diff --git "a/pgsql-performance.200301" "b/pgsql-performance.200301" new file mode 100644--- /dev/null +++ "b/pgsql-performance.200301" @@ -0,0 +1,32296 @@ +From pgsql-performance-owner@postgresql.org Tue Dec 31 22:32:13 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7A00C475DDA + for ; + Tue, 31 Dec 2002 22:32:12 -0500 (EST) +Received: from kaukau.mcs.vuw.ac.nz (kaukau.mcs.vuw.ac.nz [130.195.5.20]) + by postgresql.org (Postfix) with ESMTP id 0D13F475B47 + for ; + Tue, 31 Dec 2002 22:32:10 -0500 (EST) +Received: from devon.mcs.vuw.ac.nz (devon.mcs.vuw.ac.nz [130.195.5.109]) + by kaukau.mcs.vuw.ac.nz (8.12.6/8.12.6) with ESMTP id h013WDC6008506 + (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NOT) + for ; + Wed, 1 Jan 2003 16:32:13 +1300 (NZDT) +Received: from localhost (localhost [[UNIX: localhost]]) + by devon.mcs.vuw.ac.nz (8.11.6/8.11.1) id h013WAc05325 + for pgsql-performance@postgresql.org; + Wed, 1 Jan 2003 16:32:10 +1300 (NZDT) +Content-Type: text/plain; + charset="us-ascii" +From: Minghann Ho +To: pgsql-performance@postgresql.org +Subject: alter table TBL add constraint TBL_FK foreign key ... very slow +Date: Wed, 1 Jan 2003 16:32:10 +1300 +User-Agent: KMail/1.4.3 +MIME-Version: 1.0 +Content-Transfer-Encoding: 8bit +Message-Id: <200301011632.10433.Minghann.Ho@mcs.vuw.ac.nz> +X-Scanned-By: MIMEDefang 2.24 (www . roaringpenguin . com / mimedefang) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/229 +X-Sequence-Number: 645 + +Hi all, + +I've experienced very slow performance to add foreign key constraints using +ALTER TABLE ADD CONSTRAINT FOREIGN KEY ... + +After using COPY ... FROM to load the base tables, I started to build the +referential integrity between tables. +I have 3 tables: T1 (6 million records), T2 (1.5 million records) and T3 (0.8 +million records). +One of the RI - foreign key (T1 -> T2) constraint took about 70 hrs to build. +The other RI - foreign key (T1 -> T3) constraint took about 200 hrs and yet +completed!! (compound foreign key) + +I tried to use small subset of the tables of T2 and T3 to do the testing. +An estimation show that it need about 960 hrs to build the RI - foreign key +constraints on table T1 -> T3 !!! + +I've read in the archives that some people suffered slow performance of this +problem in Aug 2000, but there was no further information about the solution. + +Please anyone who has experience in this issues can give me some hint. + +Thanks + +Hans + +From pgsql-performance-owner@postgresql.org Tue Dec 31 22:38:09 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 650BB475DDA; Tue, 31 Dec 2002 22:38:06 -0500 (EST) +Received: from kaukau.mcs.vuw.ac.nz (kaukau.mcs.vuw.ac.nz [130.195.5.20]) + by postgresql.org (Postfix) with ESMTP + id 6696D475B47; Tue, 31 Dec 2002 22:38:05 -0500 (EST) +Received: from devon.mcs.vuw.ac.nz (devon.mcs.vuw.ac.nz [130.195.5.109]) + by kaukau.mcs.vuw.ac.nz (8.12.6/8.12.6) with ESMTP id h013c8C6008672 + (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NOT); + Wed, 1 Jan 2003 16:38:09 +1300 (NZDT) +Received: from localhost (localhost [[UNIX: localhost]]) + by devon.mcs.vuw.ac.nz (8.11.6/8.11.1) id h013c6R05361; + Wed, 1 Jan 2003 16:38:06 +1300 (NZDT) +Content-Type: text/plain; + charset="us-ascii" +From: Minghann Ho +To: pgsql-performance@postgresql.org, + pgsql-performance-owner@postgresql.org, pgsql-admin@postgresql.org +Subject: alter table TBL add constraint TBL_FK foreign key ... very slow +Date: Wed, 1 Jan 2003 16:38:06 +1300 +User-Agent: KMail/1.4.3 +MIME-Version: 1.0 +Content-Transfer-Encoding: 8bit +Message-Id: <200301011638.06045.mho@mcs.vuw.ac.nz> +X-Scanned-By: MIMEDefang 2.24 (www . roaringpenguin . com / mimedefang) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/230 +X-Sequence-Number: 646 + +Hi all, + +I've experienced very slow performance to add foreign key constraints using +ALTER TABLE ADD CONSTRAINT FOREIGN KEY ... + +After using COPY ... FROM to load the base tables, I started to build the +referential integrity between tables. +I have 3 tables: T1 (6 million records), T2 (1.5 million records) and T3 (0.8 +million records). +One of the RI - foreign key (T1 -> T2) constraint took about 70 hrs to build. +The other RI - foreign key (T1 -> T3) constraint took about 200 hrs and yet +completed!! (compound foreign key) + +I tried to use small subset of the tables of T2 and T3 to do the testing. +An estimation show that it need about 960 hrs to build the RI - foreign key +constraints on table T1 -> T3 !!! + +I've read in the archives that some people suffered slow performance of this +problem in Aug 2000, but there was no further information about the solution. + +Please anyone who has experience in this issues can give me some hint. + +Thanks + +Hans + +From pgsql-performance-owner@postgresql.org Tue Dec 31 22:38:50 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 34A00475E24 + for ; + Tue, 31 Dec 2002 22:38:50 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id C0BBF475B47 + for ; + Tue, 31 Dec 2002 22:38:49 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 35D42D610; Tue, 31 Dec 2002 19:38:54 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 2B8395C02; Tue, 31 Dec 2002 19:38:54 -0800 (PST) +Date: Tue, 31 Dec 2002 19:38:54 -0800 (PST) +From: Stephan Szabo +To: Minghann Ho +Cc: +Subject: Re: alter table TBL add constraint TBL_FK foreign key ... +In-Reply-To: <200301011632.10433.Minghann.Ho@mcs.vuw.ac.nz> +Message-ID: <20021231193351.U68640-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/231 +X-Sequence-Number: 647 + +On Wed, 1 Jan 2003, Minghann Ho wrote: + +> I've experienced very slow performance to add foreign key constraints using +> ALTER TABLE ADD CONSTRAINT FOREIGN KEY ... +> +> After using COPY ... FROM to load the base tables, I started to build the +> referential integrity between tables. +> I have 3 tables: T1 (6 million records), T2 (1.5 million records) and T3 (0.8 +> million records). +> One of the RI - foreign key (T1 -> T2) constraint took about 70 hrs to build. +> The other RI - foreign key (T1 -> T3) constraint took about 200 hrs and yet +> completed!! (compound foreign key) +> +> I tried to use small subset of the tables of T2 and T3 to do the testing. +> An estimation show that it need about 960 hrs to build the RI - foreign key +> constraints on table T1 -> T3 !!! + +It's running the constraint check for each row in the foreign key table. +Rather than using a call to the function and a select for each row, it +could probably be done in a single select with a not exists subselect, but +that hasn't been done yet. There's also been talk about allowing some +mechanism to allow the avoidance of the create time check, but I don't +think any concensus was reached. + + +From pgsql-performance-owner@postgresql.org Wed Jan 1 03:14:42 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7F5D5475A3F + for ; + Wed, 1 Jan 2003 03:14:39 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id C22204753A1 + for ; + Wed, 1 Jan 2003 03:14:37 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030101081438.BSNC26808.lakemtao03.cox.net@[192.168.1.1]> + for ; + Wed, 1 Jan 2003 03:14:38 -0500 +Subject: Re: alter table TBL add constraint TBL_FK foreign key +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <200301011632.10433.Minghann.Ho@mcs.vuw.ac.nz> +References: <200301011632.10433.Minghann.Ho@mcs.vuw.ac.nz> +Content-Type: text/plain +Organization: +Message-Id: <1041408874.16580.39.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 01 Jan 2003 02:14:34 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/1 +X-Sequence-Number: 648 + +On Tue, 2002-12-31 at 21:32, Minghann Ho wrote: +> Hi all, +> +> I've experienced very slow performance to add foreign key constraints using +> ALTER TABLE ADD CONSTRAINT FOREIGN KEY ... +> +> After using COPY ... FROM to load the base tables, I started to build the +> referential integrity between tables. +> I have 3 tables: T1 (6 million records), T2 (1.5 million records) and T3 (0.8 +> million records). +> One of the RI - foreign key (T1 -> T2) constraint took about 70 hrs to build. +> The other RI - foreign key (T1 -> T3) constraint took about 200 hrs and yet +> completed!! (compound foreign key) +> +> I tried to use small subset of the tables of T2 and T3 to do the testing. +> An estimation show that it need about 960 hrs to build the RI - foreign key +> constraints on table T1 -> T3 !!! +> +> I've read in the archives that some people suffered slow performance of this +> problem in Aug 2000, but there was no further information about the solution. +> +> Please anyone who has experience in this issues can give me some hint. + +Silly question: Are T2 & T3 compound-key indexed on the relevant foreign +key fields (in the exact order that they are mentioned in the ADD +CONSTRAINT command)? Otherwise, for each record in T1, it is scanning +T2 1.5M times (9E12 record reads!), with a similar formula for T1->T3. + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 04:55:39 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 69664475E97 + for ; + Thu, 16 Jan 2003 04:55:36 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id A5999475D93 + for ; + Thu, 16 Jan 2003 04:55:35 -0500 (EST) +Received: from klaster.net (pe26.krakow.cvx.ppp.tpnet.pl [213.76.40.26]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP + id 512FB2B84B; Thu, 16 Jan 2003 10:52:22 +0100 (CET) +Message-ID: <3E12BBEA.5020105@klaster.net> +Date: Wed, 01 Jan 2003 10:59:06 +0100 +From: Tomasz Myrta +User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; + rv:1.2b) Gecko/20021016 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Roman Fail +Cc: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/136 +X-Sequence-Number: 783 + +Roman Fail wrote: +> The same result columns and JOINS are performed all day with variations on the WHERE clause; +Are there any where clauses which all of theses variation have? +If yes - query can be reordered to contain explicit joins for these clauses and +to let Postgres to find best solution for other joins. + +I know, it is not best solution, but sometimes I prefer finding best join order by myself. +I create then several views returning the same values, but manualy ordered for specific where clauses. + +Tomasz Myrta + + + +From pgsql-performance-owner@postgresql.org Wed Jan 1 16:01:15 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 58094476065 + for ; + Wed, 1 Jan 2003 16:01:14 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 9D2AF475F2B + for ; + Wed, 1 Jan 2003 16:01:13 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h01L1Ed0008338; + Wed, 1 Jan 2003 16:01:14 -0500 (EST) +To: "Neil Conway" +Cc: mt_pgsql@yahoo.com, pgsql-performance@postgresql.org +Subject: Re: preliminary testing, two very slow situations... +In-reply-to: <2973.24.112.166.30.1041375927.squirrel@mailbox.samurai.com> +References: <20021231221435.26755.qmail@web14810.mail.yahoo.com> + <2973.24.112.166.30.1041375927.squirrel@mailbox.samurai.com> +Comments: In-reply-to "Neil Conway" + message dated "Tue, 31 Dec 2002 18:05:27 -0500" +Date: Wed, 01 Jan 2003 16:01:13 -0500 +Message-ID: <8337.1041454873@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/2 +X-Sequence-Number: 649 + +"Neil Conway" writes: +> Michael Teter said: +>> Now I'm trying to evaluate it as a possible +>> replacement for MS SQL Server. + +> What version of PostgreSQL are you using? +> [suggestions for tuning] + +The only reason I can think of for COPY to be as slow as Michael is +describing is if it's checking foreign-key constraints (and even then +it'd have to be using very inefficient plans for the check queries). +So we should ask not only about the PG version, but also about the +exact table declarations involved. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 2 09:57:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 715F54761C5 + for ; + Thu, 2 Jan 2003 09:57:16 -0500 (EST) +Received: from ll.mit.edu (LLMAIL.LL.MIT.EDU [129.55.12.40]) + by postgresql.org (Postfix) with ESMTP id ADF324760CE + for ; + Thu, 2 Jan 2003 09:57:15 -0500 (EST) +Received: (from smtp@localhost) by ll.mit.edu (8.11.3/8.8.8) id h02EvFY20211 + for ; + Thu, 2 Jan 2003 09:57:15 -0500 (EST) +Received: from sty.llan.ll.mit.edu( ), claiming to be "sty.llan" + via SMTP by llpost, id smtpdAAAgEay9G; Thu Jan 2 09:56:57 2003 +Date: Thu, 2 Jan 2003 10:57:27 -0500 +From: george young +To: pgsql-performance@postgresql.org +Subject: Re: preliminary testing, two very slow situations... +Message-Id: <20030102105727.4fa0bf7e.gry@ll.mit.edu> +Reply-To: gry@ll.mit.edu +Organization: MIT Lincoln Laboratory +X-Mailer: Sylpheed version 0.8.5 (GTK+ 1.2.10; i686-pc-linux-gnu) +Mime-Version: 1.0 +Content-Type: text/plain; charset=US-ASCII +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/3 +X-Sequence-Number: 650 + +On Tue, 31 Dec 2002 14:14:34 -0800 (PST) +Michael Teter wrote: +> I've used PostgreSQL in the past on a small project, +> and I thought it was great. +> +> Now I'm trying to evaluate it as a possible +> replacement for MS SQL Server. +> +> I have two issues: +> +> 1. I have a homegrown Java migration tool I wrote that +> seems to work reasonably well, but I'm hoping to +> understand how to improve its performance. +> +> 2. After migrating, I found pg_dump to be plenty +> quick, but psql < (to completely reload the database) +> to be very very slow during the COPY stage. + +I've found that "psql -f myfile mydb" is Much faster than +"psql mydb Now for more detail. On problem 1., I have autocommit +> off, and I'm doing PreparedStatement.addBatch() and +> executeBatch(), and eventually, commit. +> +> I've been playing with the amount of rows I do before +> executeBatch(), and I seem to do best with 20,000 to +> 50,000 rows in a batch. Some background: this is +> RedHat8.0 with all the latest RedHat patches, 1GB +> RAMBUS RAM, 2GHz P4, 40GB 7200RPM HD. Watching +> gkrellm and top, I see a good bit of CPU use by +> postmaster duing the addBatch()es, but then when +> executeBatch() comes, CPU goes almost totally idle, +> and disk starts churning. Somehow it seems the disk +> isn't being utilized to the fullest, but I'm just +> guessing. +> +> I'm wondering if there's some postmaster tuning I +> might do to improve this. +> +> Then on problem 2., a pg_dump of the database takes +> about 3 minutes, and creates a file of 192MB in size. +> Then I create testdb and do psql -e testdb +> section. So far it's been running for 45 minutes, +> mostly on one table (the biggest table, which has +> 1,090,000 rows or so). During this time, CPU use is +> very low, and there's no net or lo traffic. +> +> In contrast, using MSSQL's backup and restore +> facilities, it takes about 15 second on a previous +> generation box (with SCSI though) to backup, and 45 +> seconds to a minute to restore. +> +> Suggestions? +> +> Thanks, +> MT +> +> __________________________________________________ +> Do you Yahoo!? +> Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +> http://mailplus.yahoo.com +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 4: Don't 'kill -9' the postmaster +> + + +-- + I cannot think why the whole bed of the ocean is + not one solid mass of oysters, so prolific they seem. Ah, + I am wandering! Strange how the brain controls the brain! + -- Sherlock Holmes in "The Dying Detective" + + +-- + I cannot think why the whole bed of the ocean is + not one solid mass of oysters, so prolific they seem. Ah, + I am wandering! Strange how the brain controls the brain! + -- Sherlock Holmes in "The Dying Detective" + +From pgsql-performance-owner@postgresql.org Thu Jan 2 12:40:04 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5F71247607B + for ; + Thu, 2 Jan 2003 12:40:03 -0500 (EST) +Received: from local.iboats.com (local.iboats.com [209.63.105.131]) + by postgresql.org (Postfix) with SMTP id 9C687475FB0 + for ; + Thu, 2 Jan 2003 12:40:02 -0500 (EST) +Received: (qmail 27751 invoked by uid 82); 2 Jan 2003 10:39:40 -0700 +Received: from nw@codon.com by local.iboats.com by uid 81 with + qmail-scanner-1.14 ( Clear:. + Processed in 0.029668 secs); 02 Jan 2003 17:39:40 -0000 +Received: from unknown (HELO WEASEL) (209.63.105.136) + by 0 with SMTP; 2 Jan 2003 10:39:40 -0700 +Message-ID: <008701c2b286$4c9c2ae0$88693fd1@WEASEL> +From: "Steve Wolfe" +To: +Subject: Question on hardware & server capacity +Date: Thu, 2 Jan 2003 10:42:05 -0700 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 6.00.2800.1106 +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/4 +X-Sequence-Number: 651 + + + Well, our current database server is getting tremendously loaded, and +right now there isn't a clear-cut choice as to an upgrade path - at least +not within the commodity hardware market. + + The machine is a dual AthlonMP 2000, with 2 gigs of RAM. the loads on +the machine are getting out of hand, and performance is noticeably slowed. +'top' shows the CPU's as being anywhere from 30% to 50% idle, with (on +average) 5-10 postmasters in the "non-idle" state. 'vmstat' shows bi/bo +pegged at zero (copious quantities of disk cache, fsync turned off), +interrupts fluctuating between 200 and 1,000 per second (avg. is approx +400), context switches between 1300 and 4500 (avg. is approx 2300). I +logged some queries, and found that in an average second, the machine +forks off 10 new backends, and responds to 50 selects and 3 updates. + + My feelings are that the machine is being swamped by both the number of +context switches and the I/O, most likely the memory bandwidth. I'm +working on implementing some connection pooling to reduce the number of +new backends forked off, but there's not much I can do about the sheer +volume (or cost) of queries. + + Now, if quad-Hammers were here, I'd simply throw hardware at it. +Unfortunately, they're not. So far, about the only commodity-level answer +I can think of would be a dual P4 Xeon, with the 533 MHz bus, and +dual-channel DDR memory. That would give each processor approximately +double the memory bandwidth over what we're currently running. + + I'm fairly sure that would at least help lower the load, but I'm not +sure by how much. If anyone has run testing under similar platforms, I'd +love to hear of the performance difference. If this is going to chop the +loads in half, I'll do it. If it's only going to improve it by 10% or so, +I'm not going to waste the money. + +Steve + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 14:44:37 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 70F6E476C8E + for ; + Thu, 2 Jan 2003 14:44:34 -0500 (EST) +Received: from ns1.gnf.org (ns1.gnf.org [63.196.132.67]) + by postgresql.org (Postfix) with ESMTP id AF3A4476C19 + for ; + Thu, 2 Jan 2003 14:42:02 -0500 (EST) +Received: from EXCHCLUSTER01.lj.gnf.org (exch01.lj.gnf.org [172.25.10.19]) + by ns1.gnf.org (8.12.3/8.12.3) with ESMTP id h02JfxMf019791 + for ; + Thu, 2 Jan 2003 11:42:00 -0800 (PST) (envelope-from hlapp@gmx.net) +Received: from gmx.net ([172.25.30.55]) by EXCHCLUSTER01.lj.gnf.org with + Microsoft SMTPSVC(5.0.2195.5329); Thu, 2 Jan 2003 11:42:02 -0800 +Date: Thu, 2 Jan 2003 11:42:02 -0800 +Mime-Version: 1.0 (Apple Message framework v551) +Content-Type: text/plain; charset=US-ASCII; format=flowed +Subject: join over 12 tables takes 3 secs to plan +From: Hilmar Lapp +To: pgsql-performance@postgresql.org +Content-Transfer-Encoding: 7bit +Message-Id: <43D30901-1E8A-11D7-9244-000393B4BFF6@gmx.net> +X-Mailer: Apple Mail (2.551) +X-OriginalArrivalTime: 02 Jan 2003 19:42:02.0605 (UTC) + FILETIME=[05BFB1D0:01C2B297] +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/5 +X-Sequence-Number: 652 + +I have a query generated by an application (not mine, but there's +nothing I can find that looks bad about the query itself) that takes an +excessive amount of time to return even though there are almost no rows +in the schema yet. 3 secs may not seem to be much, but the query is run +by a web-application for a page you have to go through quite +frequently, and it appears the query should be able to execute below 1 +sec easily. I'm running Postgres 7.3.1 on Mac OSX. + +After having turned on several logging options, here is a pertinent +excerpt from the log that also shows the query. It seems the query +planner takes the whole time, not the actual execution. Does anyone +have an idea what's going on here, and what I could do to alleviate the +problem? (Just to mention, I've run the same with GEQO off and if +anything it makes the timing worse.) + +2003-01-02 11:22:59 LOG: query: SELECT TW.WORKITEMKEY, +TW.PACKAGESYNOPSYS, TW.PACKAGEDESCRIPTION, TW.BUILD, +TW.LASTEDIT, TOW.LASTNAME AS LOWNER, TOW.FIRSTNAME AS FOWNER, +TOR.LASTNAME AS LORIGINATOR, TOR.FIRSTNAME AS FORIGINATOR, +TRE.LASTNAME AS LRESPONSIBLE, TRE.FIRSTNAME AS FRESPONSIBLE, +TPRJC.LABEL AS PROJCATLABEL, TPRJ.LABEL AS PROJLABEL, TCL.LABEL AS +REQCLASS, +TW.CATEGORYKEY AS REQCATEGORY, TW.PRIORITYKEY AS REQPRIORITY, +TW.SEVERITYKEY AS REQSEVERITY, TST.LABEL AS STATELABEL, TW.STATE, +TST.STATEFLAG, TREL.LABEL AS RELEASELABEL, TW.ENDDATE +FROM TWORKITEM TW, TPERSON TOW, TPERSON TOR, TPERSON TRE, TPROJECT TPRJ, +TPROJCAT TPRJC, TCATEGORY TCAT, TCLASS TCL, TPRIORITY TPRIO, TSEVERITY +TSEV, +TSTATE TST, TRELEASE TREL +WHERE (TW.OWNER = TOW.PKEY) AND (TW.ORIGINATOR = TOR.PKEY) +AND (TW.RESPONSIBLE = TRE.PKEY) AND (TW.PROJCATKEY = TPRJC.PKEY) +AND (TPRJ.PKEY = TPRJC.PROJKEY) AND (TW.CLASSKEY = TCL.PKEY) +AND (TW.CATEGORYKEY = TCAT.PKEY) AND (TW.PRIORITYKEY = TPRIO.PKEY) +AND (TW.SEVERITYKEY = TSEV.PKEY) AND (TST.PKEY = TW.STATE) +AND (TREL.PKEY = TW.RELSCHEDULEDKEY) + +2003-01-02 11:23:02 LOG: PLANNER STATISTICS +! system usage stats: +! 2.730501 elapsed 1.400000 user 0.000000 system sec +! [3.580000 user 0.000000 sys total] +! 0/0 [0/0] filesystem blocks in/out +! 0/0 [0/0] page faults/reclaims, 0 [0] swaps +! 0 [0] signals rcvd, 0/0 [0/14] messages rcvd/sent +! 0/0 [24/0] voluntary/involuntary context switches +! buffer usage stats: +! Shared blocks: 0 read, 0 written, buffer hit +rate = 0.00% +! Local blocks: 0 read, 0 written, buffer hit +rate = 0.00% +! Direct blocks: 0 read, 0 written +2003-01-02 11:23:02 LOG: EXECUTOR STATISTICS +! system usage stats: +! 0.005024 elapsed 0.000000 user 0.000000 system sec +! [3.580000 user 0.000000 sys total] +! 0/0 [0/0] filesystem blocks in/out +! 0/0 [0/0] page faults/reclaims, 0 [0] swaps +! 0 [0] signals rcvd, 0/0 [0/14] messages rcvd/sent +! 0/0 [24/0] voluntary/involuntary context switches +! buffer usage stats: +! Shared blocks: 0 read, 0 written, buffer hit +rate = 100.00% +! Local blocks: 0 read, 0 written, buffer hit +rate = 0.00% +! Direct blocks: 0 read, 0 written +2003-01-02 11:23:02 LOG: duration: 2.740243 sec +2003-01-02 11:23:02 LOG: QUERY STATISTICS +! system usage stats: +! 0.006432 elapsed 0.000000 user 0.000000 system sec +! [3.580000 user 0.000000 sys total] +! 0/0 [0/0] filesystem blocks in/out +! 0/0 [0/0] page faults/reclaims, 0 [0] swaps +! 0 [0] signals rcvd, 0/0 [0/14] messages rcvd/sent +! 0/0 [24/0] voluntary/involuntary context switches +! buffer usage stats: +! Shared blocks: 0 read, 0 written, buffer hit +rate = 100.00% +! Local blocks: 0 read, 0 written, buffer hit +rate = 0.00% +! Direct blocks: 0 read, 0 written + +-- +------------------------------------------------------------- +Hilmar Lapp email: lapp at gnf.org +GNF, San Diego, Ca. 92121 phone: +1-858-812-1757 +------------------------------------------------------------- + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 15:05:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id F100C476B06 + for ; + Thu, 2 Jan 2003 15:05:53 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 3CB0B4769FF + for ; + Thu, 2 Jan 2003 14:57:36 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h02JvY0U003256; + Thu, 2 Jan 2003 14:57:35 -0500 (EST) +To: "Steve Wolfe" +Cc: pgsql-performance@postgresql.org +Subject: Re: Question on hardware & server capacity +In-reply-to: <008701c2b286$4c9c2ae0$88693fd1@WEASEL> +References: <008701c2b286$4c9c2ae0$88693fd1@WEASEL> +Comments: In-reply-to "Steve Wolfe" + message dated "Thu, 02 Jan 2003 10:42:05 -0700" +Date: Thu, 02 Jan 2003 14:57:34 -0500 +Message-ID: <3255.1041537454@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/6 +X-Sequence-Number: 653 + +"Steve Wolfe" writes: +> I logged some queries, and found that in an average second, the machine +> forks off 10 new backends, and responds to 50 selects and 3 updates. + +So an average backend only processes ~ 5 queries before exiting? + +> My feelings are that the machine is being swamped by both the number of +> context switches and the I/O, most likely the memory bandwidth. + +I think you're getting killed by the lack of connection pooling. +Launching a new backend is moderately expensive: there's not just the +OS-level fork overhead, but significant cost to fill the catalog caches +to useful levels, etc. + +7.3 has reduced some of those startup costs a little, so if you're still +on 7.2 then an update might help. But I'd strongly recommend getting +connection re-use in place before you go off and buy hardware. