From pgsql-performance-owner@postgresql.org Sun Aug 1 08:42:43 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id D0B9BD1B1B9 for ; Sun, 1 Aug 2004 08:42:41 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 81477-06 for ; Sun, 1 Aug 2004 11:42:36 +0000 (GMT) Received: from stark.xeocode.com (gsstark.mtl.istop.com [66.11.160.162]) by svr1.postgresql.org (Postfix) with ESMTP id C48A4D1B17B for ; Sun, 1 Aug 2004 08:42:31 -0300 (ADT) Received: from localhost ([127.0.0.1] helo=stark.xeocode.com) by stark.xeocode.com with smtp (Exim 3.36 #1 (Debian)) id 1BrEjZ-00082u-00; Sun, 01 Aug 2004 07:42:33 -0400 To: pgsql-performance@postgresql.org Subject: SSD Drives From: Greg Stark Organization: The Emacs Conspiracy; member since 1992 Date: 01 Aug 2004 07:42:33 -0400 Message-ID: <87r7qrnkye.fsf@stark.xeocode.com> Lines: 15 User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/1 X-Sequence-Number: 7637 To the person who was looking for a $5k midlevel SSD drive (sorry, I hit 'd' too fast): http://www.tigicorp.com/tigijet_exp_s.htm I found this via this interesting survey of SSD products: http://www.storagesearch.com/ssd-buyers-guide.html Incidentally it seems the popular Platypus SSD PCI cards are no more, Platypus appears to have gone out of business. -- greg From pgsql-performance-owner@postgresql.org Fri Aug 6 00:41:47 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id AB319D1B1E0 for ; Sun, 1 Aug 2004 16:18:03 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 22229-09 for ; Sun, 1 Aug 2004 19:18:01 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 8D761D1B1B4 for ; Sun, 1 Aug 2004 16:17:59 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i71JHwqb025590 for ; Sun, 1 Aug 2004 19:17:58 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i71JDCLm025097 for pgsql-performance@postgresql.org; Sun, 1 Aug 2004 19:13:12 GMT From: "Mischa Sandberg" X-Newsgroups: comp.databases.postgresql.performance References: <1091156393.39517b44365bc@mail.coretech.co.nz> <001f01c4763c$fcef40f0$4e00020a@develavoie> Subject: Re: my boss want to migrate to ORACLE Lines: 16 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2800.1437 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 Message-ID: Date: Sun, 01 Aug 2004 19:13:12 GMT To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.8 tagged_above=0.0 required=5.0 tests=PRIORITY_NO_NAME X-Spam-Level: X-Archive-Number: 200408/70 X-Sequence-Number: 7706 Regarding Raid5 at all, you might want to look at http://www.baarf.com ""Stephane Tessier"" wrote in message news:001f01c4763c$fcef40f0$4e00020a@develavoie... > I think with your help guys I'll do it! > > I'm working on it! > > I'll work on theses issues: > > we have space for more ram(we use 2 gigs on possibility of 3 gigs) > iowait is very high 98% --> look like postgresql wait for io access > raid5 -->raid0 if i'm right raid5 use 4 writes(parity,data, etc) for each .... From pgsql-performance-owner@postgresql.org Mon Aug 2 05:11:51 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 42F20D1B1E3 for ; Mon, 2 Aug 2004 05:11:48 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 85835-04 for ; Mon, 2 Aug 2004 08:11:47 +0000 (GMT) Received: from mailhost.ics.forth.gr (mailhost.ics.forth.gr [139.91.157.50]) by svr1.postgresql.org (Postfix) with ESMTP id 0F840D1B183 for ; Mon, 2 Aug 2004 05:11:43 -0300 (ADT) Received: from mailhost.ics.forth.gr (nemesis.ics.forth.gr [139.91.157.50]) by mailhost.ics.forth.gr (8.12.10/ICS-FORTH/V10-Server-1.0) with SMTP id i728BbF0012622 for ; Mon, 2 Aug 2004 11:11:43 +0300 (EEST) Received: (from ASSP-nospam [127.0.0.1]) by mailhost.ics.forth.gr (SAVSMTP 3.1.0.29) with SMTP id M2004080211114302082 for ; Mon, 02 Aug 2004 11:11:43 +0300 Received: from 139.91.157.52 ([139.91.157.52] helo=calliope.ics.forth.gr) by ASSP-nospam ; 2 Aug 04 08:11:43 -0000 Received: from localhost (theohari@localhost) by calliope.ics.forth.gr (8.9.3/ICS-FORTH/V8.2.2C-INTNULL) with ESMTP id LAA12638 for ; Mon, 2 Aug 2004 11:11:43 +0300 (EET DST) X-Authentication-Warning: calliope.ics.forth.gr: theohari owned process doing -bs Date: Mon, 2 Aug 2004 11:11:43 +0300 (EET DST) From: Ioannis Theoharis To: pgsql-performance@postgresql.org Subject: Page Miss Hits Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/2 X-Sequence-Number: 7638 Hi, i would like to answer if there is any way in postgres to find the page miss hits caused during a query execution. Is there something like explain analyze with the page miss hits??? From pgsql-performance-owner@postgresql.org Mon Aug 2 09:08:59 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 99ABBD1B17B for ; Mon, 2 Aug 2004 09:08:57 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 77186-07 for ; Mon, 2 Aug 2004 12:08:55 +0000 (GMT) Received: from p15110922.pureserver.info (p15110922.pureserver.info [217.160.165.141]) by svr1.postgresql.org (Postfix) with ESMTP id C5B71D1B170 for ; Mon, 2 Aug 2004 09:08:50 -0300 (ADT) Received: from localhost (localhost.localdomain [127.0.0.1]) by p15110922.pureserver.info (Postfix) with ESMTP id 271912202B8 for ; Mon, 2 Aug 2004 14:08:52 +0200 (CEST) Received: from p15110922.pureserver.info ([127.0.0.1]) by localhost (p15110922 [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 29440-09 for ; Mon, 2 Aug 2004 14:08:51 +0200 (CEST) Received: by p15110922.pureserver.info (Postfix, from userid 30) id B32852202B7; Mon, 2 Aug 2004 14:08:51 +0200 (CEST) From: mailing@impactmedia.de To: pgsql-performance@postgresql.org Subject: No index usage with "left join" MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message-Id: <20040802120851.B32852202B7@p15110922.pureserver.info> Date: Mon, 2 Aug 2004 14:08:51 +0200 (CEST) X-Virus-Scanned: by amavisd-new at impactmedia.de X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.3 tagged_above=0.0 required=5.0 tests=NO_REAL_NAME X-Spam-Level: X-Archive-Number: 200408/3 X-Sequence-Number: 7639 We have a "companies" and a "contacts" table with about 3000 records each. We run the following SQL-Command which runs about 2 MINUTES !: SELECT count(*) FROM contacts LEFT JOIN companies ON contacts.sid =3D companies.intfield01 contacts.sid (type text, b-tree index on it) companies.intfield01 (type bigint, b-tree index on it) comfire=3D> explain analyze SELECT count(*) FROM prg_contacts LEFT JOIN prg_addresses ON prg_contacts.sid=3Dprg_addresses.intfield01; NOTICE: QUERY PLAN: Aggregate (cost=3D495261.02..495261.02 rows=3D1 width=3D15) (actual time=3D40939.38..40939.38 rows=3D1 loops=3D1) -> Nested Loop (cost=3D0.00..495253.81 rows=3D2885 width=3D15) (actual time=3D0.05..40930.14 rows=3D2866 loops=3D1) -> Seq Scan on prg_contacts (cost=3D0.00..80.66 rows=3D2866 width=3D7) (actual time=3D0.01..18.10 rows=3D2866 loops=3D1) -> Seq Scan on prg_addresses (cost=3D0.00..131.51 rows=3D2751 width=3D8) (actual time=3D0.03..6.25 rows=3D2751 loops=3D2866) Total runtime: 40939.52 msec EXPLAIN Note: - We need the left join because we need all contacts even if they are not assigned to a company - We are not able to change the datatypes of the joined fields because we use a standard software (btw who cares: SuSE Open Exchange Server) - When we use a normal join (without LEFT or a where clause) the SQL runs immediately using the indexes How can I force the usage of the indexes when using "left join". Or any other SQL construct that does the same !? Can anybody please give us a hint !? Thanks in forward. Greetings Achim From pgsql-performance-owner@postgresql.org Mon Aug 2 09:18:31 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3DFA9D1B171 for ; Mon, 2 Aug 2004 09:18:27 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 82884-05 for ; Mon, 2 Aug 2004 12:18:16 +0000 (GMT) Received: from usbb-lacimss3.unisys.com (usbb-lacimss3.unisys.com [192.63.108.53]) by svr1.postgresql.org (Postfix) with ESMTP id 2FD6ED1B229 for ; Mon, 2 Aug 2004 09:18:11 -0300 (ADT) Received: from usbb-lacgw1.lac.uis.unisys.com ([129.226.160.21]unverified) by usbb-lacimss3 with InterScan Messaging Security Suite; Mon, 02 Aug 2004 08:19:44 -0400 Received: from usbb-lacgw1.lac.uis.unisys.com ([129.226.160.23]) by usbb-lacgw1.lac.uis.unisys.com with Microsoft SMTPSVC(6.0.3790.0); Mon, 2 Aug 2004 08:18:12 -0400 Received: from gbmk-eugw2.eu.uis.unisys.com ([129.221.133.27]) by usbb-lacgw1.lac.uis.unisys.com with Microsoft SMTPSVC(6.0.3790.0); Mon, 2 Aug 2004 08:18:12 -0400 Received: from nlshl-exch1.eu.uis.unisys.com ([192.39.239.20]) by gbmk-eugw2.eu.uis.unisys.com with Microsoft SMTPSVC(6.0.3790.0); Mon, 2 Aug 2004 13:18:02 +0100 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable X-MimeOLE: Produced By Microsoft Exchange V6.0.6487.1 Subject: Re: No index usage with "left join" Date: Mon, 2 Aug 2004 14:16:41 +0200 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] No index usage with "left join" Thread-Index: AcR4ieY+jtXJ+B+hTgWklGrx1B2u/QAAKG5w From: "Leeuw van der, Tim" To: , X-OriginalArrivalTime: 02 Aug 2004 12:18:02.0635 (UTC) FILETIME=[C1DA5DB0:01C4788A] X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/4 X-Sequence-Number: 7640 Cannot you do a cast in your query? Does that help with using the indexes? -----Original Message----- From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owner@postgresql.org]On Behalf Of mailing@impactmedia.de Sent: maandag 2 augustus 2004 14:09 To: pgsql-performance@postgresql.org Subject: [PERFORM] No index usage with "left join" We have a "companies" and a "contacts" table with about 3000 records each. We run the following SQL-Command which runs about 2 MINUTES !: SELECT count(*) FROM contacts LEFT JOIN companies ON contacts.sid =3D companies.intfield01 contacts.sid (type text, b-tree index on it) companies.intfield01 (type bigint, b-tree index on it) comfire=3D> explain analyze SELECT count(*) FROM prg_contacts LEFT JOIN prg_addresses ON prg_contacts.sid=3Dprg_addresses.intfield01; NOTICE: QUERY PLAN: Aggregate (cost=3D495261.02..495261.02 rows=3D1 width=3D15) (actual time=3D40939.38..40939.38 rows=3D1 loops=3D1) -> Nested Loop (cost=3D0.00..495253.81 rows=3D2885 width=3D15) (actual time=3D0.05..40930.14 rows=3D2866 loops=3D1) -> Seq Scan on prg_contacts (cost=3D0.00..80.66 rows=3D2866 width=3D7) (actual time=3D0.01..18.10 rows=3D2866 loops=3D1) -> Seq Scan on prg_addresses (cost=3D0.00..131.51 rows=3D2751 width=3D8) (actual time=3D0.03..6.25 rows=3D2751 loops=3D2866) Total runtime: 40939.52 msec EXPLAIN Note: - We need the left join because we need all contacts even if they are not assigned to a company - We are not able to change the datatypes of the joined fields because we use a standard software (btw who cares: SuSE Open Exchange Server) - When we use a normal join (without LEFT or a where clause) the SQL runs immediately using the indexes How can I force the usage of the indexes when using "left join". Or any other SQL construct that does the same !? Can anybody please give us a hint !? Thanks in forward. Greetings Achim ---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match From pgsql-performance-owner@postgresql.org Mon Aug 2 09:21:37 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 63C5CD1B229 for ; Mon, 2 Aug 2004 09:21:35 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 85207-05 for ; Mon, 2 Aug 2004 12:21:35 +0000 (GMT) Received: from obelix.askesis.nl (laudanum.demon.nl [82.161.125.16]) by svr1.postgresql.org (Postfix) with ESMTP id 5DB2AD1B183 for ; Mon, 2 Aug 2004 09:21:29 -0300 (ADT) MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Subject: What kind of performace can I expect and how to measure? X-MimeOLE: Produced By Microsoft Exchange V6.0.6487.1 content-class: urn:content-classes:message Date: Mon, 2 Aug 2004 14:21:31 +0200 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: What kind of performace can I expect and how to measure? Thread-Index: AcR4iz4OjHxaXZb5TuimN1+EbYe3iQ== From: "Joost Kraaijeveld" To: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/5 X-Sequence-Number: 7641 Hi all, My system is a PostgreSQL 7.4.1 on i686-pc-linux-gnu, compiled by GCC gcc (= GCC) 20020903 (Red Hat Linux 8.0 3.2-7). It has a Pentium III-733 Mhz with = 512 MB ram. It is connected to my workststation (dual XEON 1700 with 1 Gb R= AM) with a 100 Mb switched network. I have a table with 31 columns, all fixed size datatypes. It contains 88393= rows. Doing a "select * from table" with PGAdmin III in it's SQL window, i= t takes a total of 9206 ms query runtime an a 40638 ms data retrievel runti= me. Is this a reasonable time to get 88393 rows from the database? If not, what can I do to find the bottleneck (and eventually make it faster= )? Groeten, Joost Kraaijeveld Askesis B.V. Molukkenstraat 14 6524NB Nijmegen tel: 024-3888063 / 06-51855277 fax: 024-3608416 e-mail: J.Kraaijeveld@Askesis.nl web: www.askesis.nl=20 From pgsql-performance-owner@postgresql.org Mon Aug 2 09:34:41 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 7EC8FD1B241 for ; Mon, 2 Aug 2004 09:34:33 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 89595-05 for ; Mon, 2 Aug 2004 12:34:33 +0000 (GMT) Received: from Herge.rcsinc.local (mail.rcsonline.com [205.217.85.91]) by svr1.postgresql.org (Postfix) with ESMTP id B8F3AD1B243 for ; Mon, 2 Aug 2004 09:34:28 -0300 (ADT) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: Re: What kind of performace can I expect and how to measure? X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Date: Mon, 2 Aug 2004 08:33:34 -0400 Message-ID: <6EE64EF3AB31D5448D0007DD34EEB34101AF15@Herge.rcsinc.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] What kind of performace can I expect and how to measure? thread-index: AcR4iz4OjHxaXZb5TuimN1+EbYe3iQAAOFjQ From: "Merlin Moncure" To: "Joost Kraaijeveld" Cc: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/6 X-Sequence-Number: 7642 Joost wrote: > My system is a PostgreSQL 7.4.1 on i686-pc-linux-gnu, compiled by GCC gcc > (GCC) 20020903 (Red Hat Linux 8.0 3.2-7). It has a Pentium III-733 Mhz > with 512 MB ram. It is connected to my workststation (dual XEON 1700 with > 1 Gb RAM) with a 100 Mb switched network. >=20 > I have a table with 31 columns, all fixed size datatypes. It contains > 88393 rows. Doing a "select * from table" with PGAdmin III in it's SQL > window, it takes a total of 9206 ms query runtime an a 40638 ms data > retrievel runtime. >=20 > Is this a reasonable time to get 88393 rows from the database? >=20 > If not, what can I do to find the bottleneck (and eventually make it > faster)? The 9206 ms time is what the database actually spent gathering the data and sending it to you. This is non-negotiable unless you bump up hardware, etc, or fetch less data. This time usually scales linearly (or close to it) with the size of the dataset you fetch. The 40638 ms time is pgAdmin putting the data in the grid. This time spent here is dependant on your client and starts to get really nasty with large tables. Future versions of pgAdmin might be able to deal better with large datasets (cursor based fetch is one proposed solution). In the meantime, I would suggest using queries to refine your terms a little bit...(do you really need to view all 80k records at once?). Merlin From pgsql-performance-owner@postgresql.org Mon Aug 2 09:40:29 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 00F2DD1B171 for ; Mon, 2 Aug 2004 09:38:46 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 94813-02 for ; Mon, 2 Aug 2004 12:38:45 +0000 (GMT) Received: from tino.sinectis.com.ar (tino.sinectis.com.ar [216.244.192.232]) by svr1.postgresql.org (Postfix) with ESMTP id B35EFD1B184 for ; Mon, 2 Aug 2004 09:38:40 -0300 (ADT) Received: by tino.sinectis.com.ar (Postfix, from userid 99) id A10196C8BB; Mon, 2 Aug 2004 09:38:42 -0300 (GMT+3) Content-Type: text/plain Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 X-Mailer: Sinectis Webmail 5.6.16-1.5.1 From: G u i d o B a r o s i o To: tim.leeuwvander@nl.unisys.com, mailing@impactmedia.de, pgsql-performance@postgresql.org Subject: Re: No index usage with Reply-To: gbarosio@uolsinectis.com.ar Message-Id: <20040802123842.A10196C8BB@tino.sinectis.com.ar> Date: Mon, 2 Aug 2004 09:38:42 -0300 (GMT+3) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/7 X-Sequence-Number: 7643 TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match Greetz, Guido > Cannot you do a cast in your query? Does that help with using the indexes? > > -----Original Message----- > From: pgsql-performance-owner@postgresql.org > [mailto:pgsql-performance-owner@postgresql.org]On Behalf Of > mailing@impactmedia.de > Sent: maandag 2 augustus 2004 14:09 > To: pgsql-performance@postgresql.org > Subject: [PERFORM] No index usage with "left join" > > > We have a "companies" and a "contacts" table with about 3000 records > each. > > We run the following SQL-Command which runs about 2 MINUTES !: > > SELECT count(*) FROM contacts LEFT JOIN companies ON contacts.sid = > companies.intfield01 > > contacts.sid (type text, b-tree index on it) > companies.intfield01 (type bigint, b-tree index on it) > > comfire=> explain analyze SELECT count(*) FROM prg_contacts LEFT JOIN > prg_addresses ON prg_contacts.sid=prg_addresses.intfield01; > NOTICE: QUERY PLAN: > > Aggregate (cost=495261.02..495261.02 rows=1 width=15) (actual > time=40939.38..40939.38 rows=1 loops=1) > -> Nested Loop (cost=0.00..495253.81 rows=2885 width=15) (actual > time=0.05..40930.14 rows=2866 loops=1) > -> Seq Scan on prg_contacts (cost=0.00..80.66 rows=2866 > width=7) (actual time=0.01..18.10 rows=2866 loops=1) > -> Seq Scan on prg_addresses (cost=0.00..131.51 rows=2751 > width=8) (actual time=0.03..6.25 rows=2751 loops=2866) > Total runtime: 40939.52 msec > > EXPLAIN > > Note: > - We need the left join because we need all contacts even if they are > not assigned to a company > - We are not able to change the datatypes of the joined fields > because we use a standard software (btw who cares: SuSE Open Exchange > Server) > - When we use a normal join (without LEFT or a where clause) the SQL > runs immediately using the indexes > > How can I force the usage of the indexes when using "left join". Or > any other SQL construct that does the same !? Can anybody please give > us a hint !? > > Thanks in forward. > > Greetings > Achim > > ---------------------------(end of broadcast)--------------------------- > TIP 9: the planner will ignore your desire to choose an index scan if your > joining column's datatypes do not match > > ---------------------------(end of broadcast)--------------------------- > TIP 9: the planner will ignore your desire to choose an index scan if your > joining column's datatypes do not match From pgsql-performance-owner@postgresql.org Mon Aug 2 09:45:29 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 69B10D1B183 for ; Mon, 2 Aug 2004 09:45:27 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 94705-08 for ; Mon, 2 Aug 2004 12:45:26 +0000 (GMT) Received: from tht.net (vista.tht.net [216.126.88.2]) by svr1.postgresql.org (Postfix) with ESMTP id 7A05AD1B170 for ; Mon, 2 Aug 2004 09:45:20 -0300 (ADT) Received: from [134.22.68.4] (dyn-68-4.tor.dsl.tht.net [134.22.68.4]) by tht.net (Postfix) with ESMTP id 7E50C76A3C; Mon, 2 Aug 2004 08:45:24 -0400 (EDT) Subject: Re: No index usage with "left join" From: Rod Taylor To: mailing@impactmedia.de Cc: Postgresql Performance In-Reply-To: <20040802120851.B32852202B7@p15110922.pureserver.info> References: <20040802120851.B32852202B7@p15110922.pureserver.info> Content-Type: text/plain Message-Id: <1091450721.36221.104.camel@jester> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Mon, 02 Aug 2004 08:45:22 -0400 Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/8 X-Sequence-Number: 7644 > SELECT count(*) FROM contacts LEFT JOIN companies ON contacts.sid = > companies.intfield01 > > contacts.sid (type text, b-tree index on it) > companies.intfield01 (type bigint, b-tree index on it) > How can I force the usage of the indexes when using "left join". Or > any other SQL construct that does the same !? Can anybody please give > us a hint !? You really don't need to use indexes since you're fetching all information from both tables. Anyway, we can be fairly sure this isn't PostgreSQL 7.4 (which would likely choose a far better plan -- hash join rather than nested loop) as it won't join a bigint to a text field without a cast. Try this: set enable_nestloop = false; SELECT count(*) FROM contacts LEFT JOIN companies ON cast(contacts.sid as bigint) = companies.intfield01; set enable_nestloop = true; From pgsql-performance-owner@postgresql.org Mon Aug 2 09:47:48 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 61177D1B252 for ; Mon, 2 Aug 2004 09:47:44 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 98005-05 for ; Mon, 2 Aug 2004 12:47:42 +0000 (GMT) Received: from candle.pha.pa.us (candle.pha.pa.us [207.106.42.251]) by svr1.postgresql.org (Postfix) with ESMTP id 1E77ED1B243 for ; Mon, 2 Aug 2004 09:47:35 -0300 (ADT) Received: (from pgman@localhost) by candle.pha.pa.us (8.11.6/8.11.6) id i72ClKL21226; Mon, 2 Aug 2004 08:47:20 -0400 (EDT) From: Bruce Momjian Message-Id: <200408021247.i72ClKL21226@candle.pha.pa.us> Subject: Re: No index usage with In-Reply-To: <20040802123842.A10196C8BB@tino.sinectis.com.ar> To: gbarosio@uolsinectis.com.ar Date: Mon, 2 Aug 2004 08:47:20 -0400 (EDT) Cc: tim.leeuwvander@nl.unisys.com, mailing@impactmedia.de, pgsql-performance@postgresql.org X-Mailer: ELM [version 2.4ME+ PL108 (25)] MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/10 X-Sequence-Number: 7646 G u i d o B a r o s i o wrote: > TIP 9: the planner will ignore your desire to choose an index scan if your > joining column's datatypes do not match And this is fixed in 7.5/8.0. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 From pgsql-performance-owner@postgresql.org Mon Aug 2 09:47:35 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id A9556D1B229 for ; Mon, 2 Aug 2004 09:47:31 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 98005-04 for ; Mon, 2 Aug 2004 12:47:30 +0000 (GMT) Received: from obelix.askesis.nl (laudanum.demon.nl [82.161.125.16]) by svr1.postgresql.org (Postfix) with ESMTP id C4871D1B209 for ; Mon, 2 Aug 2004 09:47:25 -0300 (ADT) MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Subject: Re: What kind of performace can I expect and how to measure? X-MimeOLE: Produced By Microsoft Exchange V6.0.6487.1 content-class: urn:content-classes:message Date: Mon, 2 Aug 2004 14:47:29 +0200 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] What kind of performace can I expect and how to measure? Thread-Index: AcR4iz4OjHxaXZb5TuimN1+EbYe3iQAAOFjQAAB4WbA= From: "Joost Kraaijeveld" To: "Merlin Moncure" Cc: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/9 X-Sequence-Number: 7645 Hi Merlin, > The 9206 ms time is what the database actually spent=20 > gathering the data and sending it to you. This is non-negotiable unless = you bump up > hardware, etc, or fetch less data. This time usually scales linearly > (or close to it) with the size of the dataset you fetch. > > The 40638 ms time is pgAdmin putting the data in the grid. This time So it take PostgreSQL 9206 ms to get the data AND send it to the client. It= than takes PGAdmin 40638 ms to display the data? > solution). In the meantime, I would suggest using queries to refine > your terms a little bit...(do you really need to view all 80k=20 > records at once?). The application is build in Clarion, a 4 GL environment. We do not have any= influence over the query it generates and executes. Groeten, Joost Kraaijeveld Askesis B.V. Molukkenstraat 14 6524NB Nijmegen tel: 024-3888063 / 06-51855277 fax: 024-3608416 e-mail: J.Kraaijeveld@Askesis.nl web: www.askesis.nl=20 From pgsql-performance-owner@postgresql.org Mon Aug 2 11:04:27 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 50744D1B1CD for ; Mon, 2 Aug 2004 11:04:23 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 35607-05 for ; Mon, 2 Aug 2004 14:03:56 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id DE00DD1B184 for ; Mon, 2 Aug 2004 11:03:46 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.12.11/8.12.11) with ESMTP id i72E3mqW009717; Mon, 2 Aug 2004 10:03:48 -0400 (EDT) To: Rod Taylor Cc: mailing@impactmedia.de, Postgresql Performance Subject: Re: No index usage with "left join" In-reply-to: <1091450721.36221.104.camel@jester> References: <20040802120851.B32852202B7@p15110922.pureserver.info> <1091450721.36221.104.camel@jester> Comments: In-reply-to Rod Taylor message dated "Mon, 02 Aug 2004 08:45:22 -0400" Date: Mon, 02 Aug 2004 10:03:47 -0400 Message-ID: <9716.1091455427@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/11 X-Sequence-Number: 7647 Rod Taylor writes: >> How can I force the usage of the indexes when using "left join". > Anyway, we can be fairly sure this isn't PostgreSQL 7.4 (which would > likely choose a far better plan -- hash join rather than nested loop) Indeed, the lack of any join-condition line in the EXPLAIN output implies it's 7.2 or older. IIRC 7.4 is the first release that is capable of using merge or hash join with a condition more complicated than plain "Var = Var". In this case, since the two fields are of different datatypes, the planner sees something like "Var = Var::text" (ie, there's an inserted cast function). 7.2 will just say "duh, too complicated for me" and generate a nestloop. With the columns being of different datatypes, you don't even have a chance for an inner indexscan in the nestloop. In short: change the column datatypes to be the same, or update to 7.4.something. There are no other solutions. (Well, if you were really desperate you could create a set of mergejoinable "text op bigint" comparison operators, and then 7.2 would be able to cope; but I should think that updating to 7.4 would be much less work.) regards, tom lane From pgsql-performance-owner@postgresql.org Mon Aug 2 11:16:09 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 5D7E6D1B18C for ; Mon, 2 Aug 2004 11:16:06 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 39303-10 for ; Mon, 2 Aug 2004 14:16:04 +0000 (GMT) Received: from Herge.rcsinc.local (mail.rcsonline.com [205.217.85.91]) by svr1.postgresql.org (Postfix) with ESMTP id 86825D1B183 for ; Mon, 2 Aug 2004 11:15:58 -0300 (ADT) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: Re: What kind of performace can I expect and how to measure? X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Date: Mon, 2 Aug 2004 10:14:33 -0400 Message-ID: <6EE64EF3AB31D5448D0007DD34EEB34101AF16@Herge.rcsinc.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] What kind of performace can I expect and how to measure? thread-index: AcR4iz4OjHxaXZb5TuimN1+EbYe3iQAAOFjQAAB4WbAAAvTZAA== From: "Merlin Moncure" To: "Joost Kraaijeveld" Cc: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/12 X-Sequence-Number: 7648 > Hi Merlin, >=20 > > The 9206 ms time is what the database actually spent > > gathering the data and sending it to you. This is non-negotiable unless > you bump up > > hardware, etc, or fetch less data. This time usually scales linearly > > (or close to it) with the size of the dataset you fetch. > > > > The 40638 ms time is pgAdmin putting the data in the grid. This time > So it take PostgreSQL 9206 ms to get the data AND send it to the client. > It than takes PGAdmin 40638 ms to display the data? That is correct. This is not a problem with pgAdmin, or postgres, but a problem with grids. Conceptually, SQL tables are an in an unordered, infinite space and grids require an ordered, finite space. All 4GLs and data managers have this problem. The real solution is to refine your query in a meaningful way (80k rows is more than a human being can deal with in a practical sense). If you can't do that, install an arbitrary limit on the result set where performance breaks down, could be 10-100k depending on various factors. To simulate a finite, ordered, dataset, pgAdmin takes all the result data and puts it in GUI controls are not designed to hold 100k rows data...this is a design compromise to allow editing. Merlin From pgsql-performance-owner@postgresql.org Mon Aug 2 12:01:31 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 58A8FD1B19A for ; Mon, 2 Aug 2004 12:01:29 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 62647-05 for ; Mon, 2 Aug 2004 15:01:10 +0000 (GMT) Received: from corpmsx.gaiam.com (unknown [12.147.81.200]) by svr1.postgresql.org (Postfix) with ESMTP id 2F4EED1B181 for ; Mon, 2 Aug 2004 12:01:08 -0300 (ADT) X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: Re: SSD Drives Date: Mon, 2 Aug 2004 09:02:56 -0600 Message-ID: <8D36D5916571CB4489C2E4D0CAD6E89304864DF2@corpmsx.gaiam.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] SSD Drives Thread-Index: AcR3vfG/mln9LuUyT1mk7cOwjZ8gnQA4kwmQ From: To: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.3 tagged_above=0.0 required=5.0 tests=NO_REAL_NAME X-Spam-Level: X-Archive-Number: 200408/13 X-Sequence-Number: 7649 Thanks I found the same info on the tigi and like what I saw. I also spoke with a consulting firm that has used them and also says good things, but they have not tried it with postgres. I will post an analysis of performance once we have the equipment ordered and installed.=20 -----Original Message----- From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Greg Stark Sent: Sunday, August 01, 2004 5:43 AM To: pgsql-performance@postgresql.org Subject: [PERFORM] SSD Drives To the person who was looking for a $5k midlevel SSD drive (sorry, I hit 'd' too fast): http://www.tigicorp.com/tigijet_exp_s.htm I found this via this interesting survey of SSD products: http://www.storagesearch.com/ssd-buyers-guide.html Incidentally it seems the popular Platypus SSD PCI cards are no more, Platypus appears to have gone out of business. --=20 greg ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend From pgsql-performance-owner@postgresql.org Mon Aug 2 13:07:42 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 7160AD1B1CD for ; Mon, 2 Aug 2004 13:07:37 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 89067-07 for ; Mon, 2 Aug 2004 16:07:31 +0000 (GMT) Received: from mpls-qmqp-03.inet.qwest.net (mpls-qmqp-03.inet.qwest.net [63.231.195.114]) by svr1.postgresql.org (Postfix) with SMTP id 44C0ED1B248 for ; Mon, 2 Aug 2004 13:07:29 -0300 (ADT) Received: (qmail 83820 invoked by uid 0); 2 Aug 2004 15:36:06 -0000 Received: from mpls-pop-03.inet.qwest.net (63.231.195.3) by mpls-qmqp-03.inet.qwest.net with QMQP; 2 Aug 2004 15:36:06 -0000 Received: from 63-227-127-37.dnvr.qwest.net (HELO ?10.0.0.2?) (63.227.127.37) by mpls-pop-03.inet.qwest.net with SMTP; 2 Aug 2004 16:07:28 -0000 Date: Mon, 02 Aug 2004 10:08:49 -0600 Message-Id: <1091462929.27166.29.camel@localhost.localdomain> From: "Scott Marlowe" To: mailing@impactmedia.de Cc: pgsql-performance@postgresql.org Subject: Re: No index usage with "left join" In-Reply-To: <20040802120851.B32852202B7@p15110922.pureserver.info> References: <20040802120851.B32852202B7@p15110922.pureserver.info> Content-Type: text/plain Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/14 X-Sequence-Number: 7650 On Mon, 2004-08-02 at 06:08, mailing@impactmedia.de wrote: > We have a "companies" and a "contacts" table with about 3000 records > each. > > We run the following SQL-Command which runs about 2 MINUTES !: > > SELECT count(*) FROM contacts LEFT JOIN companies ON contacts.sid = > companies.intfield01 > > contacts.sid (type text, b-tree index on it) > companies.intfield01 (type bigint, b-tree index on it) > > comfire=> explain analyze SELECT count(*) FROM prg_contacts LEFT JOIN > prg_addresses ON prg_contacts.sid=prg_addresses.intfield01; > NOTICE: QUERY PLAN: > > Aggregate (cost=495261.02..495261.02 rows=1 width=15) (actual > time=40939.38..40939.38 rows=1 loops=1) > -> Nested Loop (cost=0.00..495253.81 rows=2885 width=15) (actual > time=0.05..40930.14 rows=2866 loops=1) > -> Seq Scan on prg_contacts (cost=0.00..80.66 rows=2866 > width=7) (actual time=0.01..18.10 rows=2866 loops=1) > -> Seq Scan on prg_addresses (cost=0.00..131.51 rows=2751 > width=8) (actual time=0.03..6.25 rows=2751 loops=2866) > Total runtime: 40939.52 msec > > EXPLAIN > > Note: > - We need the left join because we need all contacts even if they are > not assigned to a company > - We are not able to change the datatypes of the joined fields > because we use a standard software (btw who cares: SuSE Open Exchange > Server) > - When we use a normal join (without LEFT or a where clause) the SQL > runs immediately using the indexes > > How can I force the usage of the indexes when using "left join". Or > any other SQL construct that does the same !? Can anybody please give > us a hint !? Why in the world would the database use the index in this case? You're retrieving every single row, so it may as well hit the data store directly. By the way, unlike many other databases that can just hit the index, PostgreSQL always has to go back to the data store anyway to get the real value, so if it's gonna hit more than some small percentage of rows, it's usually a win to just seq scan it. Try restricting your query with a where clause to one or two rows and see what you get. From pgsql-performance-owner@postgresql.org Mon Aug 2 13:10:40 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 84296D1B19A for ; Mon, 2 Aug 2004 13:10:33 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 90792-05 for ; Mon, 2 Aug 2004 16:10:28 +0000 (GMT) Received: from mpls-qmqp-01.inet.qwest.net (mpls-qmqp-01.inet.qwest.net [63.231.195.112]) by svr1.postgresql.org (Postfix) with SMTP id 55D86D1B18A for ; Mon, 2 Aug 2004 13:10:26 -0300 (ADT) Received: (qmail 5671 invoked by uid 0); 2 Aug 2004 16:10:26 -0000 Received: from unknown (63.231.195.5) by mpls-qmqp-01.inet.qwest.net with QMQP; 2 Aug 2004 16:10:26 -0000 Received: from 63-227-127-37.dnvr.qwest.net (HELO ?10.0.0.2?) (63.227.127.37) by mpls-pop-05.inet.qwest.net with SMTP; 2 Aug 2004 16:10:25 -0000 Date: Mon, 02 Aug 2004 10:11:46 -0600 Message-Id: <1091463106.27166.33.camel@localhost.localdomain> From: "Scott Marlowe" To: "Joost Kraaijeveld" Cc: pgsql-performance@postgresql.org Subject: Re: What kind of performace can I expect and how to In-Reply-To: References: Content-Type: text/plain Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/15 X-Sequence-Number: 7651 On Mon, 2004-08-02 at 06:21, Joost Kraaijeveld wrote: > Hi all, > > My system is a PostgreSQL 7.4.1 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 20020903 (Red Hat Linux 8.0 3.2-7). It has a Pentium III-733 Mhz with 512 MB ram. It is connected to my workststation (dual XEON 1700 with 1 Gb RAM) with a 100 Mb switched network. > > I have a table with 31 columns, all fixed size datatypes. It contains 88393 rows. Doing a "select * from table" with PGAdmin III in it's SQL window, it takes a total of 9206 ms query runtime an a 40638 ms data retrievel runtime. This means it took the backend about 9 seconds to prepare the data, and 40 or so seconds total (including the 9 I believe) for the client to retrieve and then display it. > Is this a reasonable time to get 88393 rows from the database? Depends on your row size really. I'm certain you're not CPU bound if you've only got one hard drive. Put that data on a 20 way RAID5 array and I'm sure it would come back a little quicker. > If not, what can I do to find the bottleneck (and eventually make it faster)? The bottleneck is almost always IO to start with. First, as another drive and mirror it. Then go to RAID 1+0, then add more and more drives. Read this document about performance tuning: http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html From pgsql-performance-owner@postgresql.org Mon Aug 2 13:19:21 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id EA099D1B1F8 for ; Mon, 2 Aug 2004 13:18:13 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 95406-07 for ; Mon, 2 Aug 2004 16:18:08 +0000 (GMT) Received: from mpls-qmqp-03.inet.qwest.net (mpls-qmqp-03.inet.qwest.net [63.231.195.114]) by svr1.postgresql.org (Postfix) with SMTP id DFC33D1B1E3 for ; Mon, 2 Aug 2004 13:18:07 -0300 (ADT) Received: (qmail 3946 invoked by uid 0); 2 Aug 2004 15:46:44 -0000 Received: from mpls-pop-07.inet.qwest.net (63.231.195.7) by mpls-qmqp-03.inet.qwest.net with QMQP; 2 Aug 2004 15:46:44 -0000 Received: from 63-227-127-37.dnvr.qwest.net (HELO ?10.0.0.2?) (63.227.127.37) by mpls-pop-07.inet.qwest.net with SMTP; 2 Aug 2004 16:18:07 -0000 Date: Mon, 02 Aug 2004 10:19:27 -0600 Message-Id: <1091463567.27166.44.camel@localhost.localdomain> From: "Scott Marlowe" To: "Ioannis Theoharis" Cc: pgsql-performance@postgresql.org Subject: Re: Page Miss Hits In-Reply-To: References: Content-Type: text/plain Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/16 X-Sequence-Number: 7652 On Mon, 2004-08-02 at 02:11, Ioannis Theoharis wrote: > Hi, i would like to answer if there is any way in postgres to find the > page miss hits caused during a query execution. > > > Is there something like explain analyze with the page miss hits??? You're making a basic assumption that is (at least currently) untrue, and that is that PostgreSQL has it's own cache. It doesn't. It has a buffer that drops buffer back into the free pool when the last referencing backend concludes and shuts down. So, PostgreSQL currently relies on the kernel to cache for it. So, what you need is a tool that monitors the kernel cache usage and its hit rate. I'm not familiar with any, but I'm sure something out there likely does that. From pgsql-performance-owner@postgresql.org Mon Aug 2 13:48:50 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 2ED88D1B241 for ; Mon, 2 Aug 2004 13:48:18 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 11691-01 for ; Mon, 2 Aug 2004 16:48:13 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id F2641D1B1FD for ; Mon, 2 Aug 2004 13:48:12 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i72GmBqh020684 for ; Mon, 2 Aug 2004 16:48:12 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i72Gi78S020051 for pgsql-performance@postgresql.org; Mon, 2 Aug 2004 16:44:07 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Page Miss Hits Date: Mon, 02 Aug 2004 18:43:32 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 21 Message-ID: <410E6F34.6040300@bigfoot.com> References: <1091463567.27166.44.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: Scott Marlowe User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: <1091463567.27166.44.camel@localhost.localdomain> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/17 X-Sequence-Number: 7653 Scott Marlowe wrote: > On Mon, 2004-08-02 at 02:11, Ioannis Theoharis wrote: > >>Hi, i would like to answer if there is any way in postgres to find the >>page miss hits caused during a query execution. >> >> >>Is there something like explain analyze with the page miss hits??? > > > You're making a basic assumption that is (at least currently) untrue, > and that is that PostgreSQL has it's own cache. Are you sure of this ? What is the meaning of the ARC recently introduced then ? Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Mon Aug 2 17:54:50 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id F1AC6D1B181 for ; Mon, 2 Aug 2004 17:50:59 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 12601-05 for ; Mon, 2 Aug 2004 20:50:56 +0000 (GMT) Received: from pns.mm.eutelsat.org (pns.mm.eutelsat.org [194.214.173.227]) by svr1.postgresql.org (Postfix) with ESMTP id AE1A0D1B171 for ; Mon, 2 Aug 2004 17:50:52 -0300 (ADT) Received: from nts-03.mm.eutelsat.org (localhost [127.0.0.1]) by pns.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i72KoXd25533; Mon, 2 Aug 2004 22:50:34 +0200 Received: from [127.0.0.1] (accesspoint.mm.eutelsat.org [194.214.173.4]) by nts-03.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i72KoqZ19759; Mon, 2 Aug 2004 22:50:52 +0200 Message-ID: <410EA90C.7030707@bigfoot.com> Date: Mon, 02 Aug 2004 22:50:20 +0200 From: Gaetano Mendola User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Scott Marlowe Cc: "pgsql-performance@postgresql.org" Subject: Re: Page Miss Hits References: <1091463567.27166.44.camel@localhost.localdomain> <410E6F34.6040300@bigfoot.com> <1091468476.27166.48.camel@localhost.localdomain> In-Reply-To: <1091468476.27166.48.camel@localhost.localdomain> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/18 X-Sequence-Number: 7654 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Scott Marlowe wrote: | On Mon, 2004-08-02 at 10:43, Gaetano Mendola wrote: | |>Scott Marlowe wrote: |> |>>On Mon, 2004-08-02 at 02:11, Ioannis Theoharis wrote: |>> |>> |>>>Hi, i would like to answer if there is any way in postgres to find the |>>>page miss hits caused during a query execution. |>>> |>>> |>>>Is there something like explain analyze with the page miss hits??? |>> |>> |>>You're making a basic assumption that is (at least currently) untrue, |>>and that is that PostgreSQL has it's own cache. |> |>Are you sure of this ? What is the meaning of the ARC recently introduced |>then ? | | | Yes I am. Test it yourself, setup a couple of backends, select * from | some big tables, then, one at a time, shut down the psql clients and | when the last one closes, the shared mem goes away. Run another client, | do select * from the big table, and watch the client size grow from a | few meg to a size large enough to hold the whole table (or however much | your shared_buffers will hold.) | | While someone may make ARC and the shared buffers act like a cache some | day (can't be that hard, most of the work is done really) right now it's | not how it works. | | ARC still helps, since it makes sure the shared_buffers don't all get | flushed from the useful small datasets when a seq scan gets executed. I'm still not convinced. Why the last backend alive, have to throw away bunch of memory copied in the SHM? And again, the ARC is a replacement policy for a cache, which one ? Regards Gaetano Mendola -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (MingW32) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFBDqkL7UpzwH2SGd4RAsQFAKCWVpCXKgRfE1nc44ZmtEaIrtNaIQCgr4fd Hx2NiuRzV0UQ3Na9g/zQbzE= =XWua -----END PGP SIGNATURE----- From pgsql-performance-owner@postgresql.org Mon Aug 2 18:18:49 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 21D76D1B17B for ; Mon, 2 Aug 2004 18:18:47 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 21601-09 for ; Mon, 2 Aug 2004 21:18:43 +0000 (GMT) Received: from asdc003.abovesecurite.lan (unknown [206.162.148.235]) by svr1.postgresql.org (Postfix) with ESMTP id 2E77BD1B19A for ; Mon, 2 Aug 2004 18:18:37 -0300 (ADT) Received: from develavoie ([206.162.148.230]) by asdc003.abovesecurite.lan over TLS secured channel with Microsoft SMTPSVC(6.0.3790.0); Mon, 2 Aug 2004 17:23:45 -0400 From: "Stephane Tessier" To: "'Scott Marlowe'" Cc: , Subject: Re: my boss want to migrate to ORACLE Date: Mon, 2 Aug 2004 17:18:38 -0400 Message-ID: <004b01c478d6$47f46530$4e00020a@develavoie> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook CWS, Build 9.0.6604 (9.0.2911.0) In-Reply-To: <1091200491.27159.56.camel@localhost.localdomain> Importance: Normal x-mimeole: Produced By Microsoft MimeOLE V6.00.2800.1409 X-OriginalArrivalTime: 02 Aug 2004 21:23:45.0156 (UTC) FILETIME=[FDEA9440:01C478D6] X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/19 X-Sequence-Number: 7655 I checked and we have a 128 megs battery backed cache on the raid controller... -----Original Message----- From: Scott Marlowe [mailto:smarlowe@qwest.net] Sent: 30 juillet, 2004 11:15 To: Stephane Tessier Cc: markir@coretech.co.nz; pgsql-performance@postgresql.org Subject: Re: [PERFORM] my boss want to migrate to ORACLE On Fri, 2004-07-30 at 07:56, Stephane Tessier wrote: > I think with your help guys I'll do it! > > I'm working on it! > > I'll work on theses issues: > > we have space for more ram(we use 2 gigs on possibility of 3 gigs) > iowait is very high 98% --> look like postgresql wait for io access > raid5 -->raid0 if i'm right raid5 use 4 writes(parity,data, etc) for each > write on disk Just get battery backed cache on your RAID controller. RAID0 is way too unreliable for a production environment. One disk dies and all your data is just gone. > use more transactions (we have a lot of insert/update without transaction). > cpu look like not running very hard > > *php is not running on the same machine > *redhat enterprise 3.0 ES > *the version of postgresql is 7.3.4(using RHDB from redhat) > *pg_autovacuum running at 12 and 24 hour each day > > > > -----Original Message----- > From: pgsql-performance-owner@postgresql.org > [mailto:pgsql-performance-owner@postgresql.org]On Behalf Of > markir@coretech.co.nz > Sent: 29 juillet, 2004 23:00 > To: Stephane Tessier > Cc: pgsql-performance@postgresql.org > Subject: Re: [PERFORM] my boss want to migrate to ORACLE > > > A furthur thought or two: > > - you are *sure* that it is Postgres that is slow? (could be Php...or your > machine could be out of some resource - see next 2 points) > - is your machine running out of cpu or memory? > - is your machine seeing huge io transfers or long io waits? > - are you running Php on this machine as well as Postgres? > - what os (and what release) are you running? (guessing Linux but...) > > As an aside, they always say this but: Postgres 7.4 generally performs > better > than 7.3...so an upgrade could be worth it - *after* you have > solved/identified > the other issues. > > best wishes > > Mark > > Quoting Stephane Tessier : > > > Hi everyone, > > > > somebody can help me??????? my boss want to migrate to > > ORACLE................ > > > > we have a BIG problem of performance,it's slow.... > > we use postgres 7.3 for php security application with approximately 4 > > millions of insertion by day and 4 millions of delete and update > > and archive db with 40 millions of archived stuff... > > > > we have 10 databases for our clients and a centralized database for the > > general stuff. > > > > database specs: > > > > double XEON 2.4 on DELL PowerEdge2650 > > 2 gigs of RAM > > 5 SCSI Drive RAID 5 15rpm > > > > tasks: > > > > 4 millions of transactions by day > > 160 open connection 24 hours by day 7 days by week > > pg_autovacuum running 24/7 > > reindex on midnight > > > > ---------------------------(end of broadcast)--------------------------- > TIP 9: the planner will ignore your desire to choose an index scan if your > joining column's datatypes do not match > > > ---------------------------(end of broadcast)--------------------------- > TIP 8: explain analyze is your friend > From pgsql-performance-owner@postgresql.org Mon Aug 2 18:26:29 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id DCE92D1B171 for ; Mon, 2 Aug 2004 18:26:27 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 25503-10 for ; Mon, 2 Aug 2004 21:26:24 +0000 (GMT) Received: from tht.net (vista.tht.net [216.126.88.2]) by svr1.postgresql.org (Postfix) with ESMTP id 1AAE0D1B181 for ; Mon, 2 Aug 2004 18:26:20 -0300 (ADT) Received: from [134.22.68.4] (dyn-68-4.tor.dsl.tht.net [134.22.68.4]) by tht.net (Postfix) with ESMTP id 9E94876A22; Mon, 2 Aug 2004 17:26:21 -0400 (EDT) Subject: Re: Page Miss Hits From: Rod Taylor To: Gaetano Mendola Cc: Scott Marlowe , "pgsql-performance@postgresql.org" In-Reply-To: <410EA90C.7030707@bigfoot.com> References: <1091463567.27166.44.camel@localhost.localdomain> <410E6F34.6040300@bigfoot.com> <1091468476.27166.48.camel@localhost.localdomain> <410EA90C.7030707@bigfoot.com> Content-Type: text/plain Message-Id: <1091481975.36221.138.camel@jester> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Mon, 02 Aug 2004 17:26:16 -0400 Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/20 X-Sequence-Number: 7656 > | ARC still helps, since it makes sure the shared_buffers don't all get > | flushed from the useful small datasets when a seq scan gets executed. > > I'm still not convinced. Why the last backend alive, have to throw away > bunch of memory copied in the SHM? And again, the ARC is a replacement > policy for a cache, which one ? As you know, ARC is a recent addition. I've not seen any benchmarks demonstrating that the optimal SHARED_BUFFERS setting is different today than it was in the past. We know it's changed, but the old buffer strategy had an equally hard time with a small buffer as it did a large one. Does that mean the middle of the curve is still at 15k buffers but the extremes are handled better? Or something completely different? Please feel free to benchmark 7.5 (OSDL folks should be able to help us as well) and report back. From pgsql-performance-owner@postgresql.org Mon Aug 2 18:31:01 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 46554D1B184 for ; Mon, 2 Aug 2004 18:30:58 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 31678-04 for ; Mon, 2 Aug 2004 21:30:55 +0000 (GMT) Received: from asdc003.abovesecurite.lan (unknown [206.162.148.235]) by svr1.postgresql.org (Postfix) with ESMTP id 6E288D1B18C for ; Mon, 2 Aug 2004 18:30:51 -0300 (ADT) Received: from develavoie ([206.162.148.230]) by asdc003.abovesecurite.lan over TLS secured channel with Microsoft SMTPSVC(6.0.3790.0); Mon, 2 Aug 2004 17:35:59 -0400 From: "Stephane Tessier" To: "'James Thornton'" Cc: "'Scott Marlowe'" , , Subject: Re: my boss want to migrate to ORACLE Date: Mon, 2 Aug 2004 17:30:52 -0400 Message-ID: <004c01c478d7$fd8944f0$4e00020a@develavoie> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook CWS, Build 9.0.6604 (9.0.2911.0) In-Reply-To: <410EB2E3.6040609@jamesthornton.com> Importance: Normal x-mimeole: Produced By Microsoft MimeOLE V6.00.2800.1409 X-OriginalArrivalTime: 02 Aug 2004 21:35:59.0265 (UTC) FILETIME=[B37AB910:01C478D8] X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/22 X-Sequence-Number: 7658 oups, i changed for RAID 10(strip and mirror).... -----Original Message----- From: James Thornton [mailto:james@jamesthornton.com] Sent: 2 aout, 2004 17:32 To: Stephane Tessier Cc: 'Scott Marlowe'; markir@coretech.co.nz; pgsql-performance@postgresql.org Subject: Re: [PERFORM] my boss want to migrate to ORACLE Stephane Tessier wrote: > I checked and we have a 128 megs battery backed cache on the raid > controller... >>we have space for more ram(we use 2 gigs on possibility of 3 gigs) >>iowait is very high 98% --> look like postgresql wait for io access >>raid5 -->raid0 if i'm right raid5 use 4 writes(parity,data, etc) for each >>write on disk > > Just get battery backed cache on your RAID controller. RAID0 is way too > unreliable for a production environment. One disk dies and all your > data is just gone. I'm the one who sent the e-mail about RAID 5's 4 writes, but I suggested you look at RAID 10, not RAID 0. -- James Thornton ______________________________________________________ Internet Business Consultant, http://jamesthornton.com From pgsql-performance-owner@postgresql.org Mon Aug 2 18:28:03 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id C083DD1B171 for ; Mon, 2 Aug 2004 18:27:57 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 30869-03 for ; Mon, 2 Aug 2004 21:27:54 +0000 (GMT) Received: from roam.unifiedmind.com (unifiedmind.com [209.164.72.58]) by svr1.postgresql.org (Postfix) with SMTP id 04CEBD1B1EC for ; Mon, 2 Aug 2004 18:27:50 -0300 (ADT) Received: (qmail 12194 invoked from network); 2 Aug 2004 21:57:29 -0000 Received: from unknown (HELO jamesthornton.com) (james@24.175.14.24) by 0 with SMTP; 2 Aug 2004 21:57:29 -0000 Message-ID: <410EB2E3.6040609@jamesthornton.com> Date: Mon, 02 Aug 2004 16:32:19 -0500 From: James Thornton User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Stephane Tessier Cc: 'Scott Marlowe' , markir@coretech.co.nz, pgsql-performance@postgresql.org Subject: Re: my boss want to migrate to ORACLE References: <004b01c478d6$47f46530$4e00020a@develavoie> In-Reply-To: <004b01c478d6$47f46530$4e00020a@develavoie> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/21 X-Sequence-Number: 7657 Stephane Tessier wrote: > I checked and we have a 128 megs battery backed cache on the raid > controller... >>we have space for more ram(we use 2 gigs on possibility of 3 gigs) >>iowait is very high 98% --> look like postgresql wait for io access >>raid5 -->raid0 if i'm right raid5 use 4 writes(parity,data, etc) for each >>write on disk > > Just get battery backed cache on your RAID controller. RAID0 is way too > unreliable for a production environment. One disk dies and all your > data is just gone. I'm the one who sent the e-mail about RAID 5's 4 writes, but I suggested you look at RAID 10, not RAID 0. -- James Thornton ______________________________________________________ Internet Business Consultant, http://jamesthornton.com From pgsql-performance-owner@postgresql.org Mon Aug 2 19:18:39 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 7C210D1B21B for ; Mon, 2 Aug 2004 19:18:30 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 47969-08 for ; Mon, 2 Aug 2004 22:18:15 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id EFD96D1B16E for ; Mon, 2 Aug 2004 19:18:12 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i72MICqb070761 for ; Mon, 2 Aug 2004 22:18:12 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i72MEM1w070288 for pgsql-performance@postgresql.org; Mon, 2 Aug 2004 22:14:22 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Page Miss Hits Date: Tue, 03 Aug 2004 00:13:56 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 54 Message-ID: <410EBCA4.9000508@bigfoot.com> References: <1091463567.27166.44.camel@localhost.localdomain> <410E6F34.6040300@bigfoot.com> <1091468476.27166.48.camel@localhost.localdomain> <410EA90C.7030707@bigfoot.com> <1091481975.36221.138.camel@jester> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: Rod Taylor User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: <1091481975.36221.138.camel@jester> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/23 X-Sequence-Number: 7659 Rod Taylor wrote: >>| ARC still helps, since it makes sure the shared_buffers don't all get >>| flushed from the useful small datasets when a seq scan gets executed. >> >>I'm still not convinced. Why the last backend alive, have to throw away >>bunch of memory copied in the SHM? And again, the ARC is a replacement >>policy for a cache, which one ? > > > As you know, ARC is a recent addition. I've not seen any benchmarks > demonstrating that the optimal SHARED_BUFFERS setting is different today > than it was in the past. > > We know it's changed, but the old buffer strategy had an equally hard > time with a small buffer as it did a large one. Does that mean the > middle of the curve is still at 15k buffers but the extremes are handled > better? Or something completely different? > > Please feel free to benchmark 7.5 (OSDL folks should be able to help us > as well) and report back. I know, I know. We were discussing about the fact that postgres use a his own cache or not; and for the OP pleasure then if is possible retrieve hit and miss information from that cache. For benchmarch may be is better that you look not at the particular implementation done in postgresql but at the general improvements that the ARC replacement policy introduce. If I'm not wrong till now postgres was using an LRU, around you can find some articles like these: http://www.almaden.ibm.com/StorageSystems/autonomic_storage/ARC/rj10284.pdf http://www.almaden.ibm.com/cs/people/dmodha/arcfast.pdf where are showns the improvements. As you wrote no one did benchmarks on demostrating with the "brute force" that ARC is better but on the paper should be. Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Mon Aug 2 19:47:27 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 71C99D1B181 for ; Mon, 2 Aug 2004 19:47:20 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 60036-02 for ; Mon, 2 Aug 2004 22:47:20 +0000 (GMT) Received: from mail.coretech.co.nz (coretech.co.nz [202.36.204.41]) by svr1.postgresql.org (Postfix) with ESMTP id 155E5D1B17B for ; Mon, 2 Aug 2004 19:47:16 -0300 (ADT) Received: (qmail 30963 invoked from network); 2 Aug 2004 22:47:18 -0000 Received: from localhost (127.0.0.1) by 0 with SMTP; 2 Aug 2004 22:47:18 -0000 Received: from 203.167.203.141 ([203.167.203.141]) by mail.coretech.co.nz (Horde) with HTTP for ; Tue, 3 Aug 2004 10:47:18 +1200 Message-ID: <1091486838.923c2b71c3ae6@mail.coretech.co.nz> Date: Tue, 3 Aug 2004 10:47:18 +1200 From: markir@coretech.co.nz To: Stephane Tessier Cc: 'Scott Marlowe' , pgsql-performance@postgresql.org Subject: Re: my boss want to migrate to ORACLE References: <004b01c478d6$47f46530$4e00020a@develavoie> In-Reply-To: <004b01c478d6$47f46530$4e00020a@develavoie> MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Disposition: inline Content-Transfer-Encoding: 7bit User-Agent: Internet Messaging Program (IMP) 4.0-cvs X-Originating-IP: Withheld X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.3 tagged_above=0.0 required=5.0 tests=NO_REAL_NAME X-Spam-Level: X-Archive-Number: 200408/24 X-Sequence-Number: 7660 It may be worth pricing up expansion options e.g. 256M or more. The other path to consider is changing RAID5 -> RAID10 if your card supports it. However, I would recommend reducing that shared_buffers setting and doing your performance measurements *again* - before changing anything else. This is because you want to ensure that all your io hammering is not just because you are making the machine swap (by giving postgres too much memory as Scott mentioned)! Quoting Stephane Tessier : > I checked and we have a 128 megs battery backed cache on the raid > controller... From pgsql-performance-owner@postgresql.org Mon Aug 2 21:16:12 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id EF9FBD1B184 for ; Mon, 2 Aug 2004 21:16:08 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 84194-06 for ; Tue, 3 Aug 2004 00:16:02 +0000 (GMT) Received: from mpls-qmqp-01.inet.qwest.net (mpls-qmqp-01.inet.qwest.net [63.231.195.112]) by svr1.postgresql.org (Postfix) with SMTP id 5AEF1D1B16E for ; Mon, 2 Aug 2004 21:15:58 -0300 (ADT) Received: (qmail 27656 invoked by uid 0); 3 Aug 2004 00:16:01 -0000 Received: from unknown (63.231.195.5) by mpls-qmqp-01.inet.qwest.net with QMQP; 3 Aug 2004 00:16:01 -0000 Received: from 63-227-127-37.dnvr.qwest.net (HELO ?10.0.0.2?) (63.227.127.37) by mpls-pop-05.inet.qwest.net with SMTP; 3 Aug 2004 00:16:01 -0000 Date: Mon, 02 Aug 2004 18:17:16 -0600 Message-Id: <1091492236.27166.55.camel@localhost.localdomain> From: "Scott Marlowe" To: "Stephane Tessier" Cc: markir@coretech.co.nz, pgsql-performance@postgresql.org Subject: Re: my boss want to migrate to ORACLE In-Reply-To: <004b01c478d6$47f46530$4e00020a@develavoie> References: <004b01c478d6$47f46530$4e00020a@develavoie> Content-Type: text/plain Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/25 X-Sequence-Number: 7661 Is it set to write back or write through? Also, you may want to look at lowering the stripe size. The default on many RAID controllers is 128k, but for PostgreSQL 8k to 32k seems a good choice. But that's not near as important as the cache setting being write back. On Mon, 2004-08-02 at 15:18, Stephane Tessier wrote: > I checked and we have a 128 megs battery backed cache on the raid > controller... > > -----Original Message----- > From: Scott Marlowe [mailto:smarlowe@qwest.net] > Sent: 30 juillet, 2004 11:15 > To: Stephane Tessier > Cc: markir@coretech.co.nz; pgsql-performance@postgresql.org > Subject: Re: [PERFORM] my boss want to migrate to ORACLE > > > On Fri, 2004-07-30 at 07:56, Stephane Tessier wrote: > > I think with your help guys I'll do it! > > > > I'm working on it! > > > > I'll work on theses issues: > > > > we have space for more ram(we use 2 gigs on possibility of 3 gigs) > > iowait is very high 98% --> look like postgresql wait for io access > > raid5 -->raid0 if i'm right raid5 use 4 writes(parity,data, etc) for each > > write on disk > > Just get battery backed cache on your RAID controller. RAID0 is way too > unreliable for a production environment. One disk dies and all your > data is just gone. > > > use more transactions (we have a lot of insert/update without > transaction). > > cpu look like not running very hard > > > > *php is not running on the same machine > > *redhat enterprise 3.0 ES > > *the version of postgresql is 7.3.4(using RHDB from redhat) > > *pg_autovacuum running at 12 and 24 hour each day > > > > > > > > -----Original Message----- > > From: pgsql-performance-owner@postgresql.org > > [mailto:pgsql-performance-owner@postgresql.org]On Behalf Of > > markir@coretech.co.nz > > Sent: 29 juillet, 2004 23:00 > > To: Stephane Tessier > > Cc: pgsql-performance@postgresql.org > > Subject: Re: [PERFORM] my boss want to migrate to ORACLE > > > > > > A furthur thought or two: > > > > - you are *sure* that it is Postgres that is slow? (could be Php...or your > > machine could be out of some resource - see next 2 points) > > - is your machine running out of cpu or memory? > > - is your machine seeing huge io transfers or long io waits? > > - are you running Php on this machine as well as Postgres? > > - what os (and what release) are you running? (guessing Linux but...) > > > > As an aside, they always say this but: Postgres 7.4 generally performs > > better > > than 7.3...so an upgrade could be worth it - *after* you have > > solved/identified > > the other issues. > > > > best wishes > > > > Mark > > > > Quoting Stephane Tessier : > > > > > Hi everyone, > > > > > > somebody can help me??????? my boss want to migrate to > > > ORACLE................ > > > > > > we have a BIG problem of performance,it's slow.... > > > we use postgres 7.3 for php security application with approximately 4 > > > millions of insertion by day and 4 millions of delete and update > > > and archive db with 40 millions of archived stuff... > > > > > > we have 10 databases for our clients and a centralized database for the > > > general stuff. > > > > > > database specs: > > > > > > double XEON 2.4 on DELL PowerEdge2650 > > > 2 gigs of RAM > > > 5 SCSI Drive RAID 5 15rpm > > > > > > tasks: > > > > > > 4 millions of transactions by day > > > 160 open connection 24 hours by day 7 days by week > > > pg_autovacuum running 24/7 > > > reindex on midnight > > > > > > > > ---------------------------(end of broadcast)--------------------------- > > TIP 9: the planner will ignore your desire to choose an index scan if your > > joining column's datatypes do not match > > > > > > ---------------------------(end of broadcast)--------------------------- > > TIP 8: explain analyze is your friend > > > > From pgsql-performance-owner@postgresql.org Tue Aug 3 05:40:59 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id BCEE2D1B2BD for ; Tue, 3 Aug 2004 05:40:57 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 65355-04 for ; Tue, 3 Aug 2004 08:40:51 +0000 (GMT) Received: from mta2.rdslink.ro (mta2.rdslink.ro [193.231.236.124]) by svr1.postgresql.org (Postfix) with ESMTP id 156B3D1B2D9 for ; Tue, 3 Aug 2004 05:40:48 -0300 (ADT) Received: (qmail 22001 invoked from network); 3 Aug 2004 11:35:38 -0000 Received: from unknown (HELO mail.rdslink.ro) (193.231.236.20) by mta2.rdslink.ro with DES-CBC3-SHA encrypted SMTP; 3 Aug 2004 11:35:38 -0000 Received: (qmail 15830 invoked from network); 3 Aug 2004 08:39:58 -0000 Received: from unknown (HELO ?81.196.83.211?) (81.196.83.211) by mail.rdslink.ro with SMTP; 3 Aug 2004 08:39:58 -0000 Subject: NOT IN query takes forever From: Marius Andreiana To: pgsql-performance@postgresql.org Content-Type: text/plain Organization: Galuna S.R.L. Date: Tue, 03 Aug 2004 11:49:02 +0300 Message-Id: <1091522942.4936.5.camel@marte.biciclete.ro> Mime-Version: 1.0 X-Mailer: Evolution 1.5.9.1 (1.5.9.1-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/26 X-Sequence-Number: 7662 Hi I have 2 tables like this: CREATE TABLE query ( query_id int not null, dat varchar(64) null , sub_acc_id int null , query_ip varchar(64) null , osd_user_type varchar(64) null ) ; CREATE TABLE trans ( transaction_id varchar(64) not null , date varchar(64) null , query_id int not null , sub_acc_id int null , reg_acc_id int null ) ; CREATE UNIQUE INDEX query_query_id_idx ON query (query_id) ; CREATE INDEX trans_reg_acc_id_idx ON trans (reg_acc_id) ; CREATE INDEX trans_query_id_idx ON trans(query_id) ; osd=> select count(*) from trans osd-> ; count -------- 598809 (1 row) osd=> osd=> select count(*) from query osd-> ; count -------- 137042 (1 row) I just vacuum analyse'd the database. Trying to run this query: EXPLAIN ANALYSE select * FROM trans WHERE query_id NOT IN (select query_id FROM query) but it will remain like that forever (cancelled after 30 min). My postgresql.conf is the default: # - Memory - shared_buffers = 1000 # min 16, at least max_connections*2, 8KB each #sort_mem = 1024 # min 64, size in KB #vacuum_mem = 8192 # min 1024, size in KB Should I adjust something? Using postgresql 7.4.2, saw in release notes that IN/NOT IN queries are at least as faster than EXISTS. Thank you! -- Marius Andreiana Galuna - Solutii Linux in Romania http://www.galuna.ro From pgsql-performance-owner@postgresql.org Tue Aug 3 06:07:41 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 0DF9BD1B341 for ; Tue, 3 Aug 2004 06:07:40 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 74445-09 for ; Tue, 3 Aug 2004 09:07:31 +0000 (GMT) Received: from mx2.aftenposten.no (mx2.aftenposten.no [80.91.34.76]) by svr1.postgresql.org (Postfix) with ESMTP id 296DFD1B2A8 for ; Tue, 3 Aug 2004 06:07:28 -0300 (ADT) Received: from localhost (localhost.aftenposten.no [127.0.0.1]) by mx2.aftenposten.no (Postfix) with ESMTP id 9E4287F7F1F for ; Tue, 3 Aug 2004 11:07:28 +0200 (CEST) Received: from mx2.aftenposten.no ([127.0.0.1]) by localhost (mx2.aftenposten.no [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 87180-01-4 for ; Tue, 3 Aug 2004 11:07:28 +0200 (CEST) Received: from smtp1.aftenposten.no (unknown [80.91.34.6]) by mx2.aftenposten.no (Postfix) with ESMTP id 05A397F7EFD for ; Tue, 3 Aug 2004 11:07:28 +0200 (CEST) Received: from telecommail.inpoc.no (unverified) by smtp1.aftenposten.no (Content Technologies SMTPRS 4.3.12) with ESMTP id for ; Tue, 3 Aug 2004 11:09:48 +0200 Received: by TELECOMMAIL with Internet Mail Service (5.5.2653.19) id ; Tue, 3 Aug 2004 11:09:27 +0200 Message-ID: From: "Lending, Rune" To: "'pgsql-performance@postgresql.org'" Subject: pg_autovacuum parameters Date: Tue, 3 Aug 2004 11:09:26 +0200 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C47939.938C2AB0" X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.5 tagged_above=0.0 required=5.0 tests=HTML_40_50, HTML_MESSAGE X-Spam-Level: X-Archive-Number: 200408/27 X-Sequence-Number: 7663 This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ------_=_NextPart_001_01C47939.938C2AB0 Content-Type: text/plain Hello all. I am managing a large database with lots of transactions in different tables. The largest tables have around 5-6 millions tuples and around 50000-60000 inserts and maybe 20000 updates pr day. While the smalest tables have only a few tuples and a few updates /inserts pr day. In addition we have small tables with many updates/inserts. So what I am saying is that there is all kinds of tables and uses of tables in our database. This, I think, makes it difficult to set up pg_autovacuum. I am now running vacuum jobs on different tables in cron. What things should I consider when setting but base and threshold values in pg_autovacuum? Since the running of vacuum and analyze is relative to the table size, as it must be, I think it is difficult to cover all tables.. Are there anyone who have some thoughts around this? Regards Rune ------_=_NextPart_001_01C47939.938C2AB0 Content-Type: text/html Melding
Hello all.
 
I am managing a large database with lots of transactions in different tables.
The largest tables have around 5-6 millions tuples and around 50000-60000 inserts and maybe 20000 updates pr day.
While the smalest tables have only a few tuples and a few updates /inserts pr day. In addition we have small tables with many updates/inserts. So what I am saying is that there is all kinds of tables and uses of tables in our database.
This, I think, makes it difficult to set up pg_autovacuum. I am now running vacuum jobs on different tables in cron.
 
What things should I consider when setting but base and threshold values in pg_autovacuum? Since the running of vacuum and analyze is relative to the table size, as it must be, I think it is difficult to cover all tables..
 
Are there anyone who have some thoughts around this?
 