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 2 15:34:34 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B3AB2476767 + for ; + Thu, 2 Jan 2003 15:34:32 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 232D7476DD1 + for ; + Thu, 2 Jan 2003 15:24:21 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h02KOK0U003560; + Thu, 2 Jan 2003 15:24:20 -0500 (EST) +To: Hilmar Lapp +Cc: pgsql-performance@postgresql.org +Subject: Re: join over 12 tables takes 3 secs to plan +In-reply-to: <43D30901-1E8A-11D7-9244-000393B4BFF6@gmx.net> +References: <43D30901-1E8A-11D7-9244-000393B4BFF6@gmx.net> +Comments: In-reply-to Hilmar Lapp + message dated "Thu, 02 Jan 2003 11:42:02 -0800" +Date: Thu, 02 Jan 2003 15:24:20 -0500 +Message-ID: <3559.1041539060@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/7 +X-Sequence-Number: 654 + +Hilmar Lapp writes: +> I have a query generated by an application (not mine, but there's +> nothing I can find that looks bad about the query itself) that takes an +> excessive amount of time to return even though there are almost no rows +> in the schema yet. + +Read +http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/explicit-joins.html + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 2 15:48:32 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 52835476D4D + for ; + Thu, 2 Jan 2003 15:48:31 -0500 (EST) +Received: from bob.samurai.com (bob.samurai.com [205.207.28.75]) + by postgresql.org (Postfix) with ESMTP id 31341476E24 + for ; + Thu, 2 Jan 2003 15:41:23 -0500 (EST) +Received: from samurai.com (localhost [127.0.0.1]) + by bob.samurai.com (Postfix) with SMTP + id 004F91D5C; Thu, 2 Jan 2003 15:41:24 -0500 (EST) +Received: from cpe00d0096a6cd5.cpe.net.cable.rogers.com ([24.112.166.30]) + (SquirrelMail authenticated user neilc) + by mailbox.samurai.com with HTTP; + Thu, 2 Jan 2003 15:41:24 -0500 (EST) +Message-ID: <1309.24.112.166.30.1041540084.squirrel@mailbox.samurai.com> +Date: Thu, 2 Jan 2003 15:41:24 -0500 (EST) +Subject: Re: join over 12 tables takes 3 secs to plan +From: "Neil Conway" +To: +In-Reply-To: <43D30901-1E8A-11D7-9244-000393B4BFF6@gmx.net> +References: <43D30901-1E8A-11D7-9244-000393B4BFF6@gmx.net> +X-Priority: 3 +Importance: Normal +Cc: +X-Mailer: SquirrelMail (version 1.2.9) +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/8 +X-Sequence-Number: 655 + +Hilmar Lapp said: +> I have a query generated by an application (not mine, but there's +> nothing I can find that looks bad about the query itself) that takes an +> excessive amount of time to return even though there are almost no rows +> in the schema yet. + +Yes -- an exhaustive search to determine the correct join order for a +multiple relation query is similar to solving the traveling salesman +problem (only more difficult, due to the availability of different join +algorithms, etc.). GEQO should be faster than the default optimizer for +large queries involving large numbers of joins, but it's still going to +take a fair bit of time. + +In other words, it's not a surprise that a 12-relation join takes a little +while to plan. + +> I'm running Postgres 7.3.1 on Mac OSX. + +Tom recently checked in some optimizations for GEQO in CVS HEAD, so you +could try using that (or at least testing it, so you have an idea of what +7.4 will perform like). + +You could also try using prepared queries. + +Finally, there are a bunch of GEQO tuning parameters that you might want +to play with. They should allow you to reduce the planning time a bit, in +exchange for possibly generating an inferior plan. + +Cheers, + +Neil + + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 15:57:35 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C6192476048 + for ; + Thu, 2 Jan 2003 15:57:32 -0500 (EST) +Received: from local.iboats.com (local.iboats.com [209.63.105.131]) + by postgresql.org (Postfix) with SMTP id 52746476419 + for ; + Thu, 2 Jan 2003 15:57:08 -0500 (EST) +Received: (qmail 17032 invoked by uid 82); 2 Jan 2003 13:56:43 -0700 +Received: from nw@codon.com by local.iboats.com by uid 81 with + qmail-scanner-1.14 ( Clear:. + Processed in 0.027759 secs); 02 Jan 2003 20:56:43 -0000 +Received: from unknown (HELO WEASEL) (209.63.105.136) + by 0 with SMTP; 2 Jan 2003 13:56:42 -0700 +Message-ID: <006401c2b2a1$d322fec0$88693fd1@WEASEL> +From: "Steve Wolfe" +To: +References: <008701c2b286$4c9c2ae0$88693fd1@WEASEL> + <3255.1041537454@sss.pgh.pa.us> +Subject: Re: Question on hardware & server capacity +Date: Thu, 2 Jan 2003 13:59:19 -0700 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 6.00.2800.1106 +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/9 +X-Sequence-Number: 656 + +> So an average backend only processes ~ 5 queries before exiting? +> + +> 7.3 has reduced some of those startup costs a little, so if you're still +> on 7.2 then an update might help. But I'd strongly recommend getting +> connection re-use in place before you go off and buy hardware. + + I've been fooling around with some connection pooling, and it hasn't +make the sort of difference we're looking for. Going from 3 queries per +back-end to 100 queries per backend made only about a 20% difference. +While that's nothing to scoff at, we're looking for at least a 100% +improvement. Either way, the connection pooling WILL be put in place, but +I'm certainly not counting on it preventing the need for a hardware +upgrade. + +steve + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 16:03:58 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8E32F476376 + for ; + Thu, 2 Jan 2003 16:03:57 -0500 (EST) +Received: from ns1.gnf.org (ns1.gnf.org [63.196.132.67]) + by postgresql.org (Postfix) with ESMTP id A216B476264 + for ; + Thu, 2 Jan 2003 16:03:56 -0500 (EST) +Received: from EXCHCLUSTER01.lj.gnf.org (exch01.lj.gnf.org [172.25.10.19]) + by ns1.gnf.org (8.12.3/8.12.3) with ESMTP id h02L3pMf020143 + for ; + Thu, 2 Jan 2003 13:03:51 -0800 (PST) (envelope-from hlapp@gmx.net) +Received: from gmx.net ([172.25.30.55]) by EXCHCLUSTER01.lj.gnf.org with + Microsoft SMTPSVC(5.0.2195.5329); Thu, 2 Jan 2003 13:03:54 -0800 +Date: Thu, 2 Jan 2003 13:03:54 -0800 +Subject: Re: join over 12 tables takes 3 secs to plan +Content-Type: text/plain; delsp=yes; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: pgsql-performance@postgresql.org +To: Tom Lane +From: Hilmar Lapp +In-Reply-To: <3559.1041539060@sss.pgh.pa.us> +Message-Id: +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-OriginalArrivalTime: 02 Jan 2003 21:03:54.0996 (UTC) + FILETIME=[75C31340:01C2B2A2] +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/10 +X-Sequence-Number: 657 + +Thanks for the pointer Tom. The application that's generating those +queries is open source, so I could even go in and hack the query +generating code accordingly, but I doubt I can spare that time. Given +the information in the document you pointed me at and Neil's email I +assume there is no other immediate remedy. + +As an added note, appreciating that query optimization is a difficult +problem, and I do think PostgreSQL is a great product. Having said +that, I've written 16-table joins for Oracle and always found them to +plan within a second or two, so that's why I thought there's nothing +special about the query I posted ... I'm not saying this to be bashful +about PostgreSQL, but rather to suggest that apparently there are ways +to do it pretty fast. + +I'm only starting to use PostgreSQL and making experiences, so I'm +asking for forgiveness what may occasionally seem to be ignorant ... + + -hilmar + +On Thursday, January 2, 2003, at 12:24 PM, Tom Lane wrote: + +> Hilmar Lapp writes: +>> I have a query generated by an application (not mine, but there's +>> nothing I can find that looks bad about the query itself) that takes +>> an +>> excessive amount of time to return even though there are almost no +>> rows +>> in the schema yet. +> +> Read +> http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/explicit- +> joins.html +> +> regards, tom lane +> +> +-- +------------------------------------------------------------- +Hilmar Lapp email: lapp at gnf.org +GNF, San Diego, Ca. 92121 phone: +1-858-812-1757 +------------------------------------------------------------- + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 16:08:25 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0BAA847610A + for ; + Thu, 2 Jan 2003 16:08:25 -0500 (EST) +Received: from ns1.gnf.org (ns1.gnf.org [63.196.132.67]) + by postgresql.org (Postfix) with ESMTP id E21484760AF + for ; + Thu, 2 Jan 2003 16:08:23 -0500 (EST) +Received: from EXCHCLUSTER01.lj.gnf.org (exch01.lj.gnf.org [172.25.10.19]) + by ns1.gnf.org (8.12.3/8.12.3) with ESMTP id h02L8MMf020161 + for ; + Thu, 2 Jan 2003 13:08:22 -0800 (PST) (envelope-from hlapp@gmx.net) +Received: from gmx.net ([172.25.30.55]) by EXCHCLUSTER01.lj.gnf.org with + Microsoft SMTPSVC(5.0.2195.5329); Thu, 2 Jan 2003 13:08:25 -0800 +Date: Thu, 2 Jan 2003 13:08:24 -0800 +Subject: Re: join over 12 tables takes 3 secs to plan +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: +To: "Neil Conway" +From: Hilmar Lapp +In-Reply-To: <1309.24.112.166.30.1041540084.squirrel@mailbox.samurai.com> +Message-Id: <54E69E80-1E96-11D7-9244-000393B4BFF6@gmx.net> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-OriginalArrivalTime: 02 Jan 2003 21:08:25.0130 (UTC) + FILETIME=[16C640A0:01C2B2A3] +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/11 +X-Sequence-Number: 658 + + +On Thursday, January 2, 2003, at 12:41 PM, Neil Conway wrote: + +> +> Finally, there are a bunch of GEQO tuning parameters that you might +> want +> to play with. They should allow you to reduce the planning time a bit, +> in +> exchange for possibly generating an inferior plan. +> +> + +Thanks for the tip. I have to admit that I have zero experience with +tuning GAs. If anyone could provide a starter which parameters are best +to start with? Or is it in the docs? + + -hilmar + +-- +------------------------------------------------------------- +Hilmar Lapp email: lapp at gnf.org +GNF, San Diego, Ca. 92121 phone: +1-858-812-1757 +------------------------------------------------------------- + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 16:11:35 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BB138476048 + for ; + Thu, 2 Jan 2003 16:11:33 -0500 (EST) +Received: from bob.samurai.com (bob.samurai.com [205.207.28.75]) + by postgresql.org (Postfix) with ESMTP id 401AB475F5D + for ; + Thu, 2 Jan 2003 16:11:33 -0500 (EST) +Received: from samurai.com (localhost [127.0.0.1]) + by bob.samurai.com (Postfix) with SMTP + id 75E3B1F2C; Thu, 2 Jan 2003 16:11:34 -0500 (EST) +Received: from cpe00d0096a6cd5.cpe.net.cable.rogers.com ([24.112.166.30]) + (SquirrelMail authenticated user neilc) + by mailbox.samurai.com with HTTP; + Thu, 2 Jan 2003 16:11:34 -0500 (EST) +Message-ID: <1455.24.112.166.30.1041541894.squirrel@mailbox.samurai.com> +Date: Thu, 2 Jan 2003 16:11:34 -0500 (EST) +Subject: Re: join over 12 tables takes 3 secs to plan +From: "Neil Conway" +To: +In-Reply-To: <54E69E80-1E96-11D7-9244-000393B4BFF6@gmx.net> +References: <1309.24.112.166.30.1041540084.squirrel@mailbox.samurai.com> + <54E69E80-1E96-11D7-9244-000393B4BFF6@gmx.net> +X-Priority: 3 +Importance: Normal +Cc: +X-Mailer: SquirrelMail (version 1.2.9) +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/12 +X-Sequence-Number: 659 + +Hilmar Lapp said: +> Thanks for the tip. I have to admit that I have zero experience with +> tuning GAs. If anyone could provide a starter which parameters are best +> to start with? Or is it in the docs? + +http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/runtime-config.html +lists the available options. + +I'd think that GEQO_EFFORT, GEQO_GENERATIONS, and GEQO_POOL_SIZE would be +the parameters that would effect performance the most. + +Cheers, + +Neil + + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 16:21:55 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0E292476D44 + for ; + Thu, 2 Jan 2003 16:21:55 -0500 (EST) +Received: from bob.samurai.com (bob.samurai.com [205.207.28.75]) + by postgresql.org (Postfix) with ESMTP id 95A34476CD8 + for ; + Thu, 2 Jan 2003 16:21:27 -0500 (EST) +Received: from samurai.com (localhost [127.0.0.1]) + by bob.samurai.com (Postfix) with SMTP + id BEB511F2C; Thu, 2 Jan 2003 16:21:28 -0500 (EST) +Received: from cpe00d0096a6cd5.cpe.net.cable.rogers.com ([24.112.166.30]) + (SquirrelMail authenticated user neilc) + by mailbox.samurai.com with HTTP; + Thu, 2 Jan 2003 16:21:28 -0500 (EST) +Message-ID: <1477.24.112.166.30.1041542488.squirrel@mailbox.samurai.com> +Date: Thu, 2 Jan 2003 16:21:28 -0500 (EST) +Subject: Re: join over 12 tables takes 3 secs to plan +From: "Neil Conway" +To: +In-Reply-To: +References: <3559.1041539060@sss.pgh.pa.us> + +X-Priority: 3 +Importance: Normal +Cc: , +X-Mailer: SquirrelMail (version 1.2.9) +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/13 +X-Sequence-Number: 660 + +Hilmar Lapp said: +> As an added note, appreciating that query optimization is a difficult +> problem, and I do think PostgreSQL is a great product. Having said +> that, I've written 16-table joins for Oracle and always found them to +> plan within a second or two, so that's why I thought there's nothing +> special about the query I posted ... I'm not saying this to be bashful +> about PostgreSQL, but rather to suggest that apparently there are ways +> to do it pretty fast. + +I'm sure there is room for improvement -- either by adding additional +heuristics to the default optimizer, by improving GEQO, or by implementing +another method for non-exhaustive search for large join queries (there are +several ways to handle large join queries, only one of which uses a +genetic algorithm: see "Query Optimization" (Ioannidis, 1996) for a good +introductory survey). + +If you'd like to take a shot at improving it, let me know if I can be of +any assistance :-) + +Cheers, + +Neil + + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 16:29:40 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9B474475C8B + for ; + Thu, 2 Jan 2003 16:29:38 -0500 (EST) +Received: from ns1.gnf.org (ns1.gnf.org [63.196.132.67]) + by postgresql.org (Postfix) with ESMTP id 0F47A474E53 + for ; + Thu, 2 Jan 2003 16:29:38 -0500 (EST) +Received: from EXCHCLUSTER01.lj.gnf.org (exch01.lj.gnf.org [172.25.10.19]) + by ns1.gnf.org (8.12.3/8.12.3) with ESMTP id h02LTaMf020318 + for ; + Thu, 2 Jan 2003 13:29:36 -0800 (PST) (envelope-from hlapp@gmx.net) +Received: from gmx.net ([172.25.30.55]) by EXCHCLUSTER01.lj.gnf.org with + Microsoft SMTPSVC(5.0.2195.5329); Thu, 2 Jan 2003 13:29:39 -0800 +Date: Thu, 2 Jan 2003 13:29:39 -0800 +Subject: Re: join over 12 tables takes 3 secs to plan +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: , +To: "Neil Conway" +From: Hilmar Lapp +In-Reply-To: <1477.24.112.166.30.1041542488.squirrel@mailbox.samurai.com> +Message-Id: <4C57DC24-1E99-11D7-9244-000393B4BFF6@gmx.net> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-OriginalArrivalTime: 02 Jan 2003 21:29:39.0436 (UTC) + FILETIME=[0E51EAC0:01C2B2A6] +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/14 +X-Sequence-Number: 661 + + +On Thursday, January 2, 2003, at 01:21 PM, Neil Conway wrote: + +> If you'd like to take a shot at improving it, let me know if I can be +> of +> any assistance :-) +> +> + +Would be a very cool problem to work on once I enroll in a CS program +:-) + + -hilmar + +-- +------------------------------------------------------------- +Hilmar Lapp email: lapp at gnf.org +GNF, San Diego, Ca. 92121 phone: +1-858-812-1757 +------------------------------------------------------------- + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 16:42:10 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 34350475C8B + for ; + Thu, 2 Jan 2003 16:42:09 -0500 (EST) +Received: from joeconway.com (unknown [63.210.180.150]) + by postgresql.org (Postfix) with ESMTP id 85335474E53 + for ; + Thu, 2 Jan 2003 16:42:08 -0500 (EST) +Received: from [192.168.5.3] (account jconway HELO joeconway.com) + by joeconway.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP-TLS id 1499578; Thu, 02 Jan 2003 14:15:41 -0800 +Message-ID: <3E14B1C7.9040007@joeconway.com> +Date: Thu, 02 Jan 2003 13:40:23 -0800 +From: Joe Conway +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; + rv:1.2) Gecko/20021126 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Hilmar Lapp +Cc: Tom Lane , pgsql-performance@postgresql.org +Subject: Re: join over 12 tables takes 3 secs to plan +References: +In-Reply-To: +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/15 +X-Sequence-Number: 662 + +Hilmar Lapp wrote: +> As an added note, appreciating that query optimization is a difficult +> problem, and I do think PostgreSQL is a great product. Having said +> that, I've written 16-table joins for Oracle and always found them to +> plan within a second or two, so that's why I thought there's nothing +> special about the query I posted ... I'm not saying this to be bashful +> about PostgreSQL, but rather to suggest that apparently there are ways +> to do it pretty fast. + +I could be wrong, but I believe Oracle uses its rule based optimizer by +default, not its cost based optimizer. A rule based optimizer will be very +quick all the time, but might not pick the best plan all the time, because it +doesn't consider the statistics of the data. Any idea which one you were using +in your Oracle experience? + +Joe + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 17:07:44 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CC87B475B99 + for ; + Thu, 2 Jan 2003 17:07:42 -0500 (EST) +Received: from rh72.home.ee (unknown [194.204.44.121]) + by postgresql.org (Postfix) with ESMTP id 5D037475B8E + for ; + Thu, 2 Jan 2003 17:07:41 -0500 (EST) +Received: from rh72.home.ee (localhost.localdomain [127.0.0.1]) + by rh72.home.ee (8.12.5/8.12.5) with ESMTP id h02M7aRX002831; + Fri, 3 Jan 2003 03:07:37 +0500 +Received: (from hannu@localhost) + by rh72.home.ee (8.12.5/8.12.5/Submit) id h02M7Zrp002829; + Fri, 3 Jan 2003 03:07:35 +0500 +X-Authentication-Warning: rh72.home.ee: hannu set sender to hannu@tm.ee using + -f +Subject: Re: Question on hardware & server capacity +From: Hannu Krosing +To: Steve Wolfe +Cc: pgsql-performance@postgresql.org +In-Reply-To: <008701c2b286$4c9c2ae0$88693fd1@WEASEL> +References: <008701c2b286$4c9c2ae0$88693fd1@WEASEL> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1041545254.2176.28.camel@rh72.home.ee> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 03 Jan 2003 03:07:34 +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/16 +X-Sequence-Number: 663 + +Steve Wolfe kirjutas N, 02.01.2003 kell 22:42: +> Well, our current database server is getting tremendously loaded, and +> right now there isn't a clear-cut choice as to an upgrade path - at least +> not within the commodity hardware market. + +Have you optimized your queries to max ? + +Often one or two of the queries take most of resources and starve +others. + +> The machine is a dual AthlonMP 2000, with 2 gigs of RAM. the loads on +> the machine are getting out of hand, and performance is noticeably slowed. +> 'top' shows the CPU's as being anywhere from 30% to 50% idle, with (on +> average) 5-10 postmasters in the "non-idle" state. 'vmstat' shows bi/bo +> pegged at zero (copious quantities of disk cache, fsync turned off), + +Could there be some unnecessary trashing between OS and PG caches ? +How could this be detected ? + +> interrupts fluctuating between 200 and 1,000 per second (avg. is approx +> 400), context switches between 1300 and 4500 (avg. is approx 2300). I +> logged some queries, and found that in an average second, the machine +> forks off 10 new backends, and responds to 50 selects and 3 updates. + +What are the average times for query responses ? + +Will running the same queries (the ones from the logs) serially run +faster/slower/at the same speed ? + +Do you have some triggers on updates - I have occasionally found them to +be real performance killers. + +Also - if memory bandwidth is the issue, you could tweak the parameters +so that PG will prefer index scans more often - there are rumors that +under heavy loads it is often better to use more index scans due to +possible smaller memory/buffer use, even if they would be slower for +only one or two backends. + +> My feelings are that the machine is being swamped by both the number of +> context switches and the I/O, most likely the memory bandwidth. I'm +> working on implementing some connection pooling to reduce the number of +> new backends forked off, but there's not much I can do about the sheer +> volume (or cost) of queries. + +You could try to replicate the updates (one master - multiple slaves) +and distribute the selects. I guess this is what current postgreSQL +state-of-the-art already lets you do with reasonable effort. + +> Now, if quad-Hammers were here, I'd simply throw hardware at it. +> Unfortunately, they're not. + +Yes, it's BAD if your business grows faster than Moores law ;-p + +> So far, about the only commodity-level answer +> I can think of would be a dual P4 Xeon, with the 533 MHz bus, and +> dual-channel DDR memory. That would give each processor approximately +> double the memory bandwidth over what we're currently running. +> +> I'm fairly sure that would at least help lower the load, but I'm not +> sure by how much. If anyone has run testing under similar platforms, I'd +> love to hear of the performance difference. + +How big is the dataset ? What kinds of queries ? + +I could perhaps run some quick tests on quad Xeon 1.40GHz , 2GB before +this box goes to production sometime early next week. It is a RedHat +AS2.1 box with rh-postgresql-7.2.3-1_as21. + +# hdparm -tT /dev/sda + +/dev/sda: + Timing buffer-cache reads: 128 MB in 0.39 seconds =328.21 MB/sec + Timing buffered disk reads: 64 MB in 1.97 seconds = 32.49 MB/sec + +> If this is going to chop the +> loads in half, I'll do it. If it's only going to improve it by 10% or so, +> I'm not going to waste the money. + +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Thu Jan 2 17:51:20 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id DFE26476D2E + for ; + Thu, 2 Jan 2003 17:51:18 -0500 (EST) +Received: from ns1.gnf.org (ns1.gnf.org [63.196.132.67]) + by postgresql.org (Postfix) with ESMTP id 7DF8F47610A + for ; + Thu, 2 Jan 2003 17:49:01 -0500 (EST) +Received: from EXCHCLUSTER01.lj.gnf.org (exch01.lj.gnf.org [172.25.10.19]) + by ns1.gnf.org (8.12.3/8.12.3) with ESMTP id h02MmwMf020646 + for ; + Thu, 2 Jan 2003 14:48:59 -0800 (PST) (envelope-from hlapp@gmx.net) +Received: from gmx.net ([172.25.30.55]) by EXCHCLUSTER01.lj.gnf.org with + Microsoft SMTPSVC(5.0.2195.5329); Thu, 2 Jan 2003 14:49:02 -0800 +Date: Thu, 2 Jan 2003 14:49:01 -0800 +Subject: Re: join over 12 tables takes 3 secs to plan +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: Tom Lane , pgsql-performance@postgresql.org +To: Joe Conway +From: Hilmar Lapp +In-Reply-To: <3E14B1C7.9040007@joeconway.com> +Message-Id: <630BD04E-1EA4-11D7-9B10-000393B4BFF6@gmx.net> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-OriginalArrivalTime: 02 Jan 2003 22:49:02.0448 (UTC) + FILETIME=[254BDF00:01C2B2B1] +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/17 +X-Sequence-Number: 664 + + +On Thursday, January 2, 2003, at 01:40 PM, Joe Conway wrote: + +> I could be wrong, but I believe Oracle uses its rule based optimizer +> by default, not its cost based optimizer. + +They changed it from 9i on. The cost-based is now the default. The +recent 16-table join example I was referring to was on the cost-based +optimizer. + +They actually did an amazing good job on the CBO, at least in my +experience. I caught it screwing up badly only once, only to realize +that I had forgotten to compute the statistics ... It also allows for +different plans depending on whether you want some rows fast and the +total not necessarily as fast, or all rows as fast as possible. This +also caught me off-guard initially when I wanted to peek into the first +rows returned and had to wait almost as long as the entire query to +return. (optimizing for all rows is the default) + +> A rule based optimizer will be very quick all the time, but might not +> pick the best plan all the time, because it doesn't consider the +> statistics of the data. + +True. In a situation with not that many rows though even a sub-optimal +plan that takes 10x longer to execute than the possibly best (e.g., 1s +vs 0.1s), but plans 10x faster (e.g. 0.3s vs 3s), might still return +significantly sooner. Especially if some of the tables have been cached +in memory already ... + + -hilmar +-- +------------------------------------------------------------- +Hilmar Lapp email: lapp at gnf.org +GNF, San Diego, Ca. 92121 phone: +1-858-812-1757 +------------------------------------------------------------- + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 19:01:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 17C15476C67 + for ; + Thu, 2 Jan 2003 19:01:16 -0500 (EST) +Received: from lakemtao02.cox.net (lakemtao02.cox.net [68.1.17.243]) + by postgresql.org (Postfix) with ESMTP id 73E0C476C5B + for ; + Thu, 2 Jan 2003 19:01:15 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao02.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030103000118.QIVY2203.lakemtao02.cox.net@[192.168.1.1]> + for ; + Thu, 2 Jan 2003 19:01:18 -0500 +Subject: Re: join over 12 tables takes 3 secs to plan +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <3E14B1C7.9040007@joeconway.com> +References: + <3E14B1C7.9040007@joeconway.com> +Content-Type: text/plain +Organization: +Message-Id: <1041552070.16584.191.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 02 Jan 2003 18:01:10 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/18 +X-Sequence-Number: 665 + +On Thu, 2003-01-02 at 15:40, Joe Conway wrote: +> Hilmar Lapp wrote: +> > As an added note, appreciating that query optimization is a difficult +> > problem, and I do think PostgreSQL is a great product. Having said +> > that, I've written 16-table joins for Oracle and always found them to +> > plan within a second or two, so that's why I thought there's nothing +> > special about the query I posted ... I'm not saying this to be bashful +> > about PostgreSQL, but rather to suggest that apparently there are ways +> > to do it pretty fast. +> +> I could be wrong, but I believe Oracle uses its rule based optimizer by +> default, not its cost based optimizer. A rule based optimizer will be very +> quick all the time, but might not pick the best plan all the time, because it +> doesn't consider the statistics of the data. Any idea which one you were using +> in your Oracle experience? + +Remember also that the commercial RDMBSs have had many engineers working +for many years on these problems, whereas PostgreSQL hasn't... + +Could it be that PG isn't the proper tool for the job? Of course, +at USD20K/cp, Oracle may be slightly out of budget. + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 19:24:51 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 15C1F475EB9 + for ; + Thu, 2 Jan 2003 19:24:50 -0500 (EST) +Received: from ns1.gnf.org (ns1.gnf.org [63.196.132.67]) + by postgresql.org (Postfix) with ESMTP id 7E421475B8E + for ; + Thu, 2 Jan 2003 19:24:49 -0500 (EST) +Received: from EXCHCLUSTER01.lj.gnf.org (exch01.lj.gnf.org [172.25.10.19]) + by ns1.gnf.org (8.12.3/8.12.3) with ESMTP id h030OmMf020987 + for ; + Thu, 2 Jan 2003 16:24:48 -0800 (PST) (envelope-from hlapp@gmx.net) +Received: from gmx.net ([172.25.30.55]) by EXCHCLUSTER01.lj.gnf.org with + Microsoft SMTPSVC(5.0.2195.5329); Thu, 2 Jan 2003 16:24:52 -0800 +Date: Thu, 2 Jan 2003 16:24:51 -0800 +Subject: Re: join over 12 tables takes 3 secs to plan +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: PgSQL Performance ML +To: Ron Johnson +From: Hilmar Lapp +In-Reply-To: <1041552070.16584.191.camel@haggis> +Message-Id: +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-OriginalArrivalTime: 03 Jan 2003 00:24:52.0601 (UTC) + FILETIME=[88A79690:01C2B2BE] +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/19 +X-Sequence-Number: 666 + + +On Thursday, January 2, 2003, at 04:01 PM, Ron Johnson wrote: + +> +> Could it be that PG isn't the proper tool for the job? Of course, +> at USD20K/cp, Oracle may be slightly out of budget. +> +> + +We are in fact an Oracle shop, but the application I tried to get +running (http://trackplus.sourceforge.net/) I wanted to run on an OSS +RDBMS so that I could easily move it onto my laptop etc (BTW apparently +it was primarily developed on InterBase/Firebird). Anyway, I was able +to cut the planning time for those queries in half by setting +geqo_pool_size to 512. However, now it gets stuck for an excessive +amount of time after the issue update page and I have no idea what's +going on, and I'm not in the mood to track it down. So finally I'm +giving up and I'm rolling it out on MySQL on which it is working fine, +even though I don't like MySQL to say the least. + + -hilmar + +-- +------------------------------------------------------------- +Hilmar Lapp email: lapp at gnf.org +GNF, San Diego, Ca. 92121 phone: +1-858-812-1757 +------------------------------------------------------------- + + +From pgsql-performance-owner@postgresql.org Thu Jan 2 19:36:11 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4EBA7476CEE + for ; + Thu, 2 Jan 2003 19:36:11 -0500 (EST) +Received: from clearmetrix.com (unknown [209.92.142.67]) + by postgresql.org (Postfix) with ESMTP id A66D64766F6 + for ; + Thu, 2 Jan 2003 19:36:10 -0500 (EST) +Received: from clearmetrix.com (chw.muvpn.clearmetrix.com [172.16.1.3]) + by clearmetrix.com (8.11.6/linuxconf) with ESMTP id h030aAg19710; + Thu, 2 Jan 2003 19:36:10 -0500 +Message-ID: <3E14DAFC.3080409@clearmetrix.com> +Date: Thu, 02 Jan 2003 19:36:12 -0500 +From: "Charles H. Woloszynski" +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; + rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Hilmar Lapp +Cc: Ron Johnson , + PgSQL Performance ML +Subject: Re: join over 12 tables takes 3 secs to plan +References: +In-Reply-To: +Content-Type: text/plain; charset=ISO-8859-1; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/20 +X-Sequence-Number: 667 + + + +Hilmar Lapp wrote: + +> We are in fact an Oracle shop, but the application I tried to get +> running (http://trackplus.sourceforge.net/) I wanted to run on an OSS +> RDBMS so that I could easily move it onto my laptop etc (BTW +> apparently it was primarily developed on InterBase/Firebird). Anyway, +> I was able to cut the planning time for those queries in half by +> setting geqo_pool_size to 512. However, now it gets stuck for an +> excessive amount of time after the issue update page and I have no +> idea what's going on, and I'm not in the mood to track it down. So +> finally I'm giving up and I'm rolling it out on MySQL on which it is +> working fine, even though I don't like MySQL to say the least. +> +> -hilmar +> +Uhoh, did I just hear a gauntlet thrown down ... works well on MySQL but +not on PostgreSQL. If I can find the time, perhaps I can take a look at +the specific query(ies) and see what is missed in PostgreSQL that MySQL +has gotten right. + +If only there were 48 hours in a day :-). + +Charlie + +-- + + +Charles H. Woloszynski + +ClearMetrix, Inc. +115 Research Drive +Bethlehem, PA 18015 + +tel: 610-419-2210 x400 +fax: 240-371-3256 +web: www.clearmetrix.com + + + + + + +From pgsql-performance-owner@postgresql.org Fri Jan 3 12:10:21 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 51DC34763E7 + for ; + Fri, 3 Jan 2003 12:10:20 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id A4F0B4760E4 + for ; + Fri, 3 Jan 2003 12:10:19 -0500 (EST) +Received: from css120.ihs.com (css120.ihs.com [170.207.105.120]) + by mail1.ihs.com (8.12.6/8.12.6) with ESMTP id h03H6449000834; + Fri, 3 Jan 2003 10:06:40 -0700 (MST) +Date: Fri, 3 Jan 2003 10:01:29 -0700 (MST) +From: "scott.marlowe" +To: Hilmar Lapp +Cc: Ron Johnson , + PgSQL Performance ML +Subject: Re: join over 12 tables takes 3 secs to plan +In-Reply-To: +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-MailBodyFilter: Message body has not been filtered +X-MailScanner: Found to be clean +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/21 +X-Sequence-Number: 668 + +On Thu, 2 Jan 2003, Hilmar Lapp wrote: + +> +> On Thursday, January 2, 2003, at 04:01 PM, Ron Johnson wrote: +> +> > +> > Could it be that PG isn't the proper tool for the job? Of course, +> > at USD20K/cp, Oracle may be slightly out of budget. +> > +> > +> +> We are in fact an Oracle shop, but the application I tried to get +> running (http://trackplus.sourceforge.net/) I wanted to run on an OSS +> RDBMS so that I could easily move it onto my laptop etc (BTW apparently +> it was primarily developed on InterBase/Firebird). Anyway, I was able +> to cut the planning time for those queries in half by setting +> geqo_pool_size to 512. However, now it gets stuck for an excessive +> amount of time after the issue update page and I have no idea what's +> going on, and I'm not in the mood to track it down. So finally I'm +> giving up and I'm rolling it out on MySQL on which it is working fine, +> even though I don't like MySQL to say the least. + +Have you tried it on firebird for linux? It's an actively developed rdbms +that's open source too. If this was developed for it, it might be a +better fit to use that for now, and then learn postgresql under the less +rigorous schedule of simply porting, not having to get a product out the +door. + +Is an explicit join the answer here? i.e. will the number of rows we get +from each table in a single query likely to never change? If so then you +could just make an explicit join and be done with it. + + +From pgsql-performance-owner@postgresql.org Fri Jan 3 12:12:37 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3EC3F4762E7 + for ; + Fri, 3 Jan 2003 12:12:36 -0500 (EST) +Received: from jefftrout.com (h00a0cc4084e5.ne.client2.attbi.com + [24.128.215.169]) + by postgresql.org (Postfix) with SMTP id 7DAD64760E4 + for ; + Fri, 3 Jan 2003 12:12:35 -0500 (EST) +Received: (qmail 51102 invoked from network); 3 Jan 2003 17:12:44 -0000 +Received: from h00a0cc4084e5.ne.client2.attbi.com (threshar@24.128.215.169) + by h00a0cc4084e5.ne.client2.attbi.com with SMTP; + 3 Jan 2003 17:12:44 -0000 +Date: Fri, 3 Jan 2003 12:12:44 -0500 (EST) +From: Jeff +X-X-Sender: threshar@torgo +To: Hilmar Lapp +Cc: "pgsql-performance@postgresql.org" +Subject: Re: join over 12 tables takes 3 secs to plan +In-Reply-To: <43D30901-1E8A-11D7-9244-000393B4BFF6@gmx.net> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/22 +X-Sequence-Number: 669 + +On Thu, 2 Jan 2003, Hilmar Lapp wrote: + +> I have a query generated by an application (not mine, but there's +> nothing I can find that looks bad about the query itself) that takes an +> excessive amount of time to return even though there are almost no rows +> in the schema yet. 3 secs may not seem to be much, but the query is run +> by a web-application for a page you have to go through quite +> frequently, and it appears the query should be able to execute below 1 +> sec easily. I'm running Postgres 7.3.1 on Mac OSX. +> + +Hmm.. This won't fix the fact the planner takes three seconds, but since +it is a web application have you tried using PREPARE/EXECUTE so it only +needs to be planned once? (Unless I am mistaken about what prepare/execute +actually do) that way only the first visitor gets the hit.. + +------------------------------------------------------------------------------ +Jeff Trout http://www.jefftrout.com/ + Ronald McDonald, with the help of cheese soup, + controls America from a secret volkswagon hidden in the past +------------------------------------------------------------------------------- + + + +From pgsql-performance-owner@postgresql.org Fri Jan 3 12:31:28 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B4CE34764F1 + for ; + Fri, 3 Jan 2003 12:31:26 -0500 (EST) +Received: from local.iboats.com (local.iboats.com [209.63.105.131]) + by postgresql.org (Postfix) with SMTP id 72F00476DC2 + for ; + Fri, 3 Jan 2003 12:29:39 -0500 (EST) +Received: (qmail 25122 invoked by uid 82); 3 Jan 2003 10:29:21 -0700 +Received: from nw@codon.com by local.iboats.com by uid 81 with + qmail-scanner-1.14 ( Clear:. + Processed in 0.029907 secs); 03 Jan 2003 17:29:21 -0000 +Received: from unknown (HELO WEASEL) (209.63.105.136) + by 0 with SMTP; 3 Jan 2003 10:29:21 -0700 +Message-ID: <012b01c2b34e$05e267e0$88693fd1@WEASEL> +From: "Steve Wolfe" +To: +References: <008701c2b286$4c9c2ae0$88693fd1@WEASEL> + <1041545254.2176.28.camel@rh72.home.ee> +Subject: Re: Question on hardware & server capacity +Date: Fri, 3 Jan 2003 10:31:54 -0700 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 6.00.2800.1106 +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/23 +X-Sequence-Number: 670 + +> Have you optimized your queries to max ? +> +> Often one or two of the queries take most of resources and starve +> others. + + I did log a good number of queries and analyze them, and 69% of the +queries issued are from one particular application, and they consume 78% +of the total "cost". The developper is looking into optimizations, but it +doesn't look like there's going to be any low-hanging fruit. It's simply +a complicated and frequently-used app. + +> Could there be some unnecessary trashing between OS and PG caches ? +> How could this be detected ? + + The machine generally has a minimum of a hundred megs free, unused +memory, so I'm not terribly worried about memory thrashing. I've +increased the various tuneable parameters (buffer blocks, sort mem, etc.) +to the point where performance increases stopped, then I doubled them all +for good measure. I've already decided that the next machine will have at +least 4 gigs of RAM, just because RAM's cheap, and having too much is a +Good Thing. + +> Do you have some triggers on updates - I have occasionally found them to +> be real performance killers. + + There are a few triggers, but not many - and the number of updates is +extremely low relative to the number of inserts. + +> Yes, it's BAD if your business grows faster than Moores law ;-p + + .. unfortunately, that's been the case. Each year we've done slightly +more than double the traffic of the previous year - and at the same time, +as we unify all of our various data sources, the new applications that we +develop tend to make greater and greater demands on the database server. +There is always the option of the "big iron", but your +cost-per-transaction shoots through the roof. Paying a 10x premium can +really hurt. : ) + +> How big is the dataset ? What kinds of queries ? + + our ~postgres/data/base is currently 3.4 gigs. + +> I could perhaps run some quick tests on quad Xeon 1.40GHz , 2GB before +> this box goes to production sometime early next week. It is a RedHat +> AS2.1 box with rh-postgresql-7.2.3-1_as21. + + I'd appreciate that! + +steve + + +From pgsql-performance-owner@postgresql.org Fri Jan 3 13:14:58 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5FD06475CB1 + for ; + Fri, 3 Jan 2003 13:14:57 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id 8F5684763D3 + for ; + Fri, 3 Jan 2003 13:14:56 -0500 (EST) +Received: from css120.ihs.com (css120.ihs.com [170.207.105.120]) + by mail1.ihs.com (8.12.6/8.12.6) with ESMTP id h03IBDIk005142; + Fri, 3 Jan 2003 11:11:13 -0700 (MST) +Date: Fri, 3 Jan 2003 11:06:38 -0700 (MST) +From: "scott.marlowe" +To: Steve Wolfe +Cc: +Subject: Re: Question on hardware & server capacity +In-Reply-To: <012b01c2b34e$05e267e0$88693fd1@WEASEL> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-MailBodyFilter: Message body has not been filtered +X-MailScanner: Found to be clean +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/24 +X-Sequence-Number: 671 + +On Fri, 3 Jan 2003, Steve Wolfe wrote: + +> > Have you optimized your queries to max ? +> > +> > Often one or two of the queries take most of resources and starve +> > others. +> +> I did log a good number of queries and analyze them, and 69% of the +> queries issued are from one particular application, and they consume 78% +> of the total "cost". The developper is looking into optimizations, but it +> doesn't look like there's going to be any low-hanging fruit. It's simply +> a complicated and frequently-used app. +> +> > Could there be some unnecessary trashing between OS and PG caches ? +> > How could this be detected ? +> +> The machine generally has a minimum of a hundred megs free, unused +> memory, so I'm not terribly worried about memory thrashing. I've +> increased the various tuneable parameters (buffer blocks, sort mem, etc.) +> to the point where performance increases stopped, then I doubled them all +> for good measure. I've already decided that the next machine will have at +> least 4 gigs of RAM, just because RAM's cheap, and having too much is a +> Good Thing. + +Actually, free memory doesn't mean a whole lot. How much memory is being +used as cache by the kernel? I've found that as long as the kernel is +caching more data than postgresql, performance is better than when +postgresql starts using more memory than the OS. for example, on my boxes +at work, we have 1.5 gigs ram, and 256 megs are allocated to pgsql as +shared buffer. The Linux kernel on those boxes has 100 megs free mem and +690 megs cached. The first time a heavy query runs there's a lag as the +dataset is read into memory, but then subsequent queries fly. + +My experience has been that under Liunx (2.4.9 kernel RH7.2) the file +system caching is better performance wise for very large amounts of data +(500 Megs or more) than the postgresql shared buffers are. I.e. it would +seem that when Postgresql has a large amount of shared memory to keep +track of, it's quicker to just issue a request to the OS if the data is in +the file cache than it is to look it up in postgresql's own shared memory +buffers. The knee for me is somewhere between 32 megs and 512 megs memory +to postgresql and twice that on average or a little more to the kernel +file caches. + +> Yes, it's BAD if your business grows faster than Moores law ;-p +> +> .. unfortunately, that's been the case. Each year we've done slightly +> more than double the traffic of the previous year - and at the same time, +> as we unify all of our various data sources, the new applications that we +> develop tend to make greater and greater demands on the database server. +> There is always the option of the "big iron", but your +> cost-per-transaction shoots through the roof. Paying a 10x premium can +> really hurt. : ) + +Can you distribute your dataset across multiple machines? or is it the +kinda thing that all needs to be in one big machine? + +Well, good luck with all this. + + +From pgsql-performance-owner@postgresql.org Fri Jan 3 17:09:13 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 457234771A0 + for ; + Fri, 3 Jan 2003 17:09:11 -0500 (EST) +Received: from ns1.gnf.org (ns1.gnf.org [63.196.132.67]) + by postgresql.org (Postfix) with ESMTP id A2122477199 + for ; + Fri, 3 Jan 2003 17:09:02 -0500 (EST) +Received: from EXCHCLUSTER01.lj.gnf.org (exch01.lj.gnf.org [172.25.10.19]) + by ns1.gnf.org (8.12.3/8.12.3) with ESMTP id h03M8xMf024500 + for ; + Fri, 3 Jan 2003 14:08:59 -0800 (PST) (envelope-from hlapp@gmx.net) +Received: from gmx.net ([172.25.28.58]) by EXCHCLUSTER01.lj.gnf.org with + Microsoft SMTPSVC(5.0.2195.5329); Fri, 3 Jan 2003 14:09:02 -0800 +Date: Fri, 3 Jan 2003 11:38:50 -0800 +Subject: Re: join over 12 tables takes 3 secs to plan +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: "pgsql-performance@postgresql.org" +To: Jeff +From: Hilmar Lapp +In-Reply-To: +Message-Id: +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-OriginalArrivalTime: 03 Jan 2003 22:09:02.0333 (UTC) + FILETIME=[B92122D0:01C2B374] +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/27 +X-Sequence-Number: 674 + + +On Friday, January 3, 2003, at 09:12 AM, Jeff wrote: + +> Hmm.. This won't fix the fact the planner takes three seconds, but +> since +> it is a web application have you tried using PREPARE/EXECUTE so it only +> needs to be planned once? + +Interesting point. I'd have to look into the source code whether the +guy who wrote it actually uses JDBC PreparedStatements. I understand +that PostgreSQL from 7.3 onwards supports prepared statements (cool!). +Would the JDBC driver accompanying the dist. exploit that feature for +its PreparedStatement implementation? + + -hilmar +-- +------------------------------------------------------------- +Hilmar Lapp email: lapp at gnf.org +GNF, San Diego, Ca. 92121 phone: +1-858-812-1757 +------------------------------------------------------------- + + +From pgsql-performance-owner@postgresql.org Fri Jan 3 15:47:24 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 72B5347630B + for ; + Fri, 3 Jan 2003 15:47:23 -0500 (EST) +Received: from local.iboats.com (local.iboats.com [209.63.105.131]) + by postgresql.org (Postfix) with SMTP id 93D1E475E88 + for ; + Fri, 3 Jan 2003 15:47:22 -0500 (EST) +Received: (qmail 11791 invoked by uid 82); 3 Jan 2003 13:47:00 -0700 +Received: from nw@codon.com by local.iboats.com by uid 81 with + qmail-scanner-1.14 ( Clear:. + Processed in 0.026228 secs); 03 Jan 2003 20:47:00 -0000 +Received: from unknown (HELO WEASEL) (209.63.105.136) + by 0 with SMTP; 3 Jan 2003 13:47:00 -0700 +Message-ID: <006601c2b369$a2427ec0$88693fd1@WEASEL> +From: "Steve Wolfe" +To: +References: +Subject: Re: Question on hardware & server capacity +Date: Fri, 3 Jan 2003 13:49:33 -0700 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 6.00.2800.1106 +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/25 +X-Sequence-Number: 672 + +> Actually, free memory doesn't mean a whole lot. How much memory is +being +> used as cache by the kernel? + + Generally, a gig or so. + +> Can you distribute your dataset across multiple machines? or is it the +> kinda thing that all needs to be in one big machine? + + We're splitting the front-end across a number of machines, but all of +the various datasets are sufficiently intertwined that they all have to be +in the same database. I'm going to fiddle around with some of the +available replication options and see if they're robust enough to put them +into production. + +steve + + +From pgsql-performance-owner@postgresql.org Fri Jan 3 17:09:11 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7E3AE47719D + for ; + Fri, 3 Jan 2003 17:09:09 -0500 (EST) +Received: from ns1.gnf.org (ns1.gnf.org [63.196.132.67]) + by postgresql.org (Postfix) with ESMTP id A4DFB47719B + for ; + Fri, 3 Jan 2003 17:09:02 -0500 (EST) +Received: from EXCHCLUSTER01.lj.gnf.org (exch01.lj.gnf.org [172.25.10.19]) + by ns1.gnf.org (8.12.3/8.12.3) with ESMTP id h03M8xMh024500 + for ; + Fri, 3 Jan 2003 14:09:00 -0800 (PST) (envelope-from hlapp@gmx.net) +Received: from gmx.net ([172.25.28.58]) by EXCHCLUSTER01.lj.gnf.org with + Microsoft SMTPSVC(5.0.2195.5329); Fri, 3 Jan 2003 14:09:02 -0800 +Date: Fri, 3 Jan 2003 14:09:02 -0800 +Subject: Re: join over 12 tables takes 3 secs to plan +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: Ron Johnson , + PgSQL Performance ML +To: "scott.marlowe" +From: Hilmar Lapp +In-Reply-To: +Message-Id: +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-OriginalArrivalTime: 03 Jan 2003 22:09:02.0786 (UTC) + FILETIME=[B9664220:01C2B374] +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/26 +X-Sequence-Number: 673 + + +On Friday, January 3, 2003, at 09:01 AM, scott.marlowe wrote: + +> +> Have you tried it on firebird for linux? It's an actively developed +> rdbms +> that's open source too. If this was developed for it, it might be a +> better fit to use that for now, + +Probably it would. But honestly I'm not that keen to install the 3rd +OSS database (in addition to Oracle, MySQL, PostgreSQL), and my +sysadmins probably wouldn't be cheerfully jumping either ... + + +> and then learn postgresql under the less +> rigorous schedule of simply porting, not having to get a product out +> the +> door. + +Yes, so odd MySQL fit that bill for now ... + +> +> Is an explicit join the answer here? i.e. will the number of rows we +> get +> from each table in a single query likely to never change? If so then +> you +> could just make an explicit join and be done with it. +> + +Probably, even though the number of rows will change over time, but not +by magnitudes. It's not an application of ours though, and since we're +a bioinformatics shop, I'm not that eager to spend time hacking a +project management system's query generation code. + +Thanks for all the thoughts and comments from you and others though, I +appreciate that. + + -hilmar +-- +------------------------------------------------------------- +Hilmar Lapp email: lapp at gnf.org +GNF, San Diego, Ca. 92121 phone: +1-858-812-1757 +------------------------------------------------------------- + + +From pgsql-jdbc-owner@postgresql.org Fri Jan 3 17:16:49 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 40F56477147; Fri, 3 Jan 2003 17:16:47 -0500 (EST) +Received: from clearmetrix.com (unknown [209.92.142.67]) + by postgresql.org (Postfix) with ESMTP + id 9D830477142; Fri, 3 Jan 2003 17:16:44 -0500 (EST) +Received: from clearmetrix.com (chw.muvpn.clearmetrix.com [172.16.1.3]) + by clearmetrix.com (8.11.6/linuxconf) with ESMTP id h03MGig26985; + Fri, 3 Jan 2003 17:16:44 -0500 +Message-ID: <3E160BC0.3020900@clearmetrix.com> +Date: Fri, 03 Jan 2003 17:16:32 -0500 +From: "Charles H. Woloszynski" +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; + rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Hilmar Lapp +Cc: Jeff , + "pgsql-performance@postgresql.org" +Subject: Re: [PERFORM] join over 12 tables takes 3 secs to plan +References: +In-Reply-To: +Content-Type: text/plain; charset=ISO-8859-1; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/43 +X-Sequence-Number: 5893 + +I have been asking (and learning) about this same thing on the +PGSQL-JDBC mailing list. Apparently, there is a new driver for 7.3 that +can store the plan on the server (aka, preparing it on the server) and +re-use it. However, you need to set the PreparedStatement to do this +for each statement. So, yes, you can retain the plan but it looks like +you need to do some work to make it stick. [Also, you need to retain +the PreparedStatement, it is not cached based based on the text of the +statement, but associated with the PreparedStatement itself]. + +I think the functionality is starting to become real, but it looks like +it is starting with some limitations that might restricts its use from +be maximally realized until 7.4 (or beyond). + +Charlie + + + + +Hilmar Lapp wrote: + +> +> On Friday, January 3, 2003, at 09:12 AM, Jeff wrote: +> +>> Hmm.. This won't fix the fact the planner takes three seconds, but since +>> it is a web application have you tried using PREPARE/EXECUTE so it only +>> needs to be planned once? +> +> +> Interesting point. I'd have to look into the source code whether the +> guy who wrote it actually uses JDBC PreparedStatements. I understand +> that PostgreSQL from 7.3 onwards supports prepared statements (cool!). +> Would the JDBC driver accompanying the dist. exploit that feature for +> its PreparedStatement implementation? +> +> -hilmar + + +-- + + +Charles H. Woloszynski + +ClearMetrix, Inc. +115 Research Drive +Bethlehem, PA 18015 + +tel: 610-419-2210 x400 +fax: 240-371-3256 +web: www.clearmetrix.com + + + + + + +From pgsql-performance-owner@postgresql.org Fri Jan 3 17:24:11 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 43B87477174 + for ; + Fri, 3 Jan 2003 17:24:10 -0500 (EST) +Received: from ns1.gnf.org (ns1.gnf.org [63.196.132.67]) + by postgresql.org (Postfix) with ESMTP id 34355477103 + for ; + Fri, 3 Jan 2003 17:22:48 -0500 (EST) +Received: from EXCHCLUSTER01.lj.gnf.org (exch01.lj.gnf.org [172.25.10.19]) + by ns1.gnf.org (8.12.3/8.12.3) with ESMTP id h03MMjMf024545 + for ; + Fri, 3 Jan 2003 14:22:45 -0800 (PST) (envelope-from hlapp@gmx.net) +Received: from gmx.net ([172.25.28.58]) by EXCHCLUSTER01.lj.gnf.org with + Microsoft SMTPSVC(5.0.2195.5329); Fri, 3 Jan 2003 14:22:48 -0800 +Date: Fri, 3 Jan 2003 14:22:49 -0800 +Subject: Re: join over 12 tables takes 3 secs to plan +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: Jeff , + "pgsql-performance@postgresql.org" +To: "Charles H. Woloszynski" +From: Hilmar Lapp +In-Reply-To: <3E160BC0.3020900@clearmetrix.com> +Message-Id: +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-OriginalArrivalTime: 03 Jan 2003 22:22:48.0864 (UTC) + FILETIME=[A5C7C200:01C2B376] +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/29 +X-Sequence-Number: 676 + + +On Friday, January 3, 2003, at 02:16 PM, Charles H. Woloszynski wrote: + +> Also, you need to retain the PreparedStatement, it is not cached based +> based on the text of the +> statement, but associated with the PreparedStatement itself + +I think that's normal. I don't recall the JDBC spec saying that you +have a chance the server will remember that you created a +PreparedStatement for the same query text before. You have to cache the +PreparedStatement object in your app, not the query string. + +BTW that's the same for perl/DBI. At least for Oracle. + + -hilmar +-- +------------------------------------------------------------- +Hilmar Lapp email: lapp at gnf.org +GNF, San Diego, Ca. 92121 phone: +1-858-812-1757 +------------------------------------------------------------- + + +From pgsql-performance-owner@postgresql.org Sat Jan 4 08:33:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 32003475C15 + for ; + Sat, 4 Jan 2003 08:33:16 -0500 (EST) +Received: from albert.auore.net (80-24-20-197.uc.nombres.ttd.es + [80.24.20.197]) + by postgresql.org (Postfix) with SMTP id C0D0147590C + for ; + Sat, 4 Jan 2003 08:33:13 -0500 (EST) +Received: (qmail 1772 invoked by uid 1000); 4 Jan 2003 13:31:51 -0000 +From: Albert Cervera Areny +Subject: Fwd: Stock update like application +Date: Sat, 4 Jan 2003 14:31:51 +0100 +User-Agent: KMail/1.5 +To: pgsql-performance@postgresql.org +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-15" +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +Message-Id: <200301041431.51423.albertca@jazzfree.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/30 +X-Sequence-Number: 677 + +Hi! + I'm developing a small application which I'd like to be as fast as + possible. The program simply receives an order by modem and has to give an + answer with the products my enterprise will be able to send them. The number + of products could be as much as 300-400 and I don't want to make my clients + put I high time-out before the answer is sended. + +I do also need to use transactions as I start calculating before the whole +order has been received and if an error occurs everything has to be rolled +back. + +Under this circumstances which way do you think it would be faster? + +- Make a sequence for each product (we're talking about 20000 available +products so I think it is very big but it might give a really fast answer). + +- Using standard SQL queries: SELECT the product, and if there are enough +units UPDATE to decrease the number of available ones. (This one I suppose +it's not very fast as two queries need to be processed for each product). + +- Using a CURSOR or something like this which I'm not used to but I've seen + in the examples. + +Should I have the queries saved in the database to encrease performance? + +I hope I explained well enough :-) Thanks in advance! + +From pgsql-performance-owner@postgresql.org Sun Jan 5 21:25:06 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6F205476BDA + for ; + Sun, 5 Jan 2003 21:25:05 -0500 (EST) +Received: from pineapple.ji.justsystem.co.jp (pineapple.ji.justsystem.co.jp + [210.169.202.64]) + by postgresql.org (Postfix) with ESMTP id C9EFF476BD6 + for ; + Sun, 5 Jan 2003 21:25:04 -0500 (EST) +Received: from vrs01.b1.justsystem.co.jp ([10.4.1.51]) + by pineapple.ji.justsystem.co.jp with smtp (Exim 3.33 #1) + id 18VMxF-0001mX-00 + for pgsql-performance@postgresql.org; Mon, 06 Jan 2003 11:25:29 +0900 +Received: from justsystem.co.jp ([10.4.1.38]) + by vrs01.b1.justsystem.co.jp (NAVGW 2.5.1.19) with SMTP id + M2003010611250713463 + for ; Mon, 06 Jan 2003 11:25:07 +0900 +Received: (qmail 10823 invoked from network); 6 Jan 2003 11:25:07 +0900 +Received: from bat.b1.justsystem.co.jp (10.4.1.37) + by owl.b1.justsystem.co.jp with SMTP; 6 Jan 2003 11:25:07 +0900 +Received: from yutaka_inada by bat.b1.justsystem.co.jp (8.8.8/3.6W) id + LAA26427; Mon, 6 Jan 2003 11:21:46 +0900 (JST) +From: yutaka_inada@justsystem.co.jp +MIME-Version: 1.0 +Date: Mon, 6 Jan 2003 11:27:17 +0900 +Subject: Re: executing pgsql on Xeon-dual machine +To: Tom Lane +Cc: pgsql-performance@postgresql.org +Message-ID: +Content-Type: text/plain; charset=iso-2022-jp +Content-Transfer-Encoding: 7bit +In-Reply-To: <25730.1041014158@sss.pgh.pa.us> +References: <25730.1041014158@sss.pgh.pa.us> +X-Mailer: JsvMail 4.0 (Shuriken Pro2) +X-Priority: 3 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/31 +X-Sequence-Number: 678 + +Thank you, Tom, + +Tom Lane $B!'(B +> +> If you set fsync off, how do the pgbench results change? + +I'll try it. + +--- +Yutaka Inada [Justsystem Corporation] + +From pgsql-performance-owner@postgresql.org Mon Jan 6 05:59:40 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id AC4D447606A + for ; + Mon, 6 Jan 2003 05:59:38 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 17A43475C98 + for ; + Mon, 6 Jan 2003 05:59:38 -0500 (EST) +Received: from klaster.net (pa236.krakow.cvx.ppp.tpnet.pl [213.76.36.236]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP id 51AD12B21C + for ; + Mon, 6 Jan 2003 11:58:10 +0100 (CET) +Message-ID: <3E196277.5020904@klaster.net> +Date: Mon, 06 Jan 2003 12:03:19 +0100 +From: Tomasz Myrta +User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; + rv:1.2b) Gecko/20021016 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: PgSQL Performance ML +Subject: views vs pl/pgsql +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/32 +X-Sequence-Number: 679 + +Hi +1. I have plpgsql function having only one query returning 1 value. This +query joins some tables. I read, that plpgsql function saves execution +plan for all queries inside one database connection. + +2. Instead of this I can create a view returning one row. How does +postgres work with views? When the plan is being created? What happens +to views which don't have explicit joins? What happens if I create index +on tables after creating a view? + +Which one is better and when? + +Regards, +Tomasz Myrta + + +From pgsql-performance-owner@postgresql.org Mon Jan 6 14:12:14 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 63EA6476E32 + for ; + Mon, 6 Jan 2003 14:12:13 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 2F225476DD1 + for ; + Mon, 6 Jan 2003 14:12:12 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2305182; Mon, 06 Jan 2003 11:12:15 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: "Steve Wolfe" , +Subject: Re: Question on hardware & server capacity +Date: Mon, 6 Jan 2003 11:14:50 -0800 +X-Mailer: KMail [version 1.4] +References: + <006601c2b369$a2427ec0$88693fd1@WEASEL> +In-Reply-To: <006601c2b369$a2427ec0$88693fd1@WEASEL> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301061114.50830.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/33 +X-Sequence-Number: 680 + + +Steve, + +> We're splitting the front-end across a number of machines, but all of +> the various datasets are sufficiently intertwined that they all have to be +> in the same database. I'm going to fiddle around with some of the +> available replication options and see if they're robust enough to put them +> into production. + +2 other suggestions: + +1. Both PostgreSQL Inc. and Command Prompt Inc. have some sort of pay-for H= +A=20 +solution for Postgres. Paying them may end up being cheaper than=20 +improvising this yourself. + +2. Zapatec Inc. has acheived impressive performance gains by putting the=20 +database on a high-speed, HA gigabit NAS server and having a few "client=20 +servers" handle incoming queries. You may want to experiment along thes= +e=20 +lines. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-general-owner@postgresql.org Mon Jan 6 22:33:04 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 50044477289; Mon, 6 Jan 2003 22:33:03 -0500 (EST) +Received: from voyager.corporate.connx.com (unknown [209.20.248.131]) + by postgresql.org (Postfix) with ESMTP + id 7C4354769E7; Mon, 6 Jan 2003 22:32:48 -0500 (EST) +content-class: urn:content-classes:message +Subject: Re: PostgreSQL and memory usage +MIME-Version: 1.0 +Content-Type: text/plain; + charset="us-ascii" +Content-Transfer-Encoding: quoted-printable +Date: Mon, 6 Jan 2003 19:32:52 -0800 +X-MimeOLE: Produced By Microsoft Exchange V6.0.6249.0 +Message-ID: + +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [GENERAL] PostgreSQL and memory usage +Thread-Index: AcK1/R1mXBhJY5VgR9mCHWb6ZWRYOQAACaqw +From: "Dann Corbit" +To: "Tom Lane" +Cc: , +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/207 +X-Sequence-Number: 35328 + +> -----Original Message----- +> From: Tom Lane [mailto:tgl@sss.pgh.pa.us]=20 +> Sent: Monday, January 06, 2003 7:30 PM +> To: Dann Corbit +> Cc: pgsql-hackers@postgresql.org; pgsql-general@postgresql.org +> Subject: Re: [GENERAL] PostgreSQL and memory usage=20 +>=20 +>=20 +> "Dann Corbit" writes: +> > I have a machine with 4 CPU's and 2 gigabytes of physical=20 +> ram. I would=20 +> > like to get PostgreSQL to use as much memory as possible. I can't=20 +> > seem to get PostgreSQL to use more than 100 megabytes or so. +>=20 +> You should not assume that more is necessarily better. +>=20 +> In many practical situations, it's better to leave the=20 +> majority of RAM free for kernel disk caching. + +In any case, I would like to know what knobs and dials are available to +turn and what each of them means. +In at least one instance, the whole database should fit into memory. I +would think that would be faster than any sort of kernel disk caching. + +From pgsql-performance-owner@postgresql.org Tue Jan 7 06:56:35 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2D7B94768CC + for ; + Tue, 7 Jan 2003 06:56:34 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 8778B476745 + for ; + Tue, 7 Jan 2003 06:56:33 -0500 (EST) +Received: from klaster.net (pe241.krakow.cvx.ppp.tpnet.pl [213.76.40.241]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP + id 7DDA02B21C; Tue, 7 Jan 2003 12:54:53 +0100 (CET) +Message-ID: <3E1AC14C.7010104@klaster.net> +Date: Tue, 07 Jan 2003 13:00:12 +0100 +From: Tomasz Myrta +User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; + rv:1.2b) Gecko/20021016 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Achilleus Mantzios +Cc: pgsql-performance@postgresql.org +Subject: Re: [SQL] 7.3.1 index use / performance +References: +In-Reply-To: +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/35 +X-Sequence-Number: 682 + +Achilleus Mantzios wrote: + + + > it has indexes: + > Indexes: noonf_date btree (report_date), + > noonf_logno btree (log_no), + > noonf_rotation btree (rotation text_ops), + > noonf_vcode btree (v_code), + > noonf_voyageno btree (voyage_no) + > + + + > + > +------------------------------------------------------------------------------------------------------------------- + > Index Scan using noonf_date on noon (cost=0.00..4.46 rows=1 width=39) + > (actual time=0.27..52.89 rows=259 loops=1) + > Index Cond: ((report_date >= '2002-01-07'::date) AND (report_date <= + > '2003-01-07'::date)) + > Filter: ((v_code = '4500'::character varying) AND (rotation = 'NOON + > '::character varying)) + > Total runtime: 53.98 msec + > (4 rows) + + +Maybe it is not an answer to your question, but why don't you help +Postgres by yourself? +For this kind of queries it's better to drop index on report_date - your +report period is one year and answer to this condition is 10% records (I +suppose) +It would be better to change 2 indexes on v_code and rotation into one +index based on both fields. +What kind of queries do you have? How many records returns each "where" +condition? Use indexes on fields, on which condition result in smallest +amount of rows. + +Regards, +Tomasz Myrta + + +From pgsql-general-owner@postgresql.org Tue Jan 7 10:27:47 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id CC93C475A3F; Tue, 7 Jan 2003 10:27:46 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP + id 3213247628F; Tue, 7 Jan 2003 10:27:45 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 6D5C5D605; Tue, 7 Jan 2003 07:27:49 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 6316E5C04; Tue, 7 Jan 2003 07:27:49 -0800 (PST) +Date: Tue, 7 Jan 2003 07:27:49 -0800 (PST) +From: Stephan Szabo +To: Achilleus Mantzios +Cc: , + , +Subject: Re: [PERFORM] 7.3.1 index use / performance +In-Reply-To: +Message-ID: <20030107072146.L61341-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/232 +X-Sequence-Number: 35353 + + +On Tue, 7 Jan 2003, Achilleus Mantzios wrote: + +> i am just in the stage of having migrated my test system to 7.3.1 +> and i am experiencing some performance problems. +> +> i have a table "noon" +> Table "public.noon" +> Column | Type | Modifiers +> ------------------------+------------------------+----------- +> v_code | character varying(4) | +> log_no | bigint | +> report_date | date | +> report_time | time without time zone | +> voyage_no | integer | +> charterer | character varying(12) | +> port | character varying(24) | +> duration | character varying(4) | +> rotation | character varying(9) | +> ...... +> +> with a total of 278 columns. +> +> it has indexes: +> Indexes: noonf_date btree (report_date), +> noonf_logno btree (log_no), +> noonf_rotation btree (rotation text_ops), +> noonf_vcode btree (v_code), +> noonf_voyageno btree (voyage_no) +> +> On the test 7.3.1 system (a FreeBSD 4.7-RELEASE-p2, Celeron 1.2GHz +> 400Mb, with 168Mb for pgsql), +> i get: +> dynacom=# EXPLAIN ANALYZE select +> FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where +> v_code='4500' and rotation='NOON ' and report_date between +> '2002-01-07' and '2003-01-07'; +> QUERY PLAN +> + +> ------------------------------------------------------------------------------------------------------------------- +> Index Scan using noonf_date on noon (cost=0.00..4.46 rows=1 width=39) +> (actual time=0.27..52.89 rows=259 loops=1) + + +> Index Scan using noonf_vcode on noon (cost=0.00..3122.88 rows=1 +> width=39) (actual time=0.16..13.92 rows=259 loops=1) + + +What do the statistics for the three columns actually look like and what +are the real distributions and counts like? +Given an estimated cost of around 4 for the first scan, my guess would be +that it's not expecting alot of rows between 2002-01-07 and 2003-01-07 +which would make that a reasonable plan. + + +From pgsql-general-owner@postgresql.org Tue Jan 7 06:31:32 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 2A00E475ADE; Tue, 7 Jan 2003 06:31:31 -0500 (EST) +Received: from matrix.gatewaynet.com (unknown [217.19.69.50]) + by postgresql.org (Postfix) with ESMTP + id 098B04758C9; Tue, 7 Jan 2003 06:31:30 -0500 (EST) +Received: from matrix.gatewaynet.com (matrix.gatewaynet.com [217.19.69.50]) + by matrix.gatewaynet.com (8.12.5/8.12.5) with ESMTP id h07FdvXR008171; + Tue, 7 Jan 2003 13:39:57 -0200 +Received: from localhost (achill@localhost) + by matrix.gatewaynet.com (8.12.5/8.12.5/Submit) with ESMTP id + h07FdvVA008167; Tue, 7 Jan 2003 13:39:57 -0200 +Date: Tue, 7 Jan 2003 13:39:57 -0200 (GMT+2) +From: Achilleus Mantzios +To: pgsql-performance@postgresql.org, , + +Subject: 7.3.1 index use / performance +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/219 +X-Sequence-Number: 35340 + +Hi, + +i am just in the stage of having migrated my test system to 7.3.1 +and i am experiencing some performance problems. + +i have a table "noon" + Table "public.noon" + Column | Type | Modifiers +------------------------+------------------------+----------- + v_code | character varying(4) | + log_no | bigint | + report_date | date | + report_time | time without time zone | + voyage_no | integer | + charterer | character varying(12) | + port | character varying(24) | + duration | character varying(4) | + rotation | character varying(9) | +...... + +with a total of 278 columns. + +it has indexes: +Indexes: noonf_date btree (report_date), + noonf_logno btree (log_no), + noonf_rotation btree (rotation text_ops), + noonf_vcode btree (v_code), + noonf_voyageno btree (voyage_no) + +On the test 7.3.1 system (a FreeBSD 4.7-RELEASE-p2, Celeron 1.2GHz +400Mb, with 168Mb for pgsql), +i get: +dynacom=# EXPLAIN ANALYZE select +FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where +v_code='4500' and rotation='NOON ' and report_date between +'2002-01-07' and '2003-01-07'; + QUERY PLAN + +------------------------------------------------------------------------------------------------------------------- + Index Scan using noonf_date on noon (cost=0.00..4.46 rows=1 width=39) +(actual time=0.27..52.89 rows=259 loops=1) + Index Cond: ((report_date >= '2002-01-07'::date) AND (report_date <= +'2003-01-07'::date)) + Filter: ((v_code = '4500'::character varying) AND (rotation = 'NOON +'::character varying)) + Total runtime: 53.98 msec +(4 rows) + +after i drop the noonf_date index i actually get better performance +cause the backend uses now the more appropriate index noonf_vcode : + +dynacom=# EXPLAIN ANALYZE select +FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where +v_code='4500' and rotation='NOON ' and report_date between +'2002-01-07' and '2003-01-07'; + QUERY PLAN + +----------------------------------------------------------------------------------------------------------------------------------------- + Index Scan using noonf_vcode on noon (cost=0.00..3122.88 rows=1 +width=39) (actual time=0.16..13.92 rows=259 loops=1) + Index Cond: (v_code = '4500'::character varying) + Filter: ((rotation = 'NOON '::character varying) AND (report_date +>= '2002-01-07'::date) AND (report_date <= '2003-01-07'::date)) + Total runtime: 14.98 msec +(4 rows) + +On the pgsql 7.2.3 development system (a RH linux 2.4.7, PIII 1 GHz, +1Mb, with 168M for pgsql), i always get the right index use: + +dynacom=# EXPLAIN ANALYZE select +FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where +v_code='4500' and rotation='NOON ' and report_date between +'2002-01-07' and '2003-01-07'; +NOTICE: QUERY PLAN: + +Index Scan using noonf_vcode on noon (cost=0.00..3046.38 rows=39 +width=39) (actual time=0.09..8.55 rows=259 loops=1) +Total runtime: 8.86 msec + +EXPLAIN + +Is something i am missing?? +Is this reasonable behaviour?? + +P.S. +Yes i have vaccumed analyzed both systems before the queries were issued. +================================================================== +Achilleus Mantzios +S/W Engineer +IT dept +Dynacom Tankers Mngmt +Nikis 4, Glyfada +Athens 16610 +Greece +tel: +30-10-8981112 +fax: +30-10-8981877 +email: achill@matrix.gatewaynet.com + mantzios@softlab.ece.ntua.gr + + + +From pgsql-general-owner@postgresql.org Tue Jan 7 07:13:02 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id D7CB647699E; Tue, 7 Jan 2003 07:13:01 -0500 (EST) +Received: from matrix.gatewaynet.com (unknown [217.19.69.50]) + by postgresql.org (Postfix) with ESMTP + id A525647698B; Tue, 7 Jan 2003 07:12:58 -0500 (EST) +Received: from matrix.gatewaynet.com (matrix.gatewaynet.com [217.19.69.50]) + by matrix.gatewaynet.com (8.12.5/8.12.5) with ESMTP id h07GLJXR008348; + Tue, 7 Jan 2003 14:21:19 -0200 +Received: from localhost (achill@localhost) + by matrix.gatewaynet.com (8.12.5/8.12.5/Submit) with ESMTP id + h07GLJth008344; Tue, 7 Jan 2003 14:21:19 -0200 +Date: Tue, 7 Jan 2003 14:21:19 -0200 (GMT+2) +From: Achilleus Mantzios +To: Tomasz Myrta +Cc: pgsql-performance@postgresql.org, , + +Subject: Re: [SQL] 7.3.1 index use / performance +In-Reply-To: <3E1AC14C.7010104@klaster.net> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/222 +X-Sequence-Number: 35343 + +On Tue, 7 Jan 2003, Tomasz Myrta wrote: + +> Maybe it is not an answer to your question, but why don't you help +> Postgres by yourself? + +Thanx, + +i dont think that the issue here is to help postgresql by myself. +I can always stick to 7.2.3, or use indexes that 7.3.1 will +acknowledge, like noonf_vcode_date on noon (v_code,report_date). +(unfortunately when i create the above noonf_vcode_date index, it is only +used until +the next vacuum analyze, hackers is this an issue too???), +but these options are not interesting from a postgresql perspective :) + +> For this kind of queries it's better to drop index on report_date - your +> report period is one year and answer to this condition is 10% records (I +> suppose) + +I cannot drop the index on the report_date since a lot of other queries +need it. + +> It would be better to change 2 indexes on v_code and rotation into one +> index based on both fields. +> What kind of queries do you have? How many records returns each "where" +> condition? Use indexes on fields, on which condition result in smallest +> amount of rows. +> +> Regards, +> Tomasz Myrta +> + +================================================================== +Achilleus Mantzios +S/W Engineer +IT dept +Dynacom Tankers Mngmt +Nikis 4, Glyfada +Athens 16610 +Greece +tel: +30-10-8981112 +fax: +30-10-8981877 +email: achill@matrix.gatewaynet.com + mantzios@softlab.ece.ntua.gr + + +From pgsql-general-owner@postgresql.org Tue Jan 7 11:30:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id A20C247614E; Tue, 7 Jan 2003 11:30:16 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 23CE24771B4; Tue, 7 Jan 2003 11:29:48 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h07GTm0U013844; + Tue, 7 Jan 2003 11:29:48 -0500 (EST) +To: Achilleus Mantzios +Cc: Stephan Szabo , + pgsql-performance@postgresql.org, pgsql-general@postgresql.org, + pgsql-sql@postgresql.org +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance +In-reply-to: +References: +Comments: In-reply-to Achilleus Mantzios + message dated "Tue, 07 Jan 2003 18:27:32 -0200" +Date: Tue, 07 Jan 2003 11:29:48 -0500 +Message-ID: <13843.1041956988@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/237 +X-Sequence-Number: 35358 + +Achilleus Mantzios writes: +> About the stats on these 3 columns i get: + +Does 7.2 generate the same stats? (minus the schemaname of course) + +Also, I would like to see the results of these queries on both versions, +so that we can see what the planner thinks the index selectivity is: + +EXPLAIN ANALYZE select * from noon where +v_code='4500'; + +EXPLAIN ANALYZE select * from noon where +report_date between '2002-01-07' and '2003-01-07'; + + regards, tom lane + +From pgsql-general-owner@postgresql.org Tue Jan 7 12:04:52 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 4697E476313; Tue, 7 Jan 2003 12:04:51 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP + id 9FD204762C0; Tue, 7 Jan 2003 12:04:50 -0500 (EST) +Received: from css120.ihs.com (css120.ihs.com [170.207.105.120]) + by mail1.ihs.com (8.12.6/8.12.6) with ESMTP id h07H0uB2008056; + Tue, 7 Jan 2003 10:01:00 -0700 (MST) +Date: Tue, 7 Jan 2003 09:55:30 -0700 (MST) +From: "scott.marlowe" +To: Dann Corbit +Cc: Tom Lane , , + +Subject: Re: PostgreSQL and memory usage +In-Reply-To: + +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-MailScanner: Found to be clean +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/239 +X-Sequence-Number: 35360 + + +Hi Dann, I took hackers out of the list as this isn't really a hacking +issue, but I added in performance as this definitely applies there. + +There are generally two areas of a database server you have to reconfigure +to use that extra memory. The first is the kernel's shared memory +settings. + +On a linux box that has sysconf installed this is quite easy. If it isn't +installed, install it, as it's much easier to manipulate your kernel's +settings using sysctl than it is with editing rc.local. + +First, get root. Then, use 'sysctl -a|grep shm' to get a list of all the +shared memory settings handled by sysctl. + +On a default redhat install, we'll get something like this: + +kernel.shmmni = 4096 +kernel.shmall = 2097152 +kernel.shmmax = 33554432 + +On my bigger box, it's been setup to have this: + +kernel.shmmni = 4096 +kernel.shmall = 32000000 +kernel.shmmax = 256000000 + +To make changes that stick around, edit the /etc/sysctl.conf file to have +lines that look kinda like those above. To make the changes to the +/etc/sysctl.conf file take effect, use 'sysctl -p'. + +Next, as the postgres user, edit $PGDATA/postgresql.conf and increase the +number of shared buffers. On most postgresql installations this number is +multiplied by 8k to get the amount of ram being allocated, since +postgresql allocates share buffers in blocks the same size as what it uses +on the dataset. To allocate 256 Megs of buffers (that's what I use, seems +like a nice large chunk, but doesn't starve my other processes or system +file cache) set it to 32768. + +Be careful how big you make your sort size. I haven't seen a great +increase in speed on anything over 8 or 16 megs, while memory usage can +skyrocket under heavy parallel load with lots of sorts, since sort memory +is PER SORT maximum. + +Then do the old pg_ctl reload and you should be cooking with gas. + + +From pgsql-general-owner@postgresql.org Tue Jan 7 12:09:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 9234C476745; Tue, 7 Jan 2003 12:09:53 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 852AD475ED4; Tue, 7 Jan 2003 12:09:50 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h07H9L0U014257; + Tue, 7 Jan 2003 12:09:21 -0500 (EST) +To: "scott.marlowe" +Cc: Dann Corbit , pgsql-general@postgresql.org, + pgsql-performance@postgresql.org +Subject: Re: PostgreSQL and memory usage +In-reply-to: +References: +Comments: In-reply-to "scott.marlowe" + message dated "Tue, 07 Jan 2003 09:55:30 -0700" +Date: Tue, 07 Jan 2003 12:09:21 -0500 +Message-ID: <14256.1041959361@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/240 +X-Sequence-Number: 35361 + +"scott.marlowe" writes: +> Then do the old pg_ctl reload and you should be cooking with gas. + +One correction: altering the number of shared buffers requires an actual +postmaster restart. + + regards, tom lane + +From pgsql-general-owner@postgresql.org Tue Jan 7 12:44:16 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 2CC43475D99; Tue, 7 Jan 2003 12:44:15 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 6F3484759BD; Tue, 7 Jan 2003 12:44:14 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h07HiG0U014599; + Tue, 7 Jan 2003 12:44:16 -0500 (EST) +To: Achilleus Mantzios +Cc: Stephan Szabo , + pgsql-performance@postgresql.org, pgsql-general@postgresql.org, + pgsql-sql@postgresql.org +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance +In-reply-to: +References: +Comments: In-reply-to Achilleus Mantzios + message dated "Tue, 07 Jan 2003 19:05:22 -0200" +Date: Tue, 07 Jan 2003 12:44:16 -0500 +Message-ID: <14598.1041961456@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/242 +X-Sequence-Number: 35363 + +Achilleus Mantzios writes: +>> Also, I would like to see the results of these queries on both versions, +>> so that we can see what the planner thinks the index selectivity is: +>> +> [ data supplied ] + +There is something really, really bizarre going on there. You have + +dynacom=# EXPLAIN ANALYZE select * from noon where report_date between '2002-01-07' and '2003-01-07'; + QUERY PLAN + +--------------------------------------------------------------------------------------------------------------------------------- + Index Scan using noonf_date on noon (cost=0.00..15919.50 rows=11139 width=1974) (actual time=2.05..13746.17 rows=7690 loops=1) + Index Cond: ((report_date >= '2002-01-07'::date) AND (report_date <= '2003-01-07'::date)) + Total runtime: 13775.48 msec +(3 rows) + +and from your earlier message + +dynacom=# EXPLAIN ANALYZE select FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where +v_code='4500' and rotation='NOON ' and report_date between '2002-01-07' and '2003-01-07'; + QUERY PLAN + +------------------------------------------------------------------------------------------------------------------- + Index Scan using noonf_date on noon (cost=0.00..4.46 rows=1 width=39) (actual time=0.27..52.89 rows=259 loops=1) + Index Cond: ((report_date >= '2002-01-07'::date) AND (report_date <= '2003-01-07'::date)) + Filter: ((v_code = '4500'::character varying) AND (rotation = 'NOON'::character varying)) + Total runtime: 53.98 msec +(4 rows) + +There is no way that adding the filter condition should have reduced the +estimated runtime for this plan --- reducing the estimated number of +output rows, yes, but not the runtime. And in fact I can't duplicate +that when I try it here. I did this on 7.3.1: + +regression=# create table noon (v_code character varying(4) , +regression(# report_date date , +regression(# rotation character varying(9)); +CREATE TABLE +regression=# create index noonf_date on noon(report_date); +CREATE INDEX +regression=# EXPLAIN select * from noon where report_date between +regression-# '2002-01-07' and '2003-01-07'; + QUERY PLAN + +--------------------------------------------------------------------------------------------- + Index Scan using noonf_date on noon (cost=0.00..17.08 rows=5 width=25) + Index Cond: ((report_date >= '2002-01-07'::date) AND (report_date <= '2003-01-07'::date)) +(2 rows) + +regression=# explain select * from noon where +regression-# v_code='4500' and rotation='NOON ' and report_date between +regression-# '2002-01-07' and '2003-01-07'; + QUERY PLAN + +-------------------------------------------------------------------------------- +------------------ + Index Scan using noonf_date on noon (cost=0.00..17.11 rows=1 width=25) + Index Cond: ((report_date >= '2002-01-07'::date) AND (report_date <= '2003-01-07'::date)) + Filter: ((v_code = '4500'::character varying) AND (rotation = 'NOON '::character varying)) +(3 rows) + +Note that the cost went up, not down. + +I am wondering about a compiler bug, or some other peculiarity on your +platform. Can anyone else using FreeBSD try the above experiment and +see if they get different results from mine on 7.3.* (or CVS tip)? + + regards, tom lane + +From pgsql-general-owner@postgresql.org Tue Jan 7 13:22:24 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id BCAC7477275; Tue, 7 Jan 2003 13:22:23 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 63B9C476745; Tue, 7 Jan 2003 13:22:20 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h07IMF0U015502; + Tue, 7 Jan 2003 13:22:16 -0500 (EST) +To: Achilleus Mantzios +Cc: pgsql-general@postgresql.org, pgsql-sql@postgresql.org +Subject: Re: 7.3.1 function problem: ERROR: cache lookup failed for type 0 +In-reply-to: +References: +Comments: In-reply-to Achilleus Mantzios + message dated "Tue, 07 Jan 2003 19:55:33 -0200" +Date: Tue, 07 Jan 2003 13:22:15 -0500 +Message-ID: <15501.1041963735@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/245 +X-Sequence-Number: 35366 + +Achilleus Mantzios writes: +> Hi i had written a C function to easily convert an int4 to its +> equivalent 1x1 int4[] array. + +Does your function know about filling in the elemtype field that was +recently added to struct ArrayType? + + regards, tom lane + +From pgsql-general-owner@postgresql.org Tue Jan 7 13:41:40 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 494F1475ED4; Tue, 7 Jan 2003 13:41:40 -0500 (EST) +Received: from joeconway.com (unknown [63.210.180.150]) + by postgresql.org (Postfix) with ESMTP + id 79DB7477369; Tue, 7 Jan 2003 13:41:03 -0500 (EST) +Received: from [206.19.64.3] (account jconway HELO joeconway.com) + by joeconway.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP-TLS id 1554268; Tue, 07 Jan 2003 11:14:44 -0800 +Message-ID: <3E1B1ED7.7060704@joeconway.com> +Date: Tue, 07 Jan 2003 10:39:19 -0800 +From: Joe Conway +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; + rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Achilleus Mantzios +Cc: Tom Lane , pgsql-general@postgresql.org, + pgsql-sql@postgresql.org +Subject: Re: 7.3.1 function problem: ERROR: cache lookup failed +References: +In-Reply-To: +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/249 +X-Sequence-Number: 35370 + +Achilleus Mantzios wrote: +> On Tue, 7 Jan 2003, Tom Lane wrote: +>>Does your function know about filling in the elemtype field that was +>>recently added to struct ArrayType? +> +> She has no clue :) +> +> Any pointers would be great. + +See construct_array() in src/backend/utils/adt/arrayfuncs.c. + +HTH, + +Joe + + +From pgsql-general-owner@postgresql.org Tue Jan 7 13:40:05 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 48977475D99; Tue, 7 Jan 2003 13:40:01 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 84FBA475AD7; Tue, 7 Jan 2003 13:40:00 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h07Idv0U019586; + Tue, 7 Jan 2003 13:39:57 -0500 (EST) +To: Achilleus Mantzios +Cc: Stephan Szabo , + pgsql-performance@postgresql.org, pgsql-general@postgresql.org, + pgsql-sql@postgresql.org +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance +In-reply-to: +References: +Comments: In-reply-to Achilleus Mantzios + message dated "Tue, 07 Jan 2003 20:38:17 -0200" +Date: Tue, 07 Jan 2003 13:39:57 -0500 +Message-ID: <19585.1041964797@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/248 +X-Sequence-Number: 35369 + +Achilleus Mantzios writes: +> My case persists: +> After clean install of the database, and after vacuum analyze, +> i get + +Um ... is it persisting? That looks like it's correctly picked the +vcode index this time. Strange behavior though. By "clean install" +do you mean you rebuilt Postgres, or just did dropdb/createdb/reload +data? + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Jan 7 13:45:45 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 566DC47739D; Tue, 7 Jan 2003 13:45:41 -0500 (EST) +Received: from jester.senspire.com (unknown [216.208.117.7]) + by postgresql.org (Postfix) with ESMTP + id 9F44F477275; Tue, 7 Jan 2003 13:45:26 -0500 (EST) +Received: from [127.0.0.1] (localhost [127.0.0.1]) + by jester.senspire.com (8.12.6/8.12.6) with ESMTP id h07IjE39039903; + Tue, 7 Jan 2003 13:45:15 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: [SQL] 7.3.1 index use / performance +From: Rod Taylor +To: Tom Lane +Cc: Achilleus Mantzios , + Stephan Szabo , + Pgsql Performance , + pgsql-general@postgresql.org, pgsql-sql@postgresql.org +In-Reply-To: <14598.1041961456@sss.pgh.pa.us> +References: + <14598.1041961456@sss.pgh.pa.us> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-GwJlq1zAooSOa7CkghQM" +Organization: +Message-Id: <1041965114.39376.39.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 07 Jan 2003 13:45:14 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/47 +X-Sequence-Number: 694 + +--=-GwJlq1zAooSOa7CkghQM +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +> I am wondering about a compiler bug, or some other peculiarity on your +> platform. Can anyone else using FreeBSD try the above experiment and +> see if they get different results from mine on 7.3.* (or CVS tip)? + +On FreeBSD 4.7 I received the exact same results as Tom using the +statements shown by Tom. + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-GwJlq1zAooSOa7CkghQM +Content-Type: application/pgp-signature; name=signature.asc +Content-Description: This is a digitally signed message part + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (FreeBSD) + +iD8DBQA+GyA66DETLow6vwwRAmgbAJoCIJc0hYgyczkGSd8Stdlg64UebgCeNmSg +LdAAH0L9w+S1nMDrb+fMrQY= +=bljF +-----END PGP SIGNATURE----- + +--=-GwJlq1zAooSOa7CkghQM-- + + +From pgsql-general-owner@postgresql.org Tue Jan 7 14:26:16 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 18BC74762A4 + for ; + Tue, 7 Jan 2003 14:26:14 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id C764647607B + for ; + Tue, 7 Jan 2003 14:26:11 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h07JQ80U019890; + Tue, 7 Jan 2003 14:26:08 -0500 (EST) +To: Rod Taylor +Cc: Achilleus Mantzios , + Stephan Szabo , + Pgsql Performance , + pgsql-general@postgresql.org, pgsql-sql@postgresql.org +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance +In-reply-to: <1041965114.39376.39.camel@jester> +References: + <14598.1041961456@sss.pgh.pa.us> <1041965114.39376.39.camel@jester> +Comments: In-reply-to Rod Taylor + message dated "07 Jan 2003 13:45:14 -0500" +Date: Tue, 07 Jan 2003 14:26:08 -0500 +Message-ID: <19889.1041967568@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/252 +X-Sequence-Number: 35373 + +Rod Taylor writes: +>> I am wondering about a compiler bug, or some other peculiarity on your +>> platform. Can anyone else using FreeBSD try the above experiment and +>> see if they get different results from mine on 7.3.