Regards
Rune
 
------_=_NextPart_001_01C47939.938C2AB0-- From pgsql-performance-owner@postgresql.org Tue Aug 3 09:06:14 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 0FB7DD1B275 for ; Tue, 3 Aug 2004 09:06:11 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 57831-07 for ; Tue, 3 Aug 2004 12:06:05 +0000 (GMT) Received: from Herge.rcsinc.local (mail.rcsonline.com [205.217.85.91]) by svr1.postgresql.org (Postfix) with ESMTP id B8ADFD1B1D2 for ; Tue, 3 Aug 2004 09:06:02 -0300 (ADT) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: Re: NOT IN query takes forever X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Date: Tue, 3 Aug 2004 08:05:23 -0400 Message-ID: <6EE64EF3AB31D5448D0007DD34EEB34101AF1A@Herge.rcsinc.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] NOT IN query takes forever thread-index: AcR5NyJZJe1lKR+HSKajmM2X8ntV+wAGnwaw From: "Merlin Moncure" To: "Marius Andreiana" Cc: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/28 X-Sequence-Number: 7664 > Trying to run this query: > EXPLAIN ANALYSE > select * FROM trans > WHERE query_id NOT IN (select query_id FROM query) >=20 > but it will remain like that forever (cancelled after 30 min). explain analyze actually runs the query to do timings. Just run explain and see what you come up with. More than likely there is a nestloop in there which is causing the long query time. Try bumping up shared buffers some and sort mem as much as you safely can. Merlin From pgsql-performance-owner@postgresql.org Tue Aug 3 11:09:20 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 701ABD1B2E6 for ; Tue, 3 Aug 2004 11:09:14 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 16357-05 for ; Tue, 3 Aug 2004 14:06:27 +0000 (GMT) Received: from megazone.bigpanda.com (megazone.bigpanda.com [64.147.171.210]) by svr1.postgresql.org (Postfix) with ESMTP id 7DB28D1B192 for ; Tue, 3 Aug 2004 11:03:43 -0300 (ADT) Received: by megazone.bigpanda.com (Postfix, from userid 1001) id 9D911354F2; Tue, 3 Aug 2004 07:03:31 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by megazone.bigpanda.com (Postfix) with ESMTP id 9C28E354F1; Tue, 3 Aug 2004 07:03:31 -0700 (PDT) Date: Tue, 3 Aug 2004 07:03:31 -0700 (PDT) From: Stephan Szabo To: Marius Andreiana Cc: pgsql-performance@postgresql.org Subject: Re: NOT IN query takes forever In-Reply-To: <1091522942.4936.5.camel@marte.biciclete.ro> Message-ID: <20040803065928.Y88907@megazone.bigpanda.com> References: <1091522942.4936.5.camel@marte.biciclete.ro> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=1.1 tagged_above=0.0 required=5.0 tests=NO_DNS_FOR_FROM X-Spam-Level: * X-Archive-Number: 200408/29 X-Sequence-Number: 7665 On Tue, 3 Aug 2004, Marius Andreiana wrote: > I just vacuum analyse'd the database. > > Trying to run this query: > EXPLAIN ANALYSE > select * FROM trans > WHERE query_id NOT IN (select query_id FROM query) > > but it will remain like that forever (cancelled after 30 min). > > My postgresql.conf is the default: > # - Memory - > > shared_buffers = 1000 # min 16, at least max_connections*2, > 8KB each > #sort_mem = 1024 # min 64, size in KB > #vacuum_mem = 8192 # min 1024, size in KB > > Should I adjust something? Probably sort_mem. It's probably estimating that it can't hash the result into the 1MB of sort_mem so it's probably falling back to some sort of nested execution. From pgsql-performance-owner@postgresql.org Tue Aug 3 11:26:15 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 785DED1B385 for ; Tue, 3 Aug 2004 11:26:08 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 26490-02 for ; Tue, 3 Aug 2004 14:25:42 +0000 (GMT) Received: from outbound.mailhop.org (unknown [63.208.196.171]) by svr1.postgresql.org (Postfix) with ESMTP id 5944ED1B344 for ; Tue, 3 Aug 2004 11:21:06 -0300 (ADT) Received: from ool-4350c7ad.dyn.optonline.net ([67.80.199.173] helo=[192.168.0.66]) by outbound.mailhop.org with asmtp (TLSv1:AES256-SHA:256) (Exim 4.20) id 1Bs08q-000D1f-6b; Tue, 03 Aug 2004 10:19:48 -0400 Message-ID: <410F9EF4.1070003@zeut.net> Date: Tue, 03 Aug 2004 10:19:32 -0400 From: "Matthew T. O'Connor" User-Agent: Mozilla Thunderbird 0.7 (Windows/20040616) X-Accept-Language: en-us, en MIME-Version: 1.0 To: "Lending, Rune" Cc: "'pgsql-performance@postgresql.org'" Subject: Re: pg_autovacuum parameters References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Mail-Handler: MailHop Outbound by DynDNS.org X-Originating-IP: 67.80.199.173 X-Report-Abuse-To: abuse@dyndns.org (see http://www.mailhop.org/outbound/abuse.html for abuse reporting information) X-MHO-User: zeut X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.2 tagged_above=0.0 required=5.0 tests=RCVD_IN_NJABL, RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/30 X-Sequence-Number: 7666 Lending, Rune wrote: > Hello all. > > I am managing a large database with lots of transactions in different > tables. > The largest tables have around 5-6 millions tuples and around > 50000-60000 inserts and maybe 20000 updates pr day. > While the smalest tables have only a few tuples and a few updates > /inserts pr day. In addition we have small tables with many > updates/inserts. So what I am saying is that there is all kinds of > tables and uses of tables in our database. > This, I think, makes it difficult to set up pg_autovacuum. I am now > running vacuum jobs on different tables in cron. > > What things should I consider when setting but base and threshold values > in pg_autovacuum? Since the running of vacuum and analyze is relative to > the table size, as it must be, I think it is difficult to cover all tables.. One of the biggest problems with the version of pg_autovacuum in 7.4 contrib is that you can only specify one set of thresholds, which often isn't flexible enough. That said the thresholds are based on table since since you specify both a base value and a scaling factor so pg_autovacuum -v 1000 -V 1 will vacuum a table with 100 rows every 200 updates, but will vacuum a table with 1,000,000 rows every 1,000,100 updates. > Are there anyone who have some thoughts around this? Basically, you should be able to use pg_autovacuum to do most of the vacuuming, if there are a few tables that aren't getting vacuumed often enough, then you can add a vacuum command to cron for those specific tables. Matthew From pgsql-performance-owner@postgresql.org Tue Aug 3 12:00:21 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 43C5FD1B38E for ; Tue, 3 Aug 2004 12:00:16 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 38581-06 for ; Tue, 3 Aug 2004 14:59:42 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id 647AED1B37F for ; Tue, 3 Aug 2004 11:59:22 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.12.11/8.12.11) with ESMTP id i73ExHPD023046; Tue, 3 Aug 2004 10:59:17 -0400 (EDT) To: "Merlin Moncure" Cc: "Marius Andreiana" , pgsql-performance@postgresql.org Subject: Re: NOT IN query takes forever In-reply-to: <6EE64EF3AB31D5448D0007DD34EEB34101AF1A@Herge.rcsinc.local> References: <6EE64EF3AB31D5448D0007DD34EEB34101AF1A@Herge.rcsinc.local> Comments: In-reply-to "Merlin Moncure" message dated "Tue, 03 Aug 2004 08:05:23 -0400" Date: Tue, 03 Aug 2004 10:59:17 -0400 Message-ID: <23045.1091545157@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=1.1 tagged_above=0.0 required=5.0 tests=NO_DNS_FOR_FROM X-Spam-Level: * X-Archive-Number: 200408/31 X-Sequence-Number: 7667 "Merlin Moncure" writes: > Try bumping up shared buffers some and sort mem as much as you safely > can. sort_mem is probably the issue here. The only reasonable way to do NOT IN is with a hash table, and the default setting of sort_mem is probably too small to support a 137042-element table. regards, tom lane From pgsql-performance-owner@postgresql.org Tue Aug 3 15:10:45 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 90312D1B375 for ; Tue, 3 Aug 2004 15:10:41 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 22107-02 for ; Tue, 3 Aug 2004 18:10:31 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 11EFAD1B785 for ; Tue, 3 Aug 2004 13:26:05 -0300 (ADT) Received: from news.hub.org ([200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i73GN6qb034457 for ; Tue, 3 Aug 2004 16:25:23 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i73FtfGh030622 for pgsql-performance@postgresql.org; Tue, 3 Aug 2004 15:55:41 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: pg_autovacuum parameters Date: Tue, 03 Aug 2004 17:54:44 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 49 Message-ID: <410FB544.1010403@bigfoot.com> References: <410F9EF4.1070003@zeut.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: "Matthew T. O'Connor" User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: <410F9EF4.1070003@zeut.net> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/34 X-Sequence-Number: 7670 Matthew T. O'Connor wrote: > Lending, Rune wrote: > >> Hello all. >> >> I am managing a large database with lots of transactions in different >> tables. >> The largest tables have around 5-6 millions tuples and around >> 50000-60000 inserts and maybe 20000 updates pr day. >> While the smalest tables have only a few tuples and a few updates >> /inserts pr day. In addition we have small tables with many >> updates/inserts. So what I am saying is that there is all kinds of >> tables and uses of tables in our database. >> This, I think, makes it difficult to set up pg_autovacuum. I am now >> running vacuum jobs on different tables in cron. >> >> What things should I consider when setting but base and threshold >> values in pg_autovacuum? Since the running of vacuum and analyze is >> relative to the table size, as it must be, I think it is difficult to >> cover all tables.. > > > One of the biggest problems with the version of pg_autovacuum in 7.4 > contrib is that you can only specify one set of thresholds, which often > isn't flexible enough. That said the thresholds are based on table > since since you specify both a base value and a scaling factor so > pg_autovacuum -v 1000 -V 1 will vacuum a table with 100 rows every 200 > updates, but will vacuum a table with 1,000,000 rows every 1,000,100 > updates. > >> Are there anyone who have some thoughts around this? > > > Basically, you should be able to use pg_autovacuum to do most of the > vacuuming, if there are a few tables that aren't getting vacuumed often > enough, then you can add a vacuum command to cron for those specific > tables. And in the version 7.5^H^H^H8.0 ( Tom Lane docet :-) ) I think is possible specify that thresholds per table... Regards Gateano Mendola From pgsql-performance-owner@postgresql.org Tue Aug 3 12:58:16 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id F0427D1B488 for ; Tue, 3 Aug 2004 12:58:13 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 67696-09 for ; Tue, 3 Aug 2004 15:57:58 +0000 (GMT) Received: from mta2.rdslink.ro (mta2.rdslink.ro [193.231.236.124]) by svr1.postgresql.org (Postfix) with ESMTP id 56F5AD1B541 for ; Tue, 3 Aug 2004 12:54:36 -0300 (ADT) Received: (qmail 16166 invoked from network); 3 Aug 2004 18:49:20 -0000 Received: from unknown (HELO mail.rdslink.ro) (193.231.236.20) by mta2.rdslink.ro with DES-CBC3-SHA encrypted SMTP; 3 Aug 2004 18:49:20 -0000 Received: (qmail 7674 invoked from network); 3 Aug 2004 15:53:42 -0000 Received: from unknown (HELO ?81.196.83.211?) (81.196.83.211) by mail.rdslink.ro with SMTP; 3 Aug 2004 15:53:42 -0000 Subject: Re: NOT IN query takes forever From: Marius Andreiana To: pgsql-performance@postgresql.org In-Reply-To: <6EE64EF3AB31D5448D0007DD34EEB34101AF1A@Herge.rcsinc.local> References: <6EE64EF3AB31D5448D0007DD34EEB34101AF1A@Herge.rcsinc.local> Content-Type: text/plain Organization: Galuna S.R.L. Date: Tue, 03 Aug 2004 19:02:42 +0300 Message-Id: <1091548963.6915.2.camel@marte.biciclete.ro> Mime-Version: 1.0 X-Mailer: Evolution 1.5.9.1 (1.5.9.1-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/32 X-Sequence-Number: 7668 On Tue, 2004-08-03 at 08:05 -0400, Merlin Moncure wrote: > > Trying to run this query: > > EXPLAIN ANALYSE > > select * FROM trans > > WHERE query_id NOT IN (select query_id FROM query) > > > > but it will remain like that forever (cancelled after 30 min). > > explain analyze actually runs the query to do timings. Just run explain > and see what you come up with. More than likely there is a nestloop in > there which is causing the long query time. > > Try bumping up shared buffers some and sort mem as much as you safely > can. Thank you, that did it! With shared_buffers = 3000 # min 16, at least max_connections*2, 8KB each sort_mem = 128000 # min 64, size in KB it takes <3 seconds (my hardware is not server-class). -- Marius Andreiana Galuna - Solutii Linux in Romania http://www.galuna.ro From pgsql-performance-owner@postgresql.org Tue Aug 3 14:53:36 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id B355ED1B438 for ; Tue, 3 Aug 2004 14:53:31 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 03682-10 for ; Tue, 3 Aug 2004 17:53:26 +0000 (GMT) Received: from Herge.rcsinc.local (mail.rcsonline.com [205.217.85.91]) by svr1.postgresql.org (Postfix) with ESMTP id 8820FD1B388 for ; Tue, 3 Aug 2004 13:12:45 -0300 (ADT) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: Re: NOT IN query takes forever X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Date: Tue, 3 Aug 2004 12:10:04 -0400 Message-ID: <6EE64EF3AB31D5448D0007DD34EEB34101AF1C@Herge.rcsinc.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] NOT IN query takes forever thread-index: AcR5c7RN5rOmntfzRgq6HbLmiUhx0wAACuzg From: "Merlin Moncure" To: "Marius Andreiana" Cc: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/33 X-Sequence-Number: 7669 > > Try bumping up shared buffers some and sort mem as much as you safely > > can. > Thank you, that did it! >=20 > With > shared_buffers =3D 3000 # min 16, at least max_connections*2, 8KB > each > sort_mem =3D 128000 # min 64, size in KB >=20 > it takes <3 seconds (my hardware is not server-class). Be careful...sort_mem applies to each connection and (IIRC) in some cases more than once to a connection. Of all the configuration parameters, sort_mem (IMO) is the most important and the hardest to get right. 128k (or 128MB) is awfully high unless you have a ton of memory (you don't) or you are running in single connection scenarios. Do some experimentation by lowering the value until you get a good balance between potential memory consumption and speed. Merlin From pgsql-performance-owner@postgresql.org Tue Aug 3 19:21:07 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 69492D1B4E5 for ; Tue, 3 Aug 2004 19:20:50 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 13972-06 for ; Tue, 3 Aug 2004 22:20:47 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id E361BD1CEDC for ; Tue, 3 Aug 2004 14:48:25 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i73HmOqb047824 for ; Tue, 3 Aug 2004 17:48:24 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i73HSw54045070 for pgsql-performance@postgresql.org; Tue, 3 Aug 2004 17:28:58 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: NOT IN query takes forever Date: Tue, 03 Aug 2004 19:28:27 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 48 Message-ID: <410FCB3B.5050300@bigfoot.com> References: <6EE64EF3AB31D5448D0007DD34EEB34101AF1A@Herge.rcsinc.local> <1091548963.6915.2.camel@marte.biciclete.ro> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: Marius Andreiana User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: <1091548963.6915.2.camel@marte.biciclete.ro> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/39 X-Sequence-Number: 7675 Marius Andreiana wrote: > On Tue, 2004-08-03 at 08:05 -0400, Merlin Moncure wrote: > >>>Trying to run this query: >>>EXPLAIN ANALYSE >>>select * FROM trans >>>WHERE query_id NOT IN (select query_id FROM query) >>> >>>but it will remain like that forever (cancelled after 30 min). >> >>explain analyze actually runs the query to do timings. Just run explain >>and see what you come up with. More than likely there is a nestloop in >>there which is causing the long query time. >> >>Try bumping up shared buffers some and sort mem as much as you safely >>can. > > Thank you, that did it! > > With > shared_buffers = 3000 # min 16, at least max_connections*2, 8KB each > sort_mem = 128000 # min 64, size in KB 128 MB for sort_mem is too much, consider that in this way each backend can use 128 MB for sort operations... Also shared_buffers = 3000 means 24MB that is not balanced with the 128MB needed for sort... Try to bump up 128 MB for shared_buffer ( may be you need to instruct your OS to allow that ammount of shared memory usage ) and 24MB for sort_mem. Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Tue Aug 3 15:19:46 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 24311D1B4A2 for ; Tue, 3 Aug 2004 15:19:27 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 24907-10 for ; Tue, 3 Aug 2004 18:19:26 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 71D75D1B38E for ; Tue, 3 Aug 2004 15:18:28 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i73IIRqd052782 for ; Tue, 3 Aug 2004 18:18:28 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i73I5JA5050772 for pgsql-performance@postgresql.org; Tue, 3 Aug 2004 18:05:19 GMT From: Martin Foster User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7) Gecko/20040616 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 X-Newsgroups: comp.databases.postgresql.performance Subject: Performance Bottleneck Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Lines: 36 Message-ID: Date: Tue, 03 Aug 2004 18:05:04 GMT To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/35 X-Sequence-Number: 7671 I run a Perl/CGI driven website that makes extensive use of PostgreSQL (7.4.3) for everything from user information to formatting and display of specific sections of the site. The server itself, is a dual processor AMD Opteron 1.4Ghz w/ 2GB Ram and 2 x 120GB hard drives mirrored for redundancy running under FreeBSD 5.2.1 (AMD64). Recently loads on the site have increased during peak hours to the point of showing considerable loss in performance. This can be observed when connections move from the 120 concurrent connections to PostgreSQL to roughly 175 or more. Essentially, the machine seems to struggle to keep up with continual requests and slows down respectively as resources are tied down. Code changes have been made to the scripts to essentially back off in high load working environments which have worked to an extent. However, as loads continue to increase the database itself is not taking well to the increased traffic taking place. Having taken a look at 'Tuning PostgreSQL for Performance' (http://www.varlena.com/GeneralBits/Tidbits/perf.html) using it as best I could in order to set my settings. However, even with statistics disabled and ever setting tweaked things still consider to deteriorate. Is there anything anyone can recommend in order to give the system a necessary speed boost? It would seem to me that a modest dataset of roughly a Gig combined with that type of hardware should be able to handle substantially more load then what it is. Can anyone provide me with clues as where to pursue? Would disabling 'fsync' provide more performance if I choose that information may be lost in case of a crash? If anyone needs access to logs, settings et cetera. Please ask, I simply wish to test the waters first on what is needed. Thanks! Martin Foster martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Tue Aug 3 15:25:24 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 37F4CD1B374 for ; Tue, 3 Aug 2004 15:25:22 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 27583-09 for ; Tue, 3 Aug 2004 18:25:17 +0000 (GMT) Received: from mpls-qmqp-04.inet.qwest.net (mpls-qmqp-04.inet.qwest.net [63.231.195.115]) by svr1.postgresql.org (Postfix) with SMTP id 1C7DDD1B344 for ; Tue, 3 Aug 2004 15:25:14 -0300 (ADT) Received: (qmail 6619 invoked by uid 0); 3 Aug 2004 18:25:13 -0000 Received: from mpls-pop-12.inet.qwest.net (63.231.195.12) by mpls-qmqp-04.inet.qwest.net with QMQP; 3 Aug 2004 18:25:13 -0000 Received: from 63-227-127-37.dnvr.qwest.net (HELO ?10.0.0.2?) (63.227.127.37) by mpls-pop-12.inet.qwest.net with SMTP; 3 Aug 2004 18:25:12 -0000 Date: Tue, 03 Aug 2004 12:26:28 -0600 Message-Id: <1091557588.27166.94.camel@localhost.localdomain> From: "Scott Marlowe" To: "Merlin Moncure" Cc: "Marius Andreiana" , pgsql-performance@postgresql.org Subject: Re: NOT IN query takes forever In-Reply-To: <6EE64EF3AB31D5448D0007DD34EEB34101AF1C@Herge.rcsinc.local> References: <6EE64EF3AB31D5448D0007DD34EEB34101AF1C@Herge.rcsinc.local> Content-Type: text/plain Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/36 X-Sequence-Number: 7672 On Tue, 2004-08-03 at 10:10, Merlin Moncure wrote: > > > Try bumping up shared buffers some and sort mem as much as you > safely > > > can. > > Thank you, that did it! > > > > With > > shared_buffers = 3000 # min 16, at least max_connections*2, > 8KB > > each > > sort_mem = 128000 # min 64, size in KB > > > > it takes <3 seconds (my hardware is not server-class). > > Be careful...sort_mem applies to each connection and (IIRC) in some > cases more than once to a connection. Of all the configuration > parameters, sort_mem (IMO) is the most important and the hardest to get > right. 128k (or 128MB) is awfully high unless you have a ton of memory > (you don't) or you are running in single connection scenarios. Do some > experimentation by lowering the value until you get a good balance > between potential memory consumption and speed. Minor nit, sort_mem actually applies to EACH sort individually, so a query that had to run three sorts could use 3 x sort_mem. Note that one can set sort_mem per backend connection with set sort_mem=128000 if need be so as not to use up all the memory with other backends. From pgsql-performance-owner@postgresql.org Tue Aug 3 15:39:13 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 47115D1B34A for ; Tue, 3 Aug 2004 15:35:45 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 35166-04 for ; Tue, 3 Aug 2004 18:35:41 +0000 (GMT) Received: from zigo.dhs.org (as2-4-3.an.g.bonet.se [194.236.34.191]) by svr1.postgresql.org (Postfix) with ESMTP id A8883D1B171 for ; Tue, 3 Aug 2004 15:35:36 -0300 (ADT) Received: from zigo.zigo.dhs.org (zigo.zigo.dhs.org [192.168.0.1]) by zigo.dhs.org (Postfix) with ESMTP id 2DDCD8467; Tue, 3 Aug 2004 20:35:36 +0200 (CEST) Date: Tue, 3 Aug 2004 20:35:36 +0200 (CEST) From: Dennis Bjorklund To: Martin Foster Cc: pgsql-performance@postgresql.org Subject: Re: Performance Bottleneck In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/37 X-Sequence-Number: 7673 On Tue, 3 Aug 2004, Martin Foster wrote: > to roughly 175 or more. Essentially, the machine seems to struggle > to keep up with continual requests and slows down respectively as > resources are tied down. I suggest you try to find queries that are slow and check to see if the plans are optimal for those queries. There are some logging options for logging quries that run longer then a user set limit. That can help finding the slow queries. Just doing some logging for some typical page fetches often show things that can be done better. For example, it's not uncommon to see the same information beeing pulled several times by misstake. Maybe you can also try something like connection pooling. I'm not sure how much that can give, but for small queries the connection time is usually the big part. > Would disabling 'fsync' provide more performance if I choose that > information may be lost in case of a crash? I would not do that. In most cases the performance increase is modest and the data corruption risk after a crash is much bigger so it's not worth it. If you have a lot of small inserts then it might be faster with this, but if possible it's much better to try to do more work in a transaction then before. -- /Dennis Bj�rklund From pgsql-performance-owner@postgresql.org Tue Aug 3 19:46:31 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 9ADF3D1B1CD for ; Tue, 3 Aug 2004 19:36:37 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 15352-10 for ; Tue, 3 Aug 2004 22:36:36 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 150D1D1B37D for ; Tue, 3 Aug 2004 15:49:05 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i73Imlqb057882 for ; Tue, 3 Aug 2004 18:48:57 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i73IgaH0057098 for pgsql-performance@postgresql.org; Tue, 3 Aug 2004 18:42:36 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Performance Bottleneck Date: Tue, 03 Aug 2004 20:41:23 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 50 Message-ID: <410FDC53.5080509@bigfoot.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: Martin Foster User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/40 X-Sequence-Number: 7676 Martin Foster wrote: > I run a Perl/CGI driven website that makes extensive use of PostgreSQL > (7.4.3) for everything from user information to formatting and display > of specific sections of the site. The server itself, is a dual > processor AMD Opteron 1.4Ghz w/ 2GB Ram and 2 x 120GB hard drives > mirrored for redundancy running under FreeBSD 5.2.1 (AMD64). > > Recently loads on the site have increased during peak hours to the point > of showing considerable loss in performance. This can be observed > when connections move from the 120 concurrent connections to PostgreSQL > to roughly 175 or more. Essentially, the machine seems to struggle > to keep up with continual requests and slows down respectively as > resources are tied down. > > Code changes have been made to the scripts to essentially back off in > high load working environments which have worked to an extent. However, > as loads continue to increase the database itself is not taking well to > the increased traffic taking place. > > Having taken a look at 'Tuning PostgreSQL for Performance' > (http://www.varlena.com/GeneralBits/Tidbits/perf.html) using it as best > I could in order to set my settings. However, even with statistics > disabled and ever setting tweaked things still consider to deteriorate. > > Is there anything anyone can recommend in order to give the system a > necessary speed boost? It would seem to me that a modest dataset of > roughly a Gig combined with that type of hardware should be able to > handle substantially more load then what it is. Can anyone provide me > with clues as where to pursue? Would disabling 'fsync' provide more > performance if I choose that information may be lost in case of a crash? > > If anyone needs access to logs, settings et cetera. Please ask, I > simply wish to test the waters first on what is needed. Thanks! Tell us about your tipical queries, show us your configuration file. The access are only in read only mode or do you have concurrent writers and readers ? During peak hours your processors are tied to 100% ? What say the vmstat and the iostat ? May be you are not using indexes some where, or may be yes but the planner is not using it... In two words we needs other informations in order to help you. Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Tue Aug 3 16:11:41 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id C281AD1B2E0 for ; Tue, 3 Aug 2004 16:11:36 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 41637-10 for ; Tue, 3 Aug 2004 19:06:25 +0000 (GMT) Received: from hosting.commandprompt.com (128.commandprompt.com [207.173.200.128]) by svr1.postgresql.org (Postfix) with ESMTP id 62E33D1B3CA for ; Tue, 3 Aug 2004 15:52:54 -0300 (ADT) Received: from [192.168.1.51] (dsl093-038-087.pdx1.dsl.speakeasy.net [66.93.38.87]) (authenticated) by hosting.commandprompt.com (8.11.6/8.11.6) with ESMTP id i73IqKJ18462; Tue, 3 Aug 2004 11:52:20 -0700 Message-ID: <410FDEEC.90901@commandprompt.com> Date: Tue, 03 Aug 2004 11:52:28 -0700 From: "Joshua D. Drake" Organization: Command Prompt, Inc. User-Agent: Mozilla Thunderbird 0.7.1 (X11/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Martin Foster Cc: pgsql-performance@postgresql.org Subject: Re: Performance Bottleneck References: In-Reply-To: Content-Type: multipart/mixed; boundary="------------020502030003010808060900" X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/38 X-Sequence-Number: 7674 This is a multi-part message in MIME format. --------------020502030003010808060900 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Hello, It sounds to me like you are IO bound. 2x120GB hard drives just isn't going to cut it with that many connections (as a general rule). Are you swapping ? Sincerely, Joshua D. Drake Martin Foster wrote: > I run a Perl/CGI driven website that makes extensive use of PostgreSQL > (7.4.3) for everything from user information to formatting and display > of specific sections of the site. The server itself, is a dual > processor AMD Opteron 1.4Ghz w/ 2GB Ram and 2 x 120GB hard drives > mirrored for redundancy running under FreeBSD 5.2.1 (AMD64). -- Command Prompt, Inc., home of Mammoth PostgreSQL - S/ODBC and S/JDBC Postgresql support, programming shared hosting and dedicated hosting. +1-503-667-4564 - jd@commandprompt.com - http://www.commandprompt.com Mammoth PostgreSQL Replicator. Integrated Replication for PostgreSQL --------------020502030003010808060900 Content-Type: text/x-vcard; charset=utf-8; name="jd.vcf" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="jd.vcf" begin:vcard fn:Joshua D. Drake n:Drake;Joshua D. org:Command Prompt, Inc. adr:;;PO Box 215;Cascade Locks;Oregon;97014;USA email;internet:jd@commandprompt.com title:Consultant tel;work:503-667-4564 tel;fax:503-210-0034 note:Command Prompt, Inc. is the largest and oldest US based commercial PostgreSQL support provider. We provide the only commercially viable integrated PostgreSQL replication solution, but also custom programming, and support. We authored the book Practical PostgreSQL, the procedural language plPHP, and adding trigger capability to plPerl. x-mozilla-html:FALSE url:http://www.commandprompt.com/ version:2.1 end:vcard --------------020502030003010808060900-- From pgsql-performance-owner@postgresql.org Tue Aug 3 22:31:15 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 77A98D1B199 for ; Tue, 3 Aug 2004 22:31:12 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 59932-01 for ; Wed, 4 Aug 2004 01:31:12 +0000 (GMT) Received: from houston.familyhealth.com.au (fhnet.arach.net.au [203.22.197.21]) by svr1.postgresql.org (Postfix) with ESMTP id 5D10AD1B1B4 for ; Tue, 3 Aug 2004 22:31:05 -0300 (ADT) Received: from [192.168.0.40] (work-40.internal [192.168.0.40]) by houston.familyhealth.com.au (8.12.9p1/8.12.9) with ESMTP id i741V4Ui090216; Wed, 4 Aug 2004 09:31:06 +0800 (WST) (envelope-from chriskl@familyhealth.com.au) Message-ID: <41103CC5.7030207@familyhealth.com.au> Date: Wed, 04 Aug 2004 09:32:53 +0800 From: Christopher Kings-Lynne User-Agent: Mozilla Thunderbird 0.7.2 (Windows/20040707) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Merlin Moncure Cc: Marius Andreiana , pgsql-performance@postgresql.org Subject: Re: NOT IN query takes forever References: <6EE64EF3AB31D5448D0007DD34EEB34101AF1A@Herge.rcsinc.local> In-Reply-To: <6EE64EF3AB31D5448D0007DD34EEB34101AF1A@Herge.rcsinc.local> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/41 X-Sequence-Number: 7677 > explain analyze actually runs the query to do timings. Just run explain > and see what you come up with. More than likely there is a nestloop in > there which is causing the long query time. > > Try bumping up shared buffers some and sort mem as much as you safely > can. Just use an EXISTS query I suggest. Chris From pgsql-performance-owner@postgresql.org Wed Aug 4 01:26:16 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 8ECABD1B42F for ; Wed, 4 Aug 2004 01:22:22 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 98670-04 for ; Wed, 4 Aug 2004 04:21:45 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id A4796D1B29D for ; Wed, 4 Aug 2004 01:20:46 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i744JFqb036540 for ; Wed, 4 Aug 2004 04:19:56 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i743nIYm032744 for pgsql-performance@postgresql.org; Wed, 4 Aug 2004 03:49:18 GMT From: Martin Foster User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7) Gecko/20040616 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> In-Reply-To: <410FDC53.5080509@bigfoot.com> Content-Type: multipart/mixed; boundary="------------090706020804040907080407" Lines: 570 Message-ID: Date: Wed, 04 Aug 2004 03:49:11 GMT To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=1.2 tagged_above=0.0 required=5.0 tests=LINES_OF_YELLING, LINES_OF_YELLING_2, NO_DNS_FOR_FROM X-Spam-Level: * X-Archive-Number: 200408/42 X-Sequence-Number: 7678 This is a multi-part message in MIME format. --------------090706020804040907080407 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Gaetano Mendola wrote: > Martin Foster wrote: > >> I run a Perl/CGI driven website that makes extensive use of PostgreSQL >> (7.4.3) for everything from user information to formatting and display >> of specific sections of the site. The server itself, is a dual >> processor AMD Opteron 1.4Ghz w/ 2GB Ram and 2 x 120GB hard drives >> mirrored for redundancy running under FreeBSD 5.2.1 (AMD64). >> >> Recently loads on the site have increased during peak hours to the >> point of showing considerable loss in performance. This can be >> observed when connections move from the 120 concurrent connections to >> PostgreSQL to roughly 175 or more. Essentially, the machine seems >> to struggle to keep up with continual requests and slows down >> respectively as resources are tied down. >> >> Code changes have been made to the scripts to essentially back off in >> high load working environments which have worked to an extent. >> However, as loads continue to increase the database itself is not >> taking well to the increased traffic taking place. >> >> Having taken a look at 'Tuning PostgreSQL for Performance' >> (http://www.varlena.com/GeneralBits/Tidbits/perf.html) using it as >> best I could in order to set my settings. However, even with >> statistics disabled and ever setting tweaked things still consider to >> deteriorate. >> >> Is there anything anyone can recommend in order to give the system a >> necessary speed boost? It would seem to me that a modest dataset of >> roughly a Gig combined with that type of hardware should be able to >> handle substantially more load then what it is. Can anyone provide me >> with clues as where to pursue? Would disabling 'fsync' provide more >> performance if I choose that information may be lost in case of a crash? >> >> If anyone needs access to logs, settings et cetera. Please ask, I >> simply wish to test the waters first on what is needed. Thanks! > > > Tell us about your tipical queries, show us your configuration file. > The access are only in read only mode or do you have concurrent writers > and readers ? During peak hours your processors are tied to 100% ? > What say the vmstat and the iostat ? > > May be you are not using indexes some where, or may be yes but the > planner is not using it... In two words we needs other informations > in order to help you. > > > > Regards > Gaetano Mendola > > I included all the files in attachments, which will hopefully cut down on any replied to Emails. As for things like connection pooling, the web server makes use of Apache::DBI to pool the connections for the Perl scripts being driven on that server. For the sake of being thorough, a quick 'apachectl status' was thrown in when the database was under a good load. Since it would rather slow things down to wait for the servers to really get bogged down with load averages of 20.00 and more, I opted to choose a period of time where we are a bit busier then normal. You will be able to see how the system behaves under a light load and subsequently reaching 125 or so concurrent connections. The queries themselves are simple, normally drawing information from one table with few conditions or in the most complex cases using joins on two table or sub queries. These behave very well and always have, the problem is that these queries take place in rather large amounts due to the dumb nature of the scripts themselves. Over a year ago when I was still using MySQL for the project, the statistics generated would report well over 65 queries per second under loads ranging from 130 to 160 at peak but averaged over the weeks of operation. Looking at the Apache status, one can see that it averages only roughly 2.5 requests per second giving you a slight indication as to what is taking place. A quick run of 'systat -ifstat' shows the following graph: /0 /1 /2 /3 /4 /5 /6 /7 /8 /9 /10 Load Average >>>>>>>>>>> Interface Traffic Peak Total lo0 in 0.000 KB/s 0.000 KB/s 37.690 GB out 0.000 KB/s 0.000 KB/s 37.690 GB em0 in 34.638 KB/s 41.986 KB/s 28.998 GB out 70.777 KB/s 70.777 KB/s 39.553 GB Em0 is a full duplexed 100Mbs connection to an internal switch that supports the servers directly. Load on the loopback was cut down considerably once I stopped using pg_autovaccum since its performance benefits under low load were buried under the hindrance it caused when traffic was high. I am sure that there are some places that could benefit from some optimization. Especially in the case of indexes, however as a whole the problem seems to be related more to the massive onslaught of queries then it does anything else. Also note that some of these scripts run for longer durations even if they are web based. Some run as long as 30 minutes, making queries to the database from periods of wait from five seconds to twenty-five seconds. Under high duress the timeouts should back out, based on the time needed for the query to respond, normally averaging 0.008 seconds. Does this help at all, or is more detail needed on the matter? Martin Foster martin@ethereal-realms.org --------------090706020804040907080407 Content-Type: text/plain; name="postgresql.conf" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="postgresql.conf" # ----------------------------- # PostgreSQL configuration file # ----------------------------- # # This file consists of lines of the form: # # name = value # # (The '=' is optional.) White space may be used. Comments are introduced # with '#' anywhere on a line. The complete list of option names and # allowed values can be found in the PostgreSQL documentation. The # commented-out settings shown in this file represent the default values. # # Any option can also be given as a command line switch to the # postmaster, e.g. 'postmaster -c log_connections=on'. Some options # can be changed at run-time with the 'SET' SQL command. # # This file is read on postmaster startup and when the postmaster # receives a SIGHUP. If you edit the file on a running system, you have # to SIGHUP the postmaster for the changes to take effect, or use # "pg_ctl reload". #--------------------------------------------------------------------------- # CONNECTIONS AND AUTHENTICATION #--------------------------------------------------------------------------- # - Connection Settings - tcpip_socket = true ssl = false max_connections = 512 superuser_reserved_connections = 2 rendezvous_name='io' port = 5432 #unix_socket_directory = '/var/postgres' #unix_socket_group = 'postgres' #unix_socket_permissions = 0777 # octal # - Security & Authentication - authentication_timeout = 20 # 1-600, in seconds password_encryption = true db_user_namespace = false #--------------------------------------------------------------------------- # RESOURCE USAGE (except WAL) #--------------------------------------------------------------------------- # - Memory - shared_buffers = 8192 # min 16, at least max_connections*2, 8KB each sort_mem = 2048 # min 64, size in KB vacuum_mem = 65536 # min 1024, size in KB # - Free Space Map - #max_fsm_pages = 20000 # min max_fsm_relations*16, 6 bytes each #max_fsm_relations = 1000 # min 100, ~50 bytes each # - Kernel Resource Usage - #max_files_per_process = 1000 # min 25 #preload_libraries = '' #--------------------------------------------------------------------------- # WRITE AHEAD LOG #--------------------------------------------------------------------------- # - Settings - fsync = true # turns forced synchronization on or off wal_sync_method = fsync # the default varies across platforms: # fsync, fdatasync, open_sync, or open_datasync wal_buffers = 128 # min 4, 8KB each # - Checkpoints - checkpoint_segments = 24 # in logfile segments, min 1, 16MB each checkpoint_timeout = 300 # range 30-3600, in seconds checkpoint_warning = 30 # 0 is off, in seconds commit_delay = 15000 # range 0-100000, in microseconds commit_siblings = 64 # range 1-1000 #--------------------------------------------------------------------------- # QUERY TUNING #--------------------------------------------------------------------------- # - Planner Method Enabling - enable_hashagg = true enable_hashjoin = true enable_indexscan = true enable_mergejoin = true enable_nestloop = true enable_seqscan = true enable_sort = true enable_tidscan = true # - Planner Cost Constants - effective_cache_size = 16000 # typically 8KB each random_page_cost = 2 # units are one sequential page fetch cost cpu_tuple_cost = 0.01 # (same) cpu_index_tuple_cost = 0.001 # (same) cpu_operator_cost = 0.0025 # (same) # - Genetic Query Optimizer - geqo = false geqo_threshold = 11 geqo_effort = 1 geqo_generations = 0 geqo_pool_size = 0 # default based on tables in statement, # range 128-1024 geqo_selection_bias = 2.0 # range 1.5-2.0 # - Other Planner Options - default_statistics_target = 100 # range 1-1000 from_collapse_limit = 8 join_collapse_limit = 8 # 1 disables collapsing of explicit JOINs #--------------------------------------------------------------------------- # ERROR REPORTING AND LOGGING #--------------------------------------------------------------------------- # - Syslog - #syslog = 2 # range 0-2; 0=stdout; 1=both; 2=syslog #syslog_facility = 'LOCAL0' #syslog_ident = 'postgres' # - When to Log - client_min_messages = notice # Values, in order of decreasing detail: # debug5, debug4, debug3, debug2, debug1, # log, info, notice, warning, error log_min_messages = info # Values, in order of decreasing detail: # debug5, debug4, debug3, debug2, debug1, # info, notice, warning, error, log, fatal, # panic log_error_verbosity = default # terse, default, or verbose messages log_min_error_statement = panic # Values in order of increasing severity: # debug5, debug4, debug3, debug2, debug1, # info, notice, warning, error, panic(off) log_min_duration_statement = -1 # Log all statements whose # execution time exceeds the value, in # milliseconds. Zero prints all queries. # Minus-one disables. silent_mode = false # DO NOT USE without Syslog! # - What to Log - #debug_print_parse = false #debug_print_rewritten = false #debug_print_plan = false #debug_pretty_print = false #log_connections = false #log_duration = false #log_pid = false #log_statement = false #log_timestamp = false #log_hostname = false #log_source_port = false #--------------------------------------------------------------------------- # RUNTIME STATISTICS #--------------------------------------------------------------------------- # - Statistics Monitoring - log_parser_stats = false log_planner_stats = false log_executor_stats = false log_statement_stats = false # - Query/Index Statistics Collector - stats_start_collector = false stats_command_string = false stats_block_level = false stats_row_level = false stats_reset_on_server_start = true #--------------------------------------------------------------------------- # CLIENT CONNECTION DEFAULTS #--------------------------------------------------------------------------- # - Statement Behavior - search_path = '$user,public' # schema names check_function_bodies = true default_transaction_isolation = 'read committed' default_transaction_read_only = false statement_timeout = 25000 # 0 is disabled, in milliseconds # - Locale and Formatting - datestyle = 'iso, us' #timezone = unknown # actually, defaults to TZ environment setting #australian_timezones = false #extra_float_digits = 0 # min -15, max 2 #client_encoding = sql_ascii # actually, defaults to database encoding # These settings are initialized by initdb -- they may be changed lc_messages = 'C' # locale for system error message strings lc_monetary = 'C' # locale for monetary formatting lc_numeric = 'C' # locale for number formatting lc_time = 'C' # locale for time formatting # - Other Defaults - explain_pretty_print = true #dynamic_library_path = '$libdir' #max_expr_depth = 10000 # min 10 #--------------------------------------------------------------------------- # LOCK MANAGEMENT #--------------------------------------------------------------------------- deadlock_timeout = 5000 # in milliseconds #max_locks_per_transaction = 64 # min 10, ~260*max_connections bytes each #--------------------------------------------------------------------------- # VERSION/PLATFORM COMPATIBILITY #--------------------------------------------------------------------------- # - Previous Postgres Versions - #add_missing_from = true #regex_flavor = advanced # advanced, extended, or basic #sql_inheritance = true # - Other Platforms & Clients - #transform_null_equals = false --------------090706020804040907080407 Content-Type: text/plain; name="apache_load.txt" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="apache_load.txt" martin@elara ~$ apachectl status Apache Server Status for www.ethereal-realms.org Server Version: Apache/1.3.29 (Unix) mod_perl/1.27 mod_gzip/1.3.26.1a mod_ssl/2.8.16 OpenSSL/0.9.7c Server Built: May 24 2004 00:32:11 _________________________________________________________________ Current Time: Tuesday, 03-Aug-2004 21:34:37 MDT Restart Time: Tuesday, 03-Aug-2004 03:54:21 MDT Parent Server Generation: 0 Server uptime: 17 hours 40 minutes 16 seconds Total accesses: 168852 - Total Traffic: 406.0 MB CPU Usage: u283.96 s41.27 cu92.51 cs13.68 - .678% CPU load 2.65 requests/sec - 6.5 kB/second - 2521 B/request 127 requests currently being processed, 59 idle servers W_WWWW_WW.WWKKWK__W._WW_.WK._KK._..K.WW__WK_WW_WWWK_.__WWW_W.WWW __..__W._W__WWWWWW._WKWW_W_KKW_WWW___K_.WKWW__KWWWWW_WWWWKKKWW.W __.WK_WW.W_W_WWWW_KWWWWW_KW.WW.W__W_W___W___WWWKW__W_W._.WWW.WWK W___WKKW.K_W.W...KW....WW_...................................... ................................................................ ................................................................ ................................................................ ................................................................ ................................................................ ................................................................ ................................................................ ................................................................ ................................................................ ................................................................ ................................................................ ................................................................ Scoreboard Key: "_" Waiting for Connection, "S" Starting up, "R" Reading Request, "W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup, "L" Logging, "G" Gracefully finishing, "." Open slot with no current process --------------090706020804040907080407 Content-Type: text/plain; name="pg_load.txt" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="pg_load.txt" martin@io ~$ vmstat procs memory page disks faults cpu r b w avm fre flt re pi po fr sr ad4 ad6 in sy cs us sy id 0 0 0 498532 122848 3306 0 0 0 740 0 0 0 788 0 1675 16 21 63 martin@io ~$ pstat -s Device 1K-blocks Used Avail Capacity /dev/ar0s1b 4194304 24 4194280 0% martin@io ~$ iostat tty ad4 ad6 ar0 cpu tin tout KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s us ni sy in id 0 17 0.50 0 0.00 0.50 0 0.00 20.28 23 0.45 16 0 20 1 63 martin@io ~# ps -U postgres | wc -l 127 martin@io ~$ ps -uax USER PID %CPU %MEM VSZ RSS TT STAT STARTED TIME COMMAND postgres 32084 0.0 0.2 91616 3764 p0- R Mon12PM 4:08.99 /usr/local/bin/postmaster -D /var/postgres (postgres) postgres 80333 0.0 2.1 94620 44372 ?? S 8:57PM 0:01.00 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 80599 0.0 2.1 94652 44780 ?? S 8:59PM 0:00.97 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 80616 0.0 2.4 94424 50396 ?? S 8:59PM 0:00.89 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 80715 0.0 2.2 94444 46804 ?? S 9:00PM 0:00.68 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 80788 0.0 2.1 94424 43944 ?? S 9:00PM 0:00.93 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 80811 0.0 2.1 94424 43884 ?? S 9:00PM 0:00.94 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 80902 0.0 2.1 94424 43380 ?? S 9:01PM 0:00.76 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 80949 0.0 2.2 94424 45248 ?? S 9:01PM 0:00.67 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 81020 0.0 2.1 94424 42924 ?? S 9:02PM 0:00.74 postmaster: ethereal ethereal 192.168.1.6 idle in trans martin@io ~# date Tue Aug 3 21:28:53 MDT 2004 martin@io ~$ systat -vmstat 1 users Load 4.15 3.76 3.54 Aug 3 21:30 Mem:KB REAL VIRTUAL VN PAGER SWAP PAGER Tot Share Tot Share Free in out in out Act 293708 4120 482092 6736 132204 count All 1910640 5224 2462084 17060 pages Interrupts Proc:r p d s w Csw Trp Sys Int Sof Flt 212 cow 728 total 5 139 215023802 3112 1078 58023548 397288 wire 100 0: clk 295304 act 6: fdc0 59.6%Sys 0.9%Intr 38.9%User 0.0%Nice 0.6%Idl 1151936 inact 128 8: rtc | | | | | | | | | | 92748 cache 53 10: bge ==============================>>>>>>>>>>>>>>>>>> 39456 free 447 11: em0 daefr 14: ata Namei Name-cache Dir-cache 1345 prcfr Calls hits % hits % react 2761 2761 100 pdwake 1111 zfod pdpgs Disks ad4 ad6 ar0 fd0 1059 ofod intrn KB/t 0.00 0.00 16.00 0.00 95 %slo-z 204096 buf tps 0 0 35 0 1587 tfree 591 dirtybuf MB/s 0.00 0.00 0.54 0.00 120525 desiredvnodes % busy 0 0 5 0 30131 numvnodes 22695 freevnodes --------------090706020804040907080407 Content-Type: text/plain; name="pg_norm.txt" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="pg_norm.txt" martin@io ~$ vmstat procs memory page disks faults cpu r b w avm fre flt re pi po fr sr ad4 ad6 in sy cs us sy id 0 0 0 317216 128932 3121 0 0 0 736 0 0 0 789 0 1682 16 21 63 martin@io ~$ pstat -s Device 1K-blocks Used Avail Capacity /dev/ar0s1b 4194304 24 4194280 0% martin@io ~$ iostat tty ad4 ad6 ar0 cpu tin tout KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s us ni sy in id 0 17 0.50 0 0.00 0.50 0 0.00 20.32 23 0.45 16 0 20 1 63 martin@io ~$ ps -U postgres | wc -l 72 martin@io ~$ ps -uax USER PID %CPU %MEM VSZ RSS TT STAT STARTED TIME COMMAND postgres 32084 0.0 0.2 91616 3764 p0- S Mon12PM 3:17.42 /usr/local/bin/postmaster -D /var/postgres (postgres) postgres 51100 0.0 1.7 94412 35828 ?? S 3:36PM 0:01.02 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 51134 0.0 1.8 94620 37060 ?? S 3:36PM 0:01.04 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 51147 0.0 1.8 94620 36980 ?? S 3:37PM 0:00.66 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 51240 0.0 1.8 94412 37156 ?? S 3:38PM 0:00.62 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 51276 0.0 0.7 94412 15180 ?? S 3:38PM 0:00.41 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 51277 0.0 1.9 94492 40776 ?? S 3:38PM 0:00.57 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 51287 0.0 1.8 94620 37228 ?? S 3:38PM 0:00.63 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 51368 0.0 1.7 94412 35348 ?? S 3:40PM 0:00.55 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 51493 0.0 1.7 94412 35920 ?? S 3:42PM 0:00.49 postmaster: ethereal ethereal 192.168.1.6 idle in trans postgres 51495 0.0 1.7 94412 36192 ?? S 3:42PM 0:00.89 postmaster: ethereal ethereal 192.168.1.6 idle in trans martin@io ~$ date Tue Aug 3 16:09:06 MDT 2004 martin@io ~$ systat -vmstat 1 users Load 0.53 0.54 0.47 Aug 3 16:14 Mem:KB REAL VIRTUAL VN PAGER SWAP PAGER Tot Share Tot Share Free in out in out Act 205172 4312 326472 6736 120128 count All 1909516 4944 2215992 11896 pages Interrupts Proc:r p d s w Csw Trp Sys Int Sof Flt 197 cow 642 total 96 177814901 2186 947 20014746 386844 wire 100 0: clk 206544 act 6: fdc0 28.8%Sys 0.5%Intr 26.8%User 0.0%Nice 43.9%Idl 1263216 inact 128 8: rtc | | | | | | | | | | 69644 cache 55 10: bge ==============+>>>>>>>>>>>>> 50484 free 359 11: em0 daefr 14: ata Namei Name-cache Dir-cache 1235 prcfr Calls hits % hits % react 1709 1709 100 pdwake 1000 zfod pdpgs Disks ad4 ad6 ar0 fd0 938 ofod intrn KB/t 0.00 0.00 16.00 0.00 93 %slo-z 204096 buf tps 0 0 31 0 1482 tfree 56 dirtybuf MB/s 0.00 0.00 0.49 0.00 120525 desiredvnodes % busy 0 0 2 0 30131 numvnodes 7645 freevnodes --------------090706020804040907080407-- From pgsql-general-owner@postgresql.org Wed Aug 4 02:36:13 2004 X-Original-To: pgsql-general-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 2FD77D1B17A for ; Wed, 4 Aug 2004 02:35:22 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 14425-04 for ; Wed, 4 Aug 2004 05:34:23 +0000 (GMT) Received: from mta2.rdslink.ro (mta2.rdslink.ro [193.231.236.124]) by svr1.postgresql.org (Postfix) with ESMTP id 60B04D1B1B4 for ; Wed, 4 Aug 2004 02:32:48 -0300 (ADT) Received: (qmail 10695 invoked from network); 4 Aug 2004 08:27:22 -0000 Received: from unknown (HELO mail.rdslink.ro) (193.231.236.20) by mta2.rdslink.ro with DES-CBC3-SHA encrypted SMTP; 4 Aug 2004 08:27:22 -0000 Received: (qmail 23450 invoked from network); 4 Aug 2004 05:31:44 -0000 Received: from unknown (HELO ?81.196.83.211?) (81.196.83.211) by mail.rdslink.ro with SMTP; 4 Aug 2004 05:31:44 -0000 Subject: Re: [PERFORM] NOT IN query takes forever From: Marius Andreiana To: pgsql-general In-Reply-To: <410FCB3B.5050300@bigfoot.com> References: <6EE64EF3AB31D5448D0007DD34EEB34101AF1A@Herge.rcsinc.local> <1091548963.6915.2.camel@marte.biciclete.ro> <410FCB3B.5050300@bigfoot.com> Content-Type: text/plain Organization: Galuna S.R.L. Date: Wed, 04 Aug 2004 08:40:52 +0300 Message-Id: <1091598052.2647.7.camel@marte.biciclete.ro> Mime-Version: 1.0 X-Mailer: Evolution 1.5.9.1 (1.5.9.1-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=1.1 tagged_above=0.0 required=5.0 tests=NO_DNS_FOR_FROM X-Spam-Level: * X-Archive-Number: 200408/73 X-Sequence-Number: 63628 On Tue, 2004-08-03 at 19:28 +0200, Gaetano Mendola wrote: > > With > > shared_buffers = 3000 # min 16, at least max_connections*2, 8KB each > > sort_mem = 128000 # min 64, size in KB > > 128 MB for sort_mem is too much, consider that in this way each backend can > use 128 MB for sort operations... > Also shared_buffers = 3000 means 24MB that is not balanced with the 128MB > needed for sort... > Try to bump up 128 MB for shared_buffer ( may be you need to instruct your > OS to allow that ammount of shared memory usage ) and 24MB for sort_mem. Thanks for the advice. I increased shmmax to allow shared_buffers to be 128mb and set sort_mem to 24mb. -- Marius Andreiana Galuna - Solutii Linux in Romania http://www.galuna.ro From pgsql-performance-owner@postgresql.org Wed Aug 4 03:39:59 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 8BEEFD1B20D for ; Wed, 4 Aug 2004 03:39:57 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 32670-01 for ; Wed, 4 Aug 2004 06:39:59 +0000 (GMT) Received: from boutiquenumerique.com (gailleton-2-82-67-9-10.fbx.proxad.net [82.67.9.10]) by svr1.postgresql.org (Postfix) with ESMTP id 88994D1B1B6 for ; Wed, 4 Aug 2004 03:39:50 -0300 (ADT) Received: (qmail 23408 invoked from network); 4 Aug 2004 08:39:57 +0200 Received: from unknown (HELO musicbox) (192.168.0.2) by gailleton-2-82-67-9-10.fbx.proxad.net with SMTP; 4 Aug 2004 08:39:57 +0200 Date: Wed, 04 Aug 2004 08:40:41 +0200 To: pgsql-performance@postgresql.org Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> From: =?iso-8859-15?Q?Pierre-Fr=E9d=E9ric_Caillaud?= Organization: =?iso-8859-15?Q?La_Boutique_Num=E9rique?= Content-Type: text/plain; format=flowed; delsp=yes; charset=iso-8859-15 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID: In-Reply-To: User-Agent: Opera M2/7.50 (Linux, build 673) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/43 X-Sequence-Number: 7679 > The queries themselves are simple, normally drawing information from one > table with few conditions or in the most complex cases using joins on > two table or sub queries. These behave very well and always have, the > problem is that these queries take place in rather large amounts due to > the dumb nature of the scripts themselves. Hum, maybe this "dumb" thing is where to look at ? I'm no expert, but I have had the same situation with a very dump PHP application, namely osCommerce, which averaged about 140 (!!!!!) queries on a page ! I added some traces to queries, and some logging, only to see that the stupid programmers did something like (pseudo code): for id in id_list: select stuff from database where id=id Geee... I replaced it by : select stuff from database where id in (id_list) And this saved about 20 requests... The code was peppered by queries like that. In the end it went from 140 queries to about 20, which is still way too much IMHO, but I couldn't go lower without an extensive rewrite. If you have a script making many selects, it's worth grouping them, even using stored procedures. For instance using the classical "tree in a table" to store a tree of product categories : create table categories ( id serial primary key, parent_id references categories(id), etc ); You basically have these choices in order to display the tree : - select for parent_id=0 (root) - for each element, select its children - and so on OR - make a stored procedure which does that. At least 3x faster and a lot less CPU overhead. OR (if you have say 50 rows in the table which was my case) - select the entire table and build your tree in the script It was a little bit faster than the stored procedure. Could you give an example of your dumb scripts ? It's good to optimize a database, but it's even better to remove useless queries... From pgsql-general-owner@postgresql.org Wed Aug 4 09:00:53 2004 X-Original-To: pgsql-general-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 07F78D1B34A for ; Wed, 4 Aug 2004 09:00:51 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 12765-06 for ; Wed, 4 Aug 2004 12:00:52 +0000 (GMT) Received: from thor.netera.se (thor.netera.se [62.13.47.20]) by svr1.postgresql.org (Postfix) with ESMTP id 0BC2CD1B257 for ; Wed, 4 Aug 2004 09:00:42 -0300 (ADT) Received: from [127.0.0.1] (unknown [213.212.22.34]) by thor.netera.se (Postfix) with ESMTP id 6895E13AC050 for ; Wed, 4 Aug 2004 14:00:49 +0200 (CEST) Message-ID: <4110CFE7.9000202@relevanttraffic.se> Date: Wed, 04 Aug 2004 14:00:39 +0200 From: Ulrich Wisser Organization: Relevant Traffic AB User-Agent: Mozilla Thunderbird 0.7.2 (Windows/20040707) X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-general@postgresql.org Subject: How to know which queries are to be optimised? Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/77 X-Sequence-Number: 63632 Hello, my web application grows slower and slower over time. After some profiling I came to the conclusion that my SQL queries are the biggest time spenders (25 seconds). Obviously I need to optimise my queries and maybe introduce some new indexes. The problem is, that my application uses dynamic queries. I therefor can not determine what are the most common queries. I have used the postgresql logging ption before. Is there a tool to analyze the logfile for the most common and/or most time consuming queries? TIA Ulrich From pgsql-general-owner@postgresql.org Wed Aug 4 09:43:48 2004 X-Original-To: pgsql-general-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 10DA0D1B1DF; Wed, 4 Aug 2004 09:43:44 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 23074-10; Wed, 4 Aug 2004 12:43:48 +0000 (GMT) Received: from cadillac.meteo.fr (cadillac.meteo.fr [137.129.1.4]) by svr1.postgresql.org (Postfix) with ESMTP id 246DFD1B199; Wed, 4 Aug 2004 09:43:37 -0300 (ADT) Received: from mu.meteo.fr (localhost.meteo.fr [127.0.0.1]) by cadillac.meteo.fr (8.9.3 (PHNE_28760_binary)/8.9.3) with ESMTP id MAA07445; Wed, 4 Aug 2004 12:43:45 GMT Received: from mu.meteo.fr (mu.meteo.fr [137.129.6.129]) by mu.meteo.fr (8.11.7p1+Sun/8.11.7) with SMTP id i74CihO19344; Wed, 4 Aug 2004 12:44:43 GMT Message-Id: <200408041244.i74CihO19344@mu.meteo.fr> Date: Wed, 4 Aug 2004 12:44:43 +0000 (GMT) From: Valerie Schneider DSI/DEV Reply-To: Valerie Schneider DSI/DEV Subject: Tuning queries on large database To: pgsql-performance@postgresql.org, pgsql-general@postgresql.org Cc: Valerie.Schneider@meteo.fr MIME-Version: 1.0 Content-Type: TEXT/plain; charset=us-ascii Content-MD5: 0bPv2QX/0e63cdvamEjQDA== X-Mailer: dtmail 1.3.0 @(#)CDE Version 1.4.6_06 SunOS 5.8 sun4u sparc X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/80 X-Sequence-Number: 63635 Hi, I have some problem of performance on a PG database, and I don't know how to improve. I Have two questions : one about the storage of data, one about tuning queries. If possible ! My job is to compare Oracle and Postgres. All our operational databases have been running under Oracle for about fifteen years. Now I try to replace Oracle by Postgres. I have a test platform under linux (Dell server, 4 Gb RAM, bi-processor, Linux Red Hat 9 (2.4.20-31.9)) with 2 databases, 1 with Oracle (V8i or V9i it's quite the same), 1 with PG (7.4.2). Both databases have the same structure, same content, about 100 Gb each. I developped some benches, representative of our use of databases. My problem is that I have tables (relations) with more than 100 millions rows, and each row has about 160 fields and an average size 256 bytes. For Oracle I have a SGA size of 500 Mb. For PG I have a postgresql.conf as : max_connections = 1500 shared_buffers = 30000 sort_mem = 50000 effective_cache_size = 200000 and default value for other parameters. I have a table named "data" which looks like this : bench=> \d data Table "public.data" Column | Type | Modifiers ------------+-----------------------------+----------- num_poste | numeric(9,0) | not null dat | timestamp without time zone | not null datrecu | timestamp without time zone | not null rr1 | numeric(5,1) | qrr1 | numeric(2,0) | ... ... all numeric fields ... Indexes: "pk_data" primary key, btree (num_poste, dat) "i_data_dat" btree (dat) It contains 1000 different values of "num_poste" and for each one 125000 different values of "dat" (1 row per hour, 15 years). I run a vacuum analyze of the table. bench=> select * from tailledb ; schema | relfilenode | table | index | reltuples | size --------+-------------+------------------+------------+-------------+---------- public | 125615917 | data | | 1.25113e+08 | 72312040 public | 251139049 | data | i_data_dat | 1.25113e+08 | 2744400 public | 250870177 | data | pk_data | 1.25113e+08 | 4395480 My first remark is that the table takes a lot of place on disk, about 70 Gb, instead of 35 Gb with oracle. 125 000 000 rows x 256 b = about 32 Gb. This calculation gives an idea not so bad for oracle. What about for PG ? How data is stored ? The different queries of the bench are "simple" queries (no join, sub-query, ...) and are using indexes (I "explained" each one to be sure) : Q1 select_court : access to about 700 rows : 1 "num_poste" and 1 month (using PK : num_poste=p1 and dat between p2 and p3) Q2 select_moy : access to about 7000 rows : 10 "num_poste" and 1 month (using PK : num_poste between p1 and p1+10 and dat between p2 and p3) Q3 select_long : about 250 000 rows : 2 "num_poste" (using PK : num_poste in (p1,p1+2)) Q4 select_tres_long : about 3 millions rows : 25 "num_poste" (using PK : num_poste between p1 and p1 + 25) The result is that for "short queries" (Q1 and Q2) it runs in a few seconds on both Oracle and PG. The difference becomes important with Q3 : 8 seconds with oracle 80 sec with PG and too much with Q4 : 28s with oracle 17m20s with PG ! Of course when I run 100 or 1000 parallel queries such as Q3 or Q4, it becomes a disaster ! I can't understand these results. The way to execute queries is the same I think. I've read recommended articles on the PG site. I tried with a table containing 30 millions rows, results are similar. What can I do ? Thanks for your help ! ******************************************************************** * Les points de vue exprimes sont strictement personnels et * * n'engagent pas la responsabilite de METEO-FRANCE. * ******************************************************************** * Valerie SCHNEIDER Tel : +33 (0)5 61 07 81 91 * * METEO-FRANCE / DSI/DEV Fax : +33 (0)5 61 07 81 09 * * 42, avenue G. Coriolis Email : Valerie.Schneider@meteo.fr * * 31057 TOULOUSE Cedex - FRANCE http://www.meteo.fr * ******************************************************************** From pgsql-performance-owner@postgresql.org Wed Aug 4 09:46:00 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3C02BD1B385 for ; Wed, 4 Aug 2004 09:45:59 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 27220-02 for ; Wed, 4 Aug 2004 12:46:04 +0000 (GMT) Received: from mail.clockltd.com (unknown [213.219.6.249]) by svr1.postgresql.org (Postfix) with ESMTP id D9967D1B37D for ; Wed, 4 Aug 2004 09:45:53 -0300 (ADT) Received: from [193.195.120.35] (helo=[10.0.0.113]) by mail.clockltd.com with asmtp (TLS-1.0:DHE_RSA_AES_128_CBC_SHA:16) (Exim 4.34) id 1BsL9X-0004St-4t for pgsql-performance@postgresql.org; Wed, 04 Aug 2004 13:45:55 +0100 Message-ID: <4110DA83.7020505@clockltd.com> Date: Wed, 04 Aug 2004 13:45:55 +0100 From: Paul Serby Organization: Clock User-Agent: Mozilla Thunderbird 0.7.1 (X11/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: The black art of postgresql.conf tweaking X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Clock-Relay: yes X-Clock-MailScanner-Information: Please contact the ISP for more information X-Clock-MailScanner: Found to be clean X-Clock-MailScanner-SpamCheck: not spam, SpamAssassin (score=0, required 5, autolearn=not spam) X-MailScanner-From: paul.serby@clockltd.com X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/45 X-Sequence-Number: 7681 Can anyone give a good reference site/book for getting the most out of your postgres server. All I can find is contradicting theories on how to work out your settings. This is what I followed to setup our db server that serves our web applications. http://www.phpbuilder.com/columns/smith20010821.php3?page=2 We have a Dell Poweredge with the following spec. CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) Physical Memory: 2077264 kB Swap Memory: 2048244 kB Apache on the Web server can take up to 300 connections and PHP is using pg_pconnect Postgres is set with the following. max_connections = 300 shared_buffers = 38400 sort_mem = 12000 But Apache is still maxing out the non-super user connection limit. The machine is under no load and I would like to up the max_connections but I would like to know more about what you need to consider before doing so. The only other source I've found is this: http://www.varlena.com/varlena/GeneralBits/Tidbits/annotated_conf_e.html But following its method my postgres server locks up straight away as it recommends setting max_connections to 16 for Web sites? Is there a scientific method for optimizing postgres or is it all 'finger in the air' and trial and error. From pgsql-performance-owner@postgresql.org Wed Aug 4 10:01:24 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 25054D1B285 for ; Wed, 4 Aug 2004 10:01:23 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 32305-01 for ; Wed, 4 Aug 2004 13:01:28 +0000 (GMT) Received: from rwcrmhc12.comcast.net (rwcrmhc12.comcast.net [216.148.227.85]) by svr1.postgresql.org (Postfix) with ESMTP id 96138D1B257 for ; Wed, 4 Aug 2004 10:01:15 -0300 (ADT) Received: from jefftrout.com ([24.128.241.68]) by comcast.net (rwcrmhc12) with SMTP id <2004080413012301400s92rve>; Wed, 4 Aug 2004 13:01:24 +0000 Received: (qmail 52506 invoked from network); 4 Aug 2004 13:01:23 -0000 Received: from unknown (HELO ?192.168.0.101?) (10.10.10.20) by 10.10.10.10 with SMTP; 4 Aug 2004 13:01:23 -0000 In-Reply-To: <4110DA83.7020505@clockltd.com> References: <4110DA83.7020505@clockltd.com> Mime-Version: 1.0 (Apple Message framework v618) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: <85562EA8-E616-11D8-A77F-000393D1F76E@torgo.978.org> Content-Transfer-Encoding: 7bit Cc: pgsql-performance@postgresql.org From: Jeff Subject: Re: The black art of postgresql.conf tweaking Date: Wed, 4 Aug 2004 09:02:20 -0400 To: Paul Serby X-Mailer: Apple Mail (2.618) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/46 X-Sequence-Number: 7682 On Aug 4, 2004, at 8:45 AM, Paul Serby wrote: > > Apache on the Web server can take up to 300 connections and PHP is > using pg_pconnect > > Postgres is set with the following. > > max_connections = 300 > shared_buffers = 38400 > sort_mem = 12000 > > But Apache is still maxing out the non-super user connection limit. > Did you restart PG after making that change? (you need to restart, reload won't change max_connections) Also, you're sort_mem is likely too high (That is the amount of memory that can be used PER SORT) and you s hould back down on shared_buffers. (General consensus is don't go over 10k shared buffers) Another thing you may want to try is using pgpool and regular pg_connect - this way you only have a pool of say, 32 connections to the DB that are shared among all apache instances. This gets rid of the need to have hundreds of idle postgres' sitting around. Connecting to pgpool is very fast. We use it in production here and it works wonderfully. And it is 100% transparent to your application. -- Jeff Trout http://www.jefftrout.com/ http://www.stuarthamm.net/ From pgsql-performance-owner@postgresql.org Wed Aug 4 10:10:43 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 94B46D1B34A for ; Wed, 4 Aug 2004 10:10:42 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 32590-03 for ; Wed, 4 Aug 2004 13:10:46 +0000 (GMT) Received: from mx.mall.cz (mx.mall.cz [62.168.45.106]) by svr1.postgresql.org (Postfix) with ESMTP id 86B67D1B1DF for ; Wed, 4 Aug 2004 10:10:35 -0300 (ADT) Received: from localhost (localhost.localdomain [127.0.0.1]) by mx.mall.cz (Postfix) with ESMTP id 2A9A04810E; Wed, 4 Aug 2004 15:10:43 +0200 (CEST) Received: from mx.mall.cz ([127.0.0.1]) by localhost (posta [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 28620-01; Wed, 4 Aug 2004 15:10:34 +0200 (CEST) Message-ID: <4110E05F.9030404@taborsky.cz> Date: Wed, 04 Aug 2004 15:10:55 +0200 From: Michal Taborsky User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Paul Serby Cc: pgsql-performance@postgresql.org Subject: Re: The black art of postgresql.conf tweaking References: <4110DA83.7020505@clockltd.com> In-Reply-To: <4110DA83.7020505@clockltd.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/47 X-Sequence-Number: 7683 Paul Serby wrote: > Apache on the Web server can take up to 300 connections and PHP is using > pg_pconnect > max_connections = 300 > But Apache is still maxing out the non-super user connection limit. Don't forget also that some connections are reserved for superusers (usually 2), so if you want 300 users, you need to set max_connections to 300 + superuser_reserved_connections. -- Michal Taborsky http://www.taborsky.cz From pgsql-general-owner@postgresql.org Wed Aug 4 10:22:02 2004 X-Original-To: pgsql-general-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 09386D1B1A1; Wed, 4 Aug 2004 10:22:01 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 36664-01; Wed, 4 Aug 2004 13:22:05 +0000 (GMT) Received: from houston.familyhealth.com.au (fhnet.arach.net.au [203.22.197.21]) by svr1.postgresql.org (Postfix) with ESMTP id 2E445D1B257; Wed, 4 Aug 2004 10:21:52 -0300 (ADT) Received: from houston.familyhealth.com.au (chriskl@localhost [127.0.0.1]) by houston.familyhealth.com.au (8.12.9p1/8.12.9) with ESMTP id i74DLpUi006535; Wed, 4 Aug 2004 21:21:51 +0800 (WST) (envelope-from chriskl@familyhealth.com.au) Received: from localhost (chriskl@localhost) by houston.familyhealth.com.au (8.12.9p1/8.12.9/Submit) with ESMTP id i74DLpqC006532; Wed, 4 Aug 2004 21:21:51 +0800 (WST) X-Authentication-Warning: houston.familyhealth.com.au: chriskl owned process doing -bs Date: Wed, 4 Aug 2004 21:21:51 +0800 (WST) From: Christopher Kings-Lynne To: Valerie Schneider DSI/DEV Cc: pgsql-performance@postgresql.org, Subject: Re: [PERFORM] Tuning queries on large database In-Reply-To: <200408041244.i74CihO19344@mu.meteo.fr> Message-ID: <20040804211849.L3435-100000@houston.familyhealth.com.au> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/83 X-Sequence-Number: 63638 > sort_mem = 50000 That is way, way too large. Try more like 5000 or lower. > num_poste | numeric(9,0) | not null For starters numerics are really, really slow compared to integers. Why aren't you using an integer for this field since youhave '0' decimal places. > schema | relfilenode | table | index | reltuples | size > --------+-------------+------------------+------------+-------------+---------- > public | 125615917 | data | | 1.25113e+08 | 72312040 > public | 251139049 | data | i_data_dat | 1.25113e+08 | 2744400 > public | 250870177 | data | pk_data | 1.25113e+08 | 4395480 > > My first remark is that the table takes a lot of place on disk, about > 70 Gb, instead of 35 Gb with oracle. Integers will take a lot less space than numerics. > The different queries of the bench are "simple" queries (no join, > sub-query, ...) and are using indexes (I "explained" each one to > be sure) : > Q1 select_court : access to about 700 rows : 1 "num_poste" and 1 month > (using PK : num_poste=p1 and dat between p2 and p3) > Q2 select_moy : access to about 7000 rows : 10 "num_poste" and 1 month > (using PK : num_poste between p1 and p1+10 and dat between p2 and p3) > Q3 select_long : about 250 000 rows : 2 "num_poste" > (using PK : num_poste in (p1,p1+2)) > Q4 select_tres_long : about 3 millions rows : 25 "num_poste" > (using PK : num_poste between p1 and p1 + 25) > > The result is that for "short queries" (Q1 and Q2) it runs in a few > seconds on both Oracle and PG. The difference becomes important with > Q3 : 8 seconds with oracle > 80 sec with PG > and too much with Q4 : 28s with oracle > 17m20s with PG ! > > Of course when I run 100 or 1000 parallel queries such as Q3 or Q4, > it becomes a disaster ! Please reply with the EXPLAIN ANALYZE output of these queries so we can have some idea of how to help you. Chris From pgsql-performance-owner@postgresql.org Wed Aug 4 10:30:20 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id C15BBD1B1AE for ; Wed, 4 Aug 2004 10:30:17 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 38664-02 for ; Wed, 4 Aug 2004 13:30:21 +0000 (GMT) Received: from pw6tiger.de (pw6tiger.de [217.160.140.116]) by svr1.postgresql.org (Postfix) with SMTP id 4699CD1B1A1 for ; Wed, 4 Aug 2004 10:30:08 -0300 (ADT) Received: (qmail 22959 invoked by uid 505); 4 Aug 2004 13:29:51 -0000 Received: from vygen@gmx.de by planwerk6 by uid 89 with qmail-scanner-1.14 (virus scan: Clear:. Processed in 0.238747 secs); 04 Aug 2004 13:29:51 -0000 Received: from isi-dial-153-153.isionline-dialin.de (HELO ?192.168.1.10?) (vygen@planwerk6.de@195.158.153.153) by pw6tiger.de with SMTP; 4 Aug 2004 13:29:51 -0000 From: Janning Vygen To: pgsql-performance@postgresql.org Subject: Re: The black art of postgresql.conf tweaking Date: Wed, 4 Aug 2004 15:26:30 +0200 User-Agent: KMail/1.6.2 Cc: Paul Serby References: <4110DA83.7020505@clockltd.com> In-Reply-To: <4110DA83.7020505@clockltd.com> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200408041526.30460.vygen@gmx.de> X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/50 X-Sequence-Number: 7686 Am Mittwoch, 4. August 2004 14:45 schrieb Paul Serby: > Apache on the Web server can take up to 300 connections and PHP is using > pg_pconnect > > Postgres is set with the following. > > max_connections = 300 > shared_buffers = 38400 > sort_mem = 12000 > > But Apache is still maxing out the non-super user connection limit. for most websites 300 connections is far too much (imagine even 10 request per second for 10 hours a day ends up to 10.8 Mio pages a month) but anyway: you should first focus on closing your http connection to the user as fast as possible. then you dont need so much concurrent connections which keep db connections open and uses memory. I did the following: - apache: keepalive off - apache patch: lingerd (google for it) - apache mod_gzip - pg_pconnect this keeps your http connection as short as possible, so the apache child is ready to serve the next client. Imagine 5 seconds of keepalive 1 second on lingering half-closed tcp connections and 4 more seconds for transport of uncompressed content. in this scenario your apache child uses memory an your pooled db connection for 10 seconds while doing nothing! in my experience apache in standard configuration can be the main bottleneck. and teh combination of keepalive off, lingerd and mod_gzip is GREAT and i didn't found much sites propagating a configuration like this. kind regards, janning p.s: sorry for being slightly off topic and talking about apache but when it comes to performance it is always important to look at the complete system. From pgsql-performance-owner@postgresql.org Wed Aug 4 10:26:43 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 7E261D1B192 for ; Wed, 4 Aug 2004 10:26:41 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 38701-01 for ; Wed, 4 Aug 2004 13:26:46 +0000 (GMT) Received: from tht.net (vista.tht.net [216.126.88.2]) by svr1.postgresql.org (Postfix) with ESMTP id EBAC4D1B1C8 for ; Wed, 4 Aug 2004 10:26:35 -0300 (ADT) Received: from [134.22.68.4] (dyn-68-4.tor.dsl.tht.net [134.22.68.4]) by tht.net (Postfix) with ESMTP id 5D66276B36; Wed, 4 Aug 2004 09:26:45 -0400 (EDT) Subject: Re: Tuning queries on large database From: Rod Taylor To: Valerie Schneider DSI/DEV Cc: Postgresql Performance In-Reply-To: <200408041244.i74CihO19344@mu.meteo.fr> References: <200408041244.i74CihO19344@mu.meteo.fr> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-nHPhfWiYy5OOuJH9qNB8" Message-Id: <1091625999.58593.47.camel@jester> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Wed, 04 Aug 2004 09:26:42 -0400 X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/49 X-Sequence-Number: 7685 --=-nHPhfWiYy5OOuJH9qNB8 Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Wed, 2004-08-04 at 08:44, Valerie Schneider DSI/DEV wrote: > Hi, >=20 > I have some problem of performance on a PG database, and I don't > know how to improve. I Have two questions : one about the storage > of data, one about tuning queries. If possible ! >=20 > My job is to compare Oracle and Postgres. All our operational databases > have been running under Oracle for about fifteen years. Now I try to repl= ace > Oracle by Postgres. You may assume some additional hardware may be required -- this would be purchased out of the Oracle License budget :) > My first remark is that the table takes a lot of place on disk, about > 70 Gb, instead of 35 Gb with oracle. > 125 000 000 rows x 256 b =3D about 32 Gb. This calculation gives an idea > not so bad for oracle. What about for PG ? How data is stored ? This is due to the datatype you've selected. PostgreSQL does not convert NUMERIC into a more appropriate integer format behind the scenes, nor will it use the faster routines for the math when it is an integer. Currently it makes the assumption that if you've asked for numeric rather than integer or float that you are dealing with either large numbers or require high precision math. Changing most of your columns to integer + Check constraint (where necessary) will give you a large speed boost and reduce disk requirements a little. > The different queries of the bench are "simple" queries (no join, > sub-query, ...) and are using indexes (I "explained" each one to > be sure) : Care to send us the EXPLAIN ANALYZE output for each of the 4 queries after you've improved the datatype selection? --=20 Rod Taylor Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL PGP Key: http://www.rbt.ca/signature.asc --=-nHPhfWiYy5OOuJH9qNB8 Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQBBEOQO6DETLow6vwwRAll7AJ0WFK5XCtJMKSB2/0k2bgp5pxpCDACfXmZO i6ic30tZ+P81wrwzyP49E6E= =CuEp -----END PGP SIGNATURE----- --=-nHPhfWiYy5OOuJH9qNB8-- From pgsql-performance-owner@postgresql.org Wed Aug 4 10:44:09 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 30E15D1B1A1 for ; Wed, 4 Aug 2004 10:44:08 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 42070-04 for ; Wed, 4 Aug 2004 13:44:12 +0000 (GMT) Received: from anchor-post-37.mail.demon.net (anchor-post-36.mail.demon.net [194.217.242.86]) by svr1.postgresql.org (Postfix) with ESMTP id 2C158D1B17B for ; Wed, 4 Aug 2004 10:44:02 -0300 (ADT) Received: from tmsl-adsl.demon.co.uk ([80.177.114.181] helo=bacon.tmsl.demon.co.uk) by anchor-post-37.mail.demon.net with esmtp (Exim 3.35 #1) id 1BsM3v-000CNx-0b for pgsql-performance@postgresql.org; Wed, 04 Aug 2004 13:44:11 +0000 Date: Wed, 4 Aug 2004 14:44:08 +0100 From: Paul Thomas To: "pgsql-performance @ postgresql . org" Subject: Re: The black art of postgresql.conf tweaking Message-ID: <20040804144408.A17081@bacon> References: <4110DA83.7020505@clockltd.com> Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset=ISO-8859-1 In-Reply-To: <4110DA83.7020505@clockltd.com>; from paul.serby@clockltd.com on Wed, Aug 04, 2004 at 13:45:55 +0100 X-Mailer: Balsa 1.2.3 Lines: 87 X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/51 X-Sequence-Number: 7687 On 04/08/2004 13:45 Paul Serby wrote: > Can anyone give a good reference site/book for getting the most out of > your postgres server. > > All I can find is contradicting theories on how to work out your > settings. > > This is what I followed to setup our db server that serves our web > applications. > > http://www.phpbuilder.com/columns/smith20010821.php3?page=2 > > We have a Dell Poweredge with the following spec. > > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > Physical Memory: 2077264 kB > Swap Memory: 2048244 kB > > Apache on the Web server can take up to 300 connections and PHP is > using pg_pconnect > > Postgres is set with the following. > > max_connections = 300 > shared_buffers = 38400 Might be higher that neccessary. Some people reckon that there's no measurable performance going above ~10,000 buffers > sort_mem = 12000 Do you really need 12MB of sort memory? Remember that this is per connection so you could end up with 300x that being allocated in a worst case scenario. > > But Apache is still maxing out the non-super user connection limit. > > The machine is under no load and I would like to up the max_connections > but I would like to know more about what you need to consider before > doing so. I can't think why you should be maxing out when under no load. Maybe you need to investigate this further. > > The only other source I've found is this: > > http://www.varlena.com/varlena/GeneralBits/Tidbits/annotated_conf_e.html > > But following its method my postgres server locks up straight away as it > recommends setting max_connections to 16 for Web sites? I think you've mis-interpreted that. She's talking about using persistent connections - i.e., connection pooling. > > Is there a scientific method for optimizing postgres or is it all > 'finger in the air' and trial and error. Posting more details of the queries which are giving the performance problems will enable people to help you. You're vacuum/analyzing regularly of course ;) People will want to know: - PostgreSQL version - hardware configuration (SCSI or IDE? RAID level?) - table schemas - queries together with EXPLAIN ANALYZE output also output from utils like vmstat, top etc may be of use. HTH -- Paul Thomas +------------------------------+---------------------------------------------+ | Thomas Micro Systems Limited | Software Solutions for Business | | Computer Consultants | http://www.thomas-micro-systems-ltd.co.uk | +------------------------------+---------------------------------------------+ From pgsql-performance-owner@postgresql.org Wed Aug 4 11:11:37 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3AAE8D1B37D for ; Wed, 4 Aug 2004 11:11:35 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 50052-04 for ; Wed, 4 Aug 2004 14:11:39 +0000 (GMT) Received: from cadillac.meteo.fr (cadillac.meteo.fr [137.129.1.4]) by svr1.postgresql.org (Postfix) with ESMTP id A3CB5D1B285 for ; Wed, 4 Aug 2004 11:11:27 -0300 (ADT) Received: from mu.meteo.fr (localhost.meteo.fr [127.0.0.1]) by cadillac.meteo.fr (8.9.3 (PHNE_28760_binary)/8.9.3) with ESMTP id OAA13874 for ; Wed, 4 Aug 2004 14:11:36 GMT Received: from mu.meteo.fr (mu.meteo.fr [137.129.6.129]) by mu.meteo.fr (8.11.7p1+Sun/8.11.7) with SMTP id i74ECYO19577 for ; Wed, 4 Aug 2004 14:12:34 GMT Message-Id: <200408041412.i74ECYO19577@mu.meteo.fr> Date: Wed, 4 Aug 2004 14:12:34 +0000 (GMT) From: Valerie Schneider DSI/DEV Reply-To: Valerie Schneider DSI/DEV Subject: Re: Tuning queries on large database To: pgsql-performance@postgresql.org MIME-Version: 1.0 Content-Type: TEXT/plain; charset=us-ascii Content-MD5: 91AJxcJfxQX3viRBZc6njg== X-Mailer: dtmail 1.3.0 @(#)CDE Version 1.4.6_06 SunOS 5.8 sun4u sparc X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/52 X-Sequence-Number: 7688 >X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org >X-Authentication-Warning: houston.familyhealth.com.au: chriskl owned process doing -bs >Date: Wed, 4 Aug 2004 21:21:51 +0800 (WST) >From: Christopher Kings-Lynne >To: Valerie Schneider DSI/DEV >Cc: pgsql-performance@postgresql.org, >Subject: Re: [PERFORM] Tuning queries on large database >MIME-Version: 1.0 >X-Virus-Scanned: by amavisd-new at hub.org >X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= >X-Spam-Level: >X-Mailing-List: pgsql-performance > >> sort_mem = 50000 > >That is way, way too large. Try more like 5000 or lower. > >> num_poste | numeric(9,0) | not null > >For starters numerics are really, really slow compared to integers. Why >aren't you using an integer for this field since youhave '0' decimal >places. > >> schema | relfilenode | table | index | reltuples | size >> --------+-------------+------------------+------------+-------------+---------- >> public | 125615917 | data | | 1.25113e+08 | 72312040 >> public | 251139049 | data | i_data_dat | 1.25113e+08 | 2744400 >> public | 250870177 | data | pk_data | 1.25113e+08 | 4395480 >> >> My first remark is that the table takes a lot of place on disk, about >> 70 Gb, instead of 35 Gb with oracle. > >Integers will take a lot less space than numerics. > >> The different queries of the bench are "simple" queries (no join, >> sub-query, ...) and are using indexes (I "explained" each one to >> be sure) : >> Q1 select_court : access to about 700 rows : 1 "num_poste" and 1 month >> (using PK : num_poste=p1 and dat between p2 and p3) >> Q2 select_moy : access to about 7000 rows : 10 "num_poste" and 1 month >> (using PK : num_poste between p1 and p1+10 and dat between p2 and p3) >> Q3 select_long : about 250 000 rows : 2 "num_poste" >> (using PK : num_poste in (p1,p1+2)) >> Q4 select_tres_long : about 3 millions rows : 25 "num_poste" >> (using PK : num_poste between p1 and p1 + 25) >> >> The result is that for "short queries" (Q1 and Q2) it runs in a few >> seconds on both Oracle and PG. The difference becomes important with >> Q3 : 8 seconds with oracle >> 80 sec with PG >> and too much with Q4 : 28s with oracle >> 17m20s with PG ! >> >> Of course when I run 100 or 1000 parallel queries such as Q3 or Q4, >> it becomes a disaster ! > >Please reply with the EXPLAIN ANALYZE output of these queries so we can >have some idea of how to help you. > >Chris > > > >---------------------------(end of broadcast)--------------------------- >TIP 4: Don't 'kill -9' the postmaster Q1 : bench=> explain analyze select 'Q1',min(td),max(u) from data where num_poste=1000 and dat between (date_trunc('month',to_timestamp('31012004','ddmmyyyy')-interval '2000 days'))::timestamp and (date_trunc('month',to_timestamp('31012004','ddmmyyyy')-interval '2000 days') + interval '1 month' - interval '1 hour')::timestamp; QUERY PLAN -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ---------------------------------------------------------------------- Aggregate (cost=2501.90..2501.90 rows=1 width=21) (actual time=581.460..581.461 rows=1 loops=1) -> Index Scan using pk_data on data (cost=0.00..2498.80 rows=619 width=21) (actual time=92.986..579.089 rows=744 loops=1) Index Cond: ((num_poste = 1000::numeric) AND (dat >= (date_trunc('month'::text, (to_timestamp('31012004'::text, 'ddmmyyyy'::text) - '2000 days'::interval)))::timestamp without time zone) AND (dat <= (((date_trunc('month'::text, (to_timestamp('31012004'::text, 'ddmmyyyy'::text) - '2000 days'::interval)) + '1 mon'::interval) - '01:00:00'::interval))::timestamp without time zone)) Total runtime: 609.149 ms (4 rows) Q2 : bench=> explain analyze select 'Q2',count(*) from data where num_poste between 100 and 100+10 and dat between (date_trunc('month',to_timestamp('31012004','ddmmyyyy')-interval '3000 days'))::timestamp and (date_trunc('month',to_timestamp('31012004','ddmmyyyy')-interval '3000 days') + interval '1 month' - interval '1 hour')::timestamp; QUERY PLAN -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ---------------------- Aggregate (cost=23232.05..23232.05 rows=1 width=0) (actual time=5678.849..5678.850 rows=1 loops=1) -> Index Scan using pk_data on data (cost=0.00..23217.68 rows=5747 width=0) (actual time=44.408..5669.387 rows=7920 loops=1) Index Cond: ((num_poste >= 100::numeric) AND (num_poste <= 110::numeric) AND (dat >= (date_trunc('month'::text, (to_timestamp('31012004'::text, 'ddmmyyyy'::text) - '3000 days'::interval)))::timestamp without time zone) AND (dat <= (((date_trunc('month'::text, (to_timestamp('31012004'::text, 'ddmmyyyy'::text) - '3000 days'::interval)) + '1 mon'::interval) - '01:00:00'::interval))::timestamp without time zone)) Total runtime: 5679.059 ms (4 rows) Q3 : bench=> explain analyze select 'Q3',sum(rr1),count(ff) from data where num_poste in (50,50+2); QUERY PLAN -------------------------------------------------------------------------------- ------------------------------------------------------------------ Aggregate (cost=986770.56..986770.56 rows=1 width=17) (actual time=75401.030..75401.031 rows=1 loops=1) -> Index Scan using pk_data, pk_data on data (cost=0.00..985534.43 rows=247225 width=17) (actual time=35.823..74885.689 rows=250226 loops=1) Index Cond: ((num_poste = 50::numeric) OR (num_poste = 52::numeric)) Total runtime: 75405.666 ms (4 rows) Q4 : bench=> explain analyze select 'Q4',count(*) from data where num_poste between 600 and 625; QUERY PLAN -------------------------------------------------------------------------------- -------------------------------------------------------------- Aggregate (cost=12166763.62..12166763.62 rows=1 width=0) (actual time=1162090.302..1162090.303 rows=1 loops=1) -> Index Scan using pk_data on data (cost=0.00..12159021.19 rows=3096971 width=0) (actual time=94.679..1158266.561 rows=3252938 loops=1) Index Cond: ((num_poste >= 600::numeric) AND (num_poste <= 625::numeric)) Total runtime: 1162102.217 ms (4 rows) Now I'm going to recreate my table with integer and real datatype, and to decrease sort_mem to 5000. Then I'll try these queries again. Thanks. ******************************************************************** * Les points de vue exprimes sont strictement personnels et * * n'engagent pas la responsabilite de METEO-FRANCE. * ******************************************************************** * Valerie SCHNEIDER Tel : +33 (0)5 61 07 81 91 * * METEO-FRANCE / DSI/DEV Fax : +33 (0)5 61 07 81 09 * * 42, avenue G. Coriolis Email : Valerie.Schneider@meteo.fr * * 31057 TOULOUSE Cedex - FRANCE http://www.meteo.fr * ******************************************************************** From pgsql-performance-owner@postgresql.org Wed Aug 4 11:51:47 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 964AFD1B17B for ; Wed, 4 Aug 2004 11:51:44 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 61590-02 for ; Wed, 4 Aug 2004 14:51:49 +0000 (GMT) Received: from stubee.d2hosting.net (d2hosting.net [66.70.41.160]) by svr1.postgresql.org (Postfix) with ESMTP id B94C1D1B1C8 for ; Wed, 4 Aug 2004 11:51:37 -0300 (ADT) Received: from [127.0.0.1] (stubee.d2hosting.net [66.70.41.160]) by stubee.d2hosting.net (8.11.6/linuxconf) with ESMTP id i74EpJi24735; Wed, 4 Aug 2004 09:51:19 -0500 Message-ID: <4110F7E0.4050204@idigx.com> Date: Wed, 04 Aug 2004 09:51:12 -0500 From: Thomas Swan User-Agent: Mozilla Thunderbird 0.7.2 (Windows/20040707) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Janning Vygen Cc: pgsql-performance@postgresql.org, Paul Serby Subject: Re: The black art of postgresql.conf tweaking References: <4110DA83.7020505@clockltd.com> <200408041526.30460.vygen@gmx.de> In-Reply-To: <200408041526.30460.vygen@gmx.de> X-Enigmail-Version: 0.85.0.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/53 X-Sequence-Number: 7689 Janning Vygen wrote: >Am Mittwoch, 4. August 2004 14:45 schrieb Paul Serby: > > >>Apache on the Web server can take up to 300 connections and PHP is using >> pg_pconnect >> >>Postgres is set with the following. >> >>max_connections = 300 >>shared_buffers = 38400 >>sort_mem = 12000 >> >>But Apache is still maxing out the non-super user connection limit >> The number of connections in apache and in postgresql are the keys. From what you've described, apache can have up to 300 child processes. If this application uses a different identity or db for different connects then you may have more than one connection open per process easily exhausting your available connections. Also, your application may open multiple connections to postgresql per process. See if setting max_connections in postgres to a larger works, but you may want to reduce your sort_mem proportionately to keep from overbooking your system. >for most websites 300 connections is far too much (imagine even 10 request per >second for 10 hours a day ends up to 10.8 Mio pages a month) > >but anyway: you should first focus on closing your http connection to the user >as fast as possible. then you dont need so much concurrent connections which >keep db connections open and uses memory. > >I did the following: >- apache: keepalive off >- apache patch: lingerd (google for it) >- apache mod_gzip >- pg_pconnect > > KeepAlive for 2 or 3 seconds is quite sufficient. This keeps the current number of connections down for those browsers that support it, and keeps the server from leaving too many open. We found KeepAlive off caused too many http connections to be opened and closed for our applications and hardware to keep up. The benefit is facilitating a rapid succession of requests: page loads, graphics, embedded objects, frames, etc. >p.s: sorry for being slightly off topic and talking about apache but when it >comes to performance it is always important to look at the complete system. > > Good advice. From pgsql-performance-owner@postgresql.org Fri Aug 6 13:11:19 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 182445E46CB for ; Fri, 6 Aug 2004 13:11:16 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 16597-04 for ; Fri, 6 Aug 2004 16:11:18 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 959075E46D6 for ; Fri, 6 Aug 2004 13:11:09 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i76GB661081375 for ; Fri, 6 Aug 2004 16:11:16 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i76G1AG1080059 for pgsql-performance@postgresql.org; Fri, 6 Aug 2004 16:01:10 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Performance Bottleneck Date: Wed, 04 Aug 2004 17:25:42 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 112 Message-ID: <4110FFF6.1030001@bigfoot.com> References: <410FDC53.5080509@bigfoot.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: Martin Foster User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/77 X-Sequence-Number: 7713 Martin Foster wrote: > Gaetano Mendola wrote: > >> Martin Foster wrote: >> >>> I run a Perl/CGI driven website that makes extensive use of >>> PostgreSQL (7.4.3) for everything from user information to formatting >>> and display of specific sections of the site. The server itself, is >>> a dual processor AMD Opteron 1.4Ghz w/ 2GB Ram and 2 x 120GB hard >>> drives mirrored for redundancy running under FreeBSD 5.2.1 (AMD64). >>> >>> Recently loads on the site have increased during peak hours to the >>> point of showing considerable loss in performance. This can be >>> observed when connections move from the 120 concurrent connections to >>> PostgreSQL to roughly 175 or more. Essentially, the machine seems >>> to struggle to keep up with continual requests and slows down >>> respectively as resources are tied down. >>> >>> Code changes have been made to the scripts to essentially back off in >>> high load working environments which have worked to an extent. >>> However, as loads continue to increase the database itself is not >>> taking well to the increased traffic taking place. >>> >>> Having taken a look at 'Tuning PostgreSQL for Performance' >>> (http://www.varlena.com/GeneralBits/Tidbits/perf.html) using it as >>> best I could in order to set my settings. However, even with >>> statistics disabled and ever setting tweaked things still consider to >>> deteriorate. >>> >>> Is there anything anyone can recommend in order to give the system a >>> necessary speed boost? It would seem to me that a modest dataset of >>> roughly a Gig combined with that type of hardware should be able to >>> handle substantially more load then what it is. Can anyone provide >>> me with clues as where to pursue? Would disabling 'fsync' provide >>> more performance if I choose that information may be lost in case of >>> a crash? >>> >>> If anyone needs access to logs, settings et cetera. Please ask, I >>> simply wish to test the waters first on what is needed. Thanks! >> >> >> >> Tell us about your tipical queries, show us your configuration file. >> The access are only in read only mode or do you have concurrent writers >> and readers ? During peak hours your processors are tied to 100% ? >> What say the vmstat and the iostat ? >> >> May be you are not using indexes some where, or may be yes but the >> planner is not using it... In two words we needs other informations >> in order to help you. >> >> >> >> Regards >> Gaetano Mendola >> >> > > I included all the files in attachments, which will hopefully cut down > on any replied to Emails. As for things like connection pooling, the > web server makes use of Apache::DBI to pool the connections for the Perl > scripts being driven on that server. For the sake of being thorough, > a quick 'apachectl status' was thrown in when the database was under a > good load. Let start from your postgres configuration: shared_buffers = 8192 <==== This is really too small for your configuration sort_mem = 2048 wal_buffers = 128 <==== This is really too small for your configuration effective_cache_size = 16000 change this values in: shared_buffers = 50000 sort_mem = 16084 wal_buffers = 1500 effective_cache_size = 32000 to bump up the shm usage you have to configure your OS in order to be allowed to use that ammount of SHM. This are the numbers that I feel good for your HW, the second step now is analyze your queries > The queries themselves are simple, normally drawing information from one > table with few conditions or in the most complex cases using joins on > two table or sub queries. These behave very well and always have, the > problem is that these queries take place in rather large amounts due to > the dumb nature of the scripts themselves. Show us the explain analyze on that queries, how many rows the tables are containing, the table schema could be also usefull. regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Fri Aug 6 13:17:12 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 050715E46C2 for ; Fri, 6 Aug 2004 13:11:07 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 14467-09 for ; Fri, 6 Aug 2004 16:11:09 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 749CC5E46C7 for ; Fri, 6 Aug 2004 13:11:00 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i76GB65l081375 for ; Fri, 6 Aug 2004 16:11:07 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i76G1BxH080061 for pgsql-performance@postgresql.org; Fri, 6 Aug 2004 16:01:11 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: The black art of postgresql.conf tweaking Date: Wed, 04 Aug 2004 17:29:48 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 41 Message-ID: <411100EC.8010802@bigfoot.com> References: <4110DA83.7020505@clockltd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: Paul Serby User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: <4110DA83.7020505@clockltd.com> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/78 X-Sequence-Number: 7714 Paul Serby wrote: > Can anyone give a good reference site/book for getting the most out of > your postgres server. > > All I can find is contradicting theories on how to work out your settings. > > This is what I followed to setup our db server that serves our web > applications. > > http://www.phpbuilder.com/columns/smith20010821.php3?page=2 > > We have a Dell Poweredge with the following spec. > > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > Physical Memory: 2077264 kB > Swap Memory: 2048244 kB > > Apache on the Web server can take up to 300 connections and PHP is using > pg_pconnect > > Postgres is set with the following. > > max_connections = 300 > shared_buffers = 38400 > sort_mem = 12000 > > But Apache is still maxing out the non-super user connection limit. Tell us the value MaxClients in your apache configuration Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Fri Aug 6 13:11:12 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 4327E5E46DB for ; Fri, 6 Aug 2004 13:11:11 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 14423-09 for ; Fri, 6 Aug 2004 16:11:14 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id BDF305E46CD for ; Fri, 6 Aug 2004 13:11:05 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i76GB65n081375 for ; Fri, 6 Aug 2004 16:11:08 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i76G1BLs080063 for pgsql-performance@postgresql.org; Fri, 6 Aug 2004 16:01:11 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Tuning queries on large database Date: Wed, 04 Aug 2004 17:34:56 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 20 Message-ID: <41110220.7000006@bigfoot.com> References: <200408041244.i74CihO19344@mu.meteo.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: Valerie Schneider DSI/DEV User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: <200408041244.i74CihO19344@mu.meteo.fr> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/74 X-Sequence-Number: 7710 Valerie Schneider DSI/DEV wrote: > Hi, > > I have some problem of performance on a PG database, and I don't > know how to improve. I Have two questions : one about the storage > of data, one about tuning queries. If possible ! > > My job is to compare Oracle and Postgres. All our operational databases > have been running under Oracle for about fifteen years. Now I try to replace > Oracle by Postgres. Show us the explain analyze on your queries. Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Wed Aug 4 12:36:33 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 9846BD1B298 for ; Wed, 4 Aug 2004 12:36:31 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 74454-08 for ; Wed, 4 Aug 2004 15:36:27 +0000 (GMT) Received: from mail3.panix.com (mail3.panix.com [166.84.1.74]) by svr1.postgresql.org (Postfix) with ESMTP id A479DD1B1C8 for ; Wed, 4 Aug 2004 12:36:25 -0300 (ADT) Received: from panix2.panix.com (panix2.panix.com [166.84.1.2]) by mail3.panix.com (Postfix) with ESMTP id A01E0982CC; Wed, 4 Aug 2004 11:36:24 -0400 (EDT) Received: (from adler@localhost) by panix2.panix.com (8.11.6p2-a/8.8.8/PanixN1.1) id i74FaO311313; Wed, 4 Aug 2004 11:36:24 -0400 (EDT) Date: Wed, 4 Aug 2004 11:36:24 -0400 From: Michael Adler To: Martin Foster Cc: pgsql-performance@postgresql.org Subject: Re: Performance Bottleneck Message-ID: <20040804153624.GA27551@pobox.com> References: <410FDC53.5080509@bigfoot.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/54 X-Sequence-Number: 7690 On Wed, Aug 04, 2004 at 03:49:11AM +0000, Martin Foster wrote: > Also note that some of these scripts run for longer durations even if > they are web based. Some run as long as 30 minutes, making queries to > the database from periods of wait from five seconds to twenty-five > seconds. Under high duress the timeouts should back out, based on > the time needed for the query to respond, normally averaging 0.008 seconds. I would start by EXPLAIN ANALYZE'ing those 30 minute queries. > martin@io ~$ vmstat > procs memory page disks faults cpu > r b w avm fre flt re pi po fr sr ad4 ad6 in sy cs us sy id > 0 0 0 498532 122848 3306 0 0 0 740 0 0 0 788 0 1675 16 21 63 > vmstat without a "delay" argument (e.g. 'vmstat 1') gives you a cumulative or average since boot. You'd probably get better information by doing a real-time sampling of stats during normal and heavy load. > martin@io ~$ ps -uax > USER PID %CPU %MEM VSZ RSS TT STAT STARTED TIME COMMAND > postgres 32084 0.0 0.2 91616 3764 p0- R Mon12PM 4:08.99 /usr/local/bin/postmaster -D /var/postgres (postgres) > postgres 80333 0.0 2.1 94620 44372 ?? S 8:57PM 0:01.00 postmaster: ethereal ethereal 192.168.1.6 idle in trans > postgres 80599 0.0 2.1 94652 44780 ?? S 8:59PM 0:00.97 postmaster: ethereal ethereal 192.168.1.6 idle in trans > postgres 80616 0.0 2.4 94424 50396 ?? S 8:59PM 0:00.89 postmaster: ethereal ethereal 192.168.1.6 idle in trans > postgres 80715 0.0 2.2 94444 46804 ?? S 9:00PM 0:00.68 postmaster: ethereal ethereal 192.168.1.6 idle in trans > postgres 80788 0.0 2.1 94424 43944 ?? S 9:00PM 0:00.93 postmaster: ethereal ethereal 192.168.1.6 idle in trans > postgres 80811 0.0 2.1 94424 43884 ?? S 9:00PM 0:00.94 postmaster: ethereal ethereal 192.168.1.6 idle in trans > postgres 80902 0.0 2.1 94424 43380 ?? S 9:01PM 0:00.76 postmaster: ethereal ethereal 192.168.1.6 idle in trans > postgres 80949 0.0 2.2 94424 45248 ?? S 9:01PM 0:00.67 postmaster: ethereal ethereal 192.168.1.6 idle in trans > postgres 81020 0.0 2.1 94424 42924 ?? S 9:02PM 0:00.74 postmaster: ethereal ethereal 192.168.1.6 idle in trans All the connections in your email are idle. You may benefit from using pgpool instead of Apache::DBI (I've never tried). http://www.mail-archive.com/pgsql-announce@postgresql.org/msg00760.html From pgsql-performance-owner@postgresql.org Wed Aug 4 12:51:09 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 81FE6D1B1C8 for ; Wed, 4 Aug 2004 12:51:07 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 80565-04 for ; Wed, 4 Aug 2004 15:51:00 +0000 (GMT) Received: from boutiquenumerique.com (gailleton-2-82-67-9-10.fbx.proxad.net [82.67.9.10]) by svr1.postgresql.org (Postfix) with ESMTP id 813A8D1B1B4 for ; Wed, 4 Aug 2004 12:50:58 -0300 (ADT) Received: (qmail 5071 invoked from network); 4 Aug 2004 17:50:56 +0200 Received: from unknown (HELO musicbox) (192.168.0.2) by gailleton-2-82-67-9-10.fbx.proxad.net with SMTP; 4 Aug 2004 17:50:56 +0200 Date: Wed, 04 Aug 2004 17:50:56 +0200 To: "Rod Taylor" , "Valerie Schneider DSI/DEV" Subject: Re: Tuning queries on large database Cc: "Postgresql Performance" References: <200408041244.i74CihO19344@mu.meteo.fr> <1091625999.58593.47.camel@jester> From: =?iso-8859-15?Q?Pierre-Fr=E9d=E9ric_Caillaud?= Organization: =?iso-8859-15?Q?La_Boutique_Num=E9rique?= Content-Type: text/plain; format=flowed; delsp=yes; charset=iso-8859-15 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID: In-Reply-To: <1091625999.58593.47.camel@jester> User-Agent: Opera M2/7.50 (Linux, build 673) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/55 X-Sequence-Number: 7691 >> not so bad for oracle. What about for PG ? How data is stored I agree with the datatype issue. Smallint, bigint, integer... add a constraint... Also the way order of the records in the database is very important. As you seem to have a very large static population in your table, you should insert it, ordered by your favourite selection index (looks like it's poste). Also, you have a lot of static data which pollutes your table. Why not create two tables, one for the current year, and one for all the past years. Use a view to present a merged view. From pgsql-performance-owner@postgresql.org Wed Aug 4 12:53:37 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 9CAE5D1B1AA for ; Wed, 4 Aug 2004 12:53:34 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 79334-07 for ; Wed, 4 Aug 2004 15:53:30 +0000 (GMT) Received: from boutiquenumerique.com (gailleton-2-82-67-9-10.fbx.proxad.net [82.67.9.10]) by svr1.postgresql.org (Postfix) with ESMTP id 322CBD1B1B4 for ; Wed, 4 Aug 2004 12:53:28 -0300 (ADT) Received: (qmail 5166 invoked from network); 4 Aug 2004 17:53:27 +0200 Received: from unknown (HELO musicbox) (192.168.0.2) by gailleton-2-82-67-9-10.fbx.proxad.net with SMTP; 4 Aug 2004 17:53:27 +0200 To: pgsql-performance@postgresql.org Subject: Re: Tuning queries on large database References: <200408041412.i74ECYO19577@mu.meteo.fr> Message-ID: Date: Wed, 04 Aug 2004 17:53:27 +0200 From: =?iso-8859-15?Q?Pierre-Fr=E9d=E9ric_Caillaud?= Organization: =?iso-8859-15?Q?La_Boutique_Num=E9rique?= Content-Type: text/plain; format=flowed; delsp=yes; charset=iso-8859-15 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In-Reply-To: <200408041412.i74ECYO19577@mu.meteo.fr> User-Agent: Opera M2/7.50 (Linux, build 673) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/56 X-Sequence-Number: 7692 You often make sums. Why not use separate tables to cache these sums by month, by poste, by whatever ? Rule on insert on the big table updates the cache tables. From pgsql-performance-owner@postgresql.org Wed Aug 4 12:56:49 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id AE42AD1B1C8 for ; Wed, 4 Aug 2004 12:56:47 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 79334-09 for ; Wed, 4 Aug 2004 15:56:42 +0000 (GMT) Received: from Herge.rcsinc.local (mail.rcsonline.com [205.217.85.91]) by svr1.postgresql.org (Postfix) with ESMTP id 45DE4D1B199 for ; Wed, 4 Aug 2004 12:56:40 -0300 (ADT) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: FW: Tuning queries on large database X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Date: Wed, 4 Aug 2004 11:56:41 -0400 Message-ID: <6EE64EF3AB31D5448D0007DD34EEB34101AF20@Herge.rcsinc.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] Tuning queries on large database thread-index: AcR6Iae9QRnQrjxYRJyInj9KrC3FYQAAOJgQAAY977A= From: "Merlin Moncure" To: "Postgresql Performance" X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/57 X-Sequence-Number: 7693 [forwarded to performance]=20 > The result is that for "short queries" (Q1 and Q2) it runs in a few > seconds on both Oracle and PG. The difference becomes important with > Q3 : 8 seconds with oracle > 80 sec with PG > and too much with Q4 : 28s with oracle > 17m20s with PG ! >=20 > Of course when I run 100 or 1000 parallel queries such as Q3 or Q4, > it becomes a disaster ! > I can't understand these results. The way to execute queries is the > same I think. I've read recommended articles on the PG site. > I tried with a table containing 30 millions rows, results are similar. I don't trust the Oracle #s. Lets look at Q4: returns 3 million rows. Using your #s of 160 fields and 256 bytes, your are asking for a result set of 160 * 256 * 3M =3D 12 GB! This data has to be gathered by the disk, assembled, and sent over the network. I don't know Oracle, but it probably has some 'smart' result set that uses a cursor behind the scenes to do the fetching. With a 3M row result set, you need to strongly consider using cursors. Try experimenting with the same query (Q4), declared as a cursor, and fetch the data in 10k blocks in a loop (fetch 10000), and watch the #s fly. Merlin From pgsql-performance-owner@postgresql.org Wed Aug 4 13:21:44 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id E2E0ED1B373 for ; Wed, 4 Aug 2004 13:21:40 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 87396-09 for ; Wed, 4 Aug 2004 16:21:36 +0000 (GMT) Received: from fep3.cogeco.net (smtp.cogeco.net [216.221.81.25]) by svr1.postgresql.org (Postfix) with ESMTP id 2DD5AD1B347 for ; Wed, 4 Aug 2004 13:21:34 -0300 (ADT) Received: from [127.0.0.1] (d226-86-215.home.cgocable.net [24.226.86.215]) by fep3.cogeco.net (Postfix) with ESMTP id AD16C2350; Wed, 4 Aug 2004 12:21:32 -0400 (EDT) Message-ID: <41110D06.5090900@ethereal-realms.org> Date: Wed, 04 Aug 2004 12:21:26 -0400 From: Martin Foster User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7) Gecko/20040616 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 To: Michael Adler Cc: PostgreSQL Performance Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <20040804153624.GA27551@pobox.com> In-Reply-To: <20040804153624.GA27551@pobox.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/58 X-Sequence-Number: 7694 Michael Adler wrote: > On Wed, Aug 04, 2004 at 03:49:11AM +0000, Martin Foster wrote: > >>Also note that some of these scripts run for longer durations even if >>they are web based. Some run as long as 30 minutes, making queries to >>the database from periods of wait from five seconds to twenty-five >>seconds. Under high duress the timeouts should back out, based on >>the time needed for the query to respond, normally averaging 0.008 seconds. > > > I would start by EXPLAIN ANALYZE'ing those 30 minute queries. > The Apache process will run for 30 minutes at a time, not the query itself. Essentially, while that process is running it will check for new records in the table at varying intervals, since it will increase timeouts based on load or lack of activity in order to reduce load to the database. > >>martin@io ~$ vmstat >> procs memory page disks faults cpu >> r b w avm fre flt re pi po fr sr ad4 ad6 in sy cs us sy id >> 0 0 0 498532 122848 3306 0 0 0 740 0 0 0 788 0 1675 16 21 63 >> > > > vmstat without a "delay" argument (e.g. 'vmstat 1') gives you a > cumulative or average since boot. You'd probably get better > information by doing a real-time sampling of stats during normal and > heavy load. > > >>martin@io ~$ ps -uax >>USER PID %CPU %MEM VSZ RSS TT STAT STARTED TIME COMMAND >>postgres 32084 0.0 0.2 91616 3764 p0- R Mon12PM 4:08.99 /usr/local/bin/postmaster -D /var/postgres (postgres) >>postgres 80333 0.0 2.1 94620 44372 ?? S 8:57PM 0:01.00 postmaster: ethereal ethereal 192.168.1.6 idle in trans >>postgres 80599 0.0 2.1 94652 44780 ?? S 8:59PM 0:00.97 postmaster: ethereal ethereal 192.168.1.6 idle in trans >>postgres 80616 0.0 2.4 94424 50396 ?? S 8:59PM 0:00.89 postmaster: ethereal ethereal 192.168.1.6 idle in trans >>postgres 80715 0.0 2.2 94444 46804 ?? S 9:00PM 0:00.68 postmaster: ethereal ethereal 192.168.1.6 idle in trans >>postgres 80788 0.0 2.1 94424 43944 ?? S 9:00PM 0:00.93 postmaster: ethereal ethereal 192.168.1.6 idle in trans >>postgres 80811 0.0 2.1 94424 43884 ?? S 9:00PM 0:00.94 postmaster: ethereal ethereal 192.168.1.6 idle in trans >>postgres 80902 0.0 2.1 94424 43380 ?? S 9:01PM 0:00.76 postmaster: ethereal ethereal 192.168.1.6 idle in trans >>postgres 80949 0.0 2.2 94424 45248 ?? S 9:01PM 0:00.67 postmaster: ethereal ethereal 192.168.1.6 idle in trans >>postgres 81020 0.0 2.1 94424 42924 ?? S 9:02PM 0:00.74 postmaster: ethereal ethereal 192.168.1.6 idle in trans > > > All the connections in your email are idle. You may benefit from using > pgpool instead of Apache::DBI (I've never tried). > > http://www.mail-archive.com/pgsql-announce@postgresql.org/msg00760.html > I will take a look into pgpool and see if it will serve as the solution I need. The pre-pooling of children sounds like a good choice, however since overhead is already a point of worry I almost wonder if I can host it on another server in order to drop that overhead on the servers directly. Anyone have experience with this on running it on the same machine or a different machine then the database proper? Of course, if this works as it should, I could easily put an older database server back into operation provided pgpool does weighted load balancing. Martin Foster Creator/Designer Ethereal Realms martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Wed Aug 4 13:37:15 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 10220D1B1D1 for ; Wed, 4 Aug 2004 13:37:13 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 92121-09 for ; Wed, 4 Aug 2004 16:36:59 +0000 (GMT) Received: from fep4.cogeco.net (smtp.cogeco.net [216.221.81.25]) by svr1.postgresql.org (Postfix) with ESMTP id 7EA69D1B19F for ; Wed, 4 Aug 2004 13:36:52 -0300 (ADT) Received: from [127.0.0.1] (d226-86-215.home.cgocable.net [24.226.86.215]) by fep4.cogeco.net (Postfix) with ESMTP id 37FA629EE; Wed, 4 Aug 2004 12:36:51 -0400 (EDT) Message-ID: <4111109D.7020006@ethereal-realms.org> Date: Wed, 04 Aug 2004 12:36:45 -0400 From: Martin Foster User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7) Gecko/20040616 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 To: Gaetano Mendola , PostgreSQL Performance Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> In-Reply-To: <4110FFF6.1030001@bigfoot.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/59 X-Sequence-Number: 7695 Gaetano Mendola wrote: > Martin Foster wrote: > >> Gaetano Mendola wrote: >> >>> Martin Foster wrote: >>> >>>> I run a Perl/CGI driven website that makes extensive use of >>>> PostgreSQL (7.4.3) for everything from user information to >>>> formatting and display of specific sections of the site. The >>>> server itself, is a dual processor AMD Opteron 1.4Ghz w/ 2GB Ram and >>>> 2 x 120GB hard drives mirrored for redundancy running under FreeBSD >>>> 5.2.1 (AMD64). >>>> >>>> Recently loads on the site have increased during peak hours to the >>>> point of showing considerable loss in performance. This can be >>>> observed when connections move from the 120 concurrent connections >>>> to PostgreSQL to roughly 175 or more. Essentially, the machine >>>> seems to struggle to keep up with continual requests and slows down >>>> respectively as resources are tied down. >>>> >>>> Code changes have been made to the scripts to essentially back off >>>> in high load working environments which have worked to an extent. >>>> However, as loads continue to increase the database itself is not >>>> taking well to the increased traffic taking place. >>>> >>>> Having taken a look at 'Tuning PostgreSQL for Performance' >>>> (http://www.varlena.com/GeneralBits/Tidbits/perf.html) using it as >>>> best I could in order to set my settings. However, even with >>>> statistics disabled and ever setting tweaked things still consider >>>> to deteriorate. >>>> >>>> Is there anything anyone can recommend in order to give the system a >>>> necessary speed boost? It would seem to me that a modest dataset >>>> of roughly a Gig combined with that type of hardware should be able >>>> to handle substantially more load then what it is. Can anyone >>>> provide me with clues as where to pursue? Would disabling 'fsync' >>>> provide more performance if I choose that information may be lost in >>>> case of a crash? >>>> >>>> If anyone needs access to logs, settings et cetera. Please ask, I >>>> simply wish to test the waters first on what is needed. Thanks! >>> >>> >>> >>> >>> Tell us about your tipical queries, show us your configuration file. >>> The access are only in read only mode or do you have concurrent writers >>> and readers ? During peak hours your processors are tied to 100% ? >>> What say the vmstat and the iostat ? >>> >>> May be you are not using indexes some where, or may be yes but the >>> planner is not using it... In two words we needs other informations >>> in order to help you. >>> >>> >>> >>> Regards >>> Gaetano Mendola >>> >>> >> >> I included all the files in attachments, which will hopefully cut down >> on any replied to Emails. As for things like connection pooling, >> the web server makes use of Apache::DBI to pool the connections for >> the Perl scripts being driven on that server. For the sake of being >> thorough, a quick 'apachectl status' was thrown in when the database >> was under a good load. > > > Let start from your postgres configuration: > > shared_buffers = 8192 <==== This is really too small for your > configuration > sort_mem = 2048 > > wal_buffers = 128 <==== This is really too small for your configuration > > effective_cache_size = 16000 > > change this values in: > > shared_buffers = 50000 > sort_mem = 16084 > > wal_buffers = 1500 > > effective_cache_size = 32000 > > > to bump up the shm usage you have to configure your OS in order to be > allowed to use that ammount of SHM. > > This are the numbers that I feel good for your HW, the second step now is > analyze your queries > >> The queries themselves are simple, normally drawing information from >> one table with few conditions or in the most complex cases using joins >> on two table or sub queries. These behave very well and always have, >> the problem is that these queries take place in rather large amounts >> due to the dumb nature of the scripts themselves. > > > Show us the explain analyze on that queries, how many rows the tables are > containing, the table schema could be also usefull. > > > > regards > Gaetano Mendola > I will look into moving up those values and seeing how they interact with the system once I get back from work. Since it was requested, I have a visual representation of an older schema, one that was used under MySQL. Note that all of the timestamps are now properly set to LOCALTIME on PostgreSQL. http://prdownloads.sourceforge.net/ethereal-realms/ethereal-3_0_0.png?download The amount of rows for tables of note are as follows: Puppeteer 1606 Puppet 33176 Realm 83 Post 36156 Audit 61961 The post table is continually cleared of old information since the nature of the information is time very critical and archiving would only hinder performance. As a result, this will vary wildly based on time of day since users (Puppeteers) tend to post more during peak hours. NOTE: The scripts make use of different schema's with the same information in order to virtualize the script in order to support more then one site on the same hardware. On a side note, this would be a normal post-authentication session once in realm for getting new posts: * Script is executed and schema is determined through stored procedure; * Formatting information is fetched from Tag and RealmDesign as needed; * Script will retrieve stored parameters in the Param table; * Script will decode, analyze and authenticate against Puppeteer; * Script will scan the Puppet and Post tables to generate posts; * Sub-query to determine ignored puppeteers/users; * Sub-query to determine ignored puppets/handles; and * Loop above if necessary until expiry of script delaying the execution of the script from 5 to 25 seconds. This should provide an idea on that portion. of course the flow changes when one posts, but is handled by a different script instance as is authentication et cetera. Martin Foster Creator/Designer Ethereal Realms martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Thu Aug 5 03:40:53 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 27E01D1B1CF for ; Thu, 5 Aug 2004 03:40:48 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 30737-07 for ; Thu, 5 Aug 2004 06:40:42 +0000 (GMT) Received: from boutiquenumerique.com (gailleton-2-82-67-9-10.fbx.proxad.net [82.67.9.10]) by svr1.postgresql.org (Postfix) with ESMTP id ADEC5D1B1A1 for ; Thu, 5 Aug 2004 03:40:34 -0300 (ADT) Received: (qmail 10793 invoked from network); 5 Aug 2004 08:40:33 +0200 Received: from unknown (HELO musicbox) (192.168.0.2) by gailleton-2-82-67-9-10.fbx.proxad.net with SMTP; 5 Aug 2004 08:40:33 +0200 To: "PostgreSQL Performance" Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <20040804153624.GA27551@pobox.com> <41110D06.5090900@ethereal-realms.org> Message-ID: Date: Thu, 05 Aug 2004 08:40:35 +0200 From: =?iso-8859-15?Q?Pierre-Fr=E9d=E9ric_Caillaud?= Organization: =?iso-8859-15?Q?La_Boutique_Num=E9rique?= Content-Type: text/plain; format=flowed; delsp=yes; charset=iso-8859-15 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In-Reply-To: <41110D06.5090900@ethereal-realms.org> User-Agent: Opera M2/7.50 (Linux, build 673) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/60 X-Sequence-Number: 7696 Apache processes running for 30 minutes ?..... My advice : use frames and Javascript ! In your webpage, you have two frames : "content" and "refresh". "content" starts empty (say, just a title on top of the page). "refresh" is refreshed every five seconds from a script on your server. This script generates a javascript which "document.write()'s" new entries in the "content" frame, thus adding new records in the upper frame. Thus, the refreshing uses a new request every 5 seconds, which terminates very fast, and does not hog an Apache process. Turn keepalive timeout down. From pgsql-performance-owner@postgresql.org Fri Aug 6 00:58:26 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id B2E4AD1B1AE for ; Thu, 5 Aug 2004 04:20:42 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 41865-08 for ; Thu, 5 Aug 2004 07:20:40 +0000 (GMT) Received: from main.gmane.org (main.gmane.org [80.91.224.249]) by svr1.postgresql.org (Postfix) with ESMTP id 56E1CD1B4AF for ; Thu, 5 Aug 2004 04:20:34 -0300 (ADT) Received: from root by main.gmane.org with local (Exim 3.35 #1 (Debian)) id 1BscYE-0005PA-00 for ; Thu, 05 Aug 2004 09:20:34 +0200 Received: from linuxnews.dk ([81.7.132.92]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 05 Aug 2004 09:20:33 +0200 Received: from jesper by linuxnews.dk with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 05 Aug 2004 09:20:33 +0200 X-Injected-Via-Gmane: http://gmane.org/ To: pgsql-performance@postgresql.org From: Jesper Krogh Subject: pg_dump performance? Date: Thu, 5 Aug 2004 07:08:48 +0000 (UTC) Lines: 16 Message-ID: X-Complaints-To: usenet@sea.gmane.org X-Gmane-NNTP-Posting-Host: linuxnews.dk User-Agent: slrn/0.9.8.0 (Linux) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/71 X-Sequence-Number: 7707 I have a database that I should migrate from 7.3 -> 7.4.3 but pg_dump | psql seems to take forever. (Several hours) Is there anything that can I do to speed it up? The databse is primary a table with 300.000 records of about 200Kbytes each. ~ 60 GB. This is becoming an issue with the daily backup too.. (running pg_dump over night ) Jesper -- ./Jesper Krogh, jesper@krogh.cc Jabber ID: jesper@jabbernet.dk From pgsql-performance-owner@postgresql.org Thu Aug 5 05:16:09 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3D801D1B4AF for ; Thu, 5 Aug 2004 05:16:07 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 56396-09 for ; Thu, 5 Aug 2004 08:16:07 +0000 (GMT) Received: from cadillac.meteo.fr (cadillac.meteo.fr [137.129.1.4]) by svr1.postgresql.org (Postfix) with ESMTP id 69DAED1B4EC for ; Thu, 5 Aug 2004 05:16:02 -0300 (ADT) Received: from mu.meteo.fr (localhost.meteo.fr [127.0.0.1]) by cadillac.meteo.fr (8.9.3 (PHNE_28760_binary)/8.9.3) with ESMTP id IAA00289; Thu, 5 Aug 2004 08:16:02 GMT Received: from mu.meteo.fr (mu.meteo.fr [137.129.6.129]) by mu.meteo.fr (8.11.7p1+Sun/8.11.7) with SMTP id i758GxO21560; Thu, 5 Aug 2004 08:16:59 GMT Message-Id: <200408050816.i758GxO21560@mu.meteo.fr> Date: Thu, 5 Aug 2004 08:16:59 +0000 (GMT) From: Valerie Schneider DSI/DEV Reply-To: Valerie Schneider DSI/DEV Subject: Re: [GENERAL] Tuning queries on large database To: chriskl@familyhealth.com.au Cc: pgsql-performance@postgresql.org MIME-Version: 1.0 Content-Type: TEXT/plain; charset=us-ascii Content-MD5: WW+nfrgJ7X6M2P6HcEvFOw== X-Mailer: dtmail 1.3.0 @(#)CDE Version 1.4.6_06 SunOS 5.8 sun4u sparc X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/61 X-Sequence-Number: 7697 Hi, I 've decreased the sort_mem to 5000 instead of 50000. I recreated ma table using integer and real types instead of numeric : the result is very improved for the disk space : schema | relfilenode | table | index | reltuples | size --------+-------------+------------------+------------+-------------+---------- public | 253442696 | data | | 1.25113e+08 | 29760016 public | 378639579 | data | i_data_dat | 1.25113e+08 | 2744400 public | 378555698 | data | pk_data | 1.25113e+08 | 3295584 so it takes about 28 Gb instead of 68 Gb ! For my different queries, it's better but less performant than oracle : oracle PG yesterday(numeric) PG today(integer/real) Q1 <1s <1s <1s Q2 3s 8s 4s Q3 8s 1m20s 27s Q4 28s 17m20s 6m47s Result of EXPLAIN ANALYZE : Q1 :bench=> explain analyze select 'Q1',min(td),max(u) from data where num_poste=1000 and dat between (date_trunc('month',to_timestamp('31012004','ddmmyyyy')-interval '2000 days'))::timestamp and (date_trunc('month',to_timestamp('31012004','ddmmyyyy')-interval '2000 days') + interval '1 month' - interval '1 hour')::timestamp; QUERY PLAN -------------------------------------------------------------------------------- Aggregate (cost=2466.47..2466.47 rows=1 width=8) (actual time=261.777..261.778 rows=1 loops=1) -> Index Scan using pk_data on data (cost=0.00..2463.41 rows=611 width=8) (actual time=20.106..259.924 rows=744 loops=1) Index Cond: ((num_poste = 1000) AND (dat >= (date_trunc('month'::text, (to_timestamp('31012004'::text, 'ddmmyyyy'::text) - '2000 days'::interval)))::timestamp without time zone) AND (dat <= (((date_trunc('month'::text, (to_timestamp('31012004'::text, 'ddmmyyyy'::text) - '2000 days'::interval)) + '1 mon'::interval) - '01:00:00'::interval))::timestamp without time zone)) Total runtime: 262.145 ms (4 rows) Q2 : bench=> explain analyze select 'Q2',count(*) from data where num_poste between 100 and 100+10 and dat between (date_trunc('month',to_timestamp('31012004','ddmmyyyy')-interval '3000 days'))::timestamp and (date_trunc('month',to_timestamp('31012004','ddmmyyyy')-interval '3000 days') + interval '1 month' - interval '1 hour')::timestamp; QUERY PLAN -------------------------------------------------------------------------------- Aggregate (cost=24777.68..24777.68 rows=1 width=0) (actual time=4253.977..4253.978 rows=1 loops=1) -> Index Scan using pk_data on data (cost=0.00..24762.34 rows=6138 width=0) (actual time=46.602..4244.984 rows=7920 loops=1) Index Cond: ((num_poste >= 100) AND (num_poste <= 110) AND (dat >= (date_trunc('month'::text, (to_timestamp('31012004'::text, 'ddmmyyyy'::text) - '3000 days'::interval)))::timestamp without time zone) AND (dat <= (((date_trunc('month'::text, (to_timestamp('31012004'::text, 'ddmmyyyy'::text) - '3000 days'::interval)) + '1 mon'::interval) - '01:00:00'::interval))::timestamp without time zone)) Total runtime: 4254.233 ms (4 rows) Q3 : bench=> explain analyze select 'Q3',sum(rr1),count(ff) from data where num_poste in (50,50+2); QUERY PLAN -------------------------------------------------------------------------------- Aggregate (cost=963455.87..963455.87 rows=1 width=8) (actual time=27668.666..27668.667 rows=1 loops=1) -> Index Scan using pk_data, pk_data on data (cost=0.00..962236.31 rows=243910 width=8) (actual time=16.251..27275.468 rows=250226 loops=1) Index Cond: ((num_poste = 50) OR (num_poste = 52)) Total runtime: 27673.837 ms (4 rows) Q4 : bench=> explain analyze select 'Q4',count(*) from data where num_poste between 600 and 625; QUERY PLAN -------------------------------------------------------------------------------- Aggregate (cost=14086174.57..14086174.57 rows=1 width=0) (actual time=428235.024..428235.025 rows=1 loops=1) -> Index Scan using pk_data on data (cost=0.00..14076910.99 rows=3705431 width=0) (actual time=45.283..424634.826 rows=3252938 loops=1) Index Cond: ((num_poste >= 600) AND (num_poste <= 625)) Total runtime: 428235.224 ms (4 rows) Thanks for all, Valerie. >X-Original-To: pgsql-general-postgresql.org@localhost.postgresql.org >X-Authentication-Warning: houston.familyhealth.com.au: chriskl owned process doing -bs >Date: Wed, 4 Aug 2004 21:21:51 +0800 (WST) >From: Christopher Kings-Lynne >To: Valerie Schneider DSI/DEV >Cc: pgsql-performance@postgresql.org, >Subject: Re: [GENERAL] [PERFORM] Tuning queries on large database >MIME-Version: 1.0 >X-Virus-Scanned: by amavisd-new at hub.org >X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= >X-Spam-Level: >X-Mailing-List: pgsql-general > >> sort_mem = 50000 > >That is way, way too large. Try more like 5000 or lower. > >> num_poste | numeric(9,0) | not null > >For starters numerics are really, really slow compared to integers. Why >aren't you using an integer for this field since youhave '0' decimal >places. > >> schema | relfilenode | table | index | reltuples | size >> --------+-------------+------------------+------------+-------------+---------- >> public | 125615917 | data | | 1.25113e+08 | 72312040 >> public | 251139049 | data | i_data_dat | 1.25113e+08 | 2744400 >> public | 250870177 | data | pk_data | 1.25113e+08 | 4395480 >> >> My first remark is that the table takes a lot of place on disk, about >> 70 Gb, instead of 35 Gb with oracle. > >Integers will take a lot less space than numerics. > >> The different queries of the bench are "simple" queries (no join, >> sub-query, ...) and are using indexes (I "explained" each one to >> be sure) : >> Q1 select_court : access to about 700 rows : 1 "num_poste" and 1 month >> (using PK : num_poste=p1 and dat between p2 and p3) >> Q2 select_moy : access to about 7000 rows : 10 "num_poste" and 1 month >> (using PK : num_poste between p1 and p1+10 and dat between p2 and p3) >> Q3 select_long : about 250 000 rows : 2 "num_poste" >> (using PK : num_poste in (p1,p1+2)) >> Q4 select_tres_long : about 3 millions rows : 25 "num_poste" >> (using PK : num_poste between p1 and p1 + 25) >> >> The result is that for "short queries" (Q1 and Q2) it runs in a few >> seconds on both Oracle and PG. The difference becomes important with >> Q3 : 8 seconds with oracle >> 80 sec with PG >> and too much with Q4 : 28s with oracle >> 17m20s with PG ! >> >> Of course when I run 100 or 1000 parallel queries such as Q3 or Q4, >> it becomes a disaster ! > >Please reply with the EXPLAIN ANALYZE output of these queries so we can >have some idea of how to help you. > >Chris > > > >---------------------------(end of broadcast)--------------------------- >TIP 5: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faqs/FAQ.html ******************************************************************** * Les points de vue exprimes sont strictement personnels et * * n'engagent pas la responsabilite de METEO-FRANCE. * ******************************************************************** * Valerie SCHNEIDER Tel : +33 (0)5 61 07 81 91 * * METEO-FRANCE / DSI/DEV Fax : +33 (0)5 61 07 81 09 * * 42, avenue G. Coriolis Email : Valerie.Schneider@meteo.fr * * 31057 TOULOUSE Cedex - FRANCE http://www.meteo.fr * ******************************************************************** From pgsql-performance-owner@postgresql.org Fri Aug 6 13:11:16 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 4ECB85E46C6 for ; Fri, 6 Aug 2004 13:11:14 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 14629-09 for ; Fri, 6 Aug 2004 16:11:16 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id A43255E46D0 for ; Fri, 6 Aug 2004 13:11:08 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i76GB65r081375 for ; Fri, 6 Aug 2004 16:11:16 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i76G1bLA080127 for pgsql-performance@postgresql.org; Fri, 6 Aug 2004 16:01:37 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: [GENERAL] Tuning queries on large database Date: Thu, 05 Aug 2004 11:53:59 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 36 Message-ID: <411203B7.8050706@bigfoot.com> References: <200408050816.i758GxO21560@mu.meteo.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: Valerie Schneider DSI/DEV User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: <200408050816.i758GxO21560@mu.meteo.fr> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/75 X-Sequence-Number: 7711 Valerie Schneider DSI/DEV wrote: > Hi, > I 've decreased the sort_mem to 5000 instead of 50000. > I recreated ma table using integer and real types instead of > numeric : the result is very improved for the disk space : > > schema | relfilenode | table | index | reltuples | size > --------+-------------+------------------+------------+-------------+---------- > public | 253442696 | data | | 1.25113e+08 | 29760016 > public | 378639579 | data | i_data_dat | 1.25113e+08 | 2744400 > public | 378555698 | data | pk_data | 1.25113e+08 | 3295584 > > so it takes about 28 Gb instead of 68 Gb ! > > For my different queries, it's better but less performant than oracle : > > oracle PG yesterday(numeric) PG today(integer/real) > Q1 <1s <1s <1s > Q2 3s 8s 4s > Q3 8s 1m20s 27s > Q4 28s 17m20s 6m47s Are you using the same disk for oracle and PG ? Could you post your actual postgresql.conf ? Try also to mount your partition with the option: noatime and try again. Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Thu Aug 5 07:07:40 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id E74DAD1B341 for ; Thu, 5 Aug 2004 07:07:37 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 87105-04 for ; Thu, 5 Aug 2004 10:07:38 +0000 (GMT) Received: from linda-1.paradise.net.nz (bm-1a.paradise.net.nz [202.0.58.20]) by svr1.postgresql.org (Postfix) with ESMTP id 87B6DD1B340 for ; Thu, 5 Aug 2004 07:07:34 -0300 (ADT) Received: from smtp-3.paradise.net.nz (smtp-3b.paradise.net.nz [202.0.32.212]) by linda-1.paradise.net.nz (Paradise.net.nz) with ESMTP id <0I1Y002VYXGM5Y@linda-1.paradise.net.nz> for pgsql-performance@postgresql.org; Thu, 05 Aug 2004 22:07:35 +1200 (NZST) Received: from coretech.co.nz (218-101-45-230.paradise.net.nz [218.101.45.230]) by smtp-3.paradise.net.nz (Postfix) with ESMTP id 15C28AE0F7; Thu, 05 Aug 2004 22:07:34 +1200 (NZST) Date: Thu, 05 Aug 2004 22:09:58 +1200 From: Mark Kirkwood Subject: Re: [GENERAL] Tuning queries on large database In-reply-to: <200408050816.i758GxO21560@mu.meteo.fr> To: Valerie Schneider DSI/DEV Cc: chriskl@familyhealth.com.au, pgsql-performance@postgresql.org Message-id: <41120776.4090401@coretech.co.nz> MIME-version: 1.0 Content-type: text/plain; format=flowed; charset=us-ascii Content-transfer-encoding: 7bit X-Accept-Language: en-us, en User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.6) Gecko/20040429 References: <200408050816.i758GxO21560@mu.meteo.fr> X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/62 X-Sequence-Number: 7698 I am guessing that Oracle can satisfy Q4 entirely via index access, whereas Pg has to visit the table as well. Having said that, a few partial indexes may be worth trying out on data.num_poste (say 10 or so), this won't help the table access but could lower the index cost. If you combine this with loading the data in num_poste order (or run CLUSTER), you may get closer to Oracle's time for this query. regards Mark Valerie Schneider DSI/DEV wrote: >For my different queries, it's better but less performant than oracle : > > oracle PG yesterday(numeric) PG today(integer/real) > >Q4 28s 17m20s 6m47s > > > >Q4 : bench=> explain analyze select 'Q4',count(*) from data where num_poste >between 600 and 625; > QUERY PLAN >-------------------------------------------------------------------------------- > Aggregate (cost=14086174.57..14086174.57 rows=1 width=0) (actual >time=428235.024..428235.025 rows=1 loops=1) > -> Index Scan using pk_data on data (cost=0.00..14076910.99 rows=3705431 >width=0) (actual time=45.283..424634.826 rows=3252938 loops=1) > Index Cond: ((num_poste >= 600) AND (num_poste <= 625)) > Total runtime: 428235.224 ms >(4 rows) > >Thanks for all, Valerie. > > > From pgsql-performance-owner@postgresql.org Thu Aug 5 10:08:27 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 27E2CD1B1C9 for ; Thu, 5 Aug 2004 10:08:26 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 44294-10 for ; Thu, 5 Aug 2004 13:08:20 +0000 (GMT) Received: from pns.mm.eutelsat.org (pns.mm.eutelsat.org [194.214.173.227]) by svr1.postgresql.org (Postfix) with ESMTP id E4080D1B171 for ; Thu, 5 Aug 2004 10:08:15 -0300 (ADT) Received: from nts-03.mm.eutelsat.org (localhost [127.0.0.1]) by pns.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i75D7s310555; Thu, 5 Aug 2004 15:07:54 +0200 Received: from [127.0.0.1] (accesspoint.mm.eutelsat.org [194.214.173.4]) by nts-03.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i75D8GZ01181; Thu, 5 Aug 2004 15:08:17 +0200 Message-ID: <4112311A.2050808@bigfoot.com> Date: Thu, 05 Aug 2004 15:07:38 +0200 From: Gaetano Mendola User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Valerie Schneider DSI/DEV Cc: "pgsql-performance@postgresql.org" Subject: Re: [GENERAL] Tuning queries on large database References: <200408051229.i75CTZO22267@mu.meteo.fr> In-Reply-To: <200408051229.i75CTZO22267@mu.meteo.fr> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/63 X-Sequence-Number: 7699 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Valerie Schneider DSI/DEV wrote: | #--------------------------------------------------------------------------- | # RESOURCE USAGE (except WAL) | #--------------------------------------------------------------------------- | | # - Memory - | | shared_buffers = 30000 # min 16, at least max_connections*2, 8KB each | #sort_mem = 1024 # min 64, size in KB | sort_mem = 5000 # min 64, size in KB | #vacuum_mem = 8192 # min 1024, size in KB | | # - Free Space Map - | | #max_fsm_pages = 20000 # min max_fsm_relations*16, 6 bytes each | #max_fsm_relations = 1000 # min 100, ~50 bytes each | | # - Kernel Resource Usage - | | #max_files_per_process = 1000 # min 25 | #preload_libraries = '' | | | #--------------------------------------------------------------------------- | # WRITE AHEAD LOG | #--------------------------------------------------------------------------- | | # - Settings - | | #fsync = true # turns forced synchronization on or off | #wal_sync_method = fsync # the default varies across platforms: | # fsync, fdatasync, open_sync, or open_datasync | #wal_buffers = 8 # min 4, 8KB each | | # - Checkpoints - | | #checkpoint_segments = 3 # in logfile segments, min 1, 16MB each | checkpoint_segments = 30 # in logfile segments, min 1, 16MB each | #checkpoint_timeout = 300 # range 30-3600, in seconds | #checkpoint_warning = 30 # 0 is off, in seconds | #commit_delay = 0 # range 0-100000, in microseconds | #commit_siblings = 5 # range 1-1000 | | | #--------------------------------------------------------------------------- | # QUERY TUNING | #--------------------------------------------------------------------------- | | # - Planner Method Enabling - | | #enable_hashagg = true | #enable_hashjoin = true | #enable_indexscan = true | #enable_mergejoin = true | #enable_nestloop = true | enable_seqscan = false | #enable_sort = true | #enable_tidscan = true | | # - Planner Cost Constants - | | #effective_cache_size = 1000 # typically 8KB each | effective_cache_size = 200000 # typically 8KB each | #random_page_cost = 4 # units are one sequential page fetch cost | random_page_cost = 2 # units are one sequential page fetch cost | #cpu_tuple_cost = 0.01 # (same) | #cpu_index_tuple_cost = 0.001 # (same) | #cpu_operator_cost = 0.0025 # (same) | | # - Genetic Query Optimizer - | | #geqo = true | #geqo_threshold = 11 | #geqo_effort = 1 | #geqo_generations = 0 | #geqo_pool_size = 0 # default based on tables in statement, | # range 128-1024 | #geqo_selection_bias = 2.0 # range 1.5-2.0 Your wal_buffers is too small try do bump up your wal_buffers to ~3000, and see the effects. why did you disable the sequential_scan (see later) ? Try also to lower the cpu_costs: cpu_tuple_cost = 0.005 cpu_index_tuple_cost = 0.0005 # (same) cpu_operator_cost = 0.0005 # (same) this will push the optimizer to choose the index scans. If not show us the explain with enable_seqscan = false and with enable_seqscan = true *Mount also your partition with the noatime parameter* Regards Gaeatano Mendola -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (MingW32) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFBEjEY7UpzwH2SGd4RAtxnAKDuTtYZvWMXL7zjHWU20VFtm2V1OACg/Y1l GZuQ5RviMB2nB4M8G6PW17U= =HxGz -----END PGP SIGNATURE----- From pgsql-performance-owner@postgresql.org Thu Aug 5 10:18:53 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 902C8D1B229 for ; Thu, 5 Aug 2004 10:18:49 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 47793-07 for ; Thu, 5 Aug 2004 13:18:50 +0000 (GMT) Received: from tht.net (vista.tht.net [216.126.88.2]) by svr1.postgresql.org (Postfix) with ESMTP id 08043D1B171 for ; Thu, 5 Aug 2004 10:18:45 -0300 (ADT) Received: from [134.22.68.4] (dyn-68-4.tor.dsl.tht.net [134.22.68.4]) by tht.net (Postfix) with ESMTP id 3787976AF2; Thu, 5 Aug 2004 09:18:50 -0400 (EDT) Subject: Re: [GENERAL] Tuning queries on large database From: Rod Taylor To: Valerie Schneider DSI/DEV Cc: Christopher Kings-Lynne , Postgresql Performance In-Reply-To: <200408050816.i758GxO21560@mu.meteo.fr> References: <200408050816.i758GxO21560@mu.meteo.fr> Content-Type: text/plain Message-Id: <1091711927.84496.22.camel@jester> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Thu, 05 Aug 2004 09:18:47 -0400 Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/64 X-Sequence-Number: 7700 > so it takes about 28 Gb instead of 68 Gb ! Huzzah! > For my different queries, it's better but less performant than oracle : Not surprising. Oracle has a number of optimizations that we don't have implemented at this point, particularly where aggregates are involved. One that PG could use, particularly for Q4, is the ability to execute a selective sequential scan based on a read of the index -- right now it pulls in actual data from the table structure while following the index -- creates unnecessary disk-head movement. The only solution to that, at the moment, is to cluster the table by pk_data. I am curious though, could you run the below query on both systems and report back times? select 'Q4', * from data where num_poste between 600 and 625; I'm wondering if Oracle is using a shortcut since the count(*) doesn't actually require the data -- just knowledge of whether a matching row exists or not. From pgsql-performance-owner@postgresql.org Thu Aug 5 10:21:45 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 311BAD1B171 for ; Thu, 5 Aug 2004 10:21:44 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 49336-09 for ; Thu, 5 Aug 2004 13:21:38 +0000 (GMT) Received: from Herge.rcsinc.local (mail.rcsonline.com [205.217.85.91]) by svr1.postgresql.org (Postfix) with ESMTP id D47D5D1B1B4 for ; Thu, 5 Aug 2004 10:21:33 -0300 (ADT) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: Re: [GENERAL] Tuning queries on large database X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Date: Thu, 5 Aug 2004 09:20:17 -0400 Message-ID: <6EE64EF3AB31D5448D0007DD34EEB34101AF21@Herge.rcsinc.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] [GENERAL] Tuning queries on large database thread-index: AcR67dZHMvHa/6IsTO2AHzTsoIutawAAIlTw From: "Merlin Moncure" To: "Valerie Schneider DSI/DEV" Cc: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/65 X-Sequence-Number: 7701 Another question: How are you benchmarking your queries? Are you running them from within psql? Do you plan to run these queries from within an application? psql introduces some overhead because it has to scan the result set to determine the widths of the columns for formatting purposes. Try returning a result set inside the libpq library if you know C and compare the times. Of course, if you are already using libpq, this moot. If you do know libpq, try setting up a loop that fetches the data in 10k block in a loop...I will wager that you can get this to run in under two minutes (Q4). Merlin From pgsql-performance-owner@postgresql.org Thu Aug 5 10:26:28 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id ECDE2D1B373 for ; Thu, 5 Aug 2004 10:26:26 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 51732-07 for ; Thu, 5 Aug 2004 13:26:29 +0000 (GMT) Received: from Herge.rcsinc.local (mail.rcsonline.com [205.217.85.91]) by svr1.postgresql.org (Postfix) with ESMTP id 2EBCDD1B1D5 for ; Thu, 5 Aug 2004 10:26:24 -0300 (ADT) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: Re: [GENERAL] Tuning queries on large database X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Date: Thu, 5 Aug 2004 09:26:29 -0400 Message-ID: <6EE64EF3AB31D5448D0007DD34EEB34101AF22@Herge.rcsinc.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] [GENERAL] Tuning queries on large database thread-index: AcR67dZHMvHa/6IsTO2AHzTsoIutawAAIlTwAABWfSA= From: "Merlin Moncure" To: "Valerie Schneider DSI/DEV" Cc: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/66 X-Sequence-Number: 7702 I wrote:=20 > Another question: > How are you benchmarking your queries? Are you running them from within > psql? Do you plan to run these queries from within an application? >=20 > psql introduces some overhead because it has to scan the result set to > determine the widths of the columns for formatting purposes. Try > returning a result set inside the libpq library if you know C and compare > the times. Of course, if you are already using libpq, this moot. If you > do know libpq, try setting up a loop that fetches the data in 10k block in > a loop...I will wager that you can get this to run in under two minutes > (Q4). Whoop, didn't see the aggregate...sorry :) Merlin From pgsql-admin-owner@postgresql.org Thu Aug 5 11:33:28 2004 X-Original-To: pgsql-admin-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id F4060D1B275; Thu, 5 Aug 2004 11:33:21 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 73305-06; Thu, 5 Aug 2004 14:33:23 +0000 (GMT) Received: from tino.sinectis.com.ar (tino.sinectis.com.ar [216.244.192.232]) by svr1.postgresql.org (Postfix) with ESMTP id B1F15D1B171; Thu, 5 Aug 2004 11:33:17 -0300 (ADT) Received: by tino.sinectis.com.ar (Postfix, from userid 99) id 70E4A6C695; Thu, 5 Aug 2004 11:33:20 -0300 (GMT+3) Content-Type: text/plain Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 X-Mailer: Sinectis Webmail 5.6.16-1.5.1 From: G u i d o B a r o s i o To: pgsql-performance@postgresql.org Subject: Temporary tables Cc: pgsql-admin@postgresql.org Reply-To: gbarosio@uolsinectis.com.ar Message-Id: <20040805143320.70E4A6C695@tino.sinectis.com.ar> Date: Thu, 5 Aug 2004 11:33:20 -0300 (GMT+3) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/22 X-Sequence-Number: 14417 The box: Linux 2.4.24-ck1 8 Intel(R) Xeon(TM) MP CPU 2.80GHz 4 gb RAM. Postgresql 7.4.2 The problem: Short in disk space. (waiting new hard) The real problem: Developers usually write queries involving the creation of temporary tables. The BF question: Is a good idea to link this tmp tables to another partition? If so, how can I link this tmp tables to another partition? Suggestions? Thanks in advance! Guido From pgsql-performance-owner@postgresql.org Thu Aug 5 12:04:13 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 02D9DD1B1C9 for ; Thu, 5 Aug 2004 12:04:11 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 81403-10 for ; Thu, 5 Aug 2004 15:04:07 +0000 (GMT) Received: from trofast.sesse.net (trofast.sesse.net [129.241.93.32]) by svr1.postgresql.org (Postfix) with ESMTP id C18DFD1B17A for ; Thu, 5 Aug 2004 12:04:05 -0300 (ADT) Received: from sesse by trofast.sesse.net with local (Exim 3.36 #1 (Debian)) id 1Bsjml-0003Px-00 for ; Thu, 05 Aug 2004 17:04:03 +0200 Date: Thu, 5 Aug 2004 17:04:03 +0200 From: "Steinar H. Gunderson" To: pgsql-performance@postgresql.org Subject: Re: Performance Bottleneck Message-ID: <20040805150403.GA13056@uio.no> References: <410FDC53.5080509@bigfoot.com> <20040804153624.GA27551@pobox.com> <41110D06.5090900@ethereal-realms.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Operating-System: Linux 2.6.6 on a i686 User-Agent: Mutt/1.5.6+20040722i X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/68 X-Sequence-Number: 7704 On Thu, Aug 05, 2004 at 08:40:35AM +0200, Pierre-Fr�d�ric Caillaud wrote: > Apache processes running for 30 minutes ?..... > > My advice : use frames and Javascript ! My advice: Stay out of frames and Javascript if you can avoid it. The first is severely outdated technology, and the other one might well be disabled at the client side. /* Steinar */ -- Homepage: http://www.sesse.net/ From pgsql-performance-owner@postgresql.org Fri Aug 6 13:11:17 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 6DC7D5E46C7 for ; Fri, 6 Aug 2004 13:11:14 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 13919-09 for ; Fri, 6 Aug 2004 16:11:16 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 9152F5E46C5 for ; Fri, 6 Aug 2004 13:11:08 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i76GB65p081375 for ; Fri, 6 Aug 2004 16:11:13 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i76G1iS3080137 for pgsql-performance@postgresql.org; Fri, 6 Aug 2004 16:01:44 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Temporary tables Date: Thu, 05 Aug 2004 17:37:50 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 30 Message-ID: <4112544E.2060706@bigfoot.com> References: <20040805143320.70E4A6C695@tino.sinectis.com.ar> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: G u i d o B a r o s i o User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: <20040805143320.70E4A6C695@tino.sinectis.com.ar> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/76 X-Sequence-Number: 7712 G u i d o B a r o s i o wrote: > The box: > Linux 2.4.24-ck1 > 8 Intel(R) Xeon(TM) MP CPU 2.80GHz > 4 gb RAM. > Postgresql 7.4.2 > > The problem: > Short in disk space. (waiting new hard) > > The real problem: > Developers usually write queries involving the creation of temporary tables. I seen too this behavior, till I explained that this is a valid sql: select T.* from ( select * from table t where a = 5 ) AS T join foo using ( bar ); show us a typical function that use temporary tables. Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Thu Aug 5 12:42:10 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id BB980D1B341 for ; Thu, 5 Aug 2004 12:42:08 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 97944-02 for ; Thu, 5 Aug 2004 15:42:04 +0000 (GMT) Received: from sardegna.mbigroup.it (ns1.mbigroup.it [213.188.200.195]) by svr1.postgresql.org (Postfix) with ESMTP id 290F6D1B229 for ; Thu, 5 Aug 2004 12:41:58 -0300 (ADT) Received: from mailserver.bo.mbigroup.it (localhost.localdomain [127.0.0.1]) by sardegna.mbigroup.it (8.12.10/8.12.10) with ESMTP id i75FfuPM030689; Thu, 5 Aug 2004 17:41:56 +0200 Received: from [127.0.0.1] (acasula.dev.mbigroup.it [192.168.21.15]) by mailserver.bo.mbigroup.it (8.11.6/8.11.6) with ESMTP id i75Fd0909402; Thu, 5 Aug 2004 17:39:00 +0200 Message-ID: <41125519.9090907@bigfoot.com> Date: Thu, 05 Aug 2004 17:41:13 +0200 From: Gaetano Mendola User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: G u i d o B a r o s i o , "pgsql-performance@postgresql.org" Subject: Re: Temporary tables References: <20040805143320.70E4A6C695@tino.sinectis.com.ar> In-Reply-To: <20040805143320.70E4A6C695@tino.sinectis.com.ar> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.3 tagged_above=0.0 required=5.0 tests=UPPERCASE_25_50 X-Spam-Level: X-Archive-Number: 200408/69 X-Sequence-Number: 7705 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 G u i d o B a r o s i o wrote: | The box: | Linux 2.4.24-ck1 | 8 Intel(R) Xeon(TM) MP CPU 2.80GHz | 4 gb RAM. | Postgresql 7.4.2 | | The problem: | Short in disk space. (waiting new hard) | | The real problem: | Developers usually write queries involving the creation of temporary tables. I seen too this behavior, till I explained that this is a valid sql: select T.* from ( select * from table t where a = 5 ) AS T join foo using ( bar ); show us a typical function that use temporary tables. Regards Gaetano Mendola -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (MingW32) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD4DBQFBElSx7UpzwH2SGd4RAhnkAKDABtA1fZSCCF/WAP5TUBJnHdWHYACWLjjQ LgncGg4+b0lPCQbafXVG6w== =1f1i -----END PGP SIGNATURE----- From pgsql-performance-owner@postgresql.org Mon Aug 9 00:06:33 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id C632E14B287A for ; Mon, 9 Aug 2004 00:05:16 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 43184-08 for ; Mon, 9 Aug 2004 03:05:11 +0000 (GMT) Received: from ganymede.hub.org (u46n208.hfx.eastlink.ca [24.222.46.208]) by svr1.postgresql.org (Postfix) with ESMTP id 49B5F14B28BB for ; Mon, 9 Aug 2004 00:04:45 -0300 (ADT) Received: by ganymede.hub.org (Postfix, from userid 1000) id 3755934E91; Mon, 9 Aug 2004 00:04:37 -0300 (ADT) Received: from localhost (localhost [127.0.0.1]) by ganymede.hub.org (Postfix) with ESMTP id 31286346BC for ; Mon, 9 Aug 2004 00:04:37 -0300 (ADT) X-Return-Path: X-Received: from localhost ([unix socket]) by ganymede.hub.org (Cyrus v2.2.6) with LMTPA; Thu, 05 Aug 2004 15:13:37 -0300 X-Sieve: CMU Sieve 2.2 X-Received: from localhost (localhost.hub.org [127.0.0.1]) by ganymede.hub.org (Postfix) with ESMTP id B5D783CBC0 for ; Thu, 5 Aug 2004 15:11:15 -0300 (ADT) X-Received: from mail.postgresql.org [200.46.204.71] by localhost with IMAP (fetchmail-6.2.5) for scrappy@localhost (single-drop); Thu, 05 Aug 2004 15:11:15 -0300 (ADT) X-Received: from svr1.postgresql.org ([unix socket]) by svr1.postgresql.org (Cyrus v2.2.6) with LMTPA; Thu, 05 Aug 2004 15:10:09 -0300 X-Sieve: CMU Sieve 2.2 X-Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id ED4D2D1B252 for ; Thu, 5 Aug 2004 15:10:08 -0300 (ADT) X-Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 44853-06 for ; Thu, 5 Aug 2004 18:10:06 +0000 (GMT) X-Received: from mproxy.gmail.com (rproxy.gmail.com [64.233.170.193]) by svr1.postgresql.org (Postfix) with ESMTP id 5D8EED1B1C9 for ; Thu, 5 Aug 2004 15:10:02 -0300 (ADT) X-Received: by mproxy.gmail.com with SMTP id 73so18212rnk for ; Thu, 05 Aug 2004 11:10:01 -0700 (PDT) X-Received: by 10.38.9.22 with SMTP id 22mr62172rni; Thu, 05 Aug 2004 11:10:01 -0700 (PDT) Message-ID: <5cfdfaf7040805111013a769af@mail.gmail.com> Date: Thu, 5 Aug 2004 13:10:01 -0500 From: Jim Thomason Reply-To: jim@jimandkoka.com To: psql-performance@postgresql.org Subject: performance with column orders Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-DCC: : X-Spam-Pyzor: ReSent-Date: Mon, 9 Aug 2004 00:04:31 -0300 (ADT) Resent-From: "Marc G. Fournier" Resent-To: pgsql-performance@postgresql.org ReSent-Subject: performance with column orders ReSent-Message-ID: <20040809000431.L52647@ganymede.hub.org> X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/109 X-Sequence-Number: 7745 I couldn't track down recent info in the archives, so I figured I'd ask here. Does the order of columns still have an impact on table speed? Back in the olden days, it used to be that fixed width columns (integer, tinyint, etc.) should be the first ("left") columns in the table and variable width ones should be towards the end ("right"). This allowed a database to line up the columns better on disk and give you a speed boost. So, does Postgres still care about it? And, if so, how much? The posts I found were from 2 years ago, and indicated that there is a minor increase, but not a lot. Incidentally, could anyone quantify that in any fashion? Thanks, -Jim.... From pgsql-performance-owner@postgresql.org Fri Aug 6 01:43:21 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id D671E5E38A9 for ; Fri, 6 Aug 2004 01:43:09 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 31726-08 for ; Fri, 6 Aug 2004 04:43:10 +0000 (GMT) Received: from houston.familyhealth.com.au (fhnet.arach.net.au [203.22.197.21]) by svr1.postgresql.org (Postfix) with ESMTP id 3A9415E3AB5 for ; Fri, 6 Aug 2004 01:42:49 -0300 (ADT) Received: from [192.168.0.40] (work-40.internal [192.168.0.40]) by houston.familyhealth.com.au (8.12.9p1/8.12.9) with ESMTP id i764geUi012228; Fri, 6 Aug 2004 12:42:41 +0800 (WST) (envelope-from chriskl@familyhealth.com.au) Message-ID: <41130D16.7030902@familyhealth.com.au> Date: Fri, 06 Aug 2004 12:46:14 +0800 From: Christopher Kings-Lynne User-Agent: Mozilla Thunderbird 0.7.3 (Windows/20040803) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Jesper Krogh Cc: pgsql-performance@postgresql.org Subject: Re: pg_dump performance? References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/72 X-Sequence-Number: 7708 Is it the dump or the restore that's really slow? Chris Jesper Krogh wrote: > I have a database that I should migrate from 7.3 -> 7.4.3 but pg_dump | > psql seems to take forever. (Several hours) Is there anything that can I > do to speed it up? > > The databse is primary a table with 300.000 records of about 200Kbytes > each. ~ 60 GB. > > This is becoming an issue with the daily backup too.. (running pg_dump > over night ) > > Jesper > From pgsql-performance-owner@postgresql.org Fri Aug 6 02:05:22 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 893085E3AB3 for ; Fri, 6 Aug 2004 02:05:20 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 39828-05 for ; Fri, 6 Aug 2004 05:05:17 +0000 (GMT) Received: from main.gmane.org (main.gmane.org [80.91.224.249]) by svr1.postgresql.org (Postfix) with ESMTP id C61995E38A9 for ; Fri, 6 Aug 2004 02:05:15 -0300 (ADT) Received: from list by main.gmane.org with local (Exim 3.35 #1 (Debian)) id 1Bswul-0006Q3-00 for ; Fri, 06 Aug 2004 07:05:13 +0200 Received: from linuxnews.dk ([81.7.132.92]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 06 Aug 2004 07:05:11 +0200 Received: from jesper by linuxnews.dk with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 06 Aug 2004 07:05:11 +0200 X-Injected-Via-Gmane: http://gmane.org/ To: pgsql-performance@postgresql.org From: Jesper Krogh Subject: Re: pg_dump performance? Date: Fri, 6 Aug 2004 05:05:08 +0000 (UTC) Lines: 11 Message-ID: References: <41130D16.7030902@familyhealth.com.au> X-Complaints-To: usenet@sea.gmane.org X-Gmane-NNTP-Posting-Host: linuxnews.dk User-Agent: slrn/0.9.8.0 (Linux) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/73 X-Sequence-Number: 7709 I gmane.comp.db.postgresql.performance, skrev Christopher Kings-Lynne: > Is it the dump or the restore that's really slow? Primarily the dump, it seems to be CPU-bound on the postmaster' process. No signs on IO-bottleneck when I try to monitor with iostat or vmstat -- ./Jesper Krogh, jesper@krogh.cc Jabber ID: jesper@jabbernet.dk From pgsql-performance-owner@postgresql.org Fri Aug 6 13:30:02 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id AA3595E46C6 for ; Fri, 6 Aug 2004 13:30:00 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 21616-09 for ; Fri, 6 Aug 2004 16:30:03 +0000 (GMT) Received: from davinci.ethosmedia.com (server226.ethosmedia.com [209.128.84.226]) by svr1.postgresql.org (Postfix) with ESMTP id D061A5E40BA for ; Fri, 6 Aug 2004 13:29:54 -0300 (ADT) Received: from [63.195.55.98] (HELO spooky) by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 6006894; Fri, 06 Aug 2004 09:31:16 -0700 Content-Type: text/plain; charset="iso-8859-1" From: Josh Berkus Organization: Aglio Database Solutions To: Gaetano Mendola , Paul Serby Subject: Re: The black art of postgresql.conf tweaking Date: Fri, 6 Aug 2004 09:29:19 -0700 User-Agent: KMail/1.4.3 References: <4110DA83.7020505@clockltd.com> <411100EC.8010802@bigfoot.com> In-Reply-To: <411100EC.8010802@bigfoot.com> Cc: pgsql-performance@postgresql.org MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <200408060929.19840.josh@agliodbs.com> X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/79 X-Sequence-Number: 7715 Paul, > > Physical Memory: 2077264 kB > > sort_mem = 12000 Hmmm. Someone may already have mentioned this, but that looks problematic. You're allowing up to 12MB per sort, and up to 300 connections. Even if each concurrent connection averages only one sort (and they can use more) that's 3600MB ... roughly 1.5 times your *total* RAM, leaving out RAM for Apache, postmaster, shared buffers, etc. I strongly suggest that you either decrease your total connections or your sort_mem, or both. -- Josh Berkus Aglio Database Solutions San Francisco From pgsql-performance-owner@postgresql.org Fri Aug 6 14:07:38 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 823F05E46C5 for ; Fri, 6 Aug 2004 14:07:37 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 35170-07 for ; Fri, 6 Aug 2004 17:07:27 +0000 (GMT) Received: from mail.academyoflearning.ca (s64-180-138-192.bc.hsia.telus.net [64.180.138.192]) by svr1.postgresql.org (Postfix) with ESMTP id B62B25E46C0 for ; Fri, 6 Aug 2004 14:07:22 -0300 (ADT) Received: from [192.168.1.10] (d216-232-247-236.bchsia.telus.net [216.232.247.236]) (using SSLv3 with cipher RC4-MD5 (128/128 bits)) (No client certificate requested) by mail.academyoflearning.ca (Postfix) with ESMTP id 6899E34DBC; Fri, 6 Aug 2004 10:06:53 -0700 (PDT) Subject: Re: Performance Bottleneck From: Mike Benoit To: Gaetano Mendola Cc: pgsql-performance@postgresql.org In-Reply-To: <4110FFF6.1030001@bigfoot.com> References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> Content-Type: text/plain Date: Fri, 06 Aug 2004 10:06:51 -0700 Message-Id: <1091812011.7149.25.camel@ipso.snappymail.ca> Mime-Version: 1.0 X-Mailer: Evolution 1.5.91-2mdk Content-Transfer-Encoding: 7bit X-snappymail-MailScanner-Information: Please contact the ISP for more information X-snappymail-MailScanner: Found to be clean X-snappymail-MailScanner-SpamCheck: not spam, SpamAssassin (score=1.911, required 5, AWL -0.79, RCVD_IN_DYNABLOCK 2.60, RCVD_IN_SORBS 0.10) X-snappymail-MailScanner-SpamScore: s X-MailScanner-From: ipso@snappymail.ca X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/80 X-Sequence-Number: 7716 On Wed, 2004-08-04 at 17:25 +0200, Gaetano Mendola wrote: > > The queries themselves are simple, normally drawing information from one > > table with few conditions or in the most complex cases using joins on > > two table or sub queries. These behave very well and always have, the > > problem is that these queries take place in rather large amounts due to > > the dumb nature of the scripts themselves. > > Show us the explain analyze on that queries, how many rows the tables are > containing, the table schema could be also usefull. > If the queries themselves are optimized as much as they can be, and as you say, its just the sheer amount of similar queries hitting the database, you could try using prepared queries for ones that are most often executed to eliminate some of the overhead. I've had relatively good success with this in the past, and it doesn't take very much code modification. -- Mike Benoit From pgsql-performance-owner@postgresql.org Fri Aug 6 15:30:52 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 93F8F5E46EA for ; Fri, 6 Aug 2004 15:27:53 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 67333-06 for ; Fri, 6 Aug 2004 18:27:51 +0000 (GMT) Received: from pns.mm.eutelsat.org (pns.mm.eutelsat.org [194.214.173.227]) by svr1.postgresql.org (Postfix) with ESMTP id 574AD5E46E7 for ; Fri, 6 Aug 2004 15:27:47 -0300 (ADT) Received: from nts-03.mm.eutelsat.org (localhost [127.0.0.1]) by pns.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i76IRHe18249; Fri, 6 Aug 2004 20:27:18 +0200 Received: from [127.0.0.1] (accesspoint.mm.eutelsat.org [194.214.173.4]) by nts-03.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i76IRgZ06997; Fri, 6 Aug 2004 20:27:42 +0200 Message-ID: <4113CD75.2060508@bigfoot.com> Date: Fri, 06 Aug 2004 20:27:01 +0200 From: Gaetano Mendola User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Josh Berkus Cc: Paul Serby , pgsql-performance@postgresql.org Subject: Re: The black art of postgresql.conf tweaking References: <4110DA83.7020505@clockltd.com> <411100EC.8010802@bigfoot.com> <200408060929.19840.josh@agliodbs.com> In-Reply-To: <200408060929.19840.josh@agliodbs.com> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/81 X-Sequence-Number: 7717 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Josh Berkus wrote: | Paul, | | |>>Physical Memory: 2077264 kB | | |>>sort_mem = 12000 | | | Hmmm. Someone may already have mentioned this, but that looks problematic. | You're allowing up to 12MB per sort, and up to 300 connections. Even if each | concurrent connection averages only one sort (and they can use more) that's | 3600MB ... roughly 1.5 times your *total* RAM, leaving out RAM for Apache, | postmaster, shared buffers, etc. | | I strongly suggest that you either decrease your total connections or your | sort_mem, or both. Of course your are speaking about the "worst case", I aplly in scenarios like this on the rule 80/20: 80% of connection will perform a sort and 20% will allocate memory for the sort operation in the same window time: 300 -- 80% --> 240 --> 20% --> 48 48 * 12MB = 576 MB that seems resonable with the total ammount of memory available. Am I too optimistic? Regards Gaetano Mendola -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (MingW32) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFBE81z7UpzwH2SGd4RAuzzAJ98Ze0HQedKaZ/laT7P1OS44FG0CwCfaWkY MAR1TEY1+x61PoXjK/K8Q4Y= =8UmF -----END PGP SIGNATURE----- From pgsql-performance-owner@postgresql.org Fri Aug 6 20:01:31 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id CB4935E3AC5 for ; Fri, 6 Aug 2004 19:58:41 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 45471-06 for ; Fri, 6 Aug 2004 22:58:36 +0000 (GMT) Received: from fep3.cogeco.net (smtp.cogeco.net [216.221.81.25]) by svr1.postgresql.org (Postfix) with ESMTP id AD7815E46C5 for ; Fri, 6 Aug 2004 19:58:31 -0300 (ADT) Received: from [127.0.0.1] (d226-86-215.home.cgocable.net [24.226.86.215]) by fep3.cogeco.net (Postfix) with ESMTP id 08C902F0A; Fri, 6 Aug 2004 18:58:35 -0400 (EDT) Message-ID: <41140D17.7070101@ethereal-realms.org> Date: Fri, 06 Aug 2004 18:58:31 -0400 From: Martin Foster User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 To: Gaetano Mendola , PostgreSQL Performance Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> In-Reply-To: <4110FFF6.1030001@bigfoot.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/82 X-Sequence-Number: 7718 Gaetano Mendola wrote: > > > Let start from your postgres configuration: > > shared_buffers = 8192 <==== This is really too small for your > configuration > sort_mem = 2048 > > wal_buffers = 128 <==== This is really too small for your configuration > > effective_cache_size = 16000 > > change this values in: > > shared_buffers = 50000 > sort_mem = 16084 > > wal_buffers = 1500 > > effective_cache_size = 32000 > > > to bump up the shm usage you have to configure your OS in order to be > allowed to use that ammount of SHM. > > This are the numbers that I feel good for your HW, the second step now is > analyze your queries > These changes have yielded some visible improvements, with load averages rarely going over the anything noticeable. However, I do have a question on the matter, why do these values seem to be far higher then what a frequently pointed to document would indicate as necessary? http://www.varlena.com/GeneralBits/Tidbits/perf.html I am simply curious, as this clearly shows that my understanding of PostgreSQL is clearly lacking when it comes to tweaking for the hardware. Martin Foster Creator/Designer Ethereal Realms martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Fri Aug 6 20:19:35 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 715DB5E46C0 for ; Fri, 6 Aug 2004 20:18:18 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 49496-08 for ; Fri, 6 Aug 2004 23:18:20 +0000 (GMT) Received: from davinci.ethosmedia.com (server226.ethosmedia.com [209.128.84.226]) by svr1.postgresql.org (Postfix) with ESMTP id 57D835E46D3 for ; Fri, 6 Aug 2004 20:18:15 -0300 (ADT) Received: from [64.81.245.111] (HELO temoku.sf.agliodbs.com) by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 6012012; Fri, 06 Aug 2004 16:19:34 -0700 From: Josh Berkus Reply-To: josh@agliodbs.com Organization: Aglio Database Solutions To: Gaetano Mendola Subject: Re: The black art of postgresql.conf tweaking Date: Fri, 6 Aug 2004 16:18:40 -0700 User-Agent: KMail/1.5.4 Cc: Paul Serby , pgsql-performance@postgresql.org References: <4110DA83.7020505@clockltd.com> <200408060929.19840.josh@agliodbs.com> <4113CD75.2060508@bigfoot.com> In-Reply-To: <4113CD75.2060508@bigfoot.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200408061618.40047.josh@agliodbs.com> X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/83 X-Sequence-Number: 7719 Gaetano, > Of course your are speaking about the "worst case", I aplly in scenarios like > this on the rule 80/20: 80% of connection will perform a sort and 20% will allocate > memory for the sort operation in the same window time: Well, I suppose it depends on how aggresive your connection pooling is. If you minimize idle connections, then 300 connections can mean 200 concurrent queries. And since Paul *is* having problems, this is worth looking into. -- -Josh Berkus Aglio Database Solutions San Francisco From pgsql-performance-owner@postgresql.org Fri Aug 6 20:30:37 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 4661C5E46C0 for ; Fri, 6 Aug 2004 20:30:13 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 52483-09 for ; Fri, 6 Aug 2004 23:30:08 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 5C6BC5E3AC5 for ; Fri, 6 Aug 2004 20:30:03 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i76NU4Sp015840 for ; Fri, 6 Aug 2004 23:30:04 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i76NIk0p015224 for pgsql-performance@postgresql.org; Fri, 6 Aug 2004 23:18:46 GMT From: Martin Foster User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <1091812011.7149.25.camel@ipso.snappymail.ca> In-Reply-To: <1091812011.7149.25.camel@ipso.snappymail.ca> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Lines: 81 Message-ID: Date: Fri, 06 Aug 2004 23:18:49 GMT To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/84 X-Sequence-Number: 7720 Mike Benoit wrote: > On Wed, 2004-08-04 at 17:25 +0200, Gaetano Mendola wrote: > > >>>The queries themselves are simple, normally drawing information from one >>>table with few conditions or in the most complex cases using joins on >>>two table or sub queries. These behave very well and always have, the >>>problem is that these queries take place in rather large amounts due to >>>the dumb nature of the scripts themselves. >> >>Show us the explain analyze on that queries, how many rows the tables are >>containing, the table schema could be also usefull. >> > > > If the queries themselves are optimized as much as they can be, and as > you say, its just the sheer amount of similar queries hitting the > database, you could try using prepared queries for ones that are most > often executed to eliminate some of the overhead. > > I've had relatively good success with this in the past, and it doesn't > take very much code modification. > One of the biggest problems is most probably related to the indexes. Since the performance penalty of logging the information needed to see which queries are used and which are not is a slight problem, then I cannot really make use of it for now. However, I am curious how one would go about preparing query? Is this similar to the DBI::Prepare statement with placeholders and simply changing the values passed on execute? Or is this something database level such as a view et cetera? SELECT Post.PostIDNumber, Post.