* (or CVS tip)? + +> On FreeBSD 4.7 I received the exact same results as Tom using the +> statements shown by Tom. + +On looking at the code, I do see part of a possible mechanism for this +behavior: cost_index calculates the estimated cost for qual-clause +evaluation like this: + + /* + * Estimate CPU costs per tuple. + * + * Normally the indexquals will be removed from the list of restriction + * clauses that we have to evaluate as qpquals, so we should subtract + * their costs from baserestrictcost. XXX For a lossy index, not all + * the quals will be removed and so we really shouldn't subtract their + * costs; but detecting that seems more expensive than it's worth. + * Also, if we are doing a join then some of the indexquals are join + * clauses and shouldn't be subtracted. Rather than work out exactly + * how much to subtract, we don't subtract anything. + */ + cpu_per_tuple = cpu_tuple_cost + baserel->baserestrictcost; + + if (!is_injoin) + cpu_per_tuple -= cost_qual_eval(indexQuals); + +In theory, indexQuals will always be a subset of the qual list on which +baserestrictcost was computed, so we should always end up with a +cpu_per_tuple value at least as large as cpu_tuple_cost. I am wondering +if somehow in Achilleus's situation, cost_qual_eval() is producing a +silly result leading to negative cpu_per_tuple. I don't see how that +could happen though --- nor why it would happen on his machine and not +other people's. + + regards, tom lane + +From pgsql-general-owner@postgresql.org Tue Jan 7 15:03:50 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 60054475E14 + for ; + Tue, 7 Jan 2003 15:03:48 -0500 (EST) +Received: from mail.digicamp.com (ns1.digicamp.com [216.38.142.76]) + by postgresql.org (Postfix) with SMTP id 8D4D2475A71 + for ; + Tue, 7 Jan 2003 15:03:47 -0500 (EST) +Received: (qmail 3842 invoked from network); 7 Jan 2003 19:46:22 -0000 +Received: from localhost (HELO digicamp.com) (127.0.0.1) + by localhost with SMTP; 7 Jan 2003 19:46:22 -0000 +Received: from 168.103.211.137 + (SquirrelMail authenticated user fred@digicamp.com) + by mail.digicamp.com with HTTP; Tue, 7 Jan 2003 11:46:22 -0800 (PST) +Message-ID: <36045.168.103.211.137.1041968782.squirrel@mail.digicamp.com> +Date: Tue, 7 Jan 2003 11:46:22 -0800 (PST) +Subject: Re: [PERFORM] PostgreSQL and memory usage +From: "Fred Moyer" +To: +X-XheaderVersion: 1.1 +X-UserAgent: Mozilla/5.0 (X11; U; Linux i686; en-US; + rv:1.3a) Gecko/20021207 Phoenix/0.5 +In-Reply-To: +References: + + +X-Priority: 3 +Importance: Normal +Cc: , , + , +Reply-To: fred@digicamp.com +X-Mailer: SquirrelMail (version 1.2.10) +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/253 +X-Sequence-Number: 35374 + +To put this usage of shared buffers in perspective would you mind kindly +let us know your total amount of system ram? Without hearing what +percentage of memory used as shared buffers (assuming is the primary +application being using here) + +I have always taken the 'more is better' approach with shared buffers but +would like to know what in terms of percentages other people are using. I +have been using 50% of system ram (2 out of 4 gigs) for shared buffers +(and corresponding shmmax values) and it has been working great. I +haven't tweaked the kernel yet to get more than 2 gigs shmmax so I can't +speak for a setup using over 50%. I've been using between 256 and 512 +megs sort memory which sounds like a little much from what I'm hearing +here. + +Thanks + +Fred + +> +> Hi Dann, I took hackers out of the list as this isn't really a hacking +> issue, but I added in performance as this definitely applies there. +> +> There are generally two areas of a database server you have to +> reconfigure to use that extra memory. The first is the kernel's shared +> memory settings. +> +> On a linux box that has sysconf installed this is quite easy. If it +> isn't installed, install it, as it's much easier to manipulate your +> kernel's settings using sysctl than it is with editing rc.local. +> +> First, get root. Then, use 'sysctl -a|grep shm' to get a list of all +> the shared memory settings handled by sysctl. +> +> On a default redhat install, we'll get something like this: +> +> kernel.shmmni = 4096 +> kernel.shmall = 2097152 +> kernel.shmmax = 33554432 +> +> On my bigger box, it's been setup to have this: +> +> kernel.shmmni = 4096 +> kernel.shmall = 32000000 +> kernel.shmmax = 256000000 +> +> To make changes that stick around, edit the /etc/sysctl.conf file to +> have lines that look kinda like those above. To make the changes to +> the /etc/sysctl.conf file take effect, use 'sysctl -p'. +> +> Next, as the postgres user, edit $PGDATA/postgresql.conf and increase +> the number of shared buffers. On most postgresql installations this +> number is multiplied by 8k to get the amount of ram being allocated, +> since +> postgresql allocates share buffers in blocks the same size as what it +> uses on the dataset. To allocate 256 Megs of buffers (that's what I +> use, seems like a nice large chunk, but doesn't starve my other +> processes or system file cache) set it to 32768. +> +> Be careful how big you make your sort size. I haven't seen a great +> increase in speed on anything over 8 or 16 megs, while memory usage can +> skyrocket under heavy parallel load with lots of sorts, since sort +> memory is PER SORT maximum. +> +> Then do the old pg_ctl reload and you should be cooking with gas. +> +> +> ---------------------------(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 + + + + + +From pgsql-general-owner@postgresql.org Tue Jan 7 11:19:15 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 03212477060; Tue, 7 Jan 2003 11:19:13 -0500 (EST) +Received: from matrix.gatewaynet.com (unknown [217.19.69.50]) + by postgresql.org (Postfix) with ESMTP + id D443447676D; Tue, 7 Jan 2003 11:19:06 -0500 (EST) +Received: from matrix.gatewaynet.com (matrix.gatewaynet.com [217.19.69.50]) + by matrix.gatewaynet.com (8.12.5/8.12.5) with ESMTP id h07KRXXR009290; + Tue, 7 Jan 2003 18:27:33 -0200 +Received: from localhost (achill@localhost) + by matrix.gatewaynet.com (8.12.5/8.12.5/Submit) with ESMTP id + h07KRW5Z009286; Tue, 7 Jan 2003 18:27:33 -0200 +Date: Tue, 7 Jan 2003 18:27:32 -0200 (GMT+2) +From: Achilleus Mantzios +To: Stephan Szabo +Cc: pgsql-performance@postgresql.org, , + +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance +In-Reply-To: <20030107072146.L61341-100000@megazone23.bigpanda.com> +Message-ID: +MIME-Version: 1.0 +Content-Type: MULTIPART/MIXED; BOUNDARY="333001285-560812375-1041971252=:8183" +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/236 +X-Sequence-Number: 35357 + + This message is in MIME format. The first part should be readable text, + while the remaining parts are likely unreadable without MIME-aware tools. + Send mail to mime@docserver.cac.washington.edu for more info. + +--333001285-560812375-1041971252=:8183 +Content-Type: TEXT/PLAIN; charset=US-ASCII + +On Tue, 7 Jan 2003, Stephan Szabo wrote: + +> +> On Tue, 7 Jan 2003, Achilleus Mantzios wrote: +> +> > i am just in the stage of having migrated my test system to 7.3.1 +> > and i am experiencing some performance problems. +> > +> > i have a table "noon" +> > Table "public.noon" +> > Column | Type | Modifiers +> > ------------------------+------------------------+----------- +> > v_code | character varying(4) | +> > log_no | bigint | +> > report_date | date | +> > report_time | time without time zone | +> > voyage_no | integer | +> > charterer | character varying(12) | +> > port | character varying(24) | +> > duration | character varying(4) | +> > rotation | character varying(9) | +> > ...... +> > +> > with a total of 278 columns. +> > +> > it has indexes: +> > Indexes: noonf_date btree (report_date), +> > noonf_logno btree (log_no), +> > noonf_rotation btree (rotation text_ops), +> > noonf_vcode btree (v_code), +> > noonf_voyageno btree (voyage_no) +> > +> > On the test 7.3.1 system (a FreeBSD 4.7-RELEASE-p2, Celeron 1.2GHz +> > 400Mb, with 168Mb for pgsql), +> > i get: +> > dynacom=# EXPLAIN ANALYZE select +> > FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where +> > v_code='4500' and rotation='NOON ' and report_date between +> > '2002-01-07' and '2003-01-07'; +> > QUERY PLAN +> > +> +> > ------------------------------------------------------------------------------------------------------------------- +> > Index Scan using noonf_date on noon (cost=0.00..4.46 rows=1 width=39) +> > (actual time=0.27..52.89 rows=259 loops=1) +> +> +> > Index Scan using noonf_vcode on noon (cost=0.00..3122.88 rows=1 +> > width=39) (actual time=0.16..13.92 rows=259 loops=1) +> +> +> What do the statistics for the three columns actually look like and what +> are the real distributions and counts like? + +The two databases (test 7.3.1 and development 7.2.3) are identical +(loaded from the same pg_dump). + +About the stats on these 3 columns i get: (see also attachment 1 to avoid +identation/wraparound problems) + + schemaname | tablename | attname | null_frac | avg_width | n_distinct | most_common_vals | most_common_freqs | histogram_bounds | correlation +------------+-----------+-------------+-----------+-----------+------------+-----------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------+------------- + public | noon | v_code | 0 | 8 | 109 | {4630,4650,4690,4670,4520,4610,4550,4560,4620,4770} | {0.0283333,0.028,0.0256667,0.0243333,0.024,0.0236667,0.0233333,0.0233333,0.0226667,0.0226667} | {2070,3210,4330,4480,4570,4680,4751,4820,4870,4940,6020} | -0.249905 + public | noon | report_date | 0 | 4 | 3408 | {2001-11-14,1998-10-18,2000-04-03,2000-07-04,2000-12-20,2000-12-31,2001-01-12,2001-10-08,2001-12-25,1996-01-23} | {0.002,0.00166667,0.00166667,0.00166667,0.00166667,0.00166667,0.00166667,0.00166667,0.00166667,0.00133333} | {"0001-12-11 BC",1994-09-27,1996-03-26,1997-07-29,1998-08-26,1999-03-29,1999-11-30,2000-09-25,2001-05-25,2002-01-17,2002-12-31} | -0.812295 + public | noon | rotation | 0 | 13 | 6 | {"NOON ","PORT LOG ","ARRIVAL ",DEPARTURE,"SEA ","NEXT PORT"} | {0.460333,0.268667,0.139,0.119667,0.007,0.00533333} | | 0.119698 +(3 rows) + + +About distributions, i have: + +dynacom=# SELECT rotation,count(*) from noon group by rotation; + rotation | count +-----------+------- + | 2 + 000000000 | 65 + ARRIVAL | 1 + ARRIVAL | 15471 + DEPARTURE | 15030 + NEXT PORT | 462 + NOON | 50874 + PORT LOG | 25688 + SEA | 1202 +(9 rows) + +dynacom=# SELECT v_code,count(*) from noon group by v_code; + v_code | count +--------+------- + 0004 | 1 + 1030 | 1 + 2070 | 170 + 2080 | 718 + 2110 | 558 + 2220 | 351 + 2830 | 1373 + 2840 | 543 + 2860 | 407 + 2910 | 418 + 3010 | 352 + 3020 | 520 + 3060 | 61 + 3130 | 117 + 3140 | 1 + 3150 | 752 + 3160 | 811 + 3170 | 818 + 3180 | 1064 + 3190 | 640 + 3200 | 998 + 3210 | 1512 + 3220 | 595 + 3230 | 374 + 3240 | 514 + 3250 | 13 + 3260 | 132 + 3270 | 614 + 4010 | 413 + 4020 | 330 + 4040 | 728 + 4050 | 778 + 4060 | 476 + 4070 | 534 + 4310 | 759 + 4320 | 424 + 4330 | 549 + 4360 | 366 + 4370 | 334 + 4380 | 519 + 4410 | 839 + 4420 | 183 + 4421 | 590 + 4430 | 859 + 4450 | 205 + 4470 | 861 + 4480 | 766 + 4490 | 169 + 4500 | 792 + 4510 | 2116 + 4520 | 2954 + 4530 | 2142 + 4531 | 217 + 4540 | 2273 + 4550 | 2765 + 4560 | 2609 + 4570 | 2512 + 4580 | 1530 + 4590 | 1987 + 4600 | 308 + 4610 | 2726 + 4620 | 2698 + 4630 | 2813 + 4640 | 1733 + 4650 | 2655 + 4660 | 2139 + 4661 | 65 + 4670 | 2607 + 4680 | 1729 + 4690 | 2587 + 4700 | 2101 + 4710 | 1830 + 4720 | 1321 + 4730 | 1258 + 4740 | 1506 + 4750 | 1391 + 4751 | 640 + 4760 | 1517 + 4770 | 2286 + 4780 | 1353 + 4790 | 1209 + 4800 | 2414 + 4810 | 770 + 4820 | 1115 + 4830 | 1587 + 4840 | 983 + 4841 | 707 + 4850 | 1297 + 4860 | 375 + 4870 | 1440 + 4880 | 456 + 4881 | 742 + 4890 | 210 + 4891 | 45 + 4900 | 2 + 4910 | 1245 + 4920 | 414 + 4930 | 1130 + 4940 | 1268 + 4950 | 949 + 4960 | 836 + 4970 | 1008 + 4980 | 1239 + 5510 | 477 + 5520 | 380 + 5530 | 448 + 5540 | 470 + 5550 | 352 + 5560 | 148 + 5570 | 213 + 5580 | 109 + 5590 | 55 + 6010 | 246 + 6020 | 185 + 9180 | 1 + +(Not all the above vessels are active or belong to me:) ) + +The distribution on the report_date has no probabilistic significance +since each report_date usually corresponds to one row. +So, +dynacom=# SELECT count(*) from noon; + count +-------- + 108795 +(1 row) + +dynacom=# + +Now for the specific query the counts have as follows: + +dynacom=# select count(*) from noon where v_code='4500'; + count +------- + 792 +(1 row) + +dynacom=# select count(*) from noon where rotation='NOON '; + count +------- + 50874 +(1 row) + +dynacom=# select count(*) from noon where report_date between '2002-01-07' +and '2003-01-07'; + count +------- + 7690 +(1 row) + +dynacom=# + +> Given an estimated cost of around 4 for the first scan, my guess would be +> that it's not expecting alot of rows between 2002-01-07 and 2003-01-07 +> which would make that a reasonable plan. +> + +As we see the rows returned for v_code='4500' (792) are much fewer than +the rows returned for the dates between '2002-01-07' and '2003-01-07' +(7690). + +Is there a way to provide you with more information? + +And i must note that the two databases were worked on after a fresh +createdb on both systems (and as i told they are identical). +But, for some reason the 7.2.3 *always* finds the best index to use :) + +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 6: Have you searched our list archives? +> +> http://archives.postgresql.org +> + +================================================================== +Achilleus Mantzios +S/W Engineer +IT dept +Dynacom Tankers Mngmt +Nikis 4, Glyfada +Athens 16610 +Greece +tel: +30-10-8981112 +fax: +30-10-8981877 +email: achill@matrix.gatewaynet.com + mantzios@softlab.ece.ntua.gr + +--333001285-560812375-1041971252=:8183 +Content-Type: TEXT/PLAIN; 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Tue, 7 Jan 2003 15:30:24 -0500 (EST) +Received: from hoemail2.firewall.lucent.com (hoemail2.lucent.com + [192.11.226.163]) by postgresql.org (Postfix) with ESMTP + id 2F75C47727F; Tue, 7 Jan 2003 15:29:56 -0500 (EST) +Received: from nj7460exch002h.wins.lucent.com (h135-17-42-35.lucent.com + [135.17.42.35]) + by hoemail2.firewall.lucent.com (Switch-2.2.2/Switch-2.2.0) with ESMTP + id h07KTtl17570; Tue, 7 Jan 2003 15:29:55 -0500 (EST) +Received: by nj7460exch002h.ho.lucent.com with Internet Mail Service + (5.5.2653.19) id ; Tue, 7 Jan 2003 15:29:55 -0500 +Message-ID: + +From: "Claiborne, Aldemaco Earl (Al)" +To: "'Tom Lane'" +Cc: pgsql-general@postgresql.org, pgsql-performance@postgresql.org +Subject: path +Date: Tue, 7 Jan 2003 15:29:54 -0500 +MIME-Version: 1.0 +X-Mailer: Internet Mail Service (5.5.2653.19) +Content-Type: text/plain +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/256 +X-Sequence-Number: 35377 + +Hi all, + +How is this path created without the (.profile)? + +$ echo $PATH +/usr/local/bin:/usr/bin:/bin:/cygdrive/c/amtagent:/cygdrive/c/informix/bin:/cygd +rive/c/winnt:/cygdrive/c/winnt/system:winnt/system32:/cygdrive/c/Windows:/cygdri +ve/c/Windows/command:C:jdk1.2.2/bin + +How can I add this path to the above path? ~/cygwin/usr/bin/gcc-3.2.1 + + + + +From pgsql-general-owner@postgresql.org Tue Jan 7 11:56:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id CD5C2476501; Tue, 7 Jan 2003 11:56:53 -0500 (EST) +Received: from matrix.gatewaynet.com (unknown [217.19.69.50]) + by postgresql.org (Postfix) with ESMTP + id 6159B4762C5; Tue, 7 Jan 2003 11:56:52 -0500 (EST) +Received: from matrix.gatewaynet.com (matrix.gatewaynet.com [217.19.69.50]) + by matrix.gatewaynet.com (8.12.5/8.12.5) with ESMTP id h07L5NXR009492; + Tue, 7 Jan 2003 19:05:23 -0200 +Received: from localhost (achill@localhost) + by matrix.gatewaynet.com (8.12.5/8.12.5/Submit) with ESMTP id + h07L5Mh4009488; Tue, 7 Jan 2003 19:05:22 -0200 +Date: Tue, 7 Jan 2003 19:05:22 -0200 (GMT+2) +From: Achilleus Mantzios +To: Tom Lane +Cc: Stephan Szabo , + , , + +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance +In-Reply-To: <13843.1041956988@sss.pgh.pa.us> +Message-ID: +MIME-Version: 1.0 +Content-Type: MULTIPART/MIXED; + BOUNDARY="333001285-1824804068-1041973522=:9324" +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/238 +X-Sequence-Number: 35359 + + This message is in MIME format. The first part should be readable text, + while the remaining parts are likely unreadable without MIME-aware tools. + Send mail to mime@docserver.cac.washington.edu for more info. + +--333001285-1824804068-1041973522=:9324 +Content-Type: TEXT/PLAIN; charset=US-ASCII + +On Tue, 7 Jan 2003, Tom Lane wrote: + +> Achilleus Mantzios writes: +> > About the stats on these 3 columns i get: +> +> Does 7.2 generate the same stats? (minus the schemaname of course) + +Not absolutely but close: + +(See attachment) + +> +> Also, I would like to see the results of these queries on both versions, +> so that we can see what the planner thinks the index selectivity is: +> +> EXPLAIN ANALYZE select * from noon where +> v_code='4500'; +> +> EXPLAIN ANALYZE select * from noon where +> report_date between '2002-01-07' and '2003-01-07'; +> + +On 7.3.1 (On a FreeBSD) +======================= +dynacom=# EXPLAIN ANALYZE select * from noon where v_code='4500'; + QUERY PLAN + +----------------------------------------------------------------------------------------------------------------------------- + Index Scan using noonf_vcode on noon (cost=0.00..3066.64 rows=829 +width=1974) (actual time=2.02..1421.14 rows=792 loops=1) + Index Cond: (v_code = '4500'::character varying) + Total runtime: 1424.82 msec +(3 rows) + + +dynacom=# EXPLAIN ANALYZE select * from noon where report_date between +'2002-01-07' and '2003-01-07'; + QUERY PLAN + +--------------------------------------------------------------------------------------------------------------------------------- + Index Scan using noonf_date on noon (cost=0.00..15919.50 rows=11139 +width=1974) (actual time=2.05..13746.17 rows=7690 loops=1) + Index Cond: ((report_date >= '2002-01-07'::date) AND (report_date <= +'2003-01-07'::date)) + Total runtime: 13775.48 msec +(3 rows) + +On 7.2.3 (Linux) +================== +dynacom=# EXPLAIN ANALYZE select * from noon where v_code='4500'; +NOTICE: QUERY PLAN: + +Index Scan using noonf_vcode on noon (cost=0.00..3043.45 rows=827 +width=1974) (actual time=19.59..927.06 rows=792 loops=1) +Total runtime: 928.86 msec + +dynacom=# EXPLAIN ANALYZE select * from noon where report_date between +'2002-01-07' and '2003-01-07'; +NOTICE: QUERY PLAN: + +Index Scan using noonf_date on noon (cost=0.00..16426.45 rows=11958 +width=1974) (actual time=29.64..8854.05 rows=7690 loops=1) +Total runtime: 8861.90 msec + +EXPLAIN + +> regards, tom lane +> + +================================================================== +Achilleus Mantzios +S/W Engineer +IT dept +Dynacom Tankers Mngmt +Nikis 4, Glyfada +Athens 16610 +Greece +tel: +30-10-8981112 +fax: +30-10-8981877 +email: achill@matrix.gatewaynet.com + mantzios@softlab.ece.ntua.gr + +--333001285-1824804068-1041973522=:9324 +Content-Type: TEXT/PLAIN; charset=US-ASCII; name="querystats_on_7.2.3" +Content-Transfer-Encoding: BASE64 +Content-ID: +Content-Description: +Content-Disposition: attachment; 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Tue, 7 Jan 2003 12:46:58 -0500 (EST) +Received: from matrix.gatewaynet.com (unknown [217.19.69.50]) + by postgresql.org (Postfix) with ESMTP + id 943224772B4; Tue, 7 Jan 2003 12:46:57 -0500 (EST) +Received: from matrix.gatewaynet.com (matrix.gatewaynet.com [217.19.69.50]) + by matrix.gatewaynet.com (8.12.5/8.12.5) with ESMTP id h07LtXXR009677; + Tue, 7 Jan 2003 19:55:33 -0200 +Received: from localhost (achill@localhost) + by matrix.gatewaynet.com (8.12.5/8.12.5/Submit) with ESMTP id + h07LtXeB009673; Tue, 7 Jan 2003 19:55:33 -0200 +Date: Tue, 7 Jan 2003 19:55:33 -0200 (GMT+2) +From: Achilleus Mantzios +To: pgsql-general@postgresql.org, +Subject: 7.3.1 function problem: ERROR: cache lookup failed for type 0 +In-Reply-To: +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/243 +X-Sequence-Number: 35364 + + +Hi i had written a C function to easily convert an int4 to its +equivalent 1x1 int4[] array. + +It worked fine under 7.1,7.2. +Now under 7.3.1 i get the following message whenever i try to: + +dynacom=# select itoar(3126); +ERROR: cache lookup failed for type 0 + +Surprisingly though when i do something like : + +dynacom=# select defid from machdefs where itoar(3126) ~ parents and +level(parents) = 1 order by description,partno; + defid +------- + 3137 + 3127 + 3130 + 3129 + 3133 + 3136 + 3135 + 3128 + 3131 + 3132 + 3134 + 3138 +(12 rows) + +it works fine, but then again when i try to EXPLAIN the above (successful) +statement i also get: + +dynacom=# EXPLAIN select defid from machdefs where itoar(3126) ~ parents +and +level(parents) = 1 order by description,partno; +ERROR: cache lookup failed for type 0 + + +Any clues of what could be wrong?? + +The definition of the function is: + +CREATE FUNCTION "itoar" (integer) RETURNS integer[] AS +'$libdir/itoar', 'itoar' LANGUAGE 'c' WITH ( iscachable,isstrict ); + +I also tried without the iscachable option with no luck +(since it seems to complain about *type* 0) + +================================================================== +Achilleus Mantzios +S/W Engineer +IT dept +Dynacom Tankers Mngmt +Nikis 4, Glyfada +Athens 16610 +Greece +tel: +30-10-8981112 +fax: +30-10-8981877 +email: achill@matrix.gatewaynet.com + mantzios@softlab.ece.ntua.gr + + +From pgsql-general-owner@postgresql.org Tue Jan 7 13:24:29 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 25849477292; Tue, 7 Jan 2003 13:24:29 -0500 (EST) +Received: from matrix.gatewaynet.com (unknown [217.19.69.50]) + by postgresql.org (Postfix) with ESMTP + id 92F764771F7; Tue, 7 Jan 2003 13:24:26 -0500 (EST) +Received: from matrix.gatewaynet.com (matrix.gatewaynet.com [217.19.69.50]) + by matrix.gatewaynet.com (8.12.5/8.12.5) with ESMTP id h07MWuXR009828; + Tue, 7 Jan 2003 20:32:57 -0200 +Received: from localhost (achill@localhost) + by matrix.gatewaynet.com (8.12.5/8.12.5/Submit) with ESMTP id + h07MWulT009824; Tue, 7 Jan 2003 20:32:56 -0200 +Date: Tue, 7 Jan 2003 20:32:56 -0200 (GMT+2) +From: Achilleus Mantzios +To: Tom Lane +Cc: pgsql-general@postgresql.org, +Subject: Re: 7.3.1 function problem: ERROR: cache lookup failed +In-Reply-To: <15501.1041963735@sss.pgh.pa.us> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/246 +X-Sequence-Number: 35367 + +On Tue, 7 Jan 2003, Tom Lane wrote: + +> Achilleus Mantzios writes: +> > Hi i had written a C function to easily convert an int4 to its +> > equivalent 1x1 int4[] array. +> +> Does your function know about filling in the elemtype field that was +> recently added to struct ArrayType? + +She has no clue :) + +Any pointers would be great. +Thanx Tom. + +> +> regards, tom lane +> + +================================================================== +Achilleus Mantzios +S/W Engineer +IT dept +Dynacom Tankers Mngmt +Nikis 4, Glyfada +Athens 16610 +Greece +tel: +30-10-8981112 +fax: +30-10-8981877 +email: achill@matrix.gatewaynet.com + mantzios@softlab.ece.ntua.gr + + +From pgsql-general-owner@postgresql.org Tue Jan 7 13:29:55 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 6486E47612D; Tue, 7 Jan 2003 13:29:51 -0500 (EST) +Received: from matrix.gatewaynet.com (unknown [217.19.69.50]) + by postgresql.org (Postfix) with ESMTP + id 46DA4475ED4; Tue, 7 Jan 2003 13:29:50 -0500 (EST) +Received: from matrix.gatewaynet.com (matrix.gatewaynet.com [217.19.69.50]) + by matrix.gatewaynet.com (8.12.5/8.12.5) with ESMTP id h07McIXR009854; + Tue, 7 Jan 2003 20:38:18 -0200 +Received: from localhost (achill@localhost) + by matrix.gatewaynet.com (8.12.5/8.12.5/Submit) with ESMTP id + h07McH2k009850; Tue, 7 Jan 2003 20:38:17 -0200 +Date: Tue, 7 Jan 2003 20:38:17 -0200 (GMT+2) +From: Achilleus Mantzios +To: Tom Lane +Cc: Stephan Szabo , + , , + +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance +In-Reply-To: <14598.1041961456@sss.pgh.pa.us> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/247 +X-Sequence-Number: 35368 + +On Tue, 7 Jan 2003, Tom Lane wrote: + +> There is no way that adding the filter condition should have reduced the +> estimated runtime for this plan --- reducing the estimated number of +> output rows, yes, but not the runtime. And in fact I can't duplicate + +My case persists: +After clean install of the database, and after vacuum analyze, +i get + +dynacom=# EXPLAIN ANALYZE select +FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where +report_date between '2002-01-07' and '2003-01-07'; + QUERY PLAN + +----------------------------------------------------------------------------------------------------------------------------- + Index Scan using noonf_date on noon (cost=0.00..16458.54 rows=10774 +width=39) (actual time=0.13..205.86 rows=7690 loops=1) + Index Cond: ((report_date >= '2002-01-07'::date) AND (report_date <= +'2003-01-07'::date)) + Total runtime: 233.22 msec + +dynacom=# EXPLAIN ANALYZE select +FUELCONSUMPTION,rpm,Steam_Hours,voyage_activity,ldin from noon where +report_date between '2002-01-07' and '2003-01-07' and v_code='4500'; + QUERY PLAN + +------------------------------------------------------------------------------------------------------------------------ + Index Scan using noonf_vcode on noon (cost=0.00..3092.52 rows=83 +width=39) (actual time=0.15..15.08 rows=373 loops=1) + Index Cond: (v_code = '4500'::character varying) + Filter: ((report_date >= '2002-01-07'::date) AND (report_date <= +'2003-01-07'::date)) + Total runtime: 16.56 msec +(4 rows) + +I thought PostgreSQL in some sense (hub.org) used FreeBSD, +is there any 4.7 FreeBSD server with pgsql 7.3.1 you could use? + +================================================================== +Achilleus Mantzios +S/W Engineer +IT dept +Dynacom Tankers Mngmt +Nikis 4, Glyfada +Athens 16610 +Greece +tel: +30-10-8981112 +fax: +30-10-8981877 +email: achill@matrix.gatewaynet.com + mantzios@softlab.ece.ntua.gr + + +From pgsql-general-owner@postgresql.org Tue Jan 7 13:43:18 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 1FBD4476879; Tue, 7 Jan 2003 13:43:17 -0500 (EST) +Received: from matrix.gatewaynet.com (unknown [217.19.69.50]) + by postgresql.org (Postfix) with ESMTP + id 657DE4773B4; Tue, 7 Jan 2003 13:43:07 -0500 (EST) +Received: from matrix.gatewaynet.com (matrix.gatewaynet.com [217.19.69.50]) + by matrix.gatewaynet.com (8.12.5/8.12.5) with ESMTP id h07MpZXR009941; + Tue, 7 Jan 2003 20:51:35 -0200 +Received: from localhost (achill@localhost) + by matrix.gatewaynet.com (8.12.5/8.12.5/Submit) with ESMTP id + h07MpZxh009937; Tue, 7 Jan 2003 20:51:35 -0200 +Date: Tue, 7 Jan 2003 20:51:35 -0200 (GMT+2) +From: Achilleus Mantzios +To: Tom Lane +Cc: Stephan Szabo , + , , + +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance +In-Reply-To: <19585.1041964797@sss.pgh.pa.us> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/250 +X-Sequence-Number: 35371 + +On Tue, 7 Jan 2003, Tom Lane wrote: + +> Achilleus Mantzios writes: +> > My case persists: +> > After clean install of the database, and after vacuum analyze, +> > i get +> +> Um ... is it persisting? That looks like it's correctly picked the +> vcode index this time. Strange behavior though. By "clean install" +> do you mean you rebuilt Postgres, or just did dropdb/createdb/reload +> data? + +Just dropdb/createdb/reload. + +> +> regards, tom lane +> + +================================================================== +Achilleus Mantzios +S/W Engineer +IT dept +Dynacom Tankers Mngmt +Nikis 4, Glyfada +Athens 16610 +Greece +tel: +30-10-8981112 +fax: +30-10-8981877 +email: achill@matrix.gatewaynet.com + mantzios@softlab.ece.ntua.gr + + +From pgsql-general-owner@postgresql.org Tue Jan 7 18:24:26 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 1219D4773C9; Tue, 7 Jan 2003 18:24:26 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP + id 1480F4772D1; Tue, 7 Jan 2003 18:23:51 -0500 (EST) +Received: from css120.ihs.com (css120.ihs.com [170.207.105.120]) + by mail1.ihs.com (8.12.6/8.12.6) with ESMTP id h07NLafC008174; + Tue, 7 Jan 2003 16:21:36 -0700 (MST) +Date: Tue, 7 Jan 2003 16:16:09 -0700 (MST) +From: "scott.marlowe" +To: Fred Moyer +Cc: , , + , +Subject: Re: [PERFORM] PostgreSQL and memory usage +In-Reply-To: <36045.168.103.211.137.1041968782.squirrel@mail.digicamp.com> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-MailScanner: Found to be clean +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/264 +X-Sequence-Number: 35385 + +Oh yeah, sorry. My box has 1.5 gig ram, but it is an application server +that runs things other than just postgresql. It also runs: + +Apache +Real Server +OpenLDAP +Squid +Samba + +with all those services fired up and running, as well as postgresql with +256 Megs of shared buffer, I have about 900 megs of cache and 100 megs +free ram. Since a lot of data is flying off the hard drives at any given +time, favoring one service (database) over the others makes little sense +for me, and I've found that there was little or no performance gain from +256 Megs ram over say 128 meg or 64 meg. + +We run about 50 databases averaging about 25megs each or so (backed up, +it's about 50 to 75 Megs on the machine's hard drives) so there's no +way for ALL the data to fit into memory. + +On Tue, 7 Jan 2003, Fred Moyer wrote: + +> To put this usage of shared buffers in perspective would you mind kindly +> let us know your total amount of system ram? Without hearing what +> percentage of memory used as shared buffers (assuming is the primary +> application being using here) +> +> I have always taken the 'more is better' approach with shared buffers but +> would like to know what in terms of percentages other people are using. I +> have been using 50% of system ram (2 out of 4 gigs) for shared buffers +> (and corresponding shmmax values) and it has been working great. I +> haven't tweaked the kernel yet to get more than 2 gigs shmmax so I can't +> speak for a setup using over 50%. I've been using between 256 and 512 +> megs sort memory which sounds like a little much from what I'm hearing +> here. + + +From pgsql-performance-owner@postgresql.org Wed Jan 8 08:27:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1AD78475F34 + for ; + Wed, 8 Jan 2003 08:27:08 -0500 (EST) +Received: from benhur.intern.control.de (unknown [217.89.112.10]) + by postgresql.org (Postfix) with ESMTP id C1AA0475CED + for ; + Wed, 8 Jan 2003 08:27:06 -0500 (EST) +Received: from devserver (devserver.intern.control.de [192.168.100.5]) + by benhur.intern.control.de (8.12.6/8.12.6/Benhur 8.12.6) with ESMTP id + h08DQGVO019858 + for ; Wed, 8 Jan 2003 14:26:17 +0100 +Content-Type: text/plain; + charset="us-ascii" +From: Boris Klug +Organization: control IT GmbH +To: pgsql-performance@postgresql.org +Subject: Unions and where optimisation +Date: Wed, 8 Jan 2003 14:25:48 +0100 +User-Agent: KMail/1.4.3 +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301081425.48597.boris.klug@control.de> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/52 +X-Sequence-Number: 699 + +Hello! + +I am quite new in the PostgreSQL performance business, done a few years Ora= +cle=20 +stuff before. My ist question is the following: + +We have three table, lets name them rk150, 151 and rk152. They all have a= +=20 +timestamp and a order number in common but than different data after this.= +=20 +Now I need the data from all tables in one view for a given order number, s= +o=20 +I created a view + +create view orderevents as + select ts, aufnr from rk150 + union + select ts, aufnr from rk151 + union + select ts, aufnr from rk152; + +When I does a "select * from orderevents where aufnr=3D'1234'" it takes ove= +r 14=20 +seconds! +The problem is now that PostgreSQL first does the union with all the three= +=20 +tables and after this sorts out the right rows: + +Subquery Scan a (cost=3D54699.06..56622.18 rows=3D38462 width=3D20) + -> Unique (cost=3D54699.06..56622.18 rows=3D38462 width=3D20) + -> Sort (cost=3D54699.06..54699.06 rows=3D384624 width=3D20) + -> Append (cost=3D0.00..10689.24 rows=3D384624 width=3D20) + -> Subquery Scan *SELECT* 1 + (cost=3D0.00..8862.52 rows=3D314852 width=3D20) + -> Seq Scan on rk150=20 + (cost=3D0.00..8862.52 rows=3D314852 width=3D20) + -> Subquery Scan *SELECT* 2=20=20 + (cost=3D0.00..1208.58 rows=3D45858 width=3D20) + -> Seq Scan on rk151=20=20 + (cost=3D0.00..1208.58 rows=3D45858 width=3D20) + -> Subquery Scan *SELECT* 3=20 + (cost=3D0.00..618.14 rows=3D23914 width=3D20) + -> Seq Scan on rk152=20=20 + (cost=3D0.00..618.14 rows=3D23914 width=3D20) + +A better thing would it (Oracle does this and I think I have seen it on=20 +PostgreSQL before), that the where-clause is moved inside every select so w= +e=20 +have something like this (written by hand): + +select * from ( + select zeit, aufnr from rk150 where aufnr=3D'13153811' + union + select zeit, aufnr from rk151 where aufnr=3D'13153811' + union + select zeit, aufnr from rk152 where aufnr=3D'13153811') + as A; + +This takes less than 1 second because the nr of rows that have to be joined= +=20 +are only 45 (optimizer expects 4), not > 300.000: + +Subquery Scan a (cost=3D45.97..46.19 rows=3D4 width=3D20) + -> Unique (cost=3D45.97..46.19 rows=3D4 width=3D20) + -> Sort (cost=3D45.97..45.97 rows=3D45 width=3D20) + -> Append (cost=3D0.00..44.74 rows=3D45 width=3D20) + -> Subquery Scan *SELECT* 1=20 + (cost=3D0.00..32.22 rows=3D31 width=3D20) + -> Index Scan using rk150_uidx_aufnr on rk150=20= +=20 + (cost=3D0.00..32.22 rows=3D31 width=3D20) + -> Subquery Scan *SELECT* 2=20 + (cost=3D0.00..7.67 rows=3D9 width=3D20) + -> Index Scan using rk151_uidx_aufnr on rk151=20= +=20 + (cost=3D0.00..7.67 rows=3D9 width=3D20) + -> Subquery Scan *SELECT* 3=20=20 + (cost=3D0.00..4.85 rows=3D5 width=3D20) + -> Index Scan using rk152_uidx_aufnr on rk152=20 + (cost=3D0.00..4.85 rows=3D5 width=3D20) + +My question now: Is the optimizer able to move the where clause into unions= +?=20 +If so, how I can get him to do it? + +Thank you for the help in advance! + +--=20 +Dipl. Inform. Boris Klug, control IT GmbH, Germany + +From pgsql-performance-owner@postgresql.org Wed Jan 8 09:28:29 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D980E475AAC + for ; + Wed, 8 Jan 2003 09:28:27 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 3966E4758F1 + for ; + Wed, 8 Jan 2003 09:28:27 -0500 (EST) +Received: from klaster.net (pa168.krakow.cvx.ppp.tpnet.pl [213.76.36.168]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP + id 618902B21C; Wed, 8 Jan 2003 15:26:34 +0100 (CET) +Message-ID: <3E1C366B.5080406@klaster.net> +Date: Wed, 08 Jan 2003 15:32:11 +0100 +From: Tomasz Myrta +User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; + rv:1.2b) Gecko/20021016 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Hannu Krosing +Cc: Boris Klug , + "pgsql-performance@postgresql.org" +Subject: Re: Unions and where optimisation +References: <200301081425.48597.boris.klug@control.de> + <1042041735.3237.1.camel@huli> +In-Reply-To: <200301081425.48597.boris.klug@control.de> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/55 +X-Sequence-Number: 702 + +Hannu Krosing wrote: + +> +> try making the orderevents view like this: +> +> create view orderevents as +> select rk.aufnr, sub.ts +> from rk150 rk, +> ( select ts from rk150 where aufnr = rk.aufr +> union +> select ts from rk151 where aufnr = rk.aufr +> union +> select ts from rk152 where aufnr = rk.aufr +> ) as sub +> ; +> +> this could/should force your desired behavior. +> + +Hannu, does it work? +Few months ago I lost some time trying to create this kind of query and +I always got error, that subselect doesn't knows anything about upper +(outer?) table. + +In this query you should get error: +"relation rk does not exist". + +What version of postgres do you have? +Tomasz Myrta + + +From pgsql-performance-owner@postgresql.org Wed Jan 8 09:37:09 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EA2B3476F6B + for ; + Wed, 8 Jan 2003 09:37:08 -0500 (EST) +Received: from benhur.intern.control.de (unknown [217.89.112.10]) + by postgresql.org (Postfix) with ESMTP id C0B12476F67 + for ; + Wed, 8 Jan 2003 09:37:07 -0500 (EST) +Received: from devserver (devserver.intern.control.de [192.168.100.5]) + by benhur.intern.control.de (8.12.6/8.12.6/Benhur 8.12.6) with ESMTP id + h08Eb2VO024564; Wed, 8 Jan 2003 15:37:02 +0100 +Content-Type: text/plain; + charset="iso-8859-1" +From: Boris Klug +Organization: control IT GmbH +To: Tomasz Myrta , Hannu Krosing +Subject: Re: Unions and where optimisation +Date: Wed, 8 Jan 2003 15:36:33 +0100 +User-Agent: KMail/1.4.3 +Cc: "pgsql-performance@postgresql.org" +References: <200301081425.48597.boris.klug@control.de> + <1042041735.3237.1.camel@huli> <3E1C366B.5080406@klaster.net> +In-Reply-To: <3E1C366B.5080406@klaster.net> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301081536.33211.boris.klug@control.de> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/57 +X-Sequence-Number: 704 + + +Hello! + +> Hannu, does it work? +> Few months ago I lost some time trying to create this kind of query and +> I always got error, that subselect doesn't knows anything about upper +> (outer?) table. + +It does not work on my PostgreSQL 7.2.x + +Get the same error like you: "relation rk does not exist" + +Also the disadvantage of this solution is that the speed up is bound to=20 +queries for the ordernr. If a statement has a where clause e.g. for a=20 +timestamp, the view is still slow. + +Does PostgreSQL not know how to move where clause inside each select in a= +=20 +union? + +--=20 +Dipl. Inform. Boris Klug, control IT GmbH, Germany + +From pgsql-performance-owner@postgresql.org Wed Jan 8 09:36:57 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 97E2F475FCE + for ; + Wed, 8 Jan 2003 09:36:55 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id EBA84475EB2 + for ; + Wed, 8 Jan 2003 09:36:54 -0500 (EST) +Received: from klaster.net (ph110.krakow.cvx.ppp.tpnet.pl [217.99.208.110]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP + id 13E2C2B21C; Wed, 8 Jan 2003 15:35:06 +0100 (CET) +Message-ID: <3E1C386B.5050400@klaster.net> +Date: Wed, 08 Jan 2003 15:40:43 +0100 +From: Tomasz Myrta +User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; + rv:1.2b) Gecko/20021016 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Boris Klug +Cc: pgsql-performance@postgresql.org +Subject: Re: Unions and where optimisation +References: <200301081425.48597.boris.klug@control.de> +In-Reply-To: <200301081425.48597.boris.klug@control.de> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/56 +X-Sequence-Number: 703 + +Boris Klug wrote: + +> create view orderevents as +> select ts, aufnr from rk150 +> union +> select ts, aufnr from rk151 +> union +> select ts, aufnr from rk152; + +I lost some time and I didn't find valid solution for this kind of query :-( + +I solved it (nice to hear about better solution) using table inheritance. + +create table rk_master( +fields... +fields... +); + +create table rk150 () inherits rk_master; +create table rk151 () inherits rk_master; +create table rk152 () inherits rk_master; + +now you can just create simple view: +select ts, aufnr from rk_master; + +Regards, +Tomasz Myrta + + +From pgsql-performance-owner@postgresql.org Wed Jan 8 10:47:41 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 70FEE475D70 + for ; + Wed, 8 Jan 2003 10:47:40 -0500 (EST) +Received: from mail.gmx.net (mail.gmx.net [213.165.65.60]) + by postgresql.org (Postfix) with SMTP id 5ED75475CED + for ; + Wed, 8 Jan 2003 10:47:39 -0500 (EST) +Received: (qmail 30675 invoked by uid 0); 8 Jan 2003 15:47:43 -0000 +Received: from chello062178186201.1.15.tuwien.teleweb.at (HELO beeblebrox) + (62.178.186.201) + by mail.gmx.net (mp006-rz3) with SMTP; 8 Jan 2003 15:47:43 -0000 +Message-ID: <013001c2b72d$658ee4b0$3201a8c0@beeblebrox> +From: "Michael Paesold" +To: "Boris Klug" , + "Tomasz Myrta" , "Hannu Krosing" +Cc: +References: <200301081425.48597.boris.klug@control.de> + <1042041735.3237.1.camel@huli> <3E1C366B.5080406@klaster.net> + <200301081536.33211.boris.klug@control.de> +Subject: Re: Unions and where optimisation +Date: Wed, 8 Jan 2003 16:48:27 +0100 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 6.00.2800.1106 +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/60 +X-Sequence-Number: 707 + +Boris Klug wrote: + +> > Hannu, does it work? +> > Few months ago I lost some time trying to create this kind of query and +> > I always got error, that subselect doesn't knows anything about upper +> > (outer?) table. +> +> It does not work on my PostgreSQL 7.2.x +> +> Get the same error like you: "relation rk does not exist" +> +> Also the disadvantage of this solution is that the speed up is bound to +> queries for the ordernr. If a statement has a where clause e.g. for a +> timestamp, the view is still slow. +> +> Does PostgreSQL not know how to move where clause inside each select in a +> union? + +Hi Boris, + +As far as I know, this has first been "fixed" in 7.3. I think it was Tom who +improved the optimizer to push the where clause into the selects of a union +view. I've done a test... + +create view test as + select updated, invoice_id from invoice + union all + select updated, invoice_id from inv2 + union all + select updated, invoice_id from inv3; + +... and it seems to work (postgresql 7.3 here): + +billing=# explain select * from test where invoice_id = 111000; + QUERY PLAN +---------------------------------------------------------------------------- +---------------- + Subquery Scan test (cost=0.00..413.24 rows=114 width=12) + -> Append (cost=0.00..413.24 rows=114 width=12) + -> Subquery Scan "*SELECT* 1" (cost=0.00..6.00 rows=1 width=12) + -> Index Scan using pk_invoice on invoice (cost=0.00..6.00 +rows=1 width=12) + Index Cond: (invoice_id = 111000) + -> Subquery Scan "*SELECT* 2" (cost=0.00..203.62 rows=57 +width=12) + -> Index Scan using idx_inv2 on inv2 (cost=0.00..203.62 +rows=57 width=12) + Index Cond: (invoice_id = 111000) + -> Subquery Scan "*SELECT* 3" (cost=0.00..203.62 rows=57 +width=12) + -> Index Scan using idx_inv3 on inv3 (cost=0.00..203.62 +rows=57 width=12) + Index Cond: (invoice_id = 111000) +(11 rows) + +I hope this is helps. Can you upgrade to 7.3.1? I really think the upgrade +is worth the effort. + +Best Regards, +Michael Paesold + + +From pgsql-performance-owner@postgresql.org Wed Jan 8 09:08:38 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B1D334763CD + for ; + Wed, 8 Jan 2003 09:08:37 -0500 (EST) +Received: from localhost.localdomain (sein.itera.ee [194.126.109.126]) + by postgresql.org (Postfix) with ESMTP id A3B254762AA + for ; + Wed, 8 Jan 2003 09:08:36 -0500 (EST) +Received: (from hannu@localhost) + by localhost.localdomain (8.11.6/8.11.6) id h08G2G103290; + Wed, 8 Jan 2003 16:02:16 GMT +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: Unions and where optimisation +From: Hannu Krosing +To: Boris Klug +Cc: "pgsql-performance@postgresql.org" +In-Reply-To: <200301081425.48597.boris.klug@control.de> +References: <200301081425.48597.boris.klug@control.de> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1042041735.3237.1.camel@huli> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 08 Jan 2003 16:02:15 +0000 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/54 +X-Sequence-Number: 701 + +On Wed, 2003-01-08 at 13:25, Boris Klug wrote: +> Hello! +> +> I am quite new in the PostgreSQL performance business, done a few years Oracle +> stuff before. My ist question is the following: +> +> We have three table, lets name them rk150, 151 and rk152. They all have a +> timestamp and a order number in common but than different data after this. +> Now I need the data from all tables in one view for a given order number, so +> I created a view +> +> create view orderevents as +> select ts, aufnr from rk150 +> union +> select ts, aufnr from rk151 +> union +> select ts, aufnr from rk152; + +try making the orderevents view like this: + +create view orderevents as +select rk.aufnr, sub.ts + from rk150 rk, + ( select ts from rk150 where aufnr = rk.aufr + union + select ts from rk151 where aufnr = rk.aufr + union + select ts from rk152 where aufnr = rk.aufr + ) as sub +; + +this could/should force your desired behavior. + +> My question now: Is the optimizer able to move the where clause into unions? +> If so, how I can get him to do it? +> +> Thank you for the help in advance! +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Wed Jan 8 11:14:56 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D2ED2476F4C + for ; + Wed, 8 Jan 2003 11:14:54 -0500 (EST) +Received: from benhur.intern.control.de (unknown [217.89.112.10]) + by postgresql.org (Postfix) with ESMTP id 2D19F4763D8 + for ; + Wed, 8 Jan 2003 11:14:15 -0500 (EST) +Received: from devserver (devserver.intern.control.de [192.168.100.5]) + by benhur.intern.control.de (8.12.6/8.12.6/Benhur 8.12.6) with ESMTP id + h08GDVVO030991; Wed, 8 Jan 2003 17:13:32 +0100 +Content-Type: text/plain; + charset="iso-8859-1" +From: Boris Klug +Organization: control IT GmbH +To: "Michael Paesold" , + "Tomasz Myrta" , "Hannu Krosing" +Subject: Re: Unions and where optimisation +Date: Wed, 8 Jan 2003 17:13:00 +0100 +User-Agent: KMail/1.4.3 +Cc: +References: <200301081425.48597.boris.klug@control.de> + <200301081536.33211.boris.klug@control.de> + <013001c2b72d$658ee4b0$3201a8c0@beeblebrox> +In-Reply-To: <013001c2b72d$658ee4b0$3201a8c0@beeblebrox> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301081713.00786.boris.klug@control.de> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/61 +X-Sequence-Number: 708 + +Hello! + +> As far as I know, this has first been "fixed" in 7.3. I think it was Tom +> who improved the optimizer to push the where clause into the selects of a +> union view. I've done a test... + +Yes, I installed 7.3 and it works fine there. I think we will upgrade to 7.= +3.1=20 +our development system soon. + +Thank you! + +--=20 +Dipl. Inform. Boris Klug, control IT GmbH, Germany + +From pgsql-performance-owner@postgresql.org Wed Jan 8 09:56:00 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EE4C4476F5F + for ; + Wed, 8 Jan 2003 09:55:59 -0500 (EST) +Received: from localhost.localdomain (sein.itera.ee [194.126.109.126]) + by postgresql.org (Postfix) with ESMTP id DCBAC476F55 + for ; + Wed, 8 Jan 2003 09:55:58 -0500 (EST) +Received: (from hannu@localhost) + by localhost.localdomain (8.11.6/8.11.6) id h08GnKU03357; + Wed, 8 Jan 2003 16:49:20 GMT +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: Unions and where optimisation +From: Hannu Krosing +To: Tomasz Myrta +Cc: Boris Klug , + "pgsql-performance@postgresql.org" +In-Reply-To: <3E1C366B.5080406@klaster.net> +References: <200301081425.48597.boris.klug@control.de> + <1042041735.3237.1.camel@huli> <3E1C366B.5080406@klaster.net> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1042044560.3237.7.camel@huli> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 08 Jan 2003 16:49:20 +0000 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/58 +X-Sequence-Number: 705 + +On Wed, 2003-01-08 at 14:32, Tomasz Myrta wrote: +> Hannu Krosing wrote: +> +> > +> > try making the orderevents view like this: +> > +> > create view orderevents as +> > select rk.aufnr, sub.ts +> > from rk150 rk, +> > ( select ts from rk150 where aufnr = rk.aufr +> > union +> > select ts from rk151 where aufnr = rk.aufr +> > union +> > select ts from rk152 where aufnr = rk.aufr +> > ) as sub +> > ; +> > +> > this could/should force your desired behavior. +> > +> +> Hannu, does it work? + +Nope! Sorry. + +SQL spec clearly states that subqueries in FROM clause must not see each +other ;( + +It would work in WITH part of the query, which will hopefully be +implemented in some future PG version, perhaps even 7.4 as WITH is the +prerequisite for implementing SQL99 recursive queries, and RedHat has +shown an strongish interest in implementing these. + +> ---------------------------(end of broadcast)--------------------------- +> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Wed Jan 8 10:32:38 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 63B47476EAC + for ; + Wed, 8 Jan 2003 10:32:37 -0500 (EST) +Received: from com.ith.tur.cu (com.ith.tur.cu [212.44.111.34]) + by postgresql.org (Postfix) with ESMTP id 8CBDF476DC8 + for ; + Wed, 8 Jan 2003 10:32:31 -0500 (EST) +Received: from nsoft by com.ith.tur.cu with SMTP (MDaemon.PRO.v6.0.7.R) + for ; Wed, 08 Jan 2003 09:18:31 -0500 +Message-ID: <000901c2b739$ed6df360$8a24a8c0@nsoft> +Reply-To: "enediel" +From: "enediel" +To: "postgresql" +Subject: postgresql in cluster of servers +Date: Wed, 8 Jan 2003 09:18:09 -0800 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 8bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 5.00.2919.6700 +X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6700 +X-Return-Path: enediel@com.ith.tur.cu +X-MDaemon-Deliver-To: pgsql-performance@postgresql.org +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/59 +X-Sequence-Number: 706 + +Hello to all list members: + +I'm looking for information about using postgresql in a cluster of servers +where all real servers share a unique databases location outside them. + +The question could be one of the follows? + +?Is the prostgresql prepared to synchronize simultaneous accesses to oneself +database among processes that run in different PC's? + +or + +?Was the postgresql database designed to allow simultaneous acceses of +processes that run in different PC's allowing for own design the +sincronizationof all the processes? + + +Thanks in advance for the attention +Enediel +Linux user 300141 + +Happy who can penetrate the secret causes of the things +�Use Linux! + + +From pgsql-general-owner@postgresql.org Wed Jan 8 12:33:22 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 282894765C1; Wed, 8 Jan 2003 12:33:21 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 7DE6D476360; Wed, 8 Jan 2003 12:32:28 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h08HWX0U004829; + Wed, 8 Jan 2003 12:32:33 -0500 (EST) +To: pgsql-performance@postgresql.org, pgsql-general@postgresql.org, + pgsql-sql@postgresql.org +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance +In-reply-to: +References: +Comments: In-reply-to Achilleus Mantzios + message dated "Tue, 07 Jan 2003 20:38:17 -0200" +Date: Wed, 08 Jan 2003 12:32:33 -0500 +Message-ID: <4828.1042047153@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/297 +X-Sequence-Number: 35418 + +Just to close off the thread, here is the end-result of investigating +Achilleus Mantzios' problem. + +------- Forwarded Message + +Date: Wed, 08 Jan 2003 11:54:36 -0500 +From: Tom Lane +To: Achilleus Mantzios +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance + +I believe I see what's going on. You have a number of silly outlier +values in the report_date column --- quite a few instances of '10007-06-09' +for example. Depending on whether ANALYZE's random sample happens to +include one of these, the histogram generated by ANALYZE might look like +this (it took about half a dozen tries with ANALYZE to get this result): + +dynacom=# analyze noon; +ANALYZE +dynacom=# select histogram_bounds from pg_stats where attname = 'report_date'; + histogram_bounds +----------------------------------------------------------------------------------------------------------------------------- + {1969-06-26,1994-09-24,1996-04-05,1997-07-21,1998-08-27,1999-03-13,1999-11-11,2000-08-18,2001-04-18,2002-01-04,10007-06-09} +(1 row) + +in which case we get this: + +dynacom=# EXPLAIN select * from noon where +dynacom-# report_date between '2002-01-07' and '2003-01-07'; + QUERY PLAN +--------------------------------------------------------------------------------------------- + Index Scan using noonf_date on noon (cost=0.00..4.08 rows=1 width=1975) + Index Cond: ((report_date >= '2002-01-07'::date) AND (report_date <= '2003-01-07'::date)) +(2 rows) + +Seeing this histogram, the planner assumes that one-tenth of the table +is uniformly distributed between 2002-01-04 and 10007-06-09, which leads +it to the conclusion that the range between 2002-01-07 and 2003-01-07 +probably contains only about one row, which causes it to prefer a scan +on report_date rather than on v_code. + +The reason the problem comes and goes is that any given ANALYZE run +might or might not happen across one of the outliers. When it doesn't, +you get a histogram that leads to reasonably accurate estimates. + +There are a couple of things you could do about this. One is to +increase the statistics target for report_date (see ALTER TABLE SET +STATISTICS) so that a finer-grained histogram is generated for the +report_date column. The other thing, which is more work but probably +the best answer in the long run, is to fix the outliers, which I imagine +must be incorrect entries. + +You could perhaps put a constraint on report_date to prevent bogus +entries from sneaking in in future. + +It looks like increasing the stats target would be worth doing also, +if you make many queries using ranges of report_date. + + regards, tom lane + +------- End of Forwarded Message + +From pgsql-general-owner@postgresql.org Wed Jan 8 08:45:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id DF4BC47685E; Wed, 8 Jan 2003 08:45:13 -0500 (EST) +Received: from matrix.gatewaynet.com (unknown [217.19.69.50]) + by postgresql.org (Postfix) with ESMTP + id AC2154767AA; Wed, 8 Jan 2003 08:45:12 -0500 (EST) +Received: from matrix.gatewaynet.com (matrix.gatewaynet.com [217.19.69.50]) + by matrix.gatewaynet.com (8.12.5/8.12.5) with ESMTP id h08HrvXR014444; + Wed, 8 Jan 2003 15:53:57 -0200 +Received: from localhost (achill@localhost) + by matrix.gatewaynet.com (8.12.5/8.12.5/Submit) with ESMTP id + h08Hrs5Q014440; Wed, 8 Jan 2003 15:53:54 -0200 +Date: Wed, 8 Jan 2003 15:53:54 -0200 (GMT+2) +From: Achilleus Mantzios +To: Tom Lane +Cc: Rod Taylor , Stephan Szabo , + Pgsql Performance , + , +Subject: Re: [SQL] [PERFORM] 7.3.1 index use / performance +In-Reply-To: <19889.1041967568@sss.pgh.pa.us> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/287 +X-Sequence-Number: 35408 + +On Tue, 7 Jan 2003, Tom Lane wrote: + +> Rod Taylor writes: +> >> I am wondering about a compiler bug, or some other peculiarity on your +> >> platform. Can anyone else using FreeBSD try the above experiment and +> >> see if they get different results from mine on 7.3.* (or CVS tip)? +> +> > On FreeBSD 4.7 I received the exact same results as Tom using the +> > statements shown by Tom. +> +> On looking at the code, I do see part of a possible mechanism for this +> behavior: cost_index calculates the estimated cost for qual-clause +> evaluation like this: +> + +This bizarre index decreased cost (when adding conditions) behaviour maybe +was due to some vacuums. +(i cant remember how many reloads and vacuums i did to the database +in the period petween the two emails). + +However my linux machine with the same pgsql 7.3.1, with a full clean +installation also gives the same symptoms: +Choosing the slow index, and after some (random) +vacuums choosing the right index, and then after some vacuums chooses the +bad +index again. + + +> +> regards, tom lane +> + +================================================================== +Achilleus Mantzios +S/W Engineer +IT dept +Dynacom Tankers Mngmt +Nikis 4, Glyfada +Athens 16610 +Greece +tel: +30-10-8981112 +fax: +30-10-8981877 +email: achill@matrix.gatewaynet.com + mantzios@softlab.ece.ntua.gr + + +From pgsql-performance-owner@postgresql.org Wed Jan 8 14:05:48 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3579D475FFE + for ; + Wed, 8 Jan 2003 14:05:48 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 034634764E4 + for ; + Wed, 8 Jan 2003 14:05:26 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2307618; Wed, 08 Jan 2003 11:05:29 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: "enediel" , + "postgresql" +Subject: Re: postgresql in cluster of servers +Date: Wed, 8 Jan 2003 11:08:13 -0800 +X-Mailer: KMail [version 1.4] +References: <000901c2b739$ed6df360$8a24a8c0@nsoft> +In-Reply-To: <000901c2b739$ed6df360$8a24a8c0@nsoft> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301081108.13422.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/63 +X-Sequence-Number: 710 + + +Enediel, + +> ?Was the postgresql database designed to allow simultaneous acceses of +> processes that run in different PC's allowing for own design the +> sincronizationof all the processes? + +No, unless I'm really out of the loop.=20 + +However, I believe that some/all of the commercial companies who offer=20 +PostgreSQL-based solutions offer extensions/versions of Postgres that do=20 +this. I suggest that you contact: + +PostgreSQL Inc. +Command Prompt Inc. +Red Hat (Red Hat Database) + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Wed Jan 8 16:14:53 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CDEEF475E3E + for ; + Wed, 8 Jan 2003 16:14:52 -0500 (EST) +Received: from lakemtao02.cox.net (lakemtao02.cox.net [68.1.17.243]) + by postgresql.org (Postfix) with ESMTP id 44225475D1C + for ; + Wed, 8 Jan 2003 16:14:52 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao02.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030108211451.MNMM2203.lakemtao02.cox.net@[192.168.1.1]> + for ; + Wed, 8 Jan 2003 16:14:51 -0500 +Subject: Re: postgresql in cluster of servers +From: Ron Johnson +To: postgresql +In-Reply-To: <000901c2b739$ed6df360$8a24a8c0@nsoft> +References: <000901c2b739$ed6df360$8a24a8c0@nsoft> +Content-Type: text/plain +Organization: +Message-Id: <1042060491.7864.162.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 08 Jan 2003 15:14:52 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/64 +X-Sequence-Number: 711 + +On Wed, 2003-01-08 at 11:18, enediel wrote: +> Hello to all list members: +> +> I'm looking for information about using postgresql in a cluster of servers +> where all real servers share a unique databases location outside them. +> +> The question could be one of the follows? +> +> ?Is the prostgresql prepared to synchronize simultaneous accesses to oneself +> database among processes that run in different PC's? +> +> or +> +> ?Was the postgresql database designed to allow simultaneous acceses of +> processes that run in different PC's allowing for own design the +> sincronizationof all the processes? + +To clarify: do you mean + +(1) multiple copies of *the*same*database* sitting on many machines, +and all of them synchronizing themselves? + + OR + +(2) multiple application server machines all hitting a single database +sitting on a single database server machine? + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Wed Jan 8 18:38:56 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0234F475E31 + for ; + Wed, 8 Jan 2003 18:38:55 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 5D2D0475D3B + for ; + Wed, 8 Jan 2003 18:38:54 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030108233856.ZRTS26808.lakemtao03.cox.net@[192.168.1.1]> + for ; + Wed, 8 Jan 2003 18:38:56 -0500 +Subject: Re: Fw: postgresql in cluster of servers +From: Ron Johnson +To: postgresql +In-Reply-To: <018901c2b781$5576d2f0$8a24a8c0@nsoft> +References: <018901c2b781$5576d2f0$8a24a8c0@nsoft> +Content-Type: text/plain; charset=ISO-8859-1 +Organization: +Message-Id: <1042069134.7864.205.