$format, Post.PuppeteerLogin, Post.PuppetName, Post.PostCmd, Post.PostClass FROM Post WHERE Post.PostIDNumber > ?::INT AND (Post.PostTo='all' OR Post.PostTo=?) AND (NOT EXISTS (SELECT PuppetIgnore.PuppetLogin FROM PuppetIgnore WHERE PuppetIgnore.PuppetIgnore='global' AND PuppetIgnore.PuppeteerLogin=? AND PuppetIgnore.PuppetLogin=Post.PuppeteerLogin) OR Post.PuppeteerLogin IS NULL) AND (NOT EXISTS (SELECT PuppetIgnore.PuppetName FROM PuppetIgnore WHERE PuppetIgnore.PuppetIgnore='single' AND PuppetIgnore.PuppeteerLogin=? AND PuppetIgnore.PuppetName=Post.PuppetName) OR Post.PuppetName IS NULL) ORDER BY Post.PostIDNumber LIMIT 100 The range is determined from the previous run or through a query listed below. It was determined that using INT was far faster then limiting by timestamp. SELECT MIN(PostIDNumber) FROM Post WHERE RealmName=? AND PostClass IN ('general','play') AND PostTo='all' The above simply provides a starting point, nothing more. Once posts are pulled the script will throw in the last pulled number as to start from a fresh point. Under MySQL time was an stored as an INT which may have helped it handle timestamps more efficiently. It also made use of three or more queries, where two were done to generate an IN statement for the query actually running at the time. Martin Foster Creator/Designer Ethereal Realms martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Fri Aug 6 20:30:46 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 075E85E46C7 for ; Fri, 6 Aug 2004 20:30:16 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 54834-02 for ; Fri, 6 Aug 2004 23:30:08 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 5C8ED5E3F15 for ; Fri, 6 Aug 2004 20:30:03 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i76NU4Sv015840 for ; Fri, 6 Aug 2004 23:30:04 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i76NOqHa015597 for pgsql-performance@postgresql.org; Fri, 6 Aug 2004 23:24:52 GMT From: Gaetano Mendola X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Performance Bottleneck Date: Sat, 07 Aug 2004 01:24:18 +0200 Organization: PYRENET Midi-pyrenees Provider Lines: 65 Message-ID: <41141322.3010200@bigfoot.com> References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <41140D17.7070101@ethereal-realms.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@pyrenet.fr To: Martin Foster User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en In-Reply-To: <41140D17.7070101@ethereal-realms.org> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/85 X-Sequence-Number: 7721 Martin Foster wrote: > Gaetano Mendola wrote: > >> >> >> Let start from your postgres configuration: >> >> shared_buffers = 8192 <==== This is really too small for your >> configuration >> sort_mem = 2048 >> >> wal_buffers = 128 <==== This is really too small for your >> configuration >> >> effective_cache_size = 16000 >> >> change this values in: >> >> shared_buffers = 50000 >> sort_mem = 16084 >> >> wal_buffers = 1500 >> >> effective_cache_size = 32000 >> >> >> to bump up the shm usage you have to configure your OS in order to be >> allowed to use that ammount of SHM. >> >> This are the numbers that I feel good for your HW, the second step now is >> analyze your queries >> > > These changes have yielded some visible improvements, with load averages > rarely going over the anything noticeable. However, I do have a > question on the matter, why do these values seem to be far higher then > what a frequently pointed to document would indicate as necessary? > > http://www.varlena.com/GeneralBits/Tidbits/perf.html > > I am simply curious, as this clearly shows that my understanding of > PostgreSQL is clearly lacking when it comes to tweaking for the hardware. Unfortunately there is no a "wizard tuning" for postgres so each one of us have a own "school". The data I gave you are oversized to be sure to achieve improvements. Now you can start to decrease these values ( starting from the wal_buffers ) in order to find the good compromise with your HW. Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Fri Aug 6 20:43:07 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 03CC45E46D8 for ; Fri, 6 Aug 2004 20:42:11 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 58183-02 for ; Fri, 6 Aug 2004 23:42:13 +0000 (GMT) Received: from pns.mm.eutelsat.org (pns.mm.eutelsat.org [194.214.173.227]) by svr1.postgresql.org (Postfix) with ESMTP id 2057B5E4699 for ; Fri, 6 Aug 2004 20:42:08 -0300 (ADT) Received: from nts-03.mm.eutelsat.org (localhost [127.0.0.1]) by pns.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i76Nfk019452; Sat, 7 Aug 2004 01:41:46 +0200 Received: from [127.0.0.1] (accesspoint.mm.eutelsat.org [194.214.173.4]) by nts-03.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i76NgAZ08004; Sat, 7 Aug 2004 01:42:10 +0200 Message-ID: <41141728.1050608@bigfoot.com> Date: Sat, 07 Aug 2004 01:41:28 +0200 From: Gaetano Mendola User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Josh Berkus , "pgsql-performance@postgresql.org" Subject: Re: The black art of postgresql.conf tweaking References: <4110DA83.7020505@clockltd.com> <200408060929.19840.josh@agliodbs.com> <4113CD75.2060508@bigfoot.com> <200408061618.40047.josh@agliodbs.com> In-Reply-To: <200408061618.40047.josh@agliodbs.com> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/86 X-Sequence-Number: 7722 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Josh Berkus wrote: | Gaetano, | | |>Of course your are speaking about the "worst case", I aplly in scenarios | | like | |>this on the rule 80/20: 80% of connection will perform a sort and 20% will | | allocate | |>memory for the sort operation in the same window time: | | | Well, I suppose it depends on how aggresive your connection pooling is. If | you minimize idle connections, then 300 connections can mean 200 concurrent | queries. And since Paul *is* having problems, this is worth looking into. With 4 CPU ( like Paul have ) there is a lot of space in order to have 200 concurrent connection running but I don't believe that all 200 togheter are allocating space for sort, I have not seen the code but I'm quite confident that the memory for sort is released as soon the sort operation is over, not at the end of connection. Regards Gaetano Mendola -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (MingW32) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFBFBcn7UpzwH2SGd4RAuNhAJ0f+NVUlRUszX+gUE6EfYiFYQy5JQCgnaRj HcguR1U3CgvQiZ4a56PBtVU= =6Jzo -----END PGP SIGNATURE----- From pgsql-performance-owner@postgresql.org Fri Aug 6 21:01:39 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3CF345E4699 for ; Fri, 6 Aug 2004 21:00:33 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 60800-08 for ; Sat, 7 Aug 2004 00:00:35 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id 721895E4249 for ; Fri, 6 Aug 2004 21:00:29 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.12.11/8.12.11) with ESMTP id i7700LLt024610; Fri, 6 Aug 2004 20:00:21 -0400 (EDT) To: Martin Foster Cc: Gaetano Mendola , PostgreSQL Performance Subject: Re: Performance Bottleneck In-reply-to: <41140D17.7070101@ethereal-realms.org> References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <41140D17.7070101@ethereal-realms.org> Comments: In-reply-to Martin Foster message dated "Fri, 06 Aug 2004 18:58:31 -0400" Date: Fri, 06 Aug 2004 20:00:21 -0400 Message-ID: <24609.1091836821@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/87 X-Sequence-Number: 7723 Martin Foster writes: > Gaetano Mendola wrote: >> change this values in: >> shared_buffers = 50000 >> sort_mem = 16084 >> >> wal_buffers = 1500 This value of wal_buffers is simply ridiculous. There isn't any reason to set wal_buffers higher than the amount of WAL log data that will be generated by a single transaction, because whatever is in the buffers will be flushed at transaction commit. If you are mainly dealing with heavy concurrency then it's the mean time between transaction commits that matters, and that's even less than the average transaction length. Even if you are mainly interested in the performance of large updating transactions that are not concurrent with anything else (bulk data load, perhaps), I'm not sure that I see any value in setting wal_buffers so high. The data will have to go to disk before commit in any case, and buffering so much of it just means that you are going to have a serious spike in disk traffic right before commit. It's almost certainly better to keep wal_buffers conservatively small and let the data trickle out as the transaction proceeds. I don't actually think there is anything very wrong with the default value (8) ... perhaps it is too small, but it's not two orders of magnitude too small. In 8.0, the presence of the background writer may make it useful to run with wal_buffers somewhat higher than before, but I still doubt that order-of-a-thousand buffers would be useful. The RAM would almost certainly be better spent on general-purpose disk buffers or kernel cache. Note though that this is just informed opinion, as I've never done or seen any benchmarks that examine the results of changing wal_buffers while holding other things constant. Has anyone tried it? regards, tom lane From pgsql-performance-owner@postgresql.org Fri Aug 6 21:30:16 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 6BE0B5E3E30 for ; Fri, 6 Aug 2004 21:28:46 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 68710-02 for ; Sat, 7 Aug 2004 00:28:40 +0000 (GMT) Received: from hotmail.com (bay7-f23.bay7.hotmail.com [64.4.11.23]) by svr1.postgresql.org (Postfix) with ESMTP id E5D025E3AC5 for ; Fri, 6 Aug 2004 21:28:34 -0300 (ADT) Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Fri, 6 Aug 2004 17:28:39 -0700 Received: from 200.24.104.55 by by7fd.bay7.hotmail.msn.com with HTTP; Sat, 07 Aug 2004 00:28:38 GMT X-Originating-IP: [200.24.104.55] X-Originating-Email: [mileruiz@hotmail.com] X-Sender: mileruiz@hotmail.com From: "sandra ruiz" To: pgsql-performance@postgresql.org Subject: Question about Generating Possible Plans by the planner/optimizer Date: Fri, 06 Aug 2004 19:28:38 -0500 Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Message-ID: X-OriginalArrivalTime: 07 Aug 2004 00:28:39.0193 (UTC) FILETIME=[7C214890:01C47C15] X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/88 X-Sequence-Number: 7724 in the docummentation about the planer it says: "It first combines all possible ways of scanning and joining the relations that appear in a query" I would like to know if there's a time limit to do that or if it just scans ALL the posibilities until it finishes..no matter the time it takes.. thanks in advance. _________________________________________________________________ MSN Amor: busca tu � naranja http://latam.msn.com/amor/ From pgsql-performance-owner@postgresql.org Fri Aug 6 21:56:00 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 24AF35E40BB for ; Fri, 6 Aug 2004 21:55:01 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 74995-02 for ; Sat, 7 Aug 2004 00:54:56 +0000 (GMT) Received: from mpls-qmqp-04.inet.qwest.net (mpls-qmqp-04.inet.qwest.net [63.231.195.115]) by svr1.postgresql.org (Postfix) with SMTP id 509F85E4248 for ; Fri, 6 Aug 2004 21:54:50 -0300 (ADT) Received: (qmail 30662 invoked by uid 0); 7 Aug 2004 00:54:55 -0000 Received: from mpls-pop-04.inet.qwest.net (63.231.195.4) by mpls-qmqp-04.inet.qwest.net with QMQP; 7 Aug 2004 00:54:55 -0000 Received: from 63-227-127-37.dnvr.qwest.net (HELO ?10.0.0.2?) (63.227.127.37) by mpls-pop-04.inet.qwest.net with SMTP; 7 Aug 2004 00:54:55 -0000 Date: Fri, 06 Aug 2004 18:56:18 -0600 Message-Id: <1091840178.27166.255.camel@localhost.localdomain> From: "Scott Marlowe" To: "Gaetano Mendola" Cc: "Martin Foster" , pgsql-performance@postgresql.org Subject: Re: Performance Bottleneck In-Reply-To: <41141322.3010200@bigfoot.com> References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <41140D17.7070101@ethereal-realms.org> <41141322.3010200@bigfoot.com> Content-Type: text/plain Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/89 X-Sequence-Number: 7725 On Fri, 2004-08-06 at 17:24, Gaetano Mendola wrote: > Martin Foster wrote: > > > Gaetano Mendola wrote: > > > >> > >> > >> Let start from your postgres configuration: > >> > >> shared_buffers = 8192 <==== This is really too small for your > >> configuration > >> sort_mem = 2048 > >> > >> wal_buffers = 128 <==== This is really too small for your > >> configuration > >> > >> effective_cache_size = 16000 > >> > >> change this values in: > >> > >> shared_buffers = 50000 > >> sort_mem = 16084 > >> > >> wal_buffers = 1500 > >> > >> effective_cache_size = 32000 > >> > >> > >> to bump up the shm usage you have to configure your OS in order to be > >> allowed to use that ammount of SHM. > >> > >> This are the numbers that I feel good for your HW, the second step now is > >> analyze your queries > >> > > > > These changes have yielded some visible improvements, with load averages > > rarely going over the anything noticeable. However, I do have a > > question on the matter, why do these values seem to be far higher then > > what a frequently pointed to document would indicate as necessary? > > > > http://www.varlena.com/GeneralBits/Tidbits/perf.html > > > > I am simply curious, as this clearly shows that my understanding of > > PostgreSQL is clearly lacking when it comes to tweaking for the hardware. > > Unfortunately there is no a "wizard tuning" for postgres so each one of > us have a own "school". The data I gave you are oversized to be sure > to achieve improvements. Now you can start to decrease these values > ( starting from the wal_buffers ) in order to find the good compromise > with your HW. FYI, my school of tuning is to change one thing at a time some reasonable percentage (shared_buffers from 1000 to 2000) and measure the change under simulated load. Make another change, test it, chart the shape of the change line. It should look something like this for most folks: shared_buffers | q/s (more is better) 100 | 20 200 | 45 400 | 80 1000 | 100 ... levels out here... 8000 | 110 10000 | 108 20000 | 40 30000 | 20 Note it going back down as we exceed our memory and start swapping shared_buffers. Where that happens on your machine is determined by many things like your machine's memory, memory bandwidth, type of load, etc... but it will happen on most machines and when it does, it often happens at the worst times, under heavy parallel load. Unless testing shows it's faster, 10000 or 25% of mem (whichever is less) is usually a pretty good setting for shared_buffers. Large data sets may require more than 10000, but going over 25% on machines with large memory is usually a mistake, especially servers that do anything other than just PostgreSQL. You're absolutely right about one thing, there's no automatic wizard for tuning this stuff. From pgsql-performance-owner@postgresql.org Fri Aug 6 22:13:38 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 9797F5E46CA for ; Fri, 6 Aug 2004 22:12:02 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 78664-04 for ; Sat, 7 Aug 2004 01:11:53 +0000 (GMT) Received: from trofast.sesse.net (trofast.sesse.net [129.241.93.32]) by svr1.postgresql.org (Postfix) with ESMTP id F21B95E40BB for ; Fri, 6 Aug 2004 22:11:44 -0300 (ADT) Received: from sesse by trofast.sesse.net with local (Exim 3.36 #1 (Debian)) id 1BtFkS-0001k1-00 for ; Sat, 07 Aug 2004 03:11:48 +0200 Date: Sat, 7 Aug 2004 03:11:48 +0200 From: "Steinar H. Gunderson" To: pgsql-performance@postgresql.org Subject: Re: Question about Generating Possible Plans by the planner/optimizer Message-ID: <20040807011148.GA6617@uio.no> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: Linux 2.6.6 on a i686 User-Agent: Mutt/1.5.6+20040722i X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/90 X-Sequence-Number: 7726 On Fri, Aug 06, 2004 at 07:28:38PM -0500, sandra ruiz wrote: > in the docummentation about the planer it says: > > "It first combines all possible ways of scanning and joining the relations > that appear in a query" > > I would like to know if there's a time limit to do that or if it just scans > ALL the posibilities until it finishes..no matter the time it takes.. Depends; if you join a lot of tables, it stops doing an exhaustive search and goes for genetic optimization instead: http://www.postgresql.org/docs/7.4/static/geqo.html /* Steinar */ -- Homepage: http://www.sesse.net/ From pgsql-performance-owner@postgresql.org Sat Aug 7 01:13:15 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id DF6B75E4077 for ; Sat, 7 Aug 2004 01:10:08 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 23393-04 for ; Sat, 7 Aug 2004 04:10:14 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 2EB405E3F15 for ; Sat, 7 Aug 2004 01:10:05 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i774ABiG089171 for ; Sat, 7 Aug 2004 04:10:11 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i7742wmc088371 for pgsql-performance@postgresql.org; Sat, 7 Aug 2004 04:02:58 GMT From: Martin Foster User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <41140D17.7070101@ethereal-realms.org> <41141322.3010200@bigfoot.com> <1091840178.27166.255.camel@localhost.localdomain> In-Reply-To: <1091840178.27166.255.camel@localhost.localdomain> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Lines: 97 Message-ID: Date: Sat, 07 Aug 2004 04:02:58 GMT To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/91 X-Sequence-Number: 7727 Scott Marlowe wrote: > On Fri, 2004-08-06 at 17:24, Gaetano Mendola wrote: > >>Martin Foster wrote: >> >> >>>Gaetano Mendola wrote: >>> >>> >>>> >>>>Let start from your postgres configuration: >>>> >>>>shared_buffers = 8192 <==== This is really too small for your >>>>configuration >>>>sort_mem = 2048 >>>> >>>>wal_buffers = 128 <==== This is really too small for your >>>>configuration >>>> >>>>effective_cache_size = 16000 >>>> >>>>change this values in: >>>> >>>>shared_buffers = 50000 >>>>sort_mem = 16084 >>>> >>>>wal_buffers = 1500 >>>> >>>>effective_cache_size = 32000 >>>> >>>> >>>>to bump up the shm usage you have to configure your OS in order to be >>>>allowed to use that ammount of SHM. >>>> >>>>This are the numbers that I feel good for your HW, the second step now is >>>>analyze your queries >>>> >>> >>>These changes have yielded some visible improvements, with load averages >>>rarely going over the anything noticeable. However, I do have a >>>question on the matter, why do these values seem to be far higher then >>>what a frequently pointed to document would indicate as necessary? >>> >>>http://www.varlena.com/GeneralBits/Tidbits/perf.html >>> >>>I am simply curious, as this clearly shows that my understanding of >>>PostgreSQL is clearly lacking when it comes to tweaking for the hardware. >> >>Unfortunately there is no a "wizard tuning" for postgres so each one of >>us have a own "school". The data I gave you are oversized to be sure >>to achieve improvements. Now you can start to decrease these values >>( starting from the wal_buffers ) in order to find the good compromise >>with your HW. > > > FYI, my school of tuning is to change one thing at a time some > reasonable percentage (shared_buffers from 1000 to 2000) and measure the > change under simulated load. Make another change, test it, chart the > shape of the change line. It should look something like this for most > folks: > > shared_buffers | q/s (more is better) > 100 | 20 > 200 | 45 > 400 | 80 > 1000 | 100 > ... levels out here... > 8000 | 110 > 10000 | 108 > 20000 | 40 > 30000 | 20 > > Note it going back down as we exceed our memory and start swapping > shared_buffers. Where that happens on your machine is determined by > many things like your machine's memory, memory bandwidth, type of load, > etc... but it will happen on most machines and when it does, it often > happens at the worst times, under heavy parallel load. > > Unless testing shows it's faster, 10000 or 25% of mem (whichever is > less) is usually a pretty good setting for shared_buffers. Large data > sets may require more than 10000, but going over 25% on machines with > large memory is usually a mistake, especially servers that do anything > other than just PostgreSQL. > > You're absolutely right about one thing, there's no automatic wizard for > tuning this stuff. > Which rather points out the crux of the problem. This is a live system, meaning changes made need to be as informed as possible, and that changing values for the sake of testing can lead to potential problems in service. Martin Foster Creator/Designer Ethereal Realms martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Sat Aug 7 01:38:00 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 0C7C55E4075 for ; Sat, 7 Aug 2004 01:34:45 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 29299-05 for ; Sat, 7 Aug 2004 04:34:52 +0000 (GMT) Received: from mpls-qmqp-03.inet.qwest.net (mpls-qmqp-03.inet.qwest.net [63.231.195.114]) by svr1.postgresql.org (Postfix) with SMTP id 9FD855E46BF for ; Sat, 7 Aug 2004 01:34:42 -0300 (ADT) Received: (qmail 25435 invoked by uid 0); 7 Aug 2004 04:03:10 -0000 Received: from mpls-pop-03.inet.qwest.net (63.231.195.3) by mpls-qmqp-03.inet.qwest.net with QMQP; 7 Aug 2004 04:03:10 -0000 Received: from 63-227-127-37.dnvr.qwest.net (HELO ?10.0.0.2?) (63.227.127.37) by mpls-pop-03.inet.qwest.net with SMTP; 7 Aug 2004 04:34:49 -0000 Date: Fri, 06 Aug 2004 22:36:13 -0600 Message-Id: <1091853373.27166.260.camel@localhost.localdomain> From: "Scott Marlowe" To: "Martin Foster" Cc: pgsql-performance@postgresql.org Subject: Re: Performance Bottleneck In-Reply-To: References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <41140D17.7070101@ethereal-realms.org> <41141322.3010200@bigfoot.com> <1091840178.27166.255.camel@localhost.localdomain> Content-Type: text/plain Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/92 X-Sequence-Number: 7728 On Fri, 2004-08-06 at 22:02, Martin Foster wrote: > Scott Marlowe wrote: > > > On Fri, 2004-08-06 at 17:24, Gaetano Mendola wrote: > > > >>Martin Foster wrote: > >> > >> > >>>Gaetano Mendola wrote: > >>> > >>> > >>>> > >>>>Let start from your postgres configuration: > >>>> > >>>>shared_buffers = 8192 <==== This is really too small for your > >>>>configuration > >>>>sort_mem = 2048 > >>>> > >>>>wal_buffers = 128 <==== This is really too small for your > >>>>configuration > >>>> > >>>>effective_cache_size = 16000 > >>>> > >>>>change this values in: > >>>> > >>>>shared_buffers = 50000 > >>>>sort_mem = 16084 > >>>> > >>>>wal_buffers = 1500 > >>>> > >>>>effective_cache_size = 32000 > >>>> > >>>> > >>>>to bump up the shm usage you have to configure your OS in order to be > >>>>allowed to use that ammount of SHM. > >>>> > >>>>This are the numbers that I feel good for your HW, the second step now is > >>>>analyze your queries > >>>> > >>> > >>>These changes have yielded some visible improvements, with load averages > >>>rarely going over the anything noticeable. However, I do have a > >>>question on the matter, why do these values seem to be far higher then > >>>what a frequently pointed to document would indicate as necessary? > >>> > >>>http://www.varlena.com/GeneralBits/Tidbits/perf.html > >>> > >>>I am simply curious, as this clearly shows that my understanding of > >>>PostgreSQL is clearly lacking when it comes to tweaking for the hardware. > >> > >>Unfortunately there is no a "wizard tuning" for postgres so each one of > >>us have a own "school". The data I gave you are oversized to be sure > >>to achieve improvements. Now you can start to decrease these values > >>( starting from the wal_buffers ) in order to find the good compromise > >>with your HW. > > > > > > FYI, my school of tuning is to change one thing at a time some > > reasonable percentage (shared_buffers from 1000 to 2000) and measure the > > change under simulated load. Make another change, test it, chart the > > shape of the change line. It should look something like this for most > > folks: > > > > shared_buffers | q/s (more is better) > > 100 | 20 > > 200 | 45 > > 400 | 80 > > 1000 | 100 > > ... levels out here... > > 8000 | 110 > > 10000 | 108 > > 20000 | 40 > > 30000 | 20 > > > > Note it going back down as we exceed our memory and start swapping > > shared_buffers. Where that happens on your machine is determined by > > many things like your machine's memory, memory bandwidth, type of load, > > etc... but it will happen on most machines and when it does, it often > > happens at the worst times, under heavy parallel load. > > > > Unless testing shows it's faster, 10000 or 25% of mem (whichever is > > less) is usually a pretty good setting for shared_buffers. Large data > > sets may require more than 10000, but going over 25% on machines with > > large memory is usually a mistake, especially servers that do anything > > other than just PostgreSQL. > > > > You're absolutely right about one thing, there's no automatic wizard for > > tuning this stuff. > > > > Which rather points out the crux of the problem. This is a live system, > meaning changes made need to be as informed as possible, and that > changing values for the sake of testing can lead to potential problems > in service. But if you make those changes slowly, as I was showing, you should see the small deleterious effects like I was showing long before they become catastrophic. To just jump shared_buffers to 50000 is not a good idea, especially if the sweet spot is likely lower than that. From pgsql-performance-owner@postgresql.org Sat Aug 7 01:45:21 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 688715E40AC for ; Sat, 7 Aug 2004 01:39:35 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 28577-10 for ; Sat, 7 Aug 2004 04:39:39 +0000 (GMT) Received: from fep7.cogeco.net (smtp.cogeco.net [216.221.81.25]) by svr1.postgresql.org (Postfix) with ESMTP id 859DB5E4077 for ; Sat, 7 Aug 2004 01:39:29 -0300 (ADT) Received: from [127.0.0.1] (d226-86-215.home.cgocable.net [24.226.86.215]) by fep7.cogeco.net (Postfix) with ESMTP id 883C221D8; Sat, 7 Aug 2004 00:39:37 -0400 (EDT) Message-ID: <41145D07.90006@ethereal-realms.org> Date: Sat, 07 Aug 2004 00:39:35 -0400 From: Martin Foster Organization: Ethereal Realms User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 To: Scott Marlowe , PostgreSQL Performance Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <41140D17.7070101@ethereal-realms.org> <41141322.3010200@bigfoot.com> <1091840178.27166.255.camel@localhost.localdomain> <1091853373.27166.260.camel@localhost.localdomain> In-Reply-To: <1091853373.27166.260.camel@localhost.localdomain> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/93 X-Sequence-Number: 7729 Scott Marlowe wrote: > On Fri, 2004-08-06 at 22:02, Martin Foster wrote: > >>Scott Marlowe wrote: >> >> >>>On Fri, 2004-08-06 at 17:24, Gaetano Mendola wrote: >>> >>> >>>>Martin Foster wrote: >>>> >>>> >>>> >>>>>Gaetano Mendola wrote: >>>>> >>>>> >>>>> >>>>>>Let start from your postgres configuration: >>>>>> >>>>>>shared_buffers = 8192 <==== This is really too small for your >>>>>>configuration >>>>>>sort_mem = 2048 >>>>>> >>>>>>wal_buffers = 128 <==== This is really too small for your >>>>>>configuration >>>>>> >>>>>>effective_cache_size = 16000 >>>>>> >>>>>>change this values in: >>>>>> >>>>>>shared_buffers = 50000 >>>>>>sort_mem = 16084 >>>>>> >>>>>>wal_buffers = 1500 >>>>>> >>>>>>effective_cache_size = 32000 >>>>>> >>>>>> >>>>>>to bump up the shm usage you have to configure your OS in order to be >>>>>>allowed to use that ammount of SHM. >>>>>> >>>>>>This are the numbers that I feel good for your HW, the second step now is >>>>>>analyze your queries >>>>>> >>>>> >>>>>These changes have yielded some visible improvements, with load averages >>>>>rarely going over the anything noticeable. However, I do have a >>>>>question on the matter, why do these values seem to be far higher then >>>>>what a frequently pointed to document would indicate as necessary? >>>>> >>>>>http://www.varlena.com/GeneralBits/Tidbits/perf.html >>>>> >>>>>I am simply curious, as this clearly shows that my understanding of >>>>>PostgreSQL is clearly lacking when it comes to tweaking for the hardware. >>>> >>>>Unfortunately there is no a "wizard tuning" for postgres so each one of >>>>us have a own "school". The data I gave you are oversized to be sure >>>>to achieve improvements. Now you can start to decrease these values >>>>( starting from the wal_buffers ) in order to find the good compromise >>>>with your HW. >>> >>> >>>FYI, my school of tuning is to change one thing at a time some >>>reasonable percentage (shared_buffers from 1000 to 2000) and measure the >>>change under simulated load. Make another change, test it, chart the >>>shape of the change line. It should look something like this for most >>>folks: >>> >>>shared_buffers | q/s (more is better) >>>100 | 20 >>>200 | 45 >>>400 | 80 >>>1000 | 100 >>>... levels out here... >>>8000 | 110 >>>10000 | 108 >>>20000 | 40 >>>30000 | 20 >>> >>>Note it going back down as we exceed our memory and start swapping >>>shared_buffers. Where that happens on your machine is determined by >>>many things like your machine's memory, memory bandwidth, type of load, >>>etc... but it will happen on most machines and when it does, it often >>>happens at the worst times, under heavy parallel load. >>> >>>Unless testing shows it's faster, 10000 or 25% of mem (whichever is >>>less) is usually a pretty good setting for shared_buffers. Large data >>>sets may require more than 10000, but going over 25% on machines with >>>large memory is usually a mistake, especially servers that do anything >>>other than just PostgreSQL. >>> >>>You're absolutely right about one thing, there's no automatic wizard for >>>tuning this stuff. >>> >> >>Which rather points out the crux of the problem. This is a live system, >>meaning changes made need to be as informed as possible, and that >>changing values for the sake of testing can lead to potential problems >>in service. > > > But if you make those changes slowly, as I was showing, you should see > the small deleterious effects like I was showing long before they become > catastrophic. To just jump shared_buffers to 50000 is not a good idea, > especially if the sweet spot is likely lower than that. > While I agree, there are also issues with the fact that getting consistent results from this site are very much difficult to do, since it is based on the whims of users visiting one of three sites hosted on the same hardware. Now that being said, having wal_buffers at 8 certainly would not be a good idea, since the database logs themselves were warning of excessive writes in that region. I am not hoping for a perfect intermix ratio, that will solve all my problems. But a good idea on a base that will allow me to gain a fair load would certainly be a good option. Right now, the load being handled is not much more then a single processor system did with half the memory. Certainly this architecture should be able to take more of a beating then this? Martin Foster Creator/Designer Ethereal Realms martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Sat Aug 7 07:04:45 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 19CE35E3AC5 for ; Sat, 7 Aug 2004 07:04:43 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 64405-10 for ; Sat, 7 Aug 2004 10:04:34 +0000 (GMT) Received: from pns.mm.eutelsat.org (pns.mm.eutelsat.org [194.214.173.227]) by svr1.postgresql.org (Postfix) with ESMTP id 7A71C5E37CF for ; Sat, 7 Aug 2004 07:04:29 -0300 (ADT) Received: from nts-03.mm.eutelsat.org (localhost [127.0.0.1]) by pns.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i77A42h22217; Sat, 7 Aug 2004 12:04:03 +0200 Received: from [127.0.0.1] (accesspoint.mm.eutelsat.org [194.214.173.4]) by nts-03.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i77A4RZ09440; Sat, 7 Aug 2004 12:04:27 +0200 Message-ID: <4114A900.5070607@bigfoot.com> Date: Sat, 07 Aug 2004 12:03:44 +0200 From: Gaetano Mendola User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Scott Marlowe , "pgsql-performance@postgresql.org" Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <41140D17.7070101@ethereal-realms.org> <41141322.3010200@bigfoot.com> <1091840178.27166.255.camel@localhost.localdomain> <1091853373.27166.260.camel@localhost.localdomain> In-Reply-To: <1091853373.27166.260.camel@localhost.localdomain> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/94 X-Sequence-Number: 7730 Scott Marlowe wrote: > On Fri, 2004-08-06 at 22:02, Martin Foster wrote: > >>Scott Marlowe wrote: >> >> >>>On Fri, 2004-08-06 at 17:24, Gaetano Mendola wrote: >>> >>> >>>>Martin Foster wrote: >>>> >>>> >>>> >>>>>Gaetano Mendola wrote: >>>>> >>>>> >>>>> >>>>>>Let start from your postgres configuration: >>>>>> >>>>>>shared_buffers = 8192 <==== This is really too small for your >>>>>>configuration >>>>>>sort_mem = 2048 >>>>>> >>>>>>wal_buffers = 128 <==== This is really too small for your >>>>>>configuration >>>>>> >>>>>>effective_cache_size = 16000 >>>>>> >>>>>>change this values in: >>>>>> >>>>>>shared_buffers = 50000 >>>>>>sort_mem = 16084 >>>>>> >>>>>>wal_buffers = 1500 >>>>>> >>>>>>effective_cache_size = 32000 >>>>>> >>>>>> >>>>>>to bump up the shm usage you have to configure your OS in order to be >>>>>>allowed to use that ammount of SHM. >>>>>> >>>>>>This are the numbers that I feel good for your HW, the second step now is >>>>>>analyze your queries >>>>>> >>>>> >>>>>These changes have yielded some visible improvements, with load averages >>>>>rarely going over the anything noticeable. However, I do have a >>>>>question on the matter, why do these values seem to be far higher then >>>>>what a frequently pointed to document would indicate as necessary? >>>>> >>>>>http://www.varlena.com/GeneralBits/Tidbits/perf.html >>>>> >>>>>I am simply curious, as this clearly shows that my understanding of >>>>>PostgreSQL is clearly lacking when it comes to tweaking for the hardware. >>>> >>>>Unfortunately there is no a "wizard tuning" for postgres so each one of >>>>us have a own "school". The data I gave you are oversized to be sure >>>>to achieve improvements. Now you can start to decrease these values >>>>( starting from the wal_buffers ) in order to find the good compromise >>>>with your HW. >>> >>> >>>FYI, my school of tuning is to change one thing at a time some >>>reasonable percentage (shared_buffers from 1000 to 2000) and measure the >>>change under simulated load. Make another change, test it, chart the >>>shape of the change line. It should look something like this for most >>>folks: >>> >>>shared_buffers | q/s (more is better) >>>100 | 20 >>>200 | 45 >>>400 | 80 >>>1000 | 100 >>>... levels out here... >>>8000 | 110 >>>10000 | 108 >>>20000 | 40 >>>30000 | 20 >>> >>>Note it going back down as we exceed our memory and start swapping >>>shared_buffers. Where that happens on your machine is determined by >>>many things like your machine's memory, memory bandwidth, type of load, >>>etc... but it will happen on most machines and when it does, it often >>>happens at the worst times, under heavy parallel load. >>> >>>Unless testing shows it's faster, 10000 or 25% of mem (whichever is >>>less) is usually a pretty good setting for shared_buffers. Large data >>>sets may require more than 10000, but going over 25% on machines with >>>large memory is usually a mistake, especially servers that do anything >>>other than just PostgreSQL. >>> >>>You're absolutely right about one thing, there's no automatic wizard for >>>tuning this stuff. >>> >> >>Which rather points out the crux of the problem. This is a live system, >>meaning changes made need to be as informed as possible, and that >>changing values for the sake of testing can lead to potential problems >>in service. > > > But if you make those changes slowly, as I was showing, you should see > the small deleterious effects like I was showing long before they become > catastrophic. To just jump shared_buffers to 50000 is not a good idea, > especially if the sweet spot is likely lower than that. As you can see 50000 are less then 20% of his total memory and I strongly fell that 50000 is not oversized for his hardware ( as wal_buffers isn't), may be could be for his database activity but for sure that value ( values ) can not be source of problems. I'd like to have a wizard that could be run also for hours in order to find the good compromise for all GUC parameters , may be a genetic algoritm can help. Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Sat Aug 7 07:12:01 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id C58525E46C4 for ; Sat, 7 Aug 2004 07:11:51 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 68395-03 for ; Sat, 7 Aug 2004 10:11:50 +0000 (GMT) Received: from pns.mm.eutelsat.org (pns.mm.eutelsat.org [194.214.173.227]) by svr1.postgresql.org (Postfix) with ESMTP id 7E3825E46C1 for ; Sat, 7 Aug 2004 07:11:48 -0300 (ADT) Received: from nts-03.mm.eutelsat.org (localhost [127.0.0.1]) by pns.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i77ABPd22251; Sat, 7 Aug 2004 12:11:25 +0200 Received: from [127.0.0.1] (accesspoint.mm.eutelsat.org [194.214.173.4]) by nts-03.mm.eutelsat.org (8.11.6/linuxconf) with ESMTP id i77ABoZ09457; Sat, 7 Aug 2004 12:11:50 +0200 Message-ID: <4114AABD.7050505@bigfoot.com> Date: Sat, 07 Aug 2004 12:11:09 +0200 From: Gaetano Mendola User-Agent: Mozilla Thunderbird 0.7.1 (Windows/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Tom Lane , "pgsql-performance@postgresql.org" Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <41140D17.7070101@ethereal-realms.org> <24609.1091836821@sss.pgh.pa.us> In-Reply-To: <24609.1091836821@sss.pgh.pa.us> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/95 X-Sequence-Number: 7731 Tom Lane wrote: > Martin Foster writes: > >>Gaetano Mendola wrote: >> >>>change this values in: >>>shared_buffers = 50000 >>>sort_mem = 16084 >>> >>>wal_buffers = 1500 > > > This value of wal_buffers is simply ridiculous. Instead I think is ridiculous a wal_buffers = 8 ( 64KB ) by default. > There isn't any reason to set wal_buffers higher than the amount of > WAL log data that will be generated by a single transaction, because > whatever is in the buffers will be flushed at transaction commit. > If you are mainly dealing with heavy concurrency then it's the mean time > between transaction commits that matters, and that's even less than the > average transaction length. I partially agree with you, tell me how decide that value without even now the typical queries, the tipical load ... nothing. I suggested to OP to keep the wal_buffers so high in order to eliminate one freedom of degree in his performance problems. You can see from following reply, ======================================================================== Gaetano Mendola wrote: Unfortunately there is no a "wizard tuning" for postgres so each one of us have a own "school". The data I gave you are oversized to be sure to achieve improvements. Now you can start to decrease these values ( starting from the wal_buffers ) in order to find the good compromise with your HW. ======================================================================== However wal_buffers = 1500 means ~12 MB that are not so expensive considering a server with 2GB of ram and I think that is a good compromise if you are not starving for RAM. I had a discussion about how fine tuning a postgres server with a client, my question was: are you planning to have someone that periodically take a look at your server activities in order to use your hardware at the best? Easy answer: No, because when the server is overloaded I will buy a bigger one that is less expensive that pay someone, considering also that shareolders prefer increase the capex that pay salaries ( if the company close the hardware can be selled :-( ). This is the real world out there. Regards Gaetano Mendola From pgsql-performance-owner@postgresql.org Sat Aug 7 07:50:23 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 2E84B5E3AC5 for ; Sat, 7 Aug 2004 07:49:57 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 77971-01 for ; Sat, 7 Aug 2004 10:49:48 +0000 (GMT) Received: from vscan02.westnet.com.au (vscan02.westnet.com.au [203.10.1.132]) by svr1.postgresql.org (Postfix) with ESMTP id E85EB5E37CF for ; Sat, 7 Aug 2004 07:49:47 -0300 (ADT) Received: from localhost (localhost.localdomain [127.0.0.1]) by localhost (Postfix) with ESMTP id DF6D3119BE8; Sat, 7 Aug 2004 18:49:50 +0800 (WST) Received: from [192.168.1.9] (dsl-202-72-133-22.wa.westnet.com.au [202.72.133.22]) by vscan02.westnet.com.au (Postfix) with ESMTP id 65EB4119B02; Sat, 7 Aug 2004 18:49:50 +0800 (WST) Message-ID: <4114B3CE.2020504@familyhealth.com.au> Date: Sat, 07 Aug 2004 18:49:50 +0800 From: Christopher Kings-Lynne User-Agent: Mozilla Thunderbird 0.7.2 (Windows/20040707) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Gaetano Mendola Cc: Tom Lane , "pgsql-performance@postgresql.org" Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <41140D17.7070101@ethereal-realms.org> <24609.1091836821@sss.pgh.pa.us> <4114AABD.7050505@bigfoot.com> In-Reply-To: <4114AABD.7050505@bigfoot.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/96 X-Sequence-Number: 7732 >> This value of wal_buffers is simply ridiculous. > > > Instead I think is ridiculous a wal_buffers = 8 ( 64KB ) by default. There is no point making WAL buffers higher than 8. I have done much testing of this and it makes not the slightest difference to performance that I could measure. Chris From pgsql-performance-owner@postgresql.org Sat Aug 7 11:21:13 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 030885E46C1 for ; Sat, 7 Aug 2004 11:21:11 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 28596-01 for ; Sat, 7 Aug 2004 14:21:06 +0000 (GMT) Received: from smtp105.mail.sc5.yahoo.com (smtp105.mail.sc5.yahoo.com [66.163.169.225]) by svr1.postgresql.org (Postfix) with SMTP id 1DBC65E46C0 for ; Sat, 7 Aug 2004 11:21:03 -0300 (ADT) Received: from unknown (HELO jupiter.black-lion.info) (janwieck@68.80.245.191 with login) by smtp105.mail.sc5.yahoo.com with SMTP; 7 Aug 2004 14:21:09 -0000 Received: from [172.21.8.18] ([192.168.192.101]) (authenticated bits=0) by jupiter.black-lion.info (8.12.10/8.12.9) with ESMTP id i77EL23v060896; Sat, 7 Aug 2004 10:21:07 -0400 (EDT) (envelope-from JanWieck@Yahoo.com) Message-ID: <4114E54C.7040200@Yahoo.com> Date: Sat, 07 Aug 2004 10:21:00 -0400 From: Jan Wieck User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.1) Gecko/20040707 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Martin Foster Cc: pgsql-performance@postgresql.org Subject: Re: Performance Bottleneck References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/97 X-Sequence-Number: 7733 On 8/3/2004 2:05 PM, Martin Foster wrote: > I run a Perl/CGI driven website that makes extensive use of PostgreSQL > (7.4.3) for everything from user information to formatting and display > of specific sections of the site. The server itself, is a dual > processor AMD Opteron 1.4Ghz w/ 2GB Ram and 2 x 120GB hard drives > mirrored for redundancy running under FreeBSD 5.2.1 (AMD64). > > Recently loads on the site have increased during peak hours to the point > of showing considerable loss in performance. This can be observed > when connections move from the 120 concurrent connections to PostgreSQL > to roughly 175 or more. Essentially, the machine seems to struggle > to keep up with continual requests and slows down respectively as > resources are tied down. Have you taken a look at pgpool? I know, it sounds silly to *reduce* the number of DB connections through a connection pool, but it can help. Jan -- #======================================================================# # It's easier to get forgiveness for being wrong than for being right. # # Let's break this rule - forgive me. # #================================================== JanWieck@Yahoo.com # From pgsql-performance-owner@postgresql.org Sun Aug 8 02:41:42 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id DDF745E46C9 for ; Sun, 8 Aug 2004 02:40:28 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 47245-02 for ; Sun, 8 Aug 2004 05:40:25 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id CDE825E3E30 for ; Sun, 8 Aug 2004 02:40:25 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i785eOiG047874 for ; Sun, 8 Aug 2004 05:40:24 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i785EWUW042041 for pgsql-performance@postgresql.org; Sun, 8 Aug 2004 05:14:32 GMT From: Martin Foster User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Performance Bottleneck References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <41140D17.7070101@ethereal-realms.org> <24609.1091836821@sss.pgh.pa.us> <4114AABD.7050505@bigfoot.com> <4114B3CE.2020504@familyhealth.com.au> In-Reply-To: <4114B3CE.2020504@familyhealth.com.au> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Lines: 25 Message-ID: Date: Sun, 08 Aug 2004 05:14:32 GMT To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/99 X-Sequence-Number: 7735 Christopher Kings-Lynne wrote: >>> This value of wal_buffers is simply ridiculous. >> >> >> >> Instead I think is ridiculous a wal_buffers = 8 ( 64KB ) by default. > > > There is no point making WAL buffers higher than 8. I have done much > testing of this and it makes not the slightest difference to performance > that I could measure. > > Chris > No point? I had it at 64 if memory serves and logs were warning me that raising this value would be desired because of excessive IO brought upon from the logs being filled far too often. It would seem to me that 8 is a bit low in at least a few circumstances. Martin Foster Creator/Designer Ethereal Realms martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Sun Aug 8 02:29:46 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 7E0FF5E46C0 for ; Sun, 8 Aug 2004 02:29:23 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 44689-02 for ; Sun, 8 Aug 2004 05:29:19 +0000 (GMT) Received: from fep2.cogeco.net (smtp.cogeco.net [216.221.81.25]) by svr1.postgresql.org (Postfix) with ESMTP id 3FB5C5E46D1 for ; Sun, 8 Aug 2004 02:29:19 -0300 (ADT) Received: from [127.0.0.1] (d226-86-215.home.cgocable.net [24.226.86.215]) by fep2.cogeco.net (Postfix) with ESMTP id C0FFD25F6; Sun, 8 Aug 2004 01:29:18 -0400 (EDT) Message-ID: <4115BA2C.3000900@ethereal-realms.org> Date: Sun, 08 Aug 2004 01:29:16 -0400 From: Martin Foster Organization: Ethereal Realms User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 To: Jan Wieck , PostgreSQL Performance Subject: Re: Performance Bottleneck References: <4114E54C.7040200@Yahoo.com> In-Reply-To: <4114E54C.7040200@Yahoo.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/98 X-Sequence-Number: 7734 Jan Wieck wrote: > On 8/3/2004 2:05 PM, Martin Foster wrote: > >> I run a Perl/CGI driven website that makes extensive use of PostgreSQL >> (7.4.3) for everything from user information to formatting and display >> of specific sections of the site. The server itself, is a dual >> processor AMD Opteron 1.4Ghz w/ 2GB Ram and 2 x 120GB hard drives >> mirrored for redundancy running under FreeBSD 5.2.1 (AMD64). >> >> Recently loads on the site have increased during peak hours to the >> point of showing considerable loss in performance. This can be >> observed when connections move from the 120 concurrent connections to >> PostgreSQL to roughly 175 or more. Essentially, the machine seems >> to struggle to keep up with continual requests and slows down >> respectively as resources are tied down. > > > Have you taken a look at pgpool? I know, it sounds silly to *reduce* the > number of DB connections through a connection pool, but it can help. > > > Jan > I am currently making use of Apache::DBI which overrides the DBI::disconnect call and keeps a pool of active connections for use when need be. Since it offloads the pooling to the webserver, it seems more advantageous then pgpool which while being able to run on a external system is not adding another layer of complexity. Anyone had any experience with both Apache::DBI and pgpool? For my needs they seem to do essentially the same thing, simply that one is invisible to the code while the other requires adding the complexity of a proxy. Martin Foster Creator/Designer Ethereal Realms martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Sun Aug 8 05:21:53 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 875495E40AC for ; Sun, 8 Aug 2004 05:21:52 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 81696-06 for ; Sun, 8 Aug 2004 08:21:48 +0000 (GMT) Received: from mail.academyoflearning.ca (s64-180-138-192.bc.hsia.telus.net [64.180.138.192]) by svr1.postgresql.org (Postfix) with ESMTP id 6D6B45E3E30 for ; Sun, 8 Aug 2004 05:21:46 -0300 (ADT) Received: from [192.168.1.10] (d216-232-247-236.bchsia.telus.net [216.232.247.236]) (using SSLv3 with cipher RC4-MD5 (128/128 bits)) (No client certificate requested) by mail.academyoflearning.ca (Postfix) with ESMTP id 368DC2F90E; Sun, 8 Aug 2004 01:21:19 -0700 (PDT) Subject: Re: Performance Bottleneck From: Mike Benoit To: Martin Foster Cc: pgsql-performance@postgresql.org In-Reply-To: References: <410FDC53.5080509@bigfoot.com> <4110FFF6.1030001@bigfoot.com> <1091812011.7149.25.camel@ipso.snappymail.ca> Content-Type: text/plain Date: Sun, 08 Aug 2004 01:21:17 -0700 Message-Id: <1091953277.11520.3.camel@ipso.snappymail.ca> Mime-Version: 1.0 X-Mailer: Evolution 1.5.92.1-1mdk Content-Transfer-Encoding: 7bit X-snappymail-MailScanner-Information: Please contact the ISP for more information X-snappymail-MailScanner: Found to be clean X-snappymail-MailScanner-SpamCheck: not spam, SpamAssassin (score=1.911, required 5, AWL -0.79, RCVD_IN_DYNABLOCK 2.60, RCVD_IN_SORBS 0.10) X-snappymail-MailScanner-SpamScore: s X-MailScanner-From: ipso@snappymail.ca X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/100 X-Sequence-Number: 7736 On Fri, 2004-08-06 at 23:18 +0000, Martin Foster wrote: > Mike Benoit wrote: > > > On Wed, 2004-08-04 at 17:25 +0200, Gaetano Mendola wrote: > > > > > >>>The queries themselves are simple, normally drawing information from one > >>>table with few conditions or in the most complex cases using joins on > >>>two table or sub queries. These behave very well and always have, the > >>>problem is that these queries take place in rather large amounts due to > >>>the dumb nature of the scripts themselves. > >> > >>Show us the explain analyze on that queries, how many rows the tables are > >>containing, the table schema could be also usefull. > >> > > > > > > If the queries themselves are optimized as much as they can be, and as > > you say, its just the sheer amount of similar queries hitting the > > database, you could try using prepared queries for ones that are most > > often executed to eliminate some of the overhead. > > > > I've had relatively good success with this in the past, and it doesn't > > take very much code modification. > > > > One of the biggest problems is most probably related to the indexes. > Since the performance penalty of logging the information needed to see > which queries are used and which are not is a slight problem, then I > cannot really make use of it for now. > > However, I am curious how one would go about preparing query? Is this > similar to the DBI::Prepare statement with placeholders and simply > changing the values passed on execute? Or is this something database > level such as a view et cetera? > Yes, always optimize your queries and GUC settings first and foremost. Thats where you are likely to gain the most performance. After that if you still want to push things even further I would try prepared queries. I'm not familiar with DBI::Prepare at all, but I don't think its what your looking for. This is what you want: http://www.postgresql.org/docs/current/static/sql-prepare.html -- Mike Benoit From pgsql-performance-owner@postgresql.org Sun Aug 8 09:10:28 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3ED455E37CF for ; Sun, 8 Aug 2004 09:10:18 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 33436-10 for ; Sun, 8 Aug 2004 12:10:15 +0000 (GMT) Received: from rwcrmhc12.comcast.net (rwcrmhc12.comcast.net [216.148.227.85]) by svr1.postgresql.org (Postfix) with ESMTP id B78565E37CE for ; Sun, 8 Aug 2004 09:10:12 -0300 (ADT) Received: from jefftrout.com ([24.128.241.68]) by comcast.net (rwcrmhc12) with SMTP id <20040808121015014004lh81e>; Sun, 8 Aug 2004 12:10:15 +0000 Received: (qmail 86891 invoked from network); 8 Aug 2004 12:10:15 -0000 Received: from unknown (HELO ?192.168.0.102?) (10.10.10.20) by 10.10.10.10 with SMTP; 8 Aug 2004 12:10:15 -0000 In-Reply-To: <4115BA2C.3000900@ethereal-realms.org> References: <4114E54C.7040200@Yahoo.com> <4115BA2C.3000900@ethereal-realms.org> Mime-Version: 1.0 (Apple Message framework v618) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: Content-Transfer-Encoding: 7bit Cc: PostgreSQL Performance , Jan Wieck From: Jeff Subject: Re: Performance Bottleneck Date: Sun, 8 Aug 2004 08:10:24 -0400 To: Martin Foster X-Mailer: Apple Mail (2.618) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/101 X-Sequence-Number: 7737 On Aug 8, 2004, at 1:29 AM, Martin Foster wrote: > I am currently making use of Apache::DBI which overrides the > DBI::disconnect call and keeps a pool of active connections for use > when need be. Since it offloads the pooling to the webserver, it > seems more advantageous then pgpool which while being able to run on a > external system is not adding another layer of complexity. > Apache::DBI is not the same sort of a pool as pgpool. DB connections are not shared among all your apache children (A common misconception). So if you have 300 apache kids you can have have 300 db connections. With pgpool connections are shared among all of them so even though you have 300 kids you only have say 32 db connections. > Anyone had any experience with both Apache::DBI and pgpool? For my > needs they seem to do essentially the same thing, simply that one is > invisible to the code while the other requires adding the complexity > of a proxy. > Both are invisible to the app. (With pgpool it thinks it is connecting to a regular old PG server) And I've been running pgpool in production for months. It just sits there. Doesn't take much to set it up or configure it. Works like a champ -- Jeff Trout http://www.jefftrout.com/ http://www.stuarthamm.net/ From pgsql-performance-owner@postgresql.org Sun Aug 8 10:53:39 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3470B5E46D5 for ; Sun, 8 Aug 2004 10:52:18 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 55546-05 for ; Sun, 8 Aug 2004 13:52:15 +0000 (GMT) Received: from smtp105.mail.sc5.yahoo.com (smtp105.mail.sc5.yahoo.com [66.163.169.225]) by svr1.postgresql.org (Postfix) with SMTP id 128D85E46CB for ; Sun, 8 Aug 2004 10:52:08 -0300 (ADT) Received: from unknown (HELO jupiter.black-lion.info) (janwieck@68.80.245.191 with login) by smtp105.mail.sc5.yahoo.com with SMTP; 8 Aug 2004 13:52:13 -0000 Received: from [172.21.8.18] ([192.168.192.101]) (authenticated bits=0) by jupiter.black-lion.info (8.12.10/8.12.9) with ESMTP id i78Dq53v064577; Sun, 8 Aug 2004 09:52:05 -0400 (EDT) (envelope-from JanWieck@Yahoo.com) Message-ID: <41163001.8040500@Yahoo.com> Date: Sun, 08 Aug 2004 09:52:01 -0400 From: Jan Wieck User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.1) Gecko/20040707 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Jeff Cc: Martin Foster , PostgreSQL Performance Subject: Re: Performance Bottleneck References: <4114E54C.7040200@Yahoo.com> <4115BA2C.3000900@ethereal-realms.org> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/102 X-Sequence-Number: 7738 On 8/8/2004 8:10 AM, Jeff wrote: > On Aug 8, 2004, at 1:29 AM, Martin Foster wrote: > >> I am currently making use of Apache::DBI which overrides the >> DBI::disconnect call and keeps a pool of active connections for use >> when need be. Since it offloads the pooling to the webserver, it >> seems more advantageous then pgpool which while being able to run on a >> external system is not adding another layer of complexity. >> > > Apache::DBI is not the same sort of a pool as pgpool. DB connections > are not shared among all your apache children (A common misconception). > So if you have 300 apache kids you can have have 300 db connections. > With pgpool connections are shared among all of them so even though > you have 300 kids you only have say 32 db connections. And this is exactly where the pgpool advantage lies. Especially with the TPC-W, the Apache is serving a mix of PHP (or whatever CGI technique is used) and static content like images. Since the 200+ Apache kids serve any of that content by random and the emulated browsers very much encourage it to ramp up MaxClients children by using up to 4 concurrent image connections, one does end up with MaxClients DB connections that are all relatively low frequently used. In contrast to that the real pgpool causes lesser, more active DB connections, which is better for performance. > >> Anyone had any experience with both Apache::DBI and pgpool? For my >> needs they seem to do essentially the same thing, simply that one is >> invisible to the code while the other requires adding the complexity >> of a proxy. >> > > Both are invisible to the app. (With pgpool it thinks it is connecting > to a regular old PG server) > > And I've been running pgpool in production for months. It just sits > there. Doesn't take much to set it up or configure it. Works like a > champ And it buys you some extra admin feature people like to forget about it. One can shut down one pool for one web application only. That gives you instant single user access to one database without shutting down the whole webserver or tempering with the pg_hba.conf file. Jan -- #======================================================================# # It's easier to get forgiveness for being wrong than for being right. # # Let's break this rule - forgive me. # #================================================== JanWieck@Yahoo.com # From pgsql-performance-owner@postgresql.org Sun Aug 8 11:30:54 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id DF40C5E4699 for ; Sun, 8 Aug 2004 11:29:42 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 63246-10 for ; Sun, 8 Aug 2004 14:29:39 +0000 (GMT) Received: from bayswater1.ymogen.net (host-154-240-27-217.pobox.net.uk [217.27.240.154]) by svr1.postgresql.org (Postfix) with ESMTP id DBCFF5E46C2 for ; Sun, 8 Aug 2004 11:29:34 -0300 (ADT) Received: from solent (82-68-95-1.dsl.in-addr.zen.co.uk [82.68.95.1]) by bayswater1.ymogen.net (Postfix) with ESMTP id 4A6ABA55C5; Sun, 8 Aug 2004 15:29:39 +0100 (BST) Reply-To: From: "Matt Clark" To: "'Jan Wieck'" , "'Jeff'" Cc: "'Martin Foster'" , "'PostgreSQL Performance'" Subject: Re: Performance Bottleneck Date: Sun, 8 Aug 2004 15:29:39 +0100 Organization: Ymogen Ltd Message-ID: <007f01c47d54$233b4bf0$8300a8c0@solent> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 In-Reply-To: <41163001.8040500@Yahoo.com> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 Importance: Normal X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/103 X-Sequence-Number: 7739 > And this is exactly where the pgpool advantage lies. > Especially with the > TPC-W, the Apache is serving a mix of PHP (or whatever CGI > technique is > used) and static content like images. Since the 200+ Apache > kids serve > any of that content by random and the emulated browsers very much > encourage it to ramp up MaxClients children by using up to 4 > concurrent > image connections, one does end up with MaxClients DB > connections that > are all relatively low frequently used. In contrast to that the real > pgpool causes lesser, more active DB connections, which is better for > performance. There are two well-worn and very mature techniques for dealing with the issue of web apps using one DB connection per apache process, both of which work extremely well and attack the issue at its source. 1) Use a front-end caching proxy like Squid as an accelerator. Static content will be served by the accelerator 99% of the time. Additionally, large pages can be served immediately to the accelerator by Apache, which can then go on to serve another request without waiting for the end user's dial-up connection to pull the data down. Massive speedup, fewer apache processes needed. 2) Serve static content off an entirely separate apache server than the dynamic content, but by using separate domains (e.g. 'static.foo.com'). Personally I favour number 1. Our last biggish peak saw 6000 open HTTP and HTTPS connections and only 200 apache children, all of them nice and busy, not hanging around on street corners looking bored. During quiet times Apache drops back to its configured minimum of 40 kids. Option 2 has the advantage that you can use a leaner build for the 'dynamic' apache server, but with RAM so plentiful these days that's a less useful property. Basically this puts the 'pooling' back in the stateless HTTP area where it truly belongs and can be proven not to have any peculiar side effects (especially when it comes to transaction safety). Even better, so long as you use URL parameters for searches and the like, you can have the accelerator cache those pages for a certain time too so long as slightly stale results are OK. I'm sure pgpool and the like have their place, but being band-aids for poorly configured websites probably isn't the best use for them. M From pgsql-performance-owner@postgresql.org Sun Aug 8 12:49:25 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 44C4D5E46C4 for ; Sun, 8 Aug 2004 12:49:21 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 81193-07 for ; Sun, 8 Aug 2004 15:49:19 +0000 (GMT) Received: from fep2.cogeco.net (smtp.cogeco.net [216.221.81.25]) by svr1.postgresql.org (Postfix) with ESMTP id F05235E40BB for ; Sun, 8 Aug 2004 12:49:10 -0300 (ADT) Received: from [127.0.0.1] (d226-86-215.home.cgocable.net [24.226.86.215]) by fep2.cogeco.net (Postfix) with ESMTP id 1BC3B2515; Sun, 8 Aug 2004 11:49:17 -0400 (EDT) Message-ID: <41164B76.1030603@ethereal-realms.org> Date: Sun, 08 Aug 2004 11:49:10 -0400 From: Martin Foster Organization: Ethereal Realms User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 To: Jeff , PostgreSQL Performance Subject: Re: Performance Bottleneck References: <4114E54C.7040200@Yahoo.com> <4115BA2C.3000900@ethereal-realms.org> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/104 X-Sequence-Number: 7740 Jeff wrote: > > On Aug 8, 2004, at 1:29 AM, Martin Foster wrote: > >> I am currently making use of Apache::DBI which overrides the >> DBI::disconnect call and keeps a pool of active connections for use >> when need be. Since it offloads the pooling to the webserver, it >> seems more advantageous then pgpool which while being able to run on a >> external system is not adding another layer of complexity. >> > > Apache::DBI is not the same sort of a pool as pgpool. DB connections > are not shared among all your apache children (A common misconception). > So if you have 300 apache kids you can have have 300 db connections. > With pgpool connections are shared among all of them so even though you > have 300 kids you only have say 32 db connections. > Seems that you are right, never noticed that from the documentation before. I always assumed it had something to do with the long lasting/persistent scripts that would remain in transactions for extended periods of time. Here is an odd question. While the server run 7.4.x, the client connects with 7.3.x. Would this in itself make a difference in performance as the protocols are different? At least based from pgpool's documentation. Martin Foster Creator/Designer Ethereal Realms martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Sun Aug 8 13:03:32 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id DCD8F5E46C3 for ; Sun, 8 Aug 2004 13:03:13 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 84368-09 for ; Sun, 8 Aug 2004 16:03:16 +0000 (GMT) Received: from ipact2.infopact.nl (x71.infopact.nl [212.29.160.71]) by svr1.postgresql.org (Postfix) with ESMTP id BAB775E4699 for ; Sun, 8 Aug 2004 13:03:07 -0300 (ADT) Received: from [127.0.0.1] (154-90.ipact.nl [82.210.90.154]) by ipact2.infopact.nl (8.12.10/8.12.10) with ESMTP id i78G3Alx014107 for ; Sun, 8 Aug 2004 18:03:12 +0200 Message-ID: <41164E98.8030504@vulcanus.its.tudelft.nl> Date: Sun, 08 Aug 2004 18:02:32 +0200 From: Arjen van der Meijden User-Agent: Mozilla Thunderbird 0.7.3 (Windows/20040803) X-Accept-Language: en-us, en MIME-Version: 1.0 To: "'PostgreSQL Performance'" Subject: Re: Performance Bottleneck References: <007f01c47d54$233b4bf0$8300a8c0@solent> In-Reply-To: <007f01c47d54$233b4bf0$8300a8c0@solent> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/105 X-Sequence-Number: 7741 On 8-8-2004 16:29, Matt Clark wrote: > There are two well-worn and very mature techniques for dealing with the > issue of web apps using one DB connection per apache process, both of which > work extremely well and attack the issue at its source. > > 1) Use a front-end caching proxy like Squid as an accelerator. Static > content will be served by the accelerator 99% of the time. Additionally, > large pages can be served immediately to the accelerator by Apache, which > can then go on to serve another request without waiting for the end user's > dial-up connection to pull the data down. Massive speedup, fewer apache > processes needed. Another version of this 1) is to run with a "content accelerator"; our "favourite" is to run Tux in front of Apache. It takes over the connection-handling stuff, has a very low memoryprofile (compared to Apache) and very little overhead. What it does, is to serve up all "simple" content (although you can have cgi/php/perl and other languages being processed by it, entirely disabling the need for apache in some cases) and forwards/proxies everything it doesn't understand to an Apache/other webserver running at the same machine (which runs on another port). I think there are a few advantages over Squid; since it is partially done in kernel-space it can be slightly faster in serving up content, apart from its simplicity which will probably matter even more. You'll have no caching issues for pages that should not be cached or static files that change periodically (like every few seconds). Afaik Tux can handle more than 10 times as much ab-generated requests per second than a default-compiled Apache on the same machine. And besides the speed-up, you can do any request you where able to do before, since Tux will simply forward it to Apache if it didn't understand it. Anyway, apart from all that. Reducing the amount of apache-connections is nice, but not really the same as reducing the amount of pooled-connections using a db-pool... You may even be able to run with 1000 http-connections, 40 apache-processes and 10 db-connections. In case of the non-pooled setup, you'd still have 40 db-connections. In a simple test I did, I did feel pgpool had quite some overhead though. So it should be well tested, to find out where the turnover-point is where it will be a gain instead of a loss... Best regards, Arjen van der Meijden From pgsql-performance-owner@postgresql.org Sun Aug 8 15:40:43 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 9407D5E46BF for ; Sun, 8 Aug 2004 15:40:40 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 20789-08 for ; Sun, 8 Aug 2004 18:40:35 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 59EB35E40AC for ; Sun, 8 Aug 2004 15:40:35 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i78IeUiI024976 for ; Sun, 8 Aug 2004 18:40:32 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i78IIFeX019694 for pgsql-performance@postgresql.org; Sun, 8 Aug 2004 18:18:15 GMT From: Martin Foster User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-ca, en-gb, en-us, en MIME-Version: 1.0 X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Performance Bottleneck References: <007f01c47d54$233b4bf0$8300a8c0@solent> <41164E98.8030504@vulcanus.its.tudelft.nl> In-Reply-To: <41164E98.8030504@vulcanus.its.tudelft.nl> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Lines: 74 Message-ID: Date: Sun, 08 Aug 2004 18:18:15 GMT To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/106 X-Sequence-Number: 7742 Arjen van der Meijden wrote: > On 8-8-2004 16:29, Matt Clark wrote: > >> There are two well-worn and very mature techniques for dealing with the >> issue of web apps using one DB connection per apache process, both of >> which >> work extremely well and attack the issue at its source. >> >> 1) Use a front-end caching proxy like Squid as an accelerator. Static >> content will be served by the accelerator 99% of the time. Additionally, >> large pages can be served immediately to the accelerator by Apache, which >> can then go on to serve another request without waiting for the end >> user's >> dial-up connection to pull the data down. Massive speedup, fewer apache >> processes needed. > > > Another version of this 1) is to run with a "content accelerator"; our > "favourite" is to run Tux in front of Apache. It takes over the > connection-handling stuff, has a very low memoryprofile (compared to > Apache) and very little overhead. What it does, is to serve up all > "simple" content (although you can have cgi/php/perl and other languages > being processed by it, entirely disabling the need for apache in some > cases) and forwards/proxies everything it doesn't understand to an > Apache/other webserver running at the same machine (which runs on > another port). > > I think there are a few advantages over Squid; since it is partially > done in kernel-space it can be slightly faster in serving up content, > apart from its simplicity which will probably matter even more. You'll > have no caching issues for pages that should not be cached or static > files that change periodically (like every few seconds). Afaik Tux can > handle more than 10 times as much ab-generated requests per second than > a default-compiled Apache on the same machine. > And besides the speed-up, you can do any request you where able to do > before, since Tux will simply forward it to Apache if it didn't > understand it. > > Anyway, apart from all that. Reducing the amount of apache-connections > is nice, but not really the same as reducing the amount of > pooled-connections using a db-pool... You may even be able to run with > 1000 http-connections, 40 apache-processes and 10 db-connections. In > case of the non-pooled setup, you'd still have 40 db-connections. > > In a simple test I did, I did feel pgpool had quite some overhead > though. So it should be well tested, to find out where the > turnover-point is where it will be a gain instead of a loss... > > Best regards, > > Arjen van der Meijden > Other then images, there are very few static pages being loaded up by the user. Since they make up a very small portion of the traffic, it tends to be an optimization we can forgo for now. I attempted to make use of pgpool. At the default 32 connections pre-forked the webserver almost immediately tapped out the pgpool base and content stopped being served because no new processes were being forked to make up for it. So I raised it to a higher value (256) and it immediately segfaulted and dropped the core. So not sure exactly how to proceed, since I rather need the thing to fork additional servers as load hits and not the other way around. Unless I had it configured oddly, but it seems work differently then an Apache server would to handle content. Martin Foster Creator/Designer Ethereal Realms martin@ethereal-realms.org From pgsql-performance-owner@postgresql.org Sun Aug 8 22:07:10 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 82EA514B2867 for ; Sun, 8 Aug 2004 22:07:08 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 11103-05 for ; Mon, 9 Aug 2004 01:07:03 +0000 (GMT) Received: from sraigw.sra.co.jp (sraigw.sra.co.jp [202.32.10.2]) by svr1.postgresql.org (Postfix) with ESMTP id AA46014B2827 for ; Sun, 8 Aug 2004 22:07:00 -0300 (ADT) Received: from srascb.sra.co.jp (srascb [133.137.8.65]) by sraigw.sra.co.jp (Postfix) with ESMTP id 5934263041; Mon, 9 Aug 2004 10:07:04 +0900 (JST) Received: from srascb.sra.co.jp (localhost [127.0.0.1]) by localhost.sra.co.jp (Postfix) with ESMTP id 4114610CD05; Mon, 9 Aug 2004 10:07:04 +0900 (JST) Received: from sranhm.sra.co.jp (sranhm.sra.co.jp [133.137.44.16]) by srascb.sra.co.jp (Postfix) with ESMTP id 1448C10CD04; Mon, 9 Aug 2004 10:07:04 +0900 (JST) Received: from localhost (IDENT:t-ishii@srapc2345.sra.co.jp [133.137.44.184]) by sranhm.sra.co.jp (8.9.3+3.2W/3.7W-srambox) with ESMTP id KAA29592; Mon, 9 Aug 2004 10:07:03 +0900 Date: Mon, 09 Aug 2004 10:09:23 +0900 (JST) Message-Id: <20040809.100923.26536346.t-ishii@sra.co.jp> To: martin@ethereal-realms.org Cc: threshar@torgo.978.org, pgsql-performance@postgresql.org Subject: Re: Performance Bottleneck From: Tatsuo Ishii In-Reply-To: <41164B76.1030603@ethereal-realms.org> References: <4115BA2C.3000900@ethereal-realms.org> <41164B76.1030603@ethereal-realms.org> X-Mailer: Mew version 2.3 on Emacs 20.7 / Mule 4.1 =?iso-2022-jp?B?KBskQjAqGyhCKQ==?= Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/107 X-Sequence-Number: 7743 > Jeff wrote: > > > > On Aug 8, 2004, at 1:29 AM, Martin Foster wrote: > > > >> I am currently making use of Apache::DBI which overrides the > >> DBI::disconnect call and keeps a pool of active connections for use > >> when need be. Since it offloads the pooling to the webserver, it > >> seems more advantageous then pgpool which while being able to run on a > >> external system is not adding another layer of complexity. > >> > > > > Apache::DBI is not the same sort of a pool as pgpool. DB connections > > are not shared among all your apache children (A common misconception). > > So if you have 300 apache kids you can have have 300 db connections. > > With pgpool connections are shared among all of them so even though you > > have 300 kids you only have say 32 db connections. > > > > Seems that you are right, never noticed that from the documentation > before. I always assumed it had something to do with the long > lasting/persistent scripts that would remain in transactions for > extended periods of time. > > Here is an odd question. While the server run 7.4.x, the client > connects with 7.3.x. Would this in itself make a difference in > performance as the protocols are different? At least based from > pgpool's documentation. In this case the server fall back from V3 protocol (employed in 7.4 or later) to V2 protocol (employed in from 6.4 to 7.3.x). As far as pgpool concerning, performance difference is significant. Of course that depends on the implementation though. FYI here is the outline of the testing using pgbench. H/W: Pentium4 2.4GHz x2/memory 1GB/HDD IDE 80GB (all PCs are same spec) S/W: RedHat Linux 9/PostgreSQL 7.3.6/7.4.3 postgresql.conf: tcpip_socket = true max_connections = 512 shared_buffers = 2048 host A: pgbench, host B: pgpool, host C: PostgreSQL 7.3.6 or 7.4.3 pgbench parameters: -S -c 10 -t 1000 result: TPS ratio(7.4.3) ratio(7.3.6) ---------------------------------------------------------------------------------------------------- without pgpool 4357.625059 100% 100% with pgpool(connection pool mode) 4330.290294 99.4% 94.1% with pgpool(replication mode) 4297.614996 98.6% 87.6% with pgpoo(replication with strictmode) 4270.223136 98.0% 81.5% -- Tatsuo Ishii From pgsql-performance-owner@postgresql.org Sun Aug 8 22:09:54 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 14F4B14B2824 for ; Sun, 8 Aug 2004 22:09:53 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 10958-06 for ; Mon, 9 Aug 2004 01:09:47 +0000 (GMT) Received: from sraigw.sra.co.jp (sraigw.sra.co.jp [202.32.10.2]) by svr1.postgresql.org (Postfix) with ESMTP id 93C3414B2867 for ; Sun, 8 Aug 2004 22:09:45 -0300 (ADT) Received: from srascb.sra.co.jp (srascb [133.137.8.65]) by sraigw.sra.co.jp (Postfix) with ESMTP id 77AFC62E6D; Mon, 9 Aug 2004 10:09:48 +0900 (JST) Received: from srascb.sra.co.jp (localhost [127.0.0.1]) by localhost.sra.co.jp (Postfix) with ESMTP id 54B4810CD06; Mon, 9 Aug 2004 10:09:48 +0900 (JST) Received: from sranhm.sra.co.jp (sranhm.sra.co.jp [133.137.44.16]) by srascb.sra.co.jp (Postfix) with ESMTP id 30C6A10CD04; Mon, 9 Aug 2004 10:09:48 +0900 (JST) Received: from localhost (IDENT:t-ishii@srapc2345.sra.co.jp [133.137.44.184]) by sranhm.sra.co.jp (8.9.3+3.2W/3.7W-srambox) with ESMTP id KAA29840; Mon, 9 Aug 2004 10:09:48 +0900 Date: Mon, 09 Aug 2004 10:12:07 +0900 (JST) Message-Id: <20040809.101207.98857407.t-ishii@sra.co.jp> To: martin@ethereal-realms.org Cc: pgsql-performance@postgresql.org Subject: Re: Performance Bottleneck From: Tatsuo Ishii In-Reply-To: References: <007f01c47d54$233b4bf0$8300a8c0@solent> <41164E98.8030504@vulcanus.its.tudelft.nl> X-Mailer: Mew version 2.3 on Emacs 20.7 / Mule 4.1 =?iso-2022-jp?B?KBskQjAqGyhCKQ==?= Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/108 X-Sequence-Number: 7744 > Arjen van der Meijden wrote: > > > On 8-8-2004 16:29, Matt Clark wrote: > > > >> There are two well-worn and very mature techniques for dealing with the > >> issue of web apps using one DB connection per apache process, both of > >> which > >> work extremely well and attack the issue at its source. > >> > >> 1) Use a front-end caching proxy like Squid as an accelerator. Static > >> content will be served by the accelerator 99% of the time. Additionally, > >> large pages can be served immediately to the accelerator by Apache, which > >> can then go on to serve another request without waiting for the end > >> user's > >> dial-up connection to pull the data down. Massive speedup, fewer apache > >> processes needed. > > > > > > Another version of this 1) is to run with a "content accelerator"; our > > "favourite" is to run Tux in front of Apache. It takes over the > > connection-handling stuff, has a very low memoryprofile (compared to > > Apache) and very little overhead. What it does, is to serve up all > > "simple" content (although you can have cgi/php/perl and other languages > > being processed by it, entirely disabling the need for apache in some > > cases) and forwards/proxies everything it doesn't understand to an > > Apache/other webserver running at the same machine (which runs on > > another port). > > > > I think there are a few advantages over Squid; since it is partially > > done in kernel-space it can be slightly faster in serving up content, > > apart from its simplicity which will probably matter even more. You'll > > have no caching issues for pages that should not be cached or static > > files that change periodically (like every few seconds). Afaik Tux can > > handle more than 10 times as much ab-generated requests per second than > > a default-compiled Apache on the same machine. > > And besides the speed-up, you can do any request you where able to do > > before, since Tux will simply forward it to Apache if it didn't > > understand it. > > > > Anyway, apart from all that. Reducing the amount of apache-connections > > is nice, but not really the same as reducing the amount of > > pooled-connections using a db-pool... You may even be able to run with > > 1000 http-connections, 40 apache-processes and 10 db-connections. In > > case of the non-pooled setup, you'd still have 40 db-connections. > > > > In a simple test I did, I did feel pgpool had quite some overhead > > though. So it should be well tested, to find out where the > > turnover-point is where it will be a gain instead of a loss... I don't know what were the configurations you are using, but I noticed that UNIX domain sockets are preferred for the connection bwteen clients and pgpool. When I tested using pgbench -C (involving connection estblishing for each transaction), with-pgpool-configuration 10 times faster than without-pgpool-conf if using UNIX domain sockets, while there is only 3.6 times speed up with TCP/IP sockets. > > Best regards, > > > > Arjen van der Meijden > > > > Other then images, there are very few static pages being loaded up by > the user. Since they make up a very small portion of the traffic, it > tends to be an optimization we can forgo for now. > > I attempted to make use of pgpool. At the default 32 connections > pre-forked the webserver almost immediately tapped out the pgpool base > and content stopped being served because no new processes were being > forked to make up for it. > > So I raised it to a higher value (256) and it immediately segfaulted and > dropped the core. So not sure exactly how to proceed, since I rather > need the thing to fork additional servers as load hits and not the other > way around. What version of pgpool did you test? I know that certain version (actually 2.0.2) had such that problem. Can you try again with the latest verison of pgpool? (it's 2.0.6). -- Tatsuo Ishii From pgsql-performance-owner@postgresql.org Tue Aug 10 14:33:44 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3F11014B280D for ; Mon, 9 Aug 2004 08:40:41 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 81318-01 for ; Mon, 9 Aug 2004 11:40:39 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 49B7314B2800 for ; Mon, 9 Aug 2004 08:40:38 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i79BebiG081878 for ; Mon, 9 Aug 2004 11:40:37 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i79BGFPH074687 for pgsql-performance@postgresql.org; Mon, 9 Aug 2004 11:16:15 GMT From: CoL X-Newsgroups: comp.databases.postgresql.performance Subject: Re: The black art of postgresql.conf tweaking Date: Mon, 09 Aug 2004 13:16:03 +0200 Organization: Hub.Org Networking Services Lines: 44 Message-ID: References: <4110DA83.7020505@clockltd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: usenet@news.hub.org User-Agent: Mozilla Thunderbird 0.7.3 (Windows/20040803) X-Accept-Language: en-us, en In-Reply-To: <4110DA83.7020505@clockltd.com> To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/124 X-Sequence-Number: 7760 hi, Paul Serby wrote: > Can anyone give a good reference site/book for getting the most out of > your postgres server. > > All I can find is contradicting theories on how to work out your settings. > > This is what I followed to setup our db server that serves our web > applications. > > http://www.phpbuilder.com/columns/smith20010821.php3?page=2 > > We have a Dell Poweredge with the following spec. > > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) > Physical Memory: 2077264 kB > Swap Memory: 2048244 kB > > Apache on the Web server can take up to 300 connections and PHP is using > pg_pconnect > > Postgres is set with the following. > > max_connections = 300 > shared_buffers = 38400 > sort_mem = 12000 > > But Apache is still maxing out the non-super user connection limit. > > The machine is under no load and I would like to up the max_connections > but I would like to know more about what you need to consider before > doing so. One more: In php.ini, set the pgsql.max_persistent lower then 300 ; Maximum number of persistent links. -1 means no limit. pgsql.max_persistent = -1 -> change this C. From pgsql-performance-owner@postgresql.org Mon Aug 9 11:28:31 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id DB3BE14B2824 for ; Mon, 9 Aug 2004 11:28:22 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 34453-10 for ; Mon, 9 Aug 2004 14:28:13 +0000 (GMT) Received: from mail.clockltd.com (unknown [213.219.6.249]) by svr1.postgresql.org (Postfix) with ESMTP id 2506414B2800 for ; Mon, 9 Aug 2004 11:28:10 -0300 (ADT) Received: from [193.195.120.35] (helo=[10.0.0.113]) by mail.clockltd.com with asmtp (TLS-1.0:DHE_RSA_AES_128_CBC_SHA:16) (Exim 4.34) id 1BuB82-0000hU-Ja for pgsql-performance@postgresql.org; Mon, 09 Aug 2004 15:27:58 +0100 Message-ID: <411789F1.6020305@clockltd.com> Date: Mon, 09 Aug 2004 15:28:01 +0100 From: Paul Serby Organization: Clock User-Agent: Mozilla Thunderbird 0.7.1 (X11/20040626) X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: The black art of postgresql.conf tweaking References: <4110DA83.7020505@clockltd.com> In-Reply-To: <4110DA83.7020505@clockltd.com> X-Enigmail-Version: 0.84.2.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Clock-Relay: yes X-Clock-MailScanner-Information: Please contact the ISP for more information X-Clock-MailScanner: Found to be clean X-Clock-MailScanner-SpamCheck: not spam, SpamAssassin (score=0, required 5, autolearn=not spam) X-MailScanner-From: paul.serby@clockltd.com X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/110 X-Sequence-Number: 7746 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Thanks to everyone for there help. I've changed my postgres settings to the following max_connections = 500 shared_buffers = 10000 sort_mem = 2000 effective_cache_size = 5000 The 'effective_cache_size' is just a guess, but some references suggest it so I added it. Dropping the Apache Keep-alive down to 3 seconds seems to have was a great tip I now have far less idle connections hanging about. I've not maxed out the connections since making the changes, but I'm still not convinced everything is running as well as it could be. I've got some big result sets that need sorting and I'm sure I could spare a bit more sort memory. Where does everyone get there information about the settings? I still can't find anything that helps explain each of the settings and how you determine there optimal settings. If anyone wants interested here is a table schema form one of the most used tables. CREATE TABLE "tblForumMessages" ( ~ "pk_iForumMessagesID" serial, ~ "fk_iParentMessageID" integer DEFAULT 0 NOT NULL, ~ "fk_iAuthorID" integer NOT NULL, ~ "sSubject" character varying(255) NOT NULL, ~ "sBody" text, ~ "fk_iImageID" oid, ~ "dtCreatedOn" timestamp with time zone DEFAULT now(), ~ "iType" integer DEFAULT 0, ~ "bAnonymous" boolean DEFAULT false, ~ "bLocked" boolean DEFAULT false, ~ "dtHidden" timestamp with time zone, ~ "fk_iReplyToID" integer, ~ "iCreateLevel" integer DEFAULT 7 ); This is the query that is most called on the server explained EXPLAIN ANALYZE SELECT "tblForumMessages".* FROM "tblForumMessages" WHERE "fk_iParentMessageID" = 90 ORDER BY "dtCreatedOn" DESC Which gives the following: Sort (cost=8156.34..8161.71 rows=2150 width=223) (actual time=0.264..0.264 rows=0 loops=1) ~ Sort Key: "dtCreatedOn" ~ -> Index Scan using "fk_iParentMessageID_key" on "tblForumMessages" ~ (cost=0.00..8037.33 rows=2150 width=223) (actual time=0.153..0.153 rows=0 loops=1) ~ Index Cond: ("fk_iParentMessageID" = 90) ~ Total runtime: 0.323 ms SELECT COUNT(*) FROM "tblForumMessages" WHERE "fk_iParentMessageID" = 90 Returns: 22920 SELECT COUNT(*) FROM "tblForumMessages" Returns: 429913 Paul Serby wrote: | Can anyone give a good reference site/book for getting the most out of | your postgres server. | | All I can find is contradicting theories on how to work out your settings. | | This is what I followed to setup our db server that serves our web | applications. | | http://www.phpbuilder.com/columns/smith20010821.php3?page=2 | | We have a Dell Poweredge with the following spec. | | CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) | CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) | CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) | CPU: Intel(R) Xeon(TM) CPU 3.06GHz (512 KB Cache) | Physical Memory: 2077264 kB | Swap Memory: 2048244 kB | | Apache on the Web server can take up to 300 connections and PHP is using | pg_pconnect | | Postgres is set with the following. | | max_connections = 300 | shared_buffers = 38400 | sort_mem = 12000 | | But Apache is still maxing out the non-super user connection limit. | | The machine is under no load and I would like to up the max_connections | but I would like to know more about what you need to consider before | doing so. | | The only other source I've found is this: | | http://www.varlena.com/varlena/GeneralBits/Tidbits/annotated_conf_e.html | | But following its method my postgres server locks up straight away as it | recommends setting max_connections to 16 for Web sites? | | Is there a scientific method for optimizing postgres or is it all | 'finger in the air' and trial and error. | | ---------------------------(end of broadcast)--------------------------- | TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFBF4nxp51pUZR6gxsRAi8cAJ9HBfpNMGQR7vurk0wYW+p6KfqZzACfc9NX k72iabZxK+gku06Pf7NmHfQ= =Ftv6 -----END PGP SIGNATURE----- From pgsql-performance-owner@postgresql.org Mon Aug 9 11:47:14 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 6177514B2825 for ; Mon, 9 Aug 2004 11:47:01 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 43763-03 for ; Mon, 9 Aug 2004 14:46:54 +0000 (GMT) Received: from frodo.hserus.net (frodo.hserus.net [204.74.68.40]) by svr1.postgresql.org (Postfix) with ESMTP id 14CC714B2800 for ; Mon, 9 Aug 2004 11:46:52 -0300 (ADT) Received: from [203.199.147.2] (port=42122 helo=ps0499.intranet.persistent.co.in) by frodo.hserus.net with asmtp (Cipher TLSv1:RC4-MD5:128) (Exim 4.41 #0) id 1BuBQM-000CMi-Ak by authid with plain; Mon, 09 Aug 2004 20:16:54 +0530 From: Shridhar Daithankar To: Paul Serby Subject: Re: The black art of postgresql.conf tweaking Date: Mon, 9 Aug 2004 20:16:47 +0530 User-Agent: KMail/1.6.2 Cc: pgsql-performance@postgresql.org References: <4110DA83.7020505@clockltd.com> <411789F1.6020305@clockltd.com> In-Reply-To: <411789F1.6020305@clockltd.com> MIME-Version: 1.0 Content-Disposition: inline Organization: Persistent Systems Pvt. Ltd. Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200408092016.47304.shridhar@frodo.hserus.net> X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/111 X-Sequence-Number: 7747 On Monday 09 Aug 2004 7:58 pm, Paul Serby wrote: > I've not maxed out the connections since making the changes, but I'm > still not convinced everything is running as well as it could be. I've > got some big result sets that need sorting and I'm sure I could spare a > bit more sort memory. You could set the sort mem for that connection before issuing the query. i.e. # set sort_mem=20000; # select * ....; And reset it back. Setting it globally is not that good. If you do it selectively, that would tune it as per your needs.. > Where does everyone get there information about the settings? I still > can't find anything that helps explain each of the settings and how you > determine there optimal settings. http://www.varlena.com/varlena/GeneralBits/Tidbits/annotated_conf_e.html http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html HTH Shridhar From pgsql-performance-owner@postgresql.org Mon Aug 9 12:30:19 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 49E8314B27FB for ; Mon, 9 Aug 2004 12:30:05 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 58454-07 for ; Mon, 9 Aug 2004 15:29:58 +0000 (GMT) Received: from Herge.rcsinc.local (mail.rcsonline.com [205.217.85.91]) by svr1.postgresql.org (Postfix) with ESMTP id 842E314B27FC for ; Mon, 9 Aug 2004 12:29:57 -0300 (ADT) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: tablespaces and ramdisks X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Date: Mon, 9 Aug 2004 11:29:57 -0400 Message-ID: <6EE64EF3AB31D5448D0007DD34EEB34101AF2C@Herge.rcsinc.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: tablespaces and ramdisks thread-index: AcR+JbnydD6RWPlcQHKi2t/PqHr15g== From: "Merlin Moncure" To: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/112 X-Sequence-Number: 7748 If you use tablespaces to put a high-update, non-critical table on a ramdisk, will updates to that table will still cause the WAL files to sync? I'm looking for a way to turn off syncing completely for a table. Temporary tables do this, but they can only be accessed from a single backend. Merlin From pgsql-performance-owner@postgresql.org Mon Aug 9 13:35:59 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 14FCF14B2821 for ; Mon, 9 Aug 2004 13:35:36 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 81971-04 for ; Mon, 9 Aug 2004 16:35:33 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id 04D8914B280B for ; Mon, 9 Aug 2004 13:35:20 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.12.11/8.12.11) with ESMTP id i79GZBVB016004; Mon, 9 Aug 2004 12:35:11 -0400 (EDT) To: "Merlin Moncure" Cc: pgsql-performance@postgresql.org Subject: Re: tablespaces and ramdisks In-reply-to: <6EE64EF3AB31D5448D0007DD34EEB34101AF2C@Herge.rcsinc.local> References: <6EE64EF3AB31D5448D0007DD34EEB34101AF2C@Herge.rcsinc.local> Comments: In-reply-to "Merlin Moncure" message dated "Mon, 09 Aug 2004 11:29:57 -0400" Date: Mon, 09 Aug 2004 12:35:10 -0400 Message-ID: <16003.1092069310@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/113 X-Sequence-Number: 7749 "Merlin Moncure" writes: > If you use tablespaces to put a high-update, non-critical table on a > ramdisk, will updates to that table will still cause the WAL files to > sync? Sure. Postgres has no way of knowing that there's anything special about such a tablespace. > I'm looking for a way to turn off syncing completely for a table. There isn't one, and I'm not eager to invent one. regards, tom lane From pgsql-performance-owner@postgresql.org Tue Aug 10 14:43:24 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id B46A014B27FC for ; Mon, 9 Aug 2004 13:54:19 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 88620-06 for ; Mon, 9 Aug 2004 16:54:17 +0000 (GMT) Received: from pythagoras.zen.co.uk (pythagoras.zen.co.uk [212.23.3.140]) by svr1.postgresql.org (Postfix) with ESMTP id 1532514B280D for ; Mon, 9 Aug 2004 13:54:09 -0300 (ADT) Received: from [82.68.174.94] (helo=support.intercellsolutions.com) by pythagoras.zen.co.uk with esmtp (Exim 4.30) id 1BuDPR-0007In-Bt for pgsql-performance@postgresql.org; Mon, 09 Aug 2004 16:54:05 +0000 Received: from [192.168.0.233] (82-68-174-94.dsl.in-addr.zen.co.uk [82.68.174.94]) (authenticated bits=0) by support.intercellsolutions.com (8.12.8/8.12.8) with ESMTP id i79GgbS0027346 for ; Mon, 9 Aug 2004 17:42:37 +0100 Mime-Version: 1.0 (Apple Message framework v618) To: pgsql-performance@postgresql.org Message-Id: Content-Type: multipart/alternative; boundary=Apple-Mail-10--53392545 From: Paul Langard Subject: Slow select, insert, update Date: Mon, 9 Aug 2004 17:54:00 +0100 X-Mailer: Apple Mail (2.618) X-Intercell-MailScanner-Information: Please contact the ISP for more information X-Intercell-MailScanner: Found to be clean X-Intercell-MailScanner-SpamCheck: not spam, SpamAssassin (score=-4.9, required 4, BAYES_00 -4.90) X-Originating-Pythagoras-IP: [82.68.174.94] X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/125 X-Sequence-Number: 7761 --Apple-Mail-10--53392545 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; format=flowed Having trouble with one table (see time to count records below!). Fairly new to postgres so any help much appreciated. It only contains 9,106 records - as you can see from: select count(id) from project count 9106 1 row(s) Total runtime: 45,778.813 ms There are only 3 fields: id integer nextval('id'::text) projectnumber text description text There is one index: id_project_ukey CREATE UNIQUE INDEX id_project_ukey ON project USING btree (id) ... the database is regularly vaccuumed. --Apple-Mail-10--53392545 Content-Transfer-Encoding: 7bit Content-Type: text/enriched; charset=US-ASCII Having trouble with one table (see time to count records below!). Fairly new to postgres so any help much appreciated. It only contains 9,106 records - as you can see from: select count(id) from project Arialcount Arial9106 1 row(s) Total runtime: 45,778.813 ms There are only 3 fields: id integer nextval('id'::text) projectnumber text description text There is one index: id_project_ukey CREATE UNIQUE INDEX id_project_ukey ON project USING btree (id) ... the database is regularly vaccuumed. --Apple-Mail-10--53392545-- From pgsql-performance-owner@postgresql.org Mon Aug 9 13:59:27 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id B16E314B27FC for ; Mon, 9 Aug 2004 13:57:56 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 87808-09 for ; Mon, 9 Aug 2004 16:57:53 +0000 (GMT) Received: from campbell-lange.net (host0406.cammail.net [217.206.202.27]) by svr1.postgresql.org (Postfix) with ESMTP id 915E414B2868 for ; Mon, 9 Aug 2004 13:57:16 -0300 (ADT) Received: from [213.78.150.90] (helo=roz) by host0406 with asmtp (Exim 4.34) id 1BuDYz-0006yk-An for pgsql-performance@postgresql.org; Mon, 09 Aug 2004 18:03:57 +0100 Received: from rory by roz with local (Exim 4.34) id 1BuDSD-0003ym-CF for pgsql-performance@postgresql.org; Mon, 09 Aug 2004 17:56:57 +0100 Date: Mon, 9 Aug 2004 17:56:57 +0100 From: Rory Campbell-Lange To: pgsql-performance@postgresql.org Subject: Help specifying new machine Message-ID: <20040809165657.GB15169@campbell-lange.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.6+20040722i X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/114 X-Sequence-Number: 7750 I'm thinking of upgrading an existing dedicated server and colocating my own server. The server is used for prototype systems running Postgresql, php and apache. The largest database is presently under 10GB and I haven't had any major performance problems. We expect to have to host larger data sets in the next year and anticipate one or two databases reaching the 30GB mark in size. We write a lot of our webapps functionality using pl/pgsql. The present server is a 2GHz Pentium 4/512 KB cache with 2 software-raided ide disks (Maxtors) and 1GB of RAM. I have been offered the following 1U server which I can just about afford: 1U server Intel Xeon 2.8GHz 512K cache 1 512MB PC2100 DDR ECC Registered 2 80Gb SATA HDD 4 4 port SATA card, 3 ware 8506-4 1 3 year next-day hardware warranty 1 There is an option for dual CPUs. I intend to install the system (Debian testing) on the first disk and run the other 3 disks under RAID5 and ext3. I'm fairly ignorant about the issues relating to SATA vs SCSI and what the best sort of RAM is for ensuring good database performance. I don't require anything spectacular, just good speedy general performance. I imagine dedicating around 25% of RAM to Shared Memory and 2-4% for Sort memory. Comments and advice gratefully received. Rory -- Rory Campbell-Lange From pgsql-performance-owner@postgresql.org Mon Aug 9 17:08:58 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id B7BD114B27FF for ; Mon, 9 Aug 2004 17:08:54 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 44414-10 for ; Mon, 9 Aug 2004 20:08:45 +0000 (GMT) Received: from snowwhite.lulu.com (mail.lulu.com [66.193.5.50]) by svr1.postgresql.org (Postfix) with ESMTP id 4C64214B2800 for ; Mon, 9 Aug 2004 17:08:44 -0300 (ADT) Received: from [10.0.0.32] (meatwad.rdu.lulu.com [10.0.0.32]) (authenticated bits=0) by snowwhite.lulu.com (8.12.8/8.12.8) with ESMTP id i79K8UQR022183 (version=TLSv1/SSLv3 cipher=RC4-MD5 bits=128 verify=NO); Mon, 9 Aug 2004 16:08:31 -0400 Message-ID: <4117D9C8.5030207@lulu.com> Date: Mon, 09 Aug 2004 16:08:40 -0400 From: Bill Montgomery User-Agent: Mozilla Thunderbird 0.7 (X11/20040615) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rory Campbell-Lange Cc: pgsql-performance@postgresql.org Subject: Re: Help specifying new machine References: <20040809165657.GB15169@campbell-lange.net> In-Reply-To: <20040809165657.GB15169@campbell-lange.net> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/115 X-Sequence-Number: 7751 Rory, Rory Campbell-Lange wrote: >I'm thinking of upgrading an existing dedicated server and colocating my >own server. > >The server is used for prototype systems running Postgresql, php and >apache. The largest database is presently under 10GB and I haven't had >any major performance problems. We expect to have to host larger data >sets in the next year and anticipate one or two databases reaching the >30GB mark in size. We write a lot of our webapps functionality using >pl/pgsql. > >The present server is a 2GHz Pentium 4/512 KB cache with 2 >software-raided ide disks (Maxtors) and 1GB of RAM. > > >I have been offered the following 1U server which I can just about >afford: > >1U server >Intel Xeon 2.8GHz 512K cache 1 >512MB PC2100 DDR ECC Registered 2 >80Gb SATA HDD 4 >4 port SATA card, 3 ware 8506-4 1 >3 year next-day hardware warranty 1 > >There is an option for dual CPUs. > >I intend to install the system (Debian testing) on the first disk and >run the other 3 disks under RAID5 and ext3. > > If you are going to spend your money anywhere, spend it on your disk subsystem. More or less, depending on the application, the bottleneck in your database performance will be the number of random IO operations per second (IOPS) your disk subsystem can execute. If you've got the money, get the largest (i.e. most spindles) RAID 10 (striped and mirrored) you can buy. If your budget doesn't permit RAID 10, RAID 5 is probably your next best bet. >I'm fairly ignorant about the issues relating to SATA vs SCSI and what >the best sort of RAM is for ensuring good database performance. I don't >require anything spectacular, just good speedy general performance. > > Be sure that if you go with SATA over SCSI, the disk firmware does not lie about fsync(). Most consumer grade IDE disks will report to the OS that data is written to disk while it is still in the drive's cache. I don't know much about SATA disks, but I suspect they behave the same way. The problem with this is that if there is data that PostgreSQL thinks is written safely to disk, but is really still in the drive cache, and you lose power at that instant, you can find yourself with an inconsistent set of data that cannot be recovered from. SCSI disks, AFAIK, will always be truthful about fsync(), and you will never end up with data that you *thought* was written to disk, but gets lost on power failure. >I imagine dedicating around 25% of RAM to Shared Memory and 2-4% for >Sort memory. > > That is probably too much RAM to allocate to shm. Start with 10000 buffers, benchmark your app, and slowly work up from there. NOTE: This advice will likely change with the introduction of ARC (adaptive caching) in 8.0; for now what will happen is that a large read of an infrequently accessed index or table will blow away all your shared memory buffers, and you'll end up with 25% of your memory filled with useless data. Better to let the smarter filesystem cache handle the bulk of your caching needs. >Comments and advice gratefully received. >Rory > > > Best Luck, Bill Montgomery From pgsql-performance-owner@postgresql.org Mon Aug 9 21:06:14 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 1FEB414B2820 for ; Mon, 9 Aug 2004 21:06:01 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 07984-01 for ; Tue, 10 Aug 2004 00:05:58 +0000 (GMT) Received: from web13121.mail.yahoo.com (web13121.mail.yahoo.com [216.136.174.83]) by svr1.postgresql.org (Postfix) with SMTP id 6E27514B27FB for ; Mon, 9 Aug 2004 21:05:56 -0300 (ADT) Message-ID: <20040810000559.91562.qmail@web13121.mail.yahoo.com> Received: from [63.78.248.48] by web13121.mail.yahoo.com via HTTP; Mon, 09 Aug 2004 17:05:59 PDT Date: Mon, 9 Aug 2004 17:05:59 -0700 (PDT) From: Litao Wu Subject: insert waits for delete with trigger To: pgsql-performance@postgresql.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests=HOT_NASTY X-Spam-Level: X-Archive-Number: 200408/116 X-Sequence-Number: 7752 Hi all, We have table q_20040805 and a delete trigger on it. The delete trigger is: update table q_summary set count=count-1... When we delete from q_20040805, we also insert into related info q_process within the same transaction. There is a PK on q_process, but no trigger on it. No FK on either of the 3 tables. Here is info from pg_lock: relname | pid | mode | granted | current_query -------------------+-------+------------------+---------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- q_process | 14643 | RowExclusiveLock | t | DELETE FROM q_20040805 WHERE domain_id='20237906' AND module='spam' q_summary | 14643 | RowExclusiveLock | t | DELETE FROM q_20040805 WHERE domain_id='20237906' AND module='spam' q_20040805 | 14643 | RowExclusiveLock | t | DELETE FROM q_20040805 WHERE domain_id='20237906' AND module='spam' q_process | 18951 | RowExclusiveLock | t | INSERT INTO q_process (...) SELECT ... FROM q_20040805 WHERE domain_id='20237906' AND module='spam' From ps command, it is easy to see another insert is waiting: ps -elfww|grep 18951 040 S postgres 18951 870 0 69 0 - 81274 semtim 16:34 ? 00:00:00 postgres: postgres mxl xxx.xxx.x.xxx:49986 INSERT waiting ps -elfww|grep 14643 040 S postgres 14643 870 79 70 0 - 81816 semtim 15:56 ? 00:44:02 postgres: postgres mxl xxx.xxx.x.xxx:47236 DELETE I do not understand why process 18951 (insert) is waiting (subqery SELECT of INSERT INTO is not a problem as I know) PG version is: 7.3.2 Can someone explain? Thanks, __________________________________ Do you Yahoo!? New and Improved Yahoo! Mail - Send 10MB messages! http://promotions.yahoo.com/new_mail From pgsql-performance-owner@postgresql.org Mon Aug 9 21:31:55 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id D48D214B2800 for ; Mon, 9 Aug 2004 21:31:49 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 14194-01 for ; Tue, 10 Aug 2004 00:31:41 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id 8A5F314B27FB for ; Mon, 9 Aug 2004 21:31:40 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.12.11/8.12.11) with ESMTP id i7A0VhVU022224; Mon, 9 Aug 2004 20:31:43 -0400 (EDT) To: Litao Wu Cc: pgsql-performance@postgresql.org Subject: Re: insert waits for delete with trigger In-reply-to: <20040810000559.91562.qmail@web13121.mail.yahoo.com> References: <20040810000559.91562.qmail@web13121.mail.yahoo.com> Comments: In-reply-to Litao Wu message dated "Mon, 09 Aug 2004 17:05:59 -0700" Date: Mon, 09 Aug 2004 20:31:43 -0400 Message-ID: <22223.1092097903@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/117 X-Sequence-Number: 7753 Litao Wu writes: > Here is info from pg_lock: All those locks are already granted, so they are not much help in understanding what PID 18951 is waiting for. What row does it have with granted = 'f' ? regards, tom lane From pgsql-performance-owner@postgresql.org Tue Aug 10 01:36:00 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 4631614B281A for ; Tue, 10 Aug 2004 01:35:59 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 34883-03 for ; Tue, 10 Aug 2004 04:35:57 +0000 (GMT) Received: from web13124.mail.yahoo.com (web13124.mail.yahoo.com [216.136.174.142]) by svr1.postgresql.org (Postfix) with SMTP id 8344114B280B for ; Tue, 10 Aug 2004 01:35:55 -0300 (ADT) Message-ID: <20040810043555.38371.qmail@web13124.mail.yahoo.com> Received: from [24.9.238.30] by web13124.mail.yahoo.com via HTTP; Mon, 09 Aug 2004 21:35:55 PDT Date: Mon, 9 Aug 2004 21:35:55 -0700 (PDT) From: Litao Wu Subject: Re: insert waits for delete with trigger To: Tom Lane Cc: pgsql-performance@postgresql.org In-Reply-To: <22223.1092097903@sss.pgh.pa.us> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/118 X-Sequence-Number: 7754 Hi Tom, No row has granted='f'. The result shown in the original email is from: select c.relname, l.pid, l.mode, l.granted, current_query from pg_locks l, pg_class c, pg_stat_activity a where relation is not null AND l.relation = c.oid AND l.pid = a.procpid AND l.mode != 'AccessShareLock' order by l.pid; After the above result, I went to OS to get ps status. Did I miss something? Since the lock was granted to pid (18951), that cause me confuse why OS ps shows it is waiting. Also, I ntoiced that insert will be finished almost immediately after delete is done. Thanks, --- Tom Lane wrote: > Litao Wu writes: > > Here is info from pg_lock: > > All those locks are already granted, so they are not > much help in > understanding what PID 18951 is waiting for. What > row does it have > with granted = 'f' ? > > regards, tom lane > > ---------------------------(end of > broadcast)--------------------------- > TIP 7: don't forget to increase your free space map > settings > __________________________________ Do you Yahoo!? Yahoo! Mail is new and improved - Check it out! http://promotions.yahoo.com/new_mail From pgsql-performance-owner@postgresql.org Tue Aug 10 01:41:37 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 53ED114B281B for ; Tue, 10 Aug 2004 01:41:36 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 60323-01 for ; Tue, 10 Aug 2004 04:41:35 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id 4846514B280D for ; Tue, 10 Aug 2004 01:41:33 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.12.11/8.12.11) with ESMTP id i7A4fXcW024198; Tue, 10 Aug 2004 00:41:33 -0400 (EDT) To: Litao Wu Cc: pgsql-performance@postgresql.org Subject: Re: insert waits for delete with trigger In-reply-to: <20040810043555.38371.qmail@web13124.mail.yahoo.com> References: <20040810043555.38371.qmail@web13124.mail.yahoo.com> Comments: In-reply-to Litao Wu message dated "Mon, 09 Aug 2004 21:35:55 -0700" Date: Tue, 10 Aug 2004 00:41:33 -0400 Message-ID: <24197.1092112893@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/119 X-Sequence-Number: 7755 Litao Wu writes: > Did I miss something? Your join omits all transaction locks. regards, tom lane From pgsql-performance-owner@postgresql.org Tue Aug 10 10:39:31 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id F34B214B2806 for ; Tue, 10 Aug 2004 10:39:27 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 79926-09 for ; Tue, 10 Aug 2004 13:39:24 +0000 (GMT) Received: from snowwhite.lulu.com (mail.lulu.com [66.193.5.50]) by svr1.postgresql.org (Postfix) with ESMTP id B043814B27FF for ; Tue, 10 Aug 2004 10:39:20 -0300 (ADT) Received: from [10.0.0.32] (meatwad.rdu.lulu.com [10.0.0.32]) (authenticated bits=0) by snowwhite.lulu.com (8.12.8/8.12.8) with ESMTP id i7ADdBQR003010 (version=TLSv1/SSLv3 cipher=RC4-MD5 bits=128 verify=NO) for ; Tue, 10 Aug 2004 09:39:11 -0400 Message-ID: <4118D008.1070606@lulu.com> Date: Tue, 10 Aug 2004 09:39:20 -0400 From: Bill Montgomery User-Agent: Mozilla Thunderbird 0.7 (X11/20040615) X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Column order performance Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/120 X-Sequence-Number: 7756 Does the order of columns of varying size have any effect on SELECT/INSERT/UPDATE/and/or/DELETE performance? Take the example where an integer primary key is listed first in the table and alternatively listed after some large varchar or text columns? For example, is this different performance-wise: CREATE TABLE foo ( foo_id serial, foo_data varchar(8000), primary key (foo_id) ); from this? CREATE TABLE bar ( bar_data varchar(8000), bar_id serial, primary key (bar_id) ); My suspicion is it would never make a difference since the index will be searched when querying "WHERE [foo|bar]_id=?" (as long as the planner decides to use the index). What about a case where a sequential scan _must_ be performed? Could the order of columns make a difference in the number of pages read/written if there is a mix of small and large columns? Thanks for your help. Best Regards, Bill Montgomery From pgsql-performance-owner@postgresql.org Tue Aug 10 12:45:15 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 550A214B280B for ; Tue, 10 Aug 2004 11:35:54 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 05005-09 for ; Tue, 10 Aug 2004 14:35:43 +0000 (GMT) Received: from sphinx.mythic-beasts.com (sphinx.mythic-beasts.com [212.69.37.6]) by svr1.postgresql.org (Postfix) with ESMTP id D7FB414B281D for ; Tue, 10 Aug 2004 11:35:31 -0300 (ADT) Received: from xelah (helo=localhost) by sphinx.mythic-beasts.com with local-esmtp (Exim 3.33 #3) id 1BuXit-0006so-00 for pgsql-performance@postgresql.org; Tue, 10 Aug 2004 15:35:31 +0100 Date: Tue, 10 Aug 2004 15:35:31 +0100 (BST) From: Alex Hayward X-X-Sender: xelah@sphinx.mythic-beasts.com To: 'PostgreSQL Performance' Subject: Re: Performance Bottleneck In-Reply-To: <007f01c47d54$233b4bf0$8300a8c0@solent> Message-ID: References: <007f01c47d54$233b4bf0$8300a8c0@solent> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/122 X-Sequence-Number: 7758 On Sun, 8 Aug 2004, Matt Clark wrote: > > And this is exactly where the pgpool advantage lies. > > Especially with the > > TPC-W, the Apache is serving a mix of PHP (or whatever CGI > > technique is > > used) and static content like images. Since the 200+ Apache > > kids serve > > any of that content by random and the emulated browsers very much > > encourage it to ramp up MaxClients children by using up to 4 > > concurrent > > image connections, one does end up with MaxClients DB > > connections that > > are all relatively low frequently used. In contrast to that the real > > pgpool causes lesser, more active DB connections, which is better for > > performance. > > There are two well-worn and very mature techniques for dealing with the > issue of web apps using one DB connection per apache process, both of which > work extremely well and attack the issue at its source. > > 1) Use a front-end caching proxy like Squid as an accelerator. Static > content will be served by the accelerator 99% of the time. Additionally, > large pages can be served immediately to the accelerator by Apache, which > can then go on to serve another request without waiting for the end user's > dial-up connection to pull the data down. Massive speedup, fewer apache > processes needed. Squid also takes away the work of doing SSL (presuming you're running it on a different machine). Unfortunately it doesn't support HTTP/1.1 which means that most generated pages (those that don't set Content-length) end up forcing squid to close and then reopen the connection to the web server. Because you no longer need to worry about keeping Apache processes around to dribble data to people on the wrong end of modems you can reduce MaxClients quite a bit (to, say, 10 or 20 per web server). This keeps the number of PostgreSQL connections down. I'd guess that above some point you're going to reduce performance by increasing MaxClients and running queries in parallel rather than queueing the request and doing them serially. I've also had some problems when Squid had a large number of connections open (several thousand); though that may have been because of my half_closed_clients setting. Squid 3 coped a lot better when I tried it (quite a few months ago now - and using FreeBSD and the special kqueue system call) but crashed under some (admittedly synthetic) conditions. > I'm sure pgpool and the like have their place, but being band-aids for > poorly configured websites probably isn't the best use for them. You still have periods of time when the web servers are busy using their CPUs to generate HTML rather than waiting for database queries. This is especially true if you cache a lot of data somewhere on the web servers themselves (which, in my experience, reduces the database load a great deal). If you REALLY need to reduce the number of connections (because you have a large number of web servers doing a lot of computation, say) then it might still be useful. From pgsql-performance-owner@postgresql.org Tue Aug 10 11:54:11 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3A64314B281A for ; Tue, 10 Aug 2004 11:48:58 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 07206-07 for ; Tue, 10 Aug 2004 14:48:44 +0000 (GMT) Received: from web13126.mail.yahoo.com (web13126.mail.yahoo.com [216.136.174.163]) by svr1.postgresql.org (Postfix) with SMTP id 9155314B2825 for ; Tue, 10 Aug 2004 11:48:37 -0300 (ADT) Message-ID: <20040810144838.72955.qmail@web13126.mail.yahoo.com> Received: from [63.78.248.48] by web13126.mail.yahoo.com via HTTP; Tue, 10 Aug 2004 07:48:38 PDT Date: Tue, 10 Aug 2004 07:48:38 -0700 (PDT) From: Litao Wu Subject: Re: insert waits for delete with trigger To: Tom Lane Cc: pgsql-performance@postgresql.org In-Reply-To: <24197.1092112893@sss.pgh.pa.us> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/121 X-Sequence-Number: 7757 Thank you. How about: select c.relname, l.pid, l.mode, l.granted, a.current_query from pg_locks l, pg_class c, pg_stat_activity a where l.relation = c.oid AND l.pid = a.procpid order by l.granted, l.pid; relname | pid | mode | granted | current_query -----------------------------------+-------+------------------+---------+----------------------------------------------- ------------------------------------------------------------------------------------------------------------------------ --------------------------------------------------------------------------------- q_20040810 | 488 | AccessShareLock | t | q_20040810 | 488 | RowExclusiveLock | t | q_process | 3729 | AccessShareLock | t | DELETE FROM q_20040805 WHERE domain_id ='2005761066' AND module='spam' q_process | 3729 | RowExclusiveLock | t | DELETE FROM q_20040805 WHERE domain_id ='2005761066' AND module='spam' q_20040805 | 3729 | AccessShareLock | t | DELETE FROM q_20040805 WHERE domain_id ='2005761066' AND module='spam' q_20040805 | 3729 | RowExclusiveLock | t | DELETE FROM q_20040805 WHERE domain_id ='2005761066' AND module='spam' q_summary | 3729 | AccessShareLock | t | DELETE FROM q_20040805 WHERE domain_id ='2005761066' AND module='spam' q_summary | 3729 | RowExclusiveLock | t | DELETE FROM q_20040805 WHERE domain_id ='2005761066' AND module='spam' q_summary_did_dir_idx | 3729 | AccessShareLock | t | DELETE FROM q_20040805 WHERE domain_id ='2005761066' AND module='spam' pg_shadow | 7660 | AccessShareLock | t | pg_locks | 7660 | AccessShareLock | t | pg_database | 7660 | AccessShareLock | t | pg_class | 7660 | AccessShareLock | t | pg_stat_activity | 7660 | AccessShareLock | t | pg_class_oid_index | 7660 | AccessShareLock | t | q_process | 8593 | AccessShareLock | t | DELETE FROM q_20040810 WHERE domain_id ='2002300623' AND module='spam' q_process | 8593 | RowExclusiveLock | t | DELETE FROM q_20040810 WHERE domain_id ='2002300623' AND module='spam' q_20040810 | 8593 | AccessShareLock | t | DELETE FROM q_20040810 WHERE domain_id ='2002300623' AND module='spam' q_20040810 | 8593 | RowExclusiveLock | t | DELETE FROM q_20040810 WHERE domain_id ='2002300623' AND module='spam' q_summary | 8593 | AccessShareLock | t | DELETE FROM q_20040810 WHERE domain_id ='2002300623' AND module='spam' q_summary | 8593 | RowExclusiveLock | t | DELETE FROM q_20040810 WHERE domain_id ='2002300623' AND module='spam' q_summary_did_dir_idx | 8593 | AccessShareLock | t | DELETE FROM q_20040810 WHERE domain_id ='2002300623' AND module='spam' q_process | 19027 | AccessShareLock | t | INSERT INTO q_process (...) SELECT ... FROM q_20040805 WHERE domain_id='2005761066' AND module='spam' q_process | 19027 | RowExclusiveLock | t | INSERT INTO q_process (...) SELECT ... FROM q_20040805 WHERE domain_id='2005761066' AND module='spam' q_20040805 | 19027 | AccessShareLock | t | INSERT INTO q_process (...) SELECT ... FROM q_20040805 WHERE domain_id='2005761066' AND module='spam' q_did_mod_dir_20040805_idx | 19027 | AccessShareLock | t | INSERT INTO q_process (...) SELECT ... FROM q_20040805 WHERE domain_id='2005761066' AND module='spam' (26 rows) ps -elfww|grep 19027 040 S postgres 19027 870 1 69 0 - 81290 semtim 07:31 ? 00:00:51 postgres: postgres mxl 192.168.0.177:38266 INSERT waiting --- Tom Lane wrote: > Litao Wu writes: > > Did I miss something? > > Your join omits all transaction locks. > > regards, tom lane > __________________________________ Do you Yahoo!? Yahoo! Mail - 50x more storage than other providers! http://promotions.yahoo.com/new_mail From pgsql-performance-owner@postgresql.org Tue Aug 10 13:31:54 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 496C614B27FC for ; Tue, 10 Aug 2004 12:26:09 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 24261-01 for ; Tue, 10 Aug 2004 15:25:58 +0000 (GMT) Received: from Herge.rcsinc.local (mail.rcsonline.com [205.217.85.91]) by svr1.postgresql.org (Postfix) with ESMTP id 275FC14B2820 for ; Tue, 10 Aug 2004 12:25:51 -0300 (ADT) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: Re: [HACKERS] fsync vs open_sync X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 Date: Tue, 10 Aug 2004 11:25:15 -0400 Message-ID: <6EE64EF3AB31D5448D0007DD34EEB3412A7446@Herge.rcsinc.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [HACKERS] fsync vs open_sync thread-index: AcR+PTvsPyd0oLNMSpuRU9Hwk6sV/gAsMMOQ From: "Merlin Moncure" To: Cc: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/123 X-Sequence-Number: 7759 > Anyway, with fsync enabled using standard fsync(), I get roughly 300-400 > inserts per second. With fsync disabled, I get about 7000 inserts per > second. When I re-enable fsync but use the open_sync option, I can get > about 2500 inserts per second. You are getting 300-400 inserts/sec with fsync on? If you don't mind me asking, what's your hardware? (also, have you checked fsync on #s with the new bgwriter in 7.5?) Merlin From pgsql-performance-owner@postgresql.org Tue Aug 10 14:46:56 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 37EA614B281B for ; Tue, 10 Aug 2004 12:37:57 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 27846-06 for ; Tue, 10 Aug 2004 15:37:52 +0000 (GMT) Received: from outland.mohawksoft.com (unknown [64.46.156.80]) by svr1.postgresql.org (Postfix) with ESMTP id 92FF114B281A for ; Tue, 10 Aug 2004 12:37:47 -0300 (ADT) Received: (from mohawk@localhost) by outland.mohawksoft.com (8.11.6/8.11.6) id i7AFsSO09616; Tue, 10 Aug 2004 11:54:28 -0400 From: pgsql@mohawksoft.com X-Authentication-Warning: outland.mohawksoft.com: mohawk set sender to pgsql@mohawksoft.com using -f Received: from 64.119.142.34 (SquirrelMail authenticated user pgsql) by mail.mohawksoft.com with HTTP; Tue, 10 Aug 2004 11:54:28 -0400 (EDT) Message-ID: <15691.64.119.142.34.1092153268.squirrel@mail.mohawksoft.com> In-Reply-To: <6EE64EF3AB31D5448D0007DD34EEB3412A7446@Herge.rcsinc.local> References: <6EE64EF3AB31D5448D0007DD34EEB3412A7446@Herge.rcsinc.local> Date: Tue, 10 Aug 2004 11:54:28 -0400 (EDT) Subject: Re: [HACKERS] fsync vs open_sync To: "Merlin Moncure" Cc: pgsql-performance@postgresql.org User-Agent: SquirrelMail/1.4.2 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Priority: 3 Importance: Normal X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=1.1 tagged_above=0.0 required=5.0 tests=NO_REAL_NAME, PRIORITY_NO_NAME X-Spam-Level: * X-Archive-Number: 200408/126 X-Sequence-Number: 7762 >> Anyway, with fsync enabled using standard fsync(), I get roughly > 300-400 >> inserts per second. With fsync disabled, I get about 7000 inserts per >> second. When I re-enable fsync but use the open_sync option, I can get >> about 2500 inserts per second. > > You are getting 300-400 inserts/sec with fsync on? If you don't mind me > asking, what's your hardware? (also, have you checked fsync on #s with > the new bgwriter in 7.5?) > 300 inserts persecond with fsync on using fdatasync. 2500 inserts per second with fsync on using open_sync. [mwoodward@penguin-021 mwoodward]$ cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 15 model : 2 model name : Intel(R) Xeon(TM) CPU 2.40GHz stepping : 5 cpu MHz : 2399.373 cache size : 512 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid bogomips : 4784.12 Linux node1 2.4.25 #1 Mon Mar 22 13:33:41 EST 2004 i686 i686 i386 GNU/Linux ide2: BM-DMA at 0xc400-0xc407, BIOS settings: hde:pio, hdf:pio hde: Maxtor 6Y200P0, ATA DISK drive hde: attached ide-disk driver. hde: host protected area => 1 hde: 398297088 sectors (203928 MB) w/7936KiB Cache, CHS=24792/255/63, UDMA(100) PDC20268: IDE controller at PCI slot 06:05.0 From pgsql-performance-owner@postgresql.org Tue Aug 10 21:38:29 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id B4A1414B281C for ; Tue, 10 Aug 2004 13:53:28 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 42082-01 for ; Tue, 10 Aug 2004 16:53:13 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id 5D80814B2820 for ; Tue, 10 Aug 2004 13:53:11 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.12.11/8.12.11) with ESMTP id i7AGrA0k029339; Tue, 10 Aug 2004 12:53:10 -0400 (EDT) To: Litao Wu Cc: pgsql-performance@postgresql.org Subject: Re: insert waits for delete with trigger In-reply-to: <20040810144838.72955.qmail@web13126.mail.yahoo.com> References: <20040810144838.72955.qmail@web13126.mail.yahoo.com> Comments: In-reply-to Litao Wu message dated "Tue, 10 Aug 2004 07:48:38 -0700" Date: Tue, 10 Aug 2004 12:53:10 -0400 Message-ID: <29338.1092156790@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/135 X-Sequence-Number: 7771 Litao Wu writes: > How about: > select c.relname, l.pid, l.mode, l.granted, > a.current_query > from pg_locks l, pg_class c, pg_stat_activity a > where > l.relation = c.oid > AND l.pid = a.procpid > order by l.granted, l.pid; You can't join to pg_class without eliminating the transaction lock rows (because they have NULLs in the relation field). regards, tom lane From pgsql-performance-owner@postgresql.org Tue Aug 10 21:05:45 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 149ED14B281C for ; Tue, 10 Aug 2004 14:19:07 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 66847-07 for ; Tue, 10 Aug 2004 17:18:59 +0000 (GMT) Received: from davinci.ethosmedia.com (server226.ethosmedia.com [209.128.84.226]) by svr1.postgresql.org (Postfix) with ESMTP id 669AE14B281A for ; Tue, 10 Aug 2004 14:18:51 -0300 (ADT) Received: from [63.195.55.98] (HELO spooky) by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 6042550; Tue, 10 Aug 2004 10:20:02 -0700 Content-Type: text/plain; charset="iso-8859-1" From: Josh Berkus Organization: Aglio Database Solutions To: "Merlin Moncure" , Subject: Re: [HACKERS] fsync vs open_sync Date: Tue, 10 Aug 2004 10:18:32 -0700 User-Agent: KMail/1.4.3 Cc: References: <6EE64EF3AB31D5448D0007DD34EEB3412A7446@Herge.rcsinc.local> In-Reply-To: <6EE64EF3AB31D5448D0007DD34EEB3412A7446@Herge.rcsinc.local> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <200408101018.32327.josh@agliodbs.com> X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/134 X-Sequence-Number: 7770 Guys, just so you know: OSDL did some testing and found Ext3 to be perhaps the worst FS for PostgreSQL -- although this testing was with the default options. Ext3 involved an almost 40% write performance penalty compared with Ext2, whereas the penalty for ReiserFS and JFS was less than 10%. This concurs with my personal experience. -- Josh Berkus Aglio Database Solutions San Francisco From pgsql-performance-owner@postgresql.org Tue Aug 10 21:05:22 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id A564014B281A for ; Tue, 10 Aug 2004 14:23:48 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 78011-07 for ; Tue, 10 Aug 2004 17:23:46 +0000 (GMT) Received: from davinci.ethosmedia.com (server226.ethosmedia.com [209.128.84.226]) by svr1.postgresql.org (Postfix) with ESMTP id 0BC6014B2800 for ; Tue, 10 Aug 2004 14:23:44 -0300 (ADT) Received: from [63.195.55.98] (HELO spooky) by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 6042583; Tue, 10 Aug 2004 10:24:57 -0700 Content-Type: text/plain; charset="iso-8859-1" From: Josh Berkus Organization: Aglio Database Solutions To: Bill Montgomery , pgsql-performance@postgresql.org Subject: Re: Column order performance Date: Tue, 10 Aug 2004 10:23:28 -0700 User-Agent: KMail/1.4.3 References: <4118D008.1070606@lulu.com> In-Reply-To: <4118D008.1070606@lulu.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <200408101023.28084.josh@agliodbs.com> X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/133 X-Sequence-Number: 7769 Bill, > Does the order of columns of varying size have any effect on > SELECT/INSERT/UPDATE/and/or/DELETE performance? Take the example where > an integer primary key is listed first in the table and alternatively > listed after some large varchar or text columns? No, the "order" of the columns in the table makes no difference. They are not physically stored in the metadata order, anyway; on the data pages, fixed-length fields (e.g. INT, BOOLEAN, etc.) are stored first and variable-length fields (CHAR, TEXT, NUMERIC) after them, AFAIK. The only thing I have seen elusive reports of is that *display* speed can be afffected by column order (e.g. when you call the query to the command line with many rows) but I've not seen this proven in a test case. -- Josh Berkus Aglio Database Solutions San Francisco From pgsql-performance-owner@postgresql.org Fri Aug 13 12:37:17 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id A748514B281E for ; Tue, 10 Aug 2004 14:48:24 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 43532-03 for ; Tue, 10 Aug 2004 17:48:19 +0000 (GMT) Received: from outland.mohawksoft.com (unknown [64.46.156.80]) by svr1.postgresql.org (Postfix) with ESMTP id CCA2D14B2827 for ; Tue, 10 Aug 2004 14:48:12 -0300 (ADT) Received: (from mohawk@localhost) by outland.mohawksoft.com (8.11.6/8.11.6) id i7AI4rQ11357; Tue, 10 Aug 2004 14:04:53 -0400 From: pgsql@mohawksoft.com X-Authentication-Warning: outland.mohawksoft.com: mohawk set sender to pgsql@mohawksoft.com using -f Received: from 64.119.142.34 (SquirrelMail authenticated user pgsql) by mail.mohawksoft.com with HTTP; Tue, 10 Aug 2004 14:04:52 -0400 (EDT) Message-ID: <33646.64.119.142.34.1092161092.squirrel@mail.mohawksoft.com> In-Reply-To: <200408101018.32327.josh@agliodbs.com> References: <6EE64EF3AB31D5448D0007DD34EEB3412A7446@Herge.rcsinc.local> <200408101018.32327.josh@agliodbs.com> Date: Tue, 10 Aug 2004 14:04:52 -0400 (EDT) Subject: Re: [HACKERS] fsync vs open_sync To: "Josh Berkus" Cc: "Merlin Moncure" , pgsql-performance@postgresql.org User-Agent: SquirrelMail/1.4.2 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Priority: 3 Importance: Normal X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=1.1 tagged_above=0.0 required=5.0 tests=NO_REAL_NAME, PRIORITY_NO_NAME X-Spam-Level: * X-Archive-Number: 200408/207 X-Sequence-Number: 7843 > Guys, just so you know: > > OSDL did some testing and found Ext3 to be perhaps the worst FS for > PostgreSQL > -- although this testing was with the default options. Ext3 involved an > almost 40% write performance penalty compared with Ext2, whereas the > penalty > for ReiserFS and JFS was less than 10%. > > This concurs with my personal experience. I had exactly the same experience From pgsql-performance-owner@postgresql.org Tue Aug 10 20:54:58 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id CFD6C14B281C for ; Tue, 10 Aug 2004 15:18:12 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 00633-09 for ; Tue, 10 Aug 2004 18:18:10 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id C700B14B2821 for ; Tue, 10 Aug 2004 15:18:07 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.12.11/8.12.11) with ESMTP id i7AII64P000182; Tue, 10 Aug 2004 14:18:06 -0400 (EDT) To: Paul Langard Cc: pgsql-performance@postgresql.org Subject: Re: Slow select, insert, update In-reply-to: References: Comments: In-reply-to Paul Langard message dated "Mon, 09 Aug 2004 17:54:00 +0100" Date: Tue, 10 Aug 2004 14:18:05 -0400 Message-ID: <181.1092161885@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/132 X-Sequence-Number: 7768 Paul Langard writes: > select count(id) from project > count > 9106 > 1 row(s) > Total runtime: 45,778.813 ms Yipes. The only explanation I can think of is tremendous table bloat. What do you get from "vacuum verbose project" --- in particular, how many pages in the table? > ... the database is regularly vaccuumed. Not regularly enough, perhaps ... or else you need to increase the free space map size parameters. In any case you'll probably need to do one round of "vacuum full" to get this table back within bounds. regards, tom lane From pgsql-performance-owner@postgresql.org Tue Aug 10 20:20:27 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id A327C14B2804 for ; Tue, 10 Aug 2004 15:49:45 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 28439-09 for ; Tue, 10 Aug 2004 18:49:39 +0000 (GMT) Received: from snowwhite.lulu.com (mail.lulu.com [66.193.5.50]) by svr1.postgresql.org (Postfix) with ESMTP id 7935B14B2800 for ; Tue, 10 Aug 2004 15:49:33 -0300 (ADT) Received: from [10.0.0.32] (meatwad.rdu.lulu.com [10.0.0.32]) (authenticated bits=0) by snowwhite.lulu.com (8.12.8/8.12.8) with ESMTP id i7AInKQR007314 (version=TLSv1/SSLv3 cipher=RC4-MD5 bits=128 verify=NO) for ; Tue, 10 Aug 2004 14:49:20 -0400 Message-ID: <411918B9.9000707@lulu.com> Date: Tue, 10 Aug 2004 14:49:29 -0400 From: Bill Montgomery User-Agent: Mozilla Thunderbird 0.7 (X11/20040615) X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: Column order performance References: <4118D008.1070606@lulu.com> <200408101023.28084.josh@agliodbs.com> In-Reply-To: <200408101023.28084.josh@agliodbs.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/131 X-Sequence-Number: 7767 Josh Berkus wrote: >>Does the order of columns of varying size have any effect on >>SELECT/INSERT/UPDATE/and/or/DELETE performance? Take the example where >>an integer primary key is listed first in the table and alternatively >>listed after some large varchar or text columns? >> >> > >No, the "order" of the columns in the table makes no difference. They are not >physically stored in the metadata order, anyway; on the data pages, >fixed-length fields (e.g. INT, BOOLEAN, etc.) are stored first and >variable-length fields (CHAR, TEXT, NUMERIC) after them, AFAIK. > > Is this true even after a table is altered to "append" say, an integer column, after there are already variable-length columns in the table? -Bill From pgsql-performance-owner@postgresql.org Tue Aug 10 20:12:14 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id D593114B2800 for ; Tue, 10 Aug 2004 15:56:45 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 30228-08 for ; Tue, 10 Aug 2004 18:56:35 +0000 (GMT) Received: from snowwhite.lulu.com (mail.lulu.com [66.193.5.50]) by svr1.postgresql.org (Postfix) with ESMTP id 6CA2A14B2869 for ; Tue, 10 Aug 2004 15:56:32 -0300 (ADT) Received: from [10.0.0.32] (meatwad.rdu.lulu.com [10.0.0.32]) (authenticated bits=0) by snowwhite.lulu.com (8.12.8/8.12.8) with ESMTP id i7AIuJQR007420 (version=TLSv1/SSLv3 cipher=RC4-MD5 bits=128 verify=NO); Tue, 10 Aug 2004 14:56:19 -0400 Message-ID: <41191A5C.7020409@lulu.com> Date: Tue, 10 Aug 2004 14:56:28 -0400 From: Bill Montgomery User-Agent: Mozilla Thunderbird 0.7 (X11/20040615) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Paul Langard Cc: pgsql-performance@postgresql.org Subject: Re: Slow select, insert, update References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/130 X-Sequence-Number: 7766 Paul, Paul Langard wrote: > Having trouble with one table (see time to count records below!). > > Fairly new to postgres so any help much appreciated. > > It only contains 9,106 records - as you can see from: > > > select count(id) from project > > *count > *9106 > 1 row(s) > Total runtime: 45,778.813 ms > ... the database is regularly vaccuumed. Have you tried doing a VACUUM FULL, CLUSTER, or drop/restore on the table? This sounds symptomatic of a table with a bunch of dead tuples not in the FSM (free space map). Only tuples in the FSM are reclaimed by a regular VACUUM. If your FSM parameters in postgresql.conf are not big enough for your ratio of UPDATE/DELETE operations to VACUUM frequency, you will end up with dead tuples that will only be reclaimed by a VACUUM FULL. To prevent this problem in the future, look at increasing your FSM size and possibly vacuuming more frequently or using pg_autovacuum. Good Luck, Bill Montgomery From pgsql-performance-owner@postgresql.org Tue Aug 10 19:53:20 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 99B5514B280B for ; Tue, 10 Aug 2004 16:17:43 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 35908-10 for ; Tue, 10 Aug 2004 19:17:37 +0000 (GMT) Received: from mail.gotfrag.com (g01.gotfrag.com [66.208.110.11]) by svr1.postgresql.org (Postfix) with ESMTP id A7B2814B2806 for ; Tue, 10 Aug 2004 16:17:31 -0300 (ADT) Received: from jcoene2 (roc-66-66-149-175.rochester.rr.com [66.66.149.175]) by mail.gotfrag.com (8.12.10/8.12.8) with ESMTP id i7AJHR0E064106; Tue, 10 Aug 2004 15:17:27 -0400 (EDT) (envelope-from jcoene@gotfrag.com) Message-Id: <200408101917.i7AJHR0E064106@mail.gotfrag.com> From: "Jason Coene" To: Subject: Hardware upgrade for a high-traffic database Date: Tue, 10 Aug 2004 15:17:32 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook, Build 11.0.5510 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2096 Thread-Index: AcR/DohI0d8i83OnRFGAWtmzaprLpg== X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/129 X-Sequence-Number: 7765 Hi All, We're currently running Postgres 7.4.1 on FreeBSD 5.2, a Dual Xeon 2.4, 2GB ECC, 3Ware Serial ATA RAID 5 w/ 4 disks (SLOW!!). Our database is about 20GB on disk, we have some quite large tables - 2M rows with TEXT fields in a sample table, accessed constantly. We average about 4,000 - 5,000 queries per second - all from web traffic. As you can imagine, we're quite disk limited and checkpoints can be killer. Additionally, we see queries and connections getting serialized due to queries that take a long time (5 sec or so) while waiting on disk access. No fun at all. We've tweaked everything long and hard, and at the end of the day, the disk is killing us. We're looking to upgrade our server - or rather, replace it as it has no upgrade path to SCSI. I'm considering going Opteron (though right now we don't need more CPU time), and am looking for suggestions on what an optimal RAID configuration may look like (disks, controller, cache setting). We're in the market to buy right now - any good vendor suggestions? I'd appreciate any input, thanks! Jason From pgsql-performance-owner@postgresql.org Tue Aug 10 19:01:51 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 85E1314B2804 for ; Tue, 10 Aug 2004 17:05:11 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 52260-04 for ; Tue, 10 Aug 2004 20:05:03 +0000 (GMT) Received: from bayswater1.ymogen.net (host-154-240-27-217.pobox.net.uk [217.27.240.154]) by svr1.postgresql.org (Postfix) with ESMTP id 0D2B614B27FF for ; Tue, 10 Aug 2004 17:04:58 -0300 (ADT) Received: by bayswater1.ymogen.net (Postfix, from userid 99) id 765C2A607F; Tue, 10 Aug 2004 21:04:56 +0100 (BST) Received: from 82.68.132.233 (SquirrelMail authenticated user matt@ymogen.net) by webmail.ymogen.com with HTTP; Tue, 10 Aug 2004 21:04:56 +0100 (BST) Message-ID: <4995.82.68.132.233.1092168296.squirrel@webmail.ymogen.com> In-Reply-To: References: <007f01c47d54$233b4bf0$8300a8c0@solent> Date: Tue, 10 Aug 2004 21:04:56 +0100 (BST) Subject: Re: Performance Bottleneck From: matt@ymogen.net To: "Alex Hayward" Cc: "'PostgreSQL Performance'" User-Agent: SquirrelMail/1.4.2-0.1.7.x MIME-Version: 1.0 Content-Type: text/plain;charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Priority: 3 Importance: Normal X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=1.1 tagged_above=0.0 required=5.0 tests=NO_REAL_NAME, PRIORITY_NO_NAME X-Spam-Level: * X-Archive-Number: 200408/128 X-Sequence-Number: 7764 > Squid also takes away the work of doing SSL (presuming you're running it > on a different machine). Unfortunately it doesn't support HTTP/1.1 which > means that most generated pages (those that don't set Content-length) end > up forcing squid to close and then reopen the connection to the web > server. It is true that it doesn't support http/1.1, but 'most generated pages'? Unless they are actually emitted progressively they should have a perfectly good content-length header. > I've also had some problems when Squid had a large number of connections > open (several thousand); though that may have been because of my > half_closed_clients setting. Squid 3 coped a lot better when I tried it > (quite a few months ago now - and using FreeBSD and the special kqueue > system call) but crashed under some (admittedly synthetic) conditions. It runs out of the box with a very conservative setting for max open file descriptors - this may or may not be the cause of the problems you have seen. Certainly I ran squid with >16,000 connections back in 1999... > You still have periods of time when the web servers are busy using their > CPUs to generate HTML rather than waiting for database queries. This is > especially true if you cache a lot of data somewhere on the web servers > themselves (which, in my experience, reduces the database load a great > deal). If you REALLY need to reduce the number of connections (because you > have a large number of web servers doing a lot of computation, say) then > it might still be useful. Aha, a postgres related topic in this thread! What you say is very true, but then given that the connection overhead is so vanishingly small, why not simply run without a persistent DB connection in this case? I would maintain that if your webservers are holding open idle DB connections for so long that it's a problem, then simply close the connections! M From pgsql-performance-owner@postgresql.org Tue Aug 10 18:13:24 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id E172714B2806 for ; Tue, 10 Aug 2004 17:48:16 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 66814-04 for ; Tue, 10 Aug 2004 20:48:12 +0000 (GMT) Received: from main.gmane.org (main.gmane.org [80.91.224.249]) by svr1.postgresql.org (Postfix) with ESMTP id CADC414B281D for ; Tue, 10 Aug 2004 17:48:06 -0300 (ADT) Received: from list by main.gmane.org with local (Exim 3.35 #1 (Debian)) id 1BudXQ-0001Ja-00 for ; Tue, 10 Aug 2004 22:48:04 +0200 Received: from sp-260-1.net4.netcentrix.net ([4.21.254.118]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 10 Aug 2004 22:48:04 +0200 Received: from doug by sp-260-1.net4.netcentrix.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 10 Aug 2004 22:48:04 +0200 X-Injected-Via-Gmane: http://gmane.org/ To: pgsql-performance@postgresql.org From: Doug McNaught Subject: Re: Slow select, insert, update Date: Tue, 10 Aug 2004 16:48:01 -0400 Lines: 29 Message-ID: <87r7qeg1oe.fsf@asmodeus.mcnaught.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Complaints-To: usenet@sea.gmane.org X-Gmane-NNTP-Posting-Host: sp-260-1.net4.netcentrix.net User-Agent: Gnus/5.1002 (Gnus v5.10.2) Emacs/20.7 (gnu/linux) Cancel-Lock: sha1:wCwlQc8Kq7L2XH8Q0rFIhdsDwdc= X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/127 X-Sequence-Number: 7763 Paul Langard writes: > Having trouble with one table (see time to count records below!). > > Fairly new to postgres so any help much appreciated. > > It only contains 9,106 records - as you can see from: > > > select count(id) from project > > count > 9106 > 1 row(s) > Total runtime: 45,778.813 ms > ... the database is regularly vaccuumed. Hmm. You might try a VACUUM FULL and a REINDEX on the table (you don't say what version you are running--REINDEX is sometimes needed on 7.3 and below). Also, use EXPLAIN ANALYZE on your query and post the result--that's helpful diagnostic information. -Doug -- Let us cross over the river, and rest under the shade of the trees. --T. J. Jackson, 1863 From pgsql-performance-owner@postgresql.org Tue Aug 10 23:23:38 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id ABD4A14B281D for ; Tue, 10 Aug 2004 18:44:05 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 90224-04 for ; Tue, 10 Aug 2004 21:44:01 +0000 (GMT) Received: from web13123.mail.yahoo.com (web13123.mail.yahoo.com [216.136.174.141]) by svr1.postgresql.org (Postfix) with SMTP id 91F9914B27FF for ; Tue, 10 Aug 2004 18:43:58 -0300 (ADT) Message-ID: <20040810214400.55597.qmail@web13123.mail.yahoo.com> Received: from [63.78.248.48] by web13123.mail.yahoo.com via HTTP; Tue, 10 Aug 2004 14:44:00 PDT Date: Tue, 10 Aug 2004 14:44:00 -0700 (PDT) From: Litao Wu Subject: Re: Slow select, insert, update To: Doug McNaught , pgsql-performance@postgresql.org In-Reply-To: <87r7qeg1oe.fsf@asmodeus.mcnaught.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/140 X-Sequence-Number: 7776 Does that mean reindex is not needed for PG version 7.4? In what kind situations under PG 7.4, reindex is worthwhile? Thanks, Here is doc from 7.3: PostgreSQL is unable to reuse B-tree index pages in certain cases. The problem is that if indexed rows are deleted, those index pages can only be reused by rows with similar values. For example, if indexed rows are deleted and newly inserted/updated rows have much higher values, the new rows can't use the index space made available by the deleted rows. Instead, such new rows must be placed on new index pages. In such cases, disk space used by the index will grow indefinitely, even if VACUUM is run frequently. As a solution, you can use the REINDEX command periodically to discard pages used by deleted rows. There is also contrib/reindexdb which can reindex an entire database. The counterpart of 7.4 is: In some situations it is worthwhile to rebuild indexes periodically with the REINDEX command. (There is also contrib/reindexdb which can reindex an entire database.) However, PostgreSQL 7.4 has substantially reduced the need for this activity compared to earlier releases. --- Doug McNaught wrote: > Paul Langard writes: > > > Having trouble with one table (see time to count > records below!). > > > > Fairly new to postgres so any help much > appreciated. > > > > It only contains 9,106 records - as you can see > from: > > > > > > select count(id) from project > > > > count > > 9106 > > 1 row(s) > > Total runtime: 45,778.813 ms > > > ... the database is regularly vaccuumed. > > Hmm. You might try a VACUUM FULL and a REINDEX on > the table (you > don't say what version you are running--REINDEX is > sometimes needed on > 7.3 and below). > > Also, use EXPLAIN ANALYZE on your query and post the > result--that's > helpful diagnostic information. > > -Doug > -- > Let us cross over the river, and rest under the > shade of the trees. > --T. J. Jackson, 1863 > > > ---------------------------(end of > broadcast)--------------------------- > TIP 8: explain analyze is your friend > __________________________________ Do you Yahoo!? Read only the mail you want - Yahoo! Mail SpamGuard. http://promotions.yahoo.com/new_mail From pgsql-performance-owner@postgresql.org Tue Aug 10 22:46:26 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 92E9A14B281E for ; Tue, 10 Aug 2004 20:06:21 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 11447-09 for ; Tue, 10 Aug 2004 23:06:18 +0000 (GMT) Received: from diablo.OntheNet.com.au (diablo.OntheNet.com.au [203.10.89.2]) by svr1.postgresql.org (Postfix) with ESMTP id 5D6B714B281D for ; Tue, 10 Aug 2004 20:06:16 -0300 (ADT) Received: from [192.168.0.114] (imp3.dsl.onthenet.net [203.144.21.139]) by diablo.OntheNet.com.au (8.12.10/8.12.10) with ESMTP id i7AN6H4G066145 for ; Wed, 11 Aug 2004 09:06:18 +1000 (EST) Message-ID: <41195462.9090303@wildcash.com> Date: Wed, 11 Aug 2004 09:04:02 +1000 From: Rudi Starcevic Reply-To: tech@wildcash.com Organization: Internet Media Productions User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7) Gecko/20040616 X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Bulk Insert and Index use X-Enigmail-Version: 0.85.0.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/139 X-Sequence-Number: 7775 Hi, I have a question on bulk checking, inserting into a table and how best to use an index for performance. The data I have to work with is a monthly CD Rom csv data dump of 300,000 property owners from one area/shire. So every CD has 300,000 odd lines, each line of data which fills the 'property' table. Beginning with the first CD each line should require one SELECT and one INSERT as it will be the first property with this address. The SELECT uses fields like 'street' and 'suburb', to check for an existing property, so I have built an index on those fields. My question is does each INSERT rebuild the index on the 'street' and 'suburb' fields? I believe it does but I'm asking to be sure. If this is the case I guess performance will suffer when I have, say, 200,000 rows in the table. Would it be like: a) Use index to search on 'street' and 'suburb' b) No result? Insert new record c) Rebuild index on 'street' and 'suburb' for each row? Would this mean that after 200,000 rows each INSERT will require the index of 000's of rows to be re-indexed? So far I believe my only options are to use either and index or sequential scan and see which is faster. A minute for your thoughts and/or suggestions would be great. Thanks. Regards, Rudi. From pgsql-performance-owner@postgresql.org Tue Aug 10 22:43:19 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id B962314B2806 for ; Tue, 10 Aug 2004 20:06:55 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 13472-03 for ; Tue, 10 Aug 2004 23:06:52 +0000 (GMT) Received: from tht.net (vista.tht.net [216.126.88.2]) by svr1.postgresql.org (Postfix) with ESMTP id 148C214B27FF for ; Tue, 10 Aug 2004 20:06:51 -0300 (ADT) Received: from [134.22.70.202] (dyn-70-202.tor.dsl.tht.net [134.22.70.202]) by tht.net (Postfix) with ESMTP id 81DE076A54; Tue, 10 Aug 2004 19:06:58 -0400 (EDT) Subject: Re: Hardware upgrade for a high-traffic database From: Rod Taylor To: Jason Coene Cc: Postgresql Performance In-Reply-To: <200408101917.i7AJHR0E064106@mail.gotfrag.com> References: <200408101917.i7AJHR0E064106@mail.gotfrag.com> Content-Type: text/plain Message-Id: <1092179211.11635.30.camel@jester> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Tue, 10 Aug 2004 19:06:52 -0400 Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/138 X-Sequence-Number: 7774 > Our database is about 20GB on disk, we have some quite large tables - 2M > rows with TEXT fields in a sample table, accessed constantly. We average > about 4,000 - 5,000 queries per second - all from web traffic. As you can 99% is reads? and probably the same data over and over again? You might want to think about a small code change to cache sections of page output in memory for the most commonly generated pages (there are usually 3 or 4 that account for 25% to 50% of web traffic -- starting pages). The fact you're getting 5k queries/second off IDE drives tells me most of the active data is in memory -- so your actual working data set is probably quite small (less than 10% of the 20GB). If the above is all true (mostly reads, smallish dataset, etc.) and the database is not growing very quickly, you might want to look into RAM and RAM bandwidth over disk. An Opteron with 8GB ram using the same old IDE drives. Get a mobo with a SCSI raid controller in it, so the disk component can be upgraded in the future (when necessary). From pgsql-performance-owner@postgresql.org Tue Aug 10 22:30:14 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id F37BE14B2800 for ; Tue, 10 Aug 2004 20:58:39 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 29023-01 for ; Tue, 10 Aug 2004 23:58:35 +0000 (GMT) Received: from mpls-qmqp-04.inet.qwest.net (mpls-qmqp-04.inet.qwest.net [63.231.195.115]) by svr1.postgresql.org (Postfix) with SMTP id 3E21E14B27FF for ; Tue, 10 Aug 2004 20:58:32 -0300 (ADT) Received: (qmail 64577 invoked by uid 0); 10 Aug 2004 23:58:35 -0000 Received: from mpls-pop-08.inet.qwest.net (63.231.195.8) by mpls-qmqp-04.inet.qwest.net with QMQP; 10 Aug 2004 23:58:35 -0000 Received: from 63-227-127-37.dnvr.qwest.net (HELO ?10.0.0.2?) (63.227.127.37) by mpls-pop-08.inet.qwest.net with SMTP; 10 Aug 2004 23:58:35 -0000 Date: Tue, 10 Aug 2004 18:00:01 -0600 Message-Id: <1092182401.27166.348.camel@localhost.localdomain> From: "Scott Marlowe" To: "Jason Coene" Cc: pgsql-performance@postgresql.org Subject: Re: Hardware upgrade for a high-traffic database In-Reply-To: <200408101917.i7AJHR0E064106@mail.gotfrag.com> References: <200408101917.i7AJHR0E064106@mail.gotfrag.com> Content-Type: text/plain Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/137 X-Sequence-Number: 7773 On Tue, 2004-08-10 at 13:17, Jason Coene wrote: > Hi All, > > We're currently running Postgres 7.4.1 on FreeBSD 5.2, a Dual Xeon 2.4, 2GB > ECC, 3Ware Serial ATA RAID 5 w/ 4 disks (SLOW!!). > > Our database is about 20GB on disk, we have some quite large tables - 2M > rows with TEXT fields in a sample table, accessed constantly. We average > about 4,000 - 5,000 queries per second - all from web traffic. As you can > imagine, we're quite disk limited and checkpoints can be killer. > Additionally, we see queries and connections getting serialized due to > queries that take a long time (5 sec or so) while waiting on disk access. > No fun at all. > > We've tweaked everything long and hard, and at the end of the day, the disk > is killing us. > > We're looking to upgrade our server - or rather, replace it as it has no > upgrade path to SCSI. I'm considering going Opteron (though right now we > don't need more CPU time), and am looking for suggestions on what an optimal > RAID configuration may look like (disks, controller, cache setting). We're > in the market to buy right now - any good vendor suggestions? I've had very good luck with LSI MegaRAID controllers with battery backed cache. The amount of cache doesn't seem as important as having it, and having it set for write back. After that, 2 gigs or more of memory is the next improvement. After that, the speed of the memory. From pgsql-performance-owner@postgresql.org Tue Aug 10 22:10:45 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 49D4D14B2881 for ; Tue, 10 Aug 2004 22:06:59 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 48137-02 for ; Wed, 11 Aug 2004 01:06:53 +0000 (GMT) Received: from mail.gotfrag.com (unknown [66.208.110.11]) by svr1.postgresql.org (Postfix) with ESMTP id A4BDC14B2878 for ; Tue, 10 Aug 2004 22:06:44 -0300 (ADT) Received: from jcoene2 (roc-66-66-149-175.rochester.rr.com [66.66.149.175]) by mail.gotfrag.com (8.12.10/8.12.8) with ESMTP id i7B16b0E072661; Tue, 10 Aug 2004 21:06:37 -0400 (EDT) (envelope-from jcoene@gotfrag.com) Message-Id: <200408110106.i7B16b0E072661@mail.gotfrag.com> From: "Jason Coene" To: "'Rod Taylor'" Cc: "'Postgresql Performance'" Subject: Re: Hardware upgrade for a high-traffic database Date: Tue, 10 Aug 2004 21:06:37 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook, Build 11.0.5510 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2096 In-Reply-To: <1092179211.11635.30.camel@jester> Thread-Index: AcR/Lr47tKJaxYJUST64s429yuXv/gADnnNw X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/136 X-Sequence-Number: 7772 Hi Rod, Actually, we're already using a substantial caching system in code for nearly all pages delivered - we've exhausted that option. Our system uses a login/session table for about 1/8 of our page views (those visitors who are logged in), and has tracking features. While I'd love to scrap them and give the database server a vacation, it's a requirement for us. You're correct about the query caching (stored in memory) being used - most of our queries are run once and then come from memory (or, based on speed of consecutive executions, that seems to be the case). Once a user hits a page for the first time in an hour or so, it seems to cache their session query. The issue that I think we're seeing is that the performance on the 3Ware RAID is quite bad, watching FreeBSD systat will show it at "100% busy" at around "3.5 MB/s". When it needs to seek across a table (for, say, an aggregate function - typically a COUNT()), it slows the entire server down while working on the disk. Additionally, VACUUM's make the server practically useless. We have indexes on everything that's used in queries, and the planner is using them. The server has 2GB of physical memory, however it's only uses between 130MB and 200MB of it. Postgres is the only application running on the server. Our pertinent settings look like this: max_connections = 512 shared_buffers = 20000 sort_mem = 2000 vacuum_mem = 20000 effective_cache_size = 300000 fsync = false wal_sync_method = fsync wal_buffers = 32 checkpoint_segments = 2 checkpoint_timeout = 30 commit_delay = 10000 Typically, we don't use anywhere near the 512 connections - however there are peak hours where we come close, and other times that we eclipse it and run out (should some connections become serialized due to a slowdown). It's not something that we can comfortably lower. The non-standard checkpoint settings have helped making it less likely that a large (in disk time) query will conflict with a checkpoint write. I'm a programmer - definitely not a DBA by any stretch - though I am forced into the role. From reading this list, it seems to me that our settings are reasonable given our usage, and that a disk upgrade is likely in order. I'd love to hear any suggestions. Thanks, Jason -----Original Message----- From: Rod Taylor [mailto:pg@rbt.ca] Sent: Tuesday, August 10, 2004 7:07 PM To: Jason Coene Cc: Postgresql Performance Subject: Re: [PERFORM] Hardware upgrade for a high-traffic database > Our database is about 20GB on disk, we have some quite large tables - 2M > rows with TEXT fields in a sample table, accessed constantly. We average > about 4,000 - 5,000 queries per second - all from web traffic. As you can 99% is reads? and probably the same data over and over again? You might want to think about a small code change to cache sections of page output in memory for the most commonly generated pages (there are usually 3 or 4 that account for 25% to 50% of web traffic -- starting pages). The fact you're getting 5k queries/second off IDE drives tells me most of the active data is in memory -- so your actual working data set is probably quite small (less than 10% of the 20GB). If the above is all true (mostly reads, smallish dataset, etc.) and the database is not growing very quickly, you might want to look into RAM and RAM bandwidth over disk. An Opteron with 8GB ram using the same old IDE drives. Get a mobo with a SCSI raid controller in it, so the disk component can be upgraded in the future (when necessary). From pgsql-performance-owner@postgresql.org Wed Aug 11 00:53:44 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3DE3F14B2824 for ; Wed, 11 Aug 2004 00:11:09 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 77310-03 for ; Wed, 11 Aug 2004 03:11:05 +0000 (GMT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by svr1.postgresql.org (Postfix) with ESMTP id 384AA14B2825 for ; Wed, 11 Aug 2004 00:11:03 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.12.9/8.12.9) with ESMTP id i7B3B3iG078513 for ; Wed, 11 Aug 2004 03:11:03 GMT (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.12.9/8.12.9/Submit) id i7B2nv6S066003 for pgsql-performance@postgresql.org; Wed, 11 Aug 2004 02:49:57 GMT From: Christopher Browne X-Newsgroups: comp.databases.postgresql.performance Subject: Re: Bulk Insert and Index use Date: Tue, 10 Aug 2004 22:24:31 -0400 Organization: cbbrowne Computing Inc Lines: 22 Message-ID: References: <41195462.9090303@wildcash.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Complaints-To: usenet@news.hub.org X-message-flag: Outlook is rather hackable, isn't it? X-Home-Page: http://www.cbbrowne.com/info/ X-Affero: http://svcs.affero.net/rm.php?r=cbbrowne User-Agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Security Through Obscurity, linux) Cancel-Lock: sha1:u/B7c0mLYN+Z0weWz32cEutc6Hs= To: pgsql-performance@postgresql.org X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/144 X-Sequence-Number: 7780 In an attempt to throw the authorities off his trail, tech@wildcash.com (Rudi Starcevic) transmitted: > A minute for your thoughts and/or suggestions would be great. Could you give a more concrete example? E.g. - the DDL for the table(s), most particularly. At first guess, I think you're worrying about a nonissue. Each insert will lead to a _modification_ of the various indices, which costs _something_, but which is WAY less expensive than creating each index from scratch. But perhaps I'm misreading things; DDL for the intended tables and indices would be real handy. -- output = ("cbbrowne" "@" "cbbrowne.com") http://www.ntlug.org/~cbbrowne/linux.html Rules of the Evil Overlord #21. "I will hire a talented fashion designer to create original uniforms for my Legions of Terror, as opposed to some cheap knock-offs that make them look like Nazi stormtroopers, Roman footsoldiers, or savage Mongol hordes. All were eventually defeated and I want my troops to have a more positive mind-set." From pgsql-performance-owner@postgresql.org Tue Aug 10 23:55:23 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 6ED1714B2879 for ; Tue, 10 Aug 2004 23:27:59 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 39878-02 for ; Wed, 11 Aug 2004 02:27:50 +0000 (GMT) Received: from loki.globexplorer.com (unknown [208.35.14.101]) by svr1.postgresql.org (Postfix) with ESMTP id 9F76314B2825 for ; Tue, 10 Aug 2004 23:27:43 -0300 (ADT) X-MimeOLE: Produced By Microsoft Exchange V6.0.6249.0 content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Subject: Re: Bulk Insert and Index use Date: Tue, 10 Aug 2004 19:27:48 -0700 Message-ID: <71E37EF6B7DCC1499CEA0316A256832801057DE3@loki.wc.globexplorer.net> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] Bulk Insert and Index use Thread-Index: AcR/RapGzA5gUW+EScWUjqvJE4OhUgABJVEz From: "Gregory S. Williamson" To: , X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/142 X-Sequence-Number: 7778 Usualy any bulk load is faster with indexes dropped and the rebuilt ... fai= ling that (like you really need the indexes while loading, say into a "hot"= table) be sure to wrap all the SQL into one transaction (BEGIN;...COMMIT;)= ... if any data failes it all fails, which is usually easier to deal with = than partial data loads, and it is *much* faster than having each insert be= ing its own transaction. HTH, Greg Williamson DBA GlobeXplorer LLC -----Original Message----- From: Rudi Starcevic [mailto:tech@wildcash.com] Sent: Tue 8/10/2004 4:04 PM To: pgsql-performance@postgresql.org Cc:=09 Subject: [PERFORM] Bulk Insert and Index use Hi, I have a question on bulk checking, inserting into a table and how best to use an index for performance. The data I have to work with is a monthly CD Rom csv data dump of 300,000 property owners from one area/shire. So every CD has 300,000 odd lines, each line of data which fills the=20 'property' table. Beginning with the first CD each line should require one SELECT and one INSERT as it will be the first property with this address. The SELECT uses fields like 'street' and 'suburb', to check for an=20 existing property, so I have built an index on those fields. My question is does each INSERT rebuild the index on the 'street' and=20 'suburb' fields? I believe it does but I'm asking to be sure. If this is the case I guess performance will suffer when I have, say,=20 200,000 rows in the table. Would it be like: a) Use index to search on 'street' and 'suburb' b) No result? Insert new record c) Rebuild index on 'street' and 'suburb' for each row? Would this mean that after 200,000 rows each INSERT will require the index of 000's of rows to be re-indexed? So far I believe my only options are to use either and index or sequential scan and see which is faster. A minute for your thoughts and/or suggestions would be great. Thanks. Regards, Rudi. ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster From pgsql-performance-owner@postgresql.org Tue Aug 10 23:54:07 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 4470C14B281F for ; Tue, 10 Aug 2004 23:31:35 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 53761-02 for ; Wed, 11 Aug 2004 02:31:30 +0000 (GMT) Received: from smtp.gvtc.com (smtp.gvtc.com [216.177.160.80]) by svr1.postgresql.org (Postfix) with ESMTP id 6FF4D14B281E for ; Tue, 10 Aug 2004 23:31:13 -0300 (ADT) Received: from [192.168.1.102] (unknown [12.181.66.221]) by smtp.gvtc.com (Postfix) with ESMTP id 6DAC91939C3 for ; Tue, 10 Aug 2004 21:31:17 -0500 (CDT) Message-ID: <41198514.1020103@gvtc.com> Date: Tue, 10 Aug 2004 21:31:48 -0500 From: Jim J User-Agent: Mozilla Thunderbird 0.7.3 (X11/20040803) X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: Bulk Insert and Index use References: <41195462.9090303@wildcash.com> In-Reply-To: <41195462.9090303@wildcash.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/141 X-Sequence-Number: 7777 If the bulk load has the possibility of duplicating data, then you need to change methods. Try bulk loading into a temp table, index it like the original, eliminate the dups and merge the tables. It is also possible to do an insert from the temp table into the final table like: insert into original (x,x,x) (select temp.1, temp.2, etc from temp left join original on temp.street=original.street where original.street is null) Good Luck Jim Rudi Starcevic wrote: > Hi, > > I have a question on bulk checking, inserting into a table and > how best to use an index for performance. > > The data I have to work with is a monthly CD Rom csv data dump of > 300,000 property owners from one area/shire. > > So every CD has 300,000 odd lines, each line of data which fills the > 'property' table. > > Beginning with the first CD each line should require one SELECT and > one INSERT as it will be the first property with this address. > > The SELECT uses fields like 'street' and 'suburb', to check for an > existing property, > so I have built an index on those fields. > > My question is does each INSERT rebuild the index on the 'street' and > 'suburb' fields? > I believe it does but I'm asking to be sure. > > If this is the case I guess performance will suffer when I have, say, > 200,000 > rows in the table. > > Would it be like: > > a) Use index to search on 'street' and 'suburb' > b) No result? Insert new record > c) Rebuild index on 'street' and 'suburb' > > for each row? > Would this mean that after 200,000 rows each INSERT will require > the index of 000's of rows to be re-indexed? > > So far I believe my only options are to use either and index > or sequential scan and see which is faster. > > A minute for your thoughts and/or suggestions would be great. > > Thanks. > Regards, > Rudi. > > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Don't 'kill -9' the postmaster > > From pgsql-performance-owner@postgresql.org Wed Aug 11 00:41:29 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 658F614B2869 for ; Wed, 11 Aug 2004 00:36:08 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 95343-09 for ; Wed, 11 Aug 2004 03:36:03 +0000 (GMT) Received: from diablo.OntheNet.com.au (diablo.OntheNet.com.au [203.10.89.2]) by svr1.postgresql.org (Postfix) with ESMTP id 9F59814B2827 for ; Wed, 11 Aug 2004 00:35:59 -0300 (ADT) Received: from [192.168.0.114] (imp3.dsl.onthenet.net [203.144.21.139]) by diablo.OntheNet.com.au (8.12.10/8.12.10) with ESMTP id i7B3Zn4G012260 for ; Wed, 11 Aug 2004 13:35:50 +1000 (EST) Message-ID: <4119938D.6000609@wildcash.com> Date: Wed, 11 Aug 2004 13:33:33 +1000 From: Rudi Starcevic Reply-To: tech@wildcash.com Organization: Internet Media Productions User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7) Gecko/20040616 X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: Bulk Insert and Index use References: <41195462.9090303@wildcash.com> <41198514.1020103@gvtc.com> In-Reply-To: <41198514.1020103@gvtc.com> X-Enigmail-Version: 0.85.0.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/143 X-Sequence-Number: 7779 Hi Jim, Thanks for your time. > If the bulk load has the possibility of duplicating data Yes, each row will require either: a) One SELECT + One INSERT or b) One SELECT + One UPDATE I did think of using more than one table, ie. temp table. As each month worth of data is added I expect to see a change from lots of INSERTS to lots of UPDATES. Perhaps when the UPDATES become more dominant it would be best to start using Indexes. While INSERTS are more prevelant perhaps a seq. scan is better. I guess of all the options available it boils down to which is quicker for my data: index or sequential scan. Many thanks. Jim J wrote: > If the bulk load has the possibility of duplicating data, then you need > to change methods. Try bulk loading into a temp table, index it like > the original, eliminate the dups and merge the tables. > > It is also possible to do an insert from the temp table into the final > table like: > insert into original (x,x,x) (select temp.1, temp.2, etc from temp left > join original on temp.street=original.street where original.street is null) > > Good Luck > Jim > > Rudi Starcevic wrote: > >> Hi, >> >> I have a question on bulk checking, inserting into a table and >> how best to use an index for performance. >> >> The data I have to work with is a monthly CD Rom csv data dump of >> 300,000 property owners from one area/shire. >> >> So every CD has 300,000 odd lines, each line of data which fills the >> 'property' table. >> >> Beginning with the first CD each line should require one SELECT and >> one INSERT as it will be the first property with this address. >> >> The SELECT uses fields like 'street' and 'suburb', to check for an >> existing property, >> so I have built an index on those fields. >> >> My question is does each INSERT rebuild the index on the 'street' and >> 'suburb' fields? >> I believe it does but I'm asking to be sure. >> >> If this is the case I guess performance will suffer when I have, say, >> 200,000 >> rows in the table. >> >> Would it be like: >> >> a) Use index to search on 'street' and 'suburb' >> b) No result? Insert new record >> c) Rebuild index on 'street' and 'suburb' >> >> for each row? >> Would this mean that after 200,000 rows each INSERT will require >> the index of 000's of rows to be re-indexed? >> >> So far I believe my only options are to use either and index >> or sequential scan and see which is faster. >> >> A minute for your thoughts and/or suggestions would be great. >> >> Thanks. >> Regards, >> Rudi. >> >> >> ---------------------------(end of broadcast)--------------------------- >> TIP 4: Don't 'kill -9' the postmaster >> >> > > > ---------------------------(end of broadcast)--------------------------- > TIP 5: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faqs/FAQ.html > > -- Regards, Rudi. Internet Media Productions From pgsql-performance-owner@postgresql.org Wed Aug 11 01:15:38 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 4A28614B27FF for ; Wed, 11 Aug 2004 00:53:19 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 98548-06 for ; Wed, 11 Aug 2004 03:53:14 +0000 (GMT) Received: from loki.globexplorer.com (unknown [208.35.14.101]) by svr1.postgresql.org (Postfix) with ESMTP id E742E14B281D for ; Wed, 11 Aug 2004 00:53:11 -0300 (ADT) X-MimeOLE: Produced By Microsoft Exchange V6.0.6249.0 content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Subject: Re: Bulk Insert and Index use Date: Tue, 10 Aug 2004 20:53:11 -0700 Message-ID: <71E37EF6B7DCC1499CEA0316A256832801057DE5@loki.wc.globexplorer.net> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PERFORM] Bulk Insert and Index use Thread-Index: AcR/VbSjdfgqG3vyTu6v1DCcYxTeTwAANAQC From: "Gregory S. Williamson" To: , X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/145 X-Sequence-Number: 7781 If it has to read a majority (or even a good percentage) of the rows in que= stion a sequential scan is probably faster ... and as Jim pointed out, a te= mp table can often be a useful medium for getting speed in a load and then = allowing you to clean/alter data for a final (easy) push. G -----Original Message----- From: Rudi Starcevic [mailto:tech@wildcash.com] Sent: Tue 8/10/2004 8:33 PM To: pgsql-performance@postgresql.org Cc:=09 Subject: Re: [PERFORM] Bulk Insert and Index use Hi Jim, Thanks for your time. > If the bulk load has the possibility of duplicating data Yes, each row will require either: a) One SELECT + One INSERT or b) One SELECT + One UPDATE I did think of using more than one table, ie. temp table. As each month worth of data is added I expect to see a change from lots of INSERTS to lots of UPDATES. Perhaps when the UPDATES become more dominant it would be best to start using Indexes. While INSERTS are more prevelant perhaps a seq. scan is better. I guess of all the options available it boils down to which is quicker for my data: index or sequential scan. Many thanks. Jim J wrote: > If the bulk load has the possibility of duplicating data, then you need= =20 > to change methods. Try bulk loading into a temp table, index it like=20 > the original, eliminate the dups and merge the tables. >=20 > It is also possible to do an insert from the temp table into the final=20 > table like: > insert into original (x,x,x) (select temp.1, temp.2, etc from temp left= =20 > join original on temp.street=3Doriginal.street where original.street is n= ull) >=20 > Good Luck > Jim >=20 > Rudi Starcevic wrote: >=20 >> Hi, >> >> I have a question on bulk checking, inserting into a table and >> how best to use an index for performance. >> >> The data I have to work with is a monthly CD Rom csv data dump of >> 300,000 property owners from one area/shire. >> >> So every CD has 300,000 odd lines, each line of data which fills the=20 >> 'property' table. >> >> Beginning with the first CD each line should require one SELECT and >> one INSERT as it will be the first property with this address. >> >> The SELECT uses fields like 'street' and 'suburb', to check for an=20 >> existing property, >> so I have built an index on those fields. >> >> My question is does each INSERT rebuild the index on the 'street' and=20 >> 'suburb' fields? >> I believe it does but I'm asking to be sure. >> >> If this is the case I guess performance will suffer when I have, say,=20 >> 200,000 >> rows in the table. >> >> Would it be like: >> >> a) Use index to search on 'street' and 'suburb' >> b) No result? Insert new record >> c) Rebuild index on 'street' and 'suburb' >> >> for each row? >> Would this mean that after 200,000 rows each INSERT will require >> the index of 000's of rows to be re-indexed? >> >> So far I believe my only options are to use either and index >> or sequential scan and see which is faster. >> >> A minute for your thoughts and/or suggestions would be great. >> >> Thanks. >> Regards, >> Rudi. >> >> >> ---------------------------(end of broadcast)--------------------------- >> TIP 4: Don't 'kill -9' the postmaster >> >> >=20 >=20 > ---------------------------(end of broadcast)--------------------------- > TIP 5: Have you checked our extensive FAQ? >=20 > http://www.postgresql.org/docs/faqs/FAQ.html >=20 >=20 --=20 Regards, Rudi. Internet Media Productions ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org From pgsql-performance-owner@postgresql.org Wed Aug 11 01:25:03 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 4762014B281C for ; Wed, 11 Aug 2004 01:13:19 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 67717-08 for ; Wed, 11 Aug 2004 04:13:12 +0000 (GMT) Received: from diablo.OntheNet.com.au (diablo.OntheNet.com.au [203.10.89.2]) by svr1.postgresql.org (Postfix) with ESMTP id ECB9B14B2824 for ; Wed, 11 Aug 2004 01:13:10 -0300 (ADT) Received: from [192.168.0.114] (imp3.dsl.onthenet.net [203.144.21.139]) by diablo.OntheNet.com.au (8.12.10/8.12.10) with ESMTP id i7B4D84G018093 for ; Wed, 11 Aug 2004 14:13:09 +1000 (EST) Message-ID: <41199C4C.9040308@wildcash.com> Date: Wed, 11 Aug 2004 14:10:52 +1000 From: Rudi Starcevic Reply-To: tech@wildcash.com Organization: Internet Media Productions User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7) Gecko/20040616 X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: Bulk Insert and Index use References: <41195462.9090303@wildcash.com> In-Reply-To: X-Enigmail-Version: 0.85.0.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/146 X-Sequence-Number: 7782 Hi, > In an attempt to throw the authorities off his trail, tech@wildcash.com (Rudi Starcevic) transmitted: > A minute for your thoughts and/or suggestions would be great. Heh heh .... > Could you give a more concrete example? E.g. - the DDL for the > table(s), most particularly. Thanks, I didn't add the DDL as I though it may make my question too long. I have the DDL at another office so I'll pick up this email thread when I get there in a couple hours. > At first guess, I think you're worrying about a nonissue. Each insert > will lead to a _modification_ of the various indices, which costs > _something_, but which is WAY less expensive than creating each index > from scratch. Very interesting, modification and creation. I will post another email later today. Many thanks. -- Regards, Rudi. Internet Media Productions From pgsql-performance-owner@postgresql.org Wed Aug 11 02:41:38 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 6582514B2825 for ; Wed, 11 Aug 2004 02:41:35 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 41042-04 for ; Wed, 11 Aug 2004 05:41:29 +0000 (GMT) Received: from linares.terra.com.br (linares.terra.com.br [200.154.55.228]) by svr1.postgresql.org (Postfix) with ESMTP id 2775E14B281E for ; Wed, 11 Aug 2004 02:41:25 -0300 (ADT) Received: from paramonga.terra.com.br (paramonga.terra.com.br [200.154.55.133]) by linares.terra.com.br (Postfix) with ESMTP id 84EEADDC2BD for ; Wed, 11 Aug 2004 02:41:25 -0300 (BRT) Received: from [200.176.35.99] (cm-net-poa-C8B02363.brdterra.com.br [200.176.35.99]) (authenticated user erabbott) by paramonga.terra.com.br (Postfix) with ESMTP id 52FCE3C016 for ; Wed, 11 Aug 2004 02:41:25 -0300 (BRT) Message-ID: <4119B1C9.2010800@galvao.eti.br> Date: Wed, 11 Aug 2004 02:42:33 -0300 From: =?ISO-8859-1?Q?Er_Galv=E3o_Abbott?= Reply-To: galvao@galvao.eti.br User-Agent: Mozilla Thunderbird 0.7.3 (Windows/20040803) X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: NUMERIC x VARCHAR X-Priority: 1 (Highest) Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=3.8 tagged_above=0.0 required=5.0 tests=HTML_40_50, HTML_MESSAGE, HTML_TITLE_EMPTY, MIME_HTML_ONLY, PRIORITY_NO_NAME, RCVD_IN_NJABL, RCVD_IN_NJABL_PROXY, RCVD_IN_SORBS, X_PRIORITY_HIGH X-Spam-Level: *** X-Archive-Number: 200408/147 X-Sequence-Number: 7783 Greetings.

I have a question regarding performance of certain datatypes:

I have a field where I will store my clients phone numbers. I know that this field will never exceed 15 characters, and I will store only numbers here (no dashes, dots, etc...), so I was wondering:

Wich type is faster: NUMERIC(15,0) or VARCHAR(15)? Are there any storage differences between them?

TIA,
 
-- 
Er Galvão Abbott
Desenvolvedor Web
http://www.galvao.eti.br/
galvao@galvao.eti.br
From pgsql-performance-owner@postgresql.org Wed Aug 11 03:20:42 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 2ECAE14B286F for ; Wed, 11 Aug 2004 03:20:41 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 52533-08 for ; Wed, 11 Aug 2004 06:20:30 +0000 (GMT) Received: from mpls-qmqp-01.inet.qwest.net (mpls-qmqp-01.inet.qwest.net [63.231.195.112]) by svr1.postgresql.org (Postfix) with SMTP id AC26D14B286A for ; Wed, 11 Aug 2004 03:20:26 -0300 (ADT) Received: (qmail 2404 invoked by uid 0); 11 Aug 2004 06:20:27 -0000 Received: from unknown (63.231.195.5) by mpls-qmqp-01.inet.qwest.net with QMQP; 11 Aug 2004 06:20:27 -0000 Received: from 63-227-127-37.dnvr.qwest.net (HELO ?10.0.0.2?) (63.227.127.37) by mpls-pop-05.inet.qwest.net with SMTP; 11 Aug 2004 06:20:26 -0000 Date: Wed, 11 Aug 2004 00:21:48 -0600 Message-Id: <1092205308.27166.358.camel@localhost.localdomain> From: "Scott Marlowe" To: galvao@galvao.eti.br Cc: pgsql-performance@postgresql.org Subject: Re: NUMERIC x VARCHAR In-Reply-To: <4119B1C9.2010800@galvao.eti.br> References: <4119B1C9.2010800@galvao.eti.br> Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Content-Transfer-Encoding: 8bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.1 tagged_above=0.0 required=5.0 tests=RCVD_IN_SORBS X-Spam-Level: X-Archive-Number: 200408/148 X-Sequence-Number: 7784 On Tue, 2004-08-10 at 23:42, Er Galvão Abbott wrote: > Greetings. > > I have a question regarding performance of certain datatypes: > > I have a field where I will store my clients phone numbers. I know > that this field will never exceed 15 characters, and I will store only > numbers here (no dashes, dots, etc...), so I was wondering: > > Wich type is faster: NUMERIC(15,0) or VARCHAR(15)? Are there any > storage differences between them? Since numerics are stored as text strings, the storage would be similar. Numerics, however, may be slower since they have more constraints built in. If you throw a check constraint on the varchar(15) then it will likely be about the same speed for updating. text type with a check contraint it what i'd use. That way if you want to change it at a later date you just drop and recreate your constraint. From pgsql-performance-owner@postgresql.org Wed Aug 11 03:43:44 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 5707514B281C for ; Wed, 11 Aug 2004 03:43:43 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 60496-06 for ; Wed, 11 Aug 2004 06:43:36 +0000 (GMT) Received: from boutiquenumerique.com (gailleton-2-82-67-9-10.fbx.proxad.net [82.67.9.10]) by svr1.postgresql.org (Postfix) with ESMTP id E182714B2806 for ; Wed, 11 Aug 2004 03:43:34 -0300 (ADT) Received: (qmail 22277 invoked from network); 11 Aug 2004 08:43:39 +0200 Received: from unknown (HELO musicbox) (192.168.0.2) by gailleton-2-82-67-9-10.fbx.proxad.net with SMTP; 11 Aug 2004 08:43:39 +0200 To: pgsql-performance@postgresql.org Subject: Re: Hardware upgrade for a high-traffic database References: <200408101917.i7AJHR0E064106@mail.gotfrag.com> Message-ID: Date: Wed, 11 Aug 2004 08:43:36 +0200 From: =?iso-8859-15?Q?Pierre-Fr=E9d=E9ric_Caillaud?= Organization: =?iso-8859-15?Q?La_Boutique_Num=E9rique?= Content-Type: text/plain; format=flowed; delsp=yes; charset=iso-8859-15 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In-Reply-To: <200408101917.i7AJHR0E064106@mail.gotfrag.com> User-Agent: Opera M2/7.53 (Linux, build 737) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/149 X-Sequence-Number: 7785 > We're currently running Postgres 7.4.1 on FreeBSD 5.2, a Dual Xeon 2.4, > 2GB > ECC, 3Ware Serial ATA RAID 5 w/ 4 disks (SLOW!!). Cheap solution while you look for another server : Try to use something other than RAID5. You have 4 disks, so you could use a striping+mirroring RAID which would boost performance. You can switch with a minimum downtime (copy files to other HDD, change RAID parameters, copy again...) maybe 1 hour ? If your hardware supports it of course. And tell us how it works ! From pgsql-performance-owner@postgresql.org Wed Aug 11 03:47:14 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3406914B281C for ; Wed, 11 Aug 2004 03:47:13 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 62381-07 for ; Wed, 11 Aug 2004 06:47:08 +0000 (GMT) Received: from boutiquenumerique.com (gailleton-2-82-67-9-10.fbx.proxad.net [82.67.9.10]) by svr1.postgresql.org (Postfix) with ESMTP id 808FD14B2806 for ; Wed, 11 Aug 2004 03:47:07 -0300 (ADT) Received: (qmail 22397 invoked from network); 11 Aug 2004 08:47:12 +0200 Received: from unknown (HELO musicbox) (192.168.0.2) by gailleton-2-82-67-9-10.fbx.proxad.net with SMTP; 11 Aug 2004 08:47:12 +0200 To: pgsql-performance@postgresql.org Subject: Re: NUMERIC x VARCHAR References: <4119B1C9.2010800@galvao.eti.br> Message-ID: From: =?iso-8859-15?Q?Pierre-Fr=E9d=E9ric_Caillaud?= Organization: =?iso-8859-15?Q?La_Boutique_Num=E9rique?= Content-Type: text/plain; format=flowed; delsp=yes; charset=iso-8859-15 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Date: Wed, 11 Aug 2004 08:47:10 +0200 In-Reply-To: <4119B1C9.2010800@galvao.eti.br> User-Agent: Opera M2/7.53 (Linux, build 737) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200408/150 X-Sequence-Number: 7786 Numeric won't store that : (+33) 4 01 23 45 67 On Wed, 11 Aug 2004 02:42:33 -0300, Er Galv�o Abbott wrote: > Greetings. > > I have a question regarding performance of certain datatypes: > > I have a field where I will store my clients phone numbers. I know that > this > field will never exceed 15 characters, and I will store only numbers > here (no > dashes, dots, etc...), so I was wondering: > > Wich type is faster: NUMERIC(15,0) or VARCHAR(15)? Are there any storage > differences between them? > > TIA, > From pgsql-performance-owner@postgresql.org Wed Aug 11 04:26:34 2004 X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id C7C6E14B27FF for ; Wed, 11 Aug 2004 04:26:32 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 74112-10 for ; Wed, 11 Aug 2004 07:26:25 +0000 (GMT) Received: from itapoa.terra.com.br (itapoa.terra.com.br [200.154.55.227]) by svr1.postgresql.org (Postfix) with ESMTP id 16C7314B287E for ; Wed, 11 Aug 2004 04:26:21 -0300 (ADT) Received: from talara.terra.com.br (talara.terra.com.br [200.154.55.136]) by itapoa.terra.com.br (Postfix) with ESMTP id 93A27DD430F for ; Wed, 11 Aug 2004 04:26:22 -0300 (BRT) Received: from [200.176.35.99] (cm-net-poa-C8B02363.brdterra.com.br [200.176.35.99]) (authenticated user erabbott) by talara.terra.com.br (Postfix) with ESMTP id 5720C3C002 for ; Wed, 11 Aug 2004 04:26:22 -0300 (BRT) Message-ID: <4119CA63.8050307@galvao.eti.br> Date: Wed, 11 Aug 2004 04:27:31 -0300 From: =?ISO-8859-15?Q?Er_Galv=E3o_Abbott?= Reply-To: galvao@galvao.eti.br User-Agent: Mozilla Thunderbird 0.7.3 (Windows/20040803) X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: NUMERIC x VARCHAR References: <4119B1C9.2010800@galvao.eti.br> In-Reply-To: Content-Type: text/html; charset=ISO-8859-15 Content-Transfer-Encoding: 8bit X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=2.4 tagged_above=0.0 required=5.0 tests=HTML_40_50, HTML_MESSAGE, HTML_TITLE_EMPTY, MIME_HTML_ONLY, RCVD_IN_NJABL, RCVD_IN_NJABL_PROXY, RCVD_IN_SORBS X-Spam-Level: ** X-Archive-Number: 200408/151 X-Sequence-Number: 7787 It will. As I've said I wont be storing any symbols.

 
-- 
Er Galv�o Abbott
Desenvolvedor Web
http://www.galvao.eti.br/
galvao@galvao.eti.br


Pierre-Fr�d�ric Caillaud wrote:

Numeric won't store that :

����(+33) 4 01 23 45 67

On Wed, 11 Aug 2004 02:42:33 -0300, Er Galv�o Abbott� <galvao@galvao.eti.br> wrote:

Greetings.

I have a question regarding performance of certain datatypes:

I have a field where I will store my clients phone numbers. I know that� this
field will never exceed 15 characters, and I will store only numbers� here (no
dashes, dots, etc...), so I was wondering:

Wich type is faster: NUMERIC(15,0) or VARCHAR(15)? Are there any storage
differences between them?

TIA,




---------------------------(end of broadcast)---------------------------
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From pgsql-performance-owner@postgresql.org  Wed Aug 11 04:42:05 2004
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From: Michael Glaesemann 
Subject: Re: NUMERIC x VARCHAR
Date: Wed, 11 Aug 2004 16:41:25 +0900
To: galvao@galvao.eti.br
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On Aug 11, 2004, at 4:27 PM, Er Galv=E3o Abbott wrote:

> It will. As I've said I wont be storing any symbols.

It won't store leading zeros, however. This may or may not be an issue=20
for you.


test=3D# create table tel (name_id integer not null, tel_numeric=20
numeric(15) not null, tel_varchar varchar(15) not null);
CREATE TABLE
test=3D# insert into tel (name_id, tel_numeric, tel_varchar) values=20
(1,012345678911234, '012345678911234');
INSERT 17153 1
test=3D# select * from tel;
  name_id |  tel_numeric   |   tel_varchar
---------+----------------+-----------------
        1 | 12345678911234 | 012345678911234
(1 row)

I would do as another poster suggested: create a telephone number=20
domain as text with the check constraints you desire.

Michael Glaesemann
grzm myrealbox com


From pgsql-performance-owner@postgresql.org  Wed Aug 11 09:22:37 2004
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Subject: Re: Hardware upgrade for a high-traffic database
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Thread-Topic: [PERFORM] Hardware upgrade for a high-traffic database
thread-index: AcR/Lr47tKJaxYJUST64s429yuXv/gADnnNwABef6VA=
From: "Merlin Moncure" 
To: "Jason Coene" 
Cc: "Postgresql Performance" 
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> The issue that I think we're seeing is that the performance on the
3Ware
> RAID is quite bad, watching FreeBSD systat will show it at "100% busy"
at
> around "3.5 MB/s".  When it needs to seek across a table (for, say, an
> aggregate function - typically a COUNT()), it slows the entire server
down
> while working on the disk.  Additionally, VACUUM's make the server
> practically useless.  We have indexes on everything that's used in
> queries,
> and the planner is using them.

It sounds to me like your application is CPU bound, except when
vacuuming...then your server is just overloaded.  A higher performance
i/o system will help when vacuuming and checkpointing but will not solve
the overall problem.=20=20

With a (good & well supported) battery backed raid controller you can
turn fsync back on which will help you with your i/o storm issues (plus
the safety issue).   This will be particularly important if you follow
my next suggestion.

One thing you might consider is materialized views.  Your aggregate
functions are killing you...try to avoid using them (except min/max on
an index).  Just watch out for mutable functions like now().

http://www.varlena.com/varlena/GeneralBits/Tidbits/matviews.html

An application specific approach is to use triggers to keep the data you
need in as close to query form as possible...you can reap enormous
savings particularly if your queries involve 3 or more tables or have
large aggregate scans.

Merlin

=20

From pgsql-performance-owner@postgresql.org  Wed Aug 11 11:49:32 2004
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To: pgsql-performance@postgresql.org
From: Jesper Krogh 
Subject: Storing binary data.
Date: Wed, 11 Aug 2004 14:29:46 +0000 (UTC)
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Hi. 

Please be a bit patient.. I'm quite new to PostgreSQL. 

I'd like some advise on storing binary data in the database. 

Currently I have about 300.000 320.000 Bytes "Bytea" records in the
database. It works quite well but I have a feeling that it actually is
slowing the database down on queries only related to the surrounding
attributes. 

The "common" solution, I guess would be to store them in the filesystem
instead, but I like to have them just in the database it is nice clean
database and application design and if I can get PostgreSQL to "not
cache" them then it should be excactly as fast i assume. 

The binary data is not a part of most queries in the database only a few
explicitly written to fetch them and they are not accessed very often. 

What do people normally do? 


Thanks, Jesper

-- 
./Jesper Krogh, jesper@krogh.cc
Jabber ID: jesper@jabbernet.dk



From pgsql-performance-owner@postgresql.org  Wed Aug 11 12:33:58 2004
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From: Shridhar Daithankar 
To: Jesper Krogh 
Subject: Re: Storing binary data.
Date: Wed, 11 Aug 2004 20:42:50 +0530
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On Wednesday 11 Aug 2004 7:59 pm, Jesper Krogh wrote:
> The "common" solution, I guess would be to store them in the filesystem
> instead, but I like to have them just in the database it is nice clean
> database and application design and if I can get PostgreSQL to "not
> cache" them then it should be excactly as fast i assume.

You can normalize them so that a table contains an id and a bytea column only. 
Te main table will contain all the other attributes and a mapping id. That 
way you will have only the main table cached.

You don't have to go to filesystem for this, I hope.

HTH

 Shridhar

From pgsql-performance-owner@postgresql.org  Wed Aug 11 13:23:38 2004
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On Wed, 2004-08-11 at 17:51, Merlin Moncure wrote:

> One thing you might consider is materialized views.  Your aggregate
> functions are killing you...try to avoid using them (except min/max on
> an index).  Just watch out for mutable functions like now().
> 
> http://www.varlena.com/varlena/GeneralBits/Tidbits/matviews.html
> 
> An application specific approach is to use triggers to keep the data you
> need in as close to query form as possible...you can reap enormous
> savings particularly if your queries involve 3 or more tables or have
> large aggregate scans.

I thought materialized views support in pgsql was experimental as yet.
Are the pg mat-view code upto production servers? Also, do you have to
delete mat-views before you dump the db or does dump automatically not
dump the mat-views data?

Sanjay.



From pgsql-performance-owner@postgresql.org  Wed Aug 11 13:47:17 2004
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To: Jesper Krogh 
Cc: pgsql-performance@postgresql.org
Subject: Re: Storing binary data. 
In-reply-to:  
References: 
Comments: In-reply-to Jesper Krogh 
	message dated "Wed, 11 Aug 2004 14:29:46 -0000"
Date: Wed, 11 Aug 2004 12:06:38 -0400
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From: Tom Lane 
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Jesper Krogh  writes:
> I'd like some advise on storing binary data in the database. 

> Currently I have about 300.000 320.000 Bytes "Bytea" records in the
> database. It works quite well but I have a feeling that it actually is
> slowing the database down on queries only related to the surrounding
> attributes. 

> The "common" solution, I guess would be to store them in the filesystem
> instead, but I like to have them just in the database it is nice clean
> database and application design and if I can get PostgreSQL to "not
> cache" them then it should be excactly as fast i assume. 

> The binary data is not a part of most queries in the database only a few
> explicitly written to fetch them and they are not accessed very often. 

> What do people normally do? 

Nothing.  If the bytea values are large enough to be worth splitting
out, Postgres will actually do that for you automatically.  Wide field
values get pushed into a separate "toast" table, and are not fetched by
a query unless the value is specifically demanded.

You can control this behavior to some extent by altering the storage
option for the bytea column (see ALTER TABLE), but the default choice
is usually fine.

If you just want to see whether anything is happening, do a VACUUM
VERBOSE on that table and note the amount of storage in the toast table
as compared to the main table.

			regards, tom lane

From pgsql-general-owner@postgresql.org  Wed Aug 11 13:28:34 2004
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On Wed, Aug 04, 2004 at 14:00:39 +0200,
  Ulrich Wisser  wrote:

This topic really belongs on the performance list. I have copied that
list and set followups to go there and copy you.

> 
> my web application grows slower and slower over time. After some 
> profiling I came to the conclusion that my SQL queries are the biggest 
> time spenders (25 seconds). Obviously I need to optimise my queries and 
> maybe introduce some new indexes.

This sounds like you aren't doing proper maintainance. You need to be
vacuuming with a large enough FSM setting.

> The problem is, that my application uses dynamic queries. I therefor can 
> not determine what are the most common queries.
> 
> I have used the postgresql logging ption before. Is there a tool to 
> analyze the logfile for the most common and/or most time consuming queries?

You can log queries that run for at least a specified amount of time.
This will be useful in finding what the long running queries are.
You can then use explain analyse to see why they are long running.

From pgsql-performance-owner@postgresql.org  Wed Aug 11 15:02:12 2004
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To: pgsql-performance@postgresql.org
From: Jesper Krogh 
Subject: Re: Storing binary data.
Date: Wed, 11 Aug 2004 16:29:33 +0000 (UTC)
Lines: 32
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References: 
	<200408112042.50356.shridhar@frodo.hserus.net>
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I gmane.comp.db.postgresql.performance, skrev Shridhar Daithankar:
>  On Wednesday 11 Aug 2004 7:59 pm, Jesper Krogh wrote:
> > The "common" solution, I guess would be to store them in the filesystem
> > instead, but I like to have them just in the database it is nice clean
> > database and application design and if I can get PostgreSQL to "not
> > cache" them then it should be excactly as fast i assume.
> 
>  You can normalize them so that a table contains an id and a bytea column only. 
>  Te main table will contain all the other attributes and a mapping id. That 
>  way you will have only the main table cached.
> 
>  You don't have to go to filesystem for this, I hope.

Further benchmarking. 

I tried to create a table with the excact same attributes but without
the binary attribute. It didn't change anything, so my idea that it
should be the binary-stuff that sloved it down was wrong. 

I have a timestamp column in the table that I sort on. Data is ordered
over the last 4 years and I select based on a timerange, I cannot make
the query-planner use the index on the timestamp by itself but if I "set
enable_seqscan = false" the query time drops by 1/3 (from 1.200 msec to
about 400 msec). 

I cannot figure out why the query-planner chooses wrong. 
NB: It's postgresql 7.4.3

-- 
./Jesper Krogh, jesper@krogh.cc
Jabber ID: jesper@jabbernet.dk



From pgsql-performance-owner@postgresql.org  Wed Aug 11 15:05:05 2004
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Thread-Topic: [PERFORM] fsync vs open_sync
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From: "Merlin Moncure" 
To: "Josh Berkus" 
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> OSDL did some testing and found Ext3 to be perhaps the worst FS for
> PostgreSQL
> -- although this testing was with the default options.   Ext3 involved
an
> almost 40% write performance penalty compared with Ext2, whereas the
> penalty
> for ReiserFS and JFS was less than 10%.
>=20
> This concurs with my personal experience.

I'm really curious to see if you guys have compared insert performance
results between 7.4 and 8.0.  As you probably know the system sync()
call was replaced with a looping fsync on open file handles.  This may
have some interesting interactions with the WAL sync method.

What caught my attention initially was the 300+/sec insert performance.
On 8.0/NTFS/fsync=3Don, I can't break 100/sec on a 10k rpm ATA disk.  My
hardware seems to be more or less in the same league as psql's, so I was
naturally curious if this was a NT/Unix issue, a 7.4/8.0 issue, or a
combination of both.

A 5ms seek time disk would be limited to 200 transaction commits/sec if
each transaction commit has at least 1 seek.  Are there some
circumstances where a transaction commit does not generate a physical
seek?=20=20

Maybe ext3 is not the worst filesystem after all!

Merlin

From pgsql-performance-owner@postgresql.org  Wed Aug 11 14:43:23 2004
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Subject: Re: Hardware upgrade for a high-traffic database
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From: "Merlin Moncure" 
To: 
Cc: "Postgresql Performance" ,
	
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> On Wed, 2004-08-11 at 17:51, Merlin Moncure wrote:
>=20
> > One thing you might consider is materialized views.  Your aggregate
> > functions are killing you...try to avoid using them (except min/max
on
> > an index).  Just watch out for mutable functions like now().
> >
> > http://www.varlena.com/varlena/GeneralBits/Tidbits/matviews.html
> >
> > An application specific approach is to use triggers to keep the data
you
> > need in as close to query form as possible...you can reap enormous
> > savings particularly if your queries involve 3 or more tables or
have
> > large aggregate scans.
>=20
> I thought materialized views support in pgsql was experimental as yet.
> Are the pg mat-view code upto production servers? Also, do you have to
> delete mat-views before you dump the db or does dump automatically not
> dump the mat-views data?

I think you are thinking about 100% 'true' materialized views.  In that
case the answer is no, the server does not have them.  The GeneralBits
article describes how to emulate them through pl/sql triggers.  I just
bumped into the article yesterday and was very impressed by it...I have
to admin though Note: I have never tried the method, but it should work.
I cc'd the author who perhaps might chime in and tell you more about
them.

Materialized views can give performance savings so good that the tpc
people had to ban them from benchmarks because they skewed results...:)
In postgres, they can help a lot with aggregates...there are many
gotchas tho, for example keeping a count() up to date can get kind of
tricky.  If you can get them to work, the filesystem cache efficiency
will rocket upwards...YMMV.

Getting back on topic, I missed the original post where the author
stated his problems were i/o related, not cpu (contrary to my
speculation).  I wonder what his insert/update load is?

Merlin



From pgsql-performance-owner@postgresql.org  Wed Aug 11 14:41:56 2004
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Date: Wed, 11 Aug 2004 14:13:47 -0300
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	<4119CA63.8050307@galvao.eti.br>
	
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Thanks, Michael.



You and "Evil Azrael" (lol) got me. Never thought about leading zeros.



Varchar it is!



Thanks a lot,


-- 
Er Galvão Abbott
Desenvolvedor Web
http://www.galvao.eti.br/
galvao@galvao.eti.br





Michael Glaesemann wrote:




On Aug 11, 2004, at 4:27 PM, Er Galvão Abbott wrote:
  

  

  
It will. As I've said I wont be storing any
symbols.
    

  

  

It won't store leading zeros, however. This may or may not be an issue
for you.
  

  

  

test=# create table tel (name_id integer not null, tel_numeric
numeric(15) not null, tel_varchar varchar(15) not null);
  

CREATE TABLE
  

test=# insert into tel (name_id, tel_numeric, tel_varchar) values
(1,012345678911234, '012345678911234');
  

INSERT 17153 1
  

test=# select * from tel;
  

 name_id |  tel_numeric   |   tel_varchar
  

---------+----------------+-----------------
  

       1 | 12345678911234 | 012345678911234
  

(1 row)
  

  

I would do as another poster suggested: create a telephone number
domain as text with the check constraints you desire.
  

  

Michael Glaesemann
  

grzm myrealbox com
  






From pgsql-performance-owner@postgresql.org  Fri Aug 13 12:42:11 2004
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Date: Wed, 11 Aug 2004 13:14:05 -0400 (EDT)
Subject: Re: fsync vs open_sync
To: "Merlin Moncure" 
Cc: "Josh Berkus" ,
	pgsql-performance@postgresql.org
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>> OSDL did some testing and found Ext3 to be perhaps the worst FS for
>> PostgreSQL
>> -- although this testing was with the default options.   Ext3 involved
> an
>> almost 40% write performance penalty compared with Ext2, whereas the
>> penalty
>> for ReiserFS and JFS was less than 10%.
>>
>> This concurs with my personal experience.
>
> I'm really curious to see if you guys have compared insert performance
> results between 7.4 and 8.0.  As you probably know the system sync()
> call was replaced with a looping fsync on open file handles.  This may
> have some interesting interactions with the WAL sync method.
>
> What caught my attention initially was the 300+/sec insert performance.
> On 8.0/NTFS/fsync=on, I can't break 100/sec on a 10k rpm ATA disk.  My
> hardware seems to be more or less in the same league as psql's, so I was
> naturally curious if this was a NT/Unix issue, a 7.4/8.0 issue, or a
> combination of both.

The system on which I can get 300 inserts per second is a battery backed
up XEON system with 512M RAM, a Promise PDC DMA ATA card, and some fast
disks with write caching enabled.

(We are not worried about write caching because we have a UPS. Since all
non-redundent systems are evaluated on probability of error, we decided
that the probability of power failure and UPS failure was sufficiently
more rare than system crash with file system corruption or hard disk
failure.)
>
> A 5ms seek time disk would be limited to 200 transaction commits/sec if
> each transaction commit has at least 1 seek.  Are there some
> circumstances where a transaction commit does not generate a physical
> seek?
>
> Maybe ext3 is not the worst filesystem after all!
>
> Merlin
>


From pgsql-general-owner@postgresql.org  Wed Aug 11 15:46:58 2004
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	Wed, 11 Aug 2004 11:41:43 PDT
Date: Wed, 11 Aug 2004 11:41:43 -0700 (PDT)
From: Karam Chand 
Subject: My admin left the job and I am stuck
To: pgsql-general@postgresql.org
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Hello,

My linux admin left the job. We had a PostgreSQL
installed under his username. He used to maintain it.
Now I am looking at the Linux box and I am just a
super duper newbie in Linux administration.

The previosu admin had a database created under his
name coz PostgreSQL dosnt allow root database.

Now I want to get the data back and use it? I dont
mind if I have to use a different DB?

I dont even know where he isntalled the PostgreSQL
binaries and data?

Where can I all this information?

I am feeling really stupid but thank GOD we dont have
any live databases running?

Regards,
Karam


		
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From pgsql-performance-owner@postgresql.org  Wed Aug 11 16:17:31 2004
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From: "Jason Coene" 
To: "'Merlin Moncure'" 
Cc: "'Postgresql Performance'" 
Subject: Re: Hardware upgrade for a high-traffic database
Date: Wed, 11 Aug 2004 15:08:42 -0400
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Thanks for all the feedback.  To clear it up, we are definitely not CPU
bound at the moment.  Any slowdown seems to be disk dependant, or from to
serialization due to a long query (due to disk).

We do have a lot of INSERT/UPDATE calls, specifically on tables that track
user sessions, then of course things like comments, etc (where we'll see
10-30 INSERT's per second, with TEXT field, and hundreds of reads per
second).  Additionally, our system does use a lot of aggregate functions.
I'll look into materialized views, it sounds like it may be worth
implementing.

One question I do have though - you specifically mentioned NOW() as
something to watch out for, in that it's mutable.  We typically use COUNT()
as a subselect to retrieve the number of associated rows to the current
query.  Additionally, we use NOW a lot, primarily to detect the status of a
date, i.e.:

SELECT id FROM subscriptions WHERE userid = 11111 AND timeend > NOW();

Is there a better way to do this?  I was under the impression that NOW() was
pretty harmless, just to return a current timestamp.

Based on feedback, I'm looking at a minor upgrade of our RAID controller to
a 3ware 9000 series (SATA with cache, battery backup optional), and
re-configuring it for RAID 10.  It's a damn cheap upgrade at around $350 and
an hour of downtime, so I figure that it's worth it for us to give it a
shot.

Thanks,

Jason


-----Original Message-----
From: pgsql-performance-owner@postgresql.org
[mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Merlin Moncure
Sent: Wednesday, August 11, 2004 1:04 PM
To: skpobox@gawab.com
Cc: Postgresql Performance; jgardner@jonathangardner.net
Subject: Re: [PERFORM] Hardware upgrade for a high-traffic database

> On Wed, 2004-08-11 at 17:51, Merlin Moncure wrote:
> 
> > One thing you might consider is materialized views.  Your aggregate
> > functions are killing you...try to avoid using them (except min/max
on
> > an index).  Just watch out for mutable functions like now().
> >
> > http://www.varlena.com/varlena/GeneralBits/Tidbits/matviews.html
> >
> > An application specific approach is to use triggers to keep the data
you
> > need in as close to query form as possible...you can reap enormous
> > savings particularly if your queries involve 3 or more tables or
have
> > large aggregate scans.
> 
> I thought materialized views support in pgsql was experimental as yet.
> Are the pg mat-view code upto production servers? Also, do you have to
> delete mat-views before you dump the db or does dump automatically not
> dump the mat-views data?

I think you are thinking about 100% 'true' materialized views.  In that
case the answer is no, the server does not have them.  The GeneralBits
article describes how to emulate them through pl/sql triggers.  I just
bumped into the article yesterday and was very impressed by it...I have
to admin though Note: I have never tried the method, but it should work.
I cc'd the author who perhaps might chime in and tell you more about
them.

Materialized views can give performance savings so good that the tpc
people had to ban them from benchmarks because they skewed results...:)
In postgres, they can help a lot with aggregates...there are many
gotchas tho, for example keeping a count() up to date can get kind of
tricky.  If you can get them to work, the filesystem cache efficiency
will rocket upwards...YMMV.

Getting back on topic, I missed the original post where the author
stated his problems were i/o related, not cpu (contrary to my
speculation).  I wonder what his insert/update load is?

Merlin



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On 8/11/2004 2:21 AM, Scott Marlowe wrote:

> On Tue, 2004-08-10 at 23:42, Er Galvão Abbott wrote:
>> Greetings.
>> 
>> I have a question regarding performance of certain datatypes:
>> 
>> I have a field where I will store my clients phone numbers. I know
>> that this field will never exceed 15 characters, and I will store only
>> numbers here (no dashes, dots, etc...), so I was wondering:
>> 
>> Wich type is faster: NUMERIC(15,0) or VARCHAR(15)? Are there any
>> storage differences between them?
> 
> Since numerics are stored as text strings, the storage would be
> similar.  Numerics, however, may be slower since they have more
> constraints built in.  If you throw a check constraint on the
> varchar(15) then it will likely be about the same speed for updating.

They are stored as an array of signed small integers holding digits in 
base-10000, plus a precision, scale and sign. That's somewhat different 
from text strings, isn't it?


Jan

> 
> text type with a check contraint it what i'd use.  That way if you want
> to change it at a later date you just drop and recreate your constraint.
> 
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From pgsql-performance-owner@postgresql.org  Wed Aug 11 16:42:48 2004
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Cc: "'Merlin Moncure'" ,
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From: Brian Hirt 
Subject: Re: Hardware upgrade for a high-traffic database
Date: Wed, 11 Aug 2004 13:39:38 -0600
To: "Jason Coene" 
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Jason,,

One suggestion i have, stay away from adaptec ZCR RAID products, we've 
been doing testing on them, and they don't perform well at all.

--brian

On Aug 11, 2004, at 1:08 PM, Jason Coene wrote:

> Thanks for all the feedback.  To clear it up, we are definitely not CPU
> bound at the moment.  Any slowdown seems to be disk dependant, or from 
> to
> serialization due to a long query (due to disk).


From pgsql-performance-owner@postgresql.org  Wed Aug 11 17:02:45 2004
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> We do have a lot of INSERT/UPDATE calls, specifically on tables that
track
> user sessions, then of course things like comments, etc (where we'll
see
> 10-30 INSERT's per second, with TEXT field, and hundreds of reads per
> second).  Additionally, our system does use a lot of aggregate
functions.
> I'll look into materialized views, it sounds like it may be worth
> implementing.

Right.  The point is: is your i/o bottle neck on the read side or the
write side.  With 10-30 inserts/sec and fsync off, it's definitely on
the read side.  What's interesting is that such a low insert load is
causing i/o storm problems.  How does your app run with fsync on?

With read-bound i/o problems, might want to consider upgrading memory
first to get better cache efficiency.  You may want to consider Opteron
for > 4GB allocations (yummy!).

The good news is that read problems are usually solvable by being
clever, whereas write problems require hardware.

> One question I do have though - you specifically mentioned NOW() as
> something to watch out for, in that it's mutable.  We typically use

This is specifically with regards to materialized views.  Mutable
functions cause problems because when they are pushed unto the view,
they are refreshed...something to watch out for.

The trick with MVs is to increase your filesystem cache efficiency.  The
big picture is to keep frequently read data in a single place to make
better benefit of cache.  Aggregates naturally read multiple rows to
return a single row's worth of data so you want to target them first.
This all comes at a cost of update I/O time and some application
complexity.

> as a subselect to retrieve the number of associated rows to the
current
> query.  Additionally, we use NOW a lot, primarily to detect the status
of
> a
> date, i.e.:

Might want to check if your application middleware (php?) exposes
PQntuples()...this is a zero cost way to get the same information.
=20
> Based on feedback, I'm looking at a minor upgrade of our RAID
controller
> to
> a 3ware 9000 series (SATA with cache, battery backup optional), and
> re-configuring it for RAID 10.  It's a damn cheap upgrade at around
$350
> and
> an hour of downtime, so I figure that it's worth it for us to give it
a
> shot.

p.s. you can also increase cache efficiency by reducing database size,
for example use int2/int4 vs. numerics.

Good luck!

From pgsql-performance-owner@postgresql.org  Wed Aug 11 17:52:48 2004
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Subject: Re: [HACKERS] fsync vs open_sync
From: Steve Bergman 
To: Josh Berkus 
Cc: Merlin Moncure , pgsql@mohawksoft.com,
	pgsql-perform 
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On Tue, 2004-08-10 at 10:18 -0700, Josh Berkus wrote:
> Guys, just so you know:
> 
> OSDL did some testing and found Ext3 to be perhaps the worst FS for PostgreSQL 
> -- although this testing was with the default options.   Ext3 involved an 
> almost 40% write performance penalty compared with Ext2, whereas the penalty 
> for ReiserFS and JFS was less than 10%.  
> 
> This concurs with my personal experience.
> 

Yes, I have been wondering about the relative trade offs between
underlying file systems and pgsql.

For metadata journalled filesystems, wouldn't fdatasync be a better
option, since the fs is journalling the metadata anyway?

With its default settings (data=ordered), ext3 is making a guaranty that
after a crash, the filesystem will not only be in a consistent state,
but the files (including the WAL) will not contain garbage, though their
contents may not be the latest.  With reiserfs and JFS, files can
contain garbage. (I'm not sure what the implications of all this for
pgsql are.)

And wouldn't the following comparisons with ext3 be more interesting:

ext3,data=writeback,fdatasync vs Other_Journalled_FS,fdatasync

or 

ext3,data=journal,open_sync vs Other_Journalled_FS,fdatasync

Just wondering.

-Steve


From pgsql-performance-owner@postgresql.org  Wed Aug 11 18:18:51 2004
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Subject: Re: Hardware upgrade for a high-traffic database
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> 
> Right.  The point is: is your i/o bottle neck on the read side or the
> write side.  With 10-30 inserts/sec and fsync off, it's definitely on
> the read side.  What's interesting is that such a low insert load is
> causing i/o storm problems.  How does your app run with fsync on?
> 
> With read-bound i/o problems, might want to consider upgrading memory
> first to get better cache efficiency.  You may want to consider Opteron
> for > 4GB allocations (yummy!).
> 
> The good news is that read problems are usually solvable by being
> clever, whereas write problems require hardware.
> 

The difference with fsync being off makes seems to be that it allows the
server to write in groups instead of scattering our INSERT/UPDATE calls all
over - it helps keep things going.  When a checkpoint occurs, reads slow
down there.  Normal reads are usually quite fast, aside from some reads.

A good example, a comments table where users submit TEXT data.  A common
query is to find the last 5 comments a user has submitted.  The scan, while
using an index, takes a considerable amount of time (> 0.5 sec is about as
good as it gets).  Again, it's using an index on the single WHERE clause
(userid = int).  The field that's used to ORDER BY (timestamp) is also
indexed.

I'm wondering why our PG server is using so little memory...  The system has
2GB of memory, though only around 200MB of it are used.  Is there a PG
setting to force more memory usage towards the cache?  Additionally, we use
FreeBSD.  I've heard that Linux may manage that memory better, any truth
there?  Sorry if I'm grabbing at straws here :)

> > One question I do have though - you specifically mentioned NOW() as
> > something to watch out for, in that it's mutable.  We typically use
> 
> This is specifically with regards to materialized views.  Mutable
> functions cause problems because when they are pushed unto the view,
> they are refreshed...something to watch out for.
> 
> The trick with MVs is to increase your filesystem cache efficiency.  The
> big picture is to keep frequently read data in a single place to make
> better benefit of cache.  Aggregates naturally read multiple rows to
> return a single row's worth of data so you want to target them first.
> This all comes at a cost of update I/O time and some application
> complexity.
> 
> > as a subselect to retrieve the number of associated rows to the
> current
> > query.  Additionally, we use NOW a lot, primarily to detect the status
> of
> > a
> > date, i.e.:
> 
> Might want to check if your application middleware (php?) exposes
> PQntuples()...this is a zero cost way to get the same information.
> 

Thanks, I'll look into it.  We use C and PHP.

> > Based on feedback, I'm looking at a minor upgrade of our RAID
> controller
> > to
> > a 3ware 9000 series (SATA with cache, battery backup optional), and
> > re-configuring it for RAID 10.  It's a damn cheap upgrade at around
> $350
> > and
> > an hour of downtime, so I figure that it's worth it for us to give it
> a
> > shot.
> 
> p.s. you can also increase cache efficiency by reducing database size,
> for example use int2/int4 vs. numerics.
> 

I've gone through and optimized data types as much as possible.  I'll see
what else we can do w/o causing downtime once PG 8 is ready to go and we can
change data types on the fly.

Thanks,

Jason


From pgsql-performance-owner@postgresql.org  Wed Aug 11 18:31:59 2004
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Subject: Re: Hardware upgrade for a high-traffic database
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On Aug 11, 2004, at 3:18 PM, Jason Coene wrote:
>
> I'm wondering why our PG server is using so little memory...  The 
> system has
> 2GB of memory, though only around 200MB of it are used.  Is there a PG
> setting to force more memory usage towards the cache?  Additionally, 
> we use
> FreeBSD.  I've heard that Linux may manage that memory better, any 
> truth
> there?  Sorry if I'm grabbing at straws here :)
>

i don't know about freebsd, but linux is very aggressive about using 
unused memory for disk cache.  we have dedicated linux box running pg 
with 2gb of memory,   about 250mb of memory is being used by processes 
(system+postgres) and shared memory (postgres only), and there is 
1.75gb of disk buffers in use in the kernel.  this particular database 
is only about 4gb, so a good portion of the db resides in memory, 
certainly most of the active set.  the disk subsystem is a 6 disk scsi 
u160 raid array which performs pretty well when there is io.


From pgsql-performance-owner@postgresql.org  Wed Aug 11 18:46:34 2004
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Subject: Re: Hardware upgrade for a high-traffic database
From: Rod Taylor 
To: Jason Coene 
Cc: 'Merlin Moncure' ,
	Postgresql Performance 
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> I'm wondering why our PG server is using so little memory...  The system has
> 2GB of memory, though only around 200MB of it are used.  Is there a PG

This is the second time you've said this. Surely you're not implying
there is 1.8GB Free Memory -- rather than 1.8GB in Buffers or Cache.

Send output of the below:

sysctl vm

sysctl -a | grep buffers

top | grep -E "(Mem|Swap):"



From pgsql-performance-owner@postgresql.org  Wed Aug 11 18:52:12 2004
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Subject: Re: Hardware upgrade for a high-traffic database
From: Rod Taylor 
To: Brian Hirt 
Cc: Jason Coene ,
	'Postgresql Performance' 
In-Reply-To: 
References: <200408112118.i7BLIR0E097522@mail.gotfrag.com>
	
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On Wed, 2004-08-11 at 17:31, Brian Hirt wrote:
> On Aug 11, 2004, at 3:18 PM, Jason Coene wrote:
> >
> > I'm wondering why our PG server is using so little memory...  The 
> > system has
> > 2GB of memory, though only around 200MB of it are used.  Is there a PG
> > setting to force more memory usage towards the cache?  Additionally, 
> > we use
> > FreeBSD.  I've heard that Linux may manage that memory better, any 
> > truth
> > there?  Sorry if I'm grabbing at straws here :)
> >
> 
> i don't know about freebsd, but linux is very aggressive about using 
> unused memory for disk cache.  we have dedicated linux box running pg 

Aggressive indeed.. I'm stuck with the version that has a tendency to
swap out active processes rather than abandon disk cache -- it gets very
annoying!



From pgsql-performance-owner@postgresql.org  Wed Aug 11 19:03:54 2004
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From: "Jason Coene" 
To: "'Rod Taylor'" ,
	"'Merlin Moncure'" 
Cc: "'Postgresql Performance'" 
Subject: Re: Hardware upgrade for a high-traffic database
Date: Wed, 11 Aug 2004 18:03:40 -0400
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> -----Original Message-----
> From: Rod Taylor [mailto:pg@rbt.ca]
> Sent: Wednesday, August 11, 2004 5:46 PM
> To: Jason Coene
> Cc: 'Merlin Moncure'; Postgresql Performance
> Subject: Re: [PERFORM] Hardware upgrade for a high-traffic database
> 
> > I'm wondering why our PG server is using so little memory...  The system
> has
> > 2GB of memory, though only around 200MB of it are used.  Is there a PG
> 
> This is the second time you've said this. Surely you're not implying
> there is 1.8GB Free Memory -- rather than 1.8GB in Buffers or Cache.

Hi Rod,

I was looking at top and vmstat - which always show under 300MB "Active".
We may hit 400MB at peak.  Everything I see (though this isn't my area of
expertise) points to most of the memory simply being unused.  Results below,
am I missing something?

Jason

> 
> Send output of the below:
> 
> sysctl vm

d01> sysctl vm
vm.vmtotal:
System wide totals computed every five seconds: (values in kilobytes)
===============================================
Processes:              (RUNQ: 1 Disk Wait: 0 Page Wait: 0 Sleep: 149)
Virtual Memory:         (Total: 2101614K, Active 440212K)
Real Memory:            (Total: 2023532K Active 327032K)
Shared Virtual Memory:  (Total: 14356K Active: 3788K)
Shared Real Memory:     (Total: 4236K Active: 2456K)
Free Memory Pages:      88824K

vm.loadavg: { 0.46 0.41 0.42 }
vm.v_free_min: 3312
vm.v_free_target: 13997
vm.v_free_reserved: 749
vm.v_inactive_target: 20995
vm.v_cache_min: 13997
vm.v_cache_max: 27994
vm.v_pageout_free_min: 34
vm.pageout_algorithm: 0
vm.swap_enabled: 1
vm.swap_async_max: 4
vm.dmmax: 32
vm.nswapdev: 1
vm.swap_idle_threshold1: 2
vm.swap_idle_threshold2: 10
vm.v_free_severe: 2030
vm.stats.sys.v_swtch: 627853362
vm.stats.sys.v_trap: 3622664114
vm.stats.sys.v_syscall: 1638589210
vm.stats.sys.v_intr: 3250875036
vm.stats.sys.v_soft: 1930666043
vm.stats.vm.v_vm_faults: 3197534554
vm.stats.vm.v_cow_faults: 2999625102
vm.stats.vm.v_cow_optim: 10093309
vm.stats.vm.v_zfod: 3603956919
vm.stats.vm.v_ozfod: 3104475907
vm.stats.vm.v_swapin: 3353
vm.stats.vm.v_swapout: 3382
vm.stats.vm.v_swappgsin: 3792
vm.stats.vm.v_swappgsout: 7213
vm.stats.vm.v_vnodein: 14675
vm.stats.vm.v_vnodeout: 140671
vm.stats.vm.v_vnodepgsin: 24330
vm.stats.vm.v_vnodepgsout: 245840
vm.stats.vm.v_intrans: 3643
vm.stats.vm.v_reactivated: 35038
vm.stats.vm.v_pdwakeups: 26984
vm.stats.vm.v_pdpages: 335769007
vm.stats.vm.v_dfree: 8
vm.stats.vm.v_pfree: 1507856856
vm.stats.vm.v_tfree: 430723755
vm.stats.vm.v_page_size: 4096
vm.stats.vm.v_page_count: 512831
vm.stats.vm.v_free_reserved: 749
vm.stats.vm.v_free_target: 13997
vm.stats.vm.v_free_min: 3312
vm.stats.vm.v_free_count: 968
vm.stats.vm.v_wire_count: 62039
vm.stats.vm.v_active_count: 44233
vm.stats.vm.v_inactive_target: 20995
vm.stats.vm.v_inactive_count: 343621
vm.stats.vm.v_cache_count: 21237
vm.stats.vm.v_cache_min: 13997
vm.stats.vm.v_cache_max: 27994
vm.stats.vm.v_pageout_free_min: 34
vm.stats.vm.v_interrupt_free_min: 2
vm.stats.vm.v_forks: 45205536
vm.stats.vm.v_vforks: 74315
vm.stats.vm.v_rforks: 0
vm.stats.vm.v_kthreads: 2416
vm.stats.vm.v_forkpages: 1464383994
vm.stats.vm.v_vforkpages: 4259727
vm.stats.vm.v_rforkpages: 0
vm.stats.vm.v_kthreadpages: 0
vm.stats.misc.zero_page_count: 709
vm.stats.misc.cnt_prezero: -972664922
vm.max_proc_mmap: 34952
vm.msync_flush_flags: 3
vm.idlezero_enable: 1
vm.idlezero_maxrun: 16
vm.max_launder: 32
vm.pageout_stats_max: 13997
vm.pageout_full_stats_interval: 20
vm.pageout_stats_interval: 5
vm.pageout_stats_free_max: 5
vm.swap_idle_enabled: 0
vm.defer_swapspace_pageouts: 0
vm.disable_swapspace_pageouts: 0
vm.pageout_lock_miss: 0
vm.zone:
ITEM            SIZE     LIMIT     USED    FREE  REQUESTS

FFS2 dinode:     256,        0,  30156,   4389, 20093512
FFS1 dinode:     128,        0,      0,      0,        0
FFS inode:       140,        0,  30156,   4340, 20093512
SWAPMETA:        276,   121576,     16,    264,    44599
ripcb:           180,    32780,      0,    132,      289
hostcache:        88,    15390,      6,    309,      741
syncache:        104,    15390,      0,    418, 44592418
tcptw:            56,     6603,      3,   1204,   224900
tcpcb:           368,    32769,    136,   4264, 44594153
inpcb:           180,    32780,    139,   4437, 44594153
udpcb:           180,    32780,     10,    144,    85953
unpcb:           140,    32788,      6,    246,   143982
socket:          240,    32768,    152,   4248, 44824378
KNOTE:            64,        0,      0,    434,     7561
PIPE:            172,        0,      8,    222,   352848
NFSNODE:         460,        0,   1596,     92,     2419
NFSMOUNT:        424,        0,      1,     17,        1
DIRHASH:        1024,        0,    238,     86,      287
L VFS Cache:     291,        0,    165,    160,    11956
S VFS Cache:      68,        0,  38283,   3430,  3795133
NAMEI:          1024,        0,      0,    240, 907013101
VNODEPOLL:        60,        0,      1,    131,        2
VNODE:           260,        0,  34104,     36,    34104
g_bio:           136,        0,      0,   5887, 551700514
VMSPACE:         236,        0,    152,    987, 45279840
UPCALL:           44,        0,      0,      0,        0
KSE:              64,        0,   1224,    202,     1224
KSEGRP:          120,        0,   1224,    109,     1224
THREAD:          312,        0,   1224,     84,     1224
PROC:            452,        0,    261,    963, 45282231
Files:            68,        0,    782,   5413, 719968279
4096:           4096,        0,    441,   1935, 90066743
2048:           2048,        0,    237,    423,    25077
1024:           1024,        0,     23,    157,   448114
512:             512,        0,    108,    140,   770519
256:             256,        0,    458,   1102, 70685682
128:             128,        0,   1904,   1041, 186085712
64:               64,        0,   5124,  13042, 1404464781
32:               32,        0,   1281,   1302, 839881182
16:               16,        0,    842,   1548, 1712031683
DP fakepg:        72,        0,      0,      0,        0
PV ENTRY:         28,  2166780, 157829, 769251, 56650653911
MAP ENTRY:        60,        0,   6716,  33280, 2270740046
KMAP ENTRY:       60,    65538,     24,    702,   152938
MAP:             160,        0,      9,     41,        2
VM OBJECT:       132,        0,  21596,  10654, 1136467083
128 Bucket:      524,        0,   3115,      0,        0
64 Bucket:       268,        0,    200,     10,        0
32 Bucket:       140,        0,    191,      5,        0
16 Bucket:        76,        0,     49,      3,        0
UMA Hash:        128,        0,      0,     31,        0
UMA Slabs:        34,        0,   3095,     95,        0
UMA Zones:       432,        0,     52,      2,        0

vm.kvm_size: 1069543424
vm.kvm_free: 364900352

> 
> sysctl -a | grep buffers

d01 > sysctl -a | grep buffers
vfs.numdirtybuffers: 52
vfs.lodirtybuffers: 909
vfs.hidirtybuffers: 1819
vfs.numfreebuffers: 7146
vfs.lofreebuffers: 404
vfs.hifreebuffers: 808
> 
> top | grep -E "(Mem|Swap):"
> 

d01 > top | grep -E "(Mem|Swap):"
Mem: 173M Active, 1346M Inact, 242M Wired, 77M Cache, 112M Buf, 5784K Free
Swap: 4096M Total, 124K Used, 4096M Free


From pgsql-performance-owner@postgresql.org  Wed Aug 11 19:26:58 2004
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Subject: Re: Hardware upgrade for a high-traffic database
From: Rod Taylor 
To: Jason Coene 
Cc: 'Merlin Moncure' ,
	'Postgresql Performance' 
In-Reply-To: <200408112203.i7BM3d0E098570@mail.gotfrag.com>
References: <200408112203.i7BM3d0E098570@mail.gotfrag.com>
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On Wed, 2004-08-11 at 18:03, Jason Coene wrote:
> > -----Original Message-----
> > From: Rod Taylor [mailto:pg@rbt.ca]
> > Sent: Wednesday, August 11, 2004 5:46 PM
> > To: Jason Coene
> > Cc: 'Merlin Moncure'; Postgresql Performance
> > Subject: Re: [PERFORM] Hardware upgrade for a high-traffic database
> > 
> > > I'm wondering why our PG server is using so little memory...  The system
> > has
> > > 2GB of memory, though only around 200MB of it are used.  Is there a PG
> > 
> > This is the second time you've said this. Surely you're not implying
> > there is 1.8GB Free Memory -- rather than 1.8GB in Buffers or Cache.
> 
> Hi Rod,
> 
> I was looking at top and vmstat - which always show under 300MB "Active".
> We may hit 400MB at peak.  Everything I see (though this isn't my area of
> expertise) points to most of the memory simply being unused.  Results below,
> am I missing something?

This looks fine. The memory is not unused (only 5MB is actually empty)
but is being used for disk cache.

Active is memory used by programs and would need to be swapped if this
space was needed.

Inactive is memory that is generally dirty. Disk cache is often here. In
your case, you likely write to the same pages you're reading from --
which is why this number is so big. It also explains why a checkpoint is
a killer; a large chunk of this memory set needs to be pushed to disk.

Cache is memory used generally for disk cache that is not dirty. It's
been read from the disk and could be cleared immediately if necessary.

Wired is memory that cannot be swapped. In your case, Shared Memory is
probably Wired (this is good). There is another sysctl to check and set
whether it is wired or swappable.



Interesting (if dry) read:
http://www.freebsd.org/doc/en_US.ISO8859-1/articles/vm-design/index.html



From pgsql-performance-owner@postgresql.org  Wed Aug 11 19:57:00 2004
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From: "Jason Coene" 
To: "'Rod Taylor'" 
Cc: "'Merlin Moncure'" ,
	"'Postgresql Performance'" 
Subject: Re: Hardware upgrade for a high-traffic database
Date: Wed, 11 Aug 2004 18:53:52 -0400
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> > Hi Rod,
> >
> > I was looking at top and vmstat - which always show under 300MB
> "Active".
> > We may hit 400MB at peak.  Everything I see (though this isn't my area
> of
> > expertise) points to most of the memory simply being unused.  Results
> below,
> > am I missing something?
> 
> This looks fine. The memory is not unused (only 5MB is actually empty)
> but is being used for disk cache.
> 
> Active is memory used by programs and would need to be swapped if this
> space was needed.
> 
> Inactive is memory that is generally dirty. Disk cache is often here. In
> your case, you likely write to the same pages you're reading from --
> which is why this number is so big. It also explains why a checkpoint is
> a killer; a large chunk of this memory set needs to be pushed to disk.
> 
> Cache is memory used generally for disk cache that is not dirty. It's
> been read from the disk and could be cleared immediately if necessary.
> 
> Wired is memory that cannot be swapped. In your case, Shared Memory is
> probably Wired (this is good). There is another sysctl to check and set
> whether it is wired or swappable.
> 
> 
> 
> Interesting (if dry) read:
> http://www.freebsd.org/doc/en_US.ISO8859-1/articles/vm-design/index.html
> 

Ah, thanks - I didn't know that Inactive was still being used.  I'm glad to
know that at least the OS is using up the free memory for disk cache.
Shared memory is Wired, set via sysctl.  Thanks for the info!  It sounds
like adding more memory would help cache more data - I'll look into the
upgrade.

Jason


From pgsql-performance-owner@postgresql.org  Wed Aug 11 20:20:38 2004
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To: "Jason Coene" 
Cc: "'Merlin Moncure'" ,
	pgsql-performance@postgresql.org
Subject: Re: Hardware upgrade for a high-traffic database 
In-reply-to: <200408112118.i7BLIR0E097522@mail.gotfrag.com> 
References: <200408112118.i7BLIR0E097522@mail.gotfrag.com>
Comments: In-reply-to "Jason Coene" 
	message dated "Wed, 11 Aug 2004 17:18:27 -0400"
Date: Wed, 11 Aug 2004 19:20:04 -0400
Message-ID: <21682.1092266404@sss.pgh.pa.us>
From: Tom Lane 
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"Jason Coene"  writes:
> A good example, a comments table where users submit TEXT data.  A common
> query is to find the last 5 comments a user has submitted.  The scan, while
> using an index, takes a considerable amount of time (> 0.5 sec is about as
> good as it gets).  Again, it's using an index on the single WHERE clause
> (userid = int).  The field that's used to ORDER BY (timestamp) is also
> indexed.

You mean you are doing
    SELECT ... WHERE userid = 42 ORDER BY timestamp DESC LIMIT 5;
and hoping that separate indexes on userid and timestamp will get the
job done?  They won't.  There are only two possible plans for this,
neither very good: select all of user 42's posts and sort them, or
scan timewise backwards through *all* posts looking for the last 5 from
user 42.

If you do this enough to justify a specialized index, I would suggest a
two-column index on (userid, timestamp).  You will also need to tweak
the query, because the planner is not quite smart enough to deduce that
such an index is applicable to the given sort order:
    SELECT ... WHERE userid = 42 ORDER BY userid DESC, timestamp DESC LIMIT 5;
This should generate an index-scan-backwards plan that will execute nigh
instantaneously, because it will only fetch the rows you really want.

You might or might not be able to drop the separate indexes on userid
and timestamp, depending on what other queries you might have that need
them.  But you should be paying attention to what plans you are really
getting (see EXPLAIN) rather than just assuming that some indexes chosen
at random will do what you need.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Wed Aug 11 20:58:05 2004
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From: Russell Smith 
To: pgsql-performance@postgresql.org
Subject: Re: Storing binary data.
Date: Thu, 12 Aug 2004 09:44:56 +1000
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On Thu, 12 Aug 2004 02:29 am, Jesper Krogh wrote:
> I gmane.comp.db.postgresql.performance, skrev Shridhar Daithankar:
> >  On Wednesday 11 Aug 2004 7:59 pm, Jesper Krogh wrote:
> > > The "common" solution, I guess would be to store them in the filesystem
> > > instead, but I like to have them just in the database it is nice clean
> > > database and application design and if I can get PostgreSQL to "not
> > > cache" them then it should be excactly as fast i assume.
> > 
> >  You can normalize them so that a table contains an id and a bytea column only. 
> >  Te main table will contain all the other attributes and a mapping id. That 
> >  way you will have only the main table cached.
> > 
> >  You don't have to go to filesystem for this, I hope.
> 
> Further benchmarking. 
> 
> I tried to create a table with the excact same attributes but without
> the binary attribute. It didn't change anything, so my idea that it
> should be the binary-stuff that sloved it down was wrong. 
> 
> I have a timestamp column in the table that I sort on. Data is ordered
> over the last 4 years and I select based on a timerange, I cannot make
> the query-planner use the index on the timestamp by itself but if I "set
> enable_seqscan = false" the query time drops by 1/3 (from 1.200 msec to
> about 400 msec). 
> 
> I cannot figure out why the query-planner chooses wrong. 
> NB: It's postgresql 7.4.3
> 
Please post explain analyze of the query.

I would guess you are using now() is your query, which is not optimized perfectly
by the planner, so you end up with problems.  But if you post explain analyze 
people will be able to tell you what the problem is.

Maybe on with seqscan on, and one with it off.

Regards

Russell Smith

From pgsql-performance-owner@postgresql.org  Wed Aug 11 20:56:14 2004
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To: pgsql-performance@postgresql.org
Subject: Re: Hardware upgrade for a high-traffic database
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[snip]
> 
> One question I do have though - you specifically mentioned NOW() as
> something to watch out for, in that it's mutable.  We typically use COUNT()
> as a subselect to retrieve the number of associated rows to the current
> query.  Additionally, we use NOW a lot, primarily to detect the status of a
> date, i.e.:
> 
> SELECT id FROM subscriptions WHERE userid = 11111 AND timeend > NOW();
> 
> Is there a better way to do this?  I was under the impression that NOW() was
> pretty harmless, just to return a current timestamp.
> 
NOW() will trigger unnessecary sequence scans.  As it is unknown with prepared
query and function when the statement is run, the planner plans the query with
now as a variable.  This can push the planner to a seq scan over and index scan.
I have seen this time and time again.

You can create your own immutable now, but don't use it in functions or prepared queries
or you will get wrong results.

> Based on feedback, I'm looking at a minor upgrade of our RAID controller to
> a 3ware 9000 series (SATA with cache, battery backup optional), and
> re-configuring it for RAID 10.  It's a damn cheap upgrade at around $350 and
> an hour of downtime, so I figure that it's worth it for us to give it a
> shot.
> 
> Thanks,
> 
> Jason

Russell Smith

From pgsql-performance-owner@postgresql.org  Wed Aug 11 21:04:45 2004
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Date: Thu, 12 Aug 2004 10:00:02 +1000
From: Rudi Starcevic 
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Subject: Buld Insert and Index use.
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Hi,

This email is picking up a thread from yesterday on INSERTS and INDEXES.

In this case the question is to use and index or a sequential scan.

I have included the db DDL and SELECT query.

For each month I have a csv data dump of council property data.

So the First CD will have almost all unique records.
 From there most properties will already be in the db.

Each line of the csv file populates three tables.

gc_prop
gc_value
gc_owner

gc_prop has a one to many relationship with gc_value and gc_owner.

For-each line we first SELECT from the gc_prop table.
If there is no record we INSERT into the gc_prop,gc_value and gc_owner 
tables.

If there is a matching property we do not need to INSERT into the
gc_prop table only the gc_value and gc_owner tables.

So each row will require either:

a) One SELECT + three INSERTS
or
b) One SELECT + two INSERTS

CREATE TABLE gc_prop
(
gc_id                serial PRIMARY KEY,
acc_no                 numeric(9,0),
master_code         varchar(32),
no_prop             numeric(4,0),
lot_no                 numeric(9,0),
plan_no             varchar(32),
volume_no             numeric(8,0),
folio_no             numeric(8,0),
street_no             varchar(32),
street_name         varchar(30),
suburb_name         varchar(30),
suburb_postcode     numeric(4,0),
address1_txt         varchar(80),
address2_txt         varchar(80),
address3_txt         varchar(80),
address4_txt         varchar(80),
address5_txt         varchar(80),
address6_txt         varchar(80),
owner_postcode         text,
planning_zone         varchar(80),
waterfront_code     varchar(80),
vacant_land         varchar(32),
property_area         text,
improvemeny_type     varchar(20),
bup_indicator         varchar(4),
property_name         varchar(30),
lot_quantity         text,
pool_indicator         varchar(32),
owner_occupied         varchar(32),
prsh_text             varchar(30),
vg_no                 varchar(20),
property_part         varchar(20),
lot_no_txt             varchar(32),
plan_qualifier1     varchar(80),
plan_qualifier2     varchar(80),
owner_trans_date     date,
legal_entity         varchar(32),
"1st_surname_com"     varchar(80),
"1st_given_name"     varchar(64),
"2nd_surname"         varchar(64),
"2nd_given_name"     varchar(64),
easement_flag         varchar(32),
trans_code             varchar(32)
);

CREATE TABLE gc_value
(
gc_v_id                serial PRIMARY KEY,
gc_id                integer NOT NULL, -- foreign key to gc_prop table
current_valuation     numeric(10,0),
valuation_date         date,
last_sale_date         date,
annual_rates         numeric(7,0),
sale_amount         numeric(9,0),
type_sale             varchar(32),
date_sale             date,
pre_val_date         date,
pre_val_amount         numeric(10,0),
pre_vg_no             varchar(20),
future_val_date     varchar(32),
fut_val_amount         numeric(10,0),
fut_val_no             varchar(32)
);

CREATE TABLE gc_owner
(
gc_o_id                serial PRIMARY KEY,
gc_id                integer NOT NULL, -- foreign key to gc_prop table
pre_legal_entity    varchar(32),
pre_surname_com     varchar(76),
pre_given_name         varchar(32),
pre_2nd_surname     varchar(40),
pre_2nd_given         varchar(32),
orig_lot_no            numeric(9,0),
orig_lot_txt        varchar(32),
orig_prop_txt        text,
orig_plan_qualifier1    varchar(32),
orig_plan_qualifier2    varchar(32),
orig_plan_no         varchar(32)
);

CREATE INDEX gc_prop_check ON gc_prop ( 
acc_no,no_prop,lot_no,plan_no,street_no,street_name,suburb_postcode );

//check if this property already exists using gc_prop_check index
$sql = "
SELECT
gp.gc_id,
gp.acc_no,
gp.no_prop,
gp.lot_no,
gp.plan_no,
gp.street_no,
gp.street_name,
gp.suburb_postcode,
gp.owner_trans_date
FROM    gc_prop gp
WHERE
gp.acc_no = $acc_no,
AND
gp.no_prop = $no_prop,
AND
gp.lot_no = $lot_no
AND
gp.plan_no = '$plan_no'
AND
gp.street_no = '$street_no'
AND
gp.street_name = '$street_name'
AND
gp.suburb_postcode = $suburb_postcode
";

Do you think an Index or Seq. scan should be used?

Thanks.
Regards,
Rudi.

From pgsql-performance-owner@postgresql.org  Wed Aug 11 21:12:45 2004
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From: Gaetano Mendola 
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Hash: SHA1

pgsql@mohawksoft.com wrote:
|>>Anyway, with fsync enabled using standard fsync(), I get roughly
|>
|>300-400
|>
|>>inserts per second. With fsync disabled, I get about 7000 inserts per
|>>second. When I re-enable fsync but use the open_sync option, I can get
|>>about 2500 inserts per second.
|>
|>You are getting 300-400 inserts/sec with fsync on?  If you don't mind me
|>asking, what's your hardware?  (also, have you checked fsync on #s with
|>the new bgwriter in 7.5?)
|>
|
|
| 300 inserts persecond with fsync on using fdatasync. 2500 inserts per
| second with fsync on using open_sync.
|
| [mwoodward@penguin-021 mwoodward]$ cat /proc/cpuinfo
| processor       : 0
| vendor_id       : GenuineIntel
| cpu family      : 15
| model           : 2
| model name      : Intel(R) Xeon(TM) CPU 2.40GHz
| stepping        : 5
| cpu MHz         : 2399.373
| cache size      : 512 KB
| fdiv_bug        : no
| hlt_bug         : no
| f00f_bug        : no
| coma_bug        : no
| fpu             : yes
| fpu_exception   : yes
| cpuid level     : 2
| wp              : yes
| flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
| cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid
| bogomips        : 4784.12
|
| Linux node1 2.4.25 #1 Mon Mar 22 13:33:41 EST 2004 i686 i686 i386 GNU/Linux
|
|     ide2: BM-DMA at 0xc400-0xc407, BIOS settings: hde:pio, hdf:pio
| hde: Maxtor 6Y200P0, ATA DISK drive
| hde: attached ide-disk driver.
| hde: host protected area => 1
| hde: 398297088 sectors (203928 MB) w/7936KiB Cache, CHS=24792/255/63,
| UDMA(100)
|
| PDC20268: IDE controller at PCI slot 06:05.0


I did some experiments too:

inserting 10000 rows in a table with an integer column:

fsync=false                    ====>   ~7.5 secs  1300 insert/sec

wal_sync_method=fsync          ====>  ~15.5 secs   645 insert/sec
wal_sync_method=fdatasync      ====>  ~15.5 secs   645 insert/sec
wal_sync_method=open_sync      ====>  ~10.0 secs  1000 insert/sec
wal_sync_method=open_datasync  ====> 





Test bed:  Postgresql 8.0beta1, linux kernel 2.4.22,
~           hda: IC35L060AVVA07-0, ATA DISK drive
~           hda: 120103200 sectors (61493 MB) w/1863KiB Cache, CHS=7476/255/63, UDMA(100)


# cat /proc/cpuinfo
processor     : 0
vendor_id     : GenuineIntel
cpu family    : 6
model         : 8
model name    : Pentium III (Coppermine)
stepping      : 6
cpu MHz       : 877.500
cache size    : 256 KB
physical id   : 0
siblings      : 1
fdiv_bug      : no
hlt_bug       : no
f00f_bug      : no
coma_bug      : no
fpu           : yes
fpu_exception : yes
cpuid level   : 2
wp            : yes
flags         : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse
runqueue      : 0

bogomips      : 1749.81

processor     : 1
vendor_id     : GenuineIntel
cpu family    : 6
model         : 8
model name    : Pentium III (Coppermine)
stepping      : 6
cpu MHz       : 877.500
cache size    : 256 KB
physical id   : 0
siblings      : 1
fdiv_bug      : no
hlt_bug       : no
f00f_bug      : no
coma_bug      : no
fpu           : yes
fpu_exception : yes
cpuid level   : 2
wp            : yes
flags         : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse
runqueue      : 1

bogomips      : 1749.81




Regards
Gaetano Mendola






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From pgsql-performance-owner@postgresql.org  Wed Aug 11 21:26:05 2004
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From: Josh Berkus 
Reply-To: josh@agliodbs.com
Organization: Aglio Database Solutions
To: tech@wildcash.com, pgsql-performance@postgresql.org
Subject: Re: Buld Insert and Index use.
Date: Wed, 11 Aug 2004 17:25:55 -0700
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Rudi,

> Do you think an Index or Seq. scan should be used?

That was way too much data for way too simple a question.  ;-)
The answer is: depends on how many rows you have.   With any significant 
number of rows, yes.

However, you probably only need to index the first 3-5 columns; that's 
selective enough.

-- 
-Josh Berkus
 "A developer of Very Little Brain"
 Aglio Database Solutions
 San Francisco


From pgsql-performance-owner@postgresql.org  Wed Aug 11 21:29:10 2004
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From: "Jason Coene" 
To: "'Tom Lane'" 
Cc: "'Merlin Moncure'" ,
	
Subject: Re: Hardware upgrade for a high-traffic database 
Date: Wed, 11 Aug 2004 20:29:04 -0400
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> You mean you are doing
>     SELECT ... WHERE userid = 42 ORDER BY timestamp DESC LIMIT 5;
> and hoping that separate indexes on userid and timestamp will get the
> job done?  They won't.  There are only two possible plans for this,
> neither very good: select all of user 42's posts and sort them, or
> scan timewise backwards through *all* posts looking for the last 5 from
> user 42.

Wow!  I did try the method you state below (including the WHERE restricted
column in the sort by, and creating a two-column index), and it did execute
much faster (even on odd userid's to avoid cached results as much as
possible).

We have a lot of:

SELECT whatever
	FROM ourtable
	WHERE field1 = X
	AND field2 = Y
	AND field3 = Z
	ORDER BY id DESC
	LIMIT 5

With indexes:

ourtable(id)
ourtable(field1, field2, field3)

Is it standard procedure with postgres to include any fields listed in WHERE
in the ORDER BY, and create a single index for only the ORDER BY fields (in
order of appearance, of course)?

> 
> If you do this enough to justify a specialized index, I would suggest a
> two-column index on (userid, timestamp).  You will also need to tweak
> the query, because the planner is not quite smart enough to deduce that
> such an index is applicable to the given sort order:
>     SELECT ... WHERE userid = 42 ORDER BY userid DESC, timestamp DESC
> LIMIT 5;
> This should generate an index-scan-backwards plan that will execute nigh
> instantaneously, because it will only fetch the rows you really want.
> 
> You might or might not be able to drop the separate indexes on userid
> and timestamp, depending on what other queries you might have that need
> them.  But you should be paying attention to what plans you are really
> getting (see EXPLAIN) rather than just assuming that some indexes chosen
> at random will do what you need.
> 
> 			regards, tom lane
> 

We do many varied queries on nearly every table - our data is highly
relational, and we have a lot of indexes.  I thought the planner would pick
up the right index via constraints and not require them in ORDER BY...
EXPLAIN ANALYZE says that the indexes are being used, ala:

gf=# EXPLAIN ANALYZE SELECT id FROM comments WHERE userid = 51 ORDER BY
timestamp DESC LIMIT 5;
                                                                  QUERY PLAN
----------------------------------------------------------------------------
-------------------------------------------------------------------
 Limit  (cost=1608.43..1608.45 rows=5 width=8) (actual time=0.292..0.317
rows=5 loops=1)
   ->  Sort  (cost=1608.43..1609.45 rows=407 width=8) (actual
time=0.287..0.295 rows=5 loops=1)
         Sort Key: "timestamp"
         ->  Index Scan using comments_ix_userid on comments
(cost=0.00..1590.79 rows=407 width=8) (actual time=0.031..0.190 rows=35
loops=1)
               Index Cond: (userid = 51)
 Total runtime: 0.375 ms
(6 rows)

Is this the wrong procedure?  Your suggested syntax seems much more
efficient, but I don't quite understand exactly why, as PG is using our
existing indexes...

gf=# EXPLAIN ANALYZE SELECT id FROM comments WHERE userid = 51 ORDER BY
userid DESC, timestamp DESC LIMIT 5;
 
QUERY PLAN
----------------------------------------------------------------------------
----------------------------------------------------------------------------
----
 Limit  (cost=0.00..19.90 rows=5 width=12) (actual time=0.040..0.076 rows=5
loops=1)
   ->  Index Scan Backward using comments_ix_userid_timestamp on comments
(cost=0.00..1620.25 rows=407 width=12) (actual time=0.035..0.054 rows=5
loops=1)
         Index Cond: (userid = 51)
 Total runtime: 0.134 ms
(4 rows)

Note: This was done after adding an index on comments (userid, timestamp)

Regards,

Jason


From pgsql-performance-owner@postgresql.org  Wed Aug 11 23:09:24 2004
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To: "Jason Coene" 
Cc: "'Merlin Moncure'" ,
	pgsql-performance@postgresql.org
Subject: Re: Hardware upgrade for a high-traffic database 
In-reply-to: <200408120029.i7C0T30E002389@mail.gotfrag.com> 
References: <200408120029.i7C0T30E002389@mail.gotfrag.com>
Comments: In-reply-to "Jason Coene" 
	message dated "Wed, 11 Aug 2004 20:29:04 -0400"
Date: Wed, 11 Aug 2004 22:09:14 -0400
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From: Tom Lane 
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"Jason Coene"  writes:
> We have a lot of:

> SELECT whatever
> 	FROM ourtable
> 	WHERE field1 = X
> 	AND field2 = Y
> 	AND field3 = Z
> 	ORDER BY id DESC
> 	LIMIT 5

> With indexes:

> ourtable(id)
> ourtable(field1, field2, field3)

> Is it standard procedure with postgres to include any fields listed in WHERE
> in the ORDER BY, and create a single index for only the ORDER BY fields (in
> order of appearance, of course)?

It depends.  If the X/Y/Z constraint is already pretty selective, then
it seems sufficient to me to pick up the matching rows (using the
3-field index), sort them by id, and take the first 5.  The case where
the extra-index-column trick is useful is where the WHERE clause *isn't*
real selective and so a lot of rows would have to be sorted.  In your
previous example, I imagine you have a lot of prolific posters and so
"all posts by userid 42" can be a nontrivial set.  The double-column
index lets you skip the sort and just pull out the required rows by
scanning from the end of the range of userid = 42 entries.

> gf=# EXPLAIN ANALYZE SELECT id FROM comments WHERE userid = 51 ORDER BY
> timestamp DESC LIMIT 5;
>                                                                   QUERY PLAN
> ----------------------------------------------------------------------------
> -------------------------------------------------------------------
>  Limit  (cost=1608.43..1608.45 rows=5 width=8) (actual time=0.292..0.317
> rows=5 loops=1)
>    ->  Sort  (cost=1608.43..1609.45 rows=407 width=8) (actual
> time=0.287..0.295 rows=5 loops=1)
>          Sort Key: "timestamp"
>          ->  Index Scan using comments_ix_userid on comments
> (cost=0.00..1590.79 rows=407 width=8) (actual time=0.031..0.190 rows=35
> loops=1)
>                Index Cond: (userid = 51)
>  Total runtime: 0.375 ms
> (6 rows)

This example looks fine, but since userid 51 evidently only has 35
posts, there's not much time needed to read 'em all and sort 'em.  The
place where the double-column index will win big is on userids with
hundreds of posts.

You have to keep in mind that each index costs time to maintain during
inserts/updates.  So adding an index just because it makes a few queries
a little faster probably isn't a win.  You need to make tradeoffs.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Thu Aug 12 03:49:42 2004
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To: "Jason Coene" ,
	"'Tom Lane'" 
Cc: "'Merlin Moncure'" ,
	pgsql-performance@postgresql.org
Subject: Re: Hardware upgrade for a high-traffic database 
References: <200408120029.i7C0T30E002389@mail.gotfrag.com>
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Date: Thu, 12 Aug 2004 08:49:37 +0200
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On Wed, 11 Aug 2004 20:29:04 -0400, Jason Coene  wrote:




> gf=# EXPLAIN ANALYZE SELECT id FROM comments WHERE userid = 51 ORDER BY
> timestamp DESC LIMIT 5;
>                                                                   QUERY  
> PLAN
> ----------------------------------------------------------------------------
> -------------------------------------------------------------------
>  Limit  (cost=1608.43..1608.45 rows=5 width=8) (actual time=0.292..0.317
> rows=5 loops=1)
>    ->  Sort  (cost=1608.43..1609.45 rows=407 width=8) (actual
> time=0.287..0.295 rows=5 loops=1)
>          Sort Key: "timestamp"
>          ->  Index Scan using comments_ix_userid on comments
> (cost=0.00..1590.79 rows=407 width=8) (actual time=0.031..0.190 rows=35
> loops=1)
>                Index Cond: (userid = 51)
>  Total runtime: 0.375 ms
> (6 rows)

	Well, you have to read it from the bottom.
	- Index Scan using comments_ix_userid :
	It selects all records for your user.
	rows=407 : there are 407 rows.

	->  Sort  (cost=1608.43..1609.45 rows=407 width=8)
	It sorts them to find the 5 more recent.

	So basically you grab 407 rows to return only 5, so you do 80x more disk  
I/O than necessary. It is likely that posts from all users are interleaved  
in the table, so this probably translates directly into 407 page fetches.

	Note : EXPLAIN ANALYZE will only give good results the first time you run  
it. The second time, all data is in the cache, so it looks really faster  
than it is.

> gf=# EXPLAIN ANALYZE SELECT id FROM comments WHERE userid = 51 ORDER BY
> userid DESC, timestamp DESC LIMIT 5;
> QUERY PLAN
> ----
>  Limit  (cost=0.00..19.90 rows=5 width=12) (actual time=0.040..0.076  
> rows=5
> loops=1)
>    ->  Index Scan Backward using comments_ix_userid_timestamp on comments
> (cost=0.00..1620.25 rows=407 width=12) (actual time=0.035..0.054 rows=5
> loops=1)
>          Index Cond: (userid = 51)
>  Total runtime: 0.134 ms
> (4 rows)
>
> Note: This was done after adding an index on comments (userid, timestamp)

	Well, this one correctly uses the index, fetches 5 rows, and returns them.

	So, excluding index page hits, your unoptimized query has >400 page  
fetches, and your optimized one has 5 page fetches. Still wonder why it's  
faster ?

	Seq scan is fast when locality of reference is good. In your case, it's  
very bad.

From pgsql-performance-owner@postgresql.org  Thu Aug 12 07:38:09 2004
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Date: Thu, 12 Aug 2004 12:37:44 +0200
From: Ulrich Wisser 
Organization: Relevant Traffic AB
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Cc: bruno@wolff.to
Subject: Re: [GENERAL] How to know which queries are to be optimised?
References: <4110CFE7.9000202@relevanttraffic.se>
	<20040811162701.GA9992@wolff.to>
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Hi Bruno,

>>my web application grows slower and slower over time. After some 
>>profiling I came to the conclusion that my SQL queries are the biggest 
>>time spenders (25 seconds). Obviously I need to optimise my queries and 
>>maybe introduce some new indexes.
> 
> This sounds like you aren't doing proper maintainance. You need to be
> vacuuming with a large enough FSM setting.

I do a vacuum full analyze every night.
How can I see if my FSM setting is appropriate?

>>The problem is, that my application uses dynamic queries. I therefor can 
>>not determine what are the most common queries.
>>
>>I have used the postgresql logging ption before. Is there a tool to 
>>analyze the logfile for the most common and/or most time consuming queries?
> 
> 
> You can log queries that run for at least a specified amount of time.
> This will be useful in finding what the long running queries are.
> You can then use explain analyse to see why they are long running.

But is there a tool that could compile a summary out of the log? The log 
grows awefully big after a short time.

Thanks

/Ulrich






From pgsql-performance-owner@postgresql.org  Thu Aug 12 08:16:35 2004
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From: Richard Huxton 
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To: Ulrich Wisser 
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Subject: Re: [GENERAL] How to know which queries are to be optimised?
References: <4110CFE7.9000202@relevanttraffic.se>
	<20040811162701.GA9992@wolff.to>
	<411B4878.4090804@relevanttraffic.se>
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Ulrich Wisser wrote:
>> You can log queries that run for at least a specified amount of time.
>> This will be useful in finding what the long running queries are.
>> You can then use explain analyse to see why they are long running.
> 
> But is there a tool that could compile a summary out of the log? The log 
> grows awefully big after a short time.

You might want to look at the "Practical Query Analyser" - haven't used 
it myself yet, but it seems a sensible idea.

http://pqa.projects.postgresql.org/

-- 
   Richard Huxton
   Archonet Ltd

From pgsql-performance-owner@postgresql.org  Thu Aug 12 10:39:49 2004
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Subject: Re: Hardware upgrade for a high-traffic database 
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Thread-Topic: [PERFORM] Hardware upgrade for a high-traffic database 
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From: "Merlin Moncure" 
To: "Tom Lane" 
Cc: "Jason Coene" ,
	
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> This example looks fine, but since userid 51 evidently only has 35
> posts, there's not much time needed to read 'em all and sort 'em.  The
> place where the double-column index will win big is on userids with
> hundreds of posts.
>=20
> You have to keep in mind that each index costs time to maintain during
> inserts/updates.  So adding an index just because it makes a few
queries
> a little faster probably isn't a win.  You need to make tradeoffs.

IMNSHO, in Jason's case he needs to do everything possible to get his
frequently run queries going as quick as possible.  ISTM he can give up
a little on the update side, especially since he is running fsync=3Dfalse.
A .3-.5 sec query multiplied over 50-100 users running concurrently adds
up quick.  Ideally, you are looking up records based on a key that takes
you directly to the first record you want and is pointing to the next
number of records in ascending order.  I can't stress enough how
important this is so long as you can deal with the index/update
overhead.=20=20

I don't have a huge amount of experience with this in pg, but one of the
tricks we do in the ISAM world is a 'reverse date' system, so that you
can scan forwards on the key to pick up datetimes in descending order.
This is often a win because the o/s cache may assume read/forwards
giving you more cache hits.   There are a few different ways to do this,
but imagine:

create table t
(
    id int,
    ts  timestamp default now(),
    iv  interval  default ('01/01/2050'::timestamp - now())
);

create index t_idx on t(id, iv);
select * from t where id =3D k order by id, iv limit 5;

The above query should do a much better job pulling up data and should
be easier on your cache.  A further win might be to cluster the table on
this key if the table is really big.

note: interval is poor type to do this with, because it's a 12 byte type
(just used it here for demonstration purposes because it's easy).  With
a little trickery you can stuff it into a time type or an int4 type
(even better!).  If you want to be really clever you can do it without
adding any data to your table at all through functional indexes.

Since the planner can use the same index in the extraction and ordering,
you get some savings...not much, but worthwhile when applied over a lot
of users.  Knowing when and how to apply multiple key/functional indexes
will make you feel like you have 10 times the database you are using
right now.

Merlin

From pgsql-performance-owner@postgresql.org  Thu Aug 12 11:08:38 2004
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From: Christopher Kings-Lynne 
To: Ulrich Wisser 
Cc: pgsql-performance@postgresql.org, 
Subject: Re: [GENERAL] How to know which queries are to be optimised?
In-Reply-To: <411B4878.4090804@relevanttraffic.se>
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> I do a vacuum full analyze every night.
> How can I see if my FSM setting is appropriate?

On a busy website, run vacuum analyze once an hour, or even better, use
contrib/pg_autovacuum

Chris



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> But is there a tool that could compile a summary out of the log? The log
> grows awefully big after a short time.

Actually, yes there is.  Check out www.pgfoundry.org.  I think it's called
pqa or postgres query analyzer or somethign.

Chris


From pgsql-performance-owner@postgresql.org  Thu Aug 12 15:10:38 2004
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	"Tom Lane" 
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> I don't have a huge amount of experience with this in pg, but one of
the
> tricks we do in the ISAM world is a 'reverse date' system, so that you
> can scan forwards on the key to pick up datetimes in descending order.
> This is often a win because the o/s cache may assume read/forwards
> giving you more cache hits.   There are a few different ways to do
this,
> but imagine:

I've been thinking more about this and there is even a more optimal way
of doing this if you are willing to beat on your data a bit.  It
involves the use of sequences.  Lets revisit your id/timestamp query
combination for a message board.  The assumption is you are using
integer keys for all tables.  You probably have something like:

create table messages
(
    user_id 	int4 references users,
    topic_id      int4 references topics,
    message_id    serial,
    message_time  timestamp default now(),
    [...]
);

The following suggestion works in two principles: one is that instead of
using timestamps for ordering, integers are quicker, and sequences have
a built in ability for reverse-ordering.

Lets define:
create sequence message_seq increment -1 start 2147483647 minvalue 0
maxvalue 2147483647;

now we define our table:
create table messages
(
    user_id      int4 references users,
    topic_id     int4 references topics,
    message_id   int4 default nextval('message_seq') primary key,
    message_time timestamp default now(),
    [...]
);

create index user_message_idx on messages(user_id, message_id);
-- optional
cluster user_message_idx messages;

Since the sequence is in descending order, we don't have to do any
tricks to logically reverse order the table.

-- return last k posts made by user u in descending order;

select * from messages where user_id =3D u order by user_id, message_id
limit k;

-- return last k posts on a topic
create index topic_message_idx on messages(topic_id, user_id);
select * from messages where topic_id =3D t order by topic_id, message_id

a side benefit of clustering is that there is little penalty for
increasing k because of read ahead optimization whereas in normal
scenarios your read time scales with k (forcing small values for k).  If
we tended to pull up messages by topic more frequently than user, we
would cluster on topic_message_idx instead.  (if we couldn't decide, we
might cluster on message_id or not at all).

The crucial point is that we are making this one index run really fast
at the expense of other operations.  The other major point is we can use
a sequence in place of a timestamp for ordering.  Using int4 vs.
timestamp is a minor efficiency win, if you are worried about > 4B rows,
then stick with timestamp.

This all boils down to a central unifying principle: organize your
indices around your expected access patterns to the data.  Sorry if I'm
bleating on and on about this...I just think there is plenty of
optimization room left in there :)

Merlin


From pgsql-performance-owner@postgresql.org  Thu Aug 12 14:50:54 2004
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To: "Merlin Moncure" 
Cc: pgsql-performance@postgresql.org,
	"Jason Coene" 
Subject: Re: Hardware upgrade for a high-traffic database 
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Comments: In-reply-to "Merlin Moncure" 
	message dated "Thu, 12 Aug 2004 12:58:10 -0400"
Date: Thu, 12 Aug 2004 13:09:02 -0400
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"Merlin Moncure"  writes:
> The following suggestion works in two principles: one is that instead of
> using timestamps for ordering, integers are quicker,

The difference would be pretty marginal --- especially if you choose to
use bigints instead of ints.  (A timestamp is just a float8 or bigint
under the hood, and is no more expensive to compare than those datatypes.
Timestamps *are* expensive to convert for I/O, but comparison does not
have to do that.)  I wouldn't recommend kluging up your data schema just
for that.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Thu Aug 12 16:33:23 2004
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Tom Lane wrote:
> The difference would be pretty marginal --- especially if you choose
to
> use bigints instead of ints.  (A timestamp is just a float8 or bigint
> under the hood, and is no more expensive to compare than those
datatypes.
> Timestamps *are* expensive to convert for I/O, but comparison does not
> have to do that.)  I wouldn't recommend kluging up your data schema
just
> for that.

Right (int4 use was assumed).  I agree, but it's kind of a 'two birds
with one stone' kind of thing, because it's easier to work with reverse
ordering integers than time values.  So I claim a measurable win (the
real gainer of course being able to select and sort on the same key,
which works on any type), based on the int4-int8 difference, which is a
33% reduction in key size.

One claim I don't have the data for is that read-forward is better than
read-back, but my gut tells me he'll get a better cache hit ratio that
way.  This will be very difficult to measure.

As for kludging, using a decrementing sequence is not a bad idea if the
general tendency is to read the table backwards, even if just for
conceptual reasons.  The main kludge is the int4 assumption, which (IMO)
isn't so bad.  He would just have to rebuild the existing p-key in
reverse order (10$ says his keys are all already int4s), and hopefully
not mess with the application code too much.

At least, it's what I would try if I was in his shoes :)

YMMV
Merlin







From pgsql-general-owner@postgresql.org  Thu Aug 12 16:28:38 2004
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Date: Thu, 12 Aug 2004 13:02:48 -0500
From: Laura Vance 
Reply-To: vancel@winfreeacademy.com
Organization: WACS
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Subject: Re: My admin left the job and I am stuck
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All of the resources you need are at http://www.posgresql.org/

But, a quick note on how to connect to the database, you don't need to 
really know where it's installed, just that it's running and accepting 
connections.  Under Linux "netstat -tapn" will show you all of the open 
TCP ports and what's listening to each.  For Postgres, the default port 
is 5432 and the process is called postmaster.  You may need to be logged 
in as root to see this.

First thing is that knowing SQL basics is pretty much required before 
you can really investigate what he had set up.
Second thing is to connect by using the following command:  psql
Without any arguments, it will connect to the local machine and to a 
database named for the current user.  Once in psql, type \d to see a 
list of the user-defined tables.  To see a list of databases type \l and 
you will be shown a list of databases.

 From there, you can explore until your heart's content.

Everything is SQL compliant, so if you know SQL, you shouldn't have any 
problems.

As for Linux admin, the most important thing to remember is that 
everything is case sensitive.  ls != LS

If you're coming from the MS world, take some time to really learn 
Linux... I'm sure you'll like it and eventually you'll prefer it.  I use 
Linux as my only OS at home, and I finally have a job where I use Linux 
at work (they adopted it after I submitted a proposal).

hope this helps!
Laura

Karam Chand wrote:

>Hello,
>
>My linux admin left the job. We had a PostgreSQL
>installed under his username. He used to maintain it.
>Now I am looking at the Linux box and I am just a
>super duper newbie in Linux administration.
>
>The previosu admin had a database created under his
>name coz PostgreSQL dosnt allow root database.
>
>Now I want to get the data back and use it? I dont
>mind if I have to use a different DB?
>
>I dont even know where he isntalled the PostgreSQL
>binaries and data?
>
>Where can I all this information?
>
>I am feeling really stupid but thank GOD we dont have
>any live databases running?
>
>Regards,
>Karam
>  
>
-- 
Thanks,
Laura Vance
Systems Engineer
Winfree Academy Charter Schools
6221 Riverside Dr. Ste 110
Irving, Tx  75039
Web: www.winfreeacademy.com



From pgsql-performance-owner@postgresql.org  Thu Aug 12 15:58:46 2004
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From: "gnari" 
To: 
References: <6EE64EF3AB31D5448D0007DD34EEB3412A7450@Herge.rcsinc.local>
Subject: Re: Hardware upgrade for a high-traffic database 
Date: Thu, 12 Aug 2004 18:59:28 -0000
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"Merlin Moncure"  wrote:

-- optional
cluster user_message_idx messages;

would one not have to repeat this operation regularly, to keep
any advantage of this ? my impression was that this is a relatively
heavy operation on a large table.

gnari




From pgsql-performance-owner@postgresql.org  Thu Aug 12 17:03:37 2004
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> would one not have to repeat this operation regularly, to keep
> any advantage of this ? my impression was that this is a relatively
> heavy operation on a large table.

Yeah, it requires an exclusive lock and a table rebuild.  It might be
useful to a message board type database since (one presumes) the reads
would be concentrated over recently created data, entered after the
cluster and losing any benefit.

As far as table size, bigger tables are a larger operation but take
longer to get all out of whack.  Question is: what percentage of the
data turns over between maintenance periods?   Plus, there has to be a
maintenance period...nobody does anything while the table is clustering.

Also, a particular method of reading the table has to really dominate as
far as user usage pattern.  So, it's pretty rare to user cluster, but it
can help in some cases.

Merlin

From pgsql-benchmarks-owner@postgresql.org  Fri Aug 13 12:04:35 2004
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Hi All,

We are having a performance problem with our database. The problem
exists when we include a constraint in GCTBALLOT. The constraint is as
follows:

alter table GCTBALLOT
   add constraint FK_GCTBALLOT_GCTWEBU foreign key (GCTWEBU_SRL)
      references GCTWEBU (SRL)
      on delete restrict on update restrict;

The two tables that we insert into are the following:

GCTBALLOT:

                                          Table "cbcca.gctballot"

      Column      |            Type             |                      
  Modifiers
------------------+-----------------------------+-----------------------------------------------------------
 srl              | integer                     | not null default
nextval('cbcca.gctballot_srl_seq'::text)
 gctbwindow_srl   | numeric(12,0)               | not null
 gctcandidate_srl | numeric(12,0)               | not null
 gctwebu_srl      | numeric(12,0)               |
 gctphoneu_srl    | numeric(12,0)               |
 ballot_time      | timestamp without time zone | not null
 ip_addr          | character varying(15)       |
Indexes:
    "pk_gctballot" primary key, btree (srl)
    "i1_gctballot_webusrl" btree (gctwebu_srl)
Foreign-key constraints:
    "fk_gctbwindow_gctballot" FOREIGN KEY (gctbwindow_srl) REFERENCES
gctbwindow(srl) ON UPDATE RESTRICT ON DELETE RESTRICT
    "fk_gctcandidate_gctballot" FOREIGN KEY (gctcandidate_srl)
REFERENCES gctcandidate(srl) ON UPDATE RESTRICT ON DELETE RESTRICT
    "fk_gctphoneu_gctballot" FOREIGN KEY (gctphoneu_srl) REFERENCES
gctphoneu(srl) ON UPDATE RESTRICT ON DELETE RESTRICT

with the extra constraint:

"fk_gctballot_gctwebu" FOREIGN KEY (gctwebu_srl) REFERENCES
gctwebu(srl) ON UPDATE RESTRICT ON DELETE RESTRICT



GCTWEBU:

                                          Table "cbcca.gctwebu"
     Column      |            Type             |                       
Modifiers
-----------------+-----------------------------+---------------------------------------------------------
 srl             | integer                     | not null default
nextval('cbcca.gctwebu_srl_seq'::text)
 gctlocation_srl | numeric(12,0)               | not null
 gctagerange_srl | numeric(12,0)               | not null
 email           | character varying(255)      | not null
 uhash           | character varying(255)      | not null
 sex             | character varying(1)        | not null
 created_time    | timestamp without time zone | not null
Indexes:
    "pk_gctwebu" primary key, btree (srl)
    "i1_gctwebu_email" unique, btree (email)
Foreign-key constraints:
    "fk_gctagerang_gctwebu" FOREIGN KEY (gctagerange_srl) REFERENCES
gctagerange(srl) ON UPDATE RESTRICT ON DELETE RESTRICT
    "fk_gctwebu_gctlocation" FOREIGN KEY (gctlocation_srl) REFERENCES
gctlocation(srl) ON UPDATE RESTRICT ON DELETE RESTRICT


To begin, GCTBALLOT has 6122546 rows and GCTWEBU has 231444 rows.

Now when we try and insert 100 entries into GCTBALLOT with the extra
constraint it 
takes: 37981 milliseconds

Also, when we try and insert 100 entries into GCTBALLOT with the extra
constraint, 
but insert 'null' into the column gctwebu_srl it takes: 286
milliseconds

However when we try and insert 100 entries into GCTBALLOT without the
extra constraint (no foreign key between GCTBALLOT & GCTWEBU)
it takes: 471 milliseconds


In summary, inserting into GCTBALLOT without the constraint or
inserting null for 
gctwebu_srl in GCTBALLOT gives us good performance.  However, inserting
into GCTBALLOT
with the constraint and valid gctwebu_srl values gives us poor
performance.

Also, the insert we use is as follows:

INSERT INTO GCTBALLOT  (gctbwindow_srl, gctcandidate_srl, gctwebu_srl,
gctphoneu_srl, 
ballot_time, ip_addr) VALUES (CBCCA.gcf_getlocation(?), ?,
CBCCA.gcf_validvoter(?,?), 
null, ?, ?);

NOTE: "gcf_validvoter" find 'gctweb_srl' value

"
CREATE OR REPLACE FUNCTION gcf_validvoter (VARCHAR, VARCHAR) 
          RETURNS NUMERIC AS '
DECLARE
  arg1       ALIAS FOR $1;
  arg2       ALIAS FOR $2;
  return_val NUMERIC;
BEGIN
  SELECT SRL INTO return_val
  FROM   gctwebu
  WHERE  EMAIL = arg1
  AND    UHASH = arg2;

  RETURN return_val;
END;
' LANGUAGE plpgsql;
"


Where the question marks are filled in with values in our java code.

We are puzzled as to why there is this difference in performance when
inserting b/c we 
believe that we have indexed all columns used by this constraint. And
we realize that 
inserting 'null' into GCTBALLOT doesn't use this constraint b/c no look
up is necessary.
So this causes good performance.  Why is it that when we use this
constraint that
the performance is effected so much?

Any help would be much appreciated.
Thanks


P.S. Even we added an index on 'gctwebu_srl' column and did 
1- "Analyzed ALL TABLES"
2- "analyze GCTBALLOT(gctwebu_srl);"

but still have the same problem!


From pgsql-performance-owner@postgresql.org  Thu Aug 12 19:41:49 2004
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From: William Yu 
X-Newsgroups: comp.databases.postgresql.performance
Subject: Re: Help specifying new machine
Date: Thu, 12 Aug 2004 15:12:43 -0700
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Rory Campbell-Lange wrote:

> The present server is a 2GHz Pentium 4/512 KB cache with 2
> software-raided ide disks (Maxtors) and 1GB of RAM.
> 
> 
> I have been offered the following 1U server which I can just about
> afford:
> 
> 1U server
> Intel Xeon 2.8GHz 512K cache                      1
> 512MB PC2100 DDR ECC Registered                   2
> 80Gb SATA HDD                                     4
> 4 port SATA card, 3 ware 8506-4                   1
> 3 year next-day hardware warranty                 1

You're not getting much of a bump with this server. The CPU is 
incrementally faster -- in the absolutely best case scenario where your 
queries are 100% cpu-bound, that's about ~25%-30% faster.

If you could use that money instead to upgrade your current server, 
you'd get a much bigger impact. Go for more memory and scsi (raid 
controllers w/ battery-backed cache).

From pgsql-performance-owner@postgresql.org  Thu Aug 12 19:52:52 2004
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Message-ID: <411BF429.1090106@wildcash.com>
Date: Fri, 13 Aug 2004 08:50:17 +1000
From: Rudi Starcevic 
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Subject: Re: [GENERAL] How to know which queries are to be optimised?
References: <4110CFE7.9000202@relevanttraffic.se>
	<20040811162701.GA9992@wolff.to>
	<411B4878.4090804@relevanttraffic.se>
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Hi,

>> But is there a tool that could compile a summary out of the log? The 
>> log grows awefully big after a short time.

There's also pg_analyzer to check out.

http://www.samse.fr/GPL/pg_analyzer/

Some of it's features are: written in Perl and produces HTML output.

> You might want to look at the "Practical Query Analyser" - haven't used 
> it myself yet, but it seems a sensible idea.
> 
> http://pqa.projects.postgresql.org/


Cheers,
Rudi.

From pgsql-performance-owner@postgresql.org  Fri Aug 13 12:08:47 2004
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From: Raoul Buzziol 
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William Yu wrote:

> Rory Campbell-Lange wrote:
> 
>> The present server is a 2GHz Pentium 4/512 KB cache with 2
>> software-raided ide disks (Maxtors) and 1GB of RAM.
>> 
>> 
>> I have been offered the following 1U server which I can just about
>> afford:
>> 
>> 1U server
>> Intel Xeon 2.8GHz 512K cache                      1
>> 512MB PC2100 DDR ECC Registered                   2
>> 80Gb SATA HDD                                     4
>> 4 port SATA card, 3 ware 8506-4                   1
>> 3 year next-day hardware warranty                 1
> 
> You're not getting much of a bump with this server. The CPU is
> incrementally faster -- in the absolutely best case scenario where your
> queries are 100% cpu-bound, that's about ~25%-30% faster.

What about using Dual Athlon MP instead of a Xeon? Would be much less expensive,
but have higher performance (I think).

> 
> If you could use that money instead to upgrade your current server,
> you'd get a much bigger impact. Go for more memory and scsi (raid
> controllers w/ battery-backed cache).


From pgsql-performance-owner@postgresql.org  Fri Aug 13 04:47:30 2004
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Date: Fri, 13 Aug 2004 09:47:17 +0200
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Hi,

is there anything I can doo to speed up inserts? One of my tables gets 
about 100 new rows every five minutes. And somehow the inserts tend to 
take more and more time.

Any suggestions welcome.

TIA

Ulrich


From pgsql-performance-owner@postgresql.org  Fri Aug 13 07:09:17 2004
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From: G u i d o B a r o s i o 
To: ulrich.wisser@relevanttraffic.se,
	pgsql-performance@postgresql.org
Subject: Re: insert
Reply-To: gbarosio@uolsinectis.com.ar
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Tips!
*Delete indexes and recreate them after the insert.
*Disable auto-commit
*Perform a copy will be faster, sure.