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 08 Jan 2003 17:38:54 -0600 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/66 +X-Sequence-Number: 713 + +On Wed, 2003-01-08 at 19:49, enediel wrote: +> Thanks for all answers: +> Ron Johnson, I mean the second option thet you wrote: +> +> (2) multiple application server machines all hitting a single database +> sitting on a single database server machine? + +Ok, great. To the PG server, the app servers are db clients, just like +any other client. Multi-user access, arranged so that users don't step +over each other, is integrated deeply into the server. + +Thus, PostgreSQL meets this qualification... + +> Happy who can penetrate the secret causes of the things +> �Use Linux! +> ----- Original Message ----- +> From: "Ron Johnson" +> To: "postgresql" +> Sent: Wednesday, January 08, 2003 1:14 PM +> Subject: Re: [PERFORM] postgresql in cluster of servers +> +> +> > On Wed, 2003-01-08 at 11:18, enediel wrote: +> > > Hello to all list members: +> > > +> > > I'm looking for information about using postgresql in a cluster of +> servers +> > > where all real servers share a unique databases location outside them. +> > > +> > > The question could be one of the follows? +> > > +> > > ?Is the prostgresql prepared to synchronize simultaneous accesses to +> oneself +> > > database among processes that run in different PC's? +> > > +> > > or +> > > +> > > ?Was the postgresql database designed to allow simultaneous acceses of +> > > processes that run in different PC's allowing for own design the +> > > sincronizationof all the processes? +> > +> > To clarify: do you mean +> > +> > (1) multiple copies of *the*same*database* sitting on many machines, +> > and all of them synchronizing themselves? +> > +> > OR +> > +> > (2) multiple application server machines all hitting a single database +> > sitting on a single database server machine? + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Wed Jan 8 17:47:44 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7CD0A475D3B + for ; + Wed, 8 Jan 2003 17:47:42 -0500 (EST) +Received: from com.ith.tur.cu (com.ith.tur.cu [212.44.111.34]) + by postgresql.org (Postfix) with ESMTP id 4C431475D1C + for ; + Wed, 8 Jan 2003 17:47:38 -0500 (EST) +Received: from nsoft by com.ith.tur.cu with SMTP (MDaemon.PRO.v6.0.7.R) + for ; Wed, 08 Jan 2003 17:49:38 -0500 +Message-ID: <018901c2b781$5576d2f0$8a24a8c0@nsoft> +Reply-To: "enediel" +From: "enediel" +To: "postgresql" +Subject: Fw: postgresql in cluster of servers +Date: Wed, 8 Jan 2003 17:49:21 -0800 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 8bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 5.00.2919.6700 +X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6700 +X-Return-Path: enediel@com.ith.tur.cu +X-MDaemon-Deliver-To: pgsql-performance@postgresql.org +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/65 +X-Sequence-Number: 712 + +Thanks for all answers: +Ron Johnson, I mean the second option thet you wrote: + +(2) multiple application server machines all hitting a single database +sitting on a single database server machine? + +Greetings +Enediel +Linux user 300141 + +Happy who can penetrate the secret causes of the things +�Use Linux! +----- Original Message ----- +From: "Ron Johnson" +To: "postgresql" +Sent: Wednesday, January 08, 2003 1:14 PM +Subject: Re: [PERFORM] postgresql in cluster of servers + + +> On Wed, 2003-01-08 at 11:18, enediel wrote: +> > Hello to all list members: +> > +> > I'm looking for information about using postgresql in a cluster of +servers +> > where all real servers share a unique databases location outside them. +> > +> > The question could be one of the follows? +> > +> > ?Is the prostgresql prepared to synchronize simultaneous accesses to +oneself +> > database among processes that run in different PC's? +> > +> > or +> > +> > ?Was the postgresql database designed to allow simultaneous acceses of +> > processes that run in different PC's allowing for own design the +> > sincronizationof all the processes? +> +> To clarify: do you mean +> +> (1) multiple copies of *the*same*database* sitting on many machines, +> and all of them synchronizing themselves? +> +> OR +> +> (2) multiple application server machines all hitting a single database +> sitting on a single database server machine? +> +> -- +> +------------------------------------------------------------+ +> | Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +> | Jefferson, LA USA http://members.cox.net/ron.l.johnson | +> | | +> | "Basically, I got on the plane with a bomb. Basically, I | +> | tried to ignite it. Basically, yeah, I intended to damage | +> | the plane." | +> | RICHARD REID, who tried to blow up American Airlines | +> | Flight 63 | +> +------------------------------------------------------------+ +> +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org +> + + +From pgsql-performance-owner@postgresql.org Thu Jan 9 12:20:36 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1626D475FEB + for ; + Thu, 9 Jan 2003 12:20:35 -0500 (EST) +Received: from jobs1.unisoftbg.com (unknown [194.12.229.208]) + by postgresql.org (Postfix) with SMTP id C9FF8475FC6 + for ; + Thu, 9 Jan 2003 12:20:31 -0500 (EST) +Received: (qmail 16695 invoked from network); 9 Jan 2003 19:00:58 -0000 +Received: from unisoft.unisoftbg.com (HELO t1.unisoftbg.com) (194.12.229.193) + by 0 with SMTP; 9 Jan 2003 19:00:58 -0000 +Message-ID: <3E1DA1B9.E19B6C02@t1.unisoftbg.com> +Date: Thu, 09 Jan 2003 17:22:17 +0100 +From: pginfo +X-Mailer: Mozilla 4.03 [en] (Win95; I) +MIME-Version: 1.0 +To: enediel +Cc: postgresql +Subject: Re: Fw: postgresql in cluster of servers +References: <018901c2b781$5576d2f0$8a24a8c0@nsoft> +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/67 +X-Sequence-Number: 714 + +Hi, + +I think if we speak about single db server you will nead to ask +the app. server provider about clustering. + +I am working with jboss and it is supporting clustering. + + +regards, +ivan. + +enediel wrote: + +> Thanks for all answers: +> Ron Johnson, I mean the second option thet you wrote: +> +> (2) multiple application server machines all hitting a single database +> sitting on a single database server machine? +> +> Greetings +> Enediel +> Linux user 300141 +> +> Happy who can penetrate the secret causes of the things +> �Use Linux! +> ----- Original Message ----- +> From: "Ron Johnson" +> To: "postgresql" +> Sent: Wednesday, January 08, 2003 1:14 PM +> Subject: Re: [PERFORM] postgresql in cluster of servers +> +> > On Wed, 2003-01-08 at 11:18, enediel wrote: +> > > Hello to all list members: +> > > +> > > I'm looking for information about using postgresql in a cluster of +> servers +> > > where all real servers share a unique databases location outside them. +> > > +> > > The question could be one of the follows? +> > > +> > > ?Is the prostgresql prepared to synchronize simultaneous accesses to +> oneself +> > > database among processes that run in different PC's? +> > > +> > > or +> > > +> > > ?Was the postgresql database designed to allow simultaneous acceses of +> > > processes that run in different PC's allowing for own design the +> > > sincronizationof all the processes? +> > +> > To clarify: do you mean +> > +> > (1) multiple copies of *the*same*database* sitting on many machines, +> > and all of them synchronizing themselves? +> > +> > OR +> > +> > (2) multiple application server machines all hitting a single database +> > sitting on a single database server machine? +> > +> > -- +> > +------------------------------------------------------------+ +> > | Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +> > | Jefferson, LA USA http://members.cox.net/ron.l.johnson | +> > | | +> > | "Basically, I got on the plane with a bomb. Basically, I | +> > | tried to ignite it. Basically, yeah, I intended to damage | +> > | the plane." | +> > | RICHARD REID, who tried to blow up American Airlines | +> > | Flight 63 | +> > +------------------------------------------------------------+ +> > +> > +> > ---------------------------(end of broadcast)--------------------------- +> > TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org +> > +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 2: you can get off all lists at once with the unregister command +> (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) + + + + +From pgsql-performance-owner@postgresql.org Thu Jan 9 15:27:45 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4648B475DA7 + for ; + Thu, 9 Jan 2003 15:27:44 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id A93B1475CB4 + for ; + Thu, 9 Jan 2003 15:27:43 -0500 (EST) +Received: from css120.ihs.com (css120.ihs.com [170.207.105.120]) + by mail1.ihs.com (8.12.6/8.12.6) with ESMTP id h09KOsgS004117; + Thu, 9 Jan 2003 13:24:57 -0700 (MST) +Date: Thu, 9 Jan 2003 13:18:36 -0700 (MST) +From: "scott.marlowe" +To: enediel +Cc: postgresql +Subject: Re: Fw: Fw: postgresql in cluster of servers +In-Reply-To: <006f01c2b81f$89508e10$8a24a8c0@nsoft> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-MailScanner: Found to be clean +X-MailScanner-SpamCheck: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/69 +X-Sequence-Number: 716 + +On Thu, 9 Jan 2003, enediel wrote: + +> No, pginfo, suposse this example +> +> Web server or cluster web server, it's unimportant +> | +> Postgresql cluster server containing{ +> ... +> Real server 1 running postgresql processes +> Real server 2 running postgresql processes +> .... +> } +> | +> File server machine that contains all pg_databases +> +> Notice that the real servers don't have in their hard disk any database, +> they could have a link to the hard disk in the File server machine. + +Postgresql cannot currently work this way. + +It uses shared memory on a single image OS to maintain the database +coherently. when you cluster Postgresql across multiple machines, +currently you have to have two seperate and independant instances which +are synchronized by an external process of some sort. + +since I/O is usually the single limiting factor, your suggested system +would likely be no faster than a single box with decent memory and CPUs in +it. + + +From pgsql-performance-owner@postgresql.org Thu Jan 9 12:40:15 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A1D36476115 + for ; + Thu, 9 Jan 2003 12:40:14 -0500 (EST) +Received: from com.ith.tur.cu (com.ith.tur.cu [212.44.111.34]) + by postgresql.org (Postfix) with ESMTP id 1020D476085 + for ; + Thu, 9 Jan 2003 12:40:11 -0500 (EST) +Received: from nsoft by com.ith.tur.cu with SMTP (MDaemon.PRO.v6.0.7.R) + for ; Thu, 09 Jan 2003 12:42:01 -0500 +Message-ID: <006f01c2b81f$89508e10$8a24a8c0@nsoft> +Reply-To: "enediel" +From: "enediel" +To: "postgresql" +Subject: Fw: Fw: postgresql in cluster of servers +Date: Thu, 9 Jan 2003 12:41:44 -0800 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 8bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 5.00.2919.6700 +X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6700 +X-Return-Path: enediel@com.ith.tur.cu +X-MDaemon-Deliver-To: pgsql-performance@postgresql.org +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/68 +X-Sequence-Number: 715 + +No, pginfo, suposse this example + +Web server or cluster web server, it's unimportant +| +Postgresql cluster server containing{ + ... + Real server 1 running postgresql processes + Real server 2 running postgresql processes + .... +} +| +File server machine that contains all pg_databases + +Notice that the real servers don't have in their hard disk any database, +they could have a link to the hard disk in the File server machine. + +The syncronization between postgresql processes that are running on +different machines and using the same database is my question. + +Thanks for the answer + +Greetings +Enediel +Linux user 300141 + +Happy who can penetrate the secret causes of the things +�Use Linux! +----- Original Message ----- +From: "pginfo" +To: "enediel" +Sent: Thursday, January 09, 2003 8:21 AM +Subject: Re: Fw: [PERFORM] postgresql in cluster of servers + + +> Hi, +> +> I think if we speak about single db server you will nead to ask +> the app. server provider about clustering. +> +> I am working with jboss and it is supporting clustering. +> +> +> regards, +> ivan. +> +> enediel wrote: +> +> > Thanks for all answers: +> > Ron Johnson, I mean the second option thet you wrote: +> > +> > (2) multiple application server machines all hitting a single database +> > sitting on a single database server machine? +> > +> > Greetings +> > Enediel +> > Linux user 300141 +> > +> > Happy who can penetrate the secret causes of the things +> > �Use Linux! +> > ----- Original Message ----- +> > From: "Ron Johnson" +> > To: "postgresql" +> > Sent: Wednesday, January 08, 2003 1:14 PM +> > Subject: Re: [PERFORM] postgresql in cluster of servers +> > +> > > On Wed, 2003-01-08 at 11:18, enediel wrote: +> > > > Hello to all list members: +> > > > +> > > > I'm looking for information about using postgresql in a cluster of +> > servers +> > > > where all real servers share a unique databases location outside +them. +> > > > +> > > > The question could be one of the follows? +> > > > +> > > > ?Is the prostgresql prepared to synchronize simultaneous accesses to +> > oneself +> > > > database among processes that run in different PC's? +> > > > +> > > > or +> > > > +> > > > ?Was the postgresql database designed to allow simultaneous acceses +of +> > > > processes that run in different PC's allowing for own design the +> > > > sincronizationof all the processes? +> > > +> > > To clarify: do you mean +> > > +> > > (1) multiple copies of *the*same*database* sitting on many machines, +> > > and all of them synchronizing themselves? +> > > +> > > OR +> > > +> > > (2) multiple application server machines all hitting a single database +> > > sitting on a single database server machine? +> > > +> > > -- +> > > +------------------------------------------------------------+ +> > > | Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +> > > | Jefferson, LA USA http://members.cox.net/ron.l.johnson | +> > > | | +> > > | "Basically, I got on the plane with a bomb. Basically, I | +> > > | tried to ignite it. Basically, yeah, I intended to damage | +> > > | the plane." | +> > > | RICHARD REID, who tried to blow up American Airlines | +> > > | Flight 63 | +> > > +------------------------------------------------------------+ +> > > +> > > +> > > ---------------------------(end of +broadcast)--------------------------- +> > > TIP 1: subscribe and unsubscribe commands go to +majordomo@postgresql.org +> > > +> > +> > ---------------------------(end of broadcast)--------------------------- +> > TIP 2: you can get off all lists at once with the unregister command +> > (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) +> + + +From pgsql-performance-owner@postgresql.org Thu Jan 9 16:33:39 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4D0E4475E18 + for ; + Thu, 9 Jan 2003 16:33:38 -0500 (EST) +Received: from com.ith.tur.cu (com.ith.tur.cu [212.44.111.34]) + by postgresql.org (Postfix) with ESMTP id 1C40E475CB4 + for ; + Thu, 9 Jan 2003 16:33:35 -0500 (EST) +Received: from nsoft by com.ith.tur.cu with SMTP (MDaemon.PRO.v6.0.7.R) + for ; Thu, 09 Jan 2003 16:35:14 -0500 +Message-ID: <00d701c2b840$1dbedaa0$8a24a8c0@nsoft> +Reply-To: "enediel" +From: "enediel" +To: "postgresql" +Subject: Fw: Fw: Fw: postgresql in cluster of servers +Date: Thu, 9 Jan 2003 16:35:01 -0800 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 8bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 5.00.2919.6700 +X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6700 +X-Return-Path: enediel@com.ith.tur.cu +X-MDaemon-Deliver-To: pgsql-performance@postgresql.org +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/70 +X-Sequence-Number: 717 + +Thanks for the answer scott.marlowe +I'm agree with you about the limit of the I/O operations with this +configuration. + +I'm just looking for a fault tolerance configuration in the databases +server, considering a very large databases, and a lot of users accesing to +them. + +I'll accept with pleasure any suggestions about this topic. + +Greetings +Enediel +Linux user 300141 + +Happy who can penetrate the secret causes of the things +�Use Linux! + + +From pgsql-performance-owner@postgresql.org Sat Jan 11 13:53:52 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C4DEB475E84 + for ; + Sat, 11 Jan 2003 13:53:50 -0500 (EST) +Received: from pd2mo3so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net + [24.71.223.10]) by postgresql.org (Postfix) with ESMTP id 357AB475BA0 + for ; + Sat, 11 Jan 2003 13:53:50 -0500 (EST) +Received: from pd5mr4so.prod.shaw.ca + (pd5mr4so-qfe3.prod.shaw.ca [10.0.141.168]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H8K00LQRCHQP9@l-daemon> for + pgsql-performance@postgresql.org; + Sat, 11 Jan 2003 11:53:50 -0700 (MST) +Received: from pn2ml5so.prod.shaw.ca + (pn2ml5so-qfe0.prod.shaw.ca [10.0.121.149]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H8K0065MCHQ78@l-daemon> for + pgsql-performance@postgresql.org; + Sat, 11 Jan 2003 11:53:50 -0700 (MST) +Received: from kimiko (h24-78-132-76.vc.shawcable.net [24.78.132.76]) + by l-daemon (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 + 2002)) with SMTP id <0H8K006JTCHPEX@l-daemon> for + pgsql-performance@postgresql.org; + Sat, 11 Jan 2003 11:53:50 -0700 (MST) +Date: Sat, 11 Jan 2003 10:51:44 -0800 +From: Vernon Wu +Subject: "IN" or "=" and "OR" +To: pgsql-performance@postgresql.org +Reply-To: vernonw@gatewaytech.com +Message-id: +MIME-version: 1.0 +X-Mailer: Opera 6.05 build 1140 +Content-type: text/plain; charset=iso-8859-1 +Content-transfer-encoding: 7BIT +X-Priority: 3 (Normal) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/71 +X-Sequence-Number: 718 + + +Which query statement is better in terms of preformance ? + +select ... from table1 where field1 in ('a', 'b', 'c') + +select ... from table1 where field1='a' or field1='b' or field1='c' + +Thanks. + + + +From pgsql-performance-owner@postgresql.org Sat Jan 11 20:03:28 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B22AE475B47 + for ; + Sat, 11 Jan 2003 20:03:26 -0500 (EST) +Received: from bob.samurai.com (bob.samurai.com [205.207.28.75]) + by postgresql.org (Postfix) with ESMTP id 15D5D47592C + for ; + Sat, 11 Jan 2003 20:03:26 -0500 (EST) +Received: from DU150.N224.ResNet.QueensU.CA (DU150.N224.ResNet.QueensU.CA + [130.15.224.150]) by bob.samurai.com (Postfix) with ESMTP + id 1FDED1D5D; Sat, 11 Jan 2003 20:03:28 -0500 (EST) +Subject: Re: join over 12 tables takes 3 secs to plan +From: Neil Conway +To: "Charles H. Woloszynski" +Cc: Hilmar Lapp , Jeff , + "pgsql-performance@postgresql.org" +In-Reply-To: <3E160BC0.3020900@clearmetrix.com> +References: + <3E160BC0.3020900@clearmetrix.com> +Content-Type: text/plain +Organization: +Message-Id: <1042333405.386.49.camel@tokyo> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 11 Jan 2003 20:03:25 -0500 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/72 +X-Sequence-Number: 719 + +On Fri, 2003-01-03 at 17:16, Charles H. Woloszynski wrote: +> I think the functionality is starting to become real, but it looks like +> it is starting with some limitations that might restricts its use from +> be maximally realized until 7.4 (or beyond). + +Specifically, which limitations in this feature would you like to see +corrected? + +Cheers, + +Neil +-- +Neil Conway || PGP Key ID: DB3C29FC + + + + +From pgsql-performance-owner@postgresql.org Sat Jan 11 23:10:53 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A155447627F + for ; + Sat, 11 Jan 2003 23:10:52 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id EEBE14761E9 + for ; + Sat, 11 Jan 2003 23:10:51 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0C4As5u025122; + Sat, 11 Jan 2003 23:10:54 -0500 (EST) +To: vernonw@gatewaytech.com +Cc: pgsql-performance@postgresql.org +Subject: Re: "IN" or "=" and "OR" +In-reply-to: +References: +Comments: In-reply-to Vernon Wu + message dated "Sat, 11 Jan 2003 10:51:44 -0800" +Date: Sat, 11 Jan 2003 23:10:53 -0500 +Message-ID: <25121.1042344653@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/73 +X-Sequence-Number: 720 + +Vernon Wu writes: +> Which query statement is better in terms of preformance ? +> select ... from table1 where field1 in ('a', 'b', 'c') +> select ... from table1 where field1='a' or field1='b' or field1='c' + +There is no difference, other than the microseconds the parser spends +transforming form 1 into form 2 ... + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Sun Jan 12 10:52:25 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 19846475E26 + for ; + Sun, 12 Jan 2003 10:52:23 -0500 (EST) +Received: from clearmetrix.com (unknown [209.92.142.67]) + by postgresql.org (Postfix) with ESMTP id F0633475D00 + for ; + Sun, 12 Jan 2003 10:52:22 -0500 (EST) +Received: from clearmetrix.com (chw.muvpn.clearmetrix.com [172.16.1.3]) + by clearmetrix.com (8.11.6/linuxconf) with ESMTP id h0CFqOM26295; + Sun, 12 Jan 2003 10:52:24 -0500 +Message-ID: <3E218F2B.8030107@clearmetrix.com> +Date: Sun, 12 Jan 2003 10:52:11 -0500 +From: "Charles H. Woloszynski" +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; + rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Neil Conway +Cc: Hilmar Lapp , Jeff , + "pgsql-performance@postgresql.org" +Subject: Re: join over 12 tables takes 3 secs to plan +References: + <3E160BC0.3020900@clearmetrix.com> <1042333405.386.49.camel@tokyo> +In-Reply-To: <1042333405.386.49.camel@tokyo> +Content-Type: text/plain; charset=ISO-8859-1; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/74 +X-Sequence-Number: 721 + +Neil: + +I think that general use of this feature should be enabled using the +URL, not with an API call. We use a JDBC connection pool and it will +help tremendously to have the pool set to user server-side preparing +without having to downcast the connection to a PG connection (which I +think is an issue because of the facade in our connection pool code). + +The second item is that of compatibility. If the new code cannot handle +all statements (eg. something with a semi in it) and disable the +generation of a 'prepare' then we cannot count on the URL functionality. + As I understand it, the programmer is required currently to +enable/disable the server-side functionality by hand and only when the +statement to be prepared is not composite (statement1; statement2; +statement2). + +But in our real-world application space, we use a connection pool with a +facade, so getting to the actual connection to enable this is +problematic (and forces postgresql-specific coding into our framework +where it is not particularly welcome). If we overcame this issue, we +would then need to hand-manage the enable/disable to only be used when +the statement is appropriately formulated (e.g., no semicolons in the +statement). + +If we could get URL enabling and auto-detection of statements that won't +work (and hence disable the enabled function for these functions), I +think we have a solution that can be deployed into 'generic' app server +environments with just configuration changes. That is, an operations +person could enable this feature and monitor its impact on performance +to see if/how it helps. That is a BIG win (at least to me) and a HUGE +marketing item. I'd love to test MySQL with some joins over JDBC with +PostgreSQL with some joins using prepared statements and be able to +demonstrate the big improvement that this makes. + +As I understand it, the functions I am waiting for are targeted into 7.4 +(but I'd love to see them early and do some testing of those for the +community). + +Charlie + + +Neil Conway wrote: + +>On Fri, 2003-01-03 at 17:16, Charles H. Woloszynski wrote: +> +> +>>I think the functionality is starting to become real, but it looks like +>>it is starting with some limitations that might restricts its use from +>>be maximally realized until 7.4 (or beyond). +>> +>> +> +>Specifically, which limitations in this feature would you like to see +>corrected? +> +>Cheers, +> +>Neil +> +> + +-- + + +Charles H. Woloszynski + +ClearMetrix, Inc. +115 Research Drive +Bethlehem, PA 18015 + +tel: 610-419-2210 x400 +fax: 240-371-3256 +web: www.clearmetrix.com + + + + + + +From pgsql-jdbc-owner@postgresql.org Mon Jan 13 08:08:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 226E0476AF2 + for ; Mon, 13 Jan 2003 08:08:16 -0500 (EST) +Received: from clearmetrix.com (unknown [209.92.142.67]) + by postgresql.org (Postfix) with ESMTP id 1880E476AA2 + for ; Mon, 13 Jan 2003 08:08:15 -0500 (EST) +Received: from clearmetrix.com (chw.muvpn.clearmetrix.com [172.16.1.3]) + by clearmetrix.com (8.11.6/linuxconf) with ESMTP id h0DD8DM29519; + Mon, 13 Jan 2003 08:08:13 -0500 +Message-ID: <3E22BA32.3030905@clearmetrix.com> +Date: Mon, 13 Jan 2003 08:08:02 -0500 +From: "Charles H. Woloszynski" +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; + rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Neil Conway +Subject: Re: [PERFORM] join over 12 tables takes 3 secs to plan +References: + <3E160BC0.3020900@clearmetrix.com> <1042333405.386.49.camel@tokyo> + <3E218F2B.8030107@clearmetrix.com> <1042399760.362.26.camel@tokyo> +In-Reply-To: <1042399760.362.26.camel@tokyo> +Content-Type: text/plain; charset=ISO-8859-1; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/144 +X-Sequence-Number: 5994 + +Neil: + +Thanks for the feedback. I've attached my original text to this note +and re-posted it back to pgsql-jdbc to make sure that they are aware of +them. I look forward to this new and improved server-side preparation. + +Charlie + +Neil Conway wrote: + +>On Sun, 2003-01-12 at 10:52, Charles H. Woloszynski wrote: +> +> +>>As I understand it, the functions I am waiting for are targeted into 7.4 +>>(but I'd love to see them early and do some testing of those for the +>>community). +>> +>> +> +>Ok -- those are pretty much all features on the JDBC side of things (not +>the backend implementation of PREPARE/EXECUTE). I'm not sure how much of +>that is planned for 7.4: if you haven't talked to the JDBC guys about +>it, they may not be aware of your comments. +> +>Cheers, +> +>Neil +> +> +Charles H. Woloszynski wrote: + +> Neil: +> +> I think that general use of this feature should be enabled using the +> URL, not with an API call. We use a JDBC connection pool and it will +> help tremendously to have the pool set to user server-side preparing +> without having to downcast the connection to a PG connection (which I +> think is an issue because of the facade in our connection pool code). +> The second item is that of compatibility. If the new code cannot +> handle all statements (eg. something with a semi in it) and disable +> the generation of a 'prepare' then we cannot count on the URL +> functionality. As I understand it, the programmer is required +> currently to enable/disable the server-side functionality by hand and +> only when the statement to be prepared is not composite (statement1; +> statement2; statement2). +> +> But in our real-world application space, we use a connection pool with +> a facade, so getting to the actual connection to enable this is +> problematic (and forces postgresql-specific coding into our framework +> where it is not particularly welcome). If we overcame this issue, we +> would then need to hand-manage the enable/disable to only be used when +> the statement is appropriately formulated (e.g., no semicolons in the +> statement). +> +> If we could get URL enabling and auto-detection of statements that +> won't work (and hence disable the enabled function for these +> functions), I think we have a solution that can be deployed into +> 'generic' app server environments with just configuration changes. +> That is, an operations person could enable this feature and monitor +> its impact on performance to see if/how it helps. That is a BIG win +> (at least to me) and a HUGE marketing item. I'd love to test MySQL +> with some joins over JDBC with PostgreSQL with some joins using +> prepared statements and be able to demonstrate the big improvement +> that this makes. +> +> As I understand it, the functions I am waiting for are targeted into +> 7.4 (but I'd love to see them early and do some testing of those for +> the community). + + + + +-- + + +Charles H. Woloszynski + +ClearMetrix, Inc. +115 Research Drive +Bethlehem, PA 18015 + +tel: 610-419-2210 x400 +fax: 240-371-3256 +web: www.clearmetrix.com + + + + + + +From pgsql-performance-owner@postgresql.org Mon Jan 13 13:38:52 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E83AC476C2C + for ; + Mon, 13 Jan 2003 13:38:51 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 5BB8C476B4D + for ; + Mon, 13 Jan 2003 13:38:51 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2312235 for pgsql-performance@postgresql.org; + Mon, 13 Jan 2003 10:38:55 -0800 +Content-Type: text/plain; + charset="us-ascii" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: pgsql-performance@postgresql.org +Subject: Accessing ANALYZE stats +Date: Mon, 13 Jan 2003 10:42:01 -0800 +X-Mailer: KMail [version 1.4] +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301131042.01831.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/75 +X-Sequence-Number: 722 + +Folks, + +Can someone give me a quick pointer on where the ANALYZE stats are kept in= +=20 +7.2.3? Thanks. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 13:42:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EEF05475EE4 + for ; + Tue, 14 Jan 2003 13:42:52 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 5A4D9475E10 + for ; + Tue, 14 Jan 2003 13:42:52 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2313566; Tue, 14 Jan 2003 10:42:54 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Tomasz Myrta , + PgSQL Performance ML +Subject: Re: complicated queries in pl/pgsql +Date: Mon, 13 Jan 2003 10:44:50 -0800 +X-Mailer: KMail [version 1.4] +References: <3E23EC83.9060802@klaster.net> +In-Reply-To: <3E23EC83.9060802@klaster.net> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301131044.50424.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/104 +X-Sequence-Number: 751 + + Tomasz, + +> What happens to view planning - is it performed=20 +> during view creation, or rather each time view is quered? + +Each time the view is executed. The only savings in running a view over a= +=20 +regular query is that the view will have taken care of some reference=20 +expansion and JOIN explication during the CREATE process, but not planning.= +=20=20 +Also, views can actually be slower if the view is complex enough that any= +=20 +query-time parameters cannot be "pushed down" into the view. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Mon Jan 13 13:47:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E5FFC477017 + for ; + Mon, 13 Jan 2003 13:47:06 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id B800C476F4C + for ; + Mon, 13 Jan 2003 13:46:10 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 94969D605; Mon, 13 Jan 2003 10:46:10 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 8A16C5C02; Mon, 13 Jan 2003 10:46:10 -0800 (PST) +Date: Mon, 13 Jan 2003 10:46:10 -0800 (PST) +From: Stephan Szabo +To: Josh Berkus +Cc: +Subject: Re: Accessing ANALYZE stats +In-Reply-To: <200301131042.01831.josh@agliodbs.com> +Message-ID: <20030113104527.J58199-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/76 +X-Sequence-Number: 723 + +On Mon, 13 Jan 2003, Josh Berkus wrote: + +> Can someone give me a quick pointer on where the ANALYZE stats are kept in +> 7.2.3? Thanks. + +Should be in pg_stats I believe. + + +From pgsql-performance-owner@postgresql.org Mon Jan 13 16:33:19 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D52D4476CD5 + for ; + Mon, 13 Jan 2003 16:33:16 -0500 (EST) +Received: from o2.hostbaby.com (o2.hostbaby.com [208.187.29.121]) + by postgresql.org (Postfix) with SMTP id 3165E476B4D + for ; + Mon, 13 Jan 2003 16:33:16 -0500 (EST) +Received: (qmail 32631 invoked from network); 13 Jan 2003 21:33:19 -0000 +Received: from unknown (HELO l-i-e.com) (127.0.0.1) + by localhost with SMTP; 13 Jan 2003 21:33:19 -0000 +Received: from 216.80.95.13 + (Hostbaby Webmail authenticated user typea@l-i-e.com) + by www.l-i-e.com with HTTP; Mon, 13 Jan 2003 13:33:19 -0800 (PST) +Message-ID: <49456.216.80.95.13.1042493599.squirrel@www.l-i-e.com> +Date: Mon, 13 Jan 2003 13:33:19 -0800 (PST) +Subject: Cursor rowcount +From: +To: +X-Priority: 3 +Importance: Normal +X-Mailer: Hostbaby Webmail +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/77 +X-Sequence-Number: 724 + +Short Version: + +I've read the idocs and Notes and Googled a fair amount, honest. :-) + +What's the most efficient way of determining the number of rows in a +cursor's result set if you really *DO* need that? (Or, rather, if your +client specifically asked for features that require that.) + + +Long Version: +I'm not finding any way in the docs of asking a cursor how many rows total +are in the result set, even if I do "move 1000000 in foo", knowing a +priori that 1000000 is far more than could be returned. + +Oracle docs seem to have a SQL.