Best wishes,
Guido

> Hi,
> 
> is there anything I can doo to speed up inserts? One of my tables gets 
> about 100 new rows every five minutes. And somehow the inserts tend to 
> take more and more time.
> 
> Any suggestions welcome.
> 
> TIA
> 
> Ulrich
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match


From pgsql-performance-owner@postgresql.org  Fri Aug 13 07:47:35 2004
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From: "gnari" 
To: 
References: <20040813100800.24FC86C37F@honorio.sinectis.com.ar>
Subject: Re: insert
Date: Fri, 13 Aug 2004 10:49:05 -0000
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"G u i d o B a r o s i o"  wrote:

[speeding up 100 inserts every 5 minutes]

> Tips!
> *Delete indexes and recreate them after the insert.

sounds a bit extreme, for only 100 inserts
 
gnari





From pgsql-performance-owner@postgresql.org  Fri Aug 13 08:16:54 2004
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From: G u i d o B a r o s i o 
To: gnari@simnet.is, pgsql-performance@postgresql.org
Subject: Re: insert
Reply-To: gbarosio@uolsinectis.com.ar
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As I see it's 100 inserts every 5 minutes, not only 100 inserts.

Sure it's extreme for only 100 inserts.

Cheers,
Guido

> "G u i d o B a r o s i o"  wrote:
> 
> [speeding up 100 inserts every 5 minutes]
> 
> > Tips!
> > *Delete indexes and recreate them after the insert.
> 
> sounds a bit extreme, for only 100 inserts
>  
> gnari
> 
> 
> 
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match


From pgsql-performance-owner@postgresql.org  Fri Aug 13 08:45:27 2004
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From: "G u i d o B a r o s i o" :


> As I see it's 100 inserts every 5 minutes, not only 100 inserts.
>
> Sure it's extreme for only 100 inserts.

I am sorry, I do not quite grasp what you are saying.
my understanding was that there are constantly new inserts,
coming in bursts of 100 , every 5 minutes.
I imagined that the indexes were needed in between.

if this is the case, the bunches of 100 inserts should
be done inside a transaction (or by 1 COPY statement)

if, on the other hand, the inserts happen independently,
at a rate of 100 inserts / 5 minutes, then this will not help

gnari



>
> Cheers,
> Guido
>
> > "G u i d o B a r o s i o"  wrote:
> >
> > [speeding up 100 inserts every 5 minutes]
> >
> > > Tips!
> > > *Delete indexes and recreate them after the insert.
> >
> > sounds a bit extreme, for only 100 inserts
> >
> > gnari
> >
> >
> >
> >
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 9: the planner will ignore your desire to choose an index scan if
your
> >       joining column's datatypes do not match
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 7: don't forget to increase your free space map settings
>


From pgsql-performance-owner@postgresql.org  Fri Aug 13 09:10:26 2004
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From: Ulrich Wisser 
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To: gnari 
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Subject: Re: insert
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	<00cc01c4812b$4e7f02e0$0100000a@wp2000>
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Hi,

my inserts are done in one transaction, but due to some foreign key 
constraints and five indexes sometimes the 100 inserts will take more 
than 5 minutes.

/Ulrich


From pgsql-performance-owner@postgresql.org  Fri Aug 13 09:41:26 2004
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Date: Fri, 13 Aug 2004 13:41:15 +0100
From: Paul Thomas 
To: Ulrich Wisser 
Cc: "pgsql-performance @ postgresql . org" ,
	pgsql-performance@postgresql.org
Subject: Re: insert
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On 13/08/2004 13:10 Ulrich Wisser wrote:
> Hi,
> 
> my inserts are done in one transaction, but due to some foreign key 
> constraints and five indexes sometimes the 100 inserts will take more 
> than 5 minutes.

Two possibilities come to mind:

a) you need an index on the referenced FK field
b) you have an index but a type mis-match (e.g, an int4 field referencing 
an int8 field)

Either of these will cause a sequential table scan and poor performance.

-- 
Paul Thomas
+------------------------------+---------------------------------------------+
| Thomas Micro Systems Limited | Software Solutions for 
Business             |
| Computer Consultants         | 
http://www.thomas-micro-systems-ltd.co.uk   |
+------------------------------+---------------------------------------------+

From pgsql-performance-owner@postgresql.org  Fri Aug 13 09:58:34 2004
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Subject: Re: insert
From: Rod Taylor 
To: Ulrich Wisser 
Cc: gnari ,
	Postgresql Performance 
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On Fri, 2004-08-13 at 08:10, Ulrich Wisser wrote:
> Hi,
> 
> my inserts are done in one transaction, but due to some foreign key 
> constraints and five indexes sometimes the 100 inserts will take more 
> than 5 minutes.

It is likely that you are missing an index on one of those foreign key'd
items.

Do an EXPLAIN ANALYZE SELECT * FROM foreign_table WHERE foreign_col =
'';

Fix them until they're quick.



From pgsql-performance-owner@postgresql.org  Fri Aug 13 11:44:18 2004
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Date: Fri, 13 Aug 2004 10:43:43 -0400
From: "Arash Zaryoun" 
To: 
Subject: Weird Database Performance problem!
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Hi,

We are having a performance problem with our database. The problem
exists when we include a constraint in GCTBALLOT. The constraint is as
follows:

alter table GCTBALLOT
   add constraint FK_GCTBALLOT_GCTWEBU foreign key (GCTWEBU_SRL)
      references GCTWEBU (SRL)
      on delete restrict on update restrict;

The two tables that we insert into are the following:

GCTBALLOT:

                                          Table "cbcca.gctballot"

      Column      |            Type             |                      
  Modifiers
------------------+-----------------------------+-----------------------------------------------------------
 srl              | integer                     | not null default
nextval('cbcca.gctballot_srl_seq'::text)
 gctbwindow_srl   | numeric(12,0)               | not null
 gctcandidate_srl | numeric(12,0)               | not null
 gctwebu_srl      | numeric(12,0)               |
 gctphoneu_srl    | numeric(12,0)               |
 ballot_time      | timestamp without time zone | not null
 ip_addr          | character varying(15)       |
Indexes:
    "pk_gctballot" primary key, btree (srl)
    "i1_gctballot_webusrl" btree (gctwebu_srl)
Foreign-key constraints:
    "fk_gctbwindow_gctballot" FOREIGN KEY (gctbwindow_srl) REFERENCES
gctbwindow(srl) ON UPDATE RESTRICT ON DELETE RESTRICT
    "fk_gctcandidate_gctballot" FOREIGN KEY (gctcandidate_srl)
REFERENCES gctcandidate(srl) ON UPDATE RESTRICT ON DELETE RESTRICT
    "fk_gctphoneu_gctballot" FOREIGN KEY (gctphoneu_srl) REFERENCES
gctphoneu(srl) ON UPDATE RESTRICT ON DELETE RESTRICT

with the extra constraint:

"fk_gctballot_gctwebu" FOREIGN KEY (gctwebu_srl) REFERENCES
gctwebu(srl) ON UPDATE RESTRICT ON DELETE RESTRICT



GCTWEBU:

                                          Table "cbcca.gctwebu"
     Column      |            Type             |                       
Modifiers
-----------------+-----------------------------+---------------------------------------------------------
 srl             | integer                     | not null default
nextval('cbcca.gctwebu_srl_seq'::text)
 gctlocation_srl | numeric(12,0)               | not null
 gctagerange_srl | numeric(12,0)               | not null
 email           | character varying(255)      | not null
 uhash           | character varying(255)      | not null
 sex             | character varying(1)        | not null
 created_time    | timestamp without time zone | not null
Indexes:
    "pk_gctwebu" primary key, btree (srl)
    "i1_gctwebu_email" unique, btree (email)
Foreign-key constraints:
    "fk_gctagerang_gctwebu" FOREIGN KEY (gctagerange_srl) REFERENCES
gctagerange(srl) ON UPDATE RESTRICT ON DELETE RESTRICT
    "fk_gctwebu_gctlocation" FOREIGN KEY (gctlocation_srl) REFERENCES
gctlocation(srl) ON UPDATE RESTRICT ON DELETE RESTRICT


To begin, GCTBALLOT has 6122546 rows and GCTWEBU has 231444 rows.

Now when we try and insert 100 entries into GCTBALLOT with the extra
constraint it 
takes: 37981 milliseconds

Also, when we try and insert 100 entries into GCTBALLOT with the extra
constraint, 
but insert 'null' into the column gctwebu_srl it takes: 286
milliseconds

However when we try and insert 100 entries into GCTBALLOT without the
extra constraint (no foreign key between GCTBALLOT & GCTWEBU)
it takes: 471 milliseconds


In summary, inserting into GCTBALLOT without the constraint or
inserting null for 
gctwebu_srl in GCTBALLOT gives us good performance.  However, inserting
into GCTBALLOT
with the constraint and valid gctwebu_srl values gives us poor
performance.

Also, the insert we use is as follows:

INSERT INTO GCTBALLOT  (gctbwindow_srl, gctcandidate_srl, gctwebu_srl,
gctphoneu_srl, 
ballot_time, ip_addr) VALUES (CBCCA.gcf_getlocation(?), ?,
CBCCA.gcf_validvoter(?,?), 
null, ?, ?);

NOTE: "gcf_validvoter" find 'gctweb_srl' value

"
CREATE OR REPLACE FUNCTION gcf_validvoter (VARCHAR, VARCHAR) 
          RETURNS NUMERIC AS '
DECLARE
  arg1       ALIAS FOR $1;
  arg2       ALIAS FOR $2;
  return_val NUMERIC;
BEGIN
  SELECT SRL INTO return_val
  FROM   gctwebu
  WHERE  EMAIL = arg1
  AND    UHASH = arg2;

  RETURN return_val;
END;
' LANGUAGE plpgsql;
"


Where the question marks are filled in with values in our java code.

We are puzzled as to why there is this difference in performance when
inserting b/c we 
believe that we have indexed all columns used by this constraint. And
we realize that 
inserting 'null' into GCTBALLOT doesn't use this constraint b/c no look
up is necessary.
So this causes good performance.  Why is it that when we use this
constraint that
the performance is effected so much?


Thanks


P.S. Even we added an index on 'gctwebu_srl' column and did 
1- "Analyzed ALL TABLES"
2- "analyze GCTBALLOT(gctwebu_srl);"

but still have the same problem!


From pgsql-performance-owner@postgresql.org  Fri Aug 13 11:54:29 2004
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From: Bruno Wolff III 
To: Rod Taylor 
Cc: Ulrich Wisser , gnari ,
	Postgresql Performance 
Subject: Re: insert
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On Fri, Aug 13, 2004 at 08:57:56 -0400,
  Rod Taylor  wrote:
> On Fri, 2004-08-13 at 08:10, Ulrich Wisser wrote:
> > Hi,
> > 
> > my inserts are done in one transaction, but due to some foreign key 
> > constraints and five indexes sometimes the 100 inserts will take more 
> > than 5 minutes.
> 
> It is likely that you are missing an index on one of those foreign key'd
> items.

I don't think that is too likely as a foreign key reference must be a
unique key which would have an index. I think the type mismatch
suggestion is probably what the problem is.
The current solution is to make the types match. In 8.0.0 it would probably
work efficiently as is, though it isn't normal for foreign keys to have a type
mismatch and he may want to change that anyway.

From pgsql-performance-owner@postgresql.org  Fri Aug 13 13:00:49 2004
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From: Richard Huxton 
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To: Arash Zaryoun 
Cc: pgsql-performance@postgresql.org
Subject: Re: Weird Database Performance problem!
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Arash Zaryoun wrote:
> Hi,
> 
> We are having a performance problem with our database. The problem
> exists when we include a constraint in GCTBALLOT. The constraint is as
> follows:
> 
> alter table GCTBALLOT
>    add constraint FK_GCTBALLOT_GCTWEBU foreign key (GCTWEBU_SRL)
>       references GCTWEBU (SRL)
>       on delete restrict on update restrict;
> 
> The two tables that we insert into are the following:

> GCTBALLOT:
>  gctwebu_srl      | numeric(12,0)               |

> GCTWEBU:
>  srl             | integer                     | not null default

Your types don't match. You have a numeric referencing an integer. PG 
probably isn't using the index (it's smarter about this in 8.0 iirc).

HTH
-- 
   Richard Huxton
   Archonet Ltd

From pgsql-performance-owner@postgresql.org  Fri Aug 13 15:10:17 2004
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>> What caught my attention initially was the 300+/sec insert performance.
>> On 8.0/NTFS/fsync=on, I can't break 100/sec on a 10k rpm ATA disk.  My
>> hardware seems to be more or less in the same league as psql's, so I was
>> naturally curious if this was a NT/Unix issue, a 7.4/8.0 issue, or a
>> combination of both.

	There is also the fact that NTFS is a very slow filesystem, and Linux is  
a lot better than Windows for everything disk, caching and IO related. Try  
to copy some files in NTFS and in ReiserFS...

From pgsql-performance-owner@postgresql.org  Fri Aug 13 14:43:06 2004
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To: pgsql-performance@postgresql.org
Subject: Reiser4
References:  <411CDC24.4090706@archonet.com>
From: =?iso-8859-15?Q?Pierre-Fr=E9d=E9ric_Caillaud?=
	
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	ReiserFS 4 is (will be) a filesystem that implements transactions.

	Are there any plans in a future Postgresql version to support a special  
fsync method for Reiser4 which will use the filesystem's transaction  
engine, instead of an old kludge like fsync(), with a possibility of  
vastly enhanced performance ?

	Is there also a possibility to tell Postgres : "I don't care if I lose 30  
seconds of transactions on this table if the power goes out, I just want  
to be sure it's still ACID et al. compliant but you can fsync less often  
and thus be faster" (with a possibility of setting that on a per-table  
basis) ?

	Thanks.

From pgsql-performance-owner@postgresql.org  Fri Aug 13 14:14:24 2004
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Reply-To: 
From: "Matt Clark" 
To: "'Bruno Wolff III'" , "'Rod Taylor'" 
Cc: "'Ulrich Wisser'" ,
	"'gnari'" ,
	"'Postgresql Performance'" 
Subject: Re: insert
Date: Fri, 13 Aug 2004 17:17:10 +0100
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> > It is likely that you are missing an index on one of those foreign 
> > key'd items.
> 
> I don't think that is too likely as a foreign key reference 
> must be a unique key which would have an index. 

I think you must be thinking of primary keys, not foreign keys.  All
one-to-many relationships have non-unique foreign keys.


From pgsql-performance-owner@postgresql.org  Fri Aug 13 13:23:34 2004
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From: Bruno Wolff III 
To: Matt Clark 
Cc: 'Rod Taylor' ,
	'Ulrich Wisser' ,
	'gnari' ,
	'Postgresql Performance' 
Subject: Re: insert
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On Fri, Aug 13, 2004 at 17:17:10 +0100,
  Matt Clark  wrote:
> > > It is likely that you are missing an index on one of those foreign 
> > > key'd items.
> > 
> > I don't think that is too likely as a foreign key reference 
> > must be a unique key which would have an index. 
> 
> I think you must be thinking of primary keys, not foreign keys.  All
> one-to-many relationships have non-unique foreign keys.

The target of the reference needs to have at least a unique index.
I am not sure if it needs to actually be declared as either a unique
or primary key, though that is the intention.

The records doing the referencing don't need (and normally aren't)
unique.

From pgsql-benchmarks-owner@postgresql.org  Sat Aug 14 17:05:59 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: "Arash Zaryoun" , ,
	, 
Subject: Re: [PERFORM] Performance Problem With Postgresql!
Date: Fri, 13 Aug 2004 10:19:15 -0700
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Arash,

> We are having a performance problem with our database. The problem
> exists when we include a constraint in GCTBALLOT. The constraint is as
> follows:

You posted twice, to three different mailing lists each time.  This is 
discourteous.   Please do not do so again, as people may not help you if they 
feel you are being rude.

Richard H has posted the solution to your problem.

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Fri Aug 13 15:46:27 2004
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To: =?iso-8859-15?q?Pierre-Fr=E9d=E9ric=20Caillaud?=
	, pgsql-performance@postgresql.org
Subject: Re: Reiser4
Date: Fri, 13 Aug 2004 11:01:52 -0700
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Pierre,

> 	Are there any plans in a future Postgresql version to support a special  
> fsync method for Reiser4 which will use the filesystem's transaction  
> engine, instead of an old kludge like fsync(), with a possibility of  
> vastly enhanced performance ?

I don't know of any such in progress right now.  Why don't you start it?  It 
would have to be an add-in since we support 28 operating systems and Reiser 
is AFAIK Linux-only, but it sounds like an interesting experiment.

> 	Is there also a possibility to tell Postgres : "I don't care if I lose 30  
> seconds of transactions on this table if the power goes out, I just want  
> to be sure it's still ACID et al. compliant but you can fsync less often  
> and thus be faster" (with a possibility of setting that on a per-table  
> basis) ?

Not per-table, no, but otherwise take a look at the Background Writer feature 
of 8.0.

-- 
-Josh Berkus
 "A developer of Very Little Brain"
 Aglio Database Solutions
 San Francisco


From pgsql-performance-owner@postgresql.org  Fri Aug 13 15:44:22 2004
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To: Bruno Wolff III 
Cc: Rod Taylor , Ulrich Wisser ,
	gnari ,
	Postgresql Performance 
Subject: Re: insert 
In-reply-to: <20040813150243.GA2004@wolff.to> 
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	message dated "Fri, 13 Aug 2004 10:02:43 -0500"
Date: Fri, 13 Aug 2004 14:01:59 -0400
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From: Tom Lane 
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Bruno Wolff III  writes:
>   Rod Taylor  wrote:
>> It is likely that you are missing an index on one of those foreign key'd
>> items.

> I don't think that is too likely as a foreign key reference must be a
> unique key which would have an index. I think the type mismatch
> suggestion is probably what the problem is.

I agree.  It is possible to have a lack-of-index problem on the
referencing column (as opposed to the referenced column), but that
normally only hurts you for deletes from the referenced table.

> The current solution is to make the types match. In 8.0.0 it would probably
> work efficiently as is, though it isn't normal for foreign keys to have a type
> mismatch and he may want to change that anyway.

8.0 will not fix this particular issue, as I did not add any numeric-vs-int
comparison operators.  If we see a lot of complaints we could think
about adding such, but for 8.0 only the more common cases such as
int-vs-bigint are covered.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Fri Aug 13 18:05:15 2004
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Arash Zaryoun wrote:
> Hi Richard,
> 
> Thanks for your prompt reply. It fixed the problem. 
> Just one more question: Do I need to create an index for FKs? 

You don't _need_ to, but on the referring side (e.g. table GCTBALLOT in 
your example) PostgreSQL won't create one automatically.

Of course, the primary-key side will already have an index being used as 
part of the constraint.

I've cc:ed the list on this, the question pops up quite commonly.

-- 
   Richard Huxton
   Archonet Ltd

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> 	There is also the fact that NTFS is a very slow filesystem, and
> Linux is
> a lot better than Windows for everything disk, caching and IO related. Try
> to copy some files in NTFS and in ReiserFS...

I'm not so sure I would agree with such a blanket generalization.  I find N=
TFS to be very fast, my main complaint is fragmentation issues...I bet NTFS=
 is better than ext3 at most things (I do agree with you about the cache, t=
houghO.

I think in very general sense the open source stuff is higher quality but M=
icrosoft benefits from a very tight vertical integration of the system.  Th=
ey added ReadFileScatter and WriteFileScatter to the win32 api specifically=
 to make SQL Server run faster and SQL server is indeed very, very good at =
i/o.

SQL Server keeps a one file database with blocks collected and written asyn=
chronously.  It's a very tight system because they have control over every =
layer of the system.

Know your enemy.

That said, I think transaction based file I/O is 'the way' and if implement=
ed on Reiser4 faster than I/O methodology than offered on windows/ntfs.=20=
=20

Merlin

From pgsql-performance-owner@postgresql.org  Fri Aug 13 18:58:37 2004
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From: "borajetta" 
To: 
Subject: REINDEX needed because of index corruption need help ASAP
Date: Fri, 13 Aug 2004 14:40:26 -0700
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------=_NextPart_000_0034_01C48143.7925F860
Content-Type: text/plain;
	charset="iso-8859-1"
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select count(*) FROM items_2004_07_29 as items WHERE true AND index @@ to_t=
squery('default', '( audiovox)') ;
 count=20
-------
     4
(1 row)

aers=3D# reindex index idx_title_2004_07_29;
REINDEX
aers=3D# select count(*) FROM items_2004_07_29 as items WHERE true AND inde=
x @@ to_tsquery('default', '( audiovox)') ;
 count=20
-------
  2342
(1 row)


Here are 2 searches using a gist index, the first one has a gist index whic=
h is not properly created but does not though an error in creation.  After =
doing a few searches I noticed the numbers were way off so I reindexed.  Th=
e problem was fixed and the search works properly.

Is there a problem with indexing?  Do you know of this problem?
Is there a way to fix it?

We are getting this error for other index's including primary key indexs wh=
ere we get OID page not found errors and the index corruption as posted abo=
ve.
Sometimes when the index is broken it will cause run away searches which ea=
t up all the memory and the server needs to be restarted.

Anyways this all looks to be in index problem, vacuum/analyze does not fix =
it only reindexing does.

Thank you,

Aaron
------=_NextPart_000_0034_01C48143.7925F860
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select count(*) FROM items_2004_07_29 as i=
tems=20
WHERE true AND index @@ to_tsquery('default', '( audiovox)') ;
 cou=
nt=20

-------
     4
(1 row)


 


aers=3D# reindex index=20
idx_title_2004_07_29;
REINDEX
aers=3D# select count(*) FROM items_200=
4_07_29=20
as items WHERE true AND index @@ to_tsquery('default', '( audiovox)')=20
;
 count 
-------
  2342
(1 row)


 


Here are 2 searches using a gist index, th=
e first=20
one has a gist index which is not properly created but does not though an e=
rror=20
in creation.  After doing a few searches I noticed the numbers were wa=
y off=20
so I reindexed.  The problem was fixed and the search works=20
properly.


 


Is there a problem with indexing?  Do=
 you know=20
of this problem?


Is there a way to fix it?


 


We are getting this error for other index's including primary key inde=
xs=20
where we get OID page not found errors and the index corruption as posted=
=20
above.


Sometimes when the index is broken it will cause run away searches whi=
ch=20
eat up all the memory and the server needs to be restarted.


 


Anyways this all looks to be in index problem, vacuum/analyze does not=
 fix=20
it only reindexing does.


 


Thank you,


 


Aaron


------=_NextPart_000_0034_01C48143.7925F860--

From pgsql-performance-owner@postgresql.org  Fri Aug 13 19:41:02 2004
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From: Josh Berkus 
Reply-To: josh@agliodbs.com
Organization: Aglio Database Solutions
To: "borajetta" ,
	
Subject: Re: REINDEX needed because of index corruption need help ASAP
Date: Fri, 13 Aug 2004 15:18:41 -0700
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Aaron,

> We are getting this error for other index's including primary key indexs 
where we get OID page not found errors and the index corruption as posted 
above.
> Sometimes when the index is broken it will cause run away searches which eat 
up all the memory and the server needs to be restarted.

What version of PostgreSQL are you using?
Do you have frequent power-outs on the machine?
Have you tested for bad hard drive, controller, or memory?

Corruption of any kind on PostgreSQL is not normal.  It's usually indicative 
of a hardware problem.

-- 
-Josh Berkus
 "A developer of Very Little Brain"
 Aglio Database Solutions
 San Francisco


From pgsql-performance-owner@postgresql.org  Fri Aug 13 19:38:39 2004
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To: "borajetta" 
Cc: pgsql-performance@postgresql.org
Subject: Re: REINDEX needed because of index corruption need help ASAP 
In-reply-to:  
References: 
Comments: In-reply-to "borajetta" 
	message dated "Fri, 13 Aug 2004 14:40:26 -0700"
Date: Fri, 13 Aug 2004 18:23:59 -0400
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From: Tom Lane 
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"borajetta"  writes:
> We are getting this error for other index's including primary key indexs wh=
> ere we get OID page not found errors and the index corruption as posted abo=
> ve.
> Sometimes when the index is broken it will cause run away searches which ea=
> t up all the memory and the server needs to be restarted.

It sounds to me like you have got hardware problems.  Get out your
memory and disk tests ...

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Fri Aug 13 22:27:28 2004
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Date: Fri, 13 Aug 2004 18:27:04 -0700
From: Chris Cheston 
To: pgsql-performance@postgresql.org
Subject: Replication: Slony-I vs. Mammoth Replicator vs. ?
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HI all, I'm trying to implement a highly-scalable, high-performance,
real-time database replication system to back-up my Postgres database
as data gets written.

So far, Mammoth Replicator is looking pretty good but it costs $1000+ .  

Has anyone tried Slony-I and other replication systems?  Slony-I is
pretty new so I'm a little unsure if it's ready for a prime-time
commercial system yet.

So... wanted to put this out to the experts.  Has anyone got any
recommendations or had experiences with real-time database replication
solutions that don't rely on RAID?  The reason why I don't want to
rely on a hardware solution is because we are renting dedicated
servers and we don't have access to the boxes, only to software that
gets installed on the boxes.

Thanks,
Chris

From pgsql-hackers-owner@postgresql.org  Fri Aug 13 22:31:09 2004
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From: Bruce Momjian 
Message-Id: <200408140130.i7E1Ulf06800@candle.pha.pa.us>
Subject: Re: [PERFORM] Reiser4
In-Reply-To: 
To: =?ISO-8859-15?Q?Pierre-Fr=E9d=E9ric_Caillaud?=
	
Date: Fri, 13 Aug 2004 21:30:47 -0400 (EDT)
Cc: pgsql-performance@postgresql.org,
	PostgreSQL-development 
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Pierre-Fr�d�ric Caillaud wrote:
> 	Is there also a possibility to tell Postgres : "I don't care if I lose 30  
> seconds of transactions on this table if the power goes out, I just want  
> to be sure it's still ACID et al. compliant but you can fsync less often  
> and thus be faster" (with a possibility of setting that on a per-table  
> basis) ?

I have been thinking about this.  Informix calls it buffered logging and
it would be a good feature.

Added to TODO:

* Allow buffered WAL writes and fsync

  Instead of guaranteeing recovery of all committed transactions, this
  would provide improved performance by delaying WAL writes and fsync
  so an abrupt operating system restart might lose a few seconds of
  committed transactions but still be consistent.  We could perhaps
  remove the 'fsync' parameter (which results in an an inconsistent
  database) in favor of this capability.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

From pgsql-performance-owner@postgresql.org  Fri Aug 13 22:34:11 2004
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From: Bruce Momjian 
Message-Id: <200408140131.i7E1VgO06945@candle.pha.pa.us>
Subject: Re: Reiser4
In-Reply-To: <200408131101.52788.josh@agliodbs.com>
To: josh@agliodbs.com
Date: Fri, 13 Aug 2004 21:31:42 -0400 (EDT)
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Josh Berkus wrote:
> Pierre,
> 
> > 	Are there any plans in a future Postgresql version to support a special  
> > fsync method for Reiser4 which will use the filesystem's transaction  
> > engine, instead of an old kludge like fsync(), with a possibility of  
> > vastly enhanced performance ?
> 
> I don't know of any such in progress right now.  Why don't you start it?  It 
> would have to be an add-in since we support 28 operating systems and Reiser 
> is AFAIK Linux-only, but it sounds like an interesting experiment.
> 
> > 	Is there also a possibility to tell Postgres : "I don't care if I lose 30  
> > seconds of transactions on this table if the power goes out, I just want  
> > to be sure it's still ACID et al. compliant but you can fsync less often  
> > and thus be faster" (with a possibility of setting that on a per-table  
> > basis) ?
> 
> Not per-table, no, but otherwise take a look at the Background Writer feature 
> of 8.0.

Actually the fsync of WAL is the big performance issue here.  I added a
TODO item about it.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

From pgsql-performance-owner@postgresql.org  Fri Aug 13 22:42:38 2004
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Chris Cheston wrote:
> HI all, I'm trying to implement a highly-scalable, high-performance,
> real-time database replication system to back-up my Postgres database
> as data gets written.
> 
> So far, Mammoth Replicator is looking pretty good but it costs $1000+ .  

Yes but it includes 30 days of support and 12 months of upgrades/updates :)


> Has anyone tried Slony-I and other replication systems?  Slony-I is
> pretty new so I'm a little unsure if it's ready for a prime-time
> commercial system yet.

It really depends on your needs. They are both good systems. Slony-I is 
a bit more of a beast to get up and running, and it is a batch 
replication system that uses triggers. Once it is up and running it 
works well though.

Mammoth Replicator is easy to setup and is integrated into PostgreSQL.
However replicator is 1000+ and doesn't support promoting of slaves 
automatically (you can do it by hand) like Slony does. Replicator is
also live replication.

Sincerely,

Joshua D. Drake



> 
> So... wanted to put this out to the experts.  Has anyone got any
> recommendations or had experiences with real-time database replication
> solutions that don't rely on RAID?  The reason why I don't want to
> rely on a hardware solution is because we are renting dedicated
> servers and we don't have access to the boxes, only to software that
> gets installed on the boxes.
> 
> Thanks,
> Chris
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match


-- 
Command Prompt, Inc., home of Mammoth PostgreSQL - S/ODBC and S/JDBC
Postgresql support, programming shared hosting and dedicated hosting.
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From pgsql-hackers-owner@postgresql.org  Sat Aug 14 07:57:55 2004
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	=?iso-8859-1?q?Pierre-Fr=E9d=E9ric=20Caillaud?=
	
Subject: Re: [PERFORM] Reiser4
Date: Sat, 14 Aug 2004 12:57:37 +0200
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Bruce Momjian wrote:
> Pierre-Fr�d�ric Caillaud wrote:
> > 	Is there also a possibility to tell Postgres : "I don't care if I
> > lose 30 seconds of transactions on this table if the power goes
> > out, I just want to be sure it's still ACID et al. compliant but
> > you can fsync less often and thus be faster" (with a possibility of
> > setting that on a per-table basis) ?

Then it would be "ACI" compliant.

-- 
Peter Eisentraut
http://developer.postgresql.org/~petere/


From pgsql-performance-owner@postgresql.org  Sat Aug 14 11:41:53 2004
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From: Gaetano Mendola 
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gnari wrote:

> "G u i d o B a r o s i o"  wrote:
> 
> [speeding up 100 inserts every 5 minutes]
> 
> 
>>Tips!
>>*Delete indexes and recreate them after the insert.
> 
> 
> sounds a bit extreme, for only 100 inserts

which fsync method are you using ?
change it and see what happen

Regards
Gaetano Mendola



From pgsql-performance-owner@postgresql.org  Sat Aug 14 12:33:40 2004
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To: "Joshua D. Drake" 
Cc: Chris Cheston ,
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Subject: Re: Replication: Slony-I vs. Mammoth Replicator vs. ?
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On 8/13/2004 9:39 PM, Joshua D. Drake wrote:

> Chris Cheston wrote:
>> HI all, I'm trying to implement a highly-scalable, high-performance,
>> real-time database replication system to back-up my Postgres database
>> as data gets written.
>> 
>> So far, Mammoth Replicator is looking pretty good but it costs $1000+ .  
> 
> Yes but it includes 30 days of support and 12 months of upgrades/updates :)

The lead developer of Slony (me) is working for a company that has it 
deployed in production already and will move more mission critical 
systems to it very shortly. Guess what will be my top work priority if 
you spot a bug?

> 
> 
>> Has anyone tried Slony-I and other replication systems?  Slony-I is
>> pretty new so I'm a little unsure if it's ready for a prime-time
>> commercial system yet.
> 
> It really depends on your needs. They are both good systems. Slony-I is 
> a bit more of a beast to get up and running, and it is a batch 
> replication system that uses triggers. Once it is up and running it 
> works well though.
> 
> Mammoth Replicator is easy to setup and is integrated into PostgreSQL.
> However replicator is 1000+ and doesn't support promoting of slaves 
> automatically (you can do it by hand) like Slony does. Replicator is
> also live replication.

Once again, Joshua, would you please explain what you mean with "batch" 
and "live" replication system? Slony does group multiple "master" 
transactions into one replication transaction to improve performance 
(fewer commits on the slaves). The interval of these groups is 
configurable and for high volume DBs it is recommended to use about one 
second, which means that all commits that fall into an interval of one 
second are replicated in one transaction on the slave. On normal running 
systems this results in a replication lag of 600 to 800 milliseconds in 
average. On overloaded systems the asynchronous nature of course allows 
the slaves to fall behind.

What is a usual average replication lag of Mammoth Replicator?

What happens to the other existing slaves when you promote by hand? In 
Slony they accept the new master and continue replicating without the 
need of rebuilding from scratch. Slony has mechanisms to ensure the new 
master will be ahead or equal in the replication process at the time it 
takes over and allows client application updates.

The Slony documentation is an issue at the moment and the administrative 
tools around it are immature. The replication engine itself exceeds my 
own expectations and performs very robust.


Jan

-- 
#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me.                                  #
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From pgsql-performance-owner@postgresql.org  Sat Aug 14 13:31:05 2004
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To: Jan Wieck 
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	pgsql-performance@postgresql.org
Subject: Re: Replication: Slony-I vs. Mammoth Replicator vs. ?
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>
> Once again, Joshua, would you please explain what you mean with 
> "batch" and "live" replication system? Slony does group multiple 
> "master" transactions into one replication transaction to improve 
> performance (fewer commits on the slaves). The interval of these 
> groups is configurable and for high volume DBs it is recommended to 
> use about one second, which means that all commits that fall into an 
> interval of one second are replicated in one transaction on the slave. 
> On normal running systems this results in a replication lag of 600 to 
> 800 milliseconds in average. On overloaded systems the asynchronous 
> nature of course allows the slaves to fall behind.


Your description above is what I considered batch... you are taking a 
"batch" of transactions and replicating them versus each transaction. I 
am not saying it is bad in any way. I am just saying it is different 
that replicator.

> What is a usual average replication lag of Mammoth Replicator?
>
Obviously it depends on the system, the network connectivity between the 
systems etc... In our test systems it takes less than 100 ms to 
replicate the data. Again it depends on the size of the transaction (the 
data being moved).

> What happens to the other existing slaves when you promote by hand? 

This is something that Slony has over replicator. Currently the new 
master will force a full dump to the slaves. Of course this is already 
on the road map, thanks to Slony :) and should be resolved by months end.

> The Slony documentation is an issue at the moment and the 
> administrative tools around it are immature. The replication engine 
> itself exceeds my own expectations and performs very robust.
>
I have never suggested otherwise. My only comment about maturity is that 
their are actually many companies using replicator in production. We 
have already dealt with the 1.0 blues as they say.

I hope you understand that I, in no way have ever suggested (purposely) 
anything negative about Slony. Only that I believe they serve different 
technical solutions.

Sincerely,

Joshua D. Drake



>
> Jan
>


-- 
Command Prompt, Inc., home of Mammoth PostgreSQL - S/ODBC and S/JDBC
Postgresql support, programming shared hosting and dedicated hosting.
+1-503-667-4564 - jd@commandprompt.com - http://www.commandprompt.com
PostgreSQL Replicator -- production quality replication for PostgreSQL


From pgsql-performance-owner@postgresql.org  Sat Aug 14 14:56:54 2004
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On 8/14/2004 12:22 PM, Joshua D. Drake wrote:

> I hope you understand that I, in no way have ever suggested (purposely) 
> anything negative about Slony. Only that I believe they serve different 
> technical solutions.

You know I never took anything you said negative. I think People here 
need to know that we two have communicated and collaborated outside of 
the public mailing lists, that we still do it and that we do not 
consider each other as opponents. There is a natural overlap in the 
systems we offer and therefore there is some competition. Software 
development is a sport. For some professionals this sport happens to be 
the main source of income. But that shall not spoil the spirit here.


Jan

-- 
#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me.                                  #
#================================================== JanWieck@Yahoo.com #

From pgsql-performance-owner@postgresql.org  Sat Aug 14 18:11:56 2004
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Centuries ago, Nostradamus foresaw when jd@commandprompt.com ("Joshua D. Drake") would write:
> I hope you understand that I, in no way have ever suggested
> (purposely) anything negative about Slony. Only that I believe they
> serve different technical solutions.

Stipulating that I may have some bias ;-), I still don't find it at
all clear what the different situations are "shaped like" that lead to
Mammoth being forcibly preferable to Slony-I.

(Note that I have a pretty decent understanding about how ERS and
Slony work, so I'm not too frightened of technicalities...  I set up
instances of both on Thursday, so I'm pretty up to speed :-).)

Win32 support may be true at the moment, although I have to discount
that as we only just got the start of a beta release of native Win32
support for PostgreSQL proper.  For that very reason, I had to point
my youngest brother who needed "something better than Access" to
Firebird last Saturday; I played with my niece while he was doing the
install.  And there is little reason to think that Slony-I won't be
portable to Win32 given a little interest and effort, particularly
once work to make it play well with "pgxs" gets done.
-- 
(format nil "~S@~S" "cbbrowne" "ntlug.org")
http://www3.sympatico.ca/cbbrowne/multiplexor.html
"At  Microsoft, it doesn't  matter which  file you're  compiling, only
which flags you #define."  -- Colin Plumb

From pgsql-performance-owner@postgresql.org  Sat Aug 14 21:58:34 2004
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Subject: Re: Replication: Slony-I vs. Mammoth Replicator vs. ?
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Christopher Browne wrote:

>Centuries ago, Nostradamus foresaw when jd@commandprompt.com ("Joshua D. Drake") would write:
>  
>
>>I hope you understand that I, in no way have ever suggested
>>(purposely) anything negative about Slony. Only that I believe they
>>serve different technical solutions.
>>    
>>
>
>Stipulating that I may have some bias ;-), I still don't find it at
>all clear what the different situations are "shaped like" that lead to
>Mammoth being forcibly preferable to Slony-I.
>  
>
I would choose replicator if:

1. You want ease of setup
2. You want your each transaction to be replicated at time of commit
3. Your database is already laden with triggers
4. You are pushing a very high transactional load*

* Caveat I have no idea how well Slony performs on a system that does 
say 200,000 transactions
an hours that are heavily geared toward updates. Replicator performs 
very well in this scenario.

5. Replicators administrative tools are more mature than Slony (for 
example you know exactly what state your slaves are in with Replicator).

I would choose Slony if:

1. The fact that it is Open Source matters to you
2. The auto promotion of slaves is important*

*This will be fixed in a couple of weeks with Replicator

To be fair, in the real world ---

It doesn't make a bit of difference which one you choose it really comes 
down to this:

Replicator is dumb simple to setup. Any halfway talented person can 
setup replicator
in 30 minutes with a single master / slave configuration.

Slony is Open Source and thus a little easier on the pocket book initially.

Command Prompt, will support either one -- so the Replicator is 
commercially supported
argument is a little weak here.

Sincerely,

Joshua D. Drake




Sincerely,

Joshua D. Drake




>(Note that I have a pretty decent understanding about how ERS and
>Slony work, so I'm not too frightened of technicalities...  I set up
>instances of both on Thursday, so I'm pretty up to speed :-).)
>
>Win32 support may be true at the moment, although I have to discount
>that as we only just got the start of a beta release of native Win32
>support for PostgreSQL proper.  For that very reason, I had to point
>my youngest brother who needed "something better than Access" to
>Firebird last Saturday; I played with my niece while he was doing the
>install.  And there is little reason to think that Slony-I won't be
>portable to Win32 given a little interest and effort, particularly
>once work to make it play well with "pgxs" gets done.
>  
>


-- 
Command Prompt, Inc., home of Mammoth PostgreSQL - S/ODBC and S/JDBC
Postgresql support, programming shared hosting and dedicated hosting.
+1-503-667-4564 - jd@commandprompt.com - http://www.commandprompt.com
PostgreSQL Replicator -- production quality replication for PostgreSQL


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Christopher Browne wrote:


  
Centuries ago, Nostradamus foresaw when jd@commandprompt.com ("Joshua D. Drake") would write:
  

  

    
I hope you understand that I, in no way have ever suggested
(purposely) anything negative about Slony. Only that I believe they
serve different technical solutions.
    

  

  

Stipulating that I may have some bias ;-), I still don't find it at
all clear what the different situations are "shaped like" that lead to
Mammoth being forcibly preferable to Slony-I.
  



I would choose replicator if:



1. You want ease of setup

2. You want your each transaction to be replicated at time of commit

3. Your database is already laden with triggers

4. You are pushing a very high transactional load*



* Caveat I have no idea how well Slony performs on a system that does
say 200,000 transactions

an hours that are heavily geared toward updates. Replicator performs
very well in this scenario.



5. Replicators administrative tools are more mature than Slony (for
example you know exactly what state your slaves are in with Replicator).



I would choose Slony if:



1. The fact that it is Open Source matters to you

2. The auto promotion of slaves is important*



*This will be fixed in a couple of weeks with Replicator



To be fair, in the real world --- 



It doesn't make a bit of difference which one you choose it really
comes down to this:



Replicator is dumb simple to setup. Any halfway talented person can
setup replicator

in 30 minutes with a single master / slave configuration.



Slony is Open Source and thus a little easier on the pocket book
initially.



Command Prompt, will support either one -- so the Replicator is
commercially supported

argument is a little weak here. 



Sincerely,



Joshua D. Drake









Sincerely,



Joshua D. Drake











  
(Note that I have a pretty decent understanding about how ERS and
Slony work, so I'm not too frightened of technicalities...  I set up
instances of both on Thursday, so I'm pretty up to speed :-).)

Win32 support may be true at the moment, although I have to discount
that as we only just got the start of a beta release of native Win32
support for PostgreSQL proper.  For that very reason, I had to point
my youngest brother who needed "something better than Access" to
Firebird last Saturday; I played with my niece while he was doing the
install.  And there is little reason to think that Slony-I won't be
portable to Win32 given a little interest and effort, particularly
once work to make it play well with "pgxs" gets done.
  








-- 
Command Prompt, Inc., home of Mammoth PostgreSQL - S/ODBC and S/JDBC
Postgresql support, programming shared hosting and dedicated hosting.
+1-503-667-4564 - jd@commandprompt.com - http://www.commandprompt.com
PostgreSQL Replicator -- production quality replication for PostgreSQL




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Date: Sun, 15 Aug 2004 03:03:28 GMT
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I thought this could generate some interesting discussion.  Essentially, 
there are three queries below, two using sub-queries to change the way 
the randomized information (works first by author and then by work) and 
the original which simply randomizes out of all works available.

The one not using sub-queries under EXPLAIN ANALYZE proves itself to be 
less efficient and have a far higher cost then those with the penalty of 
a sub-query.   Since this seems to be counter to what I have been told 
in the past, I thought I would bring this forward and get some 
enlightenment.

	Martin Foster
	Creator/Designer Ethereal Realms
	martin@ethereal-realms.org

-----------------------------------------------------------------------

SELECT
  g.GalleryID,
  w.WorkID,
  w.WorkName,
  w.WorkImageThumbnail,
  g.GalleryRating,
  g.GalleryPenName
FROM ethereal.Work w, ethereal.Gallery g
WHERE w.GalleryID = g.GalleryID
  AND g.GalleryPrivacy = 'no'
  AND w.WorkImageThumbnail IS NOT NULL
  AND g.PuppeteerLogin = (SELECT PuppeteerLogin
   FROM ethereal.Gallery
   WHERE GalleryType='image'
   GROUP BY PuppeteerLogin
   ORDER BY RANDOM() LIMIT 1)
ORDER BY RANDOM() LIMIT 1

  Limit  (cost=60.70..60.70 rows=1 width=100) (actual time=1.013..1.013 
rows=0 loops=1)
    InitPlan
      ->  Limit  (cost=6.36..6.37 rows=1 width=11) (actual 
time=0.711..0.713 rows=1 loops=1)
            ->  Sort  (cost=6.36..6.45 rows=33 width=11) (actual 
time=0.708..0.708 rows=1 loops=1)
                  Sort Key: random()
                  ->  HashAggregate  (cost=5.45..5.53 rows=33 width=11) 
(actual time=0.420..0.553 rows=46 loops=1)
                        ->  Seq Scan on gallery  (cost=0.00..5.30 
rows=60 width=11) (actual time=0.007..0.227 rows=59 loops=1)
                              Filter: ((gallerytype)::text = 'image'::text)
    ->  Sort  (cost=54.33..54.37 rows=16 width=100) (actual 
time=1.009..1.009 rows=0 loops=1)
          Sort Key: random()
          ->  Nested Loop  (cost=0.00..54.01 rows=16 width=100) (actual 
time=0.981..0.981 rows=0 loops=1)
                ->  Seq Scan on gallery g  (cost=0.00..5.56 rows=2 
width=24) (actual time=0.855..0.888 rows=1 loops=1)
                      Filter: (((galleryprivacy)::text = 'no'::text) AND 
((puppeteerlogin)::text = ($0)::text))
                ->  Index Scan using pkwork on "work" w 
(cost=0.00..24.10 rows=8 width=80) (actual time=0.080..0.080 rows=0 loops=1)
                      Index Cond: (w.galleryid = "outer".galleryid)
                      Filter: (workimagethumbnail IS NOT NULL)
  Total runtime: 1.211 ms

-----------------------------------------------------------------------

SELECT
  g.GalleryID,
  w.WorkID,
  w.WorkName,
  w.WorkImageThumbnail,
  g.GalleryRating,
  g.GalleryPenName
FROM ethereal.Work w, ethereal.Gallery g
WHERE w.GalleryID = g.GalleryID
  AND g.GalleryPrivacy = 'no'
  AND w.WorkImageThumbnail IS NOT NULL
  AND g.GalleryPenName = (SELECT GalleryPenName
   FROM ethereal.Gallery
   WHERE GalleryType='image'
   GROUP BY GalleryPenName
   ORDER BY RANDOM() LIMIT 1)
ORDER BY RANDOM() LIMIT 1

  Limit  (cost=59.92..59.92 rows=1 width=100) (actual time=0.904..0.906 
rows=1 loops=1)
    InitPlan
      ->  Limit  (cost=6.69..6.69 rows=1 width=14) (actual 
time=0.731..0.733 rows=1 loops=1)
            ->  Sort  (cost=6.69..6.79 rows=42 width=14) (actual 
time=0.729..0.729 rows=1 loops=1)
                  Sort Key: random()
                  ->  HashAggregate  (cost=5.45..5.56 rows=42 width=14) 
(actual time=0.431..0.568 rows=48 loops=1)
                        ->  Seq Scan on gallery  (cost=0.00..5.30 
rows=60 width=14) (actual time=0.011..0.233 rows=59 loops=1)
                              Filter: ((gallerytype)::text = 'image'::text)
    ->  Sort  (cost=53.23..53.27 rows=16 width=100) (actual 
time=0.899..0.899 rows=1 loops=1)
          Sort Key: random()
          ->  Nested Loop  (cost=0.00..52.91 rows=16 width=100) (actual 
time=0.808..0.862 rows=6 loops=1)
                ->  Index Scan using idxgallery_pen on gallery g 
(cost=0.00..4.45 rows=2 width=24) (actual time=0.767..0.769 rows=1 loops=1)
                      Index Cond: ((gallerypenname)::text = ($0)::text)
                      Filter: ((galleryprivacy)::text = 'no'::text)
                ->  Index Scan using pkwork on "work" w 
(cost=0.00..24.10 rows=8 width=80) (actual time=0.020..0.042 rows=6 loops=1)
                      Index Cond: (w.galleryid = "outer".galleryid)
                      Filter: (workimagethumbnail IS NOT NULL)
  Total runtime: 1.117 ms

-----------------------------------------------------------------------

SELECT
  g.GalleryID,
  w.WorkID,
  w.WorkName,
  w.WorkImageThumbnail,
  g.GalleryRating,
  g.GalleryPenName
FROM ethereal.Work w, ethereal.Gallery g
WHERE w.GalleryID = g.GalleryID
  AND g.GalleryType = 'image'
  AND g.GalleryPrivacy = 'no'
  AND w.WorkImageThumbnail IS NOT NULL
ORDER BY RANDOM() LIMIT 1

--------
  Limit  (cost=111.73..111.73 rows=1 width=100) (actual 
time=13.021..13.023 rows=1 loops=1)
    ->  Sort  (cost=111.73..113.70 rows=786 width=100) (actual 
time=13.017..13.017 rows=1 loops=1)
          Sort Key: random()
          ->  Hash Join  (cost=5.55..73.93 rows=786 width=100) (actual 
time=1.081..8.320 rows=803 loops=1)
                Hash Cond: ("outer".galleryid = "inner".galleryid)
                ->  Seq Scan on "work" w  (cost=0.00..54.47 rows=817 
width=80) (actual time=0.006..2.207 rows=817 loops=1)
                      Filter: (workimagethumbnail IS NOT NULL)
                ->  Hash  (cost=5.30..5.30 rows=100 width=24) (actual 
time=0.669..0.669 rows=0 loops=1)
                      ->  Seq Scan on gallery g  (cost=0.00..5.30 
rows=100 width=24) (actual time=0.020..0.402 rows=100 loops=1)
                            Filter: ((galleryprivacy)::text = 'no'::text)
  Total runtime: 13.252 ms


From pgsql-performance-owner@postgresql.org  Sun Aug 15 00:55:05 2004
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To: Martin Foster 
Cc: pgsql-performance@postgresql.org
Subject: Re: Faster with a sub-query then without 
In-reply-to: <4oATc.14571$S55.11652@clgrps12> 
References: <4oATc.14571$S55.11652@clgrps12>
Comments: In-reply-to Martin Foster 
	message dated "Sun, 15 Aug 2004 03:03:28 +0000"
Date: Sat, 14 Aug 2004 23:55:03 -0400
Message-ID: <15917.1092542103@sss.pgh.pa.us>
From: Tom Lane 
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Martin Foster  writes:
> The one not using sub-queries under EXPLAIN ANALYZE proves itself to be 
> less efficient and have a far higher cost then those with the penalty of 
> a sub-query.   Since this seems to be counter to what I have been told 
> in the past, I thought I would bring this forward and get some 
> enlightenment.

The ones with the subqueries are not having to form the full join of W
and G; they just pick a few rows out of G and look up the matching W
rows.

The "subquery penalty" is nonexistent in this case because the
subqueries are not dependent on any variables from the outer query, and
so they need be evaluated only once, rather than once per outer-query
row which is what I suppose you were expecting.  This is reflected in
the EXPLAIN output: notice they are shown as InitPlans not SubPlans.
The outputs of the InitPlans are essentially treated as constants (shown
as $0 in the EXPLAIN output) and the outer plan is approximately what
it would be if you'd written WHERE g.field = 'constant' instead of
WHERE g.field = (select ...)

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Sun Aug 15 13:00:20 2004
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Date: Sun, 15 Aug 2004 10:00:14 -0600
From: Michael Fuhr 
To: pgsql-performance@postgresql.org
Subject: Slow joins against set-returning functions
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PostgreSQL versions: 7.4.3, 8.0.0beta1

Joins against set-returning functions can be slow.  Here's a simple
example (in 8.0.0beta1, the gen_series function can be replaced
with generate_series):

  CREATE FUNCTION gen_series(INTEGER, INTEGER) RETURNS SETOF INTEGER AS '
  DECLARE
      xstart  ALIAS FOR $1;
      xend    ALIAS FOR $2;
      x       INTEGER;
  BEGIN
      FOR x IN xstart .. xend LOOP
          RETURN NEXT x;
      END LOOP;
  
      RETURN;
  END;
  ' LANGUAGE plpgsql IMMUTABLE STRICT;
  
  CREATE TABLE stuff (
      id    INTEGER NOT NULL PRIMARY KEY,
      item  VARCHAR(32) NOT NULL
  );
  
  INSERT INTO stuff (id, item)
    SELECT id, 'Item ' || id FROM gen_series(1, 100000) AS f(id);
  
  ANALYZE stuff;

Here are two queries; notice how the second query, which uses higher
numbers for the join key, is much slower than the first, apparently
due to an inefficient index scan:

  EXPLAIN ANALYZE
    SELECT stuff.* FROM stuff JOIN gen_series(1, 10) AS f(id) USING (id);
  
   Merge Join  (cost=62.33..2544.33 rows=1001 width=17) (actual time=1.398..1.950 rows=10 loops=1)
     Merge Cond: ("outer".id = "inner".id)
     ->  Index Scan using stuff_pkey on stuff  (cost=0.00..2217.00 rows=100000 width=17) (actual time=0.667..0.860 rows=11 loops=1)
     ->  Sort  (cost=62.33..64.83 rows=1000 width=4) (actual time=0.646..0.670 rows=10 loops=1)
           Sort Key: f.id
           ->  Function Scan on gen_series f  (cost=0.00..12.50 rows=1000 width=4) (actual time=0.403..0.478 rows=10 loops=1)
   Total runtime: 2.529 ms
  (7 rows)
  
  EXPLAIN ANALYZE
    SELECT stuff.* FROM stuff JOIN gen_series(99991, 100000) AS f(id) USING (id);
  
   Merge Join  (cost=62.33..2544.33 rows=1001 width=17) (actual time=2907.078..2907.618 rows=10 loops=1)
     Merge Cond: ("outer".id = "inner".id)
     ->  Index Scan using stuff_pkey on stuff  (cost=0.00..2217.00 rows=100000 width=17) (actual time=0.107..2270.722 rows=100000 loops=1)
     ->  Sort  (cost=62.33..64.83 rows=1000 width=4) (actual time=0.630..0.654 rows=10 loops=1)
           Sort Key: f.id
           ->  Function Scan on gen_series f  (cost=0.00..12.50 rows=1000 width=4) (actual time=0.392..0.469 rows=10 loops=1)
   Total runtime: 2908.205 ms
  (7 rows)

If I turn off enable_mergejoin then both queries are fast:

  SET enable_mergejoin TO off;
  
  EXPLAIN ANALYZE
    SELECT stuff.* FROM stuff JOIN gen_series(1, 10) AS f(id) USING (id);
  
   Nested Loop  (cost=0.00..3038.50 rows=1001 width=17) (actual time=0.600..1.912 rows=10 loops=1)
     ->  Function Scan on gen_series f  (cost=0.00..12.50 rows=1000 width=4) (actual time=0.395..0.482 rows=10 loops=1)
     ->  Index Scan using stuff_pkey on stuff  (cost=0.00..3.01 rows=1 width=17) (actual time=0.091..0.107 rows=1 loops=10)
           Index Cond: (stuff.id = "outer".id)
   Total runtime: 2.401 ms
  (5 rows)
  
  EXPLAIN ANALYZE
    SELECT stuff.* FROM stuff JOIN gen_series(99991, 100000) AS f(id) USING (id);
  
   Nested Loop  (cost=0.00..3038.50 rows=1001 width=17) (actual time=0.586..1.891 rows=10 loops=1)
     ->  Function Scan on gen_series f  (cost=0.00..12.50 rows=1000 width=4) (actual time=0.394..0.479 rows=10 loops=1)
     ->  Index Scan using stuff_pkey on stuff  (cost=0.00..3.01 rows=1 width=17) (actual time=0.089..0.105 rows=1 loops=10)
           Index Cond: (stuff.id = "outer".id)
   Total runtime: 2.374 ms
  (5 rows)

Is the planner doing something wrong here?

Thanks.

-- 
Michael Fuhr
http://www.fuhr.org/~mfuhr/

From pgsql-performance-owner@postgresql.org  Sun Aug 15 13:01:34 2004
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Message-ID: <411F88D6.3000300@ethereal-realms.org>
Date: Sun, 15 Aug 2004 12:01:26 -0400
From: Martin Foster 
Organization: Ethereal Realms
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To: Tom Lane 
Cc: PostgreSQL Performance 
Subject: Re: Faster with a sub-query then without
References: <4oATc.14571$S55.11652@clgrps12> <15917.1092542103@sss.pgh.pa.us>
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Tom Lane wrote:
> Martin Foster  writes:
> 
>>The one not using sub-queries under EXPLAIN ANALYZE proves itself to be 
>>less efficient and have a far higher cost then those with the penalty of 
>>a sub-query.   Since this seems to be counter to what I have been told 
>>in the past, I thought I would bring this forward and get some 
>>enlightenment.
> 
> 
> The ones with the subqueries are not having to form the full join of W
> and G; they just pick a few rows out of G and look up the matching W
> rows.
> 
> The "subquery penalty" is nonexistent in this case because the
> subqueries are not dependent on any variables from the outer query, and
> so they need be evaluated only once, rather than once per outer-query
> row which is what I suppose you were expecting.  This is reflected in
> the EXPLAIN output: notice they are shown as InitPlans not SubPlans.
> The outputs of the InitPlans are essentially treated as constants (shown
> as $0 in the EXPLAIN output) and the outer plan is approximately what
> it would be if you'd written WHERE g.field = 'constant' instead of
> WHERE g.field = (select ...)
> 
> 			regards, tom lane

That would explain it overall.  Still, it does seem unusual when one 
puts in additional code, which most literature warns you about and you 
actually gain a speed boost.

Thanks!

	Martin Foster
	Creator/Designer Ethereal Realms
	martin@ethereal-realms.org



From pgsql-performance-owner@postgresql.org  Sun Aug 15 14:21:42 2004
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To: Michael Fuhr 
Cc: pgsql-performance@postgresql.org
Subject: Re: Slow joins against set-returning functions 
In-reply-to: <20040815160014.GA85211@winnie.fuhr.org> 
References: <20040815160014.GA85211@winnie.fuhr.org>
Comments: In-reply-to Michael Fuhr 
	message dated "Sun, 15 Aug 2004 10:00:14 -0600"
Date: Sun, 15 Aug 2004 13:21:30 -0400
Message-ID: <28003.1092590490@sss.pgh.pa.us>
From: Tom Lane 
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Michael Fuhr  writes:
> Is the planner doing something wrong here?

Hard to see how it can be very smart with no idea about what the
function is going to return :-(.

I'd say that the mergejoin plan is actually a good choice given the
limited amount of info, because it has the least degradation when the
input varies from what you expected.  Those "better" nestloop plans
could easily be very far worse, if the function returned more than a
trivial number of rows.

The reason the two mergejoin cases differ so much is that the scan of
the other relation can stop as soon as we've exhausted the function
output.  Evidently scanning to key 10 doesn't traverse much of
stuff_pkey while scanning to key 100000 does.  The planner is aware of
that effect, but with no information about the maximum key value to be
expected from the function scan, it can't apply the knowledge.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Sun Aug 15 14:48:08 2004
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Using this SQL:

EXPLAIN ANALYZE
SELECT DISTINCT
        sessionid,
        '2004-33' AS "yearweek",
        nd.niveau
INTO TEMP
        distinct_session
FROM
        httplog h ,niveaudir nd
WHERE
        hitDateTime>('now'::timestamp with time zone-'1440 min'::interval)
        and h.hostid=(select hostnameid from hostname where hostname='www.forbrug.dk')
        and h.statusid!=404
        and h.pathid=nd.pathid
;


I get this output:

QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Unique  (cost=5680.00..5766.70 rows=8670 width=26) (actual 
time=17030.802..20044.614 rows=68213 loops=1)
   InitPlan
     ->  Index Scan using hostname_hostname_key on hostname  
(cost=0.00..5.42 rows=1 width=4) (actual time=0.101..0.106 rows=1 loops=1)
           Index Cond: (hostname = 'www.forbrug.dk'::text)
   ->  Sort  (cost=5674.58..5696.25 rows=8670 width=26) (actual 
time=17030.792..17689.650 rows=174714 loops=1)
         Sort Key: h.sessionid, '2004-33'::text, nd.niveau
         ->  Merge Join  (cost=4500.70..5107.48 rows=8670 width=26) 
(actual time=3226.955..3966.011 rows=174714 loops=1)
               Merge Cond: ("outer".pathid = "inner".pathid)
               ->  Index Scan using niveaudir_pathid on niveaudir nd  
(cost=0.00..465.59 rows=22715 width=26) (actual time=0.181..52.248 
rows=22330 loops=1)
               ->  Sort  (cost=4500.70..4522.38 rows=8670 width=8) (actual 
time=3226.666..3443.092 rows=174714 loops=1)
                     Sort Key: h.pathid
                     ->  Index Scan using httplog_hitdatetime on httplog h  
(cost=0.00..3933.61 rows=8670 width=8) (actual time=0.425..1048.428 
rows=174714 loops=1)
                           Index Cond: (hitdatetime > '2004-08-14 
16:41:16.855829+02'::timestamp with time zone)
                           Filter: ((hostid = $0) AND (statusid <> 404))
 Total runtime: 20478.174 ms
(15 rows)

As I read it the output tells me what was done during the milliseconds:

0.101..0.106
0.181..52.248
0.425..1048.428
3226.666..3443.092
3226.955..3966.011
17030.792..17689.650
17030.802..20044.614

However, there are a few large gaps. What is happening during:

1048.428..3226.666 (2 secs)
3966.011..17030.792 (13 secs!)

This is the major part of the time but this is not accounted for in the
explain analyze output. It seems PostgreSQL is doing stuff that is not
part of the query plan. How do I get to know what this "stuff" is?


/Ole

From pgsql-performance-owner@postgresql.org  Sun Aug 15 15:21:31 2004
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To: Ole Tange 
Cc: pgsql-performance@postgresql.org
Subject: Re: Help interpreting explain analyze output 
In-reply-to:  
References: 
Comments: In-reply-to Ole Tange 
	message dated "Sun, 15 Aug 2004 19:47:53 +0200"
Date: Sun, 15 Aug 2004 14:13:39 -0400
Message-ID: <28313.1092593619@sss.pgh.pa.us>
From: Tom Lane 
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Ole Tange  writes:
> As I read it the output tells me what was done during the milliseconds:

No, you have a fundamental misconception here.  The notation means that
the first output row from a plan step was delivered after X
milliseconds, and the last row after Y milliseconds.

The "gap" you are looking at is the time to do the Sort (since a sort
can't deliver the first output row until it's finished the sort).

It is gonna take a while to sort 175000 rows ... but possibly increasing
sort_mem would help.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Sun Aug 15 15:33:17 2004
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Date: Sun, 15 Aug 2004 19:24:08 +0100
From: Richard Poole 
To: pgsql-performance@postgresql.org
Subject: Re: Help interpreting explain analyze output
Message-ID: <20040815182407.GA21608@guests.deus.net>
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On Sun, Aug 15, 2004 at 07:47:53PM +0200, Ole Tange wrote:

> QUERY PLAN
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------
>  Unique  (cost=5680.00..5766.70 rows=8670 width=26) (actual 
> time=17030.802..20044.614 rows=68213 loops=1)
>    InitPlan
>      ->  Index Scan using hostname_hostname_key on hostname  
> (cost=0.00..5.42 rows=1 width=4) (actual time=0.101..0.106 rows=1 loops=1)
>            Index Cond: (hostname = 'www.forbrug.dk'::text)
>    ->  Sort  (cost=5674.58..5696.25 rows=8670 width=26) (actual 
> time=17030.792..17689.650 rows=174714 loops=1)
>          Sort Key: h.sessionid, '2004-33'::text, nd.niveau
>          ->  Merge Join  (cost=4500.70..5107.48 rows=8670 width=26) 
> (actual time=3226.955..3966.011 rows=174714 loops=1)
>                Merge Cond: ("outer".pathid = "inner".pathid)
>                ->  Index Scan using niveaudir_pathid on niveaudir nd  
> (cost=0.00..465.59 rows=22715 width=26) (actual time=0.181..52.248 
> rows=22330 loops=1)
>                ->  Sort  (cost=4500.70..4522.38 rows=8670 width=8) (actual 
> time=3226.666..3443.092 rows=174714 loops=1)
>                      Sort Key: h.pathid
>                      ->  Index Scan using httplog_hitdatetime on httplog h  
> (cost=0.00..3933.61 rows=8670 width=8) (actual time=0.425..1048.428 
> rows=174714 loops=1)
>                            Index Cond: (hitdatetime > '2004-08-14 
> 16:41:16.855829+02'::timestamp with time zone)
>                            Filter: ((hostid = $0) AND (statusid <> 404))
>  Total runtime: 20478.174 ms
> (15 rows)
> 
> As I read it the output tells me what was done during the milliseconds:

The first time given is not the time when this stage of the plan starts
to execute, but the time when it returns its first row. So most of the
time in this query is being spent doing the two sorts - in a sort, of
course, most of the work has to be done before any rows can be returned.


Richard

From pgsql-performance-owner@postgresql.org  Sun Aug 15 16:08:32 2004
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Date: Sun, 15 Aug 2004 21:08:19 +0200 (CEST)
From: Ole Tange 
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Subject: Re: Help interpreting explain analyze output 
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On Sun, 15 Aug 2004, Tom Lane wrote:

> Ole Tange  writes:
> > As I read it the output tells me what was done during the milliseconds:
> 
> No, you have a fundamental misconception here.  The notation means that
> the first output row from a plan step was delivered after X
> milliseconds, and the last row after Y milliseconds.

Thanks. For a novice tuner like me it would be nice if you could see more
easily where the time was spent. However, the output is _far_ more
intuitive that MySQL's.

> It is gonna take a while to sort 175000 rows ... but possibly increasing
> sort_mem would help.

It didn't. However, I could reformulate the DISTINCT query as a GROUP BY
on all the selected fields and this uses Hash aggregate which is far
faster.

Now I am curious: Why isn't DISTINCT implemented using a Hash aggregate?


/Ole

From pgsql-performance-owner@postgresql.org  Sun Aug 15 16:40:44 2004
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To: Ole Tange 
Cc: pgsql-performance@postgresql.org
Subject: Re: Help interpreting explain analyze output 
In-reply-to:  
References: 
	<28313.1092593619@sss.pgh.pa.us>
	
Comments: In-reply-to Ole Tange 
	message dated "Sun, 15 Aug 2004 21:08:19 +0200"
Date: Sun, 15 Aug 2004 15:40:37 -0400
Message-ID: <29079.1092598837@sss.pgh.pa.us>
From: Tom Lane 
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Ole Tange  writes:
> Now I am curious: Why isn't DISTINCT implemented using a Hash aggregate?

Partly lack of round tuits, partly the fact that it is closely
intertwined with ORDER BY and I'm not sure what side-effects would
arise from separating them.  In particular, the DISTINCT ON special
case stops making any sense at all if it's not tied to a sort/uniq
underlying implementation.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Sun Aug 15 17:12:09 2004
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>>You're not getting much of a bump with this server. The CPU is
>>incrementally faster -- in the absolutely best case scenario where your
>>queries are 100% cpu-bound, that's about ~25%-30% faster.
> 
> 
> What about using Dual Athlon MP instead of a Xeon? Would be much less expensive,
> but have higher performance (I think).

You're not going to be able to get a Dual Athlon MP for the same price 
as a single Xeon. A few years back, this was the case because Xeon CPUs 
& MBs had a huge premium over Athlon. This is no longer true mainly 
because the number of people carrying Athlon MP motherboards has dropped 
down drastically. Go to pricewatch.com and do a search for 760MPX -- you 
get a mere 8 entries. Not surprisingly because who would not want to 
spend a few pennies more for a much superior Dual Opteron? The few 
sellers you see now just keep stuff in inventory for people who need 
replacement parts for emergencies and are willing to pay up the nose 
because it is an emergency.

From pgsql-performance-owner@postgresql.org  Mon Aug 16 12:22:36 2004
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Date: Mon, 16 Aug 2004 17:12:34 +0200
From: Stef 
To: pgsql-performance@postgresql.org
Subject: Strange problems with more memory.
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Hi all, 

I'm running postgres 7.3.4 on a quad Xeon 2.8 GHz with 
Mem:  1057824768 309108736 748716032        0 12242944 256413696
Swap: 518053888  8630272 509423616

on Linux version 2.4.26-custom 

Data directory is mounted with noatime.

Nothing else but one 11GB database is running on this machine.
When the database was created, I changed the following defaults :
shared_buffers = 24415
sort_mem = 5120
vacuum_mem = 10240
commit_delay = 5000
commit_siblings = 100

These settings worked fine, but were not optimal, I thought, and processing
stuff on this database was a bit slow. The machine is not nearly used to it's
capacity, and I realized that disk IO is what's slowing me down. So I
decided to give postgres more shared memory  and much more sort memory,
as it does a lot of "group by'"s and "order by"'s during the nightly processing.
These were the new settings I tried :
shared_buffers = 61035
sort_mem = 97657

I thought because it's only one process that runs queries exclusively at night,
I should be able to set the sort_mem this high without worrying about running
out of memory. 

It seems I was mistaking, as I started getting these kind of errors in dmesg :
VM: killing process postmaster
__alloc_pages: 0-order allocation failed (gfp=0x1d2/0)
__alloc_pages: 0-order allocation failed (gfp=0x1d2/0)
VM: killing process postmaster

and I kept on getting these postgres errors :
ERROR:  Index ???? is not a btree

I systematically reduced the shared buffers back down to 24415, and this kept
on happening. As soon as I reduced sort_mem back to under 10000,the problem
stopped. But the database is just as slow as before. (By slow I mean not as fast as it should
be on such a powerful machine compared to much worse machines running the same processes)

What can I do to make this database run faster on this machine.
Can anyone suggest how I would go about speeding up this database. 

I need to prepare a database three times the size of this one, running the same processes,
and I don't know what improvements I can do on hardware to make this possible.

On the current machine I can easily get another 1GB  or 2GB of memory, but will that help at all?
Without going into the details of exactly the queries that run on this machine, what would be needed to
make postgres run very fast on this machine?

Please help.

Kind Regards
Stefan

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One more point for your list:

Choose Slony if Replicator doesn't support your platform. :-)


-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Vivek Khera, Ph.D.                Khera Communications, Inc.
Internet: khera@kciLink.com       Rockville, MD  +1-301-869-4449 x806
AIM: vivekkhera Y!: vivek_khera   http://www.khera.org/~vivek/

From pgsql-performance-owner@postgresql.org  Mon Aug 16 12:41:19 2004
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To: Stef 
Cc: pgsql-performance@postgresql.org
Subject: Re: Strange problems with more memory. 
In-reply-to: <20040816171234.5a9bac8f@svb.ucs.co.za> 
References: <20040816171234.5a9bac8f@svb.ucs.co.za>
Comments: In-reply-to Stef 
	message dated "Mon, 16 Aug 2004 17:12:34 +0200"
Date: Mon, 16 Aug 2004 11:41:16 -0400
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From: Tom Lane 
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Stef  writes:
> It seems I was mistaking, as I started getting these kind of errors in dmesg :
> VM: killing process postmaster
> __alloc_pages: 0-order allocation failed (gfp=0x1d2/0)
> __alloc_pages: 0-order allocation failed (gfp=0x1d2/0)
> VM: killing process postmaster

This looks like the infamous OOM-kill kernel bug^H^H^Hfeature.  Turn off
memory overallocation in your kernel to get more stable behavior when
pushing the limits of available memory.

> But the database is just as slow as before. (By slow I mean not as
> fast as it should be on such a powerful machine compared to much worse
> machines running the same processes)

If your concern is with a single nightly process, then that quad Xeon is
doing squat for you, because only one of the processors will be working.
See if you can divide up the processing into several jobs that can run
in parallel.  (Of course, if the real problem is that you are disk I/O
bound, nothing will help except better disk hardware.  Way too many
people think they should buy a super-fast CPU and attach it to
consumer-grade IDE disks.  For database work you're usually better off
spending your money on good disks...)

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Mon Aug 16 13:23:14 2004
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From: Stef 
To: pgsql-performance@postgresql.org
Cc: Tom Lane 
Subject: Re: Strange problems with more memory.
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Tom Lane mentioned :
=> Turn off
=> memory overallocation in your kernel to get more stable behavior when
=> pushing the limits of available memory.

I think this will already help a lot.
Thanks!!

=> If your concern is with a single nightly process, then that quad Xeon is
=> doing squat for you, because only one of the processors will be working.
=> See if you can divide up the processing into several jobs that can run
=> in parallel.  (Of course, if the real problem is that you are disk I/O
=> bound, nothing will help except better disk hardware.  Way too many
=> people think they should buy a super-fast CPU and attach it to
=> consumer-grade IDE disks.  For database work you're usually better off
=> spending your money on good disks...)

Got 3 10000 rpm SCSI raid5 on here. I doubt I will get much better than that
without losing both arms and legs... 

I think I'll try and even out the disk IO a bit and get 4 processes running in parallel.
At least I can move forward again.

Thanks again!

Kind Regards
Stefan

From pgsql-performance-owner@postgresql.org  Mon Aug 16 20:08:52 2004
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From: Josh Berkus 
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Organization: Aglio Database Solutions
To: "Harmon S. Nine" 
Subject: Re: Timestamp-based indexing
Date: Mon, 16 Aug 2004 16:09:13 -0700
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Harmon,

> A "VACUUM FULL ANALYZE"  is performed every 3 hours.

The FULL part should not be necessary if you've set your max_fsm_pages high 
enough.

> Given there are 10080 minutes per week, the planner could, properly
> configured, estimate the number of rows returned by such a query to be:
>
> 10 min/ 10080 min  *  400,000 = 0.001 * 400,000 = 400.

The planner doesn't work that way.

> monitor=# explain analyze select * from "eventtable" where timestamp >
> CURRENT_TIMESTAMP - INTERVAL '10 minutes';

Hmmm.  What verison of PostgreSQL are you running?  I seem to remember an 
issue in one version with selecting comparisons against now().    What 
happens when you supply a constant instead of ( current_timestamp - interval 
'10 minutes' ) ?

> Here's something strange.  We try to disable sequential scans, but to no
> avail.  The estimated cost skyrockets, though:

That's how "enable_*=false" works in most cases.

-- 
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Mon Aug 16 20:15:58 2004
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From: Josh Berkus 
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Organization: Aglio Database Solutions
To: Algolist 
Subject: Re: Index type
Date: Mon, 16 Aug 2004 16:16:27 -0700
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Ilia,

> If I create btree index on all columns (A,B,C..), here is what explain
> analyze gives me:
> -----------------------------------------------------------------
>  Index Scan using all_ind on test2  (cost=0.00..4.51 rows=1 width=24)
> (actual ti me=0.000..0.000 rows=5 loops=1)
>    Index Cond: ((a >= '2004-07-20 23:50:50'::timestamp without time zone)
> AND (a <= '2004-07-21 23:50:50'::timestamp without time zone) AND (b >=
> '2004-07-20 23
>
> :50:50'::timestamp without time zone) AND (b <= '2004-07-21
> : 23:50:50'::timestamp
>
>  without time zone) AND (c >= '2004-07-20 23:50:50'::timestamp without time
> zone ) AND (c <= '2004-07-21 23:50:50'::timestamp without time zone))

Looks good to me.   It's a fully indexed search, which it should be with 
BETWEEN.  The only thing you need to ask yourself is whether or not you've 
selected the columns in the most selective order (e.g. most selective column 
first).

-- 
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Mon Aug 16 20:25:53 2004
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To: josh@agliodbs.com
Cc: "Harmon S. Nine" ,
	pgsql-performance@postgresql.org
Subject: Re: Timestamp-based indexing 
In-reply-to: <200408161609.13018.josh@agliodbs.com> 
References: <410519F6.5020806@netarx.com>
	<200408161609.13018.josh@agliodbs.com>
Comments: In-reply-to Josh Berkus 
	message dated "Mon, 16 Aug 2004 16:09:13 -0700"
Date: Mon, 16 Aug 2004 19:25:41 -0400
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From: Tom Lane 
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Josh Berkus  writes:
>> monitor=# explain analyze select * from "eventtable" where timestamp >
>> CURRENT_TIMESTAMP - INTERVAL '10 minutes';

> Hmmm.  What verison of PostgreSQL are you running?  I seem to remember an 
> issue in one version with selecting comparisons against now().

I'm also wondering about the exact datatype of the "timestamp" column.
If it's timestamp without timezone, then the above is a cross-datatype
comparison (timestamp vs timestamptz) and hence not indexable before
8.0.  This could be fixed easily by using the right current-time
function, viz LOCALTIMESTAMP not CURRENT_TIMESTAMP.  (Consistency has
obviously never been a high priority with the SQL committee :-(.)

Less easily but possibly better in the long run, change the column type
to timestamp with time zone.  IMHO, columns representing definable
real-world time instants should always be timestamptz, because the other
way leaves you open to serious confusion about what the time value
really means.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Tue Aug 17 03:24:15 2004
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Date: Tue, 17 Aug 2004 18:26:15 +1200
From: Mark Kirkwood 
Subject: Re: Strange problems with more memory.
In-reply-to: <20040816182314.24818138@svb.ucs.co.za>
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Cc: pgsql-performance@postgresql.org
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If your nightly process is heavily read-only, then raid5 is probably 
fine. If however, there is a significant write component then it would 
perhaps be worth getting another disk and converting to raid10 
(alternatively - see previous postings about raid cards with on-board 
cache). Are you seeing a lot of write activity?

Note that it is possible for a SELECT only workload to generate 
significant write activity - if the resulting datasets are too large for 
memory sorting or hashing. I'm *guessing* that with an 11G database and 
1G (or was that 2G?) of ram that it is possible to overflow whatever 
your sort_mem is set to.


cheers

Mark

Stef wrote:

>Got 3 10000 rpm SCSI raid5 on here. I doubt I will get much better than that
>without losing both arms and legs... 
>
>  
>

From pgsql-performance-owner@postgresql.org  Tue Aug 17 10:30:36 2004
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From: "olivier HARO" 
To: 
Subject: General performance problem!
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Hello,

I have a dedicated server for my posgresql database :

P4 2.4 GHZ
HDD IDE 7200 rpm
512 DDR 2700

I have a problem whith one table of my database :

CREATE SEQUENCE "base_aveugle_seq" START 1;
CREATE TABLE "base_aveugle" (
 "record_id" integer DEFAULT nextval('"base_aveugle_seq"'::text) NOT NULL,
 "dunsnumber" integer NOT NULL,
 "cp" text NOT NULL,
 "tel" text NOT NULL,
 "fax" text NOT NULL,
 "naf" text NOT NULL,
 "siege/ets" text NOT NULL,
 "effectif" integer NOT NULL,
 "ca" integer NOT NULL,
 Constraint "base_aveugle_pkey" Primary Key ("record_id")
);
CREATE INDEX base_aveugle_dunsnumber_key ON base_aveugle USING btree (dunsn=
umber);
CREATE INDEX base_aveugle_cp_key ON base_aveugle USING btree (cp);
CREATE INDEX base_aveugle_naf_key ON base_aveugle USING btree (naf);
CREATE INDEX base_aveugle_effectif_key ON base_aveugle USING btree (effecti=
f);


This table contains 5 000 000 records

I have a PHP application which often makes queries on this table (especiall=
y on the "cp","naf","effectif" fields)

Querries are like :
      select (distint cp) from base_aveugle where cp=3D'201A' and effectif =
between 1 and 150
      select (*) from base_aveugle where naf in ('721A','213F','421K') and =
cp in ('54210','21459','201A') and effectif < 150

I think it is possible to optimize the performance of this queries before c=
hanging the hardware (I now I will...) but I don't know how, even after hav=
ing read lot of things about postgresql ...

Thanks ;)=20


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Hello,


 


I have a dedicated serve=
r for my=20
posgresql database :


 


P4 2.4 GHZ


HDD IDE 7200 rpm<=
/DIV>

512 DDR 2700


 


I have a problem whith o=
ne table of=20
my database :


 


CREATE SEQUENCE "base_aveugle_seq" START=
=20
1;
CREATE TABLE "base_aveugle" (
 "record_id" integer DEFAULT=20
nextval('"base_aveugle_seq"'::text) NOT NULL,
 "dunsnumber" integer=
 NOT=20
NULL,
 "cp" text NOT NULL,
 "tel" text NOT NULL,
 "=
fax"=20
text NOT NULL,
 "naf" text NOT NULL,
 "siege/ets" text NOT=
=20
NULL,
 "effectif" integer NOT NULL,
 "ca" integer NOT=20
NULL,
 Constraint "base_aveugle_pkey" Primary Key=20
("record_id")
);
CREATE INDEX base_aveugle_dunsnumber_key ON base_ave=
ugle=20
USING btree (dunsnumber);
CREATE INDEX base_aveugle_cp_key ON base_aveug=
le=20
USING btree (cp);
CREATE INDEX base_aveugle_naf_key ON base_aveugle USIN=
G=20
btree (naf);
CREATE INDEX base_aveugle_effectif_key ON base_aveugle USIN=
G=20
btree (effectif);


 


 


This table contains 5 00=
0 000=20
records


 


I have a PHP application=
 which=20
often makes queries on this table (especially on the "cp","naf","effectif"=
=20
fields)


 


Querries are like :


    =
 =20
select (distint cp) from base_aveugle where cp=3D'201A' and effectif betwee=
n 1 and=20
150


    =
 =20
select (*) from base_aveugle where naf in ('721A','213F','421K') and cp in=
=20
('54210','21459','201A') and effectif < 150


 


I think it is possible t=
o optimize=20
the performance of this queries before changing the hardware (I now I=
=20
will...) but I don't know how, even after having read lot of things about=
=20
postgresql ...


 


Thanks ;) 

 



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From pgsql-performance-owner@postgresql.org  Tue Aug 17 11:12:34 2004
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	for pgsql-performance@postgresql.org; Tue, 17 Aug 2004 13:48:26 GMT
From: Gaetano Mendola 
X-Newsgroups: comp.databases.postgresql.performance
Subject: Re: General performance problem!
Date: Tue, 17 Aug 2004 15:48:29 +0200
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olivier HARO wrote:

> Hello,
>  
> I have a dedicated server for my posgresql database :
>  
> P4 2.4 GHZ
> HDD IDE 7200 rpm
> 512 DDR 2700
>  
> I have a problem whith one table of my database :
>  
> CREATE SEQUENCE "base_aveugle_seq" START 1;
> CREATE TABLE "base_aveugle" (
>  "record_id" integer DEFAULT nextval('"base_aveugle_seq"'::text) NOT NULL,
>  "dunsnumber" integer NOT NULL,
>  "cp" text NOT NULL,
>  "tel" text NOT NULL,
>  "fax" text NOT NULL,
>  "naf" text NOT NULL,
>  "siege/ets" text NOT NULL,
>  "effectif" integer NOT NULL,
>  "ca" integer NOT NULL,
>  Constraint "base_aveugle_pkey" Primary Key ("record_id")
> );
> CREATE INDEX base_aveugle_dunsnumber_key ON base_aveugle USING btree 
> (dunsnumber);
> CREATE INDEX base_aveugle_cp_key ON base_aveugle USING btree (cp);
> CREATE INDEX base_aveugle_naf_key ON base_aveugle USING btree (naf);
> CREATE INDEX base_aveugle_effectif_key ON base_aveugle USING btree 
> (effectif);
>  
>  
> This table contains 5 000 000 records
>  
> I have a PHP application which often makes queries on this table 
> (especially on the "cp","naf","effectif" fields)
>  
> Querries are like :
>       select (distint cp) from base_aveugle where cp='201A' and effectif 
> between 1 and 150
>       select (*) from base_aveugle where naf in ('721A','213F','421K') 
> and cp in ('54210','21459','201A') and effectif < 150
>  
> I think it is possible to optimize the performance of this queries 
> before changing the hardware (I now I will...) but I don't know how, 
> even after having read lot of things about postgresql ...

Show us a explain analyze for that queries.


Regards
Gaetano Mendola










From pgsql-performance-owner@postgresql.org  Tue Aug 17 10:57:39 2004
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Subject: Re: General performance problem!
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Thread-Topic: [PERFORM] General performance problem!
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From: "Leeuw van der, Tim" 
To: "olivier HARO" , 
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Hi,
=20
Make multi-column indexes, using the columns from your most typical queries=
, putting the most selective columns first (ie; you don't need to make inde=
xes with columns in the same order as they are used in the query).
=20
For instance, an index on cp, effectif could likely benefit both queries; s=
ame for an index on cp, effectif, naf. (You'd need only one of these indexe=
s I think, not both. Experiment to find out which one gives you most benefi=
t in your queries, vs. the slowdown in inserts).
Perhaps some of the single-column keys can be dropped.
=20

-----Original Message-----
From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owne=
r@postgresql.org]On Behalf Of olivier HARO
Sent: dinsdag 17 augustus 2004 15:30
To: pgsql-performance@postgresql.org
Subject: [PERFORM] General performance problem!


Hello,
=20
I have a dedicated server for my posgresql database :
=20
P4 2.4 GHZ
HDD IDE 7200 rpm
512 DDR 2700
=20
I have a problem whith one table of my database :
=20
CREATE SEQUENCE "base_aveugle_seq" START 1;
CREATE TABLE "base_aveugle" (
 "record_id" integer DEFAULT nextval('"base_aveugle_seq"'::text) NOT NULL,
 "dunsnumber" integer NOT NULL,
 "cp" text NOT NULL,
 "tel" text NOT NULL,
 "fax" text NOT NULL,
 "naf" text NOT NULL,
 "siege/ets" text NOT NULL,
 "effectif" integer NOT NULL,
 "ca" integer NOT NULL,
 Constraint "base_aveugle_pkey" Primary Key ("record_id")
);
CREATE INDEX base_aveugle_dunsnumber_key ON base_aveugle USING btree (dunsn=
umber);
CREATE INDEX base_aveugle_cp_key ON base_aveugle USING btree (cp);
CREATE INDEX base_aveugle_naf_key ON base_aveugle USING btree (naf);
CREATE INDEX base_aveugle_effectif_key ON base_aveugle USING btree (effecti=
f);
=20
=20
This table contains 5 000 000 records
=20
I have a PHP application which often makes queries on this table (especiall=
y on the "cp","naf","effectif" fields)
=20
Querries are like :
      select (distint cp) from base_aveugle where cp=3D'201A' and effectif =
between 1 and 150
      select (*) from base_aveugle where naf in ('721A','213F','421K') and =
cp in ('54210','21459','201A') and effectif < 150
=20
I think it is possible to optimize the performance of this queries before c=
hanging the hardware (I now I will...) but I don't know how, even after hav=
ing read lot of things about postgresql ...
=20
Thanks ;)=20
=20

---
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Hi,


 


Make=20
multi-column indexes, using the columns from your most typical queries, put=
ting=20
the most selective columns first (ie; you don't need to make indexes with=
=20
columns in the same order as they are used in the query).

 


For=20
instance, an index on cp, effectif could likely benefit both queries; same =
for=20
an index on cp, effectif, naf. (You'd need only one of these indexes I thin=
k,=20
not both. Experiment to find out which one gives you most benefit in your=
=20
queries, vs. the slowdown in inserts).


Perhaps some of the single-column keys can be=20
dropped.


 



  
-----Original Message-----
From:=20
  pgsql-performance-owner@postgresql.org=20
  [mailto:pgsql-performance-owner@postgresql.org]On Behalf Of olivie=
r=20
  HARO
Sent: dinsdag 17 augustus 2004 15:30
To:=20
  pgsql-performance@postgresql.org
Subject: [PERFORM] General=20
  performance problem!


  
Hello,

  
 

  
I have a dedicated ser=
ver for my=20
  posgresql database :

  
 

  
P4 2.4 GHZ

  
HDD IDE 7200 rpm

  
512 DDR 2700
  
 

  
I have a problem whith=
 one table=20
  of my database :

  
 

  
CREATE SEQUENCE "base_aveugle_seq" STA=
RT=20
  1;
CREATE TABLE "base_aveugle" (
 "record_id" integer DEFAULT=
=20
  nextval('"base_aveugle_seq"'::text) NOT NULL,
 "dunsnumber" integ=
er=20
  NOT NULL,
 "cp" text NOT NULL,
 "tel" text NOT=20
  NULL,
 "fax" text NOT NULL,
 "naf" text NOT=20
  NULL,
 "siege/ets" text NOT NULL,
 "effectif" integer NOT=
=20
  NULL,
 "ca" integer NOT NULL,
 Constraint "base_aveugle_p=
key"=20
  Primary Key ("record_id")
);
CREATE INDEX base_aveugle_dunsnumber_k=
ey ON=20
  base_aveugle USING btree (dunsnumber);
CREATE INDEX base_aveugle_cp_ke=
y ON=20
  base_aveugle USING btree (cp);
CREATE INDEX base_aveugle_naf_key ON=20
  base_aveugle USING btree (naf);
CREATE INDEX base_aveugle_effectif_key=
 ON=20
  base_aveugle USING btree (effectif);

  
 

  
 

  
This table contains 5 =
000 000=20
  records

  
 

  
I have a PHP applicati=
on which=20
  often makes queries on this table (especially on the "cp","naf","effectif=
"=20
  fields)

  
 

  
Querries are like :

  
   &nbs=
p; =20
  select (distint cp) from base_aveugle where cp=3D'201A' and effectif betw=
een 1=20
  and 150

  
   &nbs=
p; =20
  select (*) from base_aveugle where naf in ('721A','213F','421K') and cp i=
n=20
  ('54210','21459','201A') and effectif < 150

  
 

  
I think it is possible=
 to=20
  optimize the performance of this queries before changing the hardwar=
e (I=20
  now I will...) but I don't know how, even after having read lot of things=
=20
  about postgresql ...

  
 

  
Thanks ;) =


  
 

  

---
Outgoing ma=
il is=20
  certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: =
6.0.737=20
  / Virus Database: 491 - Release Date:=20
11/08/2004


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From pgsql-performance-owner@postgresql.org  Tue Aug 17 11:16:17 2004
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From: Richard Huxton 
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To: olivier HARO 
Cc: pgsql-performance@postgresql.org
Subject: Re: General performance problem!
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olivier HARO wrote:
> This table contains 5 000 000 records
> 
> I have a PHP application which often makes queries on this table (especially on the "cp","naf","effectif" fields)
> 
> Querries are like :
>       select (distint cp) from base_aveugle where cp='201A' and effectif between 1 and 150
>       select (*) from base_aveugle where naf in ('721A','213F','421K') and cp in ('54210','21459','201A') and effectif < 150

We'll need to know what version of PostgreSQL you're using and also what 
the output of EXPLAIN ANALYZE shows for your example queries.

-- 
   Richard Huxton
   Archonet Ltd

From pgsql-performance-owner@postgresql.org  Wed Aug 18 12:52:44 2004
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Subject: I could not get postgres to utilizy indexes
Date: Tue, 17 Aug 2004 10:22:59 -0400
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Hi verybody!

I can't make use of indexes even I tried the same test by changing different settings in postgres.conf like geqo to off/on & geqo related parameters, enable_seqscan off/on & so on. Result is the same. 

Here is test itself:

I've created simplest table test and executed the same statement "explain analyze select id from test where id = 50000;" Few times I added 100,000 records, applied vacuum full; and issued above explain command. 
Postgres uses sequential scan instead of index one. 
Of cause Time to execute the same statement constantly grows. In my mind index should not allow time to grow so much.  

Why Postgres does not utilizes primary unique index?
What I'm missing? It continue growing even there are 1,200,000 records. It should at least start using index at some point.


Details are below:
100,000 records:
QUERY PLAN
----------------------------------------------------------------------------------------------------
 Seq Scan on test  (cost=0.00..2427.00 rows=2 width=8) (actual time=99.626..199.835 rows=1 loops=1)
   Filter: (id = 50000)
 Total runtime: 199.990 ms

200,000 records:
QUERY PLAN
-----------------------------------------------------------------------------------------------------
 Seq Scan on test  (cost=0.00..4853.00 rows=2 width=8) (actual time=100.389..402.770 rows=1 loops=1)
   Filter: (id = 50000)
 Total runtime: 402.926 ms


300,000 records:
QUERY PLAN
-----------------------------------------------------------------------------------------------------
 Seq Scan on test  (cost=0.00..7280.00 rows=1 width=8) (actual time=100.563..616.064 rows=1 loops=1)
   Filter: (id = 50000)
 Total runtime: 616.224 ms
(3 rows)

I've created test table by script:

CREATE TABLE test
(
  id int8 NOT NULL DEFAULT nextval('next_id_seq'::text) INIQUE,
  description char(50),
  CONSTRAINT users_pkey PRIMARY KEY (id)
);

CREATE SEQUENCE next_id_seq
  INCREMENT 1
  MINVALUE 1
  MAXVALUE 10000000000
  START 1
  CACHE 5
  CYCLE;

I use postgres 7.4.2




From pgsql-performance-owner@postgresql.org  Tue Aug 17 12:35:58 2004
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From: Artimenko Igor 
Subject: Postgres does not utilize indexes. Why?
To: pgsql-performance@postgresql.org
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Hi everybody!

I can�t make use of indexes even I tried the same test by changing different settings in
postgres.conf like geqo to off/on & geqo related parameters, enable_seqscan off/on & so on. Result
is the same. 

Here is test itself:

I�ve created simplest table test and executed the same statement �explain analyze select id from
test where id = 50000;� Few times I added 100,000 records, applied vacuum full; and issued above
explain command. 
Postgres uses sequential scan instead of index one. 
Of cause Time to execute the same statement constantly grows. In my mind index should not allow
time to grow so much.  

Why Postgres does not utilizes primary unique index?
What I�m missing? It continue growing even there are 1,200,000 records. It should at least start
using index at some point.


Details are below:
100,000 records:
QUERY PLAN
----------------------------------------------------------------------------------------------------
 Seq Scan on test  (cost=0.00..2427.00 rows=2 width=8) (actual time=99.626..199.835 rows=1
loops=1)
   Filter: (id = 50000)
 Total runtime: 199.990 ms

200,000 records:
QUERY PLAN
-----------------------------------------------------------------------------------------------------
 Seq Scan on test  (cost=0.00..4853.00 rows=2 width=8) (actual time=100.389..402.770 rows=1
loops=1)
   Filter: (id = 50000)
 Total runtime: 402.926 ms


300,000 records:
QUERY PLAN
-----------------------------------------------------------------------------------------------------
 Seq Scan on test  (cost=0.00..7280.00 rows=1 width=8) (actual time=100.563..616.064 rows=1
loops=1)
   Filter: (id = 50000)
 Total runtime: 616.224 ms
(3 rows)

I've created test table by script:

CREATE TABLE test
(
  id int8 NOT NULL DEFAULT nextval('next_id_seq'::text) INIQUE,
  description char(50),
  CONSTRAINT users_pkey PRIMARY KEY (id)
);

CREATE SEQUENCE next_id_seq
  INCREMENT 1
  MINVALUE 1
  MAXVALUE 10000000000
  START 1
  CACHE 5
  CYCLE;

I use postgres 7.4.2






=====
Thanks a lot
Igor Artimenko
I specialize in 
Java, J2EE, Unix, Linux, HP, AIX, Solaris, Progress, Oracle, DB2, Postgres, Data Modeling


		
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From pgsql-performance-owner@postgresql.org  Tue Aug 17 12:41:42 2004
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From: "olivier HARO" 
To: 
Subject: Re: General performance problem!
Date: Tue, 17 Aug 2004 17:41:41 +0200
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Thanks for the tip for the index on multiple columns !  (I never do inserts
on this table so insert time doesn't matter)

Mys posgresql version is : PostgreSQL 7.2.1

Here are the results of the EXPLAIN ANALYZE you asked me to execute.


explain analyse select cp from base_aveugle where cp='69740' and effectif
between 1 and 50;
   NOTICE:  QUERY PLAN:
      Index Scan using base_aveugle_cp_eff on base_aveugle
(cost=0.00..508.69 rows=126 width=32)
      (actual time=0.27..11.56 rows=398 loops=1)
      Total runtime: 11.77 msec
   EXPLAIN

explain analyse select cp from base_aveugle where cp like '69%' and effectif
between 1 and 50 and naf like '24%' or naf like '25%';
   NOTICE:  QUERY PLAN:
   Index Scan using base_aveugle_cp_eff_naf, base_aveugle_naf on
base_aveugle  (cost=0.00..100001.89 rows=25245 width=32)
   (actual time=4.40..353.69 rows=6905 loops=1)
   Total runtime: 355.82 msec
   EXPLAIN


thx ;)


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From pgsql-performance-owner@postgresql.org  Tue Aug 17 12:45:23 2004
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Date: Tue, 17 Aug 2004 17:45:34 +0200
From: Michal Taborsky 
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To: Artimenko Igor 
Cc: pgsql-performance@postgresql.org
Subject: Re: Postgres does not utilize indexes. Why?
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Artimenko Igor wrote:
>   id int8 NOT NULL DEFAULT nextval('next_id_seq'::text) INIQUE,

ID column is bigint, but '50000' is int, therefore the index does not 
match. You need to cast your clause like this:

select id from test where id = 50000::int8

Also, issue VACUUM ANALYZE, so Postgres knows about the structure of the 
data.

-- 
Michal Taborsky
http://www.taborsky.cz


From pgsql-performance-owner@postgresql.org  Tue Aug 17 13:59:16 2004
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From: Duane Lee - EGOVX 
To: "'olivier HARO'" , pgsql-performance@postgresql.org
Subject: Re: General performance problem!
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An index on cp and effectif would help your first query.  An index on naf,
cp and effectif would help your second query.
 
Something like this:
 
CREATE INDEX base_aveugle_cp_key2 ON base_aveugle USING btree (cp,
effectif);
CREATE INDEX base_aveugle_naf_key2 ON base_aveugle USING btree (naf, cp,
effectif);
 
Another thing, why include "distinct cp" when you are only selecting
"cp='201A'"?  You will only retrieve one record regardless of how many may
contain cp='201A'.
 
If you could make these UNIQUE indexes that would help also but it's not a
requirement.
 
Good luck,
Duane
 
 
-----Original Message-----
From: olivier HARO [mailto:o.haro@en-compro.com]
Sent: Tuesday, August 17, 2004 6:30 AM
To: pgsql-performance@postgresql.org
Subject: [PERFORM] General performance problem!
 
Hello,
 
I have a dedicated server for my posgresql database :
 
P4 2.4 GHZ
HDD IDE 7200 rpm
512 DDR 2700
 
I have a problem whith one table of my database :
 
CREATE SEQUENCE "base_aveugle_seq" START 1;
CREATE TABLE "base_aveugle" (
 "record_id" integer DEFAULT nextval('"base_aveugle_seq"'::text) NOT NULL,
 "dunsnumber" integer NOT NULL,
 "cp" text NOT NULL,
 "tel" text NOT NULL,
 "fax" text NOT NULL,
 "naf" text NOT NULL,
 "siege/ets" text NOT NULL,
 "effectif" integer NOT NULL,
 "ca" integer NOT NULL,
 Constraint "base_aveugle_pkey" Primary Key ("record_id")
);
CREATE INDEX base_aveugle_dunsnumber_key ON base_aveugle USING btree
(dunsnumber);
CREATE INDEX base_aveugle_cp_key ON base_aveugle USING btree (cp);
CREATE INDEX base_aveugle_naf_key ON base_aveugle USING btree (naf);
CREATE INDEX base_aveugle_effectif_key ON base_aveugle USING btree
(effectif);
 
 
This table contains 5 000 000 records
 
I have a PHP application which often makes queries on this table (especially
on the "cp","naf","effectif" fields)
 
Querries are like :
      select (distint cp) from base_aveugle where cp='201A' and effectif
between 1 and 150
      select (*) from base_aveugle where naf in ('721A','213F','421K') and
cp in ('54210','21459','201A') and effectif < 150
 
I think it is possible to optimize the performance of this queries before
changing the hardware (I now I will...) but I don't know how, even after
having read lot of things about postgresql ...
 
Thanks ;) 
 

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  An index on naf, cp and effectif would help your second
query.



 



Some=
thing
like this:



 



CREATE INDEX base_aveugle_cp_key2 ON
base_aveugle USING btree (cp, effectif);

CREATE INDEX base_aveugle_naf_key2 ON base_aveugle USING btree (naf, cp,
effectif);



 



<=
span
style=3D'font-size:12.0pt;color:navy'>Another thing, why include “dis=
tinct cp”
when you are only selecting “cp=3D’201A’”? 
You will only retrieve one record regardless of how many may contain=
 cp=3D’201A’.



<=
span
style=3D'font-size:12.0pt;color:navy'> 



<=
span
style=3D'font-size:12.0pt;color:navy'>If you could make these UNIQUE indexe=
s that
would help also but it’s not a requirement.



 



Good=
 luck,



Duan=
e



 



 



-----Original
Message-----

From: olivier HARO
[mailto:o.haro@en-compro.com]

Sent: Tuesday, August 17, 20=
04
6:30 AM

To:
pgsql-performance@postgresql.org

Subject: [PERFORM] General
performance problem!



 <=
/o:p>



Hello,



 =
;



I
have a dedicated server for my posgresql database :



 =
;



P4
2.4 GHZ



HDD
IDE 7200 rpm



512
DDR 2700



 =
;



I
have a problem whith one table of my database :



 =
;



CREATE
SEQUENCE "base_aveugle_seq" START 1;

CREATE TABLE "base_aveugle" (

 "record_id" integer DEFAULT
nextval('"base_aveugle_seq"'::text) NOT NULL,

 "dunsnumber" integer NOT NULL,

 "cp" text NOT NULL,

 "tel" text NOT NULL,

 "fax" text NOT NULL,

 "naf" text NOT NULL,

 "siege/ets" text NOT NULL,

 "effectif" integer NOT NULL,

 "ca" integer NOT NULL,

 Constraint "base_aveugle_pkey" Primary Key
("record_id")

);

CREATE INDEX base_aveugle_dunsnumber_key ON base_aveugle USING btree
(dunsnumber);

CREATE INDEX base_aveugle_cp_key ON base_aveugle USING btree (cp);

CREATE INDEX base_aveugle_naf_key ON base_aveugle USING btree (naf);

CREATE INDEX base_aveugle_effectif_key ON base_aveugle USING btree (effecti=
f);



 =
;



 =
;



This
table contains 5 000 000 records



 =
;



I
have a PHP application which often makes queries on this table (especially =
on
the "cp","naf","effectif" fields)



 =
;



Querries
are like :



     
select (distint cp) from base_aveugle where cp=3D'201A' and effectif betwee=
n 1
and 150



     
select (*) from base_aveugle where naf in ('721A','213F','421K') and cp in
('54210','21459','201A') and effectif < 150



 =
;



I
think it is possible to optimize the performance of this queries before
changing the hardware (I now I will...) but I don't know how, even aft=
er
having read lot of things about postgresql ...



 =
;



Thanks
;) 



 =
;





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From pgsql-performance-owner@postgresql.org  Tue Aug 17 15:32:48 2004
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	pgsql-performance@postgresql.org
Subject: Re: Postgres does not utilize indexes. Why?
References: <20040817153555.85408.qmail@web11901.mail.yahoo.com>
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> test where id = 50000;” Few times I added 100,000 records, applied

	cast the 50000 to int8 and it will use the index

From pgsql-performance-owner@postgresql.org  Tue Aug 17 17:03:06 2004
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From: Joe Lester 
Subject: Re: shared_buffers Question
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I'm doing a nightly vacuum... so I don't think that's it, although 
should I be doing a FULL vacuum instead? The size of my data directory 
is only about 389 MB. I'll take a closer look at file sizes going 
forward.

echo "VACUUM ANALYZE VERBOSE;" | /Library/PostgreSQL/bin/psql -U 
postgres officelink 2>> vacuum.log

Thanks.


From: "Scott Marlowe"
Your shared buffers are almost certainly not the problem here. 2000
shared buffers is only 16 Megs of ram, max.  More than likely, the
database filled up the data directory / partition because it wasn't
being vacuumed.

On Sat, 2004-07-31 at 10:25, Joe Lester wrote:
 > I've been running a postgres server on a Mac (10.3, 512MB RAM) with 
200
 > clients connecting for about 2 months without a crash. However just
 > yesterday the database and all the clients hung. When I looked at the
 > Mac I'm using as the postgres server it had a window up that said that
 > there was no more disk space available to write memory too. I ended up
 > having to restart the whole machine. I would like to configure 
postgres
 > so that is does not rely so heavily on disk-based memory but, rather,
 > tries to stay within the scope of the 512MB of physical memory in the
 > Mac.





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I'm doing a nightly vacuum... so I don't think that's it, although
should I be doing a FULL vacuum instead? The size of my data directory
is only about 389 MB. I'll take a closer look at file sizes going
forward.


echo "VACUUM ANALYZE VERBOSE;" | /Library/PostgreSQL/bin/psql -U
postgres officelink 2>> vacuum.log


Thanks.



Lucida GrandeFromLucida Grande:
"Scott Marlowe"Courier

Your shared buffers are almost certainly not the problem here. 2000

shared buffers is only 16 Megs of ram, max.  More than likely, the

database filled up the data directory / partition because it wasn't

being vacuumed.



CourierOn Sat, 2004-07-31 at 10:25, Joe
Lester wrote:

> I've been running a postgres server on a Mac (10.3, 512MB RAM) with
200 

> clients connecting for about 2 months without a crash. However just 

> yesterday the database and all the clients hung. When I looked at
the 

> Mac I'm using as the postgres server it had a window up that said
that 

> there was no more disk space available to write memory too. I ended
up 

> having to restart the whole machine. I would like to configure
postgres 

> so that is does not rely so heavily on disk-based memory but,
rather, 

> tries to stay within the scope of the 512MB of physical memory in
the 

> Mac.






--Apple-Mail-20-649135890--



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From: Frank van Vugt 
Organization: Foxi Consultants in Technology BV
To: pgsql-performance@postgresql.org
Subject: Why is the number of dead tuples causing the performance of deferred
	triggers to degrading so rapidly (exponentionally)?
Date: Tue, 17 Aug 2004 23:29:52 +0200
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Hi,

I'm seeing the following behaviour with the table and functions given below:

db=# insert into f select * from full_sequence(1, 1000);
INSERT 0 1000
Time: 197,507 ms
db=# insert into f select * from full_sequence(1, 1000);
INSERT 0 1000
Time: 341,880 ms
db=# insert into f select * from full_sequence(1, 1000);
INSERT 0 1000
Time: 692,603 ms
db=# insert into f select * from full_sequence(1, 1000);
INSERT 0 1000
Time: 985,253 ms
db=# insert into f select * from full_sequence(1, 1000);
INSERT 0 1000
Time: 1241,334 ms

Or even worse (fresh drop/create of the table and functions):

db=# insert into f select id from full_sequence(1, 10000);
INSERT 0 10000
Time: 22255,767 ms
db=# insert into f select id from full_sequence(1, 10000);
INSERT 0 10000
Time: 45398,433 ms
db=# insert into f select id from full_sequence(1, 10000);
INSERT 0 10000
Time: 67993,476 ms

Wrapping the commands in a transaction only accumulates the penalty at commit.

It seems in this case the time needed for a single deferred trigger somehow 
depends on the number of dead tuples in the table, because a vacuum of the 
table will 'reset' the query-times. However, even if I wanted to, vacuum is 
not allowed from within a function.

What is happening here? And more importantly, what can I do to prevent this?

NB. My real-world application 'collects' id's in need for deferred work, but 
this work is both costly and only needed once per base record. So I use an 
'update' table whose content I join with the actual tables in order to do the 
work for _all_ the base records involved upon the first execution of the 
deferred trigger. At the end of the trigger, this 'update' table is emptied 
so any additional deferred triggers on the same table will hardly lose any 
time. Or at least, that was the intention....

*********** demo script ***********
drop table f cascade;
drop function tr_f_def() cascade;
drop function full_sequence(integer, integer);
drop type full_sequence_type;

create table f (id int);
create function tr_f_def() RETURNS trigger LANGUAGE 'plpgsql' STABLE STRICT
SECURITY INVOKER AS '
        DECLARE
        BEGIN
		-- do stuff with all the ids in the table

		-- delete the contents
--		delete from f;
		IF EXISTS (SELECT 1 FROM f) THEN
			DELETE FROM F;
			VACUUM F;
		END IF;

                RETURN NULL;
        END;';
create type full_sequence_type as (id int);
create function full_sequence(integer, integer)
	RETURNS SETOF full_sequence_type
	LANGUAGE 'plpgsql'
	IMMUTABLE
	STRICT
	SECURITY INVOKER
	AS '	DECLARE
			my_from ALIAS FOR $1;
			my_to ALIAS FOR $2;
			result full_sequence_type%ROWTYPE;
		BEGIN
			-- just loop
			FOR i IN my_from..my_to LOOP
				result.id = i;
				RETURN NEXT result;
			END LOOP;

			-- finish
			RETURN;
		END;';
CREATE CONSTRAINT TRIGGER f_def AFTER INSERT ON f DEFERRABLE INITIALLY 
DEFERRED FOR EACH ROW EXECUTE PROCEDURE tr_f_def();
*********** demo script ***********

db=# select version();
                               version
---------------------------------------------------------------------
 PostgreSQL 7.4.3 on i686-pc-linux-gnu, compiled by GCC egcs-2.91.66





-- 
Best,




Frank.


From pgsql-performance-owner@postgresql.org  Tue Aug 17 18:34:02 2004
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From: Frank van Vugt 
Organization: Foxi Consultants in Technology BV
Subject: Why is the number of dead tuples causing the performance of deferred
	triggers to degrading so rapidly (exponentionally)?
Date: Tue, 17 Aug 2004 23:33:42 +0200
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Obviously,

this part of tr_f_def():

******************************
		-- delete the contents
--		delete from f;
		IF EXISTS (SELECT 1 FROM f) THEN
			DELETE FROM F;
			VACUUM F;
		END IF;
******************************


should simply read:

******************************
		-- delete the contents
		delete from f;
******************************



--
Best,




Frank.


From pgsql-performance-owner@postgresql.org  Tue Aug 17 20:03:38 2004
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From: Josh Berkus 
Reply-To: josh@agliodbs.com
Organization: Aglio Database Solutions
To: Frank van Vugt 
Subject: Re: Why is the number of dead tuples causing the performance of
	deferred triggers to degrading so rapidly (exponentionally)?
Date: Tue, 17 Aug 2004 16:03:43 -0700
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Frank,

> It seems in this case the time needed for a single deferred trigger somehow
> depends on the number of dead tuples in the table, because a vacuum of the
> table will 'reset' the query-times. However, even if I wanted to, vacuum is
> not allowed from within a function.
>
> What is happening here? And more importantly, what can I do to prevent
> this?

I'm not clear on all of the work you're doing in the trigger.  However, it 
seems obvious that you're deleting and/or updating a large number of rows.  
The escalating execution times would be consistent with that.

> NB. My real-world application 'collects' id's in need for deferred work,
> but this work is both costly and only needed once per base record. So I use
> an 'update' table whose content I join with the actual tables in order to
> do the work for _all_ the base records involved upon the first execution of
> the deferred trigger. At the end of the trigger, this 'update' table is
> emptied so any additional deferred triggers on the same table will hardly
> lose any time. Or at least, that was the intention....

I think you're doing a lot more than is wise to do in triggers.   Deferrable 
triggers aren't really intended for running long procedures with the creation 
of types and temporary tables (your post got a bit garbled, so pardon me if 
I'm misreading it).   I'd suggest reconsidering your approach to this 
application problem.

At the very least, increase max_fsm_relations to some high value, which may 
help (or not). 

-Josh

-- 
__Aglio Database Solutions_______________
Josh Berkus		       Consultant
josh@agliodbs.com	 www.agliodbs.com
Ph: 415-752-2500	Fax: 415-752-2387
2166 Hayes Suite 200	San Francisco, CA

From pgsql-performance-owner@postgresql.org  Tue Aug 17 21:44:41 2004
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	Tue, 17 Aug 2004 17:44:38 PDT
Date: Tue, 17 Aug 2004 17:44:38 -0700 (PDT)
From: my thi ho 
Subject: postgresql performance with multimedia
To: pgsql-performance@postgresql.org
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Hi,
I am working on a project which explore postgresql to
store multimedia data.
In details,  i am trying to work with the buffer
management part of postgres source code. And try to
improve the performance. I had search on the web but
could not find much usefull information. 
It would be great if anyone knows any developer groups
that working on similar things ? or where can i find
more information on this issue?
Thank you very much for your help
regards,
MT Ho


		
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From pgsql-performance-owner@postgresql.org  Wed Aug 18 05:18:29 2004
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Date: Wed, 18 Aug 2004 10:18:19 +0200
From: eleven 
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Subject: high load caused by I/O - a hint
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Hello,

This is not strictly PostgreSQL performance hint, but may be
helpful to someone with problems like mine.

As I earlier posted, I was experiencing very high load average
on one of my Linux database servers (IBM eServer 345, SCSI disks on LSI 
Logic controller) caused by I/O bottleneck.

INSERTs were really slow, even after many days of
tweaking PostgreSQL configuration. The problem appeared to be
in the Linux kernel itself - using acpi=ht and noapic boot parameters
solved my performance problems. Load average dropped below 1.0
(before, it was as high as ten in peak) and the database
works much, much faster.

-- 
11.

From pgsql-performance-owner@postgresql.org  Wed Aug 18 05:55:50 2004
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Date: Wed, 18 Aug 2004 10:51:54 +0200
From: Grega Bremec 
To: eleven 
Cc: pgsql-performance@postgresql.org
Subject: Re: high load caused by I/O - a hint
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...and on Wed, Aug 18, 2004 at 10:18:19AM +0200, eleven used the keyboard:
> Hello,
>=20
> This is not strictly PostgreSQL performance hint, but may be
> helpful to someone with problems like mine.
>=20
> As I earlier posted, I was experiencing very high load average
> on one of my Linux database servers (IBM eServer 345, SCSI disks on LSI=
=20
> Logic controller) caused by I/O bottleneck.
>=20
> INSERTs were really slow, even after many days of
> tweaking PostgreSQL configuration. The problem appeared to be
> in the Linux kernel itself - using acpi=3Dht and noapic boot parameters
> solved my performance problems. Load average dropped below 1.0
> (before, it was as high as ten in peak) and the database
> works much, much faster.

Hello,

Did you try with acpi=3Dnoidle? This proved to be of help on many an
occasion before, and you don't have to give up any functionality over
it. It's just that the ACPI BIOS is broken and overloads the system
with idle calls.

Other than that, general guidelines would be, don't combine APM and
ACPI, and rather use proper SMP code for hyperthreaded machines than
just the ACPI CPU enumeration feature.

There's also a new option with 2.6.8.1, called CONFIG_SCHED_SMT that
is supposed to handle some cases SMP code had problems with better,
at the cost of slight overhead in other areas.

My advice would be, if you have an option to choose between APM and
ACPI, go for ACPI. It's the future, it's being developed actively,
it does a whole lot more than APM (that was really only about power
management), and last but not least, I've been using it for four
years on over fifty SMP machines and I never ever had a problem
beyond the scope of what noidle could fix (knocks-on-wood). :)

HTH,
--=20
    Grega Bremec
    Senior Administrator
    Noviforum Ltd., Software & Media
    http://www.noviforum.si/

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From pgsql-performance-owner@postgresql.org  Wed Aug 18 06:25:20 2004
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	Wed, 18 Aug 2004 11:24:57 +0200
From: Frank van Vugt 
Organization: Foxi Consultants in Technology BV
To: josh@agliodbs.com
Subject: Re: Why is the number of dead tuples causing the performance of
	deferred triggers to degrade so rapidly (exponentionally)?
Date: Wed, 18 Aug 2004 11:24:56 +0200
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Hi Josh,

> > It seems in this case the time needed for a single deferred trigger
> > somehow depends on the number of dead tuples in the table

After further investigation I think I have a better grasp of what's going on.

The thing biting me here is indeed the 'delete from' on a table with a number 
of dead rows, possibly made worse in some cases where not everything can be 
handled in memory.

> I'm not clear on all of the work you're doing in the trigger.
> > NB. My real-world application 'collects' id's in need for deferred work
> I think you're doing a lot more than is wise to do in triggers.

I probably wasn't clear enough on this. I'm not creating types and/or 
temporary tables or anything of that kind.

The ratio is probably explained better by this example:

- the database has knowledge on 'parts' and 'sets', the sets have a few fields 
whose content depend on the parts, but the proper value for these fields can 
only be determined by looking at all the parts of the particular set together 
(i.e. it's not a plain 'part-count' that one could update by a trigger on the 
part)

- during a transaction, a number of things will happen to various parts of 
various sets, so I have after triggers on the parts that will insert the ids 
of the sets that need an update into a set_update holding table; in turn, 
this set_update table has a deferred trigger

- upon execution of the deferred triggers, I now know that all the work on the 
parts is finished, so the deferred trigger initiates an update for the sets 
whose ids are in the update table and it will delete these ids afterwards

Now, because multiple updates to parts of the same set will result in multiple 
inserts in the update table, I want to avoid doing the set-update more that 
once. 

Obviously, it would be better to be able to 'cancel' the rest of the calls to 
the deferred trigger after it has been executed for the first time, but that 
doesn't seem possible.

Even better would be to use a 'for each statement' trigger on the set_update 
holding table instead, but it is not possible to create a deferred 'for each 
statement' trigger..... ;(

So, I seem to be a bit between a rock and a hard place here, I must use 
deferred triggers in order to avoid a costly set update on each part update, 
but in such a deferred trigger I cannot avoid doing the update multiple 
times....(due to the growing cost of a 'delete from' in the trigger)

Mmm, it seems that by hacking pg_trigger I am able to create a for each 
statement trigger that is 'deferrable initially deferred'.

This probably solves my problem, I will ask on 'general' whether this has any 
unforseen side effects and whether or not a 'regular' deferrable for each 
statement trigger is incorporated in v8.0.

Thanks for you reply!



-- 
Best,




Frank.


From pgsql-performance-owner@postgresql.org  Wed Aug 18 08:12:47 2004
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From: Gaetano Mendola 
X-Newsgroups: comp.databases.postgresql.performance
Subject: Re: high load caused by I/O - a hint
Date: Wed, 18 Aug 2004 12:54:35 +0200
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eleven wrote:

> Hello,
> 
> This is not strictly PostgreSQL performance hint, but may be
> helpful to someone with problems like mine.
> 
> As I earlier posted, I was experiencing very high load average
> on one of my Linux database servers (IBM eServer 345, SCSI disks on LSI 
> Logic controller) caused by I/O bottleneck.
> 
> INSERTs were really slow, even after many days of
> tweaking PostgreSQL configuration. The problem appeared to be
> in the Linux kernel itself - using acpi=ht and noapic boot parameters
> solved my performance problems. Load average dropped below 1.0
> (before, it was as high as ten in peak) and the database
> works much, much faster.

I suggest you to investigate why noapic did the work for you, do you have
not well supported device ? At your place also I'd try removing the noapic
option and using acpi=noidle



Regards
Gaetano Mendola



From pgsql-performance-owner@postgresql.org  Wed Aug 18 10:10:20 2004
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From: Jeff 
Subject: Re: high load caused by I/O - a hint
Date: Wed, 18 Aug 2004 09:10:24 -0400
To: eleven 
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On Aug 18, 2004, at 4:18 AM, eleven wrote:

> Hello,
>
> This is not strictly PostgreSQL performance hint, but may be
> helpful to someone with problems like mine.
>
> As I earlier posted, I was experiencing very high load average
> on one of my Linux database servers (IBM eServer 345, SCSI disks on 
> LSI Logic controller) caused by I/O bottleneck.
>

We have some 335's (I think they are 335s) and until April or so there 
was a bug in the Fusion MPT driver that would cause it to revert to 
async narrow mode if hardware RAID was enabled on it.  (Performance was 
horrible - NFS on a 100meg network was 10x faster than local disk!) And 
on the upside, when I originally researched the problem they hadn't 
found the bug yet so there were no others around having issues like 
mine so trying to figure it out was quite difficult.

I may see if using that acpi=ht makes any difference as well.

--
Jeff Trout 
http://www.jefftrout.com/
http://www.stuarthamm.net/


From pgsql-performance-owner@postgresql.org  Wed Aug 18 10:10:37 2004
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Subject: Re: postgresql performance with multimedia
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On 8/17/2004 8:44 PM, my thi ho wrote:

> Hi,
> I am working on a project which explore postgresql to
> store multimedia data.
> In details,  i am trying to work with the buffer
> management part of postgres source code. And try to
> improve the performance. I had search on the web but
> could not find much usefull information. 

What version of PostgreSQL are you looking at? Note that the buffer 
cache replacement strategy was completely changed for version 8.0, which 
is currently in BETA test. A description of the algorithm can be found 
in the README file in src/backend/storage/bufmgr.


Jan

> It would be great if anyone knows any developer groups
> that working on similar things ? or where can i find
> more information on this issue?
> Thank you very much for your help
> regards,
> MT Ho
> 
> 
> 		
> __________________________________
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-- 
#======================================================================#
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#================================================== JanWieck@Yahoo.com #

From pgsql-performance-owner@postgresql.org  Wed Aug 18 12:53:04 2004
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	for pgsql-performance@postgresql.org; Wed, 18 Aug 2004 15:16:37 GMT
From: Raoul Buzziol 
X-Newsgroups: comp.databases.postgresql.performance
Subject: Re: Help specifying new machine
Date: Wed, 18 Aug 2004 17:18:23 +0200
Organization: Hub.Org Networking Services
Lines: 21
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References: <20040809165657.GB15169@campbell-lange.net>
	 
	
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> You're not going to be able to get a Dual Athlon MP for the same price
> as a single Xeon. A few years back, this was the case because Xeon CPUs
> & MBs had a huge premium over Athlon. This is no longer true mainly
> because the number of people carrying Athlon MP motherboards has dropped
> down drastically. Go to pricewatch.com and do a search for 760MPX -- you
> get a mere 8 entries. Not surprisingly because who would not want to
> spend a few pennies more for a much superior Dual Opteron? The few
> sellers you see now just keep stuff in inventory for people who need
> replacement parts for emergencies and are willing to pay up the nose
> because it is an emergency.

I saw pricewatch.com and you're right. 

I looked for some benchmarks, and I would know if I'm right on:
- Dual Opteron 246 have aproximately the same performance of a Dual Xeon 3Gh
(Opteron a little better)
- Opteron system equal or cheeper than Xeon system.

As I'm not a hardware expert I would know if my impressions were right.

Thanx, Raoul

From pgsql-performance-owner@postgresql.org  Wed Aug 18 13:13:04 2004
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Subject: Re: Help specifying new machine
From: Rod Taylor 
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Cc: Postgresql Performance 
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References: <20040809165657.GB15169@campbell-lange.net>
	 
	  
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On Wed, 2004-08-18 at 11:18, Raoul Buzziol wrote:
> > You're not going to be able to get a Dual Athlon MP for the same price
> > as a single Xeon. A few years back, this was the case because Xeon CPUs
> > & MBs had a huge premium over Athlon. This is no longer true mainly
> > because the number of people carrying Athlon MP motherboards has dropped
> > down drastically. Go to pricewatch.com and do a search for 760MPX -- you
> > get a mere 8 entries. Not surprisingly because who would not want to
> > spend a few pennies more for a much superior Dual Opteron? The few
> > sellers you see now just keep stuff in inventory for people who need
> > replacement parts for emergencies and are willing to pay up the nose
> > because it is an emergency.
> 
> I saw pricewatch.com and you're right. 
> 
> I looked for some benchmarks, and I would know if I'm right on:
> - Dual Opteron 246 have aproximately the same performance of a Dual Xeon 3Gh
> (Opteron a little better)
> - Opteron system equal or cheeper than Xeon system.

For PostgreSQL, Opteron might be a touch worse than Xeon for single
processor, little better for Dual, and a whole heck of a bunch better
for Quads -- but this depends on your specific work load as memory
bound, cpu bound, lots of float math, etc. work loads will perform
differently.

In general, an Opteron is a better bet simply because you can shove more
ram onto it (without workarounds), and you can't beat an extra 8GB ram
on an IO bound database (consider your datasize in 1 year).



From pgsql-performance-owner@postgresql.org  Wed Aug 18 14:12:19 2004
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Date: Wed, 18 Aug 2004 12:12:26 -0500
From: Thomas Swan 
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Cc: pgsql-performance@postgresql.org
Subject: Re: I could not get postgres to utilizy indexes
References: <5DEC3FFCDE2F7C4DA45433EE09A4F22C01A3FFCA@colossus.dyadem.corp>
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Igor Artimenko wrote:

>Hi verybody!
>
>I can't make use of indexes even I tried the same test by changing different settings in postgres.conf like geqo to off/on & geqo related parameters, enable_seqscan off/on & so on. Result is the same. 
>
>Here is test itself:
>
>I've created simplest table test and executed the same statement "explain analyze select id from test where id = 50000;" Few times I added 100,000 records, applied vacuum full; and issued above explain command. 
>Postgres uses sequential scan instead of index one. 
>Of cause Time to execute the same statement constantly grows. In my mind index should not allow time to grow so much.  
>
>Why Postgres does not utilizes primary unique index?
>What I'm missing? It continue growing even there are 1,200,000 records. It should at least start using index at some point.
>
>  
>
Igor, you may want to run "vacuum analyze" and see if your results change.

Thomas


From pgsql-performance-owner@postgresql.org  Wed Aug 18 14:24:48 2004
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From: "gnari" 
To: "Thomas Swan" ,
	"Igor Artimenko" 
Cc: 
References: <5DEC3FFCDE2F7C4DA45433EE09A4F22C01A3FFCA@colossus.dyadem.corp>
	<41238DFA.1030207@idigx.com>
Subject: Re: I could not get postgres to utilizy indexes
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"Thomas Swan"  says:


> Igor Artimenko wrote:
>

[ snipped question that was almost exactly a repeat
  of one we saw yesterday ]

> >
> >
> Igor, you may want to run "vacuum analyze" and see if your results change.

Actually, I think it was determined that the problem was due to the
int index

Michal Taborsky suggested this solution:

    select id from test where id = 50000::int8

did this not help ?

gnari




From pgsql-performance-owner@postgresql.org  Wed Aug 18 14:29:21 2004
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From: "gnari" 
To: 
References: <5DEC3FFCDE2F7C4DA45433EE09A4F22C01A3FFCA@colossus.dyadem.corp>
	<41238DFA.1030207@idigx.com>
	<00e801c48548$8d2c0b70$0100000a@wp2000>
Subject: Re: I could not get postgres to utilizy indexes
Date: Wed, 18 Aug 2004 17:31:24 -0000
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I ("gnari" ) miswrote:

> Actually, I think it was determined that the problem was due to the
> int index

of course, i meant int8 index

gnari




From pgsql-performance-owner@postgresql.org  Wed Aug 18 16:39:34 2004
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Hi, 

I noticed an interesting phenomenon when loding (COPY) some tables
from a file.  For some reason, one load was taking longer than I
assumed it would.  As it turns out, one of the columns was an array
containing elements that were of a user defined type.  Using strace
(on linux) and truss (on solaris), most of the time was spent on
stat64() calls on the shared library that contained the in/out
functions for the user defined type.

In a nutshell, it looks like whenever COPY is invoked, and when a user
defined type is used in an array, then stat64() will be called for
each row accessed on the shared library relevant for the user defined
type.

As an example, I created a simple unsigned 2 byte integer type (called
uint2) as follows:
...
typedef uint16 uint2;

PG_FUNCTION_INFO_V1(uint2_in);
Datum
uint2_in (PG_FUNCTION_ARGS)
{
        int val;
        val = atoi(PG_GETARG_CSTRING(0));
        if (val > 65535 || val < 0)
                elog (ERROR, "Value %i is not in range for uint2", val);
        PG_RETURN_INT16((uint2) val);
}

PG_FUNCTION_INFO_V1(uint2_out);
Datum
uint2_out (PG_FUNCTION_ARGS)
{
        uint2 e = (uint2) PG_GETARG_INT16(0);
        char * ret_string = (char *) palloc(9);
                                                                                
        snprintf(ret_string, 9, "%i", (int) e);
        PG_RETURN_CSTRING(ret_string);
}
....
I compiled this, making shared library uint2.so, and in psql created the type.

I then created two test tables: 

CREATE TABLE scratch0 (value uint2);
INSERT INTO scratch0 values('1');
INSERT INTO scratch0 values('2');
INSERT INTO scratch0 values('3');
INSERT INTO scratch0 values('4');
 
CREATE TABLE scratch1 (value uint2[]);
INSERT INTO scratch1 values('{1,2,3}');
INSERT INTO scratch1 values('{10,20,30}');
INSERT INTO scratch1 values('{100,200,300}');
INSERT INTO scratch1 values('{1000,2000,300

Now, I ran strace (and truss) tattached to the postmaster process
looking for stat64, and here's what I found:

------
SELECT * from scratch0 LIMIT 1;
stat64("/pg/lib/postgresql/uint2", 0xFFBFE808) Err#2 ENOENT
stat64("/pg/lib/postgresql/uint2.so", 0xFFBFE808) = 0
 
SELECT * from scratch0 LIMIT 2;
stat64("/pg/lib/postgresql/uint2", 0xFFBFE808) Err#2 ENOENT
stat64("/pg/lib/postgresql/uint2.so", 0xFFBFE808) = 0
 
SELECT * from scratch0 LIMIT 3;
stat64("/pg/lib/postgresql/uint2", 0xFFBFE808) Err#2 ENOENT
stat64("/pg/lib/postgresql/uint2.so", 0xFFBFE808) = 0
------
.
.so each SELECT stats the uint2.so file once, regardless of the number
of fows.  fair enough.  now for the array case:

------
SELECT * from scratch1 LIMIT 1;
stat64("/pg/lib/postgresql/uint2", 0xFFBFE808) Err#2 ENOENT
stat64("/pg/lib/postgresql/uint2.so", 0xFFBFE808) = 0
                                                                                
SELECT * from scratch1 LIMIT 2;
stat64("/pg/lib/postgresql/uint2", 0xFFBFE808) Err#2 ENOENT
stat64("/pg/lib/postgresql/uint2.so", 0xFFBFE808) = 0
stat64("/pg/lib/postgresql/uint2", 0xFFBFE808) Err#2 ENOENT
stat64("/pg/lib/postgresql/uint2.so", 0xFFBFE808) = 0

SELECT * from scratch1 LIMIT 3;
stat64("/pg/lib/postgresql/uint2", 0xFFBFE808) Err#2 ENOENT
stat64("/pg/lib/postgresql/uint2.so", 0xFFBFE808) = 0
stat64("/pg/lib/postgresql/uint2", 0xFFBFE808) Err#2 ENOENT
stat64("/pg/lib/postgresql/uint2.so", 0xFFBFE808) = 0
stat64("/pg/lib/postgresql/uint2", 0xFFBFE808) Err#2 ENOENT
stat64("/pg/lib/postgresql/uint2.so", 0xFFBFE808) = 0
------

..so for *every row* involving an array, a stat64 is called.  This is
true for COPY too.. we were loading 2.5 billion rows, so that's quite
a bit of overhead!  Now, we used strace (on linux) and truss (on
solaris) to see how much this was actually affecting us.:

Output from truss COPYING large file with millions of {1,2,3} unint2 arrays:
syscall               seconds   calls  errors
read                     .055     527
write                   1.507   11358
close                    .000       6
time                     .000       3
getpid                   .000       1
kill                     .000       1
semop                    .002     116
fdsync                   .000       3
llseek                   .081    5042
stat64                 24.205 1078764 539382
open64                   .000       6
                     --------  ------   ----
sys totals:            25.853 1095827 539382
usr time:              21.567
elapsed:              113.310

so in other words, almost 25% of the total time and 50+% of the
execution time time was wasted on stat64.  on Linux, the proportion of
time relative to other calls in strace was similar.

So.. Is this a bug or are the stat64 calls necessary?  I doubt arrays
of user-defined types (in C) are common, and I couldn't find anything
that looked relevent in the lists.

From pgsql-performance-owner@postgresql.org  Wed Aug 18 18:39:21 2004
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To: apb18@cornell.edu
Cc: pgsql-performance@postgresql.org
Subject: Re: Array types and loading 
In-reply-to: <19ab0ccd040818123936c1cdd3@mail.gmail.com> 
References: <19ab0ccd040818123936c1cdd3@mail.gmail.com>
Comments: In-reply-to Aaron Birkland 
	message dated "Wed, 18 Aug 2004 15:39:29 -0400"
Date: Wed, 18 Aug 2004 17:39:21 -0400
Message-ID: <4152.1092865161@sss.pgh.pa.us>
From: Tom Lane 
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Aaron Birkland  writes:
> In a nutshell, it looks like whenever COPY is invoked, and when a user
> defined type is used in an array, then stat64() will be called for
> each row accessed on the shared library relevant for the user defined
> type.

Let me guess ... PG 7.3 or older?

7.4 should avoid the problem because array_in() caches function lookup
information for the element type's input function across multiple calls.

In 8.0 there's also a cache at the fmgr_info() level to eliminate
repeated searches for a dynamically loaded function.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Wed Aug 18 18:47:50 2004
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Date: Wed, 18 Aug 2004 17:47:50 -0400
From: Aaron Birkland 
Reply-To: apb18@cornell.edu
To: Tom Lane 
Subject: Re: Array types and loading
Cc: pgsql-performance@postgresql.org
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You got it.. 7.3 (should have mentioned that).   We're planning to
upgrade to 8.0 anyway in the future, so it's good to know.  Thanks!

   -Aaron

On Wed, 18 Aug 2004 17:39:21 -0400, Tom Lane  wrote:
> Aaron Birkland  writes:
> > In a nutshell, it looks like whenever COPY is invoked, and when a user
> > defined type is used in an array, then stat64() will be called for
> > each row accessed on the shared library relevant for the user defined
> > type.
> 
> Let me guess ... PG 7.3 or older?
> 
> 7.4 should avoid the problem because array_in() caches function lookup
> information for the element type's input function across multiple calls.
> 
> In 8.0 there's also a cache at the fmgr_info() level to eliminate
> repeated searches for a dynamically loaded function.
> 
>                         regards, tom lane
>

From pgsql-performance-owner@postgresql.org  Wed Aug 18 20:03:23 2004
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From: DeJuan Jackson 
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To: Frank van Vugt 
Cc: josh@agliodbs.com, pgsql-performance@postgresql.org
Subject: Re: Why is the number of dead tuples causing the performance
References: <200408172329.52555.ftm.van.vugt@foxi.nl>
	<200408171603.43236.josh@agliodbs.com>
	<200408181124.56823.ftm.van.vugt@foxi.nl>
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Since you are updating all of the sets with the specified part number 
why not just ensure that a transaction never inserts the same part 
number more than once (an INSERT  ...SELECT ... WHERE NOT EXISTS(...) 
comes to mind), then delete the row before the end of transaction.

Frank van Vugt wrote:

>Hi Josh,
>
>  
>
>>>It seems in this case the time needed for a single deferred trigger
>>>somehow depends on the number of dead tuples in the table
>>>      
>>>
>
>After further investigation I think I have a better grasp of what's going on.
>
>The thing biting me here is indeed the 'delete from' on a table with a number 
>of dead rows, possibly made worse in some cases where not everything can be 
>handled in memory.
>
>  
>
>>I'm not clear on all of the work you're doing in the trigger.
>>    
>>
>>>NB. My real-world application 'collects' id's in need for deferred work
>>>      
>>>
>>I think you're doing a lot more than is wise to do in triggers.
>>    
>>
>
>I probably wasn't clear enough on this. I'm not creating types and/or 
>temporary tables or anything of that kind.
>
>The ratio is probably explained better by this example:
>
>- the database has knowledge on 'parts' and 'sets', the sets have a few fields 
>whose content depend on the parts, but the proper value for these fields can 
>only be determined by looking at all the parts of the particular set together 
>(i.e. it's not a plain 'part-count' that one could update by a trigger on the 
>part)
>
>- during a transaction, a number of things will happen to various parts of 
>various sets, so I have after triggers on the parts that will insert the ids 
>of the sets that need an update into a set_update holding table; in turn, 
>this set_update table has a deferred trigger
>
>- upon execution of the deferred triggers, I now know that all the work on the 
>parts is finished, so the deferred trigger initiates an update for the sets 
>whose ids are in the update table and it will delete these ids afterwards
>
>Now, because multiple updates to parts of the same set will result in multiple 
>inserts in the update table, I want to avoid doing the set-update more that 
>once. 
>
>Obviously, it would be better to be able to 'cancel' the rest of the calls to 
>the deferred trigger after it has been executed for the first time, but that 
>doesn't seem possible.
>
>Even better would be to use a 'for each statement' trigger on the set_update 
>holding table instead, but it is not possible to create a deferred 'for each 
>statement' trigger..... ;(
>
>So, I seem to be a bit between a rock and a hard place here, I must use 
>deferred triggers in order to avoid a costly set update on each part update, 
>but in such a deferred trigger I cannot avoid doing the update multiple 
>times....(due to the growing cost of a 'delete from' in the trigger)
>
>Mmm, it seems that by hacking pg_trigger I am able to create a for each 
>statement trigger that is 'deferrable initially deferred'.
>
>This probably solves my problem, I will ask on 'general' whether this has any 
>unforseen side effects and whether or not a 'regular' deferrable for each 
>statement trigger is incorporated in v8.0.
>
>Thanks for you reply!
>
>
>
>  
>


From pgsql-performance-owner@postgresql.org  Wed Aug 18 20:11:33 2004
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	Wed, 18 Aug 2004 16:11:37 PDT
Date: Wed, 18 Aug 2004 16:11:37 -0700 (PDT)
From: Artimenko Igor 
Subject: Re: Postgres does not utilyze indexes
To: pgsql-performance@postgresql.org
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Thanks a lot. This issue has been resolved by casting to int8. I thought Postgres does those casts
up by himself implicitelly.

=====
Thanks a lot
Igor Artimenko
I specialize in 
Java, J2EE, Unix, Linux, HP, AIX, Solaris, Progress, Oracle, DB2, Postgres, Data Modeling


		
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From pgsql-performance-owner@postgresql.org  Thu Aug 19 01:42:43 2004
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From: William Yu 
X-Newsgroups: comp.databases.postgresql.performance
Subject: Re: Help specifying new machine
Date: Wed, 18 Aug 2004 21:26:45 -0700
Organization: Hub.Org Networking Services
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References: <20040809165657.GB15169@campbell-lange.net>
	 
	 
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Raoul Buzziol wrote:
> I looked for some benchmarks, and I would know if I'm right on:
> - Dual Opteron 246 have aproximately the same performance of a Dual Xeon 3Gh
> (Opteron a little better)
> - Opteron system equal or cheeper than Xeon system.

In terms of general database performance, top of the line dual opteron 
will perform roughly the same as top of the line dual xeon. Assuming you 
just run in 32-bit mode. Throw in 64-bit mode, NUMA, etc, all bets are off.

In terms of Postgres database performance, Opteron *may* be the better 
CPU for this app but there's not enough data points yet. Here's a recent 
review at Anandtech showing Opteron 150 (2.4ghz) versus 64-bit Prescott 
3.6hgz with some very simple MySQL and Postgres benchmarks:

http://www.anandtech.com/linux/showdoc.aspx?i=2163&p=2

What is a slight lead in MySQL becomes a blowout in Postgres. Of course, 
this is just the 1MB cache model. I'm sure if you went with the 2MB or 
4MB models, the Xeons would come up much closer.

The really good sign in the above numbers though is that somebody 
finally included Postgres in their benchmark suite. :) We may be seeing 
more and more data points to evaluate hardware for Postgres in the near 
future.

From pgsql-performance-owner@postgresql.org  Thu Aug 19 02:49:27 2004
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To: William Yu 
Cc: pgsql-performance@postgresql.org
Subject: Re: Help specifying new machine 
In-reply-to:  
References: <20040809165657.GB15169@campbell-lange.net>
	 
	 
	
Comments: In-reply-to William Yu 
	message dated "Wed, 18 Aug 2004 21:26:45 -0700"
Date: Thu, 19 Aug 2004 01:49:15 -0400
Message-ID: <12077.1092894555@sss.pgh.pa.us>
From: Tom Lane 
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William Yu  writes:
> In terms of Postgres database performance, Opteron *may* be the better 
> CPU for this app but there's not enough data points yet. Here's a recent 
> review at Anandtech showing Opteron 150 (2.4ghz) versus 64-bit Prescott 
> 3.6hgz with some very simple MySQL and Postgres benchmarks:

> http://www.anandtech.com/linux/showdoc.aspx?i=2163&p=2

> What is a slight lead in MySQL becomes a blowout in Postgres.

This is really interesting.  We had previously seen some evidence that
the Xeon sucks at running Postgres, but I thought that the issues only
materialized with multiple CPUs (because what we were concerned about
was the cost of transferring cache lines across CPUs).  AFAICS this test
is using single CPUs.  Maybe there is more going on than we realized.

			regards, tom lane

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Subject: Re: I could not get postgres to utilizy indexes
Date: Thu, 19 Aug 2004 09:54:47 +0200
Message-ID: 
 
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Thread-Topic: I could not get postgres to utilizy indexes
Thread-Index: AcSEZbJwv6sR2bdDTJ+eEmRsHloP7wBW8Nxw
From: "Leeuw van der, Tim" 
To: "Igor Artimenko" ,
	
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Hi,

You asked the very same question yesterday, and I believe you got some usef=
ul answers. Why do you post the question again?

You don't even mention your previous post, and you didn't continue the thre=
ad which you started yesterday.

Did you try out any of the suggestions which you got yesterday? Do you have=
 further questions about, for instance, how to do casting of values? If so,=
 please continue posting with the previous thread, rather than reposting th=
e same question with a different subject.

regards,

--Tim


-----Original Message-----
From: pgsql-performance-owner@postgresql.org
[mailto:pgsql-performance-owner@postgresql.org]On Behalf Of Igor
Artimenko
Sent: dinsdag 17 augustus 2004 16:23
To: pgsql-performance@postgresql.org
Subject: [PERFORM] I could not get postgres to utilizy indexes


Hi verybody!

I can't make use of indexes even I tried the same test by changing differen=
t settings in postgres.conf like geqo to off/on & geqo related parameters, =
enable_seqscan off/on & so on. Result is the same.=20

Here is test itself:

I've created simplest table test and executed the same statement "explain a=
nalyze select id from test where id =3D 50000;" Few times I added 100,000 r=
ecords, applied vacuum full; and issued above explain command.=20
Postgres uses sequential scan instead of index one.=20
Of cause Time to execute the same statement constantly grows. In my mind in=
dex should not allow time to grow so much.=20=20

Why Postgres does not utilizes primary unique index?
What I'm missing? It continue growing even there are 1,200,000 records. It =
should at least start using index at some point.


Details are below:
100,000 records:
QUERY PLAN
---------------------------------------------------------------------------=
-------------------------
 Seq Scan on test  (cost=3D0.00..2427.00 rows=3D2 width=3D8) (actual time=
=3D99.626..199.835 rows=3D1 loops=3D1)
   Filter: (id =3D 50000)
 Total runtime: 199.990 ms

200,000 records:
QUERY PLAN
---------------------------------------------------------------------------=
--------------------------
 Seq Scan on test  (cost=3D0.00..4853.00 rows=3D2 width=3D8) (actual time=
=3D100.389..402.770 rows=3D1 loops=3D1)
   Filter: (id =3D 50000)
 Total runtime: 402.926 ms


300,000 records:
QUERY PLAN
---------------------------------------------------------------------------=
--------------------------
 Seq Scan on test  (cost=3D0.00..7280.00 rows=3D1 width=3D8) (actual time=
=3D100.563..616.064 rows=3D1 loops=3D1)
   Filter: (id =3D 50000)
 Total runtime: 616.224 ms
(3 rows)

I've created test table by script:

CREATE TABLE test
(
  id int8 NOT NULL DEFAULT nextval('next_id_seq'::text) INIQUE,
  description char(50),
  CONSTRAINT users_pkey PRIMARY KEY (id)
);

CREATE SEQUENCE next_id_seq
  INCREMENT 1
  MINVALUE 1
  MAXVALUE 10000000000
  START 1
  CACHE 5
  CYCLE;

I use postgres 7.4.2




---------------------------(end of broadcast)---------------------------
TIP 6: Have you searched our list archives?

               http://archives.postgresql.org

From pgsql-performance-owner@postgresql.org  Thu Aug 19 10:15:55 2004
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Subject: help with query
From: Dave Cramer 
Reply-To: pg@fastcrypt.com
To: perform 
Content-Type: text/plain
Organization: Cramer Consulting
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RT uses a query like:

SELECT distinct main.oid,main.* FROM Tickets main
WHERE
(main.EffectiveId = main.id)
AND
(main.Status != 'deleted')
AND
    ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
AND
    ( (main.Queue = '9') )
AND ((
        ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
      OR
        ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
      or
        (main.id = '17417')
     )
  );


which produces a query plan:

Nested Loop  (cost=0.00..813.88 rows=1 width=169)
   Join Filter: (((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id
= 17417)) AND (("outer".id = "inner".localtarget) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("inner"
.localtarget = 17417) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR ("inner".localtarget = 17417) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR (
"inner".localtarget = 17417) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("inner".loca
lbase = 17417) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)))
   ->  Index Scan using tickets1 on tickets main  (cost=0.00..657.61 rows=1 width=169)
         Index Cond: (queue = 9)
         Filter: ((effectiveid = id) AND ((status)::text <> 'deleted'::text) AND ((("type")::text = 'ticket'::text) OR (("type")::text = 'subticket'::text)))
   ->  Seq Scan on links  (cost=0.00..46.62 rows=1462 width=20)

If I rewrite the query as:

SELECT main.* FROM Tickets main
WHERE
(main.EffectiveId = main.id)
AND
(main.Status != 'deleted')
AND
    ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
AND
    ( (main.Queue = '9') )
AND (
        17417 in (select links.localtarget from links where links.type='MemberOf' and main.id=links.localbase)
        or
        17417 in ( select links.localbase from links where links.type='MemberOf' and main.id=links.localtarget)
      or
        main.id = '17417'
    )
  ;

The time for the query goes from 1500ms to 15ms. The two OR clauses 

        ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
      OR
        ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )

don't contribute to the result set in this particular dataset, which is why the speed increases so dramatically.

Is there a way to rewrite the top query to get the same results? I have already talked to Best Practical, 
and subqueries are not easily embraced.

Dave
-- 
Dave Cramer
519 939 0336
ICQ # 14675561


From pgsql-performance-owner@postgresql.org  Thu Aug 19 10:36:02 2004
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Date: Thu, 19 Aug 2004 06:38:48 -0700
From: Brad Bulger 
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To: pg@fastcrypt.com
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Subject: Re: help with query
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You're doing a join except not, is the trouble, looks like. The query is really
"FROM Tickets main, Links", but when Tickets.id is 17417, you've got no join
to the Links table. So you end up getting every row in Links for each row in
Tickets with id = 17417.

I'd think this wants to be two queries or a union:

SELECT distinct main.oid,main.* FROM Tickets main
WHERE (main.EffectiveId = main.id)
AND (main.Status != 'deleted')
AND ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
AND ( (main.Queue = '9') )
AND ( (main.id = '17417'))
union
SELECT distinct main.oid,main.* FROM Tickets main, Links
WHERE (main.EffectiveId = main.id)
AND (main.Status != 'deleted')
AND ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
AND ( (main.Queue = '9') )
AND ( (Links.Type = 'MemberOf') )
AND ( (Links.LocalTarget = '17417') )
AND ( (main.id = Links.LocalBase) ) OR (main.id = Links.LocalTarget) )
;

or else, yah, a subquery:

[...]
AND (
  main.id = '17417'
  or
  exists(
    select true from Links
    where Type = 'MemberOf' and LocalTarget = '17417'
     and (LocalBase = main.id or LocalTarget = main.id)
  )
)

Those are the only things I can think of to make it work, anyways.

Dave Cramer wrote:

> RT uses a query like:
> 
> SELECT distinct main.oid,main.* FROM Tickets main
> WHERE
> (main.EffectiveId = main.id)
> AND
> (main.Status != 'deleted')
> AND
>     ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> AND
>     ( (main.Queue = '9') )
> AND ((
>         ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
>       OR
>         ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
>       or
>         (main.id = '17417')
>      )
>   );
> 
> 
> which produces a query plan:
> 
> Nested Loop  (cost=0.00..813.88 rows=1 width=169)
>    Join Filter: (((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id
> = 17417)) AND (("outer".id = "inner".localtarget) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("inner"
> .localtarget = 17417) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR ("inner".localtarget = 17417) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR (
> "inner".localtarget = 17417) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("inner".loca
> lbase = 17417) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)))
>    ->  Index Scan using tickets1 on tickets main  (cost=0.00..657.61 rows=1 width=169)
>          Index Cond: (queue = 9)
>          Filter: ((effectiveid = id) AND ((status)::text <> 'deleted'::text) AND ((("type")::text = 'ticket'::text) OR (("type")::text = 'subticket'::text)))
>    ->  Seq Scan on links  (cost=0.00..46.62 rows=1462 width=20)
> 
> If I rewrite the query as:
> 
> SELECT main.* FROM Tickets main
> WHERE
> (main.EffectiveId = main.id)
> AND
> (main.Status != 'deleted')
> AND
>     ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> AND
>     ( (main.Queue = '9') )
> AND (
>         17417 in (select links.localtarget from links where links.type='MemberOf' and main.id=links.localbase)
>         or
>         17417 in ( select links.localbase from links where links.type='MemberOf' and main.id=links.localtarget)
>       or
>         main.id = '17417'
>     )
>   ;
> 
> The time for the query goes from 1500ms to 15ms. The two OR clauses 
> 
>         ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
>       OR
>         ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
> 
> don't contribute to the result set in this particular dataset, which is why the speed increases so dramatically.
> 
> Is there a way to rewrite the top query to get the same results? I have already talked to Best Practical, 
> and subqueries are not easily embraced.
> 
> Dave

From pgsql-performance-owner@postgresql.org  Thu Aug 19 10:49:21 2004
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Subject: Re: help with query
From: Dave Cramer 
Reply-To: pg@fastcrypt.com
To: Brad Bulger 
Cc: perform 
In-Reply-To: <4124AD68.8000208@madfish.com>
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	<4124AD68.8000208@madfish.com>
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Brad,

Thanks, that runs on the same order of magnitude as the subqueries.

DAve
On Thu, 2004-08-19 at 09:38, Brad Bulger wrote:
> You're doing a join except not, is the trouble, looks like. The query is really
> "FROM Tickets main, Links", but when Tickets.id is 17417, you've got no join
> to the Links table. So you end up getting every row in Links for each row in
> Tickets with id = 17417.
> 
> I'd think this wants to be two queries or a union:
> 
> SELECT distinct main.oid,main.* FROM Tickets main
> WHERE (main.EffectiveId = main.id)
> AND (main.Status != 'deleted')
> AND ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> AND ( (main.Queue = '9') )
> AND ( (main.id = '17417'))
> union
> SELECT distinct main.oid,main.* FROM Tickets main, Links
> WHERE (main.EffectiveId = main.id)
> AND (main.Status != 'deleted')
> AND ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> AND ( (main.Queue = '9') )
> AND ( (Links.Type = 'MemberOf') )
> AND ( (Links.LocalTarget = '17417') )
> AND ( (main.id = Links.LocalBase) ) OR (main.id = Links.LocalTarget) )
> ;
> 
> or else, yah, a subquery:
> 
> [...]
> AND (
>   main.id = '17417'
>   or
>   exists(
>     select true from Links
>     where Type = 'MemberOf' and LocalTarget = '17417'
>      and (LocalBase = main.id or LocalTarget = main.id)
>   )
> )
> 
> Those are the only things I can think of to make it work, anyways.
> 
> Dave Cramer wrote:
> 
> > RT uses a query like:
> > 
> > SELECT distinct main.oid,main.* FROM Tickets main
> > WHERE
> > (main.EffectiveId = main.id)
> > AND
> > (main.Status != 'deleted')
> > AND
> >     ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> > AND
> >     ( (main.Queue = '9') )
> > AND ((
> >         ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
> >       OR
> >         ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
> >       or
> >         (main.id = '17417')
> >      )
> >   );
> > 
> > 
> > which produces a query plan:
> > 
> > Nested Loop  (cost=0.00..813.88 rows=1 width=169)
> >    Join Filter: (((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id
> > = 17417)) AND (("outer".id = "inner".localtarget) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("inner"
> > .localtarget = 17417) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR ("inner".localtarget = 17417) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR (
> > "inner".localtarget = 17417) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("inner".loca
> > lbase = 17417) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)))
> >    ->  Index Scan using tickets1 on tickets main  (cost=0.00..657.61 rows=1 width=169)
> >          Index Cond: (queue = 9)
> >          Filter: ((effectiveid = id) AND ((status)::text <> 'deleted'::text) AND ((("type")::text = 'ticket'::text) OR (("type")::text = 'subticket'::text)))
> >    ->  Seq Scan on links  (cost=0.00..46.62 rows=1462 width=20)
> > 
> > If I rewrite the query as:
> > 
> > SELECT main.* FROM Tickets main
> > WHERE
> > (main.EffectiveId = main.id)
> > AND
> > (main.Status != 'deleted')
> > AND
> >     ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> > AND
> >     ( (main.Queue = '9') )
> > AND (
> >         17417 in (select links.localtarget from links where links.type='MemberOf' and main.id=links.localbase)
> >         or
> >         17417 in ( select links.localbase from links where links.type='MemberOf' and main.id=links.localtarget)
> >       or
> >         main.id = '17417'
> >     )
> >   ;
> > 
> > The time for the query goes from 1500ms to 15ms. The two OR clauses 
> > 
> >         ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
> >       OR
> >         ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
> > 
> > don't contribute to the result set in this particular dataset, which is why the speed increases so dramatically.
> > 
> > Is there a way to rewrite the top query to get the same results? I have already talked to Best Practical, 
> > and subqueries are not easily embraced.
> > 
> > Dave
> 
-- 
Dave Cramer
519 939 0336
ICQ # 14675561


From pgsql-performance-owner@postgresql.org  Thu Aug 19 11:16:31 2004
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Subject: Re: help with query
From: Dave Cramer 
Reply-To: pg@fastcrypt.com
To: Brad Bulger 
Cc: perform 
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>From what I can figure, queries like this run much quicker on other
databases, is this something that can be improved ?

Dave
On Thu, 2004-08-19 at 09:38, Brad Bulger wrote:
> You're doing a join except not, is the trouble, looks like. The query is really
> "FROM Tickets main, Links", but when Tickets.id is 17417, you've got no join
> to the Links table. So you end up getting every row in Links for each row in
> Tickets with id = 17417.
> 
> I'd think this wants to be two queries or a union:
> 
> SELECT distinct main.oid,main.* FROM Tickets main
> WHERE (main.EffectiveId = main.id)
> AND (main.Status != 'deleted')
> AND ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> AND ( (main.Queue = '9') )
> AND ( (main.id = '17417'))
> union
> SELECT distinct main.oid,main.* FROM Tickets main, Links
> WHERE (main.EffectiveId = main.id)
> AND (main.Status != 'deleted')
> AND ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> AND ( (main.Queue = '9') )
> AND ( (Links.Type = 'MemberOf') )
> AND ( (Links.LocalTarget = '17417') )
> AND ( (main.id = Links.LocalBase) ) OR (main.id = Links.LocalTarget) )
> ;
> 
> or else, yah, a subquery:
> 
> [...]
> AND (
>   main.id = '17417'
>   or
>   exists(
>     select true from Links
>     where Type = 'MemberOf' and LocalTarget = '17417'
>      and (LocalBase = main.id or LocalTarget = main.id)
>   )
> )
> 
> Those are the only things I can think of to make it work, anyways.
> 
> Dave Cramer wrote:
> 
> > RT uses a query like:
> > 
> > SELECT distinct main.oid,main.* FROM Tickets main
> > WHERE
> > (main.EffectiveId = main.id)
> > AND
> > (main.Status != 'deleted')
> > AND
> >     ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> > AND
> >     ( (main.Queue = '9') )
> > AND ((
> >         ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
> >       OR
> >         ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
> >       or
> >         (main.id = '17417')
> >      )
> >   );
> > 
> > 
> > which produces a query plan:
> > 
> > Nested Loop  (cost=0.00..813.88 rows=1 width=169)
> >    Join Filter: (((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id
> > = 17417)) AND (("outer".id = "inner".localtarget) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("inner"
> > .localtarget = 17417) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR ("inner".localtarget = 17417) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR (
> > "inner".localtarget = 17417) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("inner".loca
> > lbase = 17417) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)))
> >    ->  Index Scan using tickets1 on tickets main  (cost=0.00..657.61 rows=1 width=169)
> >          Index Cond: (queue = 9)
> >          Filter: ((effectiveid = id) AND ((status)::text <> 'deleted'::text) AND ((("type")::text = 'ticket'::text) OR (("type")::text = 'subticket'::text)))
> >    ->  Seq Scan on links  (cost=0.00..46.62 rows=1462 width=20)
> > 
> > If I rewrite the query as:
> > 
> > SELECT main.* FROM Tickets main
> > WHERE
> > (main.EffectiveId = main.id)
> > AND
> > (main.Status != 'deleted')
> > AND
> >     ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> > AND
> >     ( (main.Queue = '9') )
> > AND (
> >         17417 in (select links.localtarget from links where links.type='MemberOf' and main.id=links.localbase)
> >         or
> >         17417 in ( select links.localbase from links where links.type='MemberOf' and main.id=links.localtarget)
> >       or
> >         main.id = '17417'
> >     )
> >   ;
> > 
> > The time for the query goes from 1500ms to 15ms. The two OR clauses 
> > 
> >         ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
> >       OR
> >         ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
> > 
> > don't contribute to the result set in this particular dataset, which is why the speed increases so dramatically.
> > 
> > Is there a way to rewrite the top query to get the same results? I have already talked to Best Practical, 
> > and subqueries are not easily embraced.
> > 
> > Dave
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 3: if posting/reading through Usenet, please send an appropriate
>       subscribe-nomail command to majordomo@postgresql.org so that your
>       message can get through to the mailing list cleanly
> 
-- 
Dave Cramer
519 939 0336
ICQ # 14675561


From pgsql-performance-owner@postgresql.org  Thu Aug 19 11:21:35 2004
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Subject: Re: help with query
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how about:

SELECT distinct main.oid,main.* FROM Tickets main
WHERE main.EffectiveId = main.id
AND main.Status != 'deleted'
AND ( main.Type = 'ticket' OR main.Type = 'subticket' )
AND ( main.Queue = '9' )
AND ( main.id = '17417'
   OR main.id IN (
     SELECT DISTINCT LocalTarget from Links
     where Type = 'MemberOf' and LocalTarget = '17417')
   OR main.id IN (
     SELECT DISTINCT LocalBase from Links
     where Type = 'MemberOf' and LocalTarget = '17417'))




Dave Cramer wrote:

> Brad,
> 
> Thanks, that runs on the same order of magnitude as the subqueries.
> 
> DAve
> On Thu, 2004-08-19 at 09:38, Brad Bulger wrote:
> 
>>You're doing a join except not, is the trouble, looks like. The query is really
>>"FROM Tickets main, Links", but when Tickets.id is 17417, you've got no join
>>to the Links table. So you end up getting every row in Links for each row in
>>Tickets with id = 17417.
>>
>>I'd think this wants to be two queries or a union:
>>
>>SELECT distinct main.oid,main.* FROM Tickets main
>>WHERE (main.EffectiveId = main.id)
>>AND (main.Status != 'deleted')
>>AND ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
>>AND ( (main.Queue = '9') )
>>AND ( (main.id = '17417'))
>>union
>>SELECT distinct main.oid,main.* FROM Tickets main, Links
>>WHERE (main.EffectiveId = main.id)
>>AND (main.Status != 'deleted')
>>AND ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
>>AND ( (main.Queue = '9') )
>>AND ( (Links.Type = 'MemberOf') )
>>AND ( (Links.LocalTarget = '17417') )
>>AND ( (main.id = Links.LocalBase) ) OR (main.id = Links.LocalTarget) )
>>;
>>
>>or else, yah, a subquery:
>>
>>[...]
>>AND (
>>  main.id = '17417'
>>  or
>>  exists(
>>    select true from Links
>>    where Type = 'MemberOf' and LocalTarget = '17417'
>>     and (LocalBase = main.id or LocalTarget = main.id)
>>  )
>>)
>>
>>Those are the only things I can think of to make it work, anyways.
>>
>>Dave Cramer wrote:
>>
>>
>>>RT uses a query like:
>>>
>>>SELECT distinct main.oid,main.* FROM Tickets main
>>>WHERE
>>>(main.EffectiveId = main.id)
>>>AND
>>>(main.Status != 'deleted')
>>>AND
>>>    ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
>>>AND
>>>    ( (main.Queue = '9') )
>>>AND ((
>>>        ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
>>>      OR
>>>        ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
>>>      or
>>>        (main.id = '17417')
>>>     )
>>>  );
>>>
>>>
>>>which produces a query plan:
>>>
>>>Nested Loop  (cost=0.00..813.88 rows=1 width=169)
>>>   Join Filter: (((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id
>>>= 17417)) AND (("outer".id = "inner".localtarget) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("inner"
>>>.localtarget = 17417) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR ("inner".localtarget = 17417) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR (
>>>"inner".localtarget = 17417) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("inner".loca
>>>lbase = 17417) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)))
>>>   ->  Index Scan using tickets1 on tickets main  (cost=0.00..657.61 rows=1 width=169)
>>>         Index Cond: (queue = 9)
>>>         Filter: ((effectiveid = id) AND ((status)::text <> 'deleted'::text) AND ((("type")::text = 'ticket'::text) OR (("type")::text = 'subticket'::text)))
>>>   ->  Seq Scan on links  (cost=0.00..46.62 rows=1462 width=20)
>>>
>>>If I rewrite the query as:
>>>
>>>SELECT main.* FROM Tickets main
>>>WHERE
>>>(main.EffectiveId = main.id)
>>>AND
>>>(main.Status != 'deleted')
>>>AND
>>>    ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
>>>AND
>>>    ( (main.Queue = '9') )
>>>AND (
>>>        17417 in (select links.localtarget from links where links.type='MemberOf' and main.id=links.localbase)
>>>        or
>>>        17417 in ( select links.localbase from links where links.type='MemberOf' and main.id=links.localtarget)
>>>      or
>>>        main.id = '17417'
>>>    )
>>>  ;
>>>
>>>The time for the query goes from 1500ms to 15ms. The two OR clauses 
>>>
>>>        ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
>>>      OR
>>>        ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
>>>
>>>don't contribute to the result set in this particular dataset, which is why the speed increases so dramatically.
>>>
>>>Is there a way to rewrite the top query to get the same results? I have already talked to Best Practical, 
>>>and subqueries are not easily embraced.
>>>
>>>Dave
>>

From pgsql-performance-owner@postgresql.org  Thu Aug 19 13:20:04 2004
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From: Josh Berkus 
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To: Tom Lane , William Yu 
Subject: Re: Help specifying new machine
Date: Thu, 19 Aug 2004 09:18:31 -0700
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Tom,

> This is really interesting.  We had previously seen some evidence that
> the Xeon sucks at running Postgres, but I thought that the issues only
> materialized with multiple CPUs (because what we were concerned about
> was the cost of transferring cache lines across CPUs).  AFAICS this test
> is using single CPUs.  Maybe there is more going on than we realized.

Aside from the fact that the Xeon architecture is a kludge?   

Intel really screwed up the whole Xeon line through some bad architectural 
decisions, and instead of starting over from scratch, "patched" the problem.  
The result has been sub-optimal Xeon performance for the last two years.

This is why AMD is still alive.   Better efficiency, lower cost.

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Thu Aug 19 14:43:07 2004
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	for pgsql-performance@postgresql.org; Thu, 19 Aug 2004 17:26:07 GMT
From: Gaetano Mendola 
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Subject: using an index worst performances
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Hi all,
I'm tring to optimize the following query:

http://rafb.net/paste/results/YdO9vM69.html

as you can see from the explain after defining the
index the performance is worst.

If I raise the default_statistic_target to 200
then the performance are worst then before:


Without index: 1.140 ms
With index: 1.400 ms
With default_statistic_targer = 200:   1.800 ms


tought anyone ?



Regards
Gaetano Mendola





From pgsql-performance-owner@postgresql.org  Tue Aug 24 15:48:36 2004
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Date: Thu, 19 Aug 2004 11:03:04 -0700
From: Daniel Ceregatti 
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Hi list,

I have a database with 1M "people" in it. Each person has about 20
attributes, such as height, weight, eye color, etc. I need to be able to
search for people based on these attributes. A search can be conducted
on one attribute, all attributes, or any number in between. How would
_you_ do this?

I have already attempted to answer this. My attempts are detailed here:

http://sh.nu/email.txt

This is the email I was originally going to send to this list. Since
it's so large, I decided to link to it instead. If you feel that it
belongs in a post to the list, let me know, and I'll post again.

I've discussed these attempts with people in #postgresql on
irc.freenode.net. Agliodbs (I presume you know who this is) was very
helpful, but in end was at a loss. I find myself in the same postition
at this time. He suggested I contact this list.

My ultimate goal is performance. This _must_ be fast. And by fast, I
mean, < 1 second, for every permutation of the number of attributes
searched for. Flexibility would be a bonus, but at this point I'll
settle for something that's harder to maintain if I can get the speed
gain I need.

Thanks,

Daniel Ceregatti

From pgsql-performance-owner@postgresql.org  Thu Aug 19 15:10:06 2004
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From: Richard Huxton 
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To: Gaetano Mendola 
Cc: pgsql-performance@postgresql.org
Subject: Re: using an index worst performances
References: 
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Gaetano Mendola wrote:
> Hi all,
> I'm tring to optimize the following query:
> 
> http://rafb.net/paste/results/YdO9vM69.html
> 
> as you can see from the explain after defining the
> index the performance is worst.
> 
> If I raise the default_statistic_target to 200
> then the performance are worst then before:
> 
> 
> Without index: 1.140 ms
> With index: 1.400 ms
> With default_statistic_targer = 200:   1.800 ms

Can I just check that 1.800ms means 1.8 secs (You're using . as the 
thousands separator)?

If it means 1.8ms then frankly the times are too short to mean anything 
without running them 100 times and averaging.

-- 
   Richard Huxton
   Archonet Ltd

From pgsql-performance-owner@postgresql.org  Thu Aug 19 17:13:08 2004
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From: Gaetano Mendola 
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Subject: Re: using an index worst performances
Date: Thu, 19 Aug 2004 21:56:38 +0200
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Richard Huxton wrote:

> Gaetano Mendola wrote:
> 
>> Hi all,
>> I'm tring to optimize the following query:
>>
>> http://rafb.net/paste/results/YdO9vM69.html
>>
>> as you can see from the explain after defining the
>> index the performance is worst.
>>
>> If I raise the default_statistic_target to 200
>> then the performance are worst then before:
>>
>>
>> Without index: 1.140 ms
>> With index: 1.400 ms
>> With default_statistic_targer = 200:   1.800 ms
> 
> 
> Can I just check that 1.800ms means 1.8 secs (You're using . as the 
> thousands separator)?
> 
> If it means 1.8ms then frankly the times are too short to mean anything 
> without running them 100 times and averaging.


It mean 1.8 ms and that execution time is sticky to that value even
with 1000 times.


Regards
Gaetano Mendola

From pgsql-performance-owner@postgresql.org  Thu Aug 19 22:37:50 2004
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From: Christopher Kings-Lynne 
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To: Gaetano Mendola 
Cc: Richard Huxton ,
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Subject: Re: using an index worst performances
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	<412505F6.6080000@bigfoot.com>
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>>> Without index: 1.140 ms
>>> With index: 1.400 ms
>>> With default_statistic_targer = 200:   1.800 ms
>>
>>
>>
>> Can I just check that 1.800ms means 1.8 secs (You're using . as the 
>> thousands separator)?
>>
>> If it means 1.8ms then frankly the times are too short to mean 
>> anything without running them 100 times and averaging.
> 
> 
> 
> It mean 1.8 ms and that execution time is sticky to that value even
> with 1000 times.

Given the almost irrelvant difference in the speed of those queries, I'd 
say that with the stats so high, postgres simply takes longer to check 
the statistics to come to the same conclusion.  ie. it has to loop over 
200 rows instead of just 10.

Chris


From pgsql-performance-owner@postgresql.org  Fri Aug 20 06:37:45 2004
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From: Gaetano Mendola 
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To: Christopher Kings-Lynne 
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Subject: Re: using an index worst performances
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	<412505F6.6080000@bigfoot.com>
	<4125565D.3060008@familyhealth.com.au>
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Hash: SHA1

Christopher Kings-Lynne wrote:

|>>> Without index: 1.140 ms
|>>> With index: 1.400 ms
|>>> With default_statistic_targer = 200:   1.800 ms
|>>
|>>
|>>
|>>
|>> Can I just check that 1.800ms means 1.8 secs (You're using . as the
|>> thousands separator)?
|>>
|>> If it means 1.8ms then frankly the times are too short to mean
|>> anything without running them 100 times and averaging.
|>
|>
|>
|>
|> It mean 1.8 ms and that execution time is sticky to that value even
|> with 1000 times.
|
|
| Given the almost irrelvant difference in the speed of those queries, I'd
| say that with the stats so high, postgres simply takes longer to check
| the statistics to come to the same conclusion.  ie. it has to loop over
| 200 rows instead of just 10.

The time increase seems too much.


Regards
Gaetano Mendola




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From pgsql-performance-owner@postgresql.org  Fri Aug 20 09:55:53 2004
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Subject: Re: using an index worst performances
From: Rod Taylor 
To: Gaetano Mendola 
Cc: Christopher Kings-Lynne ,
	Richard Huxton ,
	Postgresql Performance 
In-Reply-To: <4125C657.7000702@bigfoot.com>
References:  <4124ECF3.6040901@archonet.com>
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On Fri, 2004-08-20 at 05:37, Gaetano Mendola wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Christopher Kings-Lynne wrote:
> 
> |>>> Without index: 1.140 ms
> |>>> With index: 1.400 ms
> |>>> With default_statistic_targer = 200:   1.800 ms
> |>>
> |>>
> |>>
> |>>
> |>> Can I just check that 1.800ms means 1.8 secs (You're using . as the
> |>> thousands separator)?
> |>>
> |>> If it means 1.8ms then frankly the times are too short to mean
> |>> anything without running them 100 times and averaging.
> |>
> |>
> |>
> |>
> |> It mean 1.8 ms and that execution time is sticky to that value even
> |> with 1000 times.
> |
> |
> | Given the almost irrelvant difference in the speed of those queries, I'd
> | say that with the stats so high, postgres simply takes longer to check
> | the statistics to come to the same conclusion.  ie. it has to loop over
> | 200 rows instead of just 10.
> 
> The time increase seems too much.

We can test this.

What are the times without the index, with the index and with the higher
statistics value when using a prepared query?



From pgsql-performance-owner@postgresql.org  Fri Aug 20 09:56:03 2004
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Subject: pg_restore very slow in 8.0.0beta1
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Hi,
I'm migrating data from 7.4.2 to 8.0.0beta1 and the process is slow (10 15 =
tuples per second)

Can be a type conversion issue?

RedS
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Hi,


I'm migrating data from 7.4.2 to 8.0.0beta=
1 and the=20
process is slow (10 15 tuples per second)


 


Can be a type conversion issue?

 


RedS


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From pgsql-performance-owner@postgresql.org  Fri Aug 20 10:36:33 2004
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From: Manfred Koizar 
To: "Leeuw van der, Tim" 
Cc: "Igor Artimenko" ,
	
Subject: Re: I could not get postgres to utilizy indexes
Date: Fri, 20 Aug 2004 15:37:40 +0200
Message-ID: 
References: 
 
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On Thu, 19 Aug 2004 09:54:47 +0200, "Leeuw van der, Tim"
 wrote:
>You asked the very same question yesterday, and I believe you got some useful answers. Why do you post the question again?

Tim, no need to be rude here.  We see this effect from time to time when
a new user sends a message to a mailing list while not subscribed.  The
sender gets an automated reply from majordomo, subscribes to the list
and sends his mail again.  One or two days later the original message is
approved (by Marc, AFAIK) and forwarded to the list.  Look at the
timestamps in these header lines:
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>[more instructions]

And while we are teaching netiquette, could you please stop top-posting
and full-quoting.

Igor, welcome to the list!  Did the suggestions you got solve your
problem?

Servus
 Manfred

From pgsql-performance-owner@postgresql.org  Fri Aug 20 10:45:27 2004
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Subject: Re: I could not get postgres to utilizy indexes
Date: Fri, 20 Aug 2004 15:45:05 +0200
Message-ID: 
 
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Thread-Topic: [PERFORM] I could not get postgres to utilizy indexes
Thread-Index: AcSGurs8mJaFRnNiQrCVefjNVeXl7QAAHgDg
From: "Leeuw van der, Tim" 
To: "Manfred Koizar" 
Cc: "Igor Artimenko" ,
	
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Hi all,

I offered apologies to Igor Artimenko in private mail already; I'll apologi=
ze again here.

About top-posting: Outlook Exchange teaches bad habits. Can you set Outlook=
 Exchange to prefix lines with "> " only when mail is in text-only format b=
ut not when mail arrives in html / rtf format?

About full quoting: my apologies.

-----Original Message-----
From: Manfred Koizar [mailto:mkoi-pg@aon.at]
Sent: vrijdag 20 augustus 2004 15:38
To: Leeuw van der, Tim
Cc: Igor Artimenko; pgsql-performance@postgresql.org
Subject: Re: [PERFORM] I could not get postgres to utilizy indexes


On Thu, 19 Aug 2004 09:54:47 +0200, "Leeuw van der, Tim"
 wrote:
>You asked the very same question yesterday, and I believe you got some use=
ful answers. Why do you post the question again?

Tim, no need to be rude here.=20=20
[...]
>[more instructions]

And while we are teaching netiquette, could you please stop top-posting
and full-quoting.

Igor, welcome to the list!  Did the suggestions you got solve your
problem?

Servus
 Manfred

From pgsql-performance-owner@postgresql.org  Fri Aug 20 13:13:05 2004
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From: Gaetano Mendola 
X-Newsgroups: comp.databases.postgresql.performance
Subject: Re: using an index worst performances
Date: Fri, 20 Aug 2004 17:52:33 +0200
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Rod Taylor wrote:

> On Fri, 2004-08-20 at 05:37, Gaetano Mendola wrote:
> 
>>-----BEGIN PGP SIGNED MESSAGE-----
>>Hash: SHA1
>>
>>Christopher Kings-Lynne wrote:
>>
>>|>>> Without index: 1.140 ms
>>|>>> With index: 1.400 ms
>>|>>> With default_statistic_targer = 200:   1.800 ms
>>|>>
>>|>>
>>|>>
>>|>>
>>|>> Can I just check that 1.800ms means 1.8 secs (You're using . as the
>>|>> thousands separator)?
>>|>>
>>|>> If it means 1.8ms then frankly the times are too short to mean
>>|>> anything without running them 100 times and averaging.
>>|>
>>|>
>>|>
>>|>
>>|> It mean 1.8 ms and that execution time is sticky to that value even
>>|> with 1000 times.
>>|
>>|
>>| Given the almost irrelvant difference in the speed of those queries, I'd
>>| say that with the stats so high, postgres simply takes longer to check
>>| the statistics to come to the same conclusion.  ie. it has to loop over
>>| 200 rows instead of just 10.
>>
>>The time increase seems too much.
> 
> 
> We can test this.
> 
> What are the times without the index, with the index and with the higher
> statistics value when using a prepared query?

Using a prepared query:

Without index and default stat 10 :    1.12 ms
Without index and default stat 1000 :  1.25 ms
With index and default stat 10:        1.35 ms
With index and default stat 1000:      1.6 ms

that values are the average obtained after the very first one,
on 20 execution.



Regards
Gaetano Mendola

























From pgsql-performance-owner@postgresql.org  Fri Aug 20 13:19:24 2004
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To: Gaetano Mendola 
Cc: Rod Taylor , pgsql-performance@postgresql.org
Subject: Re: using an index worst performances 
In-reply-to: <41261E41.3080204@bigfoot.com> 
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	<41261E41.3080204@bigfoot.com>
Comments: In-reply-to Gaetano Mendola 
	message dated "Fri, 20 Aug 2004 17:52:33 +0200"
Date: Fri, 20 Aug 2004 12:19:22 -0400
Message-ID: <22026.1093018762@sss.pgh.pa.us>
From: Tom Lane 
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Gaetano Mendola  writes:
> Using a prepared query:

> Without index and default stat 10 :    1.12 ms
> Without index and default stat 1000 :  1.25 ms
> With index and default stat 10:        1.35 ms
> With index and default stat 1000:      1.6 ms

Could we see EXPLAIN ANALYZE EXECUTE output for each case?

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Fri Aug 20 13:20:41 2004
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Reply-To: 
From: "Danilo Mota" 
To: 
Subject: Query performance problem
Date: Fri, 20 Aug 2004 13:25:30 -0300
Organization: Nexen Tecnologia
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HI All,
 
I have a big performance issue concerning a PostgreSQL database.
 
I have the following server configuration:
 
Pentium 4 2.4 GHz
1 GB RAM
36 GB SCSI
 
And the following tables:
                                    TABLES
------------------------------------------------------------------------
--
==================  r_cliente: 75816 records
============================
CREATE TABLE "public"."r_cliente" (
  "pkcliente" INTEGER NOT NULL, 
  "cpfcnpj" VARCHAR(20) NOT NULL, 
  PRIMARY KEY("pkcliente")
) WITH OIDS;
 
CREATE UNIQUE INDEX "un_cliente_cpfcnpj" ON "public"."r_cliente"
USING btree ("cpfcnpj");
 
==================  sav_cliente_lg: 65671 records
=======================
CREATE TABLE "public"."sav_cliente_lg" (
  "codigo" INTEGER NOT NULL, 
  "cpfcnpj" VARCHAR(15) NOT NULL, 
  PRIMARY KEY("codigo")
) WITH OIDS;
 
CREATE INDEX "ix_savclientelg_cpfcnpj" ON "public"."sav_cliente_lg"
USING btree ("cpfcnpj");
 
 
 
Which I would like to run the following query:
 
                                    QUERY
------------------------------------------------------------------------
--
SELECT
 rc.pkcliente
FROM r_cliente AS rc
INNER JOIN sav_cliente_lg AS sc ON sc.cpfcnpj = sc.cpfcnpj;
 
 
 
 
The problem is, it takes a long time to run, I wait up to half an hour
and I get no result.
 
So, I executed the explain on the query and got the following results:
 
 
 
 
                                QUERY PLAN
------------------------------------------------------------------------
--
 Nested Loop  (cost=0.00..16696.87 rows=75816 width=4)
   ->  Seq Scan on sav_cliente_cf sc  (cost=0.00..3047.55 rows=1
width=0)
         Filter: ((cpfcnpj)::text = (cpfcnpj)::text)
   ->  Seq Scan on r_cliente rc  (cost=0.00..12891.16 rows=75816
width=4)
 
 
 
 
And made the following modifications on my POSTGRESQL.CONF file:
 
                                POSTGRESQL.CONF
------------------------------------------------------------------------
--
### VERSION: Postgresql 7.4.2 ###
shared_buffers = 7800
sort_mem = 4096
checkpoint_segments = 5  
effective_cache_size = 12000
cpu_operator_cost = 0.0015
stats_start_collector = false
 
 
Hope you can help me, I really need to get this running faster, and I am
out of ideas.
 
Since now, thanks a lot for your attention,
 
Danilo Mota

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Content-Type: text/html;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable























HI All,



 



I have a big performance issue concerning a PostgreSQL
database.



 



I have the following server configuration:



 



Pentium 4 2.4 GHz



1 GB RAM



36 GB SCSI



 <=
/font>



And the following tables:



        =
            &nb=
sp;            =
   TABLES



--------------------------------------------------------=
------------------



=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D  r_cliente: 75816 records 
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D



CREATE TABLE "public".&qu=
ot;r_cliente"
(



  "pkcliente" INTEGER NO=
T NULL, 



  "cpfcnpj" VARCHAR(20) =
NOT
NULL, 



  PRIMARY <=
span
class=3DGramE>KEY("pkcliente")=




) WITH OIDS;



 



CREATE UNIQUE INDEX "un_cliente_cpfcnpj" ON "public"."r_cliente"



USING btree ("cpfcnpj");



 



=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D  sav_cliente_lg: 65671 records 
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D



CREATE TABLE "public".&qu=
ot;sav_cliente_lg"
(



  "codigo" INTEGER NOT N=
ULL, 



  "cpfcnpj" VARCHAR(15) =
NOT
NULL, 



  PRIMARY <=
span
class=3DGramE>KEY("codigo")



) WITH OIDS;



 



CREATE INDEX "ix_savclientelg_cpfcnpj" ON "public"."sav_cliente_lg"



USING btree ("cpfcnpj");



 



 



 



Which I would like to run the following query:



 



        =
            &nb=
sp;            =
   QUERY



--------------------------------------------------------=
------------------



SELECT



 rc.pkcliente



FROM r_cliente AS rc



INNER JOIN sav_cliente_lg AS=
 sc ON
sc.cpfcnpj =3D sc.cpfcnpj<=
/span>;



 



 



 



 



The problem is, it takes a long time to run, I wait up to
half an hour and I get no result.



 



So, I executed the explain on=
 the
query and got the following results:



 



 



 



 



        =
            &nb=
sp;           QUER=
Y PLAN



--------------------------------------------------------=
------------------



 Nested Loop  (cost=3D0.00=
..16696.87
rows=3D75816 width=3D4)



   ->  Seq Scan on sav_cliente_cf sc&nb=
sp;
(cost=3D0.00..3047.55 rows=3D1 width=3D0)


    =
;     Filter: ((cpfcnpj)::text =3D (cpfcnpj)::text)



   ->  Seq Scan on r_cliente rc  (cost=3D0.00..12891.16 rows=3D7581=
6 width=3D4)



 



 



 



 



And made the following modific=
ations
on my POSTGRESQL.CONF file:



 



        =
            &nb=
sp;           POST=
GRESQL.CONF



--------------------------------------------------------=
------------------



### VERSION: Postgresql 7.4.=
2 ###



shared_buffers =
=3D 7800



sort_mem<=
font
size=3D2 face=3DArial> =
=3D 4096



checkpoint_segments =
=3D 5  



effective_cache_size =
=3D 12000



cpu_operator_cost =
=3D 0.0015



stats_start_collector =
=3D false



 



 



Hope you can help me, I really need to get this running
faster, and I am out of ideas.



 



Since now, thanks a lot for your attention,



 



Danilo <=
span
class=3DSpellE>Mota









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From pgsql-performance-owner@postgresql.org  Fri Aug 20 13:34:53 2004
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To: dmota@nexen.com.br
Cc: pgsql-performance@postgresql.org
Subject: Re: Query performance problem 
In-reply-to: <002201c486d2$4fbe4420$8afea8c0@nexen.lan> 
References: <002201c486d2$4fbe4420$8afea8c0@nexen.lan>
Comments: In-reply-to "Danilo Mota" 
	message dated "Fri, 20 Aug 2004 13:25:30 -0300"
Date: Fri, 20 Aug 2004 12:34:48 -0400
Message-ID: <22878.1093019688@sss.pgh.pa.us>
From: Tom Lane 
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"Danilo Mota"  writes:
> SELECT
>  rc.pkcliente
> FROM r_cliente AS rc
> INNER JOIN sav_cliente_lg AS sc ON sc.cpfcnpj = sc.cpfcnpj;

Surely you meant
  INNER JOIN sav_cliente_lg AS sc ON rc.cpfcnpj = sc.cpfcnpj;

I would also venture that your statistics are desperately out of date,
because if the planner's estimates are close to reality, even this
unconstrained-cross-product join shouldn't have taken that long.
 
			regards, tom lane

From pgsql-performance-owner@postgresql.org  Fri Aug 20 13:39:51 2004
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Date: Fri, 20 Aug 2004 11:48:21 -0500
From: Bruno Wolff III 
To: Danilo Mota 
Cc: pgsql-performance@postgresql.org
Subject: Re: Query performance problem
Message-ID: <20040820164821.GA26674@wolff.to>
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On Fri, Aug 20, 2004 at 13:25:30 -0300,
  Danilo Mota  wrote:
>  
> And the following tables:
>                                     TABLES
> ------------------------------------------------------------------------
> --
> ==================  r_cliente: 75816 records
> ============================
> CREATE TABLE "public"."r_cliente" (
>   "pkcliente" INTEGER NOT NULL, 
>   "cpfcnpj" VARCHAR(20) NOT NULL, 
>   PRIMARY KEY("pkcliente")
> ) WITH OIDS;
>  
> CREATE UNIQUE INDEX "un_cliente_cpfcnpj" ON "public"."r_cliente"
> USING btree ("cpfcnpj");
>  
> ==================  sav_cliente_lg: 65671 records
> =======================
> CREATE TABLE "public"."sav_cliente_lg" (
>   "codigo" INTEGER NOT NULL, 
>   "cpfcnpj" VARCHAR(15) NOT NULL, 
>   PRIMARY KEY("codigo")
> ) WITH OIDS;
>  
> CREATE INDEX "ix_savclientelg_cpfcnpj" ON "public"."sav_cliente_lg"
> USING btree ("cpfcnpj");
>  
>  
>  
> Which I would like to run the following query:
>  
>                                     QUERY
> ------------------------------------------------------------------------
> --
> SELECT
>  rc.pkcliente
> FROM r_cliente AS rc
> INNER JOIN sav_cliente_lg AS sc ON sc.cpfcnpj = sc.cpfcnpj;

I am going to assume that one of the sc.cpfcnpj's above is really rc.cpfcnpj
since that corresponds to the explain below.

sc.cpfcnpj and rc.cpfcnpj are different length varchars. You made need
an explicit cast to allow the use of indexes. (Unless there is a real
business rule that mandates the limits you have used, you probably want
to make them both type 'text'.)

Another potential problem is not having analyzed the tables. I don't think
this can be ruled out based on what you have showed us so far.

>  
> So, I executed the explain on the query and got the following results:

Generally you want to run EXPLAIN ANALYZE results when submitting questions
about performance problems rather than just EXPLAIN results.

From pgsql-performance-owner@postgresql.org  Fri Aug 20 13:50:01 2004
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To: Bruno Wolff III 
Cc: Danilo Mota ,
	pgsql-performance@postgresql.org
Subject: Re: Query performance problem 
In-reply-to: <20040820164821.GA26674@wolff.to> 
References: <002201c486d2$4fbe4420$8afea8c0@nexen.lan>
	<20040820164821.GA26674@wolff.to>
Comments: In-reply-to Bruno Wolff III 
	message dated "Fri, 20 Aug 2004 11:48:21 -0500"
Date: Fri, 20 Aug 2004 12:50:01 -0400
Message-ID: <27336.1093020601@sss.pgh.pa.us>
From: Tom Lane 
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Bruno Wolff III  writes:
> I am going to assume that one of the sc.cpfcnpj's above is really rc.cpfcnpj
> since that corresponds to the explain below.

No, actually the explain plan corresponds to the sc.cpfcnpj = sc.cpfcnpj
condition.  I didn't twig to the typo until I started to wonder why the
plan had the condition in the wrong place (attached to the seqscan and
not the join step).

> sc.cpfcnpj and rc.cpfcnpj are different length varchars. You made need
> an explicit cast to allow the use of indexes.

AFAIK the cross-type issues only apply to crossing actual types, not
lengths.  That does look like an error in the database schema, though.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Fri Aug 20 16:43:45 2004
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Subject: Re: using an index worst performances
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Tom Lane wrote:
| Gaetano Mendola  writes:
|
|>Using a prepared query:
|
|
|>Without index and default stat 10 :    1.12 ms

ariadne=# explain analyze execute test_ariadne;
~                                                                                                          QUERY PLAN
- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
~ Limit  (cost=46.15..46.17 rows=1 width=760) (actual time=0.926..1.035 rows=3 loops=1)
~   ->  Unique  (cost=46.15..46.17 rows=1 width=760) (actual time=0.904..0.969 rows=3 loops=1)
~         ->  Sort  (cost=46.15..46.15 rows=1 width=760) (actual time=0.891..0.909 rows=3 loops=1)
~               Sort Key: store_nodes.parent, store_nodes.priority, store_nodes."path", store_objects.id, store_objects."type", store_objects.object, date_part('epoch'::text, store_objects.lastchanged), store_objects.vtype
~               ->  Hash Join  (cost=1.74..46.14 rows=1 width=760) (actual time=0.342..0.825 rows=3 loops=1)
~                     Hash Cond: (("outer".vtype)::text = ("inner"."type")::text)
~                     ->  Nested Loop  (cost=0.00..44.38 rows=1 width=760) (actual time=0.198..0.618 rows=3 loops=1)
~                           ->  Nested Loop  (cost=0.00..38.93 rows=1 width=104) (actual time=0.157..0.447 rows=3 loops=1)
~                                 ->  Seq Scan on store_prop_article  (cost=0.00..1.75 rows=7 width=8) (actual time=0.030..0.119 rows=7 loops=1)
~                                       Filter: ((ar_start <= 1092924200) AND (ar_end >= 1092924200) AND ((ar_display)::text = 'default'::text))
~                                 ->  Index Scan using store_nodes_object on store_nodes  (cost=0.00..5.30 rows=1 width=96) (actual time=0.019..0.023 rows=0 loops=7)
~                                       Index Cond: ("outer".object = store_nodes.object)
~                                       Filter: (("path")::text ~~ '/sites/broadsat/news/%'::text)
~                           ->  Index Scan using store_objects_pkey on store_objects  (cost=0.00..5.43 rows=1 width=672) (actual time=0.013..0.020 rows=1 loops=3)
~                                 Index Cond: ("outer".object = store_objects.id)
~                     ->  Hash  (cost=1.74..1.74 rows=2 width=11) (actual time=0.085..0.085 rows=0 loops=1)
~                           ->  Seq Scan on store_types  (cost=0.00..1.74 rows=2 width=11) (actual time=0.038..0.064 rows=1 loops=1)
~                                 Filter: ((implements)::text = 'particle'::text)
~ Total runtime: 1.199 ms
(19 rows)


|>Without index and default stat 1000 :  1.25 ms

ariadne=# explain analyze execute test_ariadne;
~                                                                                                          QUERY PLAN
- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
~ Limit  (cost=46.14..46.16 rows=1 width=760) (actual time=1.027..1.126 rows=3 loops=1)
~   ->  Unique  (cost=46.14..46.16 rows=1 width=760) (actual time=1.014..1.077 rows=3 loops=1)
~         ->  Sort  (cost=46.14..46.14 rows=1 width=760) (actual time=1.001..1.019 rows=3 loops=1)
~               Sort Key: store_nodes.parent, store_nodes.priority, store_nodes."path", store_objects.id, store_objects."type", store_objects.object, date_part('epoch'::text, store_objects.lastchanged), store_objects.vtype
~               ->  Nested Loop  (cost=0.00..46.13 rows=1 width=760) (actual time=0.278..0.933 rows=3 loops=1)
~                     Join Filter: (("outer".vtype)::text = ("inner"."type")::text)
~                     ->  Nested Loop  (cost=0.00..44.38 rows=1 width=760) (actual time=0.208..0.591 rows=3 loops=1)
~                           ->  Nested Loop  (cost=0.00..38.93 rows=1 width=104) (actual time=0.168..0.417 rows=3 loops=1)
~                                 ->  Seq Scan on store_prop_article  (cost=0.00..1.75 rows=7 width=8) (actual time=0.038..0.118 rows=7 loops=1)
~                                       Filter: ((ar_start <= 1092924200) AND (ar_end >= 1092924200) AND ((ar_display)::text = 'default'::text))
~                                 ->  Index Scan using store_nodes_object on store_nodes  (cost=0.00..5.30 rows=1 width=96) (actual time=0.016..0.020 rows=0 loops=7)
~                                       Index Cond: ("outer".object = store_nodes.object)
~                                       Filter: (("path")::text ~~ '/sites/broadsat/news/%'::text)
~                           ->  Index Scan using store_objects_pkey on store_objects  (cost=0.00..5.43 rows=1 width=672) (actual time=0.012..0.022 rows=1 loops=3)
~                                 Index Cond: ("outer".object = store_objects.id)
~                     ->  Seq Scan on store_types  (cost=0.00..1.74 rows=1 width=11) (actual time=0.029..0.060 rows=1 loops=3)
~                           Filter: ((implements)::text = 'particle'::text)
~ Total runtime: 1.288 ms
(18 rows)


|>With index and default stat 10:        1.35 ms

ariadne=# explain analyze execute test_ariadne;
~                                                                                                          QUERY PLAN
- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
~ Limit  (cost=14.95..14.97 rows=1 width=760) (actual time=1.066..1.165 rows=3 loops=1)
~   ->  Unique  (cost=14.95..14.97 rows=1 width=760) (actual time=1.052..1.116 rows=3 loops=1)
~         ->  Sort  (cost=14.95..14.95 rows=1 width=760) (actual time=1.036..1.054 rows=3 loops=1)
~               Sort Key: store_nodes.parent, store_nodes.priority, store_nodes."path", store_objects.id, store_objects."type", store_objects.object, date_part('epoch'::text, store_objects.lastchanged), store_objects.vtype
~               ->  Hash Join  (cost=3.51..14.94 rows=1 width=760) (actual time=0.614..0.968 rows=3 loops=1)
~                     Hash Cond: ("outer".id = "inner".object)
~                     ->  Hash Join  (cost=1.74..13.15 rows=1 width=768) (actual time=0.281..0.651 rows=5 loops=1)
~                           Hash Cond: (("outer".vtype)::text = ("inner"."type")::text)
~                           ->  Nested Loop  (cost=0.00..11.39 rows=1 width=768) (actual time=0.070..0.406 rows=6 loops=1)
~                                 ->  Index Scan using test_index on store_nodes  (cost=0.00..5.95 rows=1 width=96) (actual time=0.027..0.084 rows=6 loops=1)
~                                       Index Cond: ((("path")::text ~>=~ '/sites/broadsat/news/'::character varying) AND (("path")::text ~<~ '/sites/broadsat/news0'::character varying))
~                                       Filter: (("path")::text ~~ '/sites/broadsat/news/%'::text)
~                                 ->  Index Scan using store_objects_pkey on store_objects  (cost=0.00..5.43 rows=1 width=672) (actual time=0.012..0.020 rows=1 loops=6)
~                                       Index Cond: (store_objects.id = "outer".object)
~                           ->  Hash  (cost=1.74..1.74 rows=2 width=11) (actual time=0.093..0.093 rows=0 loops=1)
~                                 ->  Seq Scan on store_types  (cost=0.00..1.74 rows=2 width=11) (actual time=0.029..0.054 rows=1 loops=1)
~                                       Filter: ((implements)::text = 'particle'::text)
~                     ->  Hash  (cost=1.75..1.75 rows=7 width=8) (actual time=0.182..0.182 rows=0 loops=1)
~                           ->  Seq Scan on store_prop_article  (cost=0.00..1.75 rows=7 width=8) (actual time=0.041..0.121 rows=7 loops=1)
~                                 Filter: ((ar_start <= 1092924200) AND (ar_end >= 1092924200) AND ((ar_display)::text = 'default'::text))
~ Total runtime: 1.358 ms
(21 rows)

|>With index and default stat 1000:      1.6 ms

ariadne=# explain analyze execute test_ariadne;
~                                                                                                          QUERY PLAN
- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
~ Limit  (cost=14.94..14.96 rows=1 width=760) (actual time=1.346..1.445 rows=3 loops=1)
~   ->  Unique  (cost=14.94..14.96 rows=1 width=760) (actual time=1.329..1.393 rows=3 loops=1)
~         ->  Sort  (cost=14.94..14.94 rows=1 width=760) (actual time=1.317..1.335 rows=3 loops=1)
~               Sort Key: store_nodes.parent, store_nodes.priority, store_nodes."path", store_objects.id, store_objects."type", store_objects.object, date_part('epoch'::text, store_objects.lastchanged), store_objects.vtype
~               ->  Hash Join  (cost=1.77..14.93 rows=1 width=760) (actual time=0.663..1.249 rows=3 loops=1)
~                     Hash Cond: ("outer".id = "inner".object)
~                     ->  Nested Loop  (cost=0.00..13.14 rows=1 width=768) (actual time=0.268..0.936 rows=5 loops=1)
~                           Join Filter: (("outer".vtype)::text = ("inner"."type")::text)
~                           ->  Nested Loop  (cost=0.00..11.39 rows=1 width=768) (actual time=0.070..0.412 rows=6 loops=1)
~                                 ->  Index Scan using test_index on store_nodes  (cost=0.00..5.95 rows=1 width=96) (actual time=0.027..0.093 rows=6 loops=1)
~                                       Index Cond: ((("path")::text ~>=~ '/sites/broadsat/news/'::character varying) AND (("path")::text ~<~ '/sites/broadsat/news0'::character varying))
~                                       Filter: (("path")::text ~~ '/sites/broadsat/news/%'::text)
~                                 ->  Index Scan using store_objects_pkey on store_objects  (cost=0.00..5.43 rows=1 width=672) (actual time=0.013..0.020 rows=1 loops=6)
~                                       Index Cond: (store_objects.id = "outer".object)
~                           ->  Seq Scan on store_types  (cost=0.00..1.74 rows=1 width=11) (actual time=0.025..0.051 rows=1 loops=6)
~                                 Filter: ((implements)::text = 'particle'::text)
~                     ->  Hash  (cost=1.75..1.75 rows=7 width=8) (actual time=0.181..0.181 rows=0 loops=1)
~                           ->  Seq Scan on store_prop_article  (cost=0.00..1.75 rows=7 width=8) (actual time=0.040..0.122 rows=7 loops=1)
~                                 Filter: ((ar_start <= 1092924200) AND (ar_end >= 1092924200) AND ((ar_display)::text = 'default'::text))
~ Total runtime: 1.616 ms
(20 rows)



| Could we see EXPLAIN ANALYZE EXECUTE output for each case?
|

See above.


BTW I dont know if this is a known issue:

After the prepare statement:

ariadne=# drop index test_index;
DROP INDEX
ariadne=# explain analyze execute test_ariadne;
ERROR:  could not open relation with OID 53695




Regards
Gaetano Mendola











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From pgsql-performance-owner@postgresql.org  Fri Aug 20 17:04:28 2004
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To: Gaetano Mendola 
Cc: "pgsql-performance@postgresql.org" 
Subject: Re: using an index worst performances 
In-reply-to: <4126545C.5020203@bigfoot.com> 
References:  <4124ECF3.6040901@archonet.com>
	<412505F6.6080000@bigfoot.com>
	<4125565D.3060008@familyhealth.com.au>
	<4125C657.7000702@bigfoot.com> <1093006549.75942.61.camel@jester>
	<41261E41.3080204@bigfoot.com> <22026.1093018762@sss.pgh.pa.us>
	<4126545C.5020203@bigfoot.com>
Comments: In-reply-to Gaetano Mendola 
	message dated "Fri, 20 Aug 2004 21:43:24 +0200"
Date: Fri, 20 Aug 2004 16:04:01 -0400
Message-ID: <1977.1093032241@sss.pgh.pa.us>
From: Tom Lane 
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Gaetano Mendola  writes:
> Tom Lane wrote:
> | Could we see EXPLAIN ANALYZE EXECUTE output for each case?

> [snip]
> See above.

Okay, so the issue here is choosing between a nestloop or a hash join
that have very nearly equal estimated costs:

> ~               ->  Hash Join  (cost=1.74..46.14 rows=1 width=760) (actual time=0.342..0.825 rows=3 loops=1)
> ~                     Hash Cond: (("outer".vtype)::text = ("inner"."type")::text)

> ~               ->  Nested Loop  (cost=0.00..46.13 rows=1 width=760) (actual time=0.278..0.933 rows=3 loops=1)
> ~                     Join Filter: (("outer".vtype)::text = ("inner"."type")::text)

In the indexed case it's the same choice, but at a different level of joining:

> ~                     ->  Hash Join  (cost=1.74..13.15 rows=1 width=768) (actual time=0.281..0.651 rows=5 loops=1)
> ~                           Hash Cond: (("outer".vtype)::text = ("inner"."type")::text)

> ~                     ->  Nested Loop  (cost=0.00..13.14 rows=1 width=768) (actual time=0.268..0.936 rows=5 loops=1)
> ~                           Join Filter: (("outer".vtype)::text = ("inner"."type")::text)

With only 0.01 unit of difference in the costs, it's perfectly plausible
for a change in the statistics to change the estimated cost just enough
to give one plan or the other the edge in estimated cost.

Given that the runtimes are in fact pretty similar, it doesn't bother me
that the planner is estimating them as essentially identical.

			regards, tom lane

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From: "Danilo Mota" 
To: 
Subject: Query Performance
Date: Fri, 20 Aug 2004 21:03:54 -0300
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Hi all,
 
 the following query is working well without the AND on WHERE clause, so
I need suggestions about how could I rewrite the query to get the same
result with less cost of time and resources.
 
I've already created indexes on all foreign key columns.
 
Thanks in advance.
 
Danilo Mota
 
========================================================================
============
    SELECT
        sn.notafiscalnumero,
        sn.notafiscalserie,
        CASE sn.notafiscaldata WHEN '00000000' THEN NULL ELSE
to_date(sn.notafiscaldata,'YYYYMMDD') END,
        sn.modalidade,
        rcm.pkclientemarca,
        sn.notafiscalvalor/100,
        sn.entrada/100,
        sn.cliente
    FROM r_clientemarca AS rcm
    INNER JOIN r_cliente AS rc ON rc.pkcliente = rcm.fkcliente
    INNER JOIN sav_cliente_lg AS sc ON sc.cpfcnpj = rc.cpfcnpj
    INNER JOIN sav_nota_lg AS sn ON sn.cliente = sc.codigo
    WHERE rcm.fkmarca = 1
      AND sn.notafiscalnumero||sn.notafiscalserie||sn.cliente NOT IN (
SELECT numero||serie||codigo
 
FROM r_contrato AS rcon
 
WHERE savfonte = 'lg')
 
========================================================================
============
 
 
                                                         TABLES
------------------------------------------------------------------------
-----------------------------------------------------
r_cliente: 75820 records
r_clientemarca: 97719 records
r_contrato: 782058 records
sav_cliente_lg: 65671 records
sav_nota_lg: 297329 rcords
                                                         MY SERVER
------------------------------------------------------------------------
-----------------------------------------------------
Pentium 4 2.4 GHz
1 GB RAM
36 GB SCSI
Postgresql 7.4.2
 
                                                         POSTGRESQL.CONF
------------------------------------------------------------------------
-----------------------------------------------------
shared_buffers = 7800
sort_mem = 4096
checkpoint_segments = 5  
effective_cache_size = 12000
cpu_operator_cost = 0.0015
stats_start_collector = false
 
                                                         QUERY PLAN
------------------------------------------------------------------------
-----------------------------------------------------
 Hash Join  (cost=27149.61..3090289650.24 rows=128765 width=4)
   Hash Cond: ("outer".cliente = "inner".codigo)
   ->  Seq Scan on sav_nota_lg sn  (cost=0.00..3090258517.99 rows=148665
width=8)
         Filter: (NOT (subplan))
         SubPlan
           ->  Seq Scan on r_contrato rcon  (cost=0.00..20362.47
rows=282845 width=19)
                 Filter: ((savfonte)::text = 'lg'::text)
   ->  Hash  (cost=26869.29..26869.29 rows=56880 width=4)
         ->  Hash Join  (cost=22473.95..26869.29 rows=56880 width=4)
               Hash Cond: ("outer".fkcliente = "inner".pkcliente)
               ->  Index Scan using ix_r_clientemarca_fkmarca on
r_clientemarca rcm  (cost=0.00..2244.46 rows=65665 width=4)
                     Index Cond: (fkmarca = 1)
               ->  Hash  (cost=22118.44..22118.44 rows=65672 width=8)
                     ->  Hash Join  (cost=6613.22..22118.44 rows=65672
width=8)
                           Hash Cond: (("outer".cpfcnpj)::text =
("inner".cpfcnpj)::text)
                           ->  Seq Scan on r_cliente rc
(cost=0.00..12891.16 rows=75816 width=23)
                           ->  Hash  (cost=6129.71..6129.71 rows=65671
width=23)
                                 ->  Seq Scan on sav_cliente_lg sc
(cost=0.00..6129.71 rows=65671 width=23)
 
 

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Hi all,=




 <=
/font>



 th=
e following
query is working well without the AND on WHERE clause, so I need suggestions
about how could I rewrite the query to get the same result with less cost of
time and resources.



 



I’ve already created indexes on all foreign key
columns.



 



Thanks in advance.



 



Danilo <=
span
class=3DSpellE>Mota



 



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=3D



    SELECT



        sn.notafiscalnumero,



        sn.notafiscalserie,



        CASE =
sn.notafiscaldata WHEN '00000000' THEN NULL ELSE to_date(sn.notafiscaldata,'YYYYMMDD') END,<=
/font>



        sn.mo=
dalidade,



        rcm.p=
kclientemarca,



        sn.no=
tafiscalvalor/100,



        sn.entrada/100,



        sn.cliente



    FROM r_clientemarca AS=
 rcm



    INNER JOIN =
r_cliente AS rc
ON rc.pkcliente =3D rcm.fk=
cliente



   
INNER JOIN sav_cliente_lg AS sc ON sc.cpfcnpj =3D rc.cpfcnpj=




    INNER
JOIN sav_nota_lg AS sn ON sn.cliente =
=3D sc.codigo



    WHERE rcm.fkmarca =3D 1


      AND sn.notafiscalnumero||sn.notafiscalserie||sn.cliente N=
OT IN ( SELECT numero||serie||codigo



        =
            &nb=
sp;            =
            &nb=
sp;            =
           
        =
            &nb=
sp;         FROM
r_contrato AS rcon



        =
            &nb=
sp;            =
            &nb=
sp;    
        =
                   =
            &nb=
sp;         WHERE
savfonte =3D 'lg')



 <=
/font>



=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D



 <=
/font>



 



        =
            &nb=
sp;            =
            &nb=
sp;          
TABLES



-------------------------=
---------------------------------------------------------------------------=
-------------------------



r_cliente: 75820 records<=
o:p>



r_clientemarca: 97719 rec=
ords



r_contrato: 782058 record=
s



sav_cliente_lg: 65671 rec=
ords



sav_nota_lg: 297329 rcord=
s



        =
            &nb=
sp;            =
            &nb=
sp;          
MY SERVER



--------------------------------------------------------=
---------------------------------------------------------------------<=
/o:p>



Pentium 4 2.4 GHz



1 GB RAM



36 GB SCSI



Postgresql 7.4.2



 <=
/font>



        =
            &nb=
sp;            =
            &nb=
sp;          
POSTGRESQL.CONF



--------------------------------------------------------=
---------------------------------------------------------------------<=
/o:p>



shared_buffers =
=3D 7800



sort_mem<=
font
size=3D2 face=3DArial> =
=3D 4096



checkpoint_segments =
=3D 5  



effective_cache_size =
=3D 12000



cpu_operator_cost =
=3D 0.0015



stats_start_collector =
=3D false



 



        =
            &nb=
sp;            =
            &nb=
sp;          
QUERY PLAN



--------------------------------------------------------=
---------------------------------------------------------------------<=
/o:p>



 Hash Join  (co=
st=3D27149.61..3090289650.24
rows=3D128765 width=3D4)



   Has=
h Cond: ("outer".cliente=

=3D "inner".codigo)=




   ->  Seq Scan on sav_nota_lg sn 
(cost=3D0.00..3090258517.99 rows=3D148665 width=3D8)



        
Filter: (NOT (subplan))



        
SubPlan



        =
  
->  Seq Scan on r_contrato rcon 
(cost=3D0.00..20362.47 rows=3D282845 width=3D19)



        =
        
Filter: ((savfonte):=
:text
=3D 'lg'::text)



   ->  Hash  (cost=3D26869.29..26869.29 rows=3D=
56880
width=3D4)



        
->  Hash
Join  (cost=3D22473.95..26869.=
29
rows=3D56880 width=3D4)



        =
      
Hash Cond: ("o=
uter".fkcliente
=3D "inner".pkcliente)



        =
      
-> 
Index Scan using ix_r_clientemarca_fkmar=
ca
on r_clientemarca rcm  (cost=3D0.00..2244.46 rows=3D65665=
 width=3D4)



        =
            
Index Cond: (fkmarc=
a
=3D 1)



        =
      
->  Hash  (cost=3D22118.44..22118.44 rows=3D=
65672
width=3D8)



               =
      ->  Hash
Join  (cost=3D6613.22..22118.44
rows=3D65672 width=3D8)



        =
            &nb=
sp;     
Hash Cond: (("=
outer".cpfcnpj)::text =3D ("inner".cpfc=
npj)::text)



        =
            &nb=
sp;     
->  Seq Scan on r_cliente rc 
(cost=3D0.00..12891.16 rows=3D75816 width=3D23)



        =
            &nb=
sp;     
->  Hash  (cost=3D6129.71..6129.71 rows=3D65=
671
width=3D23)



        =
            &nb=
sp;           
->  Seq Scan on sav_cliente_l=
g
sc  (cost=3D0.00..6129.71 rows=
=3D65671
width=3D23)



 



 









------=_NextPart_000_0001_01C486F9.3449FFA0--



From pgsql-performance-owner@postgresql.org  Fri Aug 20 21:59:52 2004
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Date: Fri, 20 Aug 2004 18:02:48 -0700
From: Brad Bulger 
Organization: The Madfish Group
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To: dmota@nexen.com.br
Cc: pgsql-performance@postgresql.org
Subject: Re: Query Performance
References: <000001c48712$599737a0$8afea8c0@nexen.lan>
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Have you tried

AND (sn.notafiscalnumero, sn.notafiscalserie, sn.cliente) NOT IN (
   SELECT numero, serie, codigo FROM r_contrato WHERE savfonte = 'lg')

or

and not exists(select true from r_contrato where savfonte = 'lg' and numero = 
sn.notafiscalnumero and serie = sn.notafiscalserie and codigo = sn.cliente)


Danilo Mota wrote:

> Hi all,
> 
>  
> 
>  the following query is working well without the AND on WHERE clause, so 
> I need suggestions about how could I rewrite the query to get the same 
> result with less cost of time and resources.
> 
>  
> 
> I�ve already created indexes on all foreign key columns.
> 
>  
> 
> Thanks in advance.
> 
>  
> 
> Danilo Mota
> 
>  
> 
> ====================================================================================
> 
>     SELECT
> 
>         sn.notafiscalnumero,
> 
>         sn.notafiscalserie,
> 
>         CASE sn.notafiscaldata WHEN '00000000' THEN NULL ELSE 
> to_date(sn.notafiscaldata,'YYYYMMDD') END,
> 
>         sn.modalidade,
> 
>         rcm.pkclientemarca,
> 
>         sn.notafiscalvalor/100,
> 
>         sn.entrada/100,
> 
>         sn.cliente
> 
>     FROM r_clientemarca AS rcm
> 
>     INNER JOIN r_cliente AS rc ON rc.pkcliente = rcm.fkcliente
> 
>     INNER JOIN sav_cliente_lg AS sc ON sc.cpfcnpj = rc.cpfcnpj
> 
>     INNER JOIN sav_nota_lg AS sn ON sn.cliente = sc.codigo
> 
>     WHERE rcm.fkmarca = 1
> 
>       AND sn.notafiscalnumero||sn.notafiscalserie||sn.cliente NOT IN ( 
> SELECT numero||serie||codigo
> 
>                                                                       
>                               FROM r_contrato AS rcon
> 
>                                                    
>                                                  WHERE savfonte = 'lg')
> 
>  
> 
> ====================================================================================
> 
>  
> 
>  
> 
>                                                          TABLES
> 
> -----------------------------------------------------------------------------------------------------------------------------
> 
> r_cliente: 75820 records
> 
> r_clientemarca: 97719 records
> 
> r_contrato: 782058 records
> 
> sav_cliente_lg: 65671 records
> 
> sav_nota_lg: 297329 rcords
> 
>                                                          MY SERVER
> 
> -----------------------------------------------------------------------------------------------------------------------------
> 
> Pentium 4 2.4 GHz
> 
> 1 GB RAM
> 
> 36 GB SCSI
> 
> Postgresql 7.4.2
> 
>  
> 
>                                                          POSTGRESQL.CONF
> 
> -----------------------------------------------------------------------------------------------------------------------------
> 
> shared_buffers = 7800
> 
> sort_mem = 4096
> 
> checkpoint_segments = 5 
> 
> effective_cache_size = 12000
> 
> cpu_operator_cost = 0.0015
> 
> stats_start_collector = false
> 
>  
> 
>                                                          QUERY PLAN
> 
> -----------------------------------------------------------------------------------------------------------------------------
> 
>  Hash Join  (cost=27149.61..3090289650.24 rows=128765 width=4)
> 
>    Hash Cond: ("outer".cliente = "inner".codigo)
> 
>    ->  Seq Scan on sav_nota_lg sn  (cost=0.00..3090258517.99 rows=148665 
> width=8)
> 
>          Filter: (NOT (subplan))
> 
>          SubPlan
> 
>            ->  Seq Scan on r_contrato rcon  (cost=0.00..20362.47 
> rows=282845 width=19)
> 
>                  Filter: ((savfonte)::text = 'lg'::text)
> 
>    ->  Hash  (cost=26869.29..26869.29 rows=56880 width=4)
> 
>          ->  Hash Join  (cost=22473.95..26869.29 rows=56880 width=4)
> 
>                Hash Cond: ("outer".fkcliente = "inner".pkcliente)
> 
>                ->  Index Scan using ix_r_clientemarca_fkmarca on 
> r_clientemarca rcm  (cost=0.00..2244.46 rows=65665 width=4)
> 
>                      Index Cond: (fkmarca = 1)
> 
>                ->  Hash  (cost=22118.44..22118.44 rows=65672 width=8)
> 
>                      ->  Hash Join  (cost=6613.22..22118.44 rows=65672 
> width=8)
> 
>                            Hash Cond: (("outer".cpfcnpj)::text = 
> ("inner".cpfcnpj)::text)
> 
>                            ->  Seq Scan on r_cliente rc  
> (cost=0.00..12891.16 rows=75816 width=23)
> 
>                            ->  Hash  (cost=6129.71..6129.71 rows=65671 
> width=23)
> 
>                                  ->  Seq Scan on sav_cliente_lg sc  
> (cost=0.00..6129.71 rows=65671 width=23)
> 
>  
> 
>  
> 

From pgsql-performance-owner@postgresql.org  Sun Aug 22 07:08:58 2004
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Date: Sun, 22 Aug 2004 12:08:47 +0200
From: Gaetano Mendola 
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To: "pgsql-performance@postgresql.org" 
Subject: Re: using an index worst performances
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	<412505F6.6080000@bigfoot.com>
	<4125565D.3060008@familyhealth.com.au>	
	<4125C657.7000702@bigfoot.com> <1093006549.75942.61.camel@jester>	
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Rod Taylor wrote:

|>>What are the times without the index, with the index and with the higher
|>>statistics value when using a prepared query?
|>
|>Using a prepared query:
|>
|>Without index and default stat 10 :    1.12 ms
|>Without index and default stat 1000 :  1.25 ms
|>With index and default stat 10:        1.35 ms
|>With index and default stat 1000:      1.6 ms
|>
|>that values are the average obtained after the very first one,
|>on 20 execution.
|
|
| Most interesting. And the plans chosen with the 2 different default stat
| targets are the same? Sorry if I missed the post indicating they were.
|
| If the plans are the same, it would be interesting to get a profile on
| the 2 different cases with that index in place across 100k iterations of
| the prepared query.

Do you have an advice on the profiler to use ?


Regards
Gaetano Mendola



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From pgsql-performance-owner@postgresql.org  Mon Aug 23 11:33:24 2004
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	Mon, 23 Aug 2004 07:33:10 PDT
Date: Mon, 23 Aug 2004 07:33:10 -0700 (PDT)
From: my thi ho 
Subject: postgresql 8.0 beta - fail to collect statsistic
To: pgsql-performance@postgresql.org
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Hi, 
I got this error message: 

LOG:  could not create IPv6 socket: Address family not
supported by protocol
LOG:  could not bind socket for statistics collector:
Cannot assign requested address
LOG:  disabling statistics collector for lack of
working socket
LOG:  database system was shut down at 2004-08-24
00:07:21 EST
LOG:  checkpoint record is at 0/A45360
LOG:  redo record is at 0/A45360; undo record is at
0/0; shutdown TRUE
LOG:  next transaction ID: 492; next OID: 17228
LOG:  database system is ready


I already have a look at pgstat.c but dun know where
to fix it ( with 7.3.1 i just change the line
inet_aton("127.0.0.1", &(pgStatAddr.sin_addr));
to inet_aton("", &(pgStatAddr.sin_addr)); then
it works
this is the config of the computer:
$ uname -a
Linux grieg 2.4.26-general-64G #1 SMP Tue May 18
09:31:45 EST 2004 i686 GNU/Linux

Any help would be really appreciated.
MT 


	
		
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From pgsql-performance-owner@postgresql.org  Mon Aug 23 16:01:50 2004
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	Mon, 23 Aug 2004 15:01:45 -0400 (EDT)
To: my thi ho 
Cc: pgsql-performance@postgresql.org
Subject: Re: postgresql 8.0 beta - fail to collect statsistic 
In-reply-to: <20040823143310.93307.qmail@web54104.mail.yahoo.com> 
References: <20040823143310.93307.qmail@web54104.mail.yahoo.com>
Comments: In-reply-to my thi ho 
	message dated "Mon, 23 Aug 2004 07:33:10 -0700"
Date: Mon, 23 Aug 2004 15:01:45 -0400
Message-ID: <9889.1093287705@sss.pgh.pa.us>
From: Tom Lane 
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my thi ho  writes:
> I got this error message: 

> LOG:  could not create IPv6 socket: Address family not
> supported by protocol
> LOG:  could not bind socket for statistics collector:
> Cannot assign requested address
> LOG:  disabling statistics collector for lack of
> working socket

You have a broken networking setup, or possibly a broken DNS setup.
The machine should accept connections to 127.0.0.1 ... if it does not,
find out why not.

> I already have a look at pgstat.c but dun know where
> to fix it ( with 7.3.1 i just change the line
> inet_aton("127.0.0.1", &(pgStatAddr.sin_addr));
> to inet_aton("", &(pgStatAddr.sin_addr)); then
> it works

You were fixing the symptom and not the problem.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Mon Aug 23 18:52:55 2004
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	Mon, 23 Aug 2004 17:52:49 -0400
Subject: Re: postgresql 8.0 beta - fail to collect statsistic
From: Steve Bergman 
To: Tom Lane 
Cc: my thi ho ,
	pgsql-perform 
In-Reply-To: <9889.1093287705@sss.pgh.pa.us>
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	<9889.1093287705@sss.pgh.pa.us>
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Date: Mon, 23 Aug 2004 16:52:47 -0500
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If IPv6 doesn't work, shouldn't it fall back to IPv4, or check IPv4
first, or something?  Just wondering.

-Steve Bergman


From pgsql-performance-owner@postgresql.org  Mon Aug 23 19:30:52 2004
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To: Steve Bergman 
Cc: my thi ho ,
	pgsql-perform 
Subject: Re: postgresql 8.0 beta - fail to collect statsistic 
In-reply-to: <1093297967.5512.3.camel@voyager.localdomain> 
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Comments: In-reply-to Steve Bergman 
	message dated "Mon, 23 Aug 2004 16:52:47 -0500"
Date: Mon, 23 Aug 2004 18:30:45 -0400
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From: Tom Lane 
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Steve Bergman  writes:
> If IPv6 doesn't work, shouldn't it fall back to IPv4,

It does.  That was all debugged in 7.4 --- we have not seen any cases
since 7.4 beta in which failures of this kind did not mean a
misconfigured networking setup.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Mon Aug 23 21:02:27 2004
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From: andrew@pillette.com
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Subject: How do I see what triggers are called on cascade?
To: pgsql-performance@postgresql.org
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I'm still having trouble with slow cascading DELETEs. What commands can I issue to see the sequence of events that occurs after I execute 

DELETE FROM x WHERE p;

so that I can see if indexes being used correctly, or I have a constraint I don't want, etc.

From pgsql-performance-owner@postgresql.org  Mon Aug 23 23:50:47 2004
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To: andrew@pillette.com
Cc: pgsql-performance@postgresql.org
Subject: Re: How do I see what triggers are called on cascade? 
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Comments: In-reply-to andrew@pillette.com
	message dated "Mon, 23 Aug 2004 17:02:18 -0700"
Date: Mon, 23 Aug 2004 22:50:41 -0400
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From: Tom Lane 
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andrew@pillette.com writes:
> I'm still having trouble with slow cascading DELETEs. What commands can I issue to see the sequence of events that occurs after I execute 
> DELETE FROM x WHERE p;
> so that I can see if indexes being used correctly, or I have a constraint I don't want, etc.

I'd suggest starting a fresh backend, turning on log_statement, and then
issuing the DELETE.  log_statement will log the queries generated by the
foreign-key triggers ... but only the first time through, because those
triggers cache the query plans.

The queries you will see will be parameterized (they'll use $1,$2,etc).
You can use PREPARE and EXPLAIN ANALYZE EXECUTE to investigate what sort
of plans result.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Tue Aug 24 02:15:54 2004
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	Mon, 23 Aug 2004 22:08:42 PDT
Date: Mon, 23 Aug 2004 22:08:42 -0700 (PDT)
From: my ho 
Subject: Re: postgresql performance with multimedia
To: Jan Wieck , my thi ho 
Cc: pgsql-performance@postgresql.org
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--- Jan Wieck  wrote:

> On 8/17/2004 8:44 PM, my thi ho wrote:
> 
> > Hi,
> > I am working on a project which explore postgresql
> to
> > store multimedia data.
> > In details,  i am trying to work with the buffer
> > management part of postgres source code. And try
> to
> > improve the performance. I had search on the web
> but
> > could not find much usefull information. 
> 
> What version of PostgreSQL are you looking at? Note
> that the buffer 
> cache replacement strategy was completely changed
> for version 8.0, which 
> is currently in BETA test. A description of the
> algorithm can be found 
> in the README file in src/backend/storage/bufmgr.

oki, Thanks for the information. I have a look at 8.0
beta, but cannot start the statistic collector. (I had
post this err message before for help, but havent
really got any clue to fix it)
> LOG:  could not create IPv6 socket: Address family
not
> supported by protocol
> LOG:  could not bind socket for statistics
collector:
> Cannot assign requested address
> LOG:  disabling statistics collector for lack of
> working socket

btw, what i want to ask here is does postgreSQL have
any kind of read-ahead buffer implemented? 'cos it
would be useful in multimedia case when we always scan
the large table for continous data.
Thanks 
Ho




	
		
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From pgsql-performance-owner@postgresql.org  Tue Aug 24 05:33:03 2004
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Date: Tue, 24 Aug 2004 10:32:40 +0200
From: Stef 
To: pgsql-performance@postgresql.org
Subject: Query kills machine.
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This is a multi-part message in MIME format.

--Multipart=_Tue__24_Aug_2004_10_32_40_+0200_maLgIszoscYKY=nc
Content-Type: text/plain; charset=US-ASCII
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Hi all,

I've attached all the query in query.sql

I'm using postgres 7.3.4 on Linux version 2.4.26-custom 
( /proc/sys/vm/overcommit_memory  = 0  this time ) 

free :
             total       used       free     shared    buffers     cached
Mem:       1810212    1767384      42828          0       5604    1663908
-/+ buffers/cache:      97872    1712340
Swap:       505912     131304     374608

After I rebuilt the database, the query was fast (28255.12 msec).
After one night's insertion into the tables that the query select from,
the query all of a sudden uses up all resources , and the kernel
starts swapping, and I haven't seen the query actually finish when
this happens. I did vacuum analyze AND reindex, but that doesn't 
help.

I attached the explain analyze of the query before this happens, and
the explain plan from when it actually happens that the query doesn't finish.

The one noticeable difference, was that before, it used merge joins, and
after, it used hash joins.

When the query was slow, I tried to : set enable_hashjoin to off
for this query, and the query finished relatively fast again (316245.16 msec)

I attached the output of that explain analyze as well, as well as the postgres
settings.

Can anyone shed some light on what's happening here. I can't figure it out.

Kind Regards
Stefan 

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 Aggregate  (cost=87597.84..89421.82 rows=2702 width=484) (actual time=22727.88..28164.74 rows=12040 loops=1)
   Filter: ((((sum(qty_on_hand) + sum(qty_in_goods)) - sum(qty_dp)) - sum(qty_out_goods)) < 0::numeric)
   ->  Group  (cost=87597.84..88003.17 rows=27022 width=484) (actual time=22727.45..23242.01 rows=42705 loops=1)
         ->  Sort  (cost=87597.84..87665.40 rows=27022 width=484) (actual time=22727.43..22756.74 rows=42705 loops=1)
               Sort Key: s.sku, s.stktype_code, i.sku_descr, br.cluster_code, br.cluster_descr
               ->  Merge Join  (cost=84388.96..85608.78 rows=27022 width=484) (actual time=20303.41..21814.25 rows=42705 loops=1)
                     Merge Cond: (("outer".group_code = "inner".group_code) AND ("outer".sku = "inner".sku))
                     ->  Sort  (cost=64472.34..64489.67 rows=6930 width=388) (actual time=16503.56..16530.23 rows=42705 loops=1)
                           Sort Key: s.group_code, os.sku
                           ->  Merge Join  (cost=63006.13..64030.25 rows=6930 width=388) (actual time=14394.48..15794.71 rows=42705 loops=1)
                                 Merge Cond: (("outer".cluster_brn = "inner".cluster_code) AND ("outer".sku = "inner".sku))
                                 ->  Index Scan using old_sku_uidx1 on old_sku os  (cost=0.00..797.79 rows=17799 width=64) (actual time=0.02..47.66 rows=17799 loops=1)
                                 ->  Sort  (cost=63006.13..63045.07 rows=15574 width=324) (actual time=14393.77..14556.50 rows=132703 loops=1)
                                       Sort Key: br.cluster_code, s.sku
                                       ->  Merge Join  (cost=61645.75..61921.64 rows=15574 width=324) (actual time=4862.56..6078.94 rows=132703 loops=1)
                                             Merge Cond: ("outer".brn_code = "inner".brn_code)
                                             ->  Sort  (cost=61587.79..61626.73 rows=15574 width=228) (actual time=4859.23..5043.43 rows=132703 loops=1)
                                                   Sort Key: s.brn_code
                                                   ->  Index Scan using stmst_sku_idx4 on stmst_sku s  (cost=0.00..60503.30 rows=15574 width=228) (actual time=0.07..1078.30 rows=132703 loops=1)
                                                         Index Cond: (fpp_code = '200408'::text)
                                             ->  Sort  (cost=57.96..59.62 rows=667 width=96) (actual time=3.26..91.93 rows=133005 loops=1)
                                                   Sort Key: br.brn_code
                                                   ->  Seq Scan on master_branch_descr br  (cost=0.00..26.67 rows=667 width=96) (actual time=0.02..1.13 rows=667 loops=1)
                     ->  Sort  (cost=19916.61..20306.53 rows=155968 width=96) (actual time=3797.71..3914.26 rows=184223 loops=1)
                           Sort Key: i.group_code, i.sku
                           ->  Seq Scan on master_sku_descr i  (cost=0.00..6463.68 rows=155968 width=96) (actual time=0.01..293.74 rows=155968 loops=1)
   SubPlan
     ->  Aggregate  (cost=6.02..6.02 rows=1 width=8) (actual time=0.04..0.04 rows=1 loops=14456)
           ->  Index Scan using gir_oustanding_idx1 on gir_outstanding  (cost=0.00..6.01 rows=1 width=8) (actual time=0.03..0.03 rows=0 loops=14456)
                 Index Cond: ((cluster_brn = $0) AND (sku = $1) AND (stktype_code = $2))
     ->  Aggregate  (cost=6.02..6.02 rows=1 width=8) (actual time=0.04..0.04 rows=1 loops=14456)
           ->  Index Scan using gir_oustanding_idx1 on gir_outstanding  (cost=0.00..6.01 rows=1 width=8) (actual time=0.03..0.03 rows=0 loops=14456)
                 Index Cond: ((cluster_brn = $0) AND (sku = $1) AND (stktype_code = $2))
     ->  Aggregate  (cost=6.02..6.02 rows=1 width=8) (actual time=0.03..0.03 rows=1 loops=12031)
           ->  Index Scan using gir_oustanding_idx1 on gir_outstanding  (cost=0.00..6.01 rows=1 width=8) (actual time=0.03..0.03 rows=0 loops=12031)
                 Index Cond: ((cluster_brn = $0) AND (sku = $1) AND (stktype_code = $2))
     ->  Aggregate  (cost=11.96..11.96 rows=1 width=82) (actual time=0.16..0.16 rows=1 loops=14456)
           ->  Nested Loop  (cost=0.00..11.95 rows=1 width=82) (actual time=0.08..0.15 rows=3 loops=14456)
                 ->  Index Scan using stmst_sku_idx3 on stmst_sku k  (cost=0.00..6.02 rows=1 width=50) (actual time=0.06..0.08 rows=3 loops=14456)
                       Index Cond: ((fpp_code = '200408'::text) AND (sku = $1) AND (stktype_code = $2))
                 ->  Index Scan using master_branch_descr_pkey on master_branch_descr b  (cost=0.00..5.92 rows=1 width=32) (actual time=0.02..0.02 rows=1 loops=42705)
                       Index Cond: ("outer".brn_code = b.brn_code)
                       Filter: ((brn_code <> cluster_code) AND (cluster_code = $0))
 Total runtime: 28255.12 msec
(44 rows)


--Multipart=_Tue__24_Aug_2004_10_32_40_+0200_maLgIszoscYKY=nc
Content-Type: text/plain;
 name="explain_after.txt"
Content-Disposition: attachment;
 filename="explain_after.txt"
Content-Transfer-Encoding: 7bit

 Aggregate  (cost=316107.28..316114.91 rows=11 width=322)
   Filter: ((((sum(qty_on_hand) + sum(qty_in_goods)) - sum(qty_dp)) - sum(qty_out_goods)) < 0::numeric)
   ->  Group  (cost=316107.28..316108.98 rows=113 width=322)
         ->  Sort  (cost=316107.28..316107.57 rows=113 width=322)
               Sort Key: s.sku, s.stktype_code, i.sku_descr, br.cluster_code, br.cluster_descr
               ->  Hash Join  (cost=308622.49..316103.43 rows=113 width=322)
                     Hash Cond: ("outer".sku = "inner".sku)
                     Join Filter: ("inner".group_code = "outer".group_code)
                     ->  Seq Scan on master_sku_descr i  (cost=0.00..6467.08 rows=156008 width=96)
                     ->  Hash  (cost=308618.04..308618.04 rows=1781 width=226)
                           ->  Hash Join  (cost=1698.78..308618.04 rows=1781 width=226)
                                 Hash Cond: ("outer".sku = "inner".sku)
                                 Join Filter: ("outer".brn_code = "inner".brn_code)
                                 ->  Seq Scan on stmst_sku s  (cost=0.00..284677.69 rows=356150 width=106)
                                       Filter: (fpp_code = '200408'::text)
                                 ->  Hash  (cost=1550.41..1550.41 rows=59347 width=120)
                                       ->  Merge Join  (cost=57.89..1550.41 rows=59347 width=120)
                                             Merge Cond: ("outer".cluster_brn = "inner".cluster_code)
                                             ->  Index Scan using old_sku_uidx1 on old_sku os  (cost=0.00..702.79 rows=17822 width=24)
                                             ->  Sort  (cost=57.89..59.56 rows=666 width=96)
                                                   Sort Key: br.cluster_code
                                                   ->  Seq Scan on master_branch_descr br  (cost=0.00..26.66 rows=666 width=96)
   SubPlan
     ->  Aggregate  (cost=23.73..23.73 rows=1 width=8)
           ->  Index Scan using gir_oustanding_idx1 on gir_outstanding  (cost=0.00..23.70 rows=6 width=8)
                 Index Cond: ((cluster_brn = $0) AND (sku = $1) AND (stktype_code = $2))
     ->  Aggregate  (cost=23.73..23.73 rows=1 width=8)
           ->  Index Scan using gir_oustanding_idx1 on gir_outstanding  (cost=0.00..23.70 rows=6 width=8)
                 Index Cond: ((cluster_brn = $0) AND (sku = $1) AND (stktype_code = $2))
     ->  Aggregate  (cost=23.73..23.73 rows=1 width=8)
           ->  Index Scan using gir_oustanding_idx1 on gir_outstanding  (cost=0.00..23.70 rows=6 width=8)
                 Index Cond: ((cluster_brn = $0) AND (sku = $1) AND (stktype_code = $2))
     ->  Aggregate  (cost=32.16..32.16 rows=1 width=50)
           ->  Merge Join  (cost=32.11..32.15 rows=1 width=50)
                 Merge Cond: ("outer".brn_code = "inner".brn_code)
                 ->  Sort  (cost=14.38..14.39 rows=3 width=32)
                       Sort Key: b.brn_code
                       ->  Index Scan using master_branch_descr_idx6 on master_branch_descr b  (cost=0.00..14.35 rows=3 width=32)
                             Index Cond: (cluster_code = $0)
                             Filter: (brn_code <> cluster_code)
                 ->  Sort  (cost=17.73..17.74 rows=4 width=18)
                       Sort Key: k.brn_code
                       ->  Index Scan using stmst_sku_idx3 on stmst_sku k  (cost=0.00..17.69 rows=4 width=18)
                             Index Cond: ((fpp_code = '200408'::text) AND (sku = $1) AND (stktype_code = $2))
(44 rows)

--Multipart=_Tue__24_Aug_2004_10_32_40_+0200_maLgIszoscYKY=nc
Content-Type: text/plain;
 name="explain_analyze_after_hashjoin_off.txt"
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	filename="explain_analyze_after_hashjoin_off.txt"
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 Aggregate  (cost=354420.02..354427.65 rows=11 width=322) (actual time=246825.06..316125.53 rows=12050 loops=1)
   Filter: ((((sum(qty_on_hand) + sum(qty_in_goods)) - sum(qty_dp)) - sum(qty_out_goods)) < 0::numeric)
   ->  Group  (cost=354420.02..354421.72 rows=113 width=322) (actual time=246701.96..247283.96 rows=42930 loops=1)
         ->  Sort  (cost=354420.02..354420.30 rows=113 width=322) (actual time=246701.94..246736.97 rows=42930 loops=1)
               Sort Key: s.sku, s.stktype_code, i.sku_descr, br.cluster_code, br.cluster_descr
               ->  Merge Join  (cost=354298.16..354416.17 rows=113 width=322) (actual time=245205.55..245634.53 rows=42930 loops=1)
                     Merge Cond: (("outer".brn_code = "inner".brn_code) AND ("outer".cluster_brn = "inner".cluster_code))
                     ->  Sort  (cost=354240.27..354296.76 rows=22595 width=226) (actual time=245179.07..245205.75 rows=42930 loops=1)
                           Sort Key: s.brn_code, os.cluster_brn
                           ->  Merge Join  (cost=348924.92..352606.20 rows=22595 width=226) (actual time=241551.96..244357.21 rows=42930 loops=1)
                                 Merge Cond: ("outer".sku = "inner".sku)
                                 ->  Merge Join  (cost=348924.92..351824.65 rows=22595 width=202) (actual time=241500.21..243397.42 rows=132883 loops=1)
                                       Merge Cond: (("outer".sku = "inner".sku) AND ("outer".group_code = "inner".group_code))
                                       ->  Sort  (cost=329001.17..329891.54 rows=356150 width=106) (actual time=238575.25..238742.16 rows=132883 loops=1)
                                             Sort Key: s.sku, s.group_code
                                             ->  Seq Scan on stmst_sku s  (cost=0.00..284677.69 rows=356150 width=106) (actual time=219190.28..235315.66 rows=132883 loops=1)
                                                   Filter: (fpp_code = '200408'::text)
                                       ->  Sort  (cost=19923.75..20313.77 rows=156008 width=96) (actual time=2924.57..3048.34 rows=185259 loops=1)
                                             Sort Key: i.sku, i.group_code
                                             ->  Seq Scan on master_sku_descr i  (cost=0.00..6467.08 rows=156008 width=96) (actual time=1.62..976.63 rows=156008 loops=1)
                                 ->  Index Scan using old_sku_idx1 on old_sku os  (cost=0.00..398.04 rows=17822 width=24) (actual time=49.45..209.45 rows=46294 loops=1)
                     ->  Sort  (cost=57.89..59.56 rows=666 width=96) (actual time=26.41..54.70 rows=43232 loops=1)
                           Sort Key: br.brn_code, br.cluster_code
                           ->  Seq Scan on master_branch_descr br  (cost=0.00..26.66 rows=666 width=96) (actual time=8.04..24.21 rows=666 loops=1)
   SubPlan
     ->  Aggregate  (cost=23.73..23.73 rows=1 width=8) (actual time=0.06..0.06 rows=1 loops=14481)
           ->  Index Scan using gir_oustanding_idx1 on gir_outstanding  (cost=0.00..23.70 rows=6 width=8) (actual time=0.04..0.05 rows=0 loops=14481)
                 Index Cond: ((cluster_brn = $0) AND (sku = $1) AND (stktype_code = $2))
     ->  Aggregate  (cost=23.73..23.73 rows=1 width=8) (actual time=0.04..0.04 rows=1 loops=14481)
           ->  Index Scan using gir_oustanding_idx1 on gir_outstanding  (cost=0.00..23.70 rows=6 width=8) (actual time=0.03..0.03 rows=0 loops=14481)
                 Index Cond: ((cluster_brn = $0) AND (sku = $1) AND (stktype_code = $2))
     ->  Aggregate  (cost=23.73..23.73 rows=1 width=8) (actual time=0.03..0.03 rows=1 loops=12042)
           ->  Index Scan using gir_oustanding_idx1 on gir_outstanding  (cost=0.00..23.70 rows=6 width=8) (actual time=0.03..0.03 rows=0 loops=12042)
                 Index Cond: ((cluster_brn = $0) AND (sku = $1) AND (stktype_code = $2))
     ->  Aggregate  (cost=32.16..32.16 rows=1 width=50) (actual time=4.53..4.53 rows=1 loops=14481)
           ->  Merge Join  (cost=32.11..32.15 rows=1 width=50) (actual time=4.45..4.52 rows=3 loops=14481)
                 Merge Cond: ("outer".brn_code = "inner".brn_code)
                 ->  Sort  (cost=14.38..14.39 rows=3 width=32) (actual time=3.84..4.01 rows=271 loops=14481)
                       Sort Key: b.brn_code
                       ->  Index Scan using master_branch_descr_idx6 on master_branch_descr b  (cost=0.00..14.35 rows=3 width=32) (actual time=0.02..2.14 rows=564 loops=14481)
                             Index Cond: (cluster_code = $0)
                             Filter: (brn_code <> cluster_code)
                 ->  Sort  (cost=17.73..17.74 rows=4 width=18) (actual time=0.14..0.14 rows=3 loops=14481)
                       Sort Key: k.brn_code
                       ->  Index Scan using stmst_sku_idx3 on stmst_sku k  (cost=0.00..17.69 rows=4 width=18) (actual time=0.08..0.11 rows=3 loops=14481)
                             Index Cond: ((fpp_code = '200408'::text) AND (sku = $1) AND (stktype_code = $2))
 Total runtime: 316245.16 msec
(47 rows)

--Multipart=_Tue__24_Aug_2004_10_32_40_+0200_maLgIszoscYKY=nc
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shared_buffers = 110592
wal_buffers = 400
sort_mem = 30720
vacuum_mem = 10240
checkpoint_segments = 30
commit_delay = 5000
commit_siblings = 100
effective_cache_size = 201413

--Multipart=_Tue__24_Aug_2004_10_32_40_+0200_maLgIszoscYKY=nc
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From pgsql-performance-owner@postgresql.org  Tue Aug 24 06:08:07 2004
X-Original-To: pgsql-performance@postgresql.org
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Date: Tue, 24 Aug 2004 17:08:50 +0800
From: Christopher Kings-Lynne 
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To: Stef 
Cc: pgsql-performance@postgresql.org
Subject: Re: Query kills machine.
References: <20040824103240.4d909777@svb.ucs.co.za>
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For starters,


> ------------------------------------------------------------------------
> 
> shared_buffers = 110592
> wal_buffers = 400
> sort_mem = 30720
> vacuum_mem = 10240
> checkpoint_segments = 30
> commit_delay = 5000
> commit_siblings = 100
> effective_cache_size = 201413

Try more like this:

shared_buffers = 30000
wal_buffers = 
sort_mem = 4096
vacuum_mem = 10240
checkpoint_segments = 30
commit_delay = 
commit_siblings = 
effective_cache_size = 100000

Chris


From pgsql-performance-owner@postgresql.org  Tue Aug 24 08:59:51 2004
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From: Jan Wieck 
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To: my ho 
Cc: pgsql-performance@postgresql.org
Subject: Re: postgresql performance with multimedia
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On 8/24/2004 1:08 AM, my ho wrote:

> --- Jan Wieck  wrote:
> 
>> On 8/17/2004 8:44 PM, my thi ho wrote:
>> 
>> > Hi,
>> > I am working on a project which explore postgresql
>> to
>> > store multimedia data.
>> > In details,  i am trying to work with the buffer
>> > management part of postgres source code. And try
>> to
>> > improve the performance. I had search on the web
>> but
>> > could not find much usefull information. 
>> 
>> What version of PostgreSQL are you looking at? Note
>> that the buffer 
>> cache replacement strategy was completely changed
>> for version 8.0, which 
>> is currently in BETA test. A description of the
>> algorithm can be found 
>> in the README file in src/backend/storage/bufmgr.
> 
> oki, Thanks for the information. I have a look at 8.0
> beta, but cannot start the statistic collector. (I had
> post this err message before for help, but havent
> really got any clue to fix it)
>> LOG:  could not create IPv6 socket: Address family
> not
>> supported by protocol
>> LOG:  could not bind socket for statistics
> collector:
>> Cannot assign requested address
>> LOG:  disabling statistics collector for lack of
>> working socket

Tom Lane answered to that question. The code in question does resolve 
"localhost" with getaddrinfo() and then tries to create and bind a UDP 
socket to all returned addresses. For some reason "localhost" on your 
system resolves to an address that is not available for bind(2).

> 
> btw, what i want to ask here is does postgreSQL have
> any kind of read-ahead buffer implemented? 'cos it
> would be useful in multimedia case when we always scan
> the large table for continous data.

Since there is no mechanism to control that data is stored contiguously 
in the tables, what would that be good for?


Jan

-- 
#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me.                                  #
#================================================== JanWieck@Yahoo.com #

From pgsql-performance-owner@postgresql.org  Tue Aug 24 10:30:42 2004
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Date: Tue, 24 Aug 2004 15:30:14 +0200
From: Stef 
To: pgsql-performance@postgresql.org
Subject: Re: Query kills machine.
Message-Id: <20040824153014.2a11d228@svb.ucs.co.za>
In-Reply-To: <412B05A2.8070301@familyhealth.com.au>
References: <20040824103240.4d909777@svb.ucs.co.za>
	<412B05A2.8070301@familyhealth.com.au>
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Christopher Kings-Lynne mentioned :
=> sort_mem = 4096

Reducing sort_mem to 4096 seems to make it run in a reasonable time
again. Any idea why? The database does a whole lot of huge sorts
every day, so I thought upping this parameter would help.

A couple of queries do seem to run slower now that I reduced
the sort_mem. 

The shared buffers still makes a significant difference when I increase it.

Kind Regards
Stefan


From pgsql-performance-owner@postgresql.org  Tue Aug 24 15:48:15 2004
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Subject: Re: Query kills machine.
References: <20040824103240.4d909777@svb.ucs.co.za>
	<412B05A2.8070301@familyhealth.com.au>
	<20040824153014.2a11d228@svb.ucs.co.za>
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Stef wrote:

> Christopher Kings-Lynne mentioned :
> => sort_mem = 4096
> 
> Reducing sort_mem to 4096 seems to make it run in a reasonable time
> again. Any idea why? The database does a whole lot of huge sorts
> every day, so I thought upping this parameter would help.
> 
> A couple of queries do seem to run slower now that I reduced
> the sort_mem. 
> 
> The shared buffers still makes a significant difference when I increase it.
> 

Well you have to take in account that sort_mem is not the total memory 
allocated for sorting but per connection and in complex expressions 
serveral times that too.

So if you sort a lot it can push your operating system off the cliff and 
it might start reaping things that shouldn't be reaped and start swapping.

If that happens _everything_ on that box will get slow...

Shared buffers on the other hand is only allocated once.

Regards,
Magnus

From pgsql-performance-owner@postgresql.org  Tue Aug 24 11:15:05 2004
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From: "Magnus Naeslund(pg)" 
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To: Stef 
Cc: pgsql-performance@postgresql.org
Subject: Re: Query kills machine.
References: <20040824103240.4d909777@svb.ucs.co.za>
	<412B05A2.8070301@familyhealth.com.au>
	<20040824153014.2a11d228@svb.ucs.co.za>
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Stef wrote:

 > Christopher Kings-Lynne mentioned :
 > => sort_mem = 4096
 >
 > Reducing sort_mem to 4096 seems to make it run in a reasonable time
 > again. Any idea why? The database does a whole lot of huge sorts
 > every day, so I thought upping this parameter would help.
 >
 > A couple of queries do seem to run slower now that I reduced
 > the sort_mem.
 > The shared buffers still makes a significant difference when I 
increase it.
 >

Well you have to take in account that sort_mem is not the total memory 
allocated for sorting but per connection and in complex expressions 
serveral times that too.

So if you sort a lot it can push your operating system off the cliff and 
it might start reaping things that shouldn't be reaped and start swapping.

If that happens _everything_ on that box will get slow...

Shared buffers on the other hand is only allocated once.

Regards,
Magnus


From pgsql-performance-owner@postgresql.org  Tue Aug 24 12:23:30 2004
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To: Stef 
Cc: pgsql-performance@postgresql.org
Subject: Re: Query kills machine. 
In-reply-to: <20040824153014.2a11d228@svb.ucs.co.za> 
References: <20040824103240.4d909777@svb.ucs.co.za>
	<412B05A2.8070301@familyhealth.com.au>
	<20040824153014.2a11d228@svb.ucs.co.za>
Comments: In-reply-to Stef 
	message dated "Tue, 24 Aug 2004 15:30:14 +0200"
Date: Tue, 24 Aug 2004 11:23:31 -0400
Message-ID: <4015.1093361011@sss.pgh.pa.us>
From: Tom Lane 
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Stef  writes:
> Reducing sort_mem to 4096 seems to make it run in a reasonable time
> again. Any idea why? The database does a whole lot of huge sorts
> every day, so I thought upping this parameter would help.

Not if you haven't got the RAM to support it :-(

Another thing you might look at is ANALYZEing the tables again after
you've loaded all the new data.  The row-count estimates seem way off
in these plans.  You might need to increase the statistics target,
too, to get better plans.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Tue Aug 24 13:31:23 2004
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From: Gaetano Mendola 
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Subject: [FUN] Performance increase?
Date: Tue, 24 Aug 2004 18:17:29 +0200
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Do you think that adopting the "chip tuning" product
postgresql could increase the performances as well ?



Regards
Gaetano Mendola




From pgsql-performance-owner@postgresql.org  Tue Aug 24 17:30:42 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: Daniel Ceregatti , pgsql-performance@postgresql.org
Subject: Re: What is the best way to do attribute/values?
Date: Tue, 24 Aug 2004 13:30:32 -0700
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Folks,

> I've discussed these attempts with people in #postgresql on
> irc.freenode.net. Agliodbs (I presume you know who this is) was very
> helpful, but in end was at a loss. I find myself in the same postition
> at this time. He suggested I contact this list.

There's a couple of issues here to attack:

1) PostgreSQL is not using the most optimal plan.    First, it's ignoring the 
fact that all referenced columns are indexed and only using the first column, 
then filtering based on the other criteria.   Second, testing has shown that 
a hash join would actually be faster.   We've tried upping the statistics, 
but it doesn't seem to have an effect on the planner's erroneous estimates.

2) Even were it using the most optimal plan, it's still to slow.   As you can 
see from the plan, each merge join takes about 1.5 to 2 seconds.    (hash 
joins are only about 0.5 seconds slower).  Mysteriously, a big chunk of this 
time is spent *in bewtween* planner steps, as if there was some hold-up in 
retrieving the index or table pages.   There may be, but Daniel and I have 
not been able to diagnose the cause.   It's particularly mysterious since a 
filter-and-sort on a *single* criteria set, without join, takes < 400ms.

Things we've already tried to avoid going over old ground:
1) increasing statistics;
2) increasing sort_mem (to 256MB, which is overkill)
3) testing on 8.0 beta, which does not affect the issue.

At this point I'm looking for ideas.   Suggestions, anyone?

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Tue Aug 24 18:00:56 2004
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From: Richard Huxton 
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To: Daniel Ceregatti 
Cc: pgsql-performance@postgresql.org
Subject: Re: What is the best way to do attribute/values?
References: <4124EB58.9040102@sh.nu>
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Daniel Ceregatti wrote:
> Hi list,
> 
> I have a database with 1M "people" in it. Each person has about 20
> attributes, such as height, weight, eye color, etc. I need to be able to
> search for people based on these attributes. A search can be conducted
> on one attribute, all attributes, or any number in between. How would
> _you_ do this?
> 
> I have already attempted to answer this. My attempts are detailed here:
> 
> http://sh.nu/email.txt

Hmm... interesting.

Shot in the dark - try a tsearch2 full-text index. Your problem could be 
translated into searching strings of the form
   "hair=black eyes=blue age=117"

Not pretty, but might give you the speed you want.
-- 
   Richard Huxton
   Archonet Ltd

From pgsql-performance-owner@postgresql.org  Wed Aug 25 21:50:21 2004
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From: Mischa Sandberg 
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Coming from the MSSQL world, I'm used to the first step in optimization
to be, choose your clustered index and choose it well.

I see that PG has a one-shot CLUSTER command, but doesn't support
continuously-updated clustered indexes.

What I infer from newsgroup browsing is, such an index is impossible,
given the MVCC versioning of records (happy to learn I'm wrong).

I'd be curious to know what other people, who've crossed this same
bridge from MSSQL or Oracle or Sybase to PG, have devised,
faced with the same kind of desired performance gain for retrieving
blocks of rows with the same partial key.

From pgsql-performance-owner@postgresql.org  Wed Aug 25 03:54:18 2004
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	Tue, 24 Aug 2004 23:54:05 PDT
Date: Tue, 24 Aug 2004 23:54:05 -0700 (PDT)
From: my ho 
Subject: Re: postgresql performance with multimedia
To: pgsql-performance@postgresql.org
Cc: Jan Wieck 
In-Reply-To: <412B2DE7.6000809@Yahoo.com>
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> Tom Lane answered to that question. The code in
> question does resolve 
> "localhost" with getaddrinfo() and then tries to
> create and bind a UDP 
> socket to all returned addresses. For some reason
> "localhost" on your 
> system resolves to an address that is not available
> for bind(2).

I tried to put my_ip instead of "localhost" in
bufmng.c and it seems to work (no more complaining).
However i check the pg_statio_all_tables and dont see
any recorded statistic at all. (all the columns are
'0')
some time postmaster shut down with this err msg: 
LOG:  statistics collector process ()
exited with exit code 1
i starts postmaster with this command:
postmaster -i -p $PORT -D $PGDATA -k $PGDATA -N 32 -B
64 -o -s

> > btw, what i want to ask here is does postgreSQL
> have
> > any kind of read-ahead buffer implemented? 'cos it
> > would be useful in multimedia case when we always
> scan
> > the large table for continous data.
> 
> Since there is no mechanism to control that data is
> stored contiguously 
> in the tables, what would that be good for?

i thought that rows in the table will be stored
contiguously? in that case, if the user is requesting
1 row, we make sure that the continue rows are ready
in the buffer pool so that when they next requested,
they wont be asked to read from disk. For multimedia
data, this is important 'cos data needs to be
presented continuously without any waiting.

thanks again for your help
MT Ho



__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
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From pgsql-performance-owner@postgresql.org  Wed Aug 25 04:14:13 2004
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Subject: Re: postgresql performance with multimedia
Date: Wed, 25 Aug 2004 00:14:01 -0700
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Thread-Topic: [PERFORM] postgresql performance with multimedia
Thread-Index: AcSKcJFOkOxlIeQ3SpKqe7h0GU/2YAAAb0h8
From: "Gregory S. Williamson" 
To: "my ho" ,
	
Cc: "Jan Wieck" 
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Not sure about the overall performance, etc. but I think that in order to c=
ollect statistics you need to set some values in the postgresql.conf config=
 file, to wit:
#---------------------------------------------------------------------------
# RUNTIME STATISTICS
#---------------------------------------------------------------------------

# - Statistics Monitoring -

#log_parser_stats =3D false
#log_planner_stats =3D false
#log_executor_stats =3D false
#log_statement_stats =3D false

# - Query/Index Statistics Collector -

stats_start_collector =3D true
stats_command_string =3D true
stats_block_level =3D true
stats_row_level =3D true
#stats_reset_on_server_start =3D true

If the appropriate values aren't set this could account for why no entries =
are found in the pg_stat tables. The manual has details on these; you'll ne=
ed to reload postgres to make any changes effective.

Greg


-----Original Message-----
From:	my ho [mailto:mthoatbanjo@yahoo.com]
Sent:	Tue 8/24/2004 11:54 PM
To:	pgsql-performance@postgresql.org
Cc:	Jan Wieck
Subject:	Re: [PERFORM] postgresql performance with multimedia
> Tom Lane answered to that question. The code in
> question does resolve=20
> "localhost" with getaddrinfo() and then tries to
> create and bind a UDP=20
> socket to all returned addresses. For some reason
> "localhost" on your=20
> system resolves to an address that is not available
> for bind(2).

I tried to put my_ip instead of "localhost" in
bufmng.c and it seems to work (no more complaining).
However i check the pg_statio_all_tables and dont see
any recorded statistic at all. (all the columns are
'0')
some time postmaster shut down with this err msg:=20
LOG:  statistics collector process ()
exited with exit code 1
i starts postmaster with this command:
postmaster -i -p $PORT -D $PGDATA -k $PGDATA -N 32 -B
64 -o -s

> > btw, what i want to ask here is does postgreSQL
> have
> > any kind of read-ahead buffer implemented? 'cos it
> > would be useful in multimedia case when we always
> scan
> > the large table for continous data.
>=20
> Since there is no mechanism to control that data is
> stored contiguously=20
> in the tables, what would that be good for?

i thought that rows in the table will be stored
contiguously? in that case, if the user is requesting
1 row, we make sure that the continue rows are ready
in the buffer pool so that when they next requested,
they wont be asked to read from disk. For multimedia
data, this is important 'cos data needs to be
presented continuously without any waiting.

thanks again for your help
MT Ho



__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around=20
http://mail.yahoo.com=20

---------------------------(end of broadcast)---------------------------
TIP 4: Don't 'kill -9' the postmaster




From pgsql-performance-owner@postgresql.org  Wed Aug 25 05:19:59 2004
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Date: Wed, 25 Aug 2004 20:22:18 +1200
From: Mark Kirkwood 
Subject: Re: What is the best way to do attribute/values?
In-reply-to: <200408241330.32484.josh@agliodbs.com>
To: Josh Berkus 
Cc: Daniel Ceregatti , pgsql-performance@postgresql.org
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Josh Berkus wrote:

> Things we've already tried to avoid going over old ground:
>
>1) increasing statistics;
>2) increasing sort_mem (to 256MB, which is overkill)
>3) testing on 8.0 beta, which does not affect the issue.
>
>At this point I'm looking for ideas.   Suggestions, anyone?
>
>  
>
with respect to query design:

consider instead of:

select
	pav1.person_id
from
	person_attributes_vertical pav1,
	person_attributes_vertical pav2
where
	pav1.attribute_id = 1
	and pav1.value_id in (2,3)
	and pav2.attribute_id = 2
	and pav2.value_id in (2,3)
	and pav1.person_id = pav2.person_id

try:

select
	pav1.person_id
from
	person_attributes_vertical pav1
where
	   (    pav1.attribute_id = 1
	    and pav1.value_id in (2,3))
	or (    pav1.attribute_id = 2
	    and pav1.value_id in (2,3))
	
I am gambling that the 'or's' might be less expensive than the multiple self joins (particularly in the more general cases!).

To make access work well you might want to have *several* concatenated indexes of 2 -> 4 attributes - to work around Pg inability to use more than 1 in a given query.
For this query indexing (attribute_id, value_id) is probably good.

Consider playing with 'random_page_cost' and maybe 'effective_cache_size' to encourage the planner to use 'em.

regards

Mark





From pgsql-performance-owner@postgresql.org  Wed Aug 25 08:02:54 2004
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To: my ho 
Cc: pgsql-performance@postgresql.org
Subject: Re: postgresql performance with multimedia
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On 8/25/2004 2:54 AM, my ho wrote:
>> Tom Lane answered to that question. The code in
>> question does resolve 
>> "localhost" with getaddrinfo() and then tries to
>> create and bind a UDP 
>> socket to all returned addresses. For some reason
>> "localhost" on your 
>> system resolves to an address that is not available
>> for bind(2).
> 
> I tried to put my_ip instead of "localhost" in
> bufmng.c and it seems to work (no more complaining).
> However i check the pg_statio_all_tables and dont see
> any recorded statistic at all. (all the columns are
> '0')

The block level statistics are disabled by default in the 
postgresql.conf file.

> some time postmaster shut down with this err msg: 
> LOG:  statistics collector process ()
> exited with exit code 1

Fix your operating systems network settings instead of curing the 
symptoms by breaking PostgreSQL.

> i starts postmaster with this command:
> postmaster -i -p $PORT -D $PGDATA -k $PGDATA -N 32 -B
> 64 -o -s
> 
>> > btw, what i want to ask here is does postgreSQL
>> have
>> > any kind of read-ahead buffer implemented? 'cos it
>> > would be useful in multimedia case when we always
>> scan
>> > the large table for continous data.
>> 
>> Since there is no mechanism to control that data is
>> stored contiguously 
>> in the tables, what would that be good for?
> 
> i thought that rows in the table will be stored
> contiguously? in that case, if the user is requesting
> 1 row, we make sure that the continue rows are ready
> in the buffer pool so that when they next requested,
> they wont be asked to read from disk. For multimedia
> data, this is important 'cos data needs to be
> presented continuously without any waiting.

They are only stored in that way on initial load and if the load is done 
with a single process. And don't you rely on this for the future. Right 
now, if you ever update or delete tuples, that order changes already.

Also keep in mind that large values are not stored inline, but in an 
extra "TOAST" relation.

For your "streaming" purposes I strongly recommend you do it in your 
application with the appropriate thread model. A relational database 
management system is not a multimedia cache.


Jan

-- 
#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me.                                  #
#================================================== JanWieck@Yahoo.com #

From pgsql-performance-owner@postgresql.org  Wed Aug 25 08:26:26 2004
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Subject: OT: Network config (WAS: RE: postgresql performance with multimedia)
Date: Wed, 25 Aug 2004 13:26:00 +0200
Message-ID: 
 
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Thread-Topic: [PERFORM] postgresql performance with multimedia
Thread-Index: AcSKk08DfnU6zSyLRpmzepr6Hs7XmgAAsCNA
From: "Leeuw van der, Tim" 
To: "my ho" 
Cc: 
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Hi,

We're now getting very much off-topic about configuration of networking, bu=
t:

- What is your OS?
- What output do you get when you type 'ping localhost' in any command-prom=
pt?


-----Original Message-----

[...]
> I tried to put my_ip instead of "localhost" in
> bufmng.c and it seems to work (no more complaining).
[...]

regards,

--Tim

From pgsql-performance-owner@postgresql.org  Wed Aug 25 09:35:56 2004
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	Josh Berkus 
From: Jeff 
Subject: Re: What is the best way to do attribute/values?
Date: Wed, 25 Aug 2004 08:36:07 -0400
To: Mark Kirkwood 
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On Aug 25, 2004, at 4:22 AM, Mark Kirkwood wrote:

> select
> 	pav1.person_id
> from
> 	person_attributes_vertical pav1
> where
> 	   (    pav1.attribute_id = 1
> 	    and pav1.value_id in (2,3))
> 	or (    pav1.attribute_id = 2
> 	    and pav1.value_id in (2,3))
>

You know..
It may help if you toss in a group by
ie

select pav1.person_id, count(*) from person_attributes_vertical pav1
where (pav1.attribute_id = 1 and pav1.value_id in (2,3)) or ( ... ) or 
(...)
group by pav1.person_id
order by count(*) desc

that should give you the person_id's that matched the most 
criteria........
I've used similar things before now that I've thought about it.

If you want an exact match you could put
"having count(*) = $myNumAttributes" in there too.. By definition an 
exact match would match that definition..

it has an added side effect of producing "closest matches" when an 
exact match cannot be found... granted you may not want that for a 
dating site : )

"You asked for a blond female, blue eyes.. but I couldn't find any... 
but I *DID* find a brown haired male with brown eyes! Is that good 
enough?"

--
Jeff Trout 
http://www.jefftrout.com/
http://www.stuarthamm.net/


From pgsql-performance-owner@postgresql.org  Wed Aug 25 10:06:45 2004
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Subject: Re: What is the best way to do attribute/values?
Date: Wed, 25 Aug 2004 15:05:56 +0200
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From: "Leeuw van der, Tim" 
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Hi,

On Aug 25, 2004, at 4:22 AM, Mark Kirkwood wrote:

> select
> 	pav1.person_id
> from
> 	person_attributes_vertical pav1
> where
> 	   (    pav1.attribute_id =3D 1
> 	    and pav1.value_id in (2,3))
> 	or (    pav1.attribute_id =3D 2
> 	    and pav1.value_id in (2,3))
>

[...]

Why not combine attribute_id and value_id? Then you have nothing but an OR =
(or IN).

It should, AFAICS, give you much better selectivity on your indexes:

There will be a lot of attributes with the same ID; there will also be a lo=
t of attributes with the same value. However, there should be much less att=
ributes with a specific combination of (ID/Value).
Right now I think it will be very hard to determine which field has a bette=
r selectivity: attribute_id or value_id.


The combined attribute/value field could be an int8 or so, where the upper =
4 bytes are for attribute_id and the lower 4 bytes for value_id.
Depending on the number of attributes and possible values a smaller datatyp=
e and / or a different split can be made. A smaller datatype will result in=
 faster access.

What difference does that make?

regards,

--Tim

From pgsql-performance-owner@postgresql.org  Wed Aug 25 11:31:19 2004
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Date: Wed, 25 Aug 2004 16:30:41 +0200
From: Stef 
To: Tom Lane 
Cc: pgsql-performance@postgresql.org
Subject: Re: Query kills machine.
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	<412B05A2.8070301@familyhealth.com.au>
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Tom Lane mentioned :
=> Not if you haven't got the RAM to support it :-(
=> 
=> Another thing you might look at is ANALYZEing the tables again after
=> you've loaded all the new data.  The row-count estimates seem way off
=> in these plans.  You might need to increase the statistics target,
=> too, to get better plans.

Thanks Tom, Christopher and Magnus!

I tested this, and found the correct sort_mem setting for my situation.
I'm testing a new default_statistics_target setting.
This is something I never considered.

Kind Regards
Stefan

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I have 2 servers both with the exact same data, the same O.S., the same
version of Postgres (7.4.5) and the exact same db schema's (one production
server, one development server).  One server is using the correct index for
SQL queries resulting in extremely slow performance, the other server is
properly selecting the index to use and performance is many times better.  I
have tried vacuum, but that did not work.  I finally resorted to dumping the
data, removing the database completely, creating a new database and
importing the data only to have to problem resurface.  The table has
5,000,000+ rows on both the systems.

When I run 'analyze verbose' on the correctly working system, the following
is displayed:
    {INDEXSCAN
    :startup_cost 0.00
    :total_cost 465.10
    :plan_rows 44
    :plan_width 118
    :targetlist (
       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 1
          :restype 23
          :restypmod -1
          :resname trn_integer
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 1
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 1
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 1
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 2
          :restype 23
          :restypmod -1
          :resname trn_patno
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 2
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 2
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 2
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 3
          :restype 1042
          :restypmod 5
          :resname trn_bill_inc
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 3
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 3
          :vartype 1042
          :vartypmod 5
          :varlevelsup 0
          :varnoold 1
          :varoattno 3
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 4
          :restype 1043
          :restypmod 13
          :resname trn_userid
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 4
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 4
          :vartype 1043
          :vartypmod 13
          :varlevelsup 0
          :varnoold 1
          :varoattno 4
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 5
          :restype 23
          :restypmod -1
          :resname trn_location
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 5
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 5
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 5
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 6
          :restype 1082
          :restypmod -1
          :resname trn_date
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 6
          :resjunk false
          }
       :expr
          {VAR
          :varno 1
          :varattno 6
          :vartype 1082
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 6
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 7
          :restype 23
          :restypmod -1
          :resname trn_sercode
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 7
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 7
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 7
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 8
          :restype 1043
          :restypmod 28
          :resname trn_descr
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 8
          :resjunk false
          }
       :expr
          {VAR
          :varno 1
          :varattno 8
          :vartype 1043
          :vartypmod 28
          :varlevelsup 0
          :varnoold 1
          :varoattno 8
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 9
          :restype 23
          :restypmod -1
          :resname trn_employr
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 9
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 9
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 9
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 10
          :restype 23
          :restypmod -1
          :resname trn_prof
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 10
          :resjunk false
          }
       :expr
          {VAR
          :varno 1
          :varattno 10
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 10
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 11
          :restype 1700
          :restypmod 720902
          :resname trn_amount
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 11
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 11
          :vartype 1700
          :vartypmod 720902
          :varlevelsup 0
          :varnoold 1
          :varoattno 11
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 12
          :restype 1043
          :restypmod 7
          :resname trn_tooth
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 12
          :resjunk false
          }
       :expr
          {VAR
          :varno 1
          :varattno 12
          :vartype 1043
          :vartypmod 7
          :varlevelsup 0
          :varnoold 1
          :varoattno 12
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 13
          :restype 1043
          :restypmod 10
          :resname trn_surface
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 13
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 13
          :vartype 1043
          :vartypmod 10
          :varlevelsup 0
          :varnoold 1
          :varoattno 13
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 14
          :restype 1042
          :restypmod 5
          :resname trn_flag
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 14
          :resjunk false
          }
       :expr
          {VAR
          :varno 1
          :varattno 14
          :vartype 1042
          :vartypmod 5
          :varlevelsup 0
          :varnoold 1
          :varoattno 14
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 15
          :restype 23
          :restypmod -1
          :resname trn_counter
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 15
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 15
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 15
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 16
          :restype 23
          :restypmod -1
          :resname trn_guarantr
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 16
          :resjunk false
          }
       :expr
          {VAR
          :varno 1
          :varattno 16
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 16
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 17
          :restype 1042
          :restypmod 5
          :resname trn_lab
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 17
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 17
          :vartype 1042
          :vartypmod 5
          :varlevelsup 0
          :varnoold 1
          :varoattno 17
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 18
          :restype 1082
          :restypmod -1
          :resname trn_old_date
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 18
          :resjunk false
          }
       :expr
          {VAR
          :varno 1
          :varattno 18
          :vartype 1082
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 18
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 19
          :restype 1042
          :restypmod 5
          :resname trn_hist_flag
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 19
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 19
          :vartype 1042
          :vartypmod 5
          :varlevelsup 0
          :varnoold 1
          :varoattno 19
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 20
          :restype 23
          :restypmod -1
          :resname trn_check_no
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 20
          :resjunk false
          }
       :expr
          {VAR
          :varno 1
          :varattno 20
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 20
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 21
          :restype 1043
          :restypmod 7
          :resname trn_commcode
          :ressortgroupref 0
          :resorigtbl 789839
          :resorigcol 21
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 21
          :vartype 1043
          :vartypmod 7
          :varlevelsup 0
          :varnoold 1
          :varoattno 21
          }
       }
    )
    :qual (
       {OPEXPR
       :opno 1098
       :opfuncid 1090
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 18
          :vartype 1082
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 18
          }

          {CONST
          :consttype 1082
          :constlen 4
          :constbyval true
          :constisnull false
          :constvalue 4 [ 91 -8 -1 -1 ]
          }
       )
       }
       {OPEXPR
       :opno 1096
       :opfuncid 1088
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 18
          :vartype 1082
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 18
          }

          {CONST
          :consttype 1082
          :constlen 4
          :constbyval true
          :constisnull false
          :constvalue 4 [ -96 6 0 0 ]
          }
       )
       }

       {OPEXPR
       :opno 1054
       :opfuncid 1048
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 3
          :vartype 1042
          :vartypmod 5
          :varlevelsup 0
          :varnoold 1
          :varoattno 3
          }

          {CONST
          :consttype 1042
          :constlen -1
          :constbyval false
          :constisnull false
          :constvalue 5 [ 5 0 0 0 66 ]
          }
       )
       }
    )

    :lefttree <>
    :righttree <>
    :initPlan <>
    :extParam ()

    :allParam ()

    :nParamExec 0
    :scanrelid 1
    :indxid ( 7725589)

    :indxqual ((
       {OPEXPR
       :opno 96
       :opfuncid 65
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 1
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 2
          }

          {CONST
          :consttype 23
          :constlen 4
          :constbyval true
          :constisnull false
          :constvalue 4 [ 63 13 3 0 ]
          }
       )
       }
    )
    )

    :indxqualorig ((
       {OPEXPR
       :opno 96
       :opfuncid 65
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 2
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 2
          }

          {CONST
          :consttype 23
          :constlen 4
          :constbyval true
          :constisnull false
          :constvalue 4 [ 63 13 3 0 ]
          }
       )
       }
    )
    )

    :indxorderdir 1
    }

 Index Scan using trptserc on trans  (cost=0.00..465.10 rows=44 width=118)
   Index Cond: (trn_patno = 199999)
   Filter: ((trn_old_date >= '1994-08-23'::date) AND (trn_old_date <=
'2004-08-23'::date) AND (trn_bill_inc = 'B'::bpchar))
(687 rows)


Now, when I run 'analyze verbose' on the INCORRECTLY working system, the
following is displayed:
    {INDEXSCAN
    :startup_cost 0.00
    :total_cost 105165.74
    :plan_rows 1
    :plan_width 143
    :targetlist (
       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 1
          :restype 23
          :restypmod -1
          :resname trn_integer
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 1
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 1
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 1
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 2
          :restype 23
          :restypmod -1
          :resname trn_patno
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 2
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 2
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 2
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 3
          :restype 1042
          :restypmod 5
          :resname trn_bill_inc
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 3
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 3
          :vartype 1042
          :vartypmod 5
          :varlevelsup 0
          :varnoold 1
          :varoattno 3
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 4
          :restype 1043
          :restypmod 13
          :resname trn_userid
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 4
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 4
          :vartype 1043
          :vartypmod 13
          :varlevelsup 0
          :varnoold 1
          :varoattno 4
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 5
          :restype 23
          :restypmod -1
          :resname trn_location
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 5
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 5
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 5
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 6
          :restype 1082
          :restypmod -1
          :resname trn_date
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 6
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 6
          :vartype 1082
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 6
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 7
          :restype 23
          :restypmod -1
          :resname trn_sercode
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 7
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 7
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 7
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 8
          :restype 1043
          :restypmod 28
          :resname trn_descr
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 8
          :resjunk false
          }
       :expr
          {VAR
          :varno 1
          :varattno 8
          :vartype 1043
          :vartypmod 28
          :varlevelsup 0
          :varnoold 1
          :varoattno 8
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 9
          :restype 23
          :restypmod -1
          :resname trn_employer
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 9
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 9
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 9
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 10
          :restype 23
          :restypmod -1
          :resname trn_prof
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 10
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 10
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 10
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 11
          :restype 1700
          :restypmod 720902
          :resname trn_amount
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 11
          :resjunk false
          }
       :expr
          {VAR
          :varno 1
          :varattno 11
          :vartype 1700
          :vartypmod 720902
          :varlevelsup 0
          :varnoold 1
          :varoattno 11
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 12
          :restype 1043
          :restypmod 7
          :resname trn_tooth
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 12
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 12
          :vartype 1043
          :vartypmod 7
          :varlevelsup 0
          :varnoold 1
          :varoattno 12
          }
       }
       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 13
          :restype 1043
          :restypmod 10
          :resname trn_surface
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 13
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 13
          :vartype 1043
          :vartypmod 10
          :varlevelsup 0
          :varnoold 1
          :varoattno 13
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 14
          :restype 1042
          :restypmod 5
          :resname trn_flag
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 14
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 14
          :vartype 1042
          :vartypmod 5
          :varlevelsup 0
          :varnoold 1
          :varoattno 14
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 15
          :restype 23
          :restypmod -1
          :resname trn_counter
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 15
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 15
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 15
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 16
          :restype 23
          :restypmod -1
          :resname trn_guarantr
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 16
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 16
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 16
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 17
          :restype 1042
          :restypmod 5
          :resname trn_lab
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 17
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 17
          :vartype 1042
          :vartypmod 5
          :varlevelsup 0
          :varnoold 1
          :varoattno 17
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 18
          :restype 1082
          :restypmod -1
          :resname trn_old_date
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 18
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 18
          :vartype 1082
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 18
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 19
          :restype 1042
          :restypmod 5
          :resname trn_hist_flag
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 19
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 19
          :vartype 1042
          :vartypmod 5
          :varlevelsup 0
          :varnoold 1
          :varoattno 19
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 20
          :restype 23
          :restypmod -1
          :resname trn_check_no
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 20
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 20
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 20
          }
       }

       {TARGETENTRY
       :resdom
          {RESDOM
          :resno 21
          :restype 1043
          :restypmod 7
          :resname trn_commcode
          :ressortgroupref 0
          :resorigtbl 2487466
          :resorigcol 21
          :resjunk false
          }

       :expr
          {VAR
          :varno 1
          :varattno 21
          :vartype 1043
          :vartypmod 7
          :varlevelsup 0
          :varnoold 1
          :varoattno 21
          }
       }
    )
    :qual (
       {OPEXPR
       :opno 96
       :opfuncid 65
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 2
          :vartype 23
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 2
          }

          {CONST
          :consttype 23
          :constlen 4
          :constbyval true
          :constisnull false
          :constvalue 4 [ 63 13 3 0 ]
          }
       )
       }

       {OPEXPR
       :opno 1054
       :opfuncid 1048
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 3
          :vartype 1042
          :vartypmod 5
          :varlevelsup 0
          :varnoold 1
          :varoattno 3
          }

          {CONST
          :consttype 1042
          :constlen -1
          :constbyval false
          :constisnull false
          :constvalue 5 [ 5 0 0 0 66 ]
          }
       )
       }
    )

    :lefttree <>
    :righttree <>
    :initPlan <>
    :extParam ()

    :allParam ()

    :nParamExec 0
    :scanrelid 1
    :indxid ( 7762034)

    :indxqual ((
       {OPEXPR
       :opno 1098
       :opfuncid 1090
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 1
          :vartype 1082
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 18
          }

          {CONST
          :consttype 1082
          :constlen 4
          :constbyval true
          :constisnull false
          :constvalue 4 [ 91 -8 -1 -1 ]
          }
       )
       }
       {OPEXPR
       :opno 1096
       :opfuncid 1088
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 1
          :vartype 1082
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 18
          }

          {CONST
          :consttype 1082
          :constlen 4
          :constbyval true
          :constisnull false
          :constvalue 4 [ -96 6 0 0 ]
          }
       )
       }
    )
    )

    :indxqualorig ((
       {OPEXPR
       :opno 1098
       :opfuncid 1090
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 18
          :vartype 1082
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 18
          }
          {CONST
          :consttype 1082
          :constlen 4
          :constbyval true
          :constisnull false
          :constvalue 4 [ 91 -8 -1 -1 ]
          }
       )
       }

       {OPEXPR
       :opno 1096
       :opfuncid 1088
       :opresulttype 16
       :opretset false
       :args (
          {VAR
          :varno 1
          :varattno 18
          :vartype 1082
          :vartypmod -1
          :varlevelsup 0
          :varnoold 1
          :varoattno 18
          }

          {CONST
          :consttype 1082
          :constlen 4
          :constbyval true
          :constisnull false
          :constvalue 4 [ -96 6 0 0 ]
          }
       )
       }
    )
    )

    :indxorderdir 1
    }

 Index Scan using todate on trans  (cost=0.00..105165.74 rows=1 width=143)
   Index Cond: ((trn_old_date >= '1994-08-23'::date) AND (trn_old_date <=
'2004-08-23'::date))
   Filter: ((trn_patno = 199999) AND (trn_bill_inc = 'B'::bpchar))
(713 rows)


So, you see the query optimizer has choosen different indices the two
systems - one correctly and the other incorrectly on the exact same set of
data????  I can change the query to reduce the number of arguments and then
perform a subquery (in my java code) but I am afraid there is an internal
problem that will crop up somewhere else.



From pgsql-performance-owner@postgresql.org  Wed Aug 25 12:47:30 2004
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Date: Wed, 25 Aug 2004 16:47:19 +0100
From: Richard Huxton 
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To: David Price 
Cc: pgsql-performance@postgresql.org
Subject: Re: Optimizer Selecting Incorrect Index
References: 
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David Price wrote:
> I have 2 servers both with the exact same data, the same O.S., the same
> version of Postgres (7.4.5) and the exact same db schema's (one production
> server, one development server).  One server is using the correct index for
> SQL queries resulting in extremely slow performance, the other server is
> properly selecting the index to use and performance is many times better.  I
> have tried vacuum, but that did not work.  I finally resorted to dumping the
> data, removing the database completely, creating a new database and
> importing the data only to have to problem resurface.  The table has
> 5,000,000+ rows on both the systems.
> 
> When I run 'analyze verbose' on the correctly working system, the following
> is displayed:

EXPLAIN ANALYZE is usually considered enough

>  Index Scan using trptserc on trans  (cost=0.00..465.10 rows=44 width=118)
>    Index Cond: (trn_patno = 199999)
>    Filter: ((trn_old_date >= '1994-08-23'::date) AND (trn_old_date <=
> '2004-08-23'::date) AND (trn_bill_inc = 'B'::bpchar))
> (687 rows)
> 
> 
> Now, when I run 'analyze verbose' on the INCORRECTLY working system, the
> following is displayed:

>  Index Scan using todate on trans  (cost=0.00..105165.74 rows=1 width=143)
>    Index Cond: ((trn_old_date >= '1994-08-23'::date) AND (trn_old_date <=
> '2004-08-23'::date))
>    Filter: ((trn_patno = 199999) AND (trn_bill_inc = 'B'::bpchar))
> (713 rows)

These queries are different. The first returns 687 rows and the second 
713 rows. You need to check your systems if they are supposed to be 
identical.

Things to check:
1. postgresql.conf settings match - different costs could cause this
2. statistics on the two columns (trn_patno,trn_old_date) - if they 
differ considerably between systems that would also explain it.

I suspect the second one, at a wild guess the working system happens to 
know 199999 is fairly rare wheras the second just estimates an average.

If the stats don't help, people are going to want to see the entire 
query+plan. Could you repost with the query and explain analyse on both 
system. Oh, and some idea on how many rows/unique values are involved in 
the important columns.

-- 
   Richard Huxton
   Archonet Ltd

From pgsql-performance-owner@postgresql.org  Wed Aug 25 13:59:47 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: pgsql-performance@postgresql.org
Subject: Re: What is the best way to do attribute/values?
Date: Wed, 25 Aug 2004 09:59:15 -0700
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	<412C4C3A.2030001@coretech.co.nz>
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Mark, Tim,

> select
> 	pav1.person_id
> from
> 	person_attributes_vertical pav1
> where
> 	   (    pav1.attribute_id = 1
> 	    and pav1.value_id in (2,3))
> 	or (    pav1.attribute_id = 2
> 	    and pav1.value_id in (2,3))

Not the same query, sorry.   Daniel's query yields all the person_id's which 
have criteria A AND criteria B.   Yours gives all the person_id's which have 
criteria A OR criteria B.

> There will be a lot of attributes with the same ID; there will also be a
> lot of attributes with the same value. However, there should be much less
> attributes with a specific combination of (ID/Value). Right now I think it
> will be very hard to determine which field has a better selectivity:
> attribute_id or value_id.

Given that there is already an index on ( attribute_id, value_id ) I don't 
quite see what difference this makes.   Unless you're suggesting this as a 
workaround for the PG Planner's poor use of the index?

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Wed Aug 25 16:08:08 2004
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To: Richard Huxton 
Cc: David Price ,
	pgsql-performance@postgresql.org
Subject: Re: Optimizer Selecting Incorrect Index 
In-reply-to: <412CB487.6060704@archonet.com> 
References: 
	<412CB487.6060704@archonet.com>
Comments: In-reply-to Richard Huxton 
	message dated "Wed, 25 Aug 2004 16:47:19 +0100"
Date: Wed, 25 Aug 2004 15:08:01 -0400
Message-ID: <2137.1093460881@sss.pgh.pa.us>
From: Tom Lane 
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Richard Huxton  writes:
> Things to check:
> 1. postgresql.conf settings match - different costs could cause this
> 2. statistics on the two columns (trn_patno,trn_old_date) - if they 
> differ considerably between systems that would also explain it.

The different estimated row counts could only come from #2.  I suspect
David has forgotten to run ANALYZE on the second system.

I agree that EXPLAIN VERBOSE output is not helpful...

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Wed Aug 25 18:09:40 2004
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Subject: Anyone familiar with Apple Xserve RAID
From: Robert Treat 
To: pgsql-performance@postgresql.org
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Just curious if folks have ever used this for a postgresql server and if
they used it with OSX/BSD/Linux. Even if you haven't used it, if you
know of something comparable I'd be interested.  TIA

http://store.apple.com/1-800-MY-APPLE/WebObjects/AppleStore.woa/72103/wo/oC2xGlPM9M2i3UsLG0f1PaalTlE/0.0.9.1.0.6.13.0.3.1.3.0.7.12.1.1.0


Robert Treat
-- 
Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL


From pgsql-performance-owner@postgresql.org  Wed Aug 25 18:22:33 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: Robert Treat ,
	pgsql-performance@postgresql.org
Subject: Re: Anyone familiar with Apple Xserve RAID
Date: Wed, 25 Aug 2004 14:22:08 -0700
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Robert,

> Just curious if folks have ever used this for a postgresql server and if
> they used it with OSX/BSD/Linux. Even if you haven't used it, if you
> know of something comparable I'd be interested.  TIA

Last I checked Apple was still shipping the XServes with SATA drives and a 
PROMISE controller, both very consumer-grade (and not server-grade) hardware.   
I can't recommend the XServe as a database platform.  SCSI still makes a 
difference for databases, more because of the controllers than anything else.

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Wed Aug 25 19:48:42 2004
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From: =?iso-8859-15?q?Herv=E9_Piedvache?= 
To: pgsql-performance@postgresql.org
Subject: TSearch2 and optimisation ...
Date: Thu, 26 Aug 2004 00:48:32 +0200
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Hi,

I'm a little beginner with Tsearch2 ....

I have simples tables like this :

# \d article
                                         Table "public.article"
   Column   |            Type             |                            
Modifiers
------------+-----------------------------+-----------------------------------------------------------------
 id     | integer                     | not null default 
nextval('public.article_rss_id_rss_seq'::text)
 id_site    | integer                     | not null
 title  | text                        |
 url    | text                        |
 desc   | text                        |
 r_date   | timestamp without time zone | default now()
 r_update | timestamp without time zone | default now()
 idxfti     | tsvector                    |
Indexes:
    "article_id_key" unique, btree (id)
    "idxfti_idx" gist (idxfti)
    "ix_article_update" btree (r_update)
    "ix_article_url" btree (url)
    "ix_id_site" btree (id_site)
Foreign-key constraints:
    "$1" FOREIGN KEY (id_site) REFERENCES site (id_site)
Triggers:
    tsvectorupdate BEFORE INSERT OR UPDATE ON article FOR EACH ROW EXECUTE 
PROCEDURE tsearch2('idxfti', 'title', 'desc')

# \d site_rss
                                Table "public.site"
    Column    |  Type   |                           Modifiers
--------------+---------+---------------------------------------------------------------
 id_site      | integer | not null default 
nextval('public.site_id_site_seq'::text)
 site_name    | text    |
 site_url     | text    |
url             | text    |
 language     | text    |
 datecrea     | date    | default now()
 id_category  | integer |
 time_refresh | integer |
 active       | integer |
 error        | integer |
Indexes:
    "site_id_site_key" unique, btree (id_site)
    "ix_site_id_category" btree (id_category)
    "ix_site_url" btree (url)

# \d user_choice
  Table "public.user_choice"
 Column  |  Type   | Modifiers
---------+---------+-----------
 id_user | integer |
 id_site | integer |
Indexes:
    "ix_user_choice_all" unique, btree (id_user, id_site)

I have done a simple request, looking for title or description having Postgres 
inside order by rank and date,  like this :
SELECT a.title, a.id, a.url, to_char(a.r_date, 'DD/MM/YYYY HH24:MI:SS') as dt, 
s.site_name, s.id_site, case when exists (select id_user from user_choice u 
where u.id_site=s.id_site and u.id_user = 1) then 1 else 0 end as bookmarked
    FROM article a, site s
  WHERE s.id_site = a.id_site
       AND idxfti @@ to_tsquery('postgresql')
   ORDER BY rank(idxfti, to_tsquery('postgresql')) DESC, a.r_date DESC;

The request takes about 4 seconds ... I have about 1 400 000 records in 
article and 36 000 records in site table ... it's a Bi-Pentium III 933 MHz 
server with 1 Gb memory ... I'm using Postgresql 7.4.5
For me this result is very very slow I really need a quicker result with less 
than 1 second ...
The next time I call the same request I have got the result in 439 ms ... but 
If I replace "Postgresql" in my find with "Linux" for example I will get the 
next result in 5 seconds ... :o(

Is it a bad use of Tsearch2 ... or a bad table structure ... or from my 
request ... ? I have no idea how to optimise this ...

Explain gives me this result :
                                               QUERY PLAN
-----------------------------------------------------------------------------------------------------------
 Sort  (cost=10720.91..10724.29 rows=1351 width=191)
   Sort Key: rank(a.idxfti, '\'postgresql\''::tsquery), a.r_date
   ->  Merge Join  (cost=4123.09..10650.66 rows=1351 width=191)
         Merge Cond: ("outer".id_site = "inner".id_site)
         ->  Index Scan using site_id_site_key on site s  (cost=0.00..2834.96 
rows=35705 width=28)
         ->  Sort  (cost=4123.09..4126.47 rows=1351 width=167)
               Sort Key: a.id_site
               ->  Index Scan using idxfti_idx on article a  
(cost=0.00..4052.84 rows=1351 width=167)
                     Index Cond: (idxfti @@ '\'postgresql\''::tsquery)
                     Filter: (idxfti @@ '\'postgresql\''::tsquery)
         SubPlan
           ->  Seq Scan on user_choice u  (cost=0.00..2.69 rows=1 width=4)
                 Filter: ((id_site = $0) AND (id_user = 1))
(13 rows)

Any idea are well done ;o)

Regards,
-- 
Bill Footcow


From pgsql-performance-owner@postgresql.org  Wed Aug 25 19:52:17 2004
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From: Doug McNaught 
Subject: Re: Anyone familiar with Apple Xserve RAID
Date: Wed, 25 Aug 2004 18:52:05 -0400
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Josh Berkus  writes:

> Robert,
>
>> Just curious if folks have ever used this for a postgresql server and if
>> they used it with OSX/BSD/Linux. Even if you haven't used it, if you
>> know of something comparable I'd be interested.  TIA
>
\> Last I checked Apple was still shipping the XServes with SATA drives
> and a PROMISE controller, both very consumer-grade (and not
> server-grade) hardware.  I can't recommend the XServe as a database
> platform.  SCSI still makes a difference for databases, more because
> of the controllers than anything else.

The XServe RAID is fibre-channel.  

-Doug
-- 
Let us cross over the river, and rest under the shade of the trees.
   --T. J. Jackson, 1863


From pgsql-performance-owner@postgresql.org  Wed Aug 25 21:50:23 2004
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From: Ralf Schramm 
Subject: Re: Anyone familiar with Apple Xserve RAID
Date: Thu, 26 Aug 2004 00:58:24 +0200
To: Robert Treat 
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we checked a XServe/XRaid system some months ago and
especially the relation price/space/performance was OK
compared to a HP/Intel maschine. Tomorrow I'll try to
find the performance charts on my harddisc and post the
links to the list. You get a huge amount of raid-space
for a good price.

We plan to get one to do our web-statistics there with
about 150 MegaPageImpressions a month.

Ralf Schramm


Am 25.08.2004 um 23:09 schrieb Robert Treat:

> Just curious if folks have ever used this for a postgresql server and  
> if
> they used it with OSX/BSD/Linux. Even if you haven't used it, if you
> know of something comparable I'd be interested.  TIA
>
> http://store.apple.com/1-800-MY-APPLE/WebObjects/AppleStore.woa/72103/ 
> wo/oC2xGlPM9M2i3UsLG0f1PaalTlE/0.0.9.1.0.6.13.0.3.1.3.0.7.12.1.1.0
>
>
> Robert Treat
> -- 
> Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL


From pgsql-performance-owner@postgresql.org  Wed Aug 25 21:50:25 2004
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From: Ralf Schramm 
Subject: Re: Anyone familiar with Apple Xserve RAID
Date: Thu, 26 Aug 2004 01:03:52 +0200
To: Josh Berkus 
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the XServe/XRaid comes with FibreChannel

Here some infos:
http://www.apple.com/xserve/raid/architecture.html
http://www.apple.com/xserve/raid/fibre_channel.html
http://www.apple.com/xserve/architecture.html

Ralf Schramm


Am 25.08.2004 um 23:22 schrieb Josh Berkus:

> Robert,
>
>> Just curious if folks have ever used this for a postgresql server and 
>> if
>> they used it with OSX/BSD/Linux. Even if you haven't used it, if you
>> know of something comparable I'd be interested.  TIA
>
> Last I checked Apple was still shipping the XServes with SATA drives 
> and a
> PROMISE controller, both very consumer-grade (and not server-grade) 
> hardware.
> I can't recommend the XServe as a database platform.  SCSI still makes 
> a
> difference for databases, more because of the controllers than 
> anything else.
>
> -- 
> Josh Berkus
> Aglio Database Solutions
> San Francisco


From pgsql-performance-owner@postgresql.org  Wed Aug 25 20:49:28 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: Ralf Schramm 
Subject: Re: Anyone familiar with Apple Xserve RAID
Date: Wed, 25 Aug 2004 16:49:02 -0700
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Guys,

> the XServe/XRaid comes with FibreChannel

I stand corrected.   That should help things some; it makes it more of a small 
tradeoff between performance and storage size for the drives.

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Wed Aug 25 20:51:15 2004
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To: =?iso-8859-15?q?Herv=E9=20Piedvache?= ,
	pgsql-performance@postgresql.org
Subject: Re: TSearch2 and optimisation ...
Date: Wed, 25 Aug 2004 16:50:53 -0700
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Herve'

> The request takes about 4 seconds ... I have about 1 400 000 records in
> article and 36 000 records in site table ... it's a Bi-Pentium III 933 MHz
> server with 1 Gb memory ... I'm using Postgresql 7.4.5
> For me this result is very very slow I really need a quicker result with
> less than 1 second ...
> The next time I call the same request I have got the result in 439 ms ...
> but If I replace "Postgresql" in my find with "Linux" for example I will
> get the next result in 5 seconds ... :o(

Hmmm.  It sounds like your system is unable to keep all of the data cached in 
memory.  What else do you have going on on that machine?

> Explain gives me this result :

Please do "EXPLAIN ANALYZE" so that we can see where time is actually spent.

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Wed Aug 25 21:22:08 2004
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From: "Simon Riggs" 
To: "Daniel Ceregatti" , 
Subject: Re: What is the best way to do attribute/values?
Date: Thu, 26 Aug 2004 01:38:16 +0100
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Two more unusual suggestions:

1. Drop all the indexes and just do sequential scans (full table scans),
aiming as hard as possible to get the whole people table to fit in memory
(size says that should be easy - various ways) - and make sure you're using
8.0 so you have the best cache manager. This will at least give you
consistent performance on whatever attribute values searched on in user
queries. Dropping all the indexes will allow the query to optimize faster,
since it has only one path choice. Work out how many attributes it takes to
reduce the list of candidates to a manageable number, and include only those
factors into the table, effectively vertically partitioning the table,
thereby reducing the volume and increasing scan speed. Then redesign the
user interface so that they see a two-stage process, first stage is top N
common attributes, second stage is to further reduce that down using rarer
attributes, as well as using the output from the first table to index into
the second. Users then won't mind additional wait time.
(Experiment with: Horizontally partition the table into N pieces. Issue N
simultaneous queries to simulate a parallel query. Try N == 2 on your box)

2. You can try forcing the use of a Star Join optimization here:
Concatenate the attribute values into a single column, then index it. This
will be nearly unique. Cluster the table.
Permute the values of the attributes, to give you a list of concatenated
keys that would match, then join that list to the main table, using a join
via the index.
You can do this permutation by using a reference table per attribute, then
doing an unconstrained product join between all of the attribute tables
(avoid any indexes on them) and assembling the candidate keys into a single
temporary table. Then join the temp table to the main people table. This
will only work effectively if people's attributes are selected with some
discrimination, otherwise this optimisation will fail. You'd need to
constrain the user interface to "pick 20 out of the following 100 attribute
values" or some other heuristic to ensure a relatively low count, or use a
LIMIT on the query into the temp table.
This sounds long winded, but is essentially the route the Oracle optimizer
takes in performing a star join....you clearly know you're Oracle, so look
that up to confirm what I'm saying. (May not work as well if you use a
sub-select on PostgreSQL....)

Also, I'd categorise the Age, Height, Weight and Salary attributes and
everything else based upon most common ranges, so it will be just an
equality search on an integer assigned to that category, rather than a >
search. Order by the distance, don't search on it, it'll be quicker since
you'll only need to calculate it for the records that match...even if you do
get a few too many, it would be a shame to avoid somebody because they lived
1 mile outside of the stated radius.

The database sounds < 1 Gb in total logical volume, so 4Gb of RAM should be
easily sufficient.

Best Regards, Simon Riggs

> -----Original Message-----
> From: pgsql-performance-owner@postgresql.org
> [mailto:pgsql-performance-owner@postgresql.org]On Behalf Of Daniel
> Ceregatti
> Sent: 19 August 2004 19:03
> To: pgsql-performance@postgresql.org
> Subject: [PERFORM] What is the best way to do attribute/values?
>
>
> Hi list,
>
> I have a database with 1M "people" in it. Each person has about 20
> attributes, such as height, weight, eye color, etc. I need to be able to
> search for people based on these attributes. A search can be conducted
> on one attribute, all attributes, or any number in between. How would
> _you_ do this?
>
> I have already attempted to answer this. My attempts are detailed here:
>
> http://sh.nu/email.txt
>
> This is the email I was originally going to send to this list. Since
> it's so large, I decided to link to it instead. If you feel that it
> belongs in a post to the list, let me know, and I'll post again.
>
> I've discussed these attempts with people in #postgresql on
> irc.freenode.net. Agliodbs (I presume you know who this is) was very
> helpful, but in end was at a loss. I find myself in the same postition
> at this time. He suggested I contact this list.
>
> My ultimate goal is performance. This _must_ be fast. And by fast, I
> mean, < 1 second, for every permutation of the number of attributes
> searched for. Flexibility would be a bonus, but at this point I'll
> settle for something that's harder to maintain if I can get the speed
> gain I need.
>
> Thanks,
>
> Daniel Ceregatti
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster


From pgsql-performance-owner@postgresql.org  Wed Aug 25 22:13:16 2004
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From: Christopher Kings-Lynne 
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To: Mischa Sandberg 
Cc: pgsql-performance@postgresql.org
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
References: 
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> I see that PG has a one-shot CLUSTER command, but doesn't support
> continuously-updated clustered indexes.
> 
> What I infer from newsgroup browsing is, such an index is impossible,
> given the MVCC versioning of records (happy to learn I'm wrong).
> 
> I'd be curious to know what other people, who've crossed this same
> bridge from MSSQL or Oracle or Sybase to PG, have devised,
> faced with the same kind of desired performance gain for retrieving
> blocks of rows with the same partial key.

I just run clusterdb each weekend in a cron job...

Chris

From pgsql-performance-owner@postgresql.org  Thu Aug 26 01:49:19 2004
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Date: Thu, 26 Aug 2004 16:51:50 +1200
From: Mark Kirkwood 
Subject: Re: What is the best way to do attribute/values?
In-reply-to: <200408250959.15946.josh@agliodbs.com>
To: Josh Berkus 
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Josh Berkus wrote:

>Mark, Tim,
>
>  
>
>>select
>>	pav1.person_id
>>from
>>	person_attributes_vertical pav1
>>where
>>	   (    pav1.attribute_id = 1
>>	    and pav1.value_id in (2,3))
>>	or (    pav1.attribute_id = 2
>>	    and pav1.value_id in (2,3))
>>    
>>
>
>Not the same query, sorry.   Daniel's query yields all the person_id's which 
>have criteria A AND criteria B.   Yours gives all the person_id's which have 
>criteria A OR criteria B.
>
>  
>
Apologies, not thinking clearly enough there...


Maybe try out intersection :


select
    pav1.person_id
from
    person_attributes_vertical pav1
where
       (    pav1.attribute_id = 1
        and pav1.value_id in (2,3))
intersect
select
    pav1.person_id
from
    person_attributes_vertical pav1
where (    pav1.attribute_id = 2
        and pav1.value_id in (2,3))


In the advent that is unhelpful, I wonder about simplifying the 
situation and investigating how


select
    pav1.person_id
from
    person_attributes_vertical pav1
where
       pav1.attribute_id = 1


performs, compared to


select
    pav1.person_id
from
    person_attributes_vertical pav1
where
       (    pav1.attribute_id = 1
        and pav1.value_id in (2,3))


If the first performs ok and the second does not, It may be possible to 
get better times by doing some horrible re-writes :e.g:


select
    pav1.person_id
from
    person_attributes_vertical pav1
where
       (    pav1.attribute_id = 1
        and pav1.value_id||null in (2,3))


etc.


regards

Mark



    

From pgsql-performance-owner@postgresql.org  Thu Aug 26 03:16:02 2004
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Date: Thu, 26 Aug 2004 08:15:52 +0200 (CEST)
From: Dennis Bjorklund 
To: Richard Huxton 
Cc: David Price ,
	
Subject: Re: Optimizer Selecting Incorrect Index
In-Reply-To: <412CB487.6060704@archonet.com>
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On Wed, 25 Aug 2004, Richard Huxton wrote:

> >  Index Scan using trptserc on trans  (cost=0.00..465.10 rows=44 width=118)
> >    Index Cond: (trn_patno = 199999)
> >    Filter: ((trn_old_date >= '1994-08-23'::date) AND (trn_old_date <=
> > '2004-08-23'::date) AND (trn_bill_inc = 'B'::bpchar))
> > (687 rows)
> 
> >  Index Scan using todate on trans  (cost=0.00..105165.74 rows=1 width=143)
> >    Index Cond: ((trn_old_date >= '1994-08-23'::date) AND (trn_old_date <=
> > '2004-08-23'::date))
> >    Filter: ((trn_patno = 199999) AND (trn_bill_inc = 'B'::bpchar))
> > (713 rows)
> 
> These queries are different. The first returns 687 rows and the second 
> 713 rows.

The 687 and 713 are the number of rows in the plan, not the number of rows 
the queries return.

-- 
/Dennis Bj�rklund


From pgsql-performance-owner@postgresql.org  Thu Aug 26 04:22:16 2004
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Organization: Elma =?iso-8859-15?q?Ing=E9nierie?= Informatique
To: pgsql-performance@postgresql.org
Subject: Re: TSearch2 and optimisation ...
Date: Thu, 26 Aug 2004 09:22:01 +0200
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	<200408251650.53233.josh@agliodbs.com>
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Josh,

Le Jeudi 26 Ao�t 2004 01:50, Josh Berkus a �crit :
> > The request takes about 4 seconds ... I have about 1 400 000 records in
> > article and 36 000 records in site table ... it's a Bi-Pentium III 933
> > MHz server with 1 Gb memory ... I'm using Postgresql 7.4.5
> > For me this result is very very slow I really need a quicker result with
> > less than 1 second ...
> > The next time I call the same request I have got the result in 439 ms ...
> > but If I replace "Postgresql" in my find with "Linux" for example I will
> > get the next result in 5 seconds ... :o(
>
> Hmmm.  It sounds like your system is unable to keep all of the data cached
> in memory.  What else do you have going on on that machine?

There is an Apache + PHP running in same time ... 

> > Explain gives me this result :
>
> Please do "EXPLAIN ANALYZE" so that we can see where time is actually
> spent.

                                                         QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=10740.35..10743.73 rows=1351 width=190) (actual 
time=7054.603..7054.707 rows=139 loops=1)
   Sort Key: rank(a.idxfti, '\'postgresql\''::tsquery), a.r_date
   ->  Merge Join  (cost=4123.09..10670.10 rows=1351 width=190) (actual 
time=5476.749..7052.766 rows=139 loops=1)
         Merge Cond: ("outer".id_site = "inner".id_site)
         ->  Index Scan using site_id_site_key on site s  (cost=0.00..2846.52 
rows=35705 width=28) (actual time=43.985..1548.903 rows=34897 loops=1)
         ->  Sort  (cost=4123.09..4126.47 rows=1351 width=166) (actual 
time=5416.836..5416.983 rows=139 loops=1)
               Sort Key: a.id_site
               ->  Index Scan using idxfti_idx on article a  
(cost=0.00..4052.84 rows=1351 width=166) (actual time=109.766..5415.108 
rows=139 loops=1)
                     Index Cond: (idxfti @@ '\'postgresql\''::tsquery)
                     Filter: (idxfti @@ '\'postgresql\''::tsquery)
         SubPlan
           ->  Seq Scan on user_choice u  (cost=0.00..2.69 rows=1 width=4) 
(actual time=0.146..0.146 rows=0 loops=139)
                 Filter: ((id_site = $0) AND (id_user = 1))
 Total runtime: 7056.126 ms

Thanks for your help ...
-- 
Herv� Piedvache

Elma Ing�nierie Informatique
6 rue du Faubourg Saint-Honor�
F-75008 - Paris - France
Pho. 33-144949901
Fax. 33-144949902

From pgsql-performance-owner@postgresql.org  Thu Aug 26 07:17:43 2004
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Dennis Bjorklund wrote:
> On Wed, 25 Aug 2004, Richard Huxton wrote:
>>
>>These queries are different. The first returns 687 rows and the second 
>>713 rows.
> 
> 
> The 687 and 713 are the number of rows in the plan, not the number of rows 
> the queries return.

D'OH! Thanks Dennis

-- 
   Richard Huxton
   Archonet Ltd

From pgsql-performance-owner@postgresql.org  Thu Aug 26 08:04:38 2004
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	Thu, 26 Aug 2004 07:04:32 -0400
From: "David Price" 
To: "Tom Lane" ,
	"Richard Huxton" 
Cc: 
Subject: Re: Optimizer Selecting Incorrect Index 
Date: Thu, 26 Aug 2004 07:05:26 -0400
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Tom, your suspicions were correct - ANALYZE was not being run.

I run vacuumdb via a cron script during off hours.  After checking the
scripts on both systems, I found that on the system that was not functioning
correctly that the '-z' (analyze) command line option to vacuumdb was
missing.  After correcting it and re-running the script, the poorly
performing SQL query takes only a few seconds as opposed to 15 minutes.

Thank you for your help!
- David

-----Original Message-----
From: pgsql-performance-owner@postgresql.org
[mailto:pgsql-performance-owner@postgresql.org]On Behalf Of Tom Lane
Sent: Wednesday, August 25, 2004 3:08 PM
To: Richard Huxton
Cc: David Price; pgsql-performance@postgresql.org
Subject: Re: [PERFORM] Optimizer Selecting Incorrect Index


Richard Huxton  writes:
> Things to check:
> 1. postgresql.conf settings match - different costs could cause this
> 2. statistics on the two columns (trn_patno,trn_old_date) - if they
> differ considerably between systems that would also explain it.

The different estimated row counts could only come from #2.  I suspect
David has forgotten to run ANALYZE on the second system.

I agree that EXPLAIN VERBOSE output is not helpful...

			regards, tom lane

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From pgsql-performance-owner@postgresql.org  Thu Aug 26 09:07:44 2004
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From: Andrew Rawnsley 
Subject: Re: Anyone familiar with Apple Xserve RAID
Date: Thu, 26 Aug 2004 08:07:42 -0400
To: pgsql-performance@postgresql.org
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Just starting to work with one now, so I'll let people know what I 
find. There has been
some talk that the XServe RAID seems more optimized for streaming 
applications rather than
heavy random-access type applications, which really wouldn't surprise 
me given where they
probably expect to sell most of them (music/film). They gave us a very 
good price break, as
we are in an industry they wanted exposure in (financial services). If 
you want a pile of
storage at a good price point, its certainly worth considering.

The unit itself is built very well, and the admin tools are very good 
(OS X only, though). It and the
cards that come in the XServes use copper SFP cables/connections, which 
is good or
bad depending upon you're point of view. The switch Apple sells off of 
their web site
is a Vixel (recently bought by Emulex).

I have XServes hooked up at the moment, which work fine. My production 
DB machine
is a slackware box, which has tested out fine in initial tests with a 
QLogic HBA and the stock in-kernel
drivers. They're also 'certified' to work with Emulex cards, but IIRC 
Emulex doesn't do copper.
Emulex did open-source their driver code last year (right after I had 
to change an client's install
from my beloved Slack to RHAS because Emulex only had version-specific 
drivers....).

More as it happens.

On Aug 25, 2004, at 6:52 PM, Doug McNaught wrote:

> Josh Berkus  writes:
>
>> Robert,
>>
>>> Just curious if folks have ever used this for a postgresql server 
>>> and if
>>> they used it with OSX/BSD/Linux. Even if you haven't used it, if you
>>> know of something comparable I'd be interested.  TIA
>>
> \> Last I checked Apple was still shipping the XServes with SATA drives
>> and a PROMISE controller, both very consumer-grade (and not
>> server-grade) hardware.  I can't recommend the XServe as a database
>> platform.  SCSI still makes a difference for databases, more because
>> of the controllers than anything else.
>
> The XServe RAID is fibre-channel.
>
> -Doug
> -- 
> Let us cross over the river, and rest under the shade of the trees.
>    --T. J. Jackson, 1863
>
>
> ---------------------------(end of 
> broadcast)---------------------------
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>
--------------------

Andrew Rawnsley
President
The Ravensfield Digital Resource Group, Ltd.
(740) 587-0114
www.ravensfield.com


From pgsql-performance-owner@postgresql.org  Sun Aug 29 12:16:58 2004
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From: "Stefano Bonnin" 
To: 
Subject: Query performance problem in 8.0.0beta1
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Hi, I have just installed 8.0.0beta1 and I noticed that some query are slow=
er than 7.4.2 queries.

After a FULL VACUUM ANALYZE

***With 7.4.2***

explain analyze SELECT count(*) FROM "SNS_DATA" WHERE "Data_Arrivo_Campione=
" BETWEEN '2004-01-01 00:00:00' AND '2004-01-31 23:59:59' AND "Cod_Par" =3D=
 '17476'

gives

 Aggregate  (cost=3D46817.89..46817.89 rows=3D1 width=3D0) (actual time=3D4=
01.216..401.217 rows=3D1 loops=3D1)
   ->  Index Scan using snsdata_codpar on "SNS_DATA"  (cost=3D0.00..46817.2=
2 rows=3D268 width=3D0) (actual time=3D165.948..400.258 rows=3D744 loops=3D=
1)
         Index Cond: (("Cod_Par")::text =3D '17476'::text)
         Filter: (("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::times=
tamp without time zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:=
59'::timestamp without time zone))
 Total runtime: 401.302 ms

***while on 8.0.0***

the same query gives

---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
-----------------------------------------------------------------------
 Aggregate  (cost=3D93932.91..93932.91 rows=3D1 width=3D0) (actual time=3D1=
4916.371..14916.371 rows=3D1 loops=3D1)
   ->  Seq Scan on "SNS_DATA"  (cost=3D0.00..93930.14 rows=3D1108 width=3D0=
) (actual time=3D6297.152..14915.330 rows=3D744 loops=3D1)
         Filter: (("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::times=
tamp without time zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:=
59'::timestamp without time zone) AND (("Cod_Par")::text =3D '17476'::text))
 Total runtime: 14916.935 ms

And I if disable the seqscan
SET enable_seqscan =3D false;

I get the following Aggregate  (cost=3D158603.19..158603.19 rows=3D1 width=
=3D0) (actual time=3D4605.862..4605.863 rows=3D1 loops=3D1)
   ->  Index Scan using snsdata_codpar on "SNS_DATA"  (cost=3D0.00..158600.=
41 rows=3D1108 width=3D0) (actual time=3D2534.422..4604.865 rows=3D744 loop=
s=3D1)
         Index Cond: (("Cod_Par")::text =3D '17476'::text)
         Filter: (("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::times=
tamp without time zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:=
59'::timestamp without time zone))
 Total runtime: 4605.965 ms

The total runtime is bigger (x10 !!) than the old one.

The memory runtime parameters are=20
shared_buffer =3D 2048
work_mem =3D sort_mem =3D 2048

SNS_DATA shema is the following:

                         Table "public.SNS_DATA"
        Column        |            Type             |     Modifiers
----------------------+-----------------------------+--------------------
 Ordine               | integer                     | not null default 0
 Cod_Par              | character varying(100)      | not null
 Cod_Ana              | character varying(100)      | not null
 Valore               | character varying(255)      |
 Descriz              | character varying(512)      |
 Un_Mis               | character varying(70)       |
 hash                 | integer                     |
 valid                | boolean                     | default true
 alarm                | boolean                     | default false
 Cod_Luogo            | character varying(30)       |
 Data_Arrivo_Campione | timestamp without time zone |
 site_id              | integer                     |
 Cod_Luogo_v          | character varying(30)       |
 repeated_val         | boolean                     | default false
Indexes:
    "sns_data2_pkey" PRIMARY KEY, btree ("Ordine", "Cod_Ana", "Cod_Par")
    "sns_datacodluogo2" btree ("Cod_Luogo")
    "sns_datatimefield2" btree ("Data_Arrivo_Campione")
    "sns_siteid2" btree (site_id)
    "sns_valid2" btree ("valid")
    "snsdata_codana" btree ("Cod_Ana")
    "snsdata_codpar" btree ("Cod_Par")
Foreign-key constraints:
    "$2" FOREIGN KEY ("Cod_Ana") REFERENCES "SNS_ANA"("Cod_Ana") ON DELETE =
CASCADE
Triggers:
    sns_action_tr BEFORE INSERT OR UPDATE ON "SNS_DATA" FOR EACH ROW EXECUT=
E PROCEDURE sns_action()


Can it be a datatype conversion problem?
Thanks in advance!
Reds





------=_NextPart_000_0087_01C48B82.6F3FAD70
Content-Type: text/html;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable









Hi, I have just installed 8.0.0beta1 and I=
 noticed=20
that some query are slower than 7.4.2 queries.


 


After a FULL VACUUM ANALYZE


 


***With 7.4.2***


 


explain analyze SELECT count(*) FROM "SNS_=
DATA"=20
WHERE "Data_Arrivo_Campione" BETWEEN '2004-01-01 00:00:00' AND '2004-01-31=
=20
23:59:59' AND "Cod_Par" =3D '17476'


 


gives


 


 Aggregate  (cost=3D46817.89..46=
817.89=20
rows=3D1 width=3D0) (actual time=3D401.216..401.217 rows=3D1 loops=3D1)
=
  =20
->  Index Scan using snsdata_codpar on "SNS_DATA" =20
(cost=3D0.00..46817.22 rows=3D268 width=3D0) (actual time=3D165.948..400.25=
8 rows=3D744=20
loops=3D1)
         Index Cond:=
=20
(("Cod_Par")::text =3D=20
'17476'::text)
         Filter:=
=20
(("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::timestamp without t=
ime=20
zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:59'::timestamp =
without=20
time zone))
 Total runtime: 401.302 ms


 


***while on 8.0.0***


 


the same query gives


 


------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
-----
 Aggregate =20
(cost=3D93932.91..93932.91 rows=3D1 width=3D0) (actual time=3D14916.371..14=
916.371=20
rows=3D1 loops=3D1)
   ->  Seq Scan on "SNS_DATA" =
;=20
(cost=3D0.00..93930.14 rows=3D1108 width=3D0) (actual time=3D6297.152..1491=
5.330=20
rows=3D744 loops=3D1)
         F=
ilter:=20
(("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::timestamp without t=
ime=20
zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:59'::timestamp =
without=20
time zone) AND (("Cod_Par")::text =3D '17476'::text))
 Total runtim=
e:=20
14916.935 ms


And I if disable the seqscan


SET enable_seqscan =3D false;


 


I get the following Aggregate =20
(cost=3D158603.19..158603.19 rows=3D1 width=3D0) (actual time=3D4605.862..4=
605.863=20
rows=3D1 loops=3D1)
   ->  Index Scan using snsdata_co=
dpar on=20
"SNS_DATA"  (cost=3D0.00..158600.41 rows=3D1108 width=3D0) (actual=20
time=3D2534.422..4604.865 rows=3D744=20
loops=3D1)
         Index Cond:=
=20
(("Cod_Par")::text =3D=20
'17476'::text)
         Filter:=
=20
(("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::timestamp without t=
ime=20
zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:59'::timestamp =
without=20
time zone))
 Total runtime: 4605.965 ms


The total runtime is bigger (x10 !!) than =
the old=20
one.


 


The memory runtime parameters are <=
/DIV>

shared_buffer =3D 2048


work_mem =3D sort_mem =3D 2048


 


SNS_DATA shema is the following:

 


           =
            &nb=
sp;=20
Table "public.SNS_DATA"
       =20
Column       =20
|           =20
Type            =
;=20
|    =20
Modifiers
----------------------+-----------------------------+---------=
-----------
 Ordine        =
      =20
|=20
integer           &n=
bsp;        =20
| not null default=20
0
 Cod_Par         &nb=
sp;   =20
| character varying(100)      | not=20
null
 Cod_Ana         =
    =20
| character varying(100)      | not=20
null
 Valore         &=
nbsp;    =20
| character varying(255)     =20
|
 Descriz         &nb=
sp;   =20
| character varying(512)     =20
|
 Un_Mis         &nbs=
p;    =20
| character varying(70)      =20
|
 hash          =
      =20
|=20
integer           &n=
bsp;        =20
|
 valid          =
;     =20
|=20
boolean           &n=
bsp;        =20
| default=20
true
 alarm         &n=
bsp;     =20
|=20
boolean           &n=
bsp;        =20
| default=20
false
 Cod_Luogo        &nb=
sp;  =20
| character varying(30)      =20
|
 Data_Arrivo_Campione | timestamp without time zone=20
|
 site_id         &nb=
sp;   =20
|=20
integer           &n=
bsp;        =20
|
 Cod_Luogo_v         =
; |=20
character varying(30)      =20
|
 repeated_val         |=
=20
boolean           &n=
bsp;        =20
| default false
Indexes:
    "sns_data2_pkey" PRIMARY =
KEY,=20
btree ("Ordine", "Cod_Ana", "Cod_Par")
    "sns_datacodlu=
ogo2"=20
btree ("Cod_Luogo")
    "sns_datatimefield2" btree=20
("Data_Arrivo_Campione")
    "sns_siteid2" btree=20
(site_id)
    "sns_valid2" btree=20
("valid")
    "snsdata_codana" btree=20
("Cod_Ana")
    "snsdata_codpar" btree=20
("Cod_Par")
Foreign-key constraints:
    "$2" FOREIGN =
KEY=20
("Cod_Ana") REFERENCES "SNS_ANA"("Cod_Ana") ON DELETE=20
CASCADE
Triggers:
    sns_action_tr BEFORE INSERT OR U=
PDATE=20
ON "SNS_DATA" FOR EACH ROW EXECUTE PROCEDURE sns_action()


 


 


Can it be a datatype conversion=20
problem?


Thanks in advance!


Reds


 


 


 


 


 


------=_NextPart_000_0087_01C48B82.6F3FAD70--


From pgsql-performance-owner@postgresql.org  Thu Aug 26 12:13:34 2004
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	<200408251422.08366.josh@agliodbs.com>
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From: Tore Halset 
Subject: Re: Anyone familiar with Apple Xserve RAID
Date: Thu, 26 Aug 2004 17:13:24 +0200
To: pgsql-performance@postgresql.org
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On Aug 26, 2004, at 14:07, Andrew Rawnsley wrote:

> The unit itself is built very well, and the admin tools are very good=20
> (OS X only, though). It and the

The admin tools are supposed to work cross platform. From Apples=20
website: "This Java-based application provides an intuitive interface=20
for creating protected storage volumes, managing preferences and=20
monitoring storage hardware from any virtually any networked computer=20
over TCP/IP. That means you don=92t have to use a Mac to administer your=20
deployment, though, we=92d like you to, of course."

http://www.apple.com/xserve/raid/management.html

Regards,
  - Tore.

From pgsql-performance-owner@postgresql.org  Thu Aug 26 14:40:53 2004
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Cc: pgsql-performance@postgresql.org
From: Andrew Rawnsley 
Subject: Re: Anyone familiar with Apple Xserve RAID
Date: Thu, 26 Aug 2004 13:40:41 -0400
To: Tore Halset 
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Oops. My bad.

They must really want to sell those things if they're making them=20
completely platform independent...

On Aug 26, 2004, at 11:13 AM, Tore Halset wrote:

> On Aug 26, 2004, at 14:07, Andrew Rawnsley wrote:
>
>> The unit itself is built very well, and the admin tools are very good=20
>> (OS X only, though). It and the
>
> The admin tools are supposed to work cross platform. From Apples=20
> website: "This Java-based application provides an intuitive interface=20
> for creating protected storage volumes, managing preferences and=20
> monitoring storage hardware from any virtually any networked computer=20
> over TCP/IP. That means you don=92t have to use a Mac to administer your=
=20
> deployment, though, we=92d like you to, of course."
>
> http://www.apple.com/xserve/raid/management.html
>
> Regards,
>  - Tore.
>
> ---------------------------(end of=20
> broadcast)---------------------------
> TIP 1: subscribe and unsubscribe commands go to=20
> majordomo@postgresql.org
>
--------------------

Andrew Rawnsley
President
The Ravensfield Digital Resource Group, Ltd.
(740) 587-0114
www.ravensfield.com


From pgsql-performance-owner@postgresql.org  Thu Aug 26 14:49:27 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: =?iso-8859-15?q?Herv=E9=20Piedvache?= ,
	pgsql-performance@postgresql.org
Subject: Re: TSearch2 and optimisation ...
Date: Thu, 26 Aug 2004 10:48:58 -0700
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Herve'

> (cost=0.00..4052.84 rows=1351 width=166) (actual time=109.766..5415.108
> rows=139 loops=1)
>                      Index Cond: (idxfti @@ '\'postgresql\''::tsquery)
>                      Filter: (idxfti @@ '\'postgresql\''::tsquery)

 From this, it looks like your FTI index isn't fitting in your sort_mem.  
What's sort_mem at now?  Can you increase it?

Overall, though, I'm not sure you can get this sub-1s without a faster 
machine.   Although I'm doing FTI on about 25MB of FTI text on a 
single-processor machine, and getting 40ms response times, so maybe we can 
...

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Thu Aug 26 14:58:40 2004
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	Thu, 26 Aug 2004 10:58:33 PDT
Date: Thu, 26 Aug 2004 10:58:33 -0700 (PDT)
From: George Essig 
Subject: Re: TSearch2 and optimisation ...
To: pgsql-performance@postgresql.org
Cc: footcow@noos.fr
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Bill Footcow wrote:

...
> I have done a simple request, looking for title or description having Postgres 
> inside order by rank and date,  like this :
> SELECT a.title, a.id, a.url, to_char(a.r_date, 'DD/MM/YYYY HH24:MI:SS') as dt, 
> s.site_name, s.id_site, case when exists (select id_user from user_choice u 
> where u.id_site=s.id_site and u.id_user = 1) then 1 else 0 end as bookmarked
>     FROM article a, site s
>   WHERE s.id_site = a.id_site
>        AND idxfti @@ to_tsquery('postgresql')
>    ORDER BY rank(idxfti, to_tsquery('postgresql')) DESC, a.r_date DESC;
> 
> The request takes about 4 seconds ... I have about 1 400 000 records in 
> article and 36 000 records in site table ... it's a Bi-Pentium III 933 MHz 
> server with 1 Gb memory ... I'm using Postgresql 7.4.5
> For me this result is very very slow I really need a quicker result with less 
> than 1 second ...
> The next time I call the same request I have got the result in 439 ms ... but 
...

The first query is slow because the relevant index pages are not cached in memory.  Everyone
experiences this.  GiST indexes on tsvector columns can get really big.  You have done nothing
wrong.  When you have a lot of records, tsearch2 will not run fast without extensive performance
tuning.  

Read the following:

Optimization
http://www.sai.msu.su/~megera/postgres/gist/tsearch/V2/docs/oscon_tsearch2/optimization.html

stat function
http://www.sai.msu.su/~megera/oddmuse/index.cgi/Tsearch_V2_Notes
http://www.sai.msu.su/~megera/postgres/gist/tsearch/V2/docs/oscon_tsearch2/stat.html

Stop words
http://www.sai.msu.su/~megera/postgres/gist/tsearch/V2/docs/tsearch-V2-intro.html
http://www.sai.msu.su/~megera/postgres/gist/tsearch/V2/docs/oscon_tsearch2/stop_words.html

Multicolumn GiST index
http://www.sai.msu.su/~megera/postgres/gist/tsearch/V2/docs/oscon_tsearch2/multi_column_index.html

openfts-general mailing list archive
http://sourceforge.net/mailarchive/forum.php?forum=openfts-general

Try some of things out and let me know how it goes.

George Essig



From pgsql-performance-owner@postgresql.org  Thu Aug 26 15:03:10 2004
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From: Neil Cooper 
To: "pgsql-performance@postgresql.org" 
Subject: Disabling transaction/outdated-tuple behaviour
Date: Thu, 26 Aug 2004 14:02:55 -0400
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I am using a simple PostgreSQL 7.3 database in a soft-realtime
application.

I have a problem where an update on a record within a (fully indexed)
table containing less than ten records needs to occur as fast as
possible.

Immediately after performing a vaccum, updates take upto 50 milliseconds
to occur, however the update performance degrades over time, such that
after a few hours of continuous updates, each update takes about half a
second. Regular vacuuming improves the performance temporarily, but
during the vacuum operation (which takes upto 2 minutes), performance of
concurrent updates falls below an acceptable level (sometimes > 2
seconds per update).

According to the documentation, PostgreSQL keeps the old versions of the
tuples in case of use by other transactions (i.e. each update is
actually extending the table). I believe this behaviour is what is
causing my performance problem.

Is there a way to disable this behaviour such that an update operation
would overwrite the current record and does not generate an outdated
tuple each time? (My application does not need transactional support).
=20
I believe this would give me the performance gain I need, and would
eliminate the need for regular vacuuming too.
=20
Thanks in advance,

Neil Cooper.

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From pgsql-performance-owner@postgresql.org  Thu Aug 26 15:14:37 2004
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
From: "J. Andrew Rogers" 
To: pgsql-performance@postgresql.org
Cc: mischa.sandberg@telus.net
In-Reply-To: 
References: 
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On Tue, 2004-08-24 at 22:28, Mischa Sandberg wrote:
> I see that PG has a one-shot CLUSTER command, but doesn't support
> continuously-updated clustered indexes.
> 
> What I infer from newsgroup browsing is, such an index is impossible,
> given the MVCC versioning of records (happy to learn I'm wrong).


It is possible to have MVCC and ordered/indexed heaps, but it isn't
something you can just tack onto the currently supported types -- I
looked into this myself.  It would take substantial additional code
infrastructure to support it, basically an alternative heap system and
adding support for tables with odd properties to many parts of the
system.  Pretty non-trivial.

This is probably my #1 "I wish postgres had this feature" feature.  It
is a serious scalability enhancer for big systems and a pain to work
around not having.


> I'd be curious to know what other people, who've crossed this same
> bridge from MSSQL or Oracle or Sybase to PG, have devised,
> faced with the same kind of desired performance gain for retrieving
> blocks of rows with the same partial key.


The CLUSTER command is often virtually useless for precisely the kinds
of tables that need to be clustered.  My databases are on-line 24x7, and
the tables that are ideal candidates for clustering are in the range of
50-100 million rows. I can afford to lock these tables up for no more
than 5-10 minutes during off-peak in the hopes that no one notices, and
CLUSTER does not work remotely in the ballpark of that fast for tables
of that size.  People who can run CLUSTER in a cron job must either have
relatively small tables or regular large maintenance windows.


My solution, which may or may not work for you, was to write a table
partitioning system using the natural flexibility and programmability of
postgresql (e.g. table inheritance).  From this I automatically get a
roughly ordered heap according to the index I would cluster on, with
only slightly funky SQL access.  The end result works much better with
CLUSTER too, though CLUSTER is much less necessary at that point
because, at least for my particular purposes, the rows are mostly
ordered due to how the data was partitioned.

So there are ways to work around CLUSTER, but you'll have to be clever
and it will require tailoring the solution to your particular
requirements.


J. Andrew Rogers




From pgsql-performance-owner@postgresql.org  Thu Aug 26 15:18:59 2004
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Reply-To: 
From: "Matt Clark" 
To: "'Neil Cooper'" ,
	
Subject: Re: Disabling transaction/outdated-tuple behaviour
Date: Thu, 26 Aug 2004 19:18:52 +0100
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> Immediately after performing a vaccum, updates take upto 50=20
> milliseconds to occur, however the update performance=20
> degrades over time, such that after a few hours of continuous=20
> updates, each update takes about half a second. Regular=20
> vacuuming improves the performance temporarily, but during=20
> the vacuum operation (which takes upto 2 minutes),=20
> performance of concurrent updates falls below an acceptable=20
> level (sometimes > 2 seconds per update).

You must be doing an enormous number of updates!  You can vacuum as often as
you like, and should usually do so at least as often as the time it takes
for 'all' tuples to be updated.  So, in your case, every 10 updates.  OK,
that seems unnecessary, how about every 100 updates?=20

> According to the documentation, PostgreSQL keeps the old=20
> versions of the tuples in case of use by other transactions=20
> (i.e. each update is actually extending the table). I believe=20
> this behaviour is what is causing my performance problem.

Yes, it probably is.

> Is there a way to disable this behaviour such that an update=20
> operation would overwrite the current record and does not=20
> generate an outdated tuple each time? (My application does=20
> not need transactional support).

No, I don't believe there is.  If you really don't need transaction support
then you might want to reconsider whether postgres is really the right tool.

M


From pgsql-performance-owner@postgresql.org  Thu Aug 26 15:19:11 2004
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From: Bruce Momjian 
Message-Id: <200408261818.i7QIIrr09640@candle.pha.pa.us>
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
In-Reply-To: <1093544071.349.106.camel@vulture.corp.neopolitan.com>
To: "J. Andrew Rogers" 
Date: Thu, 26 Aug 2004 14:18:53 -0400 (EDT)
Cc: pgsql-performance@postgresql.org, mischa.sandberg@telus.net
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How do vendors actually implement auto-clustering?  I assume they move
rows around during quiet periods or have lots of empty space in each
value bucket.

---------------------------------------------------------------------------

J. Andrew Rogers wrote:
> On Tue, 2004-08-24 at 22:28, Mischa Sandberg wrote:
> > I see that PG has a one-shot CLUSTER command, but doesn't support
> > continuously-updated clustered indexes.
> > 
> > What I infer from newsgroup browsing is, such an index is impossible,
> > given the MVCC versioning of records (happy to learn I'm wrong).
> 
> 
> It is possible to have MVCC and ordered/indexed heaps, but it isn't
> something you can just tack onto the currently supported types -- I
> looked into this myself.  It would take substantial additional code
> infrastructure to support it, basically an alternative heap system and
> adding support for tables with odd properties to many parts of the
> system.  Pretty non-trivial.
> 
> This is probably my #1 "I wish postgres had this feature" feature.  It
> is a serious scalability enhancer for big systems and a pain to work
> around not having.
> 
> 
> > I'd be curious to know what other people, who've crossed this same
> > bridge from MSSQL or Oracle or Sybase to PG, have devised,
> > faced with the same kind of desired performance gain for retrieving
> > blocks of rows with the same partial key.
> 
> 
> The CLUSTER command is often virtually useless for precisely the kinds
> of tables that need to be clustered.  My databases are on-line 24x7, and
> the tables that are ideal candidates for clustering are in the range of
> 50-100 million rows. I can afford to lock these tables up for no more
> than 5-10 minutes during off-peak in the hopes that no one notices, and
> CLUSTER does not work remotely in the ballpark of that fast for tables
> of that size.  People who can run CLUSTER in a cron job must either have
> relatively small tables or regular large maintenance windows.
> 
> 
> My solution, which may or may not work for you, was to write a table
> partitioning system using the natural flexibility and programmability of
> postgresql (e.g. table inheritance).  From this I automatically get a
> roughly ordered heap according to the index I would cluster on, with
> only slightly funky SQL access.  The end result works much better with
> CLUSTER too, though CLUSTER is much less necessary at that point
> because, at least for my particular purposes, the rows are mostly
> ordered due to how the data was partitioned.
> 
> So there are ways to work around CLUSTER, but you'll have to be clever
> and it will require tailoring the solution to your particular
> requirements.
> 
> 
> J. Andrew Rogers
> 
> 
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 6: Have you searched our list archives?
> 
>                http://archives.postgresql.org
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

From pgsql-performance-owner@postgresql.org  Thu Aug 26 15:20:49 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: Neil Cooper ,
	"pgsql-performance@postgresql.org" 
Subject: Re: Disabling transaction/outdated-tuple behaviour
Date: Thu, 26 Aug 2004 11:20:20 -0700
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Neil,

> I am using a simple PostgreSQL 7.3 database in a soft-realtime
> application.

Then you're not going to like the answer I have for you, see below.

> I have a problem where an update on a record within a (fully indexed)
> table containing less than ten records needs to occur as fast as
> possible.

Have you considered dropping the indexes?  On such a small table, they won't 
be used, and they are detracting significantly from your update speed.

> Immediately after performing a vaccum, updates take upto 50 milliseconds
> to occur, however the update performance degrades over time, such that
> after a few hours of continuous updates, each update takes about half a
> second. Regular vacuuming improves the performance temporarily, but
> during the vacuum operation (which takes upto 2 minutes), performance of
> concurrent updates falls below an acceptable level (sometimes > 2
> seconds per update).

This is "normal" depending on your platform and concurrent activity.   More 
frequent vacuums would take less time each.   What is your max_fsm_pages set 
to?   Increasing this may decrease the necessity of vacuums as well as 
speeding them up.  Also, are you vacuuming the whole DB or just that table?  
2 mintues seems like a long time; I can vacuum a 100GB database in less than 
4.

> Is there a way to disable this behaviour such that an update operation
> would overwrite the current record and does not generate an outdated
> tuple each time? (My application does not need transactional support).

No.  Our ACID Transaction compliance depends on "that behaviour" (MVCC).  We 
don't offer PostgreSQL in a "non-ACID mode".   If your application truly does 
not need transactional support, you may want to consider an embedded database 
instead, such as BerkeleyDB or SQLite.    PostgreSQL has a *lot* of "baggage" 
associated with having 99.99% incorruptable transactions.

Alternately, you may also want to take a look at TelegraphCG, a derivative of 
PostgreSQL designed to handle "streaming data".  They may have already 
conquered some of your difficulties for you.  
http://telegraph.cs.berkeley.edu/

Were I you, I would start with tuning the database first through 
PostgreSQL.conf and a careful look at my hardware usage and DB maintenance.   
Then I would consider testing 8.0, which has some specific improvements 
designed to address some of the problems you are having.   Particularly, 
Jan's Background Writer and Lazy Vacuum.

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Thu Aug 26 15:33:02 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: Bruce Momjian ,
	"J. Andrew Rogers" 
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
Date: Thu, 26 Aug 2004 11:32:30 -0700
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Bruce,

> How do vendors actually implement auto-clustering?  I assume they move
> rows around during quiet periods or have lots of empty space in each
> value bucket.

That's how SQL Server does it.   In old versions (6.5) you had to manually 
send commands to update the cluster, same as PG.   Also, when you create a 
cluster (or an index or table for that matter) you can manually set an amount 
of "space" to be held open on each data page for updates.

Also keep in mind that SQL Server, as a "single-user database" has a much 
easier time with this.  They don't have to hold several versions of an index 
in memory and collapse it into a single version at commit time.

All that being said, we could do a better job of "auto-balancing" clustered 
tables.   I believe that someone was working on this in Hackers through what 
they called "B-Tree Tables".  What happened to that?

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Thu Aug 26 16:04:52 2004
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
From: "J. Andrew Rogers" 
To: Bruce Momjian 
Cc: pgsql-performance@postgresql.org, mischa.sandberg@telus.net
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On Thu, 2004-08-26 at 11:18, Bruce Momjian wrote:
> How do vendors actually implement auto-clustering?  I assume they move
> rows around during quiet periods or have lots of empty space in each
> value bucket.


As far as I know, Oracle does it by having a B-Tree organized heap (a
feature introduced around v8 IIRC), basically making the primary key
index and the heap the same physical structure.  Any non-index columns
are stored in the index along with the index columns.  Implementing it
is slightly weird because searching the index and selecting the rows
from the heap are not separate operations.

The major caveat to having tables of this type is that you can only have
a primary key index.  No other indexes are possible because the "heap"
constantly undergoes local reorganizations if you have a lot of write
traffic, the same kind of reorganization you would normally expect in a
BTree index.

The performance improvements come from two optimizations.  First, you
have to touch significantly fewer blocks to get all the rows, even
compared to a CLUSTERed heap.  Second, the footprint is smaller and
plays nicely with the buffer cache.

When I've used these types of heaps in Oracle 8 on heavily used tables
with tens of millions of rows, we frequently got a 10x or better
performance improvement on queries against those tables.  It is only
really useful for tables with vast quantities of relatively small rows,
but it can be a lifesaver in those cases.


J. Andrew Rogers



From pgsql-performance-owner@postgresql.org  Thu Aug 26 16:10:58 2004
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From: Kevin Barnard 
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Actually you are both are right and wrong.  The XRaid uses FibreChannel 
to communicate to the host machine(s).  The Raid controller is a 
FibreChannel controller.  After that there is a FibreChannel to UltraATA 
conversion for each drive, separate ATA bus for each drive.

What I am curious about is if this setup gets around ATA fsync problems, 
where the drive reports the write before it is actually performed.


Josh Berkus wrote:

>Guys,
>
>  
>
>>the XServe/XRaid comes with FibreChannel
>>    
>>
>
>I stand corrected.   That should help things some; it makes it more of a small 
>tradeoff between performance and storage size for the drives.
>
>  
>

-- 
Kevin Barnard
Speed Fulfillment and Call Center
kbarnard@speedfc.com
214-258-0120


--------------010605050705080208010809
Content-Type: text/html; charset=us-ascii
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Actually you are both are right and wrong.  The XRaid uses FibreChannel
to communicate to the host machine(s).  The Raid controller is a
FibreChannel controller.  After that there is a FibreChannel to
UltraATA conversion for each drive, separate ATA bus for each drive.



What I am curious about is if this setup gets around ATA fsync
problems, where the drive reports the write before it is actually
performed.





Josh Berkus wrote:



  
Guys,

  

  

    
the XServe/XRaid comes with FibreChannel
    

  

  

I stand corrected.   That should help things some; it makes it more of a small 
tradeoff between performance and storage size for the drives.

  






-- 
Kevin Barnard
Speed Fulfillment and Call Center
kbarnard@speedfc.com
214-258-0120




--------------010605050705080208010809--

From pgsql-performance-owner@postgresql.org  Thu Aug 26 16:30:33 2004
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
Date: Thu, 26 Aug 2004 21:30:24 +0200
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Thread-Topic: [PERFORM] Equivalent praxis to CLUSTERED INDEX?
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From: "Magnus Hagander" 
To: "J. Andrew Rogers" ,
	"Bruce Momjian" 
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>> How do vendors actually implement auto-clustering?  I assume=20
>they move
>> rows around during quiet periods or have lots of empty space in each
>> value bucket.
>
>
>As far as I know, Oracle does it by having a B-Tree organized heap (a
>feature introduced around v8 IIRC), basically making the primary key
>index and the heap the same physical structure.  Any non-index columns
>are stored in the index along with the index columns.  Implementing it
>is slightly weird because searching the index and selecting the rows
>from the heap are not separate operations.

Almost the same for MSSQL. The clustered index is always forced unique.
If you create a non-unique clustered index, SQLServer will internally
pad it with random (or is it sequential? Can't remember right now) data
to make each key unique. The clustered index contains all the data
fields - both the index key and the other columns from the database.

It does support non-clustered indexes as well on the same table. Any
"secondary index" will then contain the index key and the primary key
value. This means a lookup in a non-clustered index means a two-step
index lookup: First look in the non-clustered index for the clustered
key. Then look in the clustered index for the rest of the data.=20

Naturally a non-clustered index needs better selectivity before it's
actually used than a clustered index does.

IIRC, SQL Server always creates clustered indexes by default for primary
keys.


//Magnus

From pgsql-performance-owner@postgresql.org  Thu Aug 26 16:30:50 2004
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From: =?iso-8859-15?q?Herv=E9_Piedvache?= 
To: pgsql-performance@postgresql.org
Subject: Re: TSearch2 and optimisation ...
Date: Thu, 26 Aug 2004 21:30:40 +0200
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Le Jeudi 26 Ao=FBt 2004 19:48, Josh Berkus a =E9crit :
> Herve'
>
> > (cost=3D0.00..4052.84 rows=3D1351 width=3D166) (actual time=3D109.766..=
5415.108
> > rows=3D139 loops=3D1)
> >                      Index Cond: (idxfti @@ '\'postgresql\''::tsquery)
> >                      Filter: (idxfti @@ '\'postgresql\''::tsquery)
> >
> >From this, it looks like your FTI index isn't fitting in your sort_mem.
>
> What's sort_mem at now?  Can you increase it?

shared_buffers =3D 3000
sort_mem =3D 10240

> Overall, though, I'm not sure you can get this sub-1s without a faster
> machine.   Although I'm doing FTI on about 25MB of FTI text on a
> single-processor machine, and getting 40ms response times, so maybe we can
> ...

Sorry I missed understand what you mean here ...=20
You tell me to upgrade the hardware but you manage a 25 Mb with a single=20
processor ?? What you mean ?
My database is about 450 Mb ...

Regards,
--=20
Bill Footcow


From pgsql-performance-owner@postgresql.org  Thu Aug 26 16:48:53 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: "Magnus Hagander" ,
	"J. Andrew Rogers" ,
	"Bruce Momjian" 
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
Date: Thu, 26 Aug 2004 12:48:25 -0700
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Magnus,

> IIRC, SQL Server always creates clustered indexes by default for primary
> keys.

I think that's a per-database setting; certainly the ones I admin do not.

However, since SQL Server orders its data pages, those data pages tend to be 
in the order of the primary key regardless if there is no clustered index.

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Thu Aug 26 16:54:16 2004
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From: Doug McNaught 
Subject: Re: Anyone familiar with Apple Xserve RAID
Date: Thu, 26 Aug 2004 15:54:04 -0400
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Kevin Barnard  writes:

>    Actually you are both are right and wrong.  The XRaid uses
>    FibreChannel to communicate to the host machine(s).  The Raid
>    controller is a FibreChannel controller.  After that there is a
>    FibreChannel to UltraATA conversion for each drive, separate ATA bus
>    for each drive.
>    What I am curious about is if this setup gets around ATA fsync
>    problems, where the drive reports the write before it is actually
>    performed.

Good point.

(a) The FC<->ATA unit hopefully has a battery-backed cache, which
    would make the whole thing more robust against power loss.
(b) Since Apple is the vendor for the drive units, they can buy ATA
    drives that don't lie about cache flushes.  Whether they do or not
    is definitely a question.  ;)

-Doug
-- 
Let us cross over the river, and rest under the shade of the trees.
   --T. J. Jackson, 1863


From pgsql-performance-owner@postgresql.org  Thu Aug 26 17:01:24 2004
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Doug McNaught wrote:

>Kevin Barnard  writes:
>
>  
>
>>   Actually you are both are right and wrong.  The XRaid uses
>>   FibreChannel to communicate to the host machine(s).  The Raid
>>   controller is a FibreChannel controller.  After that there is a
>>   FibreChannel to UltraATA conversion for each drive, separate ATA bus
>>   for each drive.
>>   What I am curious about is if this setup gets around ATA fsync
>>   problems, where the drive reports the write before it is actually
>>   performed.
>>    
>>
>
>Good point.
>
>(a) The FC<->ATA unit hopefully has a battery-backed cache, which
>    would make the whole thing more robust against power loss.
>(b) Since Apple is the vendor for the drive units, they can buy ATA
>    drives that don't lie about cache flushes.  Whether they do or not
>    is definitely a question.  ;)
>  
>

FYI:    http://developer.apple.com/technotes/tn/pdf/tn1040.pdf   a tech 
note on write cache flushing.

A bit dated now, but perhaps some other tech note from Apple has more 
recent information.

-- Alan

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From: Andrew Rawnsley 
Subject: Re: Anyone familiar with Apple Xserve RAID
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On Aug 26, 2004, at 3:54 PM, Doug McNaught wrote:

> Kevin Barnard  writes:
>
>>    Actually you are both are right and wrong.  The XRaid uses
>>    FibreChannel to communicate to the host machine(s).  The Raid
>>    controller is a FibreChannel controller.  After that there is a
>>    FibreChannel to UltraATA conversion for each drive, separate ATA 
>> bus
>>    for each drive.
>>    What I am curious about is if this setup gets around ATA fsync
>>    problems, where the drive reports the write before it is actually
>>    performed.
>
> Good point.
>
> (a) The FC<->ATA unit hopefully has a battery-backed cache, which
>     would make the whole thing more robust against power loss.

Each controller is battery backed (pretty beefy batteries too). 
Actually, they are optional,
but if you spend the money for the unit and leave off the battery you 
should
have your head examined.


> (b) Since Apple is the vendor for the drive units, they can buy ATA
>     drives that don't lie about cache flushes.  Whether they do or not
>     is definitely a question.  ;)

Given what they charge for them I would like to think so...but who 
knows...

The ones in mine are from Hitachi, model #HDS722525VLAT80.

>
> -Doug
> -- 
> Let us cross over the river, and rest under the shade of the trees.
>    --T. J. Jackson, 1863
>
>
> ---------------------------(end of 
> broadcast)---------------------------
> TIP 1: subscribe and unsubscribe commands go to 
> majordomo@postgresql.org
>
--------------------

Andrew Rawnsley
President
The Ravensfield Digital Resource Group, Ltd.
(740) 587-0114
www.ravensfield.com


From pgsql-performance-owner@postgresql.org  Thu Aug 26 17:44:08 2004
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
From: "J. Andrew Rogers" 
To: Magnus Hagander 
Cc: Bruce Momjian ,
	pgsql-performance@postgresql.org, mischa.sandberg@telus.net
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On Thu, 2004-08-26 at 12:30, Magnus Hagander wrote:
> Almost the same for MSSQL. The clustered index is always forced unique.
> If you create a non-unique clustered index, SQLServer will internally
> pad it with random (or is it sequential? Can't remember right now) data
> to make each key unique. The clustered index contains all the data
> fields - both the index key and the other columns from the database.
> 
> It does support non-clustered indexes as well on the same table. Any
> "secondary index" will then contain the index key and the primary key
> value. This means a lookup in a non-clustered index means a two-step
> index lookup: First look in the non-clustered index for the clustered
> key. Then look in the clustered index for the rest of the data.


Ah, okay.  I see how that would work for a secondary index, though it
would make for a slow secondary index.  Neat workaround.  For all I
know, current versions of Oracle may support secondary indexes on
index-organized tables; all this Postgres usage over the last couple
years has made my Oracle knowledge rusty.


> IIRC, SQL Server always creates clustered indexes by default for primary
> keys.


That would surprise me actually.  For some types of tables, e.g. ones
with multiple well-used indexes or large rows, index-organizing the heap
could easily give worse performance than a normal index/heap pair
depending on access patterns.  It also tends to be more prone to having
locking contention under some access patterns.  This is one of those
options that needs to be used knowledgeably; it is not a general
architectural improvement that you would want to apply to every table
all the time.


J. Andrew Rogers




From pgsql-performance-owner@postgresql.org  Sun Aug 29 12:15:31 2004
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
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Ummm ... not quite. In MSSQL/Sybase/Oracle, a clustered index maintains 
its space saturation as part of each update operation. High activity 
does indeed result in less-full pages (typically 60-80% full for tables 
with heavy deletions or rowsize changes). To bring the percentage back 
up, you run DBCC INDEXDEFRAG, which also does what you'd expect of a 
normal file defragmenter -- put related disk pages together on the platter.

But the performance difference is hardly as severe as I gather it can be 
if you neglect to vacuum.

As for SQL Server being a 'single-user database' ... ummm ... no, I 
don't think so. I'm REALLY happy to be shut of the Microsoft world, but 
MSSQL 7/2000/2005 is a serious big DB engine. It also has some serious 
bright heads behind it. They hired Goetz Graefe and Paul (aka Per-Ake) 
Larsen away from academia, and it shows, in the join and aggregate 
processing. I'll be a happy camper if I manage to contribute something
to PG that honks the way their stuff does. Happy to discuss, too.

Josh Berkus wrote:
> Bruce,
> 
> 
>>How do vendors actually implement auto-clustering?  I assume they move
>>rows around during quiet periods or have lots of empty space in each
>>value bucket.
> 
> 
> That's how SQL Server does it.   In old versions (6.5) you had to manually 
> send commands to update the cluster, same as PG.   Also, when you create a 
> cluster (or an index or table for that matter) you can manually set an amount 
> of "space" to be held open on each data page for updates.
> 
> Also keep in mind that SQL Server, as a "single-user database" has a much 
> easier time with this.  They don't have to hold several versions of an index 
> in memory and collapse it into a single version at commit time.
> 
> All that being said, we could do a better job of "auto-balancing" clustered 
> tables.   I believe that someone was working on this in Hackers through what 
> they called "B-Tree Tables".  What happened to that?
> 

From pgsql-performance-owner@postgresql.org  Thu Aug 26 18:31:55 2004
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From: Gaetano Mendola 
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Bruce Momjian wrote:
> How do vendors actually implement auto-clustering?  I assume they move
> rows around during quiet periods or have lots of empty space in each
> value bucket.
> 
> ---------------------------------------------------------------------------

IIRC informix doesn't have it, and you have to recluster periodically
the table. After having clustered the table with an index in order to
recluster the table with another index you have to release the previous
one ( ALTER index TO NOT CLUSTER ), the CLUSTER is an index attribute and
each table can have only one index with that attribute ON.


Regards
Gaetano Mendola



From pgsql-performance-owner@postgresql.org  Sun Aug 29 12:16:51 2004
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
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J. Andrew Rogers wrote:
> On Thu, 2004-08-26 at 12:30, Magnus Hagander wrote:
>>IIRC, SQL Server always creates clustered indexes by default for primary
>>keys.
> 
> That would surprise me actually.

Yaz, it should. It doesn't ALWAYS create clustered (unique) index for 
primary keys, but clustered is the default if you just specify

CREATE TABLE Foo (col1, ...
	,PRIMARY KEY(col1, ...)
)

Saying PRIMARY KEY NONCLUSTERED(...) is how you override the default.
	
((Weird to be discussing so much MSSQL here))

From pgsql-performance-owner@postgresql.org  Sun Aug 29 12:15:59 2004
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Sheer nitpick here...

A B-tree is where the records (data) live at all levels of the tree;
B+ tree is where the records are only at the leaf level.
That's what Knuth calls them, anyway.

Clustered indexes for all known dbs are true B+ trees.
Nonclustered indexes could be B-trees (probably aren't),
since there's no big fanout penalty for storing the little
(heap) row locators everywhere at all levels.

J. Andrew Rogers wrote:
> As far as I know, Oracle does it by having a B-Tree organized heap (a
> feature introduced around v8 IIRC), basically making the primary key
> index and the heap the same physical structure.  
...

From pgsql-performance-owner@postgresql.org  Thu Aug 26 19:36:30 2004
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
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Thread-Topic: [PERFORM] Equivalent praxis to CLUSTERED INDEX?
Thread-Index: AcSLtF0iLWfopjgTSa69GezGy0M88QACwW/w
From: "Gregory S. Williamson" 
To: "Gaetano Mendola" ,
	"Bruce Momjian" ,
	
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FWIW,

Informix does allow the fragmentation of data over named dbspaces by round-=
robin and expression; this is autosupporting as long as the dba keeps enoug=
h space available. You may also fragment the index although there are some =
variations depending on type of Informix (XPS, etc.); this is available in =
at least 9.3 ... I have never used the index fragmentation as its own beast=
, but the fragmenting of data works like a charm for spreadling load over m=
ore disks.

Greg Williamson
DBA
GlobeXplorer LLC

-----Original Message-----
From: Gaetano Mendola [mailto:mendola@bigfoot.com]
Sent: Thursday, August 26, 2004 2:10 PM
To: Bruce Momjian; pgsql-performance@postgresql.org
Subject: Re: [PERFORM] Equivalent praxis to CLUSTERED INDEX?


Bruce Momjian wrote:
> How do vendors actually implement auto-clustering?  I assume they move
> rows around during quiet periods or have lots of empty space in each
> value bucket.
>=20
> -------------------------------------------------------------------------=
--

IIRC informix doesn't have it, and you have to recluster periodically
the table. After having clustered the table with an index in order to
recluster the table with another index you have to release the previous
one ( ALTER index TO NOT CLUSTER ), the CLUSTER is an index attribute and
each table can have only one index with that attribute ON.


Regards
Gaetano Mendola



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From pgsql-performance-owner@postgresql.org  Thu Aug 26 22:45:53 2004
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
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	pgsql-performance@postgresql.org, mischa.sandberg@telus.net
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Updated TODO item:

        o Automatically maintain clustering on a table

        This would require some background daemon to maintain clustering
        during periods of low usage. It might also require tables to be only
        paritally filled for easier reorganization.  It also might require
        creating a merged heap/index data file so an index lookup would
        automatically access the heap data too.

---------------------------------------------------------------------------

J. Andrew Rogers wrote:
> On Thu, 2004-08-26 at 12:30, Magnus Hagander wrote:
> > Almost the same for MSSQL. The clustered index is always forced unique.
> > If you create a non-unique clustered index, SQLServer will internally
> > pad it with random (or is it sequential? Can't remember right now) data
> > to make each key unique. The clustered index contains all the data
> > fields - both the index key and the other columns from the database.
> > 
> > It does support non-clustered indexes as well on the same table. Any
> > "secondary index" will then contain the index key and the primary key
> > value. This means a lookup in a non-clustered index means a two-step
> > index lookup: First look in the non-clustered index for the clustered
> > key. Then look in the clustered index for the rest of the data.
> 
> 
> Ah, okay.  I see how that would work for a secondary index, though it
> would make for a slow secondary index.  Neat workaround.  For all I
> know, current versions of Oracle may support secondary indexes on
> index-organized tables; all this Postgres usage over the last couple
> years has made my Oracle knowledge rusty.
> 
> 
> > IIRC, SQL Server always creates clustered indexes by default for primary
> > keys.
> 
> 
> That would surprise me actually.  For some types of tables, e.g. ones
> with multiple well-used indexes or large rows, index-organizing the heap
> could easily give worse performance than a normal index/heap pair
> depending on access patterns.  It also tends to be more prone to having
> locking contention under some access patterns.  This is one of those
> options that needs to be used knowledgeably; it is not a general
> architectural improvement that you would want to apply to every table
> all the time.
> 
> 
> J. Andrew Rogers
> 
> 
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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Cc: "J. Andrew Rogers" ,
	Magnus Hagander ,
	pgsql-performance@postgresql.org, mischa.sandberg@telus.net
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
References: <200408270145.i7R1jop04185@candle.pha.pa.us>
In-Reply-To: <200408270145.i7R1jop04185@candle.pha.pa.us>
From: Greg Stark 
Organization: The Emacs Conspiracy; member since 1992
Date: 26 Aug 2004 23:39:42 -0400
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Bruce Momjian  writes:

> Updated TODO item:
> 
>         o Automatically maintain clustering on a table
> 
>         This would require some background daemon to maintain clustering
>         during periods of low usage. It might also require tables to be only
>         paritally filled for easier reorganization.  It also might require
>         creating a merged heap/index data file so an index lookup would
>         automatically access the heap data too.

Fwiw, I would say the first "would" is also a "might". None of the previous
discussions here presumed a maintenance daemon. The discussions before talked
about a mechanism to try to place new tuples as close as possible to the
proper index position.

I would also suggest making some distinction between a cluster system similar
to what we have now but improved to maintain the clustering continuously, and
an actual index-organized-table where the tuples are actually only stored in a
btree structure.

They're two different approaches to similar problems. But they might both be
useful to have, and have markedly different implementation details.

-- 
greg


From pgsql-performance-owner@postgresql.org  Fri Aug 27 01:35:13 2004
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From: Bruce Momjian 
Message-Id: <200408270435.i7R4Z7N25250@candle.pha.pa.us>
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
In-Reply-To: <87pt5dnta9.fsf@stark.xeocode.com>
To: Greg Stark 
Date: Fri, 27 Aug 2004 00:35:07 -0400 (EDT)
Cc: "J. Andrew Rogers" ,
	Magnus Hagander ,
	pgsql-performance@postgresql.org, mischa.sandberg@telus.net
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OK, new wording:

        o Automatically maintain clustering on a table

        This might require some background daemon to maintain clustering
        during periods of low usage. It might also require tables to be only
        paritally filled for easier reorganization.  Another idea would
        be to create a merged heap/index data file so an index lookup would
        automatically access the heap data too.


---------------------------------------------------------------------------

Greg Stark wrote:
> 
> Bruce Momjian  writes:
> 
> > Updated TODO item:
> > 
> >         o Automatically maintain clustering on a table
> > 
> >         This would require some background daemon to maintain clustering
> >         during periods of low usage. It might also require tables to be only
> >         paritally filled for easier reorganization.  It also might require
> >         creating a merged heap/index data file so an index lookup would
> >         automatically access the heap data too.
> 
> Fwiw, I would say the first "would" is also a "might". None of the previous
> discussions here presumed a maintenance daemon. The discussions before talked
> about a mechanism to try to place new tuples as close as possible to the
> proper index position.
> 
> I would also suggest making some distinction between a cluster system similar
> to what we have now but improved to maintain the clustering continuously, and
> an actual index-organized-table where the tuples are actually only stored in a
> btree structure.
> 
> They're two different approaches to similar problems. But they might both be
> useful to have, and have markedly different implementation details.
> 
> -- 
> greg
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

From pgsql-performance-owner@postgresql.org  Fri Aug 27 03:27:24 2004
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	Thu, 26 Aug 2004 23:27:16 PDT
Date: Thu, 26 Aug 2004 23:27:16 -0700 (PDT)
From: my ho 
Subject: Re: postgresql performance with multimedia
To: Jan Wieck 
Cc: pgsql-performance@postgresql.org
In-Reply-To: <412C71F1.4030902@Yahoo.com>
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Hi,
> For your "streaming" purposes I strongly recommend
> you do it in your 
> application with the appropriate thread model. A
> relational database 
> management system is not a multimedia cache.

That's actually what i plan to do with postgreSQL,
maybe tailor it to suit with a multimedia streaming
database. Well, i could do it in the application level
but i think it's also worth a try with the database
itself.

> They are only stored in that way on initial load and
> if the load is done 
> with a single process. And don't you rely on this
> for the future. Right 
> now, if you ever update or delete tuples, that order
> changes already.

does the buffer manager have any idea what table that
buf belongs to? (can we add 'rel' variable to sbufdesc
in buf_internals.h and update it everytime we add new
entry to the buffer cahe?) And then we take in to
account which relation the data in the buffer belongs
to in the buf replacement algorithm or in the
read-ahead policy.

> Also keep in mind that large values are not stored
> inline, but in an 
> extra "TOAST" relation.
This is how i store my video file: break them in to
small chunks and store each part in a row of a table. 

regards,
MThi 



	
		
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From pgsql-performance-owner@postgresql.org  Fri Aug 27 03:54:24 2004
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From: "Stefano Bonnin" 
To: 
Subject: Query performance issue with 8.0.0beta1
Date: Fri, 27 Aug 2004 08:57:43 +0200
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Hi, I have just installed 8.0.0beta1 and I noticed that some query are slow=
er than 7.4.2 queries.

After:
pg_dump my_database >mydb.sql (from 7.4.2)
psql my_new_database   Index Scan using snsdata_codpar on "SNS_DATA"  (cost=3D0.00..46817.2=
2 rows=3D268 width=3D0) (actual time=3D165.948..400.258 rows=3D744 loops=3D=
1)
         Index Cond: (("Cod_Par")::text =3D '17476'::text)
         Filter: (("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::times=
tamp without time zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:=
59'::timestamp without time zone))
 Total runtime: 401.302 ms

***while on 8.0.0***

the same query gives

---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
-----------------------------------------------------------------------
 Aggregate  (cost=3D93932.91..93932.91 rows=3D1 width=3D0) (actual time=3D1=
4916.371..14916.371 rows=3D1 loops=3D1)
   ->  Seq Scan on "SNS_DATA"  (cost=3D0.00..93930.14 rows=3D1108 width=3D0=
) (actual time=3D6297.152..14915.330 rows=3D744 loops=3D1)
         Filter: (("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::times=
tamp without time zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:=
59'::timestamp without time zone) AND (("Cod_Par")::text =3D '17476'::text))
 Total runtime: 14916.935 ms

And I if disable the seqscan
SET enable_seqscan =3D false;

I get the following:

Aggregate  (cost=3D158603.19..158603.19 rows=3D1 width=3D0) (actual time=3D=
4605.862..4605.863 rows=3D1 loops=3D1)
   ->  Index Scan using snsdata_codpar on "SNS_DATA"  (cost=3D0.00..158600.=
41 rows=3D1108 width=3D0) (actual time=3D2534.422..4604.865 rows=3D744 loop=
s=3D1)
         Index Cond: (("Cod_Par")::text =3D '17476'::text)
         Filter: (("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::times=
tamp without time zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:=
59'::timestamp without time zone))
 Total runtime: 4605.965 ms

The total runtime is bigger (x10 !!) than the old one.

The memory runtime parameters are=20
shared_buffer =3D 2048
work_mem =3D sort_mem =3D 2048

SNS_DATA shema is the following:

                         Table "public.SNS_DATA"
        Column        |            Type             |     Modifiers
----------------------+-----------------------------+--------------------
 Ordine               | integer                     | not null default 0
 Cod_Par              | character varying(100)      | not null
 Cod_Ana              | character varying(100)      | not null
 Valore               | character varying(255)      |
 Descriz              | character varying(512)      |
 Un_Mis               | character varying(70)       |
 hash                 | integer                     |
 valid                | boolean                     | default true
 alarm                | boolean                     | default false
 Cod_Luogo            | character varying(30)       |
 Data_Arrivo_Campione | timestamp without time zone |
 site_id              | integer                     |
 Cod_Luogo_v          | character varying(30)       |
 repeated_val         | boolean                     | default false
Indexes:
    "sns_data2_pkey" PRIMARY KEY, btree ("Ordine", "Cod_Ana", "Cod_Par")
    "sns_datacodluogo2" btree ("Cod_Luogo")
    "sns_datatimefield2" btree ("Data_Arrivo_Campione")
    "sns_siteid2" btree (site_id)
    "sns_valid2" btree ("valid")
    "snsdata_codana" btree ("Cod_Ana")
    "snsdata_codpar" btree ("Cod_Par")
Foreign-key constraints:
    "$2" FOREIGN KEY ("Cod_Ana") REFERENCES "SNS_ANA"("Cod_Ana") ON DELETE =
CASCADE
Triggers:
    sns_action_tr BEFORE INSERT OR UPDATE ON "SNS_DATA" FOR EACH ROW EXECUT=
E PROCEDURE sns_action()

The table has 2M of records
Can it be a datatype conversion issue?
Can it be depend on the the type of restore (with COPY commands)?
I have no idea.

Thanks in advance!
Reds

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Hi, I have just installed 8.0.0beta1 and I=
 noticed=20
that some query are slower than 7.4.2 queries.


 


After:


pg_dump my_database >mydb.sql (from=20
7.4.2)


psql my_new_database <mydb.sql (to 8.0.0 with COPY instead of=20
INSERT)


FULL VACUUM ANALYZE


 


***With the old db on 7.4.2***


 


explain analyze SELECT count(*) FROM "SNS_=
DATA"=20
WHERE "Data_Arrivo_Campione" BETWEEN '2004-01-01 00:00:00' AND '2004-01-31=
=20
23:59:59' AND "Cod_Par" =3D '17476'


 


gives


 


 Aggregate  (cost=3D46817.89..46=
817.89=20
rows=3D1 width=3D0) (actual time=3D401.216..401.217 rows=3D1 loops=3D1)
=
  =20
->  Index Scan using snsdata_codpar on "SNS_DATA" =20
(cost=3D0.00..46817.22 rows=3D268 width=3D0) (actual time=3D165.948..400.25=
8 rows=3D744=20
loops=3D1)
         Index Cond:=
=20
(("Cod_Par")::text =3D=20
'17476'::text)
         Filter:=
=20
(("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::timestamp without t=
ime=20
zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:59'::timestamp =
without=20
time zone))
 Total runtime: 401.302 ms


 


***while on 8.0.0***


 


the same query gives


 


------------------------------------------------------------------=
---------------------------------------------------------------------------=
---------------------------------------------------------------------------=
-----
 Aggregate =20
(cost=3D93932.91..93932.91 rows=3D1 width=3D0) (actual time=3D14916.371..14=
916.371=20
rows=3D1 loops=3D1)
   ->  Seq Scan on "SNS_DATA" =
;=20
(cost=3D0.00..93930.14 rows=3D1108 width=3D0) (actual time=3D6297.152..1491=
5.330=20
rows=3D744 loops=3D1)
         F=
ilter:=20
(("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::timestamp without t=
ime=20
zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:59'::timestamp =
without=20
time zone) AND (("Cod_Par")::text =3D '17476'::text))
 Total runtim=
e:=20
14916.935 ms


And I if disable the seqscan


SET enable_seqscan =3D false;


 


I get the following:


 


Aggregate  (cost=3D158603.19..158603.=
19 rows=3D1=20
width=3D0) (actual time=3D4605.862..4605.863 rows=3D1 loops=3D1)
 &=
nbsp;=20
->  Index Scan using snsdata_codpar on "SNS_DATA" =20
(cost=3D0.00..158600.41 rows=3D1108 width=3D0) (actual time=3D2534.422..460=
4.865=20
rows=3D744 loops=3D1)
         I=
ndex=20
Cond: (("Cod_Par")::text =3D=20
'17476'::text)
         Filter:=
=20
(("Data_Arrivo_Campione" >=3D '2004-01-01 00:00:00'::timestamp without t=
ime=20
zone) AND ("Data_Arrivo_Campione" <=3D '2004-01-31 23:59:59'::timestamp =
without=20
time zone))
 Total runtime: 4605.965 ms


The total runtime is bigger (x10 !!) than =
the old=20
one.


 


The memory runtime parameters are <=
/DIV>

shared_buffer =3D 2048


work_mem =3D sort_mem =3D 2048


 


SNS_DATA shema is the following:

 


           =
            &nb=
sp;=20
Table "public.SNS_DATA"
       =20
Column       =20
|           =20
Type            =
;=20
|    =20
Modifiers
----------------------+-----------------------------+---------=
-----------
 Ordine        =
      =20
|=20
integer           &n=
bsp;        =20
| not null default=20
0
 Cod_Par         &nb=
sp;   =20
| character varying(100)      | not=20
null
 Cod_Ana         =
    =20
| character varying(100)      | not=20
null
 Valore         &=
nbsp;    =20
| character varying(255)     =20
|
 Descriz         &nb=
sp;   =20
| character varying(512)     =20
|
 Un_Mis         &nbs=
p;    =20
| character varying(70)      =20
|
 hash          =
      =20
|=20
integer           &n=
bsp;        =20
|
 valid          =
;     =20
|=20
boolean           &n=
bsp;        =20
| default=20
true
 alarm         &n=
bsp;     =20
|=20
boolean           &n=
bsp;        =20
| default=20
false
 Cod_Luogo        &nb=
sp;  =20
| character varying(30)      =20
|
 Data_Arrivo_Campione | timestamp without time zone=20
|
 site_id         &nb=
sp;   =20
|=20
integer           &n=
bsp;        =20
|
 Cod_Luogo_v         =
; |=20
character varying(30)      =20
|
 repeated_val         |=
=20
boolean           &n=
bsp;        =20
| default false
Indexes:
    "sns_data2_pkey" PRIMARY =
KEY,=20
btree ("Ordine", "Cod_Ana", "Cod_Par")
    "sns_datacodlu=
ogo2"=20
btree ("Cod_Luogo")
    "sns_datatimefield2" btree=20
("Data_Arrivo_Campione")
    "sns_siteid2" btree=20
(site_id)
    "sns_valid2" btree=20
("valid")
    "snsdata_codana" btree=20
("Cod_Ana")
    "snsdata_codpar" btree=20
("Cod_Par")
Foreign-key constraints:
    "$2" FOREIGN =
KEY=20
("Cod_Ana") REFERENCES "SNS_ANA"("Cod_Ana") ON DELETE=20
CASCADE
Triggers:
    sns_action_tr BEFORE INSERT OR U=
PDATE=20
ON "SNS_DATA" FOR EACH ROW EXECUTE PROCEDURE sns_action()


 


The table has 2M of records


Can it be a datatype conversion issue?


Can it be depend on the the type of restore (with COPY commands)?


I have no idea.


 


Thanks in advance!


Reds

 


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From pgsql-performance-owner@postgresql.org  Fri Aug 27 05:32:06 2004
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	for pgsql-performance@postgresql.org; Fri, 27 Aug 2004 08:26:36 GMT
From: Gaetano Mendola 
X-Newsgroups: comp.databases.postgresql.performance
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
Date: Fri, 27 Aug 2004 10:26:26 +0200
Organization: PYRENET Midi-pyrenees Provider
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Greg Stark wrote:

> The discussions before talked about a mechanism to try to place new 
 > tuples as close as possible to the proper index position.

Means this that an index shall have a "fill factor" property, similar to
Informix one ?

 From the manual:


The FILLFACTOR option takes effect only when you build an index on a table
that contains more than 5,000 rows and uses more than 100 table pages, when
you create an index on a fragmented table, or when you create a fragmented
index on a nonfragmented table.
Use the FILLFACTOR option to provide for expansion of an index at a later
date or to create compacted indexes.
When the index is created, the database server initially fills only that
percentage of the nodes specified with the FILLFACTOR value.

# Providing a Low Percentage Value
If you provide a low percentage value, such as 50, you allow room for growth
in your index. The nodes of the index initially fill to a certain percentage and
contain space for inserts. The amount of available space depends on the
number of keys in each page as well as the percentage value.
For example, with a 50-percent FILLFACTOR value, the page would be half
full and could accommodate doubling in size. A low percentage value can
result in faster inserts and can be used for indexes that you expect to grow.


# Providing a High Percentage Value
If you provide a high percentage value, such as 99, your indexes are
compacted, and any new index inserts result in splitting nodes. The
maximum density is achieved with 100 percent. With a 100-percent
FILLFACTOR value, the index has no room available for growth; any
additions to the index result in splitting the nodes.
A 99-percent FILLFACTOR value allows room for at least one insertion per
node. A high percentage value can result in faster selects and can be used for
indexes that you do not expect to grow or for mostly read-only indexes.




Regards
Gaetano Mendola





From pgsql-performance-owner@postgresql.org  Fri Aug 27 05:49:37 2004
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From: Russell Smith 
To: pgsql-performance@postgresql.org
Subject: Re: Query performance issue with 8.0.0beta1
Date: Fri, 27 Aug 2004 18:48:08 +1000
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7.4.2
>  Aggregate  (cost=46817.89..46817.89 rows=1 width=0) (actual time=401.216..401.217 rows=1 loops=1)
>    ->  Index Scan using snsdata_codpar on "SNS_DATA"  (cost=0.00..46817.22 rows=268 width=0) (actual time=165.948..400.258 rows=744 loops=1)
>          Index Cond: (("Cod_Par")::text = '17476'::text)
>          Filter: (("Data_Arrivo_Campione" >= '2004-01-01 00:00:00'::timestamp without time zone) AND ("Data_Arrivo_Campione" <= '2004-01-31 23:59:59'::timestamp without time zone))
>  Total runtime: 401.302 ms
> 
Row counts are out by a factor of 3, on the low side. so the planner will guess index is better, which it is.

> ***while on 8.0.0***
>  Aggregate  (cost=93932.91..93932.91 rows=1 width=0) (actual time=14916.371..14916.371 rows=1 loops=1)
>    ->  Seq Scan on "SNS_DATA"  (cost=0.00..93930.14 rows=1108 width=0) (actual time=6297.152..14915.330 rows=744 loops=1)
>          Filter: (("Data_Arrivo_Campione" >= '2004-01-01 00:00:00'::timestamp without time zone) AND ("Data_Arrivo_Campione" <= '2004-01-31 23:59:59'::timestamp without time zone) AND (("Cod_Par")::text = '17476'::text))
>  Total runtime: 14916.935 ms
Planner guesses that 1108 row should be returned, which is out by less, but on the high side.
Big question is given there are 2M rows, why does returning 1108 rows, less than 1% result in a sequence scan.
Usually the selectivity on the index is bad, try increasing the stats target on the column.

I know 8.0 has new stats anaylsis code, which could be effecting how it choses the plan. But it would still
require a good amount of stats to get it to guess correctly.

Increase stats and see if the times improve.

> 
> And I if disable the seqscan
> SET enable_seqscan = false;
> 
> I get the following:
> 
> Aggregate  (cost=158603.19..158603.19 rows=1 width=0) (actual time=4605.862..4605.863 rows=1 loops=1)
>    ->  Index Scan using snsdata_codpar on "SNS_DATA"  (cost=0.00..158600.41 rows=1108 width=0) (actual time=2534.422..4604.865 rows=744 loops=1)
>          Index Cond: (("Cod_Par")::text = '17476'::text)
>          Filter: (("Data_Arrivo_Campione" >= '2004-01-01 00:00:00'::timestamp without time zone) AND ("Data_Arrivo_Campione" <= '2004-01-31 23:59:59'::timestamp without time zone))
>  Total runtime: 4605.965 ms
> 
> The total runtime is bigger (x10 !!) than the old one.
Did you run this multiple times, or is this the first time.  If it had to get the data off disk it will be slower.
Are you sure that it's coming from disk in this and the 7.4 case? or both from memory.
If 7.4 is from buffer_cache, or kernel_cache, and 8.0 is from disk you are likely to get A LOT slower.

> 
> The memory runtime parameters are 
> shared_buffer = 2048
> work_mem = sort_mem = 2048
> 
[ snip ]

> The table has 2M of records
> Can it be a datatype conversion issue?
That should not be an issue in 8.0, at least for the simple type conversions.  like int8 to int4.
I'm not 100% sure which ones were added, and which were not, but the query appears to cast everything correctly anyway.

> Can it be depend on the the type of restore (with COPY commands)?
Shouldn't and VACUUM FULL ANALYZE will make the table as small as possible.  The row order may be different
on disk, but the planner won't know that, and it's a bad plan causing the problem.

> I have no idea.
> 
> Thanks in advance!
> Reds
> 
Regards

Russell Smith.

From pgsql-performance-owner@postgresql.org  Fri Aug 27 13:24:02 2004
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From: Bruce Momjian 
Message-Id: <200408271623.i7RGNvK05464@candle.pha.pa.us>
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
In-Reply-To: 
To: Gaetano Mendola 
Date: Fri, 27 Aug 2004 12:23:57 -0400 (EDT)
Cc: pgsql-performance@postgresql.org
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I had FILLFACTOR in the TODO list until just a few months ago, but
because no one had discussed it in 3-4 years, I removed the item.  I
have added mention now in the auto-cluster section because that actually
seems like the only good reason for a non-100% fillfactor.  I don't
think our ordinary btrees have enough of a penalty for splits to make a
non-full fillfactor worthwhile, but having a non-full fillfactor for
autocluster controls how often items have to be shifted around.

---------------------------------------------------------------------------

Gaetano Mendola wrote:
> Greg Stark wrote:
> 
> > The discussions before talked about a mechanism to try to place new 
>  > tuples as close as possible to the proper index position.
> 
> Means this that an index shall have a "fill factor" property, similar to
> Informix one ?
> 
>  From the manual:
> 
> 
> The FILLFACTOR option takes effect only when you build an index on a table
> that contains more than 5,000 rows and uses more than 100 table pages, when
> you create an index on a fragmented table, or when you create a fragmented
> index on a nonfragmented table.
> Use the FILLFACTOR option to provide for expansion of an index at a later
> date or to create compacted indexes.
> When the index is created, the database server initially fills only that
> percentage of the nodes specified with the FILLFACTOR value.
> 
> # Providing a Low Percentage Value
> If you provide a low percentage value, such as 50, you allow room for growth
> in your index. The nodes of the index initially fill to a certain percentage and
> contain space for inserts. The amount of available space depends on the
> number of keys in each page as well as the percentage value.
> For example, with a 50-percent FILLFACTOR value, the page would be half
> full and could accommodate doubling in size. A low percentage value can
> result in faster inserts and can be used for indexes that you expect to grow.
> 
> 
> # Providing a High Percentage Value
> If you provide a high percentage value, such as 99, your indexes are
> compacted, and any new index inserts result in splitting nodes. The
> maximum density is achieved with 100 percent. With a 100-percent
> FILLFACTOR value, the index has no room available for growth; any
> additions to the index result in splitting the nodes.
> A 99-percent FILLFACTOR value allows room for at least one insertion per
> node. A high percentage value can result in faster selects and can be used for
> indexes that you do not expect to grow or for mostly read-only indexes.
> 
> 
> 
> 
> Regards
> Gaetano Mendola
> 
> 
> 
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 7: don't forget to increase your free space map settings
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

From pgsql-performance-owner@postgresql.org  Fri Aug 27 13:31:43 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: Bruce Momjian ,
	Gaetano Mendola 
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
Date: Fri, 27 Aug 2004 09:31:06 -0700
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Bruce,

What happened to the B-Tree Table patch discussed on Hackers ad nauseum last 
winter?

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Fri Aug 27 13:32:49 2004
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From: Bruce Momjian 
Message-Id: <200408271632.i7RGWh206951@candle.pha.pa.us>
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
In-Reply-To: <200408270931.06191.josh@agliodbs.com>
To: Josh Berkus 
Date: Fri, 27 Aug 2004 12:32:43 -0400 (EDT)
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Josh Berkus wrote:
> Bruce,
> 
> What happened to the B-Tree Table patch discussed on Hackers ad nauseum last 
> winter?

I don't remember that. The only issue I remember is sorting btree index
by heap tid on creation.  We eventually got that into CVS for 8.0.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

From pgsql-performance-owner@postgresql.org  Fri Aug 27 13:51:18 2004
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From: Adi Alurkar 
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
Date: Fri, 27 Aug 2004 09:51:00 -0700
To: pgsql-performance@postgresql.org
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Greetings,

I am not sure if this applies only to clustering but for storage in 
general,

IIRC  Oracle has 2 parameters that can be set at table creation :
from Oracle docs

PCTFREE integer :
Specify the percentage of space in each data block of the table, object 
table OID index, or partition reserved for future updates to the 
table's rows. The value of PCTFREE must be a value from 0 to 99. A 
value of 0 allows the entire block to be filled by inserts of new rows. 
The default value is 10. This value reserves 10% of each block for 
updates to existing rows and allows inserts of new rows to fill a 
maximum of 90% of each block.
PCTFREE has the same function in the PARTITION description and in the 
statements that create and alter clusters, indexes, materialized views, 
and materialized view logs. The combination of PCTFREE and PCTUSED 
determines whether new rows will be inserted into existing data blocks 
or into new blocks.

PCTUSED integer
Specify the minimum percentage of used space that Oracle maintains for 
each data block of the table, object table OID index, or 
index-organized table overflow data segment. A block becomes a 
candidate for row insertion when its used space falls below PCTUSED. 
PCTUSED is specified as a positive integer from 0 to 99 and defaults to 
40.
PCTUSED has the same function in the PARTITION description and in the 
statements that create and alter clusters, materialized views, and 
materialized view logs.
PCTUSED is not a valid table storage characteristic for an 
index-organized table (ORGANIZATION INDEX).
The sum of PCTFREE and PCTUSED must be equal to or less than 100. You 
can use PCTFREE and PCTUSED together to utilize space within a table 
more efficiently.

PostgreSQL could take some hints from the above.

On Aug 27, 2004, at 1:26 AM, Gaetano Mendola wrote:

> Greg Stark wrote:
>
>> The discussions before talked about a mechanism to try to place new
> > tuples as close as possible to the proper index position.
>
> Means this that an index shall have a "fill factor" property, similar 
> to
> Informix one ?
>
> From the manual:
>
>
> The FILLFACTOR option takes effect only when you build an index on a 
> table
> that contains more than 5,000 rows and uses more than 100 table pages, 
> when
> you create an index on a fragmented table, or when you create a 
> fragmented
> index on a nonfragmented table.
> Use the FILLFACTOR option to provide for expansion of an index at a 
> later
> date or to create compacted indexes.
> When the index is created, the database server initially fills only 
> that
> percentage of the nodes specified with the FILLFACTOR value.
>
> # Providing a Low Percentage Value
> If you provide a low percentage value, such as 50, you allow room for 
> growth
> in your index. The nodes of the index initially fill to a certain 
> percentage and
> contain space for inserts. The amount of available space depends on the
> number of keys in each page as well as the percentage value.
> For example, with a 50-percent FILLFACTOR value, the page would be half
> full and could accommodate doubling in size. A low percentage value can
> result in faster inserts and can be used for indexes that you expect 
> to grow.
>
>
> # Providing a High Percentage Value
> If you provide a high percentage value, such as 99, your indexes are
> compacted, and any new index inserts result in splitting nodes. The
> maximum density is achieved with 100 percent. With a 100-percent
> FILLFACTOR value, the index has no room available for growth; any
> additions to the index result in splitting the nodes.
> A 99-percent FILLFACTOR value allows room for at least one insertion 
> per
> node. A high percentage value can result in faster selects and can be 
> used for
> indexes that you do not expect to grow or for mostly read-only indexes.
>
>
>
>
> Regards
> Gaetano Mendola
>
>
>
>
>
> ---------------------------(end of 
> broadcast)---------------------------
> TIP 7: don't forget to increase your free space map settings
>
>
--
Adi Alurkar (DBA sf.NET) 
1024D/79730470 A491 5724 74DE 956D 06CB  D844 6DF1 B972 7973 0470



From pgsql-performance-owner@postgresql.org  Fri Aug 27 13:52:26 2004
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From: andrew@pillette.com
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Subject: Re: Query performance issue with 8.0.0beta1
To: "Stefano Bonnin" 
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Is it possible (to mix two threads) that you had CLUSTERed the table on the old database in a way that retrieved the records in this query faster?

From pgsql-performance-owner@postgresql.org  Sun Aug 29 12:16:50 2004
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Subject: Why does a simple query not use an obvious index?
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The query:
    select count(*) from billing where timestamp > now()-60

should obviously use the index

    CREATE INDEX billing_timestamp_idx ON billing USING btree ("timestamp"
timestamp_ops);

on a table with 1400000 rows.

But it uses a Seq Scan. If I set enable_seqscan=no, it indicates a queryplan
could not be calculated.

Why does this simple query not use the timestamp index, and how can I get it
to?

Thanks, Jack

     Jack Kerkhof
      Research & Development
      jack.kerkhof@guest-tek.com
      www.guest-tek.com
      1.866.509.1010 3480

--------------------------------------------------------------------------

      Guest-Tek is a leading provider of broadband technology solutions for
the hospitality industry. Guest-Tek's GlobalSuite� high-speed Internet
solution enables hotels to offer their guests the convenience of wired
and/or wireless broadband Internet access from guest rooms, meeting rooms
and public areas.



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	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable







The=20
query:




    select count(*) from billing where timestamp &g=
t;=20
now()-60


should obvi=
ously use=20
the index 


    CREATE INDEX billing_timestamp_idx ON billing USING btree =
("timestamp" timestamp_ops);


on a table =
with=20
1400000 rows.


But it uses=
 a Seq=20
Scan. If I set enable_seqscan=3Dno, it indicates a queryplan could not be=
=20
calculated. 


Why does this simple query not use the timestamp index, and how ca=
n I get=20
it to?


Thanks, Jack



  
  

    
    
      
Jack=20
      Kerkhof
Research & Development
jack.kerkhof@guest-tek.com
www.guest-tek.com
1.866.509=
.1010=20
      3480

  

    
      


      

      
Guest-Tek is a =
leading=20
      provider of broadband technology solutions for the hospitality indust=
ry.=20
      Guest-Tek's GlobalSuite=99 high-speed Internet solution enables hotel=
s to=20
      offer their guests the convenience of wired and/or wireless broadband=
=20
      Internet access from guest rooms, meeting rooms and public areas.=20
      


 


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From pgsql-performance-owner@postgresql.org  Fri Aug 27 14:15:09 2004
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From: Josh Berkus 
Organization: Aglio Database Solutions
To: "Stefano Bonnin" ,
	
Subject: Re: Query performance issue with 8.0.0beta1
Date: Fri, 27 Aug 2004 10:14:29 -0700
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Stefano,

> Hi, I have just installed 8.0.0beta1 and I noticed that some query are
> slower than 7.4.2 queries.

Seems unlikely.   How have you configured postgresql.conf?    DID you 
configure it for the 8.0 database?

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Fri Aug 27 14:27:39 2004
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From: Bruce Momjian 
Message-Id: <200408271727.i7RHR7Z13191@candle.pha.pa.us>
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
In-Reply-To: <4661B1AE-F849-11D8-8B8C-000A95C4BD7A@sf.net>
To: Adi Alurkar 
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But what is the advantage of non-full pages in Oracle?

---------------------------------------------------------------------------

Adi Alurkar wrote:
> Greetings,
> 
> I am not sure if this applies only to clustering but for storage in 
> general,
> 
> IIRC  Oracle has 2 parameters that can be set at table creation :
> from Oracle docs
> 
> PCTFREE integer :
> Specify the percentage of space in each data block of the table, object 
> table OID index, or partition reserved for future updates to the 
> table's rows. The value of PCTFREE must be a value from 0 to 99. A 
> value of 0 allows the entire block to be filled by inserts of new rows. 
> The default value is 10. This value reserves 10% of each block for 
> updates to existing rows and allows inserts of new rows to fill a 
> maximum of 90% of each block.
> PCTFREE has the same function in the PARTITION description and in the 
> statements that create and alter clusters, indexes, materialized views, 
> and materialized view logs. The combination of PCTFREE and PCTUSED 
> determines whether new rows will be inserted into existing data blocks 
> or into new blocks.
> 
> PCTUSED integer
> Specify the minimum percentage of used space that Oracle maintains for 
> each data block of the table, object table OID index, or 
> index-organized table overflow data segment. A block becomes a 
> candidate for row insertion when its used space falls below PCTUSED. 
> PCTUSED is specified as a positive integer from 0 to 99 and defaults to 
> 40.
> PCTUSED has the same function in the PARTITION description and in the 
> statements that create and alter clusters, materialized views, and 
> materialized view logs.
> PCTUSED is not a valid table storage characteristic for an 
> index-organized table (ORGANIZATION INDEX).
> The sum of PCTFREE and PCTUSED must be equal to or less than 100. You 
> can use PCTFREE and PCTUSED together to utilize space within a table 
> more efficiently.
> 
> PostgreSQL could take some hints from the above.
> 
> On Aug 27, 2004, at 1:26 AM, Gaetano Mendola wrote:
> 
> > Greg Stark wrote:
> >
> >> The discussions before talked about a mechanism to try to place new
> > > tuples as close as possible to the proper index position.
> >
> > Means this that an index shall have a "fill factor" property, similar 
> > to
> > Informix one ?
> >
> > From the manual:
> >
> >
> > The FILLFACTOR option takes effect only when you build an index on a 
> > table
> > that contains more than 5,000 rows and uses more than 100 table pages, 
> > when
> > you create an index on a fragmented table, or when you create a 
> > fragmented
> > index on a nonfragmented table.
> > Use the FILLFACTOR option to provide for expansion of an index at a 
> > later
> > date or to create compacted indexes.
> > When the index is created, the database server initially fills only 
> > that
> > percentage of the nodes specified with the FILLFACTOR value.
> >
> > # Providing a Low Percentage Value
> > If you provide a low percentage value, such as 50, you allow room for 
> > growth
> > in your index. The nodes of the index initially fill to a certain 
> > percentage and
> > contain space for inserts. The amount of available space depends on the
> > number of keys in each page as well as the percentage value.
> > For example, with a 50-percent FILLFACTOR value, the page would be half
> > full and could accommodate doubling in size. A low percentage value can
> > result in faster inserts and can be used for indexes that you expect 
> > to grow.
> >
> >
> > # Providing a High Percentage Value
> > If you provide a high percentage value, such as 99, your indexes are
> > compacted, and any new index inserts result in splitting nodes. The
> > maximum density is achieved with 100 percent. With a 100-percent
> > FILLFACTOR value, the index has no room available for growth; any
> > additions to the index result in splitting the nodes.
> > A 99-percent FILLFACTOR value allows room for at least one insertion 
> > per
> > node. A high percentage value can result in faster selects and can be 
> > used for
> > indexes that you do not expect to grow or for mostly read-only indexes.
> >
> >
> >
> >
> > Regards
> > Gaetano Mendola
> >
> >
> >
> >
> >
> > ---------------------------(end of 
> > broadcast)---------------------------
> > TIP 7: don't forget to increase your free space map settings
> >
> >
> --
> Adi Alurkar (DBA sf.NET) 
> 1024D/79730470 A491 5724 74DE 956D 06CB  D844 6DF1 B972 7973 0470
> 
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 6: Have you searched our list archives?
> 
>                http://archives.postgresql.org
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

From pgsql-performance-owner@postgresql.org  Fri Aug 27 14:39:39 2004
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From: "Jeremy Dunn" 
To: 
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
Date: Fri, 27 Aug 2004 13:39:35 -0400
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> -----Original Message-----
> From: pgsql-performance-owner@postgresql.org 
> [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of 
> Bruce Momjian
> Sent: Friday, August 27, 2004 1:27 PM
> To: Adi Alurkar
> Cc: pgsql-performance@postgresql.org
> Subject: Re: [PERFORM] Equivalent praxis to CLUSTERED INDEX?
> 
> 
> 
> But what is the advantage of non-full pages in Oracle?
> 

One advantage has to do with updates of variable-length columns, e.g.
varchars.

If the block is fully packed with data, an update to a varchar column
that makes the column wider, causes "row-chaining".  This means that a
portion of the row is stored in a different data block, which may be
somewhere completely different in the storage array.  Retrieving that
row (or even just that column from that row) as a unit may now require
additional disk seek(s).

Leaving some space for updates in each data block doesn't prevent this
problem completely, but mitigates it to a certain extent.  If for
instance a row is typically inserted with a null value for a varchar
column, but the application developer knows it will almost always get
updated with some value later on, then leaving a certain percentage of
empty space in each block allocated to that table makes sense.

Conversely, if you know that your data is never going to get updated
(e.g. a data warehousing application), you might specify to pack the
blocks as full as possible.  This makes for the most efficient data
retrieval performance.

- Jeremy


From pgsql-performance-owner@postgresql.org  Fri Aug 27 14:40:04 2004
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From: Adi Alurkar 
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
Date: Fri, 27 Aug 2004 10:39:38 -0700
To: pgsql-performance@postgresql.org
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IIRC it it to reduce the "overflow" of data or what oracle calls  
chained rows. i.e if a table has variable length columns and 10 rows  
get inserted into a datapage, if this datapage is full and one of the  
variable length field gets updated the row will now "overflow" into  
another datapage, but if the datapage is created with an appropriate  
amount of free space the updated row will be stored in one single  
datapage.

On Aug 27, 2004, at 10:27 AM, Bruce Momjian wrote:

>
> But what is the advantage of non-full pages in Oracle?
>
> ----------------------------------------------------------------------- 
> ----
>
> Adi Alurkar wrote:
>> Greetings,
>>
>> I am not sure if this applies only to clustering but for storage in
>> general,
>>
>> IIRC  Oracle has 2 parameters that can be set at table creation :
>> from Oracle docs
>>
>> PCTFREE integer :
>> Specify the percentage of space in each data block of the table,  
>> object
>> table OID index, or partition reserved for future updates to the
>> table's rows. The value of PCTFREE must be a value from 0 to 99. A
>> value of 0 allows the entire block to be filled by inserts of new  
>> rows.
>> The default value is 10. This value reserves 10% of each block for
>> updates to existing rows and allows inserts of new rows to fill a
>> maximum of 90% of each block.
>> PCTFREE has the same function in the PARTITION description and in the
>> statements that create and alter clusters, indexes, materialized  
>> views,
>> and materialized view logs. The combination of PCTFREE and PCTUSED
>> determines whether new rows will be inserted into existing data blocks
>> or into new blocks.
>>
>> PCTUSED integer
>> Specify the minimum percentage of used space that Oracle maintains for
>> each data block of the table, object table OID index, or
>> index-organized table overflow data segment. A block becomes a
>> candidate for row insertion when its used space falls below PCTUSED.
>> PCTUSED is specified as a positive integer from 0 to 99 and defaults  
>> to
>> 40.
>> PCTUSED has the same function in the PARTITION description and in the
>> statements that create and alter clusters, materialized views, and
>> materialized view logs.
>> PCTUSED is not a valid table storage characteristic for an
>> index-organized table (ORGANIZATION INDEX).
>> The sum of PCTFREE and PCTUSED must be equal to or less than 100. You
>> can use PCTFREE and PCTUSED together to utilize space within a table
>> more efficiently.
>>
>> PostgreSQL could take some hints from the above.
>>
>> On Aug 27, 2004, at 1:26 AM, Gaetano Mendola wrote:
>>
>>> Greg Stark wrote:
>>>
>>>> The discussions before talked about a mechanism to try to place new
>>>> tuples as close as possible to the proper index position.
>>>
>>> Means this that an index shall have a "fill factor" property, similar
>>> to
>>> Informix one ?
>>>
>>> From the manual:
>>>
>>>
>>> The FILLFACTOR option takes effect only when you build an index on a
>>> table
>>> that contains more than 5,000 rows and uses more than 100 table  
>>> pages,
>>> when
>>> you create an index on a fragmented table, or when you create a
>>> fragmented
>>> index on a nonfragmented table.
>>> Use the FILLFACTOR option to provide for expansion of an index at a
>>> later
>>> date or to create compacted indexes.
>>> When the index is created, the database server initially fills only
>>> that
>>> percentage of the nodes specified with the FILLFACTOR value.
>>>
>>> # Providing a Low Percentage Value
>>> If you provide a low percentage value, such as 50, you allow room for
>>> growth
>>> in your index. The nodes of the index initially fill to a certain
>>> percentage and
>>> contain space for inserts. The amount of available space depends on  
>>> the
>>> number of keys in each page as well as the percentage value.
>>> For example, with a 50-percent FILLFACTOR value, the page would be  
>>> half
>>> full and could accommodate doubling in size. A low percentage value  
>>> can
>>> result in faster inserts and can be used for indexes that you expect
>>> to grow.
>>>
>>>
>>> # Providing a High Percentage Value
>>> If you provide a high percentage value, such as 99, your indexes are
>>> compacted, and any new index inserts result in splitting nodes. The
>>> maximum density is achieved with 100 percent. With a 100-percent
>>> FILLFACTOR value, the index has no room available for growth; any
>>> additions to the index result in splitting the nodes.
>>> A 99-percent FILLFACTOR value allows room for at least one insertion
>>> per
>>> node. A high percentage value can result in faster selects and can be
>>> used for
>>> indexes that you do not expect to grow or for mostly read-only  
>>> indexes.
>>>
>>>
>>>
>>>
>>> Regards
>>> Gaetano Mendola
>>>
>>>
>>>
>>>
>>>
>>> ---------------------------(end of
>>> broadcast)---------------------------
>>> TIP 7: don't forget to increase your free space map settings
>>>
>>>
>> --
>> Adi Alurkar (DBA sf.NET) 
>> 1024D/79730470 A491 5724 74DE 956D 06CB  D844 6DF1 B972 7973 0470
>>
>>
>>
>> ---------------------------(end of  
>> broadcast)---------------------------
>> TIP 6: Have you searched our list archives?
>>
>>                http://archives.postgresql.org
>>
>
> -- 
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman@candle.pha.pa.us               |  (610) 359-1001
>   +  If your life is a hard drive,     |  13 Roberts Road
>   +  Christ can be your backup.        |  Newtown Square, Pennsylvania  
> 19073
>
> ---------------------------(end of  
> broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if  
> your
>       joining column's datatypes do not match
>
>
--
Adi Alurkar (DBA sf.NET) 
1024D/79730470 A491 5724 74DE 956D 06CB  D844 6DF1 B972 7973 0470



From pgsql-performance-owner@postgresql.org  Fri Aug 27 14:49:36 2004
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From: Bruce Momjian 
Message-Id: <200408271748.i7RHmfJ15766@candle.pha.pa.us>
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
In-Reply-To: <118B3D82-F850-11D8-8B8C-000A95C4BD7A@sf.net>
To: Adi Alurkar 
Date: Fri, 27 Aug 2004 13:48:41 -0400 (EDT)
Cc: pgsql-performance@postgresql.org
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Adi Alurkar wrote:
> IIRC it it to reduce the "overflow" of data or what oracle calls  
> chained rows. i.e if a table has variable length columns and 10 rows  
> get inserted into a datapage, if this datapage is full and one of the  
> variable length field gets updated the row will now "overflow" into  
> another datapage, but if the datapage is created with an appropriate  
> amount of free space the updated row will be stored in one single  
> datapage.

Agreed.  What I am wondering is with our system where every update gets
a new row, how would this help us?  I know we try to keep an update on
the same row as the original, but is there any significant performance
benefit to doing that which would offset the compaction advantage?

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

From pgsql-performance-owner@postgresql.org  Fri Aug 27 15:19:38 2004
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To: Bruce Momjian 
Cc: Adi Alurkar , pgsql-performance@postgresql.org
Subject: Re: Equivalent praxis to CLUSTERED INDEX? 
In-reply-to: <200408271748.i7RHmfJ15766@candle.pha.pa.us> 
References: <200408271748.i7RHmfJ15766@candle.pha.pa.us>
Comments: In-reply-to Bruce Momjian 
	message dated "Fri, 27 Aug 2004 13:48:41 -0400"
Date: Fri, 27 Aug 2004 14:19:29 -0400
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From: Tom Lane 
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Bruce Momjian  writes:
> Agreed.  What I am wondering is with our system where every update gets
> a new row, how would this help us?  I know we try to keep an update on
> the same row as the original, but is there any significant performance
> benefit to doing that which would offset the compaction advantage?

Because Oracle uses overwrite-in-place (undoing from an UNDO log on
transaction abort), while we always write a whole new row, it would take
much larger PCTFREE wastage to get a useful benefit in PG than it does
in Oracle.  That wastage translates directly into increased I/O costs,
so I'm a bit dubious that we should assume there is a win to be had here
just because Oracle offers the feature.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Sun Aug 29 12:15:33 2004
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From: Mischa Sandberg 
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
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	<200408271748.i7RHmfJ15766@candle.pha.pa.us>
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I think you've probably fingered the kicker of why PG doesn't have this 
kind of clustering already. Hence perhaps the need for other approaches
to the issue (the disk-IO efficiency of reading groups of rows related 
by a common key) that other DB's (with in-place update) address with
synchronous clustering ('heap rebalancing' ?).

Bruce Momjian wrote:
> Adi Alurkar wrote:
> 
>>IIRC it it to reduce the "overflow" of data or what oracle calls  
>>chained rows. i.e if a table has variable length columns and 10 rows  
>>get inserted into a datapage, if this datapage is full and one of the  
>>variable length field gets updated the row will now "overflow" into  
>>another datapage, but if the datapage is created with an appropriate  
>>amount of free space the updated row will be stored in one single  
>>datapage.
> 
> 
> Agreed.  What I am wondering is with our system where every update gets
> a new row, how would this help us?  I know we try to keep an update on
> the same row as the original, but is there any significant performance
> benefit to doing that which would offset the compaction advantage?
> 

From pgsql-performance-owner@postgresql.org  Fri Aug 27 16:29:27 2004
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	Fri, 27 Aug 2004 12:29:11 PDT
Date: Fri, 27 Aug 2004 12:29:11 -0700 (PDT)
From: Artimenko Igor 
Subject: Why those queries do not utilize indexes?
To: pgsql-performance@postgresql.org
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Hi everybody!

Here is my queries:

1. explain SELECT * FROM messageinfo WHERE user_id = CAST( 20000 AS BIGINT ) and msgstatus = CAST(
0 AS smallint );

2. explain SELECT * FROM messageinfo WHERE messageinfo.user_id = 20000::int8 and msgstatus =
0::smallint;

In both cases Explain command shows:
1. Sequential search and very high cost if set enable_seqscan to on;
Seq scan on messageinfo ( cost=0.00..24371.30, rows =36802 )

2. Index scan but even bigger cost if set enable_seqscan to off;
Index �messagesStatus� on messageinfo ( Cost=0.00..27220.72, rows=36802 )

messageinfo table has 200 records which meet this criteria and 662420 in total:

CREATE TABLE messageinfo
(
  user_id int8 NOT NULL,
  msgstatus int2 NOT NULL DEFAULT (0)::smallint,
  receivedtime timestamp NOT NULL DEFAULT now(),
  �
  msgread bool DEFAULT false,
  �
  CONSTRAINT "$1" FOREIGN KEY (user_id) REFERENCES users (id) ON UPDATE CASCADE ON DELETE CASCADE,
  ) 
WITH OIDS;

CREATE INDEX msgstatus
  ON messageinfo
  USING btree
  (user_id, msgstatus);

CREATE INDEX "messagesStatus"
  ON messageinfo
  USING btree
  (msgstatus);

CREATE INDEX msgread
  ON messageinfo
  USING btree
  (user_id, msgread);

CREATE INDEX "receivedTime"
  ON messageinfo
  USING btree
  (receivedtime);


MY QUESTIONS ARE:

1.	Should I afraid of high cost indexes? Or query will still be very efficient?

2.	Postgres does not use the index I need. For my data sets it�s always msgstatus index is
narrowest compare with �messagesStatus� one. Is any way to �enforce� to use a particular index?
What�s the logic when Postgres chooses one index compare with the other.

3.	I can change db structure to utilize Postgres specifics if you can tell them to me.

4.	Also, originally I had �messagesStatus� index having 2 components ( �msgstatus�, �user_id� ).
But query SELECT * FROM messageinfo WHERE msgstatus = 0 did not utilize indexes in this case. It
only worked if both index components are in WHERE part. So I have to remove 2-nd component
�user_id� from messagesStatus index even I wanted it. Is any way that where clause has only 1-st
component but index is utilized? 

Igor Artimenko


		
__________________________________
Do you Yahoo!?
Yahoo! Mail Address AutoComplete - You start. We finish.
http://promotions.yahoo.com/new_mail 

From pgsql-performance-owner@postgresql.org  Fri Aug 27 16:31:37 2004
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To: Bruce Momjian 
Cc: Adi Alurkar , pgsql-performance@postgresql.org
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
References: <200408271748.i7RHmfJ15766@candle.pha.pa.us>
In-Reply-To: <200408271748.i7RHmfJ15766@candle.pha.pa.us>
From: Greg Stark 
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Bruce Momjian  writes:

> Agreed.  What I am wondering is with our system where every update gets
> a new row, how would this help us?  I know we try to keep an update on
> the same row as the original, but is there any significant performance
> benefit to doing that which would offset the compaction advantage?

Hm. Posit a system where all transactions are short updates executed in
autocommit mode. 

In such a system as soon as a transaction commits it would take a very short
time before the previous record was a dead tuple.

If every backend kept a small list of tuples it had marked deleted and
whenever it was idle checked to see if they were dead yet, it might avoid much
of the need for vacuum. And in such a circumstance I think you wouldn't need
more than a pctfree of 50% even on a busy table. Every tuple would need about
one extra slot.

This would only be a reasonable idea if a) if the list of potential dead
tuples is short and if it overflows it just forgets them leaving them for
vacuum to deal with. and b) It only checks the potentially dead tuples when
the backend is otherwise idle.

Even so it would be less efficient than a batch vacuum, and it would be taking
up i/o bandwidth (to maintain indexes even if the heap buffer is in ram), even
if that backend is idle it doesn't mean other backends couldn't have used that
i/o bandwidth.

But I think it would deal with a lot of the complaints about vacuum and it
would make it more feasible to use a pctfree parameter to make clustering more
effective.

-- 
greg


From pgsql-performance-owner@postgresql.org  Fri Aug 27 16:35:03 2004
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To: Bruce Momjian 
Cc: Adi Alurkar , pgsql-performance@postgresql.org
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
References: <200408271748.i7RHmfJ15766@candle.pha.pa.us>
In-Reply-To: <200408271748.i7RHmfJ15766@candle.pha.pa.us>
From: Greg Stark 
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Bruce Momjian  writes:

> but is there any significant performance benefit to doing that which would
> offset the compaction advantage?

Just as a side comment. Setting PCTFREE 0 PCTUSED 100 on tables that have no
updates on them has an astonishingly big effect on speed. So the penalty for
leaving some space free really is substantial.

I think the other poster is right. Oracle really needs pctfree because of the
way it handles updates. Postgres doesn't really need as much because it
doesn't try to squeeze the new tuple in the space the old one took up. If it
doesn't fit on the page the worst that happens is it has to store it on some
other page, whereas oracle has to do its strange row chaining thing.

-- 
greg


From pgsql-performance-owner@postgresql.org  Fri Aug 27 16:43:53 2004
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From: Bruce Momjian 
Message-Id: <200408271942.i7RJgoR03090@candle.pha.pa.us>
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
In-Reply-To: <87acwgml26.fsf@stark.xeocode.com>
To: Greg Stark 
Date: Fri, 27 Aug 2004 15:42:50 -0400 (EDT)
Cc: Adi Alurkar , pgsql-performance@postgresql.org
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Greg Stark wrote:
> 
> Bruce Momjian  writes:
> 
> > but is there any significant performance benefit to doing that which would
> > offset the compaction advantage?
> 
> Just as a side comment. Setting PCTFREE 0 PCTUSED 100 on tables that have no
> updates on them has an astonishingly big effect on speed. So the penalty for
> leaving some space free really is substantial.
> 
> I think the other poster is right. Oracle really needs pctfree because of the
> way it handles updates. Postgres doesn't really need as much because it
> doesn't try to squeeze the new tuple in the space the old one took up. If it
> doesn't fit on the page the worst that happens is it has to store it on some
> other page, whereas oracle has to do its strange row chaining thing.

Oracle also does that chain thing so moving updates to different pages
might have more of an impact than it does on PostgreSQL.  We have chains
too but just for locking.  Not sure on Oracle.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

From pgsql-performance-owner@postgresql.org  Fri Aug 27 16:49:25 2004
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Date: Fri, 27 Aug 2004 21:49:12 +0200 (CEST)
From: Dennis Bjorklund 
To: Artimenko Igor 
Cc: pgsql-performance@postgresql.org
Subject: Re: Why those queries do not utilize indexes?
In-Reply-To: <20040827192911.72205.qmail@web11905.mail.yahoo.com>
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On Fri, 27 Aug 2004, Artimenko Igor wrote:

> 1. Sequential search and very high cost if set enable_seqscan to on;
> Seq scan on messageinfo ( cost=0.00..24371.30, rows =36802 )
> 
> 2. Index scan but even bigger cost if set enable_seqscan to off;
> Index �messagesStatus� on messageinfo ( Cost=0.00..27220.72, rows=36802 )

So pg thinks that a sequential scan will be a little bit faster (The cost 
is a little bit smaller). If you compare the actual runtimes maybe you 
will see that pg was right. In this case the cost is almost the same so 
the runtime is probably almost the same.

When you have more data pg will start to use the index since then it will 
be faster to use an index compared to a seq. scan.

-- 
/Dennis Bj�rklund


From pgsql-performance-owner@postgresql.org  Sun Aug 29 12:15:40 2004
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From: Mischa Sandberg 
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
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This discussion is starting to sound like the split in HEAP memory 
management evolution, into garbage-collecting (e.g. Java) and 
non-garbage-collecting (e.g. C++).

Reclamation by GC's these days has become seriously sophisticated.
CLUSTER resembles the first generation of GC's, which were 
single-big-pass hold-everything-else threads.

Perhaps the latest in incremental GC algorithms would be worth scouting, 
for the next step in PG page management.

Greg Stark wrote:

> Bruce Momjian  writes:
> 
>>but is there any significant performance benefit to doing that which would
>>offset the compaction advantage?
> 
> Just as a side comment. Setting PCTFREE 0 PCTUSED 100 on tables that have no
> updates on them has an astonishingly big effect on speed. So the penalty for
> leaving some space free really is substantial.
> 
> I think the other poster is right. Oracle really needs pctfree because of the
> way it handles updates. Postgres doesn't really need as much because it
> doesn't try to squeeze the new tuple in the space the old one took up. If it
> doesn't fit on the page the worst that happens is it has to store it on some
> other page, whereas oracle has to do its strange row chaining thing.

From pgsql-performance-owner@postgresql.org  Fri Aug 27 17:34:37 2004
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>>>>> "JB" == Josh Berkus  writes:

JB> Guys,
>> the XServe/XRaid comes with FibreChannel

JB> I stand corrected.  That should help things some; it makes it more
JB> of a small tradeoff between performance and storage size for the
JB> drives.


it is fibre channel to the host.  the internals are still IDE drives
with possibly multiple controllers inside the enclosure.

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Vivek Khera, Ph.D.                Khera Communications, Inc.
Internet: khera@kciLink.com       Rockville, MD  +1-301-869-4449 x806
AIM: vivekkhera Y!: vivek_khera   http://www.khera.org/~vivek/

From pgsql-performance-owner@postgresql.org  Fri Aug 27 18:09:04 2004
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	Fri, 27 Aug 2004 14:08:58 PDT
Date: Fri, 27 Aug 2004 14:08:58 -0700 (PDT)
From: Artimenko Igor 
Subject: Re: Why those queries do not utilize indexes?
To: Dennis Bjorklund 
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I could force Postgres to use the best index by removing condition "msgstatus = CAST( 0 AS
smallint );" from WHERE clause & set enable_seqscan to off;
Total runtime in this case dropped from 1883 ms ( sequential reads ) to 1.598 ms ( best index ).

But unfortunatelly It does not resolve my problem. I can not remove above condition. I need to
find a way to use whole condition "WHERE user_id = CAST( 20000 AS BIGINT ) and msgstatus = CAST( 0
AS smallint );" and still utilyze index.  

Yes you are right. Using "messagesStatus" index is even worse for my data set then sequential
scan.

Igor Artimenko

--- Dennis Bjorklund  wrote:

> On Fri, 27 Aug 2004, Artimenko Igor wrote:
> 
> > 1. Sequential search and very high cost if set enable_seqscan to on;
> > Seq scan on messageinfo ( cost=0.00..24371.30, rows =36802 )
> > 
> > 2. Index scan but even bigger cost if set enable_seqscan to off;
> > Index �messagesStatus� on messageinfo ( Cost=0.00..27220.72, rows=36802 )
> 
> So pg thinks that a sequential scan will be a little bit faster (The cost 
> is a little bit smaller). If you compare the actual runtimes maybe you 
> will see that pg was right. In this case the cost is almost the same so 
> the runtime is probably almost the same.
> 
> When you have more data pg will start to use the index since then it will 
> be faster to use an index compared to a seq. scan.
> 
> -- 
> /Dennis Bj�rklund
> 
> 



		
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From: Gaetano Mendola 
X-Newsgroups: comp.databases.postgresql.performance
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
Date: Sat, 28 Aug 2004 03:02:47 +0200
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Tom Lane wrote:

 > Bruce Momjian  writes:
 >
 >>Agreed.  What I am wondering is with our system where every update gets
 >>a new row, how would this help us?  I know we try to keep an update on
 >>the same row as the original, but is there any significant performance
 >>benefit to doing that which would offset the compaction advantage?
 >
 >
 > Because Oracle uses overwrite-in-place (undoing from an UNDO log on
 > transaction abort), while we always write a whole new row, it would take
 > much larger PCTFREE wastage to get a useful benefit in PG than it does
 > in Oracle.  That wastage translates directly into increased I/O costs,
 > so I'm a bit dubious that we should assume there is a win to be had here
 > just because Oracle offers the feature.

Mmmm. Consider this scenario:

ctid           datas
(0,1)   yyy-xxxxxxxxxxxxxxxxxxx
(0,2)   -------- EMPTY --------
(0,3)   -------- EMPTY --------
(0,4)   -------- EMPTY --------
(0,5)   -------- EMPTY --------
(0,6)   yyy-xxxxxxxxxxxxxxxxxxx
(0,7)   -------- EMPTY --------
....    -------- EMPTY --------
(0,11)  yyy-xxxxxxxxxxxxxxxxxxx


the row (0,2) --> (0,5) are space available for the (0,1) updates.
This will help a table clustered ( for example ) to mantain his
own correct cluster order.



Regards
Gaetano Mendola













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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Bruce Momjian wrote:

| Gaetano Mendola wrote:
|
|>Tom Lane wrote:
|>
|> > Bruce Momjian  writes:
|> >
|> >>Agreed.  What I am wondering is with our system where every update gets
|> >>a new row, how would this help us?  I know we try to keep an update on
|> >>the same row as the original, but is there any significant performance
|> >>benefit to doing that which would offset the compaction advantage?
|> >
|> >
|> > Because Oracle uses overwrite-in-place (undoing from an UNDO log on
|> > transaction abort), while we always write a whole new row, it would take
|> > much larger PCTFREE wastage to get a useful benefit in PG than it does
|> > in Oracle.  That wastage translates directly into increased I/O costs,
|> > so I'm a bit dubious that we should assume there is a win to be had here
|> > just because Oracle offers the feature.
|>
|>Mmmm. Consider this scenario:
|>
|>ctid           datas
|>(0,1)   yyy-xxxxxxxxxxxxxxxxxxx
|>(0,2)   -------- EMPTY --------
|>(0,3)   -------- EMPTY --------
|>(0,4)   -------- EMPTY --------
|>(0,5)   -------- EMPTY --------
|>(0,6)   yyy-xxxxxxxxxxxxxxxxxxx
|>(0,7)   -------- EMPTY --------
|>....    -------- EMPTY --------
|>(0,11)  yyy-xxxxxxxxxxxxxxxxxxx
|>
|>
|>the row (0,2) --> (0,5) are space available for the (0,1) updates.
|>This will help a table clustered ( for example ) to mantain his
|>own correct cluster order.
|
|
| Right.  My point was that non-full fill is valuable for us only when
| doing clustering, while for Oracle it is a win even in non-cluster cases
| because of the way they update in place.

Don't you think this will permit also to avoid extra disk seek and cache
invalidation? If you are updating the row (0,1) I think is less expensive
put the new version in (0,2) instead of thousand line far from that point.


Regards
Gaetano Mendola





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From pgsql-performance-owner@postgresql.org  Sat Aug 28 00:55:01 2004
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From: Bruce Momjian 
Message-Id: <200408280354.i7S3slb21543@candle.pha.pa.us>
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
In-Reply-To: <412FE901.3070707@bigfoot.com>
To: Gaetano Mendola 
Date: Fri, 27 Aug 2004 23:54:47 -0400 (EDT)
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	"pgsql-performance@postgresql.org" 
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Gaetano Mendola wrote:
> | Right.  My point was that non-full fill is valuable for us only when
> | doing clustering, while for Oracle it is a win even in non-cluster cases
> | because of the way they update in place.
> 
> Don't you think this will permit also to avoid extra disk seek and cache
> invalidation? If you are updating the row (0,1) I think is less expensive
> put the new version in (0,2) instead of thousand line far from that point.

It would, but does that outweigh the decreased I/O by having things more
densely packed?  I would think not.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

From pgsql-performance-owner@postgresql.org  Sat Aug 28 05:15:29 2004
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Subject: Re: Equivalent praxis to CLUSTERED INDEX?
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Bruce Momjian  writes:

> > Don't you think this will permit also to avoid extra disk seek and cache
> > invalidation? If you are updating the row (0,1) I think is less expensive
> > put the new version in (0,2) instead of thousand line far from that point.

Well if the other buffer "a thousand lines far from that point" is already in
ram, then no, there's no penalty at the time for storing it there.

However it destroys the clustering, which was the original point.

> It would, but does that outweigh the decreased I/O by having things more
> densely packed?  I would think not.

Well the dense packing is worth something. But so is the clustering. There's
definitely a trade-off.

I always found my largest tables are almost always insert-only tables anyways.
So in Oracle I would have pctused 100 pctfree 0 on them and get the
performance gain.

The tables that would benefit from this would be tables always accessed by
indexes in index scans of more than one record. The better the clustering the
fewer pages the index scan would have to read in. If the data took 10% more
space but the index scan only needs 1/4 as many buffers it could be a big net
win.

-- 
greg


From pgsql-performance-owner@postgresql.org  Sat Aug 28 05:51:02 2004
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First things first:  try vacuum full analyze on all the tables involved.

> 1.	Should I afraid of high cost indexes? Or query will still be very efficient?

Not necessarily.  However, EXPLAIN output is pretty much useless for us 
for helping you.  You need to post EXPLAIN ANALYZE output.

Then, you need to use explain analyze to check the speed difference 
between the index and seq scan versions.  Is the seq scan actually slower?

> 2.	Postgres does not use the index I need. For my data sets it�s always msgstatus index is
> narrowest compare with �messagesStatus� one. Is any way to �enforce� to use a particular index?
> What�s the logic when Postgres chooses one index compare with the other.

It's complicated, but it's based on teh statistics in pg_statistic that 
the vacuum analyze command gathers.

> 3.	I can change db structure to utilize Postgres specifics if you can tell them to me.

I avoid using int8 and int2 in the first place :)  In PostgreSQL 8.0, 
they will be less troublesome, but I've never seen a need for them!

> 4.	Also, originally I had �messagesStatus� index having 2 components ( �msgstatus�, �user_id� ).
> But query SELECT * FROM messageinfo WHERE msgstatus = 0 did not utilize indexes in this case. It
> only worked if both index components are in WHERE part. So I have to remove 2-nd component
> �user_id� from messagesStatus index even I wanted it. Is any way that where clause has only 1-st
> component but index is utilized? 

So long as your where clause matches a subset of the columns in the 
index in left to right order, the index can be used.  For example, if 
your index is over (a, b, c) then select * where a=1 and b=2; can use 
the index.

Chris


From pgsql-performance-owner@postgresql.org  Sat Aug 28 08:15:07 2004
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Hi all,
do you know any clean workaround at ill-planned queries inside a stored procedure?
Let me explain with an example:


empdb=# select count(*) from user_logs;
   count
---------
  5223837
(1 row)

empdb=# select count(*) from user_logs where id_user = 5024;
  count
--------
  239453
(1 row)

empdb=# explain analyze select login_time from user_logs where id_user = 5024 order by id_user_log desc limit 1;
                                                                      QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------
  Limit  (cost=0.00..22.62 rows=1 width=12) (actual time=3.921..3.922 rows=1 loops=1)
    ->  Index Scan Backward using user_logs_pkey on user_logs  (cost=0.00..5355619.65 rows=236790 width=12) (actual time=3.918..3.918 rows=1 loops=1)
          Filter: (id_user = 5024)
  Total runtime: 3.963 ms
(4 rows)


same select in a prepared query ( I guess the stored procedure use same plan ):

empdb=# explain analyze execute test(5024);
                                                                        QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------------------
  Limit  (cost=759.60..759.61 rows=1 width=12) (actual time=45065.755..45065.756 rows=1 loops=1)
    ->  Sort  (cost=759.60..760.78 rows=470 width=12) (actual time=45065.748..45065.748 rows=1 loops=1)
          Sort Key: id_user_log
          ->  Index Scan using idx_user_user_logs on user_logs  (cost=0.00..738.75 rows=470 width=12) (actual time=8.936..44268.087 rows=239453 loops=1)
                Index Cond: (id_user = $1)
  Total runtime: 45127.256 ms
(6 rows)


There is a way to say: replan this query at execution time ?


Regards
Gaetano Mendola






From pgsql-performance-owner@postgresql.org  Sat Aug 28 09:02:17 2004
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From: Gaetano Mendola 
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Greg Stark wrote:

> Bruce Momjian  writes:
> 
> 
>>>Don't you think this will permit also to avoid extra disk seek and cache
>>>invalidation? If you are updating the row (0,1) I think is less expensive
>>>put the new version in (0,2) instead of thousand line far from that point.
> 
> 
> Well if the other buffer "a thousand lines far from that point" is already in
> ram, then no, there's no penalty at the time for storing it there.

I was wandering about the cache invalidation, may be the ram is big enough but I
doubt about the cache, the recommendation in this case is to modify adjacent
memory address instead of jumping.


Regards
Gaetano Mendola



From pgsql-performance-owner@postgresql.org  Sat Aug 28 12:13:46 2004
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From: andrew@pillette.com
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Subject: Re: ill-planned queries inside a stored procedure
To: Gaetano Mendola 
Cc: "pgsql-performance@postgresql.org" 
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I use "EXECUTE" inside a stored procedure for just this purpose. This is not the same as PREPARE/EXECUTE, it lets you send an arbitrary string as SQL within the procedure. You have to write the query text on the fly in the procedure, which can be a little messy with quoting and escaping.

Gaetano Mendola  wrote ..
> Hi all,
> do you know any clean workaround at ill-planned queries inside a stored
> procedure?

From pgsql-performance-owner@postgresql.org  Sat Aug 28 13:35:31 2004
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

andrew@pillette.com wrote:

| Gaetano Mendola  wrote ..
|
|>Hi all,
|>do you know any clean workaround at ill-planned queries inside a stored
|>procedure?
| I use "EXECUTE" inside a stored procedure for just this purpose. This is
| not the same as PREPARE/EXECUTE, it lets you send an arbitrary string as
| SQL within the procedure. You have to write the query text on the fly in
| the procedure, which can be a little messy with quoting and escaping.
|

Yes I knew, I wrote "clean workaround" :-)

I hate write in function piece of code like this:

~   [...]

~   my_stm := ''SELECT '' || my_operation || ''( '' || a_id_transaction;
~   my_stm := my_stm || '', '' || a_id_contract;
~   my_stm := my_stm || '', '' || quote_literal(a_date) || '') AS res'';

~   FOR my_record IN EXECUTE my_stm LOOP
~      IF my_record.res < 0 THEN
~         RETURN my_record.res;
~      END IF;

~      EXIT;
~   END LOOP;

~   [...]

note also that useless loop that is needed to retrieve the value!



Regards
Gaetano Mendola












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From pgsql-performance-owner@postgresql.org  Sat Aug 28 14:42:03 2004
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Date: Sat, 28 Aug 2004 20:41:51 +0300
From: Vitaly Belman 
Reply-To: Vitaly Belman 
To: Postgresql Performance 
Subject: Performance hit on loading from HD
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I have a problem with certain queries performance. Trouble is that
while their execution plan is pretty good and mostly their execution
is great as well, their FIRST execution time (that is after you mount
the database) is abysmal.

I realize that it happens due to the loading of data from the HD to
the memory/swap and it wouldn't be too bad if I just could make the
data stay in the memory, sadly, after a few minutes the data is back
on the HD and running the query again results the same bad
performance.

Here's a query for example, though as I said, this problem occurs in
different queries.

---------------------------------------------------------------------------------------

  SELECT *
    FROM bv_bookgenres, bv_books
   WHERE bv_books.book_id = bv_bookgenres.book_id and genre_id = 987 
ORDER BY vote_avg limit 10

---------------------------------------------------------------------------------------

---------------------------------------------------------------------------------------

QUERY PLAN
Limit  (cost=2601.16..2601.18 rows=10 width=193) (actual
time=4735.097..4735.107 rows=10 loops=1)
  ->  Sort  (cost=2601.16..2601.70 rows=219 width=193) (actual
time=4735.092..4735.095 rows=10 loops=1)
        Sort Key: bv_books.vote_avg
        ->  Nested Loop  (cost=0.00..2592.64 rows=219 width=193)
(actual time=74.615..4719.147 rows=1877 loops=1)
              ->  Index Scan using i_bookgenres_genre_id on
bv_bookgenres  (cost=0.00..1707.03 rows=218 width=4) (actual
time=74.540..2865.366 rows=1877 loops=1)
                    Index Cond: (genre_id = 987)
              ->  Index Scan using bv_books_pkey on bv_books 
(cost=0.00..4.05 rows=1 width=193) (actual time=0.968..0.971 rows=1
loops=1877)
                    Index Cond: (bv_books.book_id = "outer".book_id)
Total runtime: 4735.726 ms

---------------------------------------------------------------------------------------

If I run the query again after it just finished running I would get
the following timing:

---------------------------------------------------------------------------------------

Limit  (cost=3937.82..3937.84 rows=10 width=204)
  ->  Sort  (cost=3937.82..3938.38 rows=223 width=204)
        Sort Key: bv_books.vote_avg
        ->  Nested Loop  (cost=0.00..3929.12 rows=223 width=204)
              ->  Index Scan using i_bookgenres_genre_id on
bv_bookgenres  (cost=0.00..1731.94 rows=222 width=8)
                    Index Cond: (genre_id = 987)
              ->  Index Scan using bv_books_pkey on bv_books 
(cost=0.00..9.88 rows=1 width=196)
                    Index Cond: (bv_books.book_id = "outer".book_id)

---------------------------------------------------------------------------------------

Before going on, I should say that I am running PostgreSQL on CoLinux
under Windows 2000. From what I read/tested, the CoLinux performance
on CoLinux are matching to the performance of VMWare. Yet, I'm still
wondering if it is a side effect of my development setup or if some of
my settings are indeed wrong.

With that said, here is the information of the tables:

---------------------------------------------------------------------------------------

CREATE TABLE bv_books
(
  book_id serial NOT NULL,
  book_name varchar(255) NOT NULL,
  series_id int4,
  series_index int2,
  annotation_desc_id int4,
  description_desc_id int4,
  book_picture varchar(255) NOT NULL,
  reviews_error int4 NOT NULL,
  vote_avg float4 NOT NULL,
  vote_count int4 NOT NULL,
  book_genre int4[],
  book_name_fulltext tsearch2.tsvector,
  book_name_fulltext2 tsearch2.tsvector,
  CONSTRAINT bv_books_pkey PRIMARY KEY (book_id),
  CONSTRAINT fk_books_annotation_desc_id FOREIGN KEY
(annotation_desc_id) REFERENCES bv_descriptions (description_id) ON
UPDATE RESTRICT ON DELETE SET NULL,
  CONSTRAINT fk_books_description_desc_id FOREIGN KEY
(description_desc_id) REFERENCES bv_descriptions (description_id) ON
UPDATE RESTRICT ON DELETE SET NULL,
  CONSTRAINT fk_books_series_id FOREIGN KEY (series_id) REFERENCES
bv_series (series_id) ON UPDATE RESTRICT ON DELETE RESTRICT
) 
WITH OIDS;

CREATE TABLE bv_bookgenres
(
  book_id int4 NOT NULL,
  genre_id int4 NOT NULL,
  CONSTRAINT bv_bookgenres_pkey PRIMARY KEY (book_id, genre_id),
  CONSTRAINT fk_bookgenres_book_id FOREIGN KEY (book_id) REFERENCES
bv_books (book_id) ON UPDATE RESTRICT ON DELETE CASCADE,
  CONSTRAINT fk_bookgenres_genre_id FOREIGN KEY (genre_id) REFERENCES
bv_genres (genre_id) ON UPDATE RESTRICT ON DELETE RESTRICT
) 
WITH OIDS;

---------------------------------------------------------------------------------------

As far as the data is concerned, there are around 170,000 rows in
bv_books and 940,000 in bv_bookgenres. There are also btree index on
all the relevant (to the query) fields.

I can live up with the fact that the data has to be loaded the first
time it is accessed, but is it possible to make it stick longer in the
memory? Is it the fact that CoLinux gets only 128MB of RAM? Or one of
my settings should be fixed?

Thanks

From pgsql-performance-owner@postgresql.org  Sat Aug 28 18:33:54 2004
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From: Josh Berkus 
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Organization: Aglio Database Solutions
To: Vitaly Belman 
Subject: Re: Performance hit on loading from HD
Date: Sat, 28 Aug 2004 14:34:23 -0700
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Vitaly,

> I have a problem with certain queries performance. Trouble is that
> while their execution plan is pretty good and mostly their execution
> is great as well, their FIRST execution time (that is after you mount
> the database) is abysmal.

This is a well-known problem.   The general approach to this is to run a 
script to do select * queries against all important tables on system 
start-up.

> I realize that it happens due to the loading of data from the HD to
> the memory/swap and it wouldn't be too bad if I just could make the
> data stay in the memory, sadly, after a few minutes the data is back
> on the HD and running the query again results the same bad
> performance.

This could be for a variety of reasons.  On a standard platform (which yours 
most definitely is not), this would be due to database vacuuming, commits of 
large updates to your data, or another application using most of the system 
memory.

> Before going on, I should say that I am running PostgreSQL on CoLinux
> under Windows 2000. From what I read/tested, the CoLinux performance
> on CoLinux are matching to the performance of VMWare. Yet, I'm still
> wondering if it is a side effect of my development setup or if some of
> my settings are indeed wrong.

Probably you will continue to get worse-than-normal performance from both.   
You simply can't expect performance PostgreSQL running on an emulation 
environment.   If you could, we wouldn't have bothered with a Windows port.  
Speaking of which, have you started testing the Windows port?  I'd be 
interested in your comparison of it against running on CoLinux.

> I can live up with the fact that the data has to be loaded the first
> time it is accessed, but is it possible to make it stick longer in the
> memory? Is it the fact that CoLinux gets only 128MB of RAM? Or one of
> my settings should be fixed?

Well, mostly it's that you should start testing 8.0, and the Windows port.  
Not only should running native be better, but 8.0 (thanks to the work of Jan 
Wieck) is now able to take advantage of a large chunk of dedicated memory, 
which earlier versions were not.   Also, "lazy vacuum" and the "background 
writer", also features of 8.0 and Jan's work, should prevent PostgreSQL from 
cleaning out its own cache completely.    You should test this, 
*particularly* on Windows where we could use some more performance testing.

-- 
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Sun Aug 29 15:05:05 2004
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Date: Sun, 29 Aug 2004 11:04:48 -0700 (PDT)
From: Mr Pink 
Subject: Re: Why does a simple query not use an obvious index?
To: Jack Kerkhof 
Cc: pgsql-performance@postgresql.org
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Strangely enough, I don't find that result surprising.

if the vast bulk of the data is in the past and now()-60 represents a very small slice of the data
we might expect that using an index is optimal, but there could be many reasons why it doesn't get
used. 

AFAIK postgres doesn't peek at values used in a query when optimizing so any query with a ">" type
condition is gonna have a seq scan as the plan since the best guess is that you are gonna match
50% of the table. That's one possible explanation.

Another is that if the condition data types don't match then an indes won't be used you could try:

  select count(*) from billing where timestamp > (now()-60)::timestamp

Might make a difference, I dunno, it's a case of testing amd seing what happens.

You could try lowering the random page cost, it might help, but I don't like your chances.

If your problem is that you want to access the most recent data from a large table with fast
response, then you could consider:

1. a "recent" index. If the data is within the "recent" time from set a flag to true, other wise
null. Reset the flags periodically. Nulls aren't indexed so the selectivity of such an index is
much higher. Can work wonders.

2, duplicate recent data in another table that is purged when data passes the age limit. This is
basic archiving.

Something like that. Hopefully someone with more knowlege of the optimaizer will have a brighter
suggestion for you. 

What version are you using by the way?
 
Regards
Mr Pink
 
--- Jack Kerkhof  wrote:

> The query:
>     select count(*) from billing where timestamp > now()-60
> 
> should obviously use the index
> 
>     CREATE INDEX billing_timestamp_idx ON billing USING btree ("timestamp"
> timestamp_ops);
> 
> on a table with 1400000 rows.
> 
> But it uses a Seq Scan. If I set enable_seqscan=no, it indicates a queryplan
> could not be calculated.
> 
> Why does this simple query not use the timestamp index, and how can I get it
> to?
> 
> Thanks, Jack
> 
>      Jack Kerkhof
>       Research & Development
>       jack.kerkhof@guest-tek.com
>       www.guest-tek.com
>       1.866.509.1010 3480
> 
> --------------------------------------------------------------------------
> 
>       Guest-Tek is a leading provider of broadband technology solutions for
> the hospitality industry. Guest-Tek's GlobalSuite�Ehigh-speed Internet
> solution enables hotels to offer their guests the convenience of wired
> and/or wireless broadband Internet access from guest rooms, meeting rooms
> and public areas.
> 
> 
> 



		
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From pgsql-performance-owner@postgresql.org  Sun Aug 29 15:27:22 2004
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Date: Sun, 29 Aug 2004 12:28:48 -0600
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From: "Scott Marlowe" 
To: "Jack Kerkhof" 
Cc: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
In-Reply-To: 
References: 
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On Fri, 2004-08-27 at 11:12, Jack Kerkhof wrote:
> The query:
> 
>     select count(*) from billing where timestamp > now()-60
> 
> should obviously use the index 
> 
>     CREATE INDEX billing_timestamp_idx ON billing USING btree
> ("timestamp" timestamp_ops);
> 
> on a table with 1400000 rows.
> 
> But it uses a Seq Scan. If I set enable_seqscan=no, it indicates a
> queryplan could not be calculated. 

Have you tried this:

marlowe=> select now()-60;
ERROR:  operator does not exist: timestamp with time zone - integer
HINT:  No operator matches the given name and argument type(s). You may
need to add explicit type casts.

you likely need:

smarlowe=> select now()-'60 seconds'::interval;
           ?column?
-------------------------------
 2004-08-29 12:25:38.249564-06

inside there.  

Also, count(*) is likely to always generate a seq scan due to the way
aggregates are implemented currently in pgsql.  you might want to try:

select somefield from sometable where timestampfield > now()-'60
seconds'::interval

and count the number of returned rows.  If there's a lot, it won't be
any faster, if there's a few, it should be a win.


From pgsql-performance-owner@postgresql.org  Sun Aug 29 15:57:54 2004
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Date: Sun, 29 Aug 2004 20:57:50 +0200
From: "Steinar H. Gunderson" 
To: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
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On Sun, Aug 29, 2004 at 11:04:48AM -0700, Mr Pink wrote:
> Another is that if the condition data types don't match then an indes won't be used you could try:
> 
>   select count(*) from billing where timestamp > (now()-60)::timestamp

In fact, I've had success with code like

    select count(*) from billing where timestamp > ( select now() - interval '1 minute' )

At least in my case (PostgreSQL 7.2, though), it made PostgreSQL magically do
an index scan. :-)

/* Steinar */
-- 
Homepage: http://www.sesse.net/

From pgsql-performance-owner@postgresql.org  Sun Aug 29 15:58:24 2004
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From: Josh Berkus 
Reply-To: josh@agliodbs.com
Organization: Aglio Database Solutions
To: ischamay.andbergsay@activestateway.com
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
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Mishca,

> Ummm ... not quite. In MSSQL/Sybase/Oracle, a clustered index maintains
> its space saturation as part of each update operation. High activity
> does indeed result in less-full pages (typically 60-80% full for tables
> with heavy deletions or rowsize changes). To bring the percentage back
> up, you run DBCC INDEXDEFRAG, which also does what you'd expect of a
> normal file defragmenter -- put related disk pages together on the platter.

Sure, it does now, which is a nice thing.  It didn't in the first version 
(6.5) where this cluster maint needed to be done manually and asynchronously, 
as I recall.   

> As for SQL Server being a 'single-user database' ... ummm ... no, I
> don't think so. 

Hmmm ... perhaps it would be better if I said "serial-only database".   MSSQL 
(like earlier versions of Sybase) handles transactions by spooling everything 
out to a serial log, effectively making all transcations SERIAL isolation.   
This has some significant benefits in performance for OLAP and data 
warehousing, but really kills you on high-concurrency transaction processing.

> I'm REALLY happy to be shut of the Microsoft world, but 
> MSSQL 7/2000/2005 is a serious big DB engine. It also has some serious
> bright heads behind it. They hired Goetz Graefe and Paul (aka Per-Ake)
> Larsen away from academia, and it shows, in the join and aggregate
> processing. I'll be a happy camper if I manage to contribute something
> to PG that honks the way their stuff does. Happy to discuss, too.

Yeah, they also have very speedy cursor handling.  I can do things with 
cursors in MSSQL that I wouldn't consider with other DBs.   Not that that 
makes up for the lack of other functionality, but it is nice when you need 
it.

-- 
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Sun Aug 29 18:10:49 2004
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To: Mr Pink 
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 pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
References: <20040829180448.41247.qmail@web41108.mail.yahoo.com>
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Mr Pink  writes:

> AFAIK postgres doesn't peek at values used in a query when optimizing 

Of course it does.

However sometimes things don't work perfectly.
To get good answers rather than just guesses we'll need two things:

. What version of postgres are you using.
. The output of EXPLAIN ANALYZE select ...

-- 
greg


From pgsql-performance-owner@postgresql.org  Sun Aug 29 18:12:16 2004
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To: "Scott Marlowe" 
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	pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
References: 
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"Scott Marlowe"  writes:

> Also, count(*) is likely to always generate a seq scan due to the way
> aggregates are implemented currently in pgsql.  you might want to try:

Huh? I'm curious to know what you're talking about here.

> select somefield from sometable where timestampfield > now()-'60
> seconds'::interval
> 
> and count the number of returned rows.  If there's a lot, it won't be
> any faster, if there's a few, it should be a win.

Why would this ever be faster? And how could postgres ever calculate that
without doing a sequential scan when count(*) would force it to do a
sequential scan?

-- 
greg


From pgsql-performance-owner@postgresql.org  Sun Aug 29 18:36:26 2004
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From: "Scott Marlowe" 
To: "Greg Stark" 
Cc: "Jack Kerkhof" ,
	pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
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On Sun, 2004-08-29 at 15:12, Greg Stark wrote:
> "Scott Marlowe"  writes:
> 
> > Also, count(*) is likely to always generate a seq scan due to the way
> > aggregates are implemented currently in pgsql.  you might want to try:
> 
> Huh? I'm curious to know what you're talking about here.

This has been discussed ad infinitum on the lists in the past.  And
explained by better minds than mine, but I'll give it a go.

PostgreSQL has a "generic" aggregate method.  Imagine instead doing a
select count(id1+id2-id3) from table where ...  In that instance, it's
not a simple shortcut to just grab the number of rows anymore.  Since
PostgreSQL uses a generic aggregate method that can be expanded by the
user with custom aggregates et. al., it has no optimizations to make
simple count(*) fast, like many other databases.

Add to that the fact that even when postgresql uses an index it still
has to hit the data store to get the actual value of the tuple, and
you've got very few instances in which an index scan of more than some
small percentage of the table is worth while.  I.e. a sequential scan
tends to "win" over an index scan quicker in postgresql than in other
databases like Oracle, where the data store is serialized and the
indexes have the correct information along with the application of the
transaction / roll back segments.

> > select somefield from sometable where timestampfield > now()-'60
> > seconds'::interval
> > 
> > and count the number of returned rows.  If there's a lot, it won't be
> > any faster, if there's a few, it should be a win.
> 
> Why would this ever be faster? And how could postgres ever calculate that
> without doing a sequential scan when count(*) would force it to do a
> sequential scan?

Because, count(*) CANNOT use an index.  So, if you're hitting, say,
0.01% of the table (let's say 20 out of 20,000,000 rows or something
like that) then the second should be MUCH faster.


From pgsql-performance-owner@postgresql.org  Sun Aug 29 18:42:39 2004
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On Sun, 2004-08-29 at 15:38, Scott Marlowe wrote:
> On Sun, 2004-08-29 at 15:12, Greg Stark wrote:
> > "Scott Marlowe"  writes:
> > 
> > > Also, count(*) is likely to always generate a seq scan due to the way
> > > aggregates are implemented currently in pgsql.  you might want to try:
> > 
> > Huh? I'm curious to know what you're talking about here.
> 
> This has been discussed ad infinitum on the lists in the past.  And
> explained by better minds than mine, but I'll give it a go.
> 
> PostgreSQL has a "generic" aggregate method.  Imagine instead doing a
> select count(id1+id2-id3) from table where ... 

that should be avg(id1+id2-id3)... doh


From pgsql-performance-owner@postgresql.org  Sun Aug 29 19:03:47 2004
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To: "Jack Kerkhof" 
Cc: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index? 
In-reply-to: <87fz65k5sq.fsf@stark.xeocode.com> 
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>> select somefield from sometable where timestampfield > now()-'60
>> seconds'::interval

This is a FAQ, but since the archives don't seem to be up at the moment,
here's the answer once again:

The expression "now() - something" is not a constant, so the planner
is faced with "timestampfield > unknownvalue".  Its default assumption
about the number of rows that will match is much too high to make an
indexscan look profitable (from memory, I think it guesses that about
a third of the table will match...).

There are a couple of hacks you can use to deal with this.  Plan A
is just "set enable_seqscan = false" for this query.  This is ugly and
not really recommended, but you should try it first to verify that you
do get an indexscan that way, just to be sure that lack of statistics
is the problem and not something else.

Plan B is to add an extra WHERE clause to make the problem look like a
range query, eg

	where timestampfield > now() - ... AND timestampfield <= now();

The planner still doesn't know the exact values involved, so it still
can't make use of any statistics, but it can see that this is a range
constraint on timestampfield.  The default guess about the selectivity
will be a lot smaller than in the case of the one-sided inequality,
and in most cases you should get an indexscan out of it.  This isn't
completely guaranteed though.  Also, it's got a severe problem in that
if you sometimes do queries with a large interval, it'll still do an
indexscan even though that may be quite inappropriate.

Plan C is to fix things so that the compared-to value *does* look like a
constant; then the planner will correctly observe that only a small part
of the table is to be scanned, and do the right thing (given reasonably
up-to-date ANALYZE statistics, anyway).  The most trustworthy way of
doing that is to compute the "now() - interval" value on the client side
and send over a timestamp constant.  If that's not convenient for some
reason, people frequently use a hack like this:

	create function ago(interval) returns timestamptz as
	'select now() - $1' language sql strict immutable;

	select ... where timestampfield > ago('60 seconds');

This is a kluge because you are lying when you say that the result of
ago() is immutable; it obviously isn't.  But the planner will believe
you, fold the function call to a constant during planning, and use the
result.  CAUTION: this works nicely for interactively-issued SQL
queries, but it will come back to bite you if you try to use ago() in
prepared queries or plpgsql functions, because the premature collapsing
of the now() result will become significant.

We have speculated about ways to get the planner to treat expressions
involving now() and similar functions as pseudo-constants, so that it
would do the right thing in this sort of situation without any kluges.
It's not been done yet though.

BTW, the above discussion applies to PG 7.3 and later; if you're dealing
with an old version then there are some different considerations.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Sun Aug 29 19:04:18 2004
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From: "Steinar H. Gunderson" 
To: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
Message-ID: <20040829220413.GA1490@uio.no>
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On Sun, Aug 29, 2004 at 03:38:00PM -0600, Scott Marlowe wrote:
>>> select somefield from sometable where timestampfield > now()-'60
>>> seconds'::interval
>>> 
>>> and count the number of returned rows.  If there's a lot, it won't be
>>> any faster, if there's a few, it should be a win.
>> Why would this ever be faster? And how could postgres ever calculate that
>> without doing a sequential scan when count(*) would force it to do a
>> sequential scan?
> Because, count(*) CANNOT use an index.  So, if you're hitting, say,
> 0.01% of the table (let's say 20 out of 20,000,000 rows or something
> like that) then the second should be MUCH faster.

Of course count(*) can use an index:

images=# explain analyze select count(*) from images where event='test';
                                                             QUERY PLAN                                                             
------------------------------------------------------------------------------------------------------------------------------------
 Aggregate  (cost=168.97..168.97 rows=1 width=0) (actual time=68.211..68.215 rows=1 loops=1)
   ->  Index Scan using unique_filenames on images  (cost=0.00..168.81 rows=63 width=0) (actual time=68.094..68.149 rows=8 loops=1)
         Index Cond: ((event)::text = 'test'::text)
 Total runtime: 68.369 ms
(4 rows)

However, it cannot rely on an index _alone_; it has to go fetch the relevant
pages, but of course, so must "select somefield from" etc..

/* Steinar */
-- 
Homepage: http://www.sesse.net/

From pgsql-performance-owner@postgresql.org  Sun Aug 29 19:10:10 2004
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To: "Scott Marlowe" 
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	pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
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"Scott Marlowe"  writes:

> PostgreSQL has a "generic" aggregate method.  Imagine instead doing a
> select count(id1+id2-id3) from table where ...  In that instance, it's
> not a simple shortcut to just grab the number of rows anymore.  Since
> PostgreSQL uses a generic aggregate method that can be expanded by the
> user with custom aggregates et. al., it has no optimizations to make
> simple count(*) fast, like many other databases.

People expect count(*) _without a where clause_ to be cached in a single
global variable. Postgres can't do this, but the reason has everything to do
with MVCC, not with postgres's generalized aggregates. Because of MVCC
Postgres can't just store a single cached value, because there is no single
cached value. It would have to store a complete history back to the oldest
extant transaction.

However in this case the user has a where clause. No database is going to
cache values of count(*) for random where clauses. But that doesn't stop
Postgres from using an index to fetch the records.


> > > select somefield from sometable where timestampfield > now()-'60
> > > seconds'::interval
> > > 
> > > and count the number of returned rows.  If there's a lot, it won't be
> > > any faster, if there's a few, it should be a win.
> > 
> > Why would this ever be faster? And how could postgres ever calculate that
> > without doing a sequential scan when count(*) would force it to do a
> > sequential scan?
> 
> Because, count(*) CANNOT use an index.  So, if you're hitting, say,
> 0.01% of the table (let's say 20 out of 20,000,000 rows or something
> like that) then the second should be MUCH faster.

I think you've applied these past discussions and come up with some bogus
conclusions.

The problem here has nothing to do with the count(*) and everything to do with
the WHERE clause. To fetch the records satisfying that where clause postgres
has to do exactly the same thing regardless of whether it's going to feed the
data to count(*) or return some or all of it to the client.

If postgres decides the where clause isn't selective enough it'll choose to
use a sequential scan. However it would do that regardless of whether you're
calling count(*) or not. If the number is records is substantial then you
would get the overhead of the scan plus the time it takes to transfer all that
unnecessary data to the user.

What you're probably thinking of when you talk about general purpose aggregate
interfaces is the difficulty of making min()/max() use indexes. That's a whole
other case entirely. That's where postgres's generalized aggregates leaves it
without enough information about what records the aggregate functions are
interested in and what index scans might make them faster.

None of these common cases end up making it a good idea to read the records
into the clients and do the work in the client. The only cases where that
would make sense would be if the function requires doing some manipulation of
the data that's awkward to express in sql. The "top n" type of query is the
usual culprit, but with postgres's new array functions even that becomes
tractable.

-- 
greg


From pgsql-performance-owner@postgresql.org  Sun Aug 29 19:18:22 2004
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Subject: Re: Why does a simple query not use an obvious index?
From: Rod Taylor 
To: Greg Stark 
Cc: Scott Marlowe ,
	Jack Kerkhof ,
	Postgresql Performance 
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> People expect count(*) _without a where clause_ to be cached in a single
> global variable. Postgres can't do this, but the reason has everything to do

Someone should write an approx_count('table') function that reads
reltuples from pg_class and tell them to use it in combination with
autovac.

I've yet to see someone use count(*) across a table and not round the
result themselves (approx 9 million clients).



From pgsql-performance-owner@postgresql.org  Sun Aug 29 19:32:55 2004
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From: Russell Smith 
To: pgsql-performance@postgresql.org
Subject: Re: Query performance problem in 8.0.0beta1
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Hi,

I assume you have reposted because you have just signed up to the list.

If this is the case, can you please read the archives or replies to your original post about this question.
It did make it onto the archives and myself and others did reply with a few ideas and questions.

If you could address those in a reply mail that would help everybody with your problem

Regards

Russell Smith

From pgsql-performance-owner@postgresql.org  Sun Aug 29 23:10:03 2004
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Date: Sun, 29 Aug 2004 19:09:54 -0700 (PDT)
From: Mr Pink 
Subject: Re: Why does a simple query not use an obvious index?
To: pgsql-performance@postgresql.org
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--- Greg Stark  wrote:

> 
> Mr Pink  writes:
> 
> > AFAIK postgres doesn't peek at values used in a query when optimizing 
> 
> Of course it does.

But not ones returned by a function such as now(), or when you use bind variables, as Tom aptly
explained.

That's what I meant by 'peek'. Interestingly enough Oracle does that, it's inline with their
policy of recommending the use of bind variables. Perhaps postgres could use such a feature some
day.




		
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From pgsql-performance-owner@postgresql.org  Sun Aug 29 23:23:55 2004
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To: Mr Pink 
Cc: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index? 
In-reply-to: <20040830020954.3596.qmail@web41110.mail.yahoo.com> 
References: <20040830020954.3596.qmail@web41110.mail.yahoo.com>
Comments: In-reply-to Mr Pink 
	message dated "Sun, 29 Aug 2004 19:09:54 -0700"
Date: Sun, 29 Aug 2004 22:23:56 -0400
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From: Tom Lane 
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Mr Pink  writes:
>>> AFAIK postgres doesn't peek at values used in a query when optimizing 
>> 
>> Of course it does.

> But not ones returned by a function such as now(), or when you use
> bind variables, as Tom aptly explained.

FWIW, 8.0 does have the ability to use the values of bind variables for
planning estimation (Oliver Jowett did the work for this).  The main
issue in the way of dealing with now() is that whatever we did to now()
would apply to all functions marked "stable", and it's a bit
nervous-making to assume that they should all be treated this way.
Or we could introduce more function volatility categories, but that's
not much fun either.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Mon Aug 30 04:38:49 2004
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Yeah! Bind variable peeking is great news. I did actually read the guff, but forgot about that.

Version 8 is looking great on paper, I hope I'll get a chance to play wth it soon.

I can kind of appreciate your point about peeking stable functions, however, I would have thought
that if it was possible to do for bind variables (which could change many times in a transaction)
then it would make even more sense for a stable function which doesn't change for the life of the
transaction. No doubt this is an oversimplification the situation.

regards
Mr Pink


		
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From pgsql-performance-owner@postgresql.org  Mon Aug 30 05:20:09 2004
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Date: Mon, 30 Aug 2004 20:19:59 +1200
From: Guy Thornley 
To: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
Message-ID: <20040830081959.GC3714@conker.esphion.com>
Reply-To: Guy Thornley 
References: 
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On Sun, Aug 29, 2004 at 06:03:43PM -0400, Tom Lane wrote:
> >> select somefield from sometable where timestampfield > now()-'60
> >> seconds'::interval
> 
> This is a FAQ, but since the archives don't seem to be up at the moment,
> here's the answer once again:
> 
> The expression "now() - something" is not a constant, so the planner
> is faced with "timestampfield > unknownvalue".  Its default assumption
> about the number of rows that will match is much too high to make an
> indexscan look profitable (from memory, I think it guesses that about
> a third of the table will match...).


Ok; this explains some really wierd stuff I've been seeing.

However, I'm seeing breakage of the form mentioned by the original poster
even when the query uses a _constant_ timestamp: [Postgres 7.4.3]

        ntais# \d detect.stats
                                                 Table "detect.stats"
            Column    |           Type           |                          Modifiers                          
        --------------+--------------------------+-------------------------------------------------------------
         anomaly_id   | integer                  | not null
         at           | timestamp with time zone | not null default ('now'::text)::timestamp(6) with time zone
         resolution   | real                     | default 1.0
         values       | real[]                   | 
         stat_type_id | integer                  | not null
        Indexes:
            "stats_pkey" primary key, btree (anomaly_id, stat_type_id, "at")
            "stats__ends_at" btree (stats__ends_at("at", resolution, "values"))
        Foreign-key constraints:
            "$1" FOREIGN KEY (anomaly_id) REFERENCES anomalies(anomaly_id) ON DELETE CASCADE
            "$2" FOREIGN KEY (stat_type_id) REFERENCES stat_types(stat_type_id)


        ntais=# SET enable_seqscan = on;
        SET
        ntais=# EXPLAIN ANALYZE                                       
          SELECT anomaly_id, stat_type_id
          FROM detect.stats
          WHERE detect.stats__ends_at(at, resolution, values) > '2004-08-30 16:21:09+12'::timestamptz
          ORDER BY anomaly_id, stat_type_id
          ;

                                                                 QUERY PLAN                                                          
        -----------------------------------------------------------------------------------------------------------------------------
         Sort  (cost=602473.59..608576.72 rows=2441254 width=8) (actual time=198577.407..198579.136 rows=6152 loops=1)
           Sort Key: anomaly_id, stat_type_id
           ->  Seq Scan on stats  (cost=0.00..248096.42 rows=2441254 width=8) (actual time=198299.685..198551.460 rows=6152 loops=1)
                 Filter: (stats__ends_at("at", resolution, "values") > '2004-08-30 16:21:09+12'::timestamp with time zone)
         Total runtime: 198641.649 ms
        (5 rows)


        ntais=# EXPLAIN ANALYZE
          SELECT anomaly_id, stat_type_id
          FROM detect.stats
          WHERE detect.stats__ends_at(at, resolution, values) > '2004-08-30
          16:21:09+12'::timestamptz
          ORDER BY anomaly_id, stat_type_id
          ;

                                                                         QUERY PLAN                                                                 
        --------------------------------------------------------------------------------------------------------------------------------------------
         Sort  (cost=10166043.26..10172146.40 rows=2441254 width=8) (actual time=44.710..46.661 rows=6934 loops=1)
           Sort Key: anomaly_id, stat_type_id
           ->  Index Scan using stats__ends_at on stats  (cost=0.00..9811666.09 rows=2441254 width=8) (actual time=0.075..24.702 rows=6934 loops=1)
         Index Cond: (stats__ends_at("at", resolution, "values") > '2004-08-30 16:21:09+12'::timestamp with time zone)
         Total runtime: 50.354 ms
        (5 rows)


        ntais=# SELECT count(*) FROM detect.stats;
          count  
        ---------
         7326151
        (1 row)

Ive done repeated ANALYZE's, both table-specific and database-wide, and get
the same result every time.

For us, a global 'enable_seqscan = off' in postgresql.conf is the way to go.
You occasionally see an odd plan while developing a query (eg: scanning an
index with no contraint to simply get ORDER BY). Usually thats a broken
query/index, and I simply fix it.


Guy Thornley

From pgsql-performance-owner@postgresql.org  Mon Aug 30 12:41:04 2004
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To: Guy Thornley 
Cc: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index? 
In-reply-to: <20040830081959.GC3714@conker.esphion.com> 
References: 
	<1093804128.5493.22.camel@localhost.localdomain>
	<87fz65k5sq.fsf@stark.xeocode.com> <16093.1093817023@sss.pgh.pa.us>
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Comments: In-reply-to Guy Thornley 
	message dated "Mon, 30 Aug 2004 20:19:59 +1200"
Date: Mon, 30 Aug 2004 11:41:02 -0400
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From: Tom Lane 
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Guy Thornley  writes:
> However, I'm seeing breakage of the form mentioned by the original poster
> even when the query uses a _constant_ timestamp: [Postgres 7.4.3]

>         Indexes:
>             "stats_pkey" primary key, btree (anomaly_id, stat_type_id, "at")
>             "stats__ends_at" btree (stats__ends_at("at", resolution, "values"))

>         ntais=# EXPLAIN ANALYZE                                       
>           SELECT anomaly_id, stat_type_id
>           FROM detect.stats
>           WHERE detect.stats__ends_at(at, resolution, values) > '2004-08-30 16:21:09+12'::timestamptz
>           ORDER BY anomaly_id, stat_type_id
>           ;

Here I'm afraid you're just stuck until 8.0 comes out (or you're feeling
brave enough to use a beta).  Releases before 8.0 do not maintain any
statistics about the contents of functional indexes, so the planner is
flying blind here in any case, and you end up with the very same 1/3rd
default assumption no matter what the right-hand side looks like.
You'll have to fall back to Plan A or Plan B to get this case to work
in 7.4.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Mon Aug 30 12:41:11 2004
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To: Guy Thornley 
Cc: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
References: 
	<1093804128.5493.22.camel@localhost.localdomain>
	<87fz65k5sq.fsf@stark.xeocode.com> <16093.1093817023@sss.pgh.pa.us>
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From: Greg Stark 
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Guy Thornley  writes:

>             "stats__ends_at" btree (stats__ends_at("at", resolution, "values"))

Postgres 7.4 doesn't have any stats on functional indexes. So it's back to
just guessing at the selectivity of this. 8.0 does gather stats for functional
indexes so it should be better off.

-- 
greg


From pgsql-performance-owner@postgresql.org  Mon Aug 30 13:02:31 2004
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Date: Mon, 30 Aug 2004 18:02:28 +0200
From: "Steinar H. Gunderson" 
To: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
Message-ID: <20040830160228.GB16847@uio.no>
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On Sun, Aug 29, 2004 at 06:03:43PM -0400, Tom Lane wrote:
> The expression "now() - something" is not a constant, so the planner
> is faced with "timestampfield > unknownvalue".  Its default assumption
> about the number of rows that will match is much too high to make an
> indexscan look profitable (from memory, I think it guesses that about
> a third of the table will match...).

Out of curiosity, does the subselect query I presented earlier in the thread
count as "a constant"? It gives the correct query plan, but this could of
course just be correct by accident...

/* Steinar */
-- 
Homepage: http://www.sesse.net/

From pgsql-performance-owner@postgresql.org  Mon Aug 30 13:47:32 2004
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To: "Steinar H. Gunderson" 
Cc: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index? 
In-reply-to: <20040830160228.GB16847@uio.no> 
References: 
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	<87fz65k5sq.fsf@stark.xeocode.com> <16093.1093817023@sss.pgh.pa.us>
	<20040830160228.GB16847@uio.no>
Comments: In-reply-to "Steinar H. Gunderson" 
	message dated "Mon, 30 Aug 2004 18:02:28 +0200"
Date: Mon, 30 Aug 2004 12:47:23 -0400
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From: Tom Lane 
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"Steinar H. Gunderson"  writes:
> On Sun, Aug 29, 2004 at 06:03:43PM -0400, Tom Lane wrote:
>> The expression "now() - something" is not a constant, so the planner
>> is faced with "timestampfield > unknownvalue".

> Out of curiosity, does the subselect query I presented earlier in the thread
> count as "a constant"? It gives the correct query plan, but this could of
> course just be correct by accident...

That was on 7.2, wasn't it?  I don't remember any longer exactly how 7.2
does this stuff, but it's different from 7.3 and later (and certainly
not any more "right").

You did at one time need to hide now() in a subselect to get the planner
to consider an indexscan at all --- that was before we made the
distinction between immutable and stable functions, and so now() had
to be treated as unsafe to index against (just as random() still is).
I think 7.2 behaved that way but I'm not totally sure.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Mon Aug 30 14:46:44 2004
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Subject: seqscan instead of index scan
From: Martin Sarsale 
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Dear all:

Im having a weird problem here. I have a table w/ ~180.000 rows and I
want to select those where c > 0 or d > 0 (there only a few of those on
the table)
I indexed columns c and d (separately) but this query used the slow
seqscan instead of the index scan:

select * from t where c<>0 or d<>0;

After playing some time, I noticed that if I change the "or" for an
"and", pg used the fast index scan (but the query w/ 'and' was not what
I as looking for).

Then, I thought I could do the following:
Creating an index with the expression (c+d) and selecting the rows where
c+d > 0:
select * from t where c + d <> 0;

Again, this used a seqscan. Asking in #postgresql in freenode, somebody
told me to try to disable seqscan (set enable_seqscan false) and
suprisingly, Pg started using the index scan and it was -fast-.

Now: I've no idea why it chooses to use a seq scan instead of the index
scan (yes, I've just vacuum analyzed the table before running the
query).

Some more info:
c and d are both bigint. I've tried the queries casting the constant (0)
to bigint but nothing changed.

Im using debian's pg 7.4.1-2.


Thanks in advance


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From pgsql-performance-owner@postgresql.org  Mon Aug 30 14:53:46 2004
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From: Bruno Wolff III 
To: Martin Sarsale 
Cc: pgsql-performance@postgresql.org
Subject: Re: seqscan instead of index scan
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On Mon, Aug 30, 2004 at 14:46:37 -0300,
  Martin Sarsale  wrote:
> Dear all:
> 
> Im having a weird problem here. I have a table w/ ~180.000 rows and I
> want to select those where c > 0 or d > 0 (there only a few of those on
> the table)
> I indexed columns c and d (separately) but this query used the slow
> seqscan instead of the index scan:

Postgres doesn't 'or' bitmaps derived from two indexes. You might have more
luck using a combined index.

> 
> select * from t where c<>0 or d<>0;
> 
> After playing some time, I noticed that if I change the "or" for an
> "and", pg used the fast index scan (but the query w/ 'and' was not what
> I as looking for).
> 
> Then, I thought I could do the following:
> Creating an index with the expression (c+d) and selecting the rows where
> c+d > 0:
> select * from t where c + d <> 0;
> 
> Again, this used a seqscan. Asking in #postgresql in freenode, somebody
> told me to try to disable seqscan (set enable_seqscan false) and
> suprisingly, Pg started using the index scan and it was -fast-.
> 
> Now: I've no idea why it chooses to use a seq scan instead of the index
> scan (yes, I've just vacuum analyzed the table before running the
> query).
> 
> Some more info:
> c and d are both bigint. I've tried the queries casting the constant (0)
> to bigint but nothing changed.
> 
> Im using debian's pg 7.4.1-2.
> 
> 
> Thanks in advance
> 



From pgsql-performance-owner@postgresql.org  Mon Aug 30 15:06:57 2004
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From: "Merlin Moncure" 
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> Im having a weird problem here. I have a table w/ ~180.000 rows and I
> want to select those where c > 0 or d > 0 (there only a few of those
on
> the table)
> I indexed columns c and d (separately) but this query used the slow
> seqscan instead of the index scan:

create function is_somethingable (ctype, dtype) returns boolean as
'
	return case when $1 > 0 and $2 > 0 then true else false end;
' language sql immutable;

create index t_idx on t(is_somethingable(c,d));

analyze t;

select * from t where is_somethingable(t.c, t.d) =3D true;

Merlin


From pgsql-performance-owner@postgresql.org  Mon Aug 30 15:07:23 2004
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Subject: Re: seqscan instead of index scan
From: Martin Sarsale 
To: Bruno Wolff III 
Cc: pgsql-performance@postgresql.org
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On Mon, 2004-08-30 at 15:02, Bruno Wolff III wrote:
> On Mon, Aug 30, 2004 at 14:46:37 -0300,

> > Im having a weird problem here. I have a table w/ ~180.000 rows and I
> > want to select those where c > 0 or d > 0 (there only a few of those on
> > the table)
> > I indexed columns c and d (separately) but this query used the slow
> > seqscan instead of the index scan:
>=20
> Postgres doesn't 'or' bitmaps derived from two indexes. You might have mo=
re
> luck using a combined index.

With combined index, you mean a multiple column index?
From
http://www.postgresql.org/docs/7.4/interactive/indexes-multicolumn.html
=20
"Multicolumn indexes can only be used if the clauses involving the
indexed columns are joined with AND. For instance,

SELECT name FROM test2 WHERE major =3D constant OR minor =3D constant;

cannot make use of the index test2_mm_idx defined above to look up both
columns. (It can be used to look up only the major column, however.) "

But I need something like:

select * from t where c<>0 or d<>0;



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Subject: Re: seqscan instead of index scan
From: Martin Sarsale 
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On Mon, 2004-08-30 at 15:06, Merlin Moncure wrote:
> create function is_somethingable (ctype, dtype) returns boolean as

Thanks, but I would prefer a simpler solution.

I would like to know why this uses a seqscan instead of an index scan:

create index t_idx on t((c+d));
select * from t where c+d > 0;=20



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From pgsql-performance-owner@postgresql.org  Mon Aug 30 15:29:31 2004
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> On Mon, 2004-08-30 at 15:06, Merlin Moncure wrote:
> > create function is_somethingable (ctype, dtype) returns boolean as
>=20
> Thanks, but I would prefer a simpler solution.
>=20
> I would like to know why this uses a seqscan instead of an index scan:
>=20
> create index t_idx on t((c+d));
> select * from t where c+d > 0;
>=20

hmmm, please define simple.=20=20

Using a functional index you can define an index around the way you
access the data.  There is no faster or better way to do it...this is a
mathematical truth, not a problem with the planner.  Why not use the
right tool for the job?  A boolean index is super-efficient both in disk
space and cache utilization.

Multiple column indexes are useless for 'or' combinations! (however they
are a huge win for 'and' combinations because you don't have to merge).

With an 'or' expression, the planner must use one index or the other, or
use both and merge the results.  When and what the planner uses is an
educated guess based on statistics.

Also, your function can be changed...why fill all your queries with
Boolean cruft when you can abstract it into the database and reap the
speed savings at the same time?  I think it's time to rethink the
concept of 'simple'.

Constructive criticism all,
Merlin



From pgsql-performance-owner@postgresql.org  Mon Aug 30 16:15:31 2004
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To: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
References: <20040829180448.41247.qmail@web41108.mail.yahoo.com>
Message-ID: 
Date: Mon, 30 Aug 2004 21:17:06 +0200
From: =?utf-8?Q?Pierre-Fr=C3=A9d=C3=A9ric_Caillaud?=
	
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	Most likely your table has a SERIAL PRIMARY KEY in it, in this case, do  
the following :

   	my_limit = select primary_key_field from billing where timestamp >  
(now()-60)::timestamp ORDER BY timestamp ASC LIMIT 1;

	then

	SELECT count(*) FROM billing WHERE primary_key_field>=my_limit;

	I don't know if it'll work better, but you can try.

	When you insert records in the table, they are appended at the end, so  
this type of recent records query only requires reading the tail of the  
table. It should be fast if planned correctly.

> Strangely enough, I don't find that result surprising.
>
> if the vast bulk of the data is in the past and now()-60 represents a  
> very small slice of the data
> we might expect that using an index is optimal, but there could be many  
> reasons why it doesn't get
> used.
>
> AFAIK postgres doesn't peek at values used in a query when optimizing so  
> any query with a ">" type
> condition is gonna have a seq scan as the plan since the best guess is  
> that you are gonna match
> 50% of the table. That's one possible explanation.
>
> Another is that if the condition data types don't match then an indes  
> won't be used you could try:
>
>   select count(*) from billing where timestamp > (now()-60)::timestamp
>
> Might make a difference, I dunno, it's a case of testing amd seing what  
> happens.
>
> You could try lowering the random page cost, it might help, but I don't  
> like your chances.
>
> If your problem is that you want to access the most recent data from a  
> large table with fast
> response, then you could consider:
>
> 1. a "recent" index. If the data is within the "recent" time from set a  
> flag to true, other wise
> null. Reset the flags periodically. Nulls aren't indexed so the  
> selectivity of such an index is
> much higher. Can work wonders.
>
> 2, duplicate recent data in another table that is purged when data  
> passes the age limit. This is
> basic archiving.
>
> Something like that. Hopefully someone with more knowlege of the  
> optimaizer will have a brighter
> suggestion for you.
>
> What version are you using by the way?
> Regards
> Mr Pink
> --- Jack Kerkhof  wrote:
>
>> The query:
>>     select count(*) from billing where timestamp > now()-60
>>
>> should obviously use the index
>>
>>     CREATE INDEX billing_timestamp_idx ON billing USING btree  
>> ("timestamp"
>> timestamp_ops);
>>
>> on a table with 1400000 rows.
>>
>> But it uses a Seq Scan. If I set enable_seqscan=no, it indicates a  
>> queryplan
>> could not be calculated.
>>
>> Why does this simple query not use the timestamp index, and how can I  
>> get it
>> to?
>>
>> Thanks, Jack
>>
>>      Jack Kerkhof
>>       Research & Development
>>       jack.kerkhof@guest-tek.com
>>       www.guest-tek.com
>>       1.866.509.1010 3480
>>
>> --------------------------------------------------------------------------
>>
>>       Guest-Tek is a leading provider of broadband technology solutions  
>> for
>> the hospitality industry. Guest-Tek's GlobalSuite�Ehigh-speed Internet
>> solution enables hotels to offer their guests the convenience of wired
>> and/or wireless broadband Internet access from guest rooms, meeting  
>> rooms
>> and public areas.
>>
>>
>>
>
>
>
> 		
> __________________________________
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From pgsql-performance-owner@postgresql.org  Mon Aug 30 16:09:22 2004
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From: Bruno Wolff III 
To: Martin Sarsale 
Cc: pgsql-performance@postgresql.org
Subject: Re: seqscan instead of index scan
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On Mon, Aug 30, 2004 at 15:07:15 -0300,
  Martin Sarsale  wrote:
> 
> With combined index, you mean a multiple column index?
> From
> http://www.postgresql.org/docs/7.4/interactive/indexes-multicolumn.html

You are right, a multicolumn index doesn't help for 'or'.

From pgsql-performance-owner@postgresql.org  Mon Aug 30 16:19:45 2004
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Subject: Re: Why does a simple query not use an obvious index?
References: 
	<1093804128.5493.22.camel@localhost.localdomain>
	<87fz65k5sq.fsf@stark.xeocode.com>
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Date: Mon, 30 Aug 2004 21:21:26 +0200
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>> Also, count(*) is likely to always generate a seq scan due to the way
>> aggregates are implemented currently in pgsql.  you might want to try:


	By the way, in an ideal world, count(*) should only read the index on the  
timetamp column, not the rows. I guess this is not the case. Would this be  
an useful optimization ?

From pgsql-performance-owner@postgresql.org  Mon Aug 30 16:30:50 2004
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	Another primary key trick :

	If you insert records with a serial primary key, and rarely delete them  
or update the timestamp, you can use the primary key to compute an  
approximate number of rows.

	a := SELECT pkey FROM table WHERE timestamp() > threshold ORDER BY  
timestamp ASC LIMIT 1;
	b := SELECT pkey FROM table WHERE ORDER BY pkey DESC LIMIT 1;

	(b-a) is an approximate count.

	Performance is great because you only fetch two rows. Index scan is  
guaranteed (LIMIT 1). On the downside, you get an approximation, and this  
only works for tables where timestamp is a date of INSERT, timestamp  
worrelated wiht pkey) not when timestamp is a date of UPDATE (uncorrelated  
with pkey).

From pgsql-performance-owner@postgresql.org  Mon Aug 30 16:37:36 2004
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Subject: Re: seqscan instead of index scan
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Date: Mon, 30 Aug 2004 21:39:17 +0200
From: =?iso-8859-15?Q?Pierre-Fr=E9d=E9ric_Caillaud?=
	
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>> create index t_idx on t((c+d));
>> select * from t where c+d > 0;

	Why not :

	select ((select * from t where c<>0::bigint) UNION (select * from t where  
d<>0::bigint))
	group by whatever;

	or someting ?

From pgsql-performance-owner@postgresql.org  Mon Aug 30 16:32:07 2004
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To: =?iso-8859-1?Q?Pierre-Fr=E9d=E9ric?= Caillaud
 
Cc: pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
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	,
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On Mon, Aug 30, 2004 at 21:21:26 +0200,
  Pierre-Fr�d�ric Caillaud  wrote:
> >>Also, count(*) is likely to always generate a seq scan due to the way
> >>aggregates are implemented currently in pgsql.  you might want to try:
> 
> 
> 	By the way, in an ideal world, count(*) should only read the index 
> 	on the  timetamp column, not the rows. I guess this is not the case. Would 
> this be  an useful optimization ?

It's in the archives. The short answer is that no, postgres has to check
the heap to check tuple visibility to the current transaction.

From pgsql-performance-owner@postgresql.org  Mon Aug 30 17:04:10 2004
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From: Stephan Szabo 
To: Martin Sarsale 
Cc: pgsql-performance@postgresql.org
Subject: Re: seqscan instead of index scan
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On Mon, 30 Aug 2004, Martin Sarsale wrote:

> On Mon, 2004-08-30 at 15:06, Merlin Moncure wrote:
> > create function is_somethingable (ctype, dtype) returns boolean as
>
> Thanks, but I would prefer a simpler solution.
>
> I would like to know why this uses a seqscan instead of an index scan:
>
> create index t_idx on t((c+d));
> select * from t where c+d > 0;

As a geuss, since 7.4 and earlier have no statistics on the distribution
of c+d it has to guess about how likely that is to be true and is probably
overestimating. 8.0beta might handle this better.

From pgsql-performance-owner@postgresql.org  Mon Aug 30 17:18:52 2004
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To: Mr Pink 
Cc: Tom Lane , pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
References: <20040830073841.30957.qmail@web41108.mail.yahoo.com>
In-Reply-To: <20040830073841.30957.qmail@web41108.mail.yahoo.com>
From: Greg Stark 
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[I'm actually responding to the previous post from Tom Lane, but I've deleted
it and the archives seem to be down again.]


The assumption being made is that the first provided result is representative
of all future results. I don't see any reason that making this assumption of
all stable functions should be less scary than making the assumption about
user provided parameters.

However I have the complementary reaction. I find peeking at the first
bind parameter to be scary as hell. Functions seem slightly less scary.

On Oracle Peeking at bind parameters is a feature explicitly intended for DSS
data warehouse type systems. The use of placeholders there was purely for
security and programming ease, not efficiency, since the queries are only
planned executed a small number of times per plan. These are systems that
suffered enormously without the parameter values. They often involved full
table scans or bitmap index scans and without the statistics produced awful
plans.

For OLTP systems peeking at placeholders is more a danger than a benefit. The
query will be executed thousands of times and if it's planned based on a
single unusual value initially the entire system could fail.

Consider the following scenario which isn't farfetched at all. In fact I think
it well describes my current project:

I have a table with a few million records. 99% of the time users are working
with only a few hundred records at most. There's an index on the column
they're keying off of. 1% of the key values have an unusually large number of
records.

Without peeking at placeholders the system should see that virtually all the
key values are well under the threshold for an index scan to be best. So it
always uses an index scan. 1% of the time it takes longer than that it would
have with a sequential scan, but only by a small factor. (On the whole we're
probably still better off avoiding the cache pollution anyways.)

With peeking at placeholders 99% of the backends would perform the same way.
However 1 backend in 100 sees one of these unusual values for its first query.
This backend will use a sequential scan for *every* request. Executing a
sequential table scan of this big table once a second this backend will drive
the entire system into the ground.

This means every time I start the system up I stand a small but significant
chance of it just completely failing to perform properly. Worse, apache is
designed to periodically start new processes, so at any given time the system
could just randomly fall over and die.

I would rather incur a 10% penalty on every query than have a 1% chance of it
keeling over and dieing. Given this I would when I upgrade to 8.0 have to
ensure that my application driver is either not using placeholders at all (at
the protocol level -- I always prefer them at the api level) or ensure that
postgres is *not* peeking at the value.

I like the feature but I just want to be sure that it's optional.

-- 
greg


From pgsql-performance-owner@postgresql.org  Mon Aug 30 17:36:40 2004
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To: Martin Sarsale 
Cc: pgsql-performance@postgresql.org
Subject: Re: seqscan instead of index scan
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	<1093889849.1680.83.camel@kadaif>
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Another option here is to use a partial index. You can index on some other
column -- perhaps the column you want the results ordered by where the where
clause is true.

Something like:

create index t_idx on t (name) where c>0 and d>0;

then any select with a matching where clause can use the index:

select * from t where c>0 and d>0 order by name

Could scan the index and not even have to sort on name.

-- 
greg


From pgsql-performance-owner@postgresql.org  Mon Aug 30 17:48:11 2004
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To: Martin Sarsale 
Cc: pgsql-performance@postgresql.org
Subject: Re: seqscan instead of index scan 
In-reply-to: <1093887997.1680.71.camel@kadaif> 
References: <1093887997.1680.71.camel@kadaif>
Comments: In-reply-to Martin Sarsale 
	message dated "Mon, 30 Aug 2004 14:46:37 -0300"
Date: Mon, 30 Aug 2004 16:48:05 -0400
Message-ID: <11309.1093898885@sss.pgh.pa.us>
From: Tom Lane 
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Martin Sarsale  writes:
> I indexed columns c and d (separately) but this query used the slow
> seqscan instead of the index scan:

> select * from t where c<>0 or d<>0;

> After playing some time, I noticed that if I change the "or" for an
> "and", pg used the fast index scan (but the query w/ 'and' was not what
> I as looking for).

I don't think so.  <> is not an indexable operator --- it appears
nowhere in the index operator classes.  It would help if you showed us
*exactly* what you did instead of a not-very-accurate filtered version.
I'm going to assume that you meant > ...

> Now: I've no idea why it chooses to use a seq scan instead of the index
> scan (yes, I've just vacuum analyzed the table before running the
> query).

Because 7.4 doesn't have statistics about expression indexes, so it has
no idea that there are only a few rows with c+d > 0.

What I'd suggest is

	select * from t where c>0 union select * from t where d>0

with separate indexes on c and d.

Another possibility is a partial index on exactly the condition you
want:

	create index nonzero on t(c) where c>0 or d>0;

although I'm not certain if 7.4 has enough stats to recognize this as a win.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Mon Aug 30 18:00:08 2004
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To: Greg Stark 
Cc: Mr Pink ,
	pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index? 
In-reply-to: <87ekloidls.fsf@stark.xeocode.com> 
References: <20040830073841.30957.qmail@web41108.mail.yahoo.com>
	<87ekloidls.fsf@stark.xeocode.com>
Comments: In-reply-to Greg Stark 
	message dated "30 Aug 2004 16:18:39 -0400"
Date: Mon, 30 Aug 2004 17:00:00 -0400
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From: Tom Lane 
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Greg Stark  writes:
> However I have the complementary reaction. I find peeking at the first
> bind parameter to be scary as hell. Functions seem slightly less scary.

FWIW, we only do it in the context of unnamed parameterized queries.
As the protocol docs say, those are optimized on the assumption that
they will be executed only once.  It seems entirely legitimate to me 
to use the parameter values in such a case.

We might in future get braver about using sample parameter values,
but 8.0 is conservative about it.

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Tue Aug 31 03:00:56 2004
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To: Tom Lane 
Cc: Greg Stark , Mr Pink ,
	pgsql-performance@postgresql.org
Subject: Re: Why does a simple query not use an obvious index?
References: <20040830073841.30957.qmail@web41108.mail.yahoo.com>
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Tom Lane  writes:

> Greg Stark  writes:
> > However I have the complementary reaction. I find peeking at the first
> > bind parameter to be scary as hell. Functions seem slightly less scary.
> 
> FWIW, we only do it in the context of unnamed parameterized queries.

I knew that. That's why I hadn't been jumping up and down screaming. I was
watching though to insist on an option to disable it if it became more
widespread.

> As the protocol docs say, those are optimized on the assumption that
> they will be executed only once.  It seems entirely legitimate to me 
> to use the parameter values in such a case.

Sure. It's a great feature to have; it means people can be more aggressive
about using placeholders for other reasons without worrying about performance
impacts.

> We might in future get braver about using sample parameter values,
> but 8.0 is conservative about it.

If they're used for named parameters I would strongly recommend guc variable
to control the default on a server-wide basis. It could be a variable that
individual sessions could override since there's no security or resource
implications. It's purely a protocol interface issue.

For that matter, would it be possible for the default selectivity estimates to
be a guc variable? It's something that the DBA -- or even programmer on a
per-session basis -- might be able to provide a better value for his
applications than any hard coded default.

Or perhaps it would be one valid use of hints to provide selectivity estimates
for blind placeholders. It would be nice to be able to say for example:

  select * from foo where col > $0 /*+ 5% */ AND col2 > $1 /*+ 10% */

Would there be any hope of convincing you that this is a justifiable use of
hints; providing information that the optimizer has absolutely no possibility
of ever being able to calculate on its own?

-- 
greg


From pgsql-performance-owner@postgresql.org  Tue Aug 31 12:14:47 2004
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Subject: Re: seqscan instead of index scan
From: Martin Sarsale 
To: Merlin Moncure 
Cc: pgsql-performance@postgresql.org
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> Using a functional index you can define an index around the way you
> access the data.  There is no faster or better way to do it...this is a
> mathematical truth, not a problem with the planner.  Why not use the
> right tool for the job?  A boolean index is super-efficient both in disk
> space and cache utilization.

Thanks for your constructive criticism, you're absolutely right.

I had to modify your "return" for a "select":

create function rankeable (bigint, bigint) returns boolean as '
        select case when $1 > 0 or $2 > 0 then true else false end;'
language sql immutable;

and it works great.



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From pgsql-performance-owner@postgresql.org  Tue Aug 31 12:27:55 2004
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Date: Tue, 31 Aug 2004 17:27:41 +0200
From: Jean-Max Reymond 
Reply-To: Jean-Max Reymond 
To: pgsql-performance@postgresql.org
Subject: Performance with Intel Compiler
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hi,
has anyone compile Postgres with Intel compiler ?
Does it exist a substantial gain of performance ?


-- 
Jean-Max Reymond
CKR Solutions
http://www.ckr-solutions.com

From pgsql-odbc-owner@postgresql.org  Tue Aug 31 14:26:56 2004
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Subject: odbc/ado problems
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Hi all!

I'm new here, so hello to everybody!

I'm in a deep truble using postgesSQL 7.2.0 on a low-end pc with SUSE 8. I'm
using some databases from that pc through odbc (7.3.200). Until now i had no
problems with this solution, everithing worked fine. But today i wrote a
small app, that converts/copies some data from a database to an other
database.

During this work i wrote a simple query as follows:
select pers_driving_license from person where pers_id=23456

This should return a single varchar(20) field. Running this query over
ADO/ODBC from a Delphi app tooks 50-100 secs. If i run this from pgAdmin II.
it takes some msecs.

The output of explain is:
Index Scan using person_id_index on person (cost=0.00..3.14 rows=1 width=4)

Any idea?

Thanks in advance: steve


From pgsql-performance-owner@postgresql.org  Tue Aug 31 14:33:20 2004
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From: "Merlin Moncure" 
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> I'm new here, so hello to everybody!
>=20
> I'm in a deep truble using postgesSQL 7.2.0 on a low-end pc with SUSE 8.
> I'm
> using some databases from that pc through odbc (7.3.200). Until now i had
> no
> problems with this solution, everithing worked fine. But today i wrote a
> small app, that converts/copies some data from a database to an other
> database.
>=20
> During this work i wrote a simple query as follows:
> select pers_driving_license from person where pers_id=3D23456
>=20
> This should return a single varchar(20) field. Running this query over
> ADO/ODBC from a Delphi app tooks 50-100 secs. If i run this from pgAdmin
> II.
> it takes some msecs.

Question: what is your Delphi database driver?  If you are using the BDE, t=
hat might be your problem.  Try installing and using the ZeosLib toolkit.

http://www.zeoslib.org

Merlin

From pgsql-performance-owner@postgresql.org  Tue Aug 31 15:09:44 2004
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Date: Tue, 31 Aug 2004 11:11:02 -0700
From: Ron St-Pierre 
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Subject: Table UPDATE is too slow
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 We have a web based application with data that is updated daily. The 
biggest bottleneck occurs when we try to update
 one of the tables. This table contains 58,000 rows and 62 columns, and 
EVERY column is indexed. Every column is
 queryable (?) by the users through the web interface so we are 
reluctant to remove the indexes (recreating them would
 be time consuming too). The primary key is an INT and the rest of the 
columns are a mix of NUMERIC, TEXT, and DATEs.
 A typical update is:
   UPDATE dataTable SET field01=44.5, field02=44.5, field03='Bob',
     field04='foo', ... , field60='2004-08-30', field61='2004-08-29'
     WHERE id = 1234;

 Also of note is that the update is run about 10 times per day; we get 
blocks of data from 10 different sources, so we pre-process the
 data and then update the table. We also run VACUUM FULL ANALYZE on a 
nightly basis.
 
 Does anyone have some idea on how we can increase speed, either by 
changing the updates, designing the database
 differently, etc, etc? This is currently a big problem for us.
 
 Other notables:
   The UPDATE is run from a within a function: FOR rec IN SELECT ...LOOP 
RETURN NEXT rec; UPDATE dataTable.....
   Postgres 7.4.3
   debian stable
   2 GB RAM
   80 DB IDE drive (we can't change it)
 
   shared_buffers = 2048
   sort_mem = 1024  
   max_fsm_pages = 40000
   checkpoint_segments = 5
   random_page_cost = 3
 
 
 Thanks
 
 Ron



From pgsql-performance-owner@postgresql.org  Tue Aug 31 15:16:34 2004
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Cc: pgsql-performance@postgresql.org
From: Thomas F.O'Connell 
Subject: Re: Table UPDATE is too slow
Date: Tue, 31 Aug 2004 13:16:22 -0500
To: Ron St-Pierre 
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What is the datatype of the id column?

-tfo

On Aug 31, 2004, at 1:11 PM, Ron St-Pierre wrote:

> We have a web based application with data that is updated daily. The 
> biggest bottleneck occurs when we try to update
> one of the tables. This table contains 58,000 rows and 62 columns, and 
> EVERY column is indexed. Every column is
> queryable (?) by the users through the web interface so we are 
> reluctant to remove the indexes (recreating them would
> be time consuming too). The primary key is an INT and the rest of the 
> columns are a mix of NUMERIC, TEXT, and DATEs.
> A typical update is:
>   UPDATE dataTable SET field01=44.5, field02=44.5, field03='Bob',
>     field04='foo', ... , field60='2004-08-30', field61='2004-08-29'
>     WHERE id = 1234;
>
> Also of note is that the update is run about 10 times per day; we get 
> blocks of data from 10 different sources, so we pre-process the
> data and then update the table. We also run VACUUM FULL ANALYZE on a 
> nightly basis.
> Does anyone have some idea on how we can increase speed, either by 
> changing the updates, designing the database
> differently, etc, etc? This is currently a big problem for us.
> Other notables:
>   The UPDATE is run from a within a function: FOR rec IN SELECT 
> ...LOOP RETURN NEXT rec; UPDATE dataTable.....
>   Postgres 7.4.3
>   debian stable
>   2 GB RAM
>   80 DB IDE drive (we can't change it)
>   shared_buffers = 2048
>   sort_mem = 1024    max_fsm_pages = 40000
>   checkpoint_segments = 5
>   random_page_cost = 3
> Thanks
> Ron


From pgsql-performance-owner@postgresql.org  Tue Aug 31 15:18:24 2004
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Date: Tue, 31 Aug 2004 20:18:15 +0200
From: "Steinar H. Gunderson" 
To: pgsql-performance@postgresql.org
Subject: Re: Table UPDATE is too slow
Message-ID: <20040831181815.GB24253@uio.no>
References: <4134BF36.3000504@syscor.com>
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On Tue, Aug 31, 2004 at 11:11:02AM -0700, Ron St-Pierre wrote:
> We have a web based application with data that is updated daily. The 
> biggest bottleneck occurs when we try to update
> one of the tables. This table contains 58,000 rows and 62 columns, and 
> EVERY column is indexed.

That is usually a very bad idea; for every update, PostgreSQL has to update
62 indexes. Do you really do queries on all those 62 columns?

> A typical update is:
>   UPDATE dataTable SET field01=44.5, field02=44.5, field03='Bob',
>     field04='foo', ... , field60='2004-08-30', field61='2004-08-29'
>     WHERE id = 1234;

That looks like poor database normalization, really. Are you sure you don't
want to split this into multiple tables instead of having 62 columns?

> Other notables:
>   The UPDATE is run from a within a function: FOR rec IN SELECT ...LOOP 
> RETURN NEXT rec; UPDATE dataTable.....
>   Postgres 7.4.3
>   debian stable
>   2 GB RAM
>   80 DB IDE drive (we can't change it)

Are you doing all this in multiple transactions, or in a sngle one? Wrapping
the FOR loop in a transaction might help speed.

/* Steinar */
-- 
Homepage: http://www.sesse.net/

From pgsql-performance-owner@postgresql.org  Tue Aug 31 15:22:20 2004
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Date: Tue, 31 Aug 2004 11:23:39 -0700
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Thomas F. O'Connell wrote:

> What is the datatype of the id column?
>
The id column is INTEGER.

Ron


From pgsql-performance-owner@postgresql.org  Tue Aug 31 15:34:22 2004
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Steinar H. Gunderson wrote:

>On Tue, Aug 31, 2004 at 11:11:02AM -0700, Ron St-Pierre wrote:
>  
>
>>We have a web based application with data that is updated daily. The 
>>biggest bottleneck occurs when we try to update
>>one of the tables. This table contains 58,000 rows and 62 columns, and 
>>EVERY column is indexed.
>>    
>>
>
>That is usually a very bad idea; for every update, PostgreSQL has to update
>62 indexes. Do you really do queries on all those 62 columns?
>  
>
Yes, I know that it's not a very good idea, however queries are allowed 
against all of those columns. One option is to disable some or all of the
indexes when we update, run the update, and recreate the indexes, 
however it may slow down user queries. Because there are so many indexes,
it is time consuming to recreate them after the update.

>  
>
>>A typical update is:
>>  UPDATE dataTable SET field01=44.5, field02=44.5, field03='Bob',
>>    field04='foo', ... , field60='2004-08-30', field61='2004-08-29'
>>    WHERE id = 1234;
>>    
>>
>
>That looks like poor database normalization, really. Are you sure you don't
>want to split this into multiple tables instead of having 62 columns?
>
No, it is properly normalized. The data in this table is stock 
fundamentals, stuff like 52 week high, ex-dividend date, etc, etc.

>
>  
>
>>Other notables:
>>  The UPDATE is run from a within a function: FOR rec IN SELECT ...LOOP 
>>RETURN NEXT rec; UPDATE dataTable.....
>>  Postgres 7.4.3
>>  debian stable
>>  2 GB RAM
>>  80 DB IDE drive (we can't change it)
>>    
>>
>
>Are you doing all this in multiple transactions, or in a sngle one? Wrapping
>the FOR loop in a transaction might help speed.
>
We're doing it in multiple transactions within the function. Could we do 
something like this?:

....
BEGIN
  FOR rec IN SELECT field01, field02, ... FROM otherTable LOOP 
  RETURN NEXT rec;
  UPDATE dataTable SET field01=rec.field01, field02=rec.field02, rec.field03=field03, ...
    WHERE id = rec.id;
COMMIT;
....


If we can do it this way, are there any other gotcha's we should be 
aware of?


Ron


From pgsql-performance-owner@postgresql.org  Tue Aug 31 15:46:24 2004
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Date: Tue, 31 Aug 2004 13:46:19 -0500
From: Frank Wiles 
To: Ron St-Pierre 
Cc: pgsql-performance@postgresql.org
Subject: Re: Table UPDATE is too slow
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On Tue, 31 Aug 2004 11:11:02 -0700
Ron St-Pierre  wrote:


>    Postgres 7.4.3
>    debian stable
>    2 GB RAM
>    80 DB IDE drive (we can't change it)
>  
>    shared_buffers = 2048
>    sort_mem = 1024  
>    max_fsm_pages = 40000
>    checkpoint_segments = 5
>    random_page_cost = 3

  I agree with all of the follow ups that having indexes on every 
  column is a bad idea.  I would remove the indexes from the
  least searched upon 10-20 columns, as I'm sure this will help
  your performance.

  You mention that not having indexes on some of the columns because it
  "may slow down user queries".  I think you should investigate this and
  make sure they are necessary.  I've seen many an application, with far
  more rows than you're dealing with, only need 1 or 2 indexes, even
  when all (or most) columns could be searched. 

  Also, you should consider increasing your shared_buffers and probably
  your sort memory a touch as well. This will help your overall
  performance. 

 ---------------------------------
   Frank Wiles 
   http://www.wiles.org
 ---------------------------------


From pgsql-performance-owner@postgresql.org  Tue Aug 31 15:48:53 2004
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From: "Steinar H. Gunderson" 
To: pgsql-performance@postgresql.org
Subject: Re: Table UPDATE is too slow
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On Tue, Aug 31, 2004 at 11:35:38AM -0700, Ron St-Pierre wrote:
> We're doing it in multiple transactions within the function. Could we do 
> something like this?:
> 
> ....
> BEGIN
>  FOR rec IN SELECT field01, field02, ... FROM otherTable LOOP 
>  RETURN NEXT rec;
>  UPDATE dataTable SET field01=rec.field01, field02=rec.field02, 
>  rec.field03=field03, ...
>    WHERE id = rec.id;
> COMMIT;
> ....
> 
> 
> If we can do it this way, are there any other gotcha's we should be 
> aware of?

AFAIK you should be able to do this, yes (although I have no experience with
PL/SQL); I'm not sure how much it buys you, but you might want to test it, at
least.

/* Steinar */
-- 
Homepage: http://www.sesse.net/

From pgsql-performance-owner@postgresql.org  Tue Aug 31 15:59:34 2004
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Date: Tue, 31 Aug 2004 20:59:11 +0200
From: Jean-Max Reymond 
Reply-To: Jean-Max Reymond 
To: pgsql-performance@postgresql.org
Subject: Optimizing a request
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hi,
I have the following structure in my base 7.4.2

CREATE TABLE "public"."article" (
 "art_id" INTEGER NOT NULL,
 "rub_id" INTEGER DEFAULT '0' NOT NULL,
 "art_titre" VARCHAR(100) DEFAULT '' NOT NULL,
 "art_texte" TEXT NOT NULL,
 "art_date" DATE NOT NULL,
 "aut_id" INTEGER,
 CONSTRAINT "article_pkey" PRIMARY KEY("art_id")
) WITH OIDS;

CREATE INDEX "article_art_date_index" ON "public"."article"
USING btree ("art_date");


CREATE INDEX "article_aut_id_index" ON "public"."article"
USING btree ("aut_id");


CREATE INDEX "article_rub_id_index" ON "public"."article"
USING btree ("rub_id");


CREATE INDEX "article_titre" ON "public"."article"
USING btree ("art_id", "art_titre");


CREATE TABLE "public"."auteur" (
 "aut_id" INTEGER NOT NULL,
 "aut_name" VARCHAR(100) DEFAULT '' NOT NULL,
 CONSTRAINT "auteur_pkey" PRIMARY KEY("aut_id")
) WITH OIDS;


CREATE TABLE "public"."rubrique" (
 "rub_id" INTEGER NOT NULL,
 "rub_titre" VARCHAR(100) DEFAULT '' NOT NULL,
 "rub_parent" INTEGER DEFAULT '0' NOT NULL,
 "rub_date" DATE,
 CONSTRAINT "rubrique_pkey" PRIMARY KEY("rub_id")
) WITH OIDS;

CREATE INDEX "rub_rub" ON "public"."rubrique"
USING btree ("rub_parent");

CREATE INDEX "rubrique_rub_date_index" ON "public"."rubrique"
USING btree ("rub_date");

CREATE INDEX "rubrique_rub_titre_index" ON "public"."rubrique"
USING btree ("rub_titre");

I want to optimize the following request and avoid the seq scan on the
table article (10000000 rows).



explain SELECT art_id, art_titre, art_texte, rub_titre
FROM article inner join rubrique on article.rub_id = rubrique.rub_id
where rub_parent = 8;

Hash Join  (cost=8.27..265637.59 rows=25 width=130)
  Hash Cond: ("outer".rub_id = "inner".rub_id)
  ->  Seq Scan on article  (cost=0.00..215629.00 rows=10000000 width=108)
  ->  Hash  (cost=8.26..8.26 rows=3 width=22)
        ->  Index Scan using rubrique_parent on rubrique 
(cost=0.00..8.26 rows=3 width=22)
              Index Cond: (rub_parent = 8)


thanks for your answers,

-- 
Jean-Max Reymond
CKR Solutions
http://www.ckr-solutions.com

From pgsql-performance-owner@postgresql.org  Tue Aug 31 16:00:08 2004
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Reply-To: 
From: "Matt Clark" 
To: "'Ron St-Pierre'" ,
	"'Steinar H. Gunderson'" ,
	
Subject: Re: Table UPDATE is too slow
Date: Tue, 31 Aug 2004 19:59:55 +0100
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> >That looks like poor database normalization, really. Are you=20
> sure you=20
> >don't want to split this into multiple tables instead of having 62=20
> >columns?
> >
> No, it is properly normalized. The data in this table is stock=20
> fundamentals, stuff like 52 week high, ex-dividend date, etc, etc.

Hmm, the two examples you gave there are actually ripe for breaking out into
another table.  It's not quite 'normalisation', but if you have data that
changes very rarely, why not group it into a separate table?  You could have
the highly volatile data in one table, the semi-volatile stuff in another,
and the pretty static stuff in a third.  Looked at another way, if you have
sets of fields that tend to change together, group them into tables
together.  That way you will radically reduce the number of indexes that are
affected by each update.

But as someone else pointed out, you should at the very least wrap your
updates in a big transaction.

M


From pgsql-performance-owner@postgresql.org  Tue Aug 31 16:01:02 2004
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> thanks for the quick answer! My db driver is the native MS ADO, and
from
> Delphi i use the AODExpress components which are wrapper classes to
reach
> the ActiveX components from delhpi. The strange behaviour of that
query
> is,
> that all other queries executed in this environment are running fast,
> except
> this one. First there was any index on that table (appr. 40.000
records),
> and i thought that maybe this is my problem. Then i made this index,
but
> this hasn't solved my problem.
> Now i think that maybe the odbc driver makes something with my query?
Can
> this happen?

Possible.  I would turn on statement logging on the server and make sure
the query is the way you wrote it in the app.  The driver might be doing
something like pulling all the data and attempting a client side filter.
Otherwise you may be looking at a casting problem of some sort.

To turn on logging, set statement log to 'all' in your postgresql.conf
file.  You may need to start the server manually so you can determine
where the log goes (logging to terminal is often the easiest to work
with).

If you are writing Delphi applications, you really should check out
Zeos.  It utilizes native drivers to connect to the database...it's
really, really fast and supports all the Delphi controls (and free!).

Merlin

From pgsql-performance-owner@postgresql.org  Tue Aug 31 16:33:07 2004
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Ron St-Pierre wrote:
> Yes, I know that it's not a very good idea, however queries are allowed 
> against all of those columns. One option is to disable some or all of the
> indexes when we update, run the update, and recreate the indexes, 
> however it may slow down user queries. Because there are so many indexes,
> it is time consuming to recreate them after the update.

Just because a query can run against any column does not mean all 
columns should be indexed. Take a good look at the column types and 
their value distribution.

Let's say I have a table of addresses but every address I collect is in 
the 94116 zip code. That would mean indexes on city, state and zip are 
not only useless but could decrease performance.

Also, if a search always includes a unique key (or a column with highly 
unique values), eliminating the other indexes would force the planner to 
always use that index first.

From pgsql-performance-owner@postgresql.org  Tue Aug 31 16:15:04 2004
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From: Josh Berkus 
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Organization: Aglio Database Solutions
To: Jean-Max Reymond 
Subject: Re: Optimizing a request
Date: Tue, 31 Aug 2004 12:15:40 -0700
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Jean,

> I have the following structure in my base 7.4.2

Upgrade to 7.4.5.  The version you're using has several known issues with data 
restore in the event of system failure.

> Hash Join  (cost=8.27..265637.59 rows=25 width=130)
>   Hash Cond: ("outer".rub_id = "inner".rub_id)
>   ->  Seq Scan on article  (cost=0.00..215629.00 rows=10000000 width=108)
>   ->  Hash  (cost=8.26..8.26 rows=3 width=22)
>         ->  Index Scan using rubrique_parent on rubrique
> (cost=0.00..8.26 rows=3 width=22)
>               Index Cond: (rub_parent = 8)

Those look suspiciously like stock estimates.  When was the last time you ran 
ANALYZE?


-- 
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Tue Aug 31 16:19:17 2004
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Date: Tue, 31 Aug 2004 21:19:09 +0200
From: Jean-Max Reymond 
Reply-To: Jean-Max Reymond 
To: josh@agliodbs.com
Subject: Re: Optimizing a request
Cc: pgsql-performance@postgresql.org
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On Tue, 31 Aug 2004 12:15:40 -0700, Josh Berkus  wrote:

> Those look suspiciously like stock estimates.  When was the last time you ran
> ANALYZE?

the vacuum analyze ran just before the explain

-- 
Jean-Max Reymond
CKR Solutions
http://www.ckr-solutions.com

From pgsql-performance-owner@postgresql.org  Tue Aug 31 16:21:49 2004
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From: "Gary Doades" 
To: pgsql-performance@postgresql.org
Date: Tue, 31 Aug 2004 20:21:49 +0100
MIME-Version: 1.0
Subject: Re: Optimizing a request
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On 31 Aug 2004 at 20:59, Jean-Max Reymond wrote:

> hi,
> 
> I want to optimize the following request and avoid the seq scan on the
> table article (10000000 rows).
> 
> explain SELECT art_id, art_titre, art_texte, rub_titre
> FROM article inner join rubrique on article.rub_id = rubrique.rub_id
> where rub_parent = 8;
> 
> Hash Join  (cost=8.27..265637.59 rows=25 width=130)
>   Hash Cond: ("outer".rub_id = "inner".rub_id)
>   ->  Seq Scan on article  (cost=0.00..215629.00 rows=10000000 width=108)
>   ->  Hash  (cost=8.26..8.26 rows=3 width=22)
>         ->  Index Scan using rubrique_parent on rubrique 
> (cost=0.00..8.26 rows=3 width=22)
>               Index Cond: (rub_parent = 8)
> 
> 
> thanks for your answers,
> 
> -- 

Have you run ANALYZE on this database after creating the indexes or 
loading the data?

What percentage of rows in the "article" table are likely to match the 
keys selected from the "rubrique" table?

If it is likely to fetch a high proportion of the rows from article then it 
may be best that a seq scan is performed.

What are your non-default postgresql.conf settings? It may be better to 
increase the default_statistics_target (to say 100 to 
200) before running ANALYZE and then re-run the 
query.

Cheers,
Gary.


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On 31 Aug 2004 at 20:59, Jean-Max Reymond wrote:







> hi,


> 


> I want to optimize the following request and avoid the seq scan on the


> table article (10000000 rows).


> 


> explain SELECT art_id, art_titre, art_texte, rub_titre


> FROM article inner join rubrique on article.rub_id = rubrique.rub_id


> where rub_parent = 8;


> 


> Hash Join  (cost=8.27..265637.59 rows=25 width=130)


>   Hash Cond: ("outer".rub_id = "inner".rub_id)


>   ->  Seq Scan on article  (cost=0.00..215629.00 rows=10000000 
width=108)


>   ->  Hash  (cost=8.26..8.26 rows=3 width=22)


>         ->  Index Scan using rubrique_parent 
on rubrique 


> (cost=0.00..8.26 rows=3 width=22)


>               Index 
Cond: (rub_parent = 8)


> 


> 


> thanks for your answers,


> 


> -- 





Have you run ANALYZE on this database after creating the indexes or 
loading the data?







What percentage of rows in the "article" table are likely to match the 
keys selected from the "rubrique" table?







If it is likely to fetch a high proportion of the rows from article then it 
may be best that a seq scan is performed.







What are your non-default postgresql.conf settings? It may be better to 
increase the default_statistics_target (to say 100 to 
200) before running ANALYZE and then re-run the 
query.







Cheers,


Gary.






--Alt-Boundary-12526.78604236--

From pgsql-performance-owner@postgresql.org  Tue Aug 31 16:43:05 2004
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From: Jean-Max Reymond 
Reply-To: Jean-Max Reymond 
To: Gary Doades 
Subject: Re: Optimizing a request
Cc: pgsql-performance@postgresql.org
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----- Original Message -----
From: Gary Doades 
Date: Tue, 31 Aug 2004 20:21:49 +0100
Subject: Re: [PERFORM] Optimizing a request
To: pgsql-performance@postgresql.org

 

> Have you run ANALYZE on this database after creating the indexes or loading the data? 
 
the indexes are created and the data loaded and then, I run vacuum analyze.

>What percentage of rows in the "article" table are likely to match
the keys selected from  the "rubrique" table?
 
only 1 record.

If it is likely to fetch a high proportion of the rows from article
then it may be best that a seq scan is performed.
 
What are your non-default postgresql.conf settings? It may be better
to increase the default_statistics_target (to say 100 to 200) before
running ANALYZE and then re-run the query.
 
yes,  default_statistics_target is set to the default_value.
I have just increased  shared_buffers and effective_cache_size to give
advantage of 1 Mb RAM
 



-- 
Jean-Max Reymond
CKR Solutions
http://www.ckr-solutions.com

From pgsql-performance-owner@postgresql.org  Tue Aug 31 17:14:06 2004
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To: Jean-Max Reymond 
Cc: pgsql-performance@postgresql.org
Subject: Re: Optimizing a request 
In-reply-to: <4b09a0c0408311159fa91802@mail.gmail.com> 
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Comments: In-reply-to Jean-Max Reymond 
	message dated "Tue, 31 Aug 2004 20:59:11 +0200"
Date: Tue, 31 Aug 2004 16:13:58 -0400
Message-ID: <14630.1093983238@sss.pgh.pa.us>
From: Tom Lane 
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Jean-Max Reymond  writes:
> explain SELECT art_id, art_titre, art_texte, rub_titre
> FROM article inner join rubrique on article.rub_id = rubrique.rub_id
> where rub_parent = 8;

> Hash Join  (cost=8.27..265637.59 rows=25 width=130)
>   Hash Cond: ("outer".rub_id = "inner".rub_id)
>   ->  Seq Scan on article  (cost=0.00..215629.00 rows=10000000 width=108)
>   ->  Hash  (cost=8.26..8.26 rows=3 width=22)
>         ->  Index Scan using rubrique_parent on rubrique 
> (cost=0.00..8.26 rows=3 width=22)
>               Index Cond: (rub_parent = 8)

That seems like a very strange plan choice given those estimated row
counts.  I'd have expected it to use a nestloop with inner index scan
on article_rub_id_index.  You haven't done anything odd like disable
nestloop, have you?

What plan do you get if you turn off enable_hashjoin?  (If it's a merge
join, then turn off enable_mergejoin and try again.)  Also, could we see
EXPLAIN ANALYZE not just EXPLAIN output for all these cases?

			regards, tom lane

From pgsql-performance-owner@postgresql.org  Tue Aug 31 17:16:42 2004
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From: "Gary Doades" 
To: pgsql-performance@postgresql.org
Date: Tue, 31 Aug 2004 21:16:46 +0100
MIME-Version: 1.0
Subject: Re: Optimizing a request
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On 31 Aug 2004 at 21:42, Jean-Max Reymond wrote:

> ----- Original Message -----
> From: Gary Doades 
> Date: Tue, 31 Aug 2004 20:21:49 +0100
> Subject: Re: [PERFORM] Optimizing a request
> To: pgsql-performance@postgresql.org
> 
>  
> 
> > Have you run ANALYZE on this database after creating the indexes or loading the data? 
>  
> the indexes are created and the data loaded and then, I run vacuum analyze.
> 
> >What percentage of rows in the "article" table are likely to match
> the keys selected from  the "rubrique" table?
>  
> only 1 record.
> 
> If it is likely to fetch a high proportion of the rows from article
> then it may be best that a seq scan is performed.
>  
> What are your non-default postgresql.conf settings? It may be better
> to increase the default_statistics_target (to say 100 to 200) before
> running ANALYZE and then re-run the query.
>  
> yes,  default_statistics_target is set to the default_value.
> I have just increased  shared_buffers and effective_cache_size to give
> advantage of 1 Mb RAM
>  

I can only presume you mean 1 GB RAM. What exactly are your 
settings for shared buffers and effective_cache_size?

Can you increase default_statistics_target and re-test? It is possible 
that with such a large table that the distribution of values is skewed and 
postgres does not realise that an index scan would be better.

It seems very odd otherwise that only on row out of 10,000,000 could 
match and postgres does not realise this.

Can you post an explain analyse (not just explain) for this query?

Cheers,
Gary.


From pgsql-performance-owner@postgresql.org  Tue Aug 31 17:24:58 2004
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Date: Tue, 31 Aug 2004 22:24:51 +0200
From: Jean-Max Reymond 
Reply-To: Jean-Max Reymond 
To: Gary Doades 
Subject: Re: Optimizing a request
Cc: pgsql-performance@postgresql.org
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On Tue, 31 Aug 2004 21:16:46 +0100, Gary Doades  wrote:

> I can only presume you mean 1 GB RAM. What exactly are your
> settings for shared buffers and effective_cache_size?

for 1 GB RAM,
shared_buffers = 65536
effective_cache_size = 16384 

> 
> Can you increase default_statistics_target and re-test? It is possible
> that with such a large table that the distribution of values is skewed and
> postgres does not realise that an index scan would be better.

OK, tomorrow, I'll try with the new value of default_statistics_target

> It seems very odd otherwise that only on row out of 10,000,000 could
> match and postgres does not realise this.
> 
> Can you post an explain analyse (not just explain) for this query?

yes, of course


-- 
Jean-Max Reymond
CKR Solutions
http://www.ckr-solutions.com

From pgsql-performance-owner@postgresql.org  Tue Aug 31 17:26:14 2004
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Reply-To: Jean-Max Reymond 
To: Tom Lane 
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On Tue, 31 Aug 2004 16:13:58 -0400, Tom Lane  wrote:

> That seems like a very strange plan choice given those estimated row
> counts.  I'd have expected it to use a nestloop with inner index scan
> on article_rub_id_index.  You haven't done anything odd like disable
> nestloop, have you?
> 

no optimizer disabled.

> What plan do you get if you turn off enable_hashjoin?  (If it's a merge
> join, then turn off enable_mergejoin and try again.)  Also, could we see
> EXPLAIN ANALYZE not just EXPLAIN output for all these cases?
> 
>                         regards, tom lane
> 

OK, TOM Thanks for your help

-- 
Jean-Max Reymond
CKR Solutions
http://www.ckr-solutions.com

From pgsql-performance-owner@postgresql.org  Tue Aug 31 17:31:42 2004
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From: "Gary Doades" 
To: pgsql-performance@postgresql.org
Date: Tue, 31 Aug 2004 21:31:44 +0100
MIME-Version: 1.0
Subject: Re: Optimizing a request
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On 31 Aug 2004 at 22:24, Jean-Max Reymond wrote:

> On Tue, 31 Aug 2004 21:16:46 +0100, Gary Doades  wrote:
> 
> > I can only presume you mean 1 GB RAM. What exactly are your
> > settings for shared buffers and effective_cache_size?
> 
> for 1 GB RAM,
> shared_buffers = 65536
> effective_cache_size = 16384 

This seems like the wrong way round also.

You might try:

shared_buffers = 10000
effective_cache_size = 60000

Cheers,
Gary.


From pgsql-performance-owner@postgresql.org  Tue Aug 31 17:41:25 2004
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From: =?iso-8859-1?q?Herv=E9_Piedvache?= 
To: Jean-Max Reymond 
Subject: Re: Optimizing a request
Date: Tue, 31 Aug 2004 22:41:15 +0200
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Hi,

Le Mardi 31 Ao=FBt 2004 20:59, Jean-Max Reymond a =E9crit :
> explain SELECT art_id, art_titre, art_texte, rub_titre
> FROM article inner join rubrique on article.rub_id =3D rubrique.rub_id
> where rub_parent =3D 8;
>
> Hash Join  (cost=3D8.27..265637.59 rows=3D25 width=3D130)
>   Hash Cond: ("outer".rub_id =3D "inner".rub_id)
>   ->  Seq Scan on article  (cost=3D0.00..215629.00 rows=3D10000000 width=
=3D108)
>   ->  Hash  (cost=3D8.26..8.26 rows=3D3 width=3D22)
>         ->  Index Scan using rubrique_parent on rubrique
> (cost=3D0.00..8.26 rows=3D3 width=3D22)
>               Index Cond: (rub_parent =3D 8)
>

What are the values in rub_parent ... is their many disparity in the values=
 ?
May be you have most of the value set to 8 ... and may be the optimizer thi=
nk=20
a seq scan is better than the use of an index ...

Could you do a simple :
SELECT rub_parent, count(rub_id)
   FROM rubrique=20
 GROUP BY rub_parent;

Just to see the disparity of the values ...

regards,
--=20
Bill Footcow


From pgsql-performance-owner@postgresql.org  Tue Aug 31 18:20:53 2004
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Hello,

Is context switching problem resolved in 8.0?

Can I drop in another Xeon?

Thanks,
Jelle


On Wed, 2 Jun 2004, Josh Berkus wrote:

> Folks,
> 
> I've been testing varying SPINS_PER_DELAY in a client's installation of 
> PostgreSQL against a copy of a production database, to test varying this 
> statistic as a way of fixing the issue.   
> 
> It does not seem to work.
> 
> I've tested all of the following graduated levels:
> 
> 100 (the original)
> 250
> 500
> 1000
> 2000
> 5000
> 10000
> 20000
> 30000
> 50000
> 
> None of these quantities seem to make any difference at all in the number of 
> context switches -- neither down nor up.   Seems to me like this is a dead 
> end.   Does anyone have test results that show otherwise?
> 
> 

-- 

http://www.jibjab.com


From pgsql-performance-owner@postgresql.org  Tue Aug 31 18:50:21 2004
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From: "Jim C. Nasby" 
To: "J. Andrew Rogers" 
Cc: Bruce Momjian ,
	pgsql-performance@postgresql.org, mischa.sandberg@telus.net
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
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On Thu, Aug 26, 2004 at 12:04:48PM -0700, J. Andrew Rogers wrote:
> The major caveat to having tables of this type is that you can only have
> a primary key index.  No other indexes are possible because the "heap"
> constantly undergoes local reorganizations if you have a lot of write
> traffic, the same kind of reorganization you would normally expect in a
> BTree index.

This isn't true, at least in 9i. You can create whatever indexes you
want on an index-organized table. I believe that the index stores the PK
value instead of the ROWID.
-- 
Jim C. Nasby, Database Consultant               decibel@decibel.org 
Give your computer some brain candy! www.distributed.net Team #1828

Windows: "Where do you want to go today?"
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From pgsql-performance-owner@postgresql.org  Tue Aug 31 19:02:28 2004
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Jellej,

> Is context switching problem resolved in 8.0?
>
> Can I drop in another Xeon?

Nope, not solved yet.   However, it only affects certain data access patterns.  
So don't use it as a reason not to go multi-processor.

-- 
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco

From pgsql-performance-owner@postgresql.org  Tue Aug 31 19:05:07 2004
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From: "Jim C. Nasby" 
To: Greg Stark 
Cc: Bruce Momjian ,
	"J. Andrew Rogers" ,
	Magnus Hagander ,
	pgsql-performance@postgresql.org, mischa.sandberg@telus.net
Subject: Re: Equivalent praxis to CLUSTERED INDEX?
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On Thu, Aug 26, 2004 at 11:39:42PM -0400, Greg Stark wrote:
> 
> Bruce Momjian  writes:
> 
> > Updated TODO item:
> > 
> >         o Automatically maintain clustering on a table
> > 
> >         This would require some background daemon to maintain clustering
> >         during periods of low usage. It might also require tables to be only
> >         paritally filled for easier reorganization.  It also might require
> >         creating a merged heap/index data file so an index lookup would
> >         automatically access the heap data too.
> 
> Fwiw, I would say the first "would" is also a "might". None of the previous
> discussions here presumed a maintenance daemon. The discussions before talked
> about a mechanism to try to place new tuples as close as possible to the
> proper index position.
> 
> I would also suggest making some distinction between a cluster system similar
> to what we have now but improved to maintain the clustering continuously, and
> an actual index-organized-table where the tuples are actually only stored in a
> btree structure.
> 
> They're two different approaches to similar problems. But they might both be
> useful to have, and have markedly different implementation details.

There's a third approach that I think is worth considering. Half of the
benefit to clustered tables is limiting the number of pages you need to
access when scanning the primary key. The order of tuples in the pages
themselves isn't nearly as important as ordering of the pages. This
means you can get most of the benefit of an index-organized table just
by being careful about what page you place a tuple on. What I'm thinking
of is some means to ensure all the tuples on a page are within some PK
range, but not worrying about the exact order within the page since it's
relatively cheap to scan through the page in memory.

Some pros:
This would probably mean less change to the code that inserts tuples.

No need for a background daemon.

No need to create a new B-Tree table structure.

Ideally, there won't be need to move tuples around, which should mean
that current indexing code doesn't need to change.

Cons:
Need to have some way to deal with pages that fill up.

To gain full benefit some means of indicating what range of PK values
are on a page might be needed.

It's not as beneficial as a true IOT since you don't get the benefit of
storing your tuples inline with your B-Tree.

I'm sure there's a ton of things I'm missing, especially since I'm not
familiar with the postgresql code, but hopefully others can explore this
further.
-- 
Jim C. Nasby, Database Consultant               decibel@decibel.org 
Give your computer some brain candy! www.distributed.net Team #1828

Windows: "Where do you want to go today?"
Linux: "Where do you want to go tomorrow?"
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