%ROWCOUNT which gives the answer, provided +one has moved beyond the last row... If I'm reading the Oracle docs +right... + +Anyway. I could find nothing similar in PostgreSQL, even though it seems +reasonable, even for a Portal, provided one is willing to do the "move X" +for X sufficiently high -- And, in fact, psql outputs the precise number +of rows when I do that in the psql monitor, so at some level PostgreSQL +"knows" the answer I want, but I can't get that "MOVE XX" output into PHP, +as far as I can tell. (Can I?) + +I suppose I could, in theory, use PHP to fire up psql, but that's not +exactly going to be efficient, much less pleasant. :-) + +Using PHP, if it matters. I guess it does since maybe other APIs have +some way to access that number I want -- psql sure seems to print it out +when one goes over the edge. + +Given that the count(*) queries take just as long as the actual +data-retrieval queries, and that some of my queries take too long as it is +(like, a minute for a 4-term full text search)... + +I've written and am about to benchmark a binary search using a bunch of +"move X" "fetch 1" "move backward 1" "move backward X" and then using Ye +Olde Low/High guessing game algorithm to find the number of rows, but I'm +hoping for something better from the optimization experts. + +Sorry this got a bit long, but I wanted to be clear about where I've been +and gone, rather than leave you guessing. :-) + +Hope I didn't miss some obvious solution/documentation "out there"... + + + + +From pgsql-performance-owner@postgresql.org Mon Jan 13 17:23:19 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id AC8DA477192 + for ; + Mon, 13 Jan 2003 17:23:18 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 07E764770D4 + for ; + Mon, 13 Jan 2003 17:22:10 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0DMMA5u006430; + Mon, 13 Jan 2003 17:22:10 -0500 (EST) +To: typea@l-i-e.com +Cc: pgsql-performance@postgresql.org +Subject: Re: Cursor rowcount +In-reply-to: <49456.216.80.95.13.1042493599.squirrel@www.l-i-e.com> +References: <49456.216.80.95.13.1042493599.squirrel@www.l-i-e.com> +Comments: In-reply-to + message dated "Mon, 13 Jan 2003 13:33:19 -0800" +Date: Mon, 13 Jan 2003 17:22:10 -0500 +Message-ID: <6429.1042496530@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/78 +X-Sequence-Number: 725 + + writes: +> I'm not finding any way in the docs of asking a cursor how many rows total +> are in the result set, even if I do "move 1000000 in foo", knowing a +> priori that 1000000 is far more than could be returned. + +regression=# begin; +BEGIN +regression=# declare c cursor for select * from int8_tbl; +DECLARE CURSOR +regression=# move all in c; +MOVE 5 <----------------------- +regression=# end; +COMMIT + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Jan 14 17:30:53 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6EF86475D22 + for ; + Tue, 14 Jan 2003 17:30:52 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id CFE7E475B8F + for ; + Tue, 14 Jan 2003 17:30:51 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2313944; Tue, 14 Jan 2003 14:30:50 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Noah Silverman , Rod Taylor +Subject: Re: Multiple databases +Date: Mon, 13 Jan 2003 14:32:47 -0800 +X-Mailer: KMail [version 1.4] +Cc: Pgsql Performance +References: +In-Reply-To: +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301131432.47468.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/112 +X-Sequence-Number: 759 + + +Noah, + +> Can someone give me a good description of what the various directories=20 +> and files actually are. I have RTFMed, but the descriptions there=20 +> don't seem to match what I have on my machine. + +Within $PGDATA: + +/base is all database files unless you use WITH LOCATION +/pg_clog is the Clog, which keeps a permanent count of transactions +/pg_xlog is the transaction log (WAL) +/global are a small number of relations, like pg_database or pg_user, which= +=20 +are available in all databases. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Mon Jan 13 20:05:45 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D89D2475E9D + for ; + Mon, 13 Jan 2003 20:05:44 -0500 (EST) +Received: from o2.hostbaby.com (o2.hostbaby.com [208.187.29.121]) + by postgresql.org (Postfix) with SMTP id 0C11D475D3B + for ; + Mon, 13 Jan 2003 20:05:44 -0500 (EST) +Received: (qmail 23419 invoked from network); 14 Jan 2003 01:05:50 -0000 +Received: from unknown (HELO l-i-e.com) (127.0.0.1) + by localhost with SMTP; 14 Jan 2003 01:05:50 -0000 +Received: from 216.80.95.13 + (Hostbaby Webmail authenticated user typea@l-i-e.com) + by www.l-i-e.com with HTTP; Mon, 13 Jan 2003 17:05:50 -0800 (PST) +Message-ID: <50156.216.80.95.13.1042506350.squirrel@www.l-i-e.com> +Date: Mon, 13 Jan 2003 17:05:50 -0800 (PST) +Subject: Re: Cursor rowcount +From: +To: +In-Reply-To: <6429.1042496530@sss.pgh.pa.us> +References: <49456.216.80.95.13.1042493599.squirrel@www.l-i-e.com> + <6429.1042496530@sss.pgh.pa.us> +X-Priority: 3 +Importance: Normal +X-Mailer: Hostbaby Webmail +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/79 +X-Sequence-Number: 726 + +> writes: +>> I'm not finding any way in the docs of asking a cursor how many rows +>> total are in the result set, even if I do "move 1000000 in foo", +>> knowing a priori that 1000000 is far more than could be returned. +> +> regression=# begin; +> BEGIN +> regression=# declare c cursor for select * from int8_tbl; +> DECLARE CURSOR +> regression=# move all in c; +> MOVE 5 <----------------------- +> regression=# end; +> COMMIT +> +> regards, tom lane + +Yes, but as noted in my longer version, that number does not seem to "come +through" the PHP API. + +I've tried calling just about every function I can in the PHP API in a +test script, and none of them give me that number. + +At least, none that I can find... + + + + +From pgsql-performance-owner@postgresql.org Mon Jan 13 23:20:57 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9726E4771E3 + for ; + Mon, 13 Jan 2003 23:20:56 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 2CFCF47722D + for ; + Mon, 13 Jan 2003 23:19:37 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0E4Je5u012896; + Mon, 13 Jan 2003 23:19:41 -0500 (EST) +To: typea@l-i-e.com +Cc: pgsql-performance@postgresql.org +Subject: Re: Cursor rowcount +In-reply-to: <50156.216.80.95.13.1042506350.squirrel@www.l-i-e.com> +References: <49456.216.80.95.13.1042493599.squirrel@www.l-i-e.com> + <6429.1042496530@sss.pgh.pa.us> + <50156.216.80.95.13.1042506350.squirrel@www.l-i-e.com> +Comments: In-reply-to + message dated "Mon, 13 Jan 2003 17:05:50 -0800" +Date: Mon, 13 Jan 2003 23:19:40 -0500 +Message-ID: <12895.1042517980@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/80 +X-Sequence-Number: 727 + + writes: +> Yes, but as noted in my longer version, that number does not seem to "come +> through" the PHP API. + +Perhaps not, but you'd have to ask the PHP folk about it. This question +surely doesn't belong on pgsql-performance ... + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Jan 14 04:12:38 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C54B5475AE6 + for ; + Tue, 14 Jan 2003 04:12:36 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 0E65947580B + for ; + Tue, 14 Jan 2003 04:12:36 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030114091237.MGAF26808.lakemtao03.cox.net@[192.168.1.1]> + for ; + Tue, 14 Jan 2003 04:12:37 -0500 +Subject: Re: Cursor rowcount +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <12895.1042517980@sss.pgh.pa.us> +References: <49456.216.80.95.13.1042493599.squirrel@www.l-i-e.com> + <6429.1042496530@sss.pgh.pa.us> + <50156.216.80.95.13.1042506350.squirrel@www.l-i-e.com> + <12895.1042517980@sss.pgh.pa.us> +Content-Type: text/plain +Organization: +Message-Id: <1042535548.27702.31.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 14 Jan 2003 03:12:28 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/81 +X-Sequence-Number: 728 + +On Mon, 2003-01-13 at 22:19, Tom Lane wrote: +> writes: +> > Yes, but as noted in my longer version, that number does not seem to "come +> > through" the PHP API. +> +> Perhaps not, but you'd have to ask the PHP folk about it. This question +> surely doesn't belong on pgsql-performance ... + +Wellllll, maybe it does, since the /performance/ of a SELECT COUNT(*) +followed by a cursor certainly is lower than getting the count from +a system variable. + +But still I agree, the PHP list seems more appropriate... + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 05:50:55 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 30F6C475EE2 + for ; + Tue, 14 Jan 2003 05:50:54 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 625A6475DBC + for ; + Tue, 14 Jan 2003 05:50:53 -0500 (EST) +Received: from klaster.net (pc43.krakow.cvx.ppp.tpnet.pl [213.76.38.43]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP id 3A0062B267 + for ; + Tue, 14 Jan 2003 11:48:02 +0100 (CET) +Message-ID: <3E23EC83.9060802@klaster.net> +Date: Tue, 14 Jan 2003 11:54:59 +0100 +From: Tomasz Myrta +User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; + rv:1.2b) Gecko/20021016 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: PgSQL Performance ML +Subject: complicated queries in pl/pgsql +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/82 +X-Sequence-Number: 729 + +Hi +Sometimes my pl/pgsql functions have pretty complicated queries inside - + most of their execution time takes postgresql query planning. +I was wondering if I should change these queries into views? Does it +speed up function execution? Pl/pgsql saves execution plan for +connection lifetime. What happens to view planning - is it performed +during view creation, or rather each time view is quered? + +Regards, +Tomasz Myrta + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 10:00:07 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8035C47618A + for ; + Tue, 14 Jan 2003 10:00:05 -0500 (EST) +Received: from web21103.mail.yahoo.com (web21103.mail.yahoo.com + [216.136.227.105]) + by postgresql.org (Postfix) with SMTP id C80EC4760D4 + for ; + Tue, 14 Jan 2003 10:00:04 -0500 (EST) +Message-ID: <20030114150008.49425.qmail@web21103.mail.yahoo.com> +Received: from [131.142.161.245] by web21103.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 07:00:08 PST +Date: Tue, 14 Jan 2003 07:00:08 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Sun vs. Mac +To: pgsql-performance@postgresql.org +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/83 +X-Sequence-Number: 730 + +Hello, + +I'm having some serious performance issues with PostgreSQL on +our newish SunFire 280R (1 900MHz ultrasparc III, 1 GB RAM). +It's painfully slow. It took me almost a week of tuning to get +it in the range of an old Mac G3 laptop. Now, a few days later, +after tweaking every nearly every parameter (only noting +decreased performance on some) in /etc/system and +$PGDATA/postgresql.conf it's about as fast as I can make it, but +still horribly slow. A few simple queries that take 1.5-7 +minutes on the G3 take 1-1.5 minutes on the Sun. A bulk load of +roughly 2.4 GB database dump takes ~1 hour on each machine. It +took almost 2 hours on the Sun before I turned off fsync. + +We have plans to add another CPU, RAM and another disk, which +should all help, but in its current state, I (and many others) +would think that it should run circles around the G3. I'm +thinking that I'm missing something big and obvious because this +can't be right. Otherwise we might as well just get a bunch of +ibooks to run our databases - they're a lot smaller and much +more quiet. + +Can someone please point me in the right direction? + +Thanks, + +-X + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 10:06:19 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BC1DF475E64 + for ; + Tue, 14 Jan 2003 10:06:17 -0500 (EST) +Received: from new-smtp2.ihug.com.au (new-smtp2.ihug.com.au [203.109.250.28]) + by postgresql.org (Postfix) with ESMTP id 1D69447580B + for ; + Tue, 14 Jan 2003 10:06:17 -0500 (EST) +Received: from p96-tnt1.adl.ihug.com.au (postgresql.org) [203.173.248.96] + by new-smtp2.ihug.com.au with esmtp (Exim 3.22 #1 (Debian)) + id 18YSdv-0002Ef-00; Wed, 15 Jan 2003 02:06:20 +1100 +Message-ID: <3E242826.8020306@postgresql.org> +Date: Wed, 15 Jan 2003 01:39:26 +1030 +From: Justin Clift +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: captainx0r@yahoo.com +Cc: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac +References: <20030114150008.49425.qmail@web21103.mail.yahoo.com> +In-Reply-To: <20030114150008.49425.qmail@web21103.mail.yahoo.com> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/84 +X-Sequence-Number: 731 + +Hi CaptainXOr, + +Which version of PostgreSQL, and which release of Solaris are you running? + +Regards and best wishes, + +Justin Clift + + +CaptainX0r wrote: +> Hello, +> +> I'm having some serious performance issues with PostgreSQL on +> our newish SunFire 280R (1 900MHz ultrasparc III, 1 GB RAM). +> It's painfully slow. It took me almost a week of tuning to get +> it in the range of an old Mac G3 laptop. Now, a few days later, +> after tweaking every nearly every parameter (only noting +> decreased performance on some) in /etc/system and +> $PGDATA/postgresql.conf it's about as fast as I can make it, but +> still horribly slow. A few simple queries that take 1.5-7 +> minutes on the G3 take 1-1.5 minutes on the Sun. A bulk load of +> roughly 2.4 GB database dump takes ~1 hour on each machine. It +> took almost 2 hours on the Sun before I turned off fsync. +> +> We have plans to add another CPU, RAM and another disk, which +> should all help, but in its current state, I (and many others) +> would think that it should run circles around the G3. I'm +> thinking that I'm missing something big and obvious because this +> can't be right. Otherwise we might as well just get a bunch of +> ibooks to run our databases - they're a lot smaller and much +> more quiet. +> +> Can someone please point me in the right direction? +> +> Thanks, +> +> -X +> +> __________________________________________________ +> Do you Yahoo!? +> Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +> http://mailplus.yahoo.com +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org + + +-- +"My grandfather once told me that there are two kinds of people: those +who work and those who take the credit. He told me to try to be in the +first group; there was less competition there." +- Indira Gandhi + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 10:18:57 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 40EA4476212 + for ; + Tue, 14 Jan 2003 10:18:55 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id AB8B547721B + for ; + Tue, 14 Jan 2003 10:10:50 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18YSiM-0002Kv-00 + for ; Tue, 14 Jan 2003 10:10:54 -0500 +Date: Tue, 14 Jan 2003 10:10:54 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac +Message-ID: <20030114101054.B5335@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <20030114150008.49425.qmail@web21103.mail.yahoo.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <20030114150008.49425.qmail@web21103.mail.yahoo.com>; + from captainx0r@yahoo.com on Tue, Jan 14, 2003 at 07:00:08AM -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/85 +X-Sequence-Number: 732 + +On Tue, Jan 14, 2003 at 07:00:08AM -0800, CaptainX0r wrote: +> Hello, +> +> I'm having some serious performance issues with PostgreSQL on +> our newish SunFire 280R (1 900MHz ultrasparc III, 1 GB RAM). +> It's painfully slow. It took me almost a week of tuning to get +> it in the range of an old Mac G3 laptop. Now, a few days later, +> after tweaking every nearly every parameter (only noting +> decreased performance on some) in /etc/system and +> $PGDATA/postgresql.conf it's about as fast as I can make it, but + +You should tell us about what version of Solaris you're running, what +version of Postgres, and what options you have used. Did you split +the WAL onto its own filesystem? You'll get a big win that way. +Also, what fsync setting are you using (open_datasync is the fastest +in my experience). Finally, the bottleneck on Solaris is both disk +and process forking (fork() is notoriously slow on Solaris). + +Also, certain sort routines are abysmal. Replace the +Solaris-provided qsort(). + +I have to say, however, that my experience indicates that Solaris is +slower that the competition for Postgres. It still shouldn't be that +bad. + +A +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 10:43:44 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 016F74760CC + for ; + Tue, 14 Jan 2003 10:43:43 -0500 (EST) +Received: from web21106.mail.yahoo.com (web21106.mail.yahoo.com + [216.136.227.108]) + by postgresql.org (Postfix) with SMTP id 2C1D4475FEC + for ; + Tue, 14 Jan 2003 10:18:19 -0500 (EST) +Message-ID: <20030114151823.75801.qmail@web21106.mail.yahoo.com> +Received: from [131.142.161.245] by web21106.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 07:18:23 PST +Date: Tue, 14 Jan 2003 07:18:23 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac +To: pgsql-performance@postgresql.org +In-Reply-To: <3E242826.8020306@postgresql.org> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/86 +X-Sequence-Number: 733 + +Sorry - I meant to include that. I'm running PG 7.3.1 on +Solaris 8. + +Thanks, + +-X + +--- Justin Clift wrote: +> +> Which version of PostgreSQL, and which release of Solaris are +> you running? +> +> > +> > I'm having some serious performance issues with PostgreSQL +> on +> > our newish SunFire 280R (1 900MHz ultrasparc III, 1 GB RAM). +> +> > It's painfully slow. It took me almost a week of tuning to +> get +> > it in the range of an old Mac G3 laptop. Now, a few days +> later, +> > after tweaking every nearly every parameter (only noting +> > decreased performance on some) in /etc/system and +> > $PGDATA/postgresql.conf it's about as fast as I can make it, +> but +> > still horribly slow. A few simple queries that take 1.5-7 +> > minutes on the G3 take 1-1.5 minutes on the Sun. A bulk +> load of +> > roughly 2.4 GB database dump takes ~1 hour on each machine. +> It +> > took almost 2 hours on the Sun before I turned off fsync. +> > +> > We have plans to add another CPU, RAM and another disk, +> which +> > should all help, but in its current state, I (and many +> others) +> > would think that it should run circles around the G3. I'm +> > thinking that I'm missing something big and obvious because +> this +> > can't be right. Otherwise we might as well just get a bunch +> of +> > ibooks to run our databases - they're a lot smaller and much +> > more quiet. +> > +> > Can someone please point me in the right direction? +> > +> > Thanks, +> > +> > -X +> > + + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 10:47:03 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A88A94761B5 + for ; + Tue, 14 Jan 2003 10:47:02 -0500 (EST) +Received: from web21103.mail.yahoo.com (web21103.mail.yahoo.com + [216.136.227.105]) + by postgresql.org (Postfix) with SMTP id 873C8475ADD + for ; + Tue, 14 Jan 2003 10:41:17 -0500 (EST) +Message-ID: <20030114154121.53714.qmail@web21103.mail.yahoo.com> +Received: from [131.142.161.245] by web21103.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 07:41:21 PST +Date: Tue, 14 Jan 2003 07:41:21 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac +To: pgsql-performance@postgresql.org +In-Reply-To: <20030114101054.B5335@mail.libertyrms.com> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/87 +X-Sequence-Number: 734 + +All, + +> You should tell us about what version of Solaris you're +> running, what +> version of Postgres, and what options you have used. + +You're right, sorry. PG 7.3.1 on Solaris 8. I've got the +default recommended /etc/system but with shmmax cranked way up +which seems to have helped. I don't have the system in front of +me (and it's down, so I can't get to it), but from memory +max_connections was increased to 64, shared_buffers up to 65536, +sort_mem and vacuum_mem were doubled, and I think that's it. I +changed every seemingly relevant one, and spent a lot of time on +the *cost section trying various factors of n*10 on each, with +no joy. + +> Did you split +> the WAL onto its own filesystem? You'll get a big win that +> way. + +I have not. What exactly do you by "own filesystem"? Another +filesystem? I was planning on putting pg_xlog on the OS disk +and moving $PGDATA off to a second disk. + +> Also, what fsync setting are you using (open_datasync is the +> fastest in my experience). + +I've read that somewhere (maybe in the archives?) and I got no +change with any of them. But now I'm thinking back - do I need +fsync=true for that to have an affect? I'm not worried about +the cons of having fsync=false at all - and I'm assuming that +should be better than true and open_datasync. Or am I confusing +things? + +> Also, certain sort routines are abysmal. Replace the +> Solaris-provided qsort(). + +I've read about this as well - but haven't even gotten that far +on the testing/configuring yet. + +> I have to say, however, that my experience indicates that +> Solaris is +> slower that the competition for Postgres. It still shouldn't +> be that bad. + +I agree completely. + +Thanks for your input, + +-X + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 11:09:32 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 29306476435 + for ; + Tue, 14 Jan 2003 11:09:31 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 6B25F4762EE + for ; + Tue, 14 Jan 2003 11:04:48 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0EG4r5u016238; + Tue, 14 Jan 2003 11:04:53 -0500 (EST) +To: captainx0r@yahoo.com +Cc: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac +In-reply-to: <20030114154121.53714.qmail@web21103.mail.yahoo.com> +References: <20030114154121.53714.qmail@web21103.mail.yahoo.com> +Comments: In-reply-to CaptainX0r + message dated "Tue, 14 Jan 2003 07:41:21 -0800" +Date: Tue, 14 Jan 2003 11:04:52 -0500 +Message-ID: <16237.1042560292@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/88 +X-Sequence-Number: 735 + +CaptainX0r writes: +> I've read that somewhere (maybe in the archives?) and I got no +> change with any of them. But now I'm thinking back - do I need +> fsync=true for that to have an affect? I'm not worried about +> the cons of having fsync=false at all - and I'm assuming that +> should be better than true and open_datasync. + +You are right that fsync_method is a no-op if you've got fsync turned +off. + +Let me get this straight: the Sun is slower even with fsync off? That +shoots down the first theory that I had, which was that the Sun's disk +drives were actually honoring fsync while the laptop's drive does not. +(See archives for more discussion of that, but briefly: IDE drives are +commonly set up to claim write complete as soon as they've absorbed +data into their onboard buffers. SCSI drives usually tell the truth +about when they've completed a write.) + +Andrew Sullivan's nearby recommendation to replace qsort() is a good +one, but PG 7.3 is already configured to do that by default. (Look in +src/Makefile.global to confirm that qsort.o is mentioned in LIBOBJS.) + +I'd suggest starting with some elementary measurements, for example +looking at I/O rates and CPU idle percentage while running the same +task on both Solaris and G3. That would at least give us a clue whether +I/O or CPU is the bottleneck. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Jan 14 11:11:12 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B086A4767D9 + for ; + Tue, 14 Jan 2003 11:11:11 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 4761F47608D + for ; + Tue, 14 Jan 2003 11:08:47 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18YTcS-0003QL-00 + for ; Tue, 14 Jan 2003 11:08:52 -0500 +Date: Tue, 14 Jan 2003 11:08:52 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac +Message-ID: <20030114110852.E5335@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <20030114101054.B5335@mail.libertyrms.com> + <20030114154121.53714.qmail@web21103.mail.yahoo.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <20030114154121.53714.qmail@web21103.mail.yahoo.com>; + from captainx0r@yahoo.com on Tue, Jan 14, 2003 at 07:41:21AM -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/89 +X-Sequence-Number: 736 + +On Tue, Jan 14, 2003 at 07:41:21AM -0800, CaptainX0r wrote: +> +> You're right, sorry. PG 7.3.1 on Solaris 8. I've got the +> default recommended /etc/system but with shmmax cranked way up + +Ok, I have no experience with 7.3.1 in a production setting - we're +using 7.2. But here are some things. + +> which seems to have helped. I don't have the system in front of +> me (and it's down, so I can't get to it), but from memory +> max_connections was increased to 64, shared_buffers up to 65536, +> sort_mem and vacuum_mem were doubled, and I think that's it. I +> changed every seemingly relevant one, and spent a lot of time on + +You'll need to increase the number of available semaphores more than +likely, if you add any connections. You do indeed need to fix +shmmax, but if the postmaster starts, you're fine. + +I would worry slightly about sort_mem. I have managed to make +Solaris boxes with _lots_ of memory start swapping by setting that +too high (while experimenting). Look for problems in your I/O. + +> the *cost section trying various factors of n*10 on each, with +> no joy. + +These are fine-tuning knobs. You have a different problem :) + +> > Did you split +> > the WAL onto its own filesystem? You'll get a big win that +> > way. +> +> I have not. What exactly do you by "own filesystem"? Another +> filesystem? I was planning on putting pg_xlog on the OS disk +> and moving $PGDATA off to a second disk. + +That's what you need. Without any doubt at all. The xlog on the +same UFS filesystem (and disk) as the rest of $PGDATA is a nightmare. + +Interestingly, by the way, there is practically _no difference_ if +you do this with an A5200 managed by Veritas. I have tried dozens of +things. It never matters. The array is too fast. + +> > Also, what fsync setting are you using (open_datasync is the +> > fastest in my experience). +> +> I've read that somewhere (maybe in the archives?) and I got no +> change with any of them. But now I'm thinking back - do I need +> fsync=true for that to have an affect? I'm not worried about +> the cons of having fsync=false at all - and I'm assuming that +> should be better than true and open_datasync. Or am I confusing +> things? + +Yes, if you change the fsync method but have fsync turned off, it +will make no difference. + +> > Also, certain sort routines are abysmal. Replace the +> > Solaris-provided qsort(). +> +> I've read about this as well - but haven't even gotten that far +> on the testing/configuring yet. + +If you're doing any sorting that is not by an index, forget about it. +Change it now. It's something like a multiple of 40 slower. + +A +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 11:20:29 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 726424760E2 + for ; + Tue, 14 Jan 2003 11:20:27 -0500 (EST) +Received: from internet.csl.co.uk (internet.csl.co.uk [194.130.52.3]) + by postgresql.org (Postfix) with ESMTP id 4DF084762C4 + for ; + Tue, 14 Jan 2003 11:18:56 -0500 (EST) +Received: from euphrates.csl.co.uk (host-194-67.csl.co.uk [194.130.52.67]) + by internet.csl.co.uk (8.12.6/8.12.6) with ESMTP id h0EGIvMi002242; + Tue, 14 Jan 2003 16:18:57 GMT +Received: from kelvin.csl.co.uk by euphrates.csl.co.uk (8.9.3/ConceptI 2.4) + id QAA22033; Tue, 14 Jan 2003 16:18:59 GMT +Received: by kelvin.csl.co.uk (8.11.6) id h0EGIvu04353; + Tue, 14 Jan 2003 16:18:57 GMT +From: Lee Kindness +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Message-ID: <15908.14449.469992.977688@kelvin.csl.co.uk> +Date: Tue, 14 Jan 2003 16:18:57 +0000 +To: captainx0r@yahoo.com +Cc: pgsql-performance@postgresql.org, + Lee Kindness +Subject: Sun vs. Mac +In-Reply-To: <20030114150008.49425.qmail@web21103.mail.yahoo.com> +References: <20030114150008.49425.qmail@web21103.mail.yahoo.com> +X-Mailer: VM 7.00 under 21.4 (patch 6) "Common Lisp" XEmacs Lucid +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/90 +X-Sequence-Number: 737 + +CaptainX0r writes: + > I'm having some serious performance issues with PostgreSQL on + > our newish SunFire 280R (1 900MHz ultrasparc III, 1 GB RAM). + > It's painfully slow. + +What has PostgreSQL been compiled by? Personal past experience has +shown the Sun Workshop C compiler to result in much better performance +compared to GCC... + +L. + +From pgsql-performance-owner@postgresql.org Tue Jan 14 11:31:34 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id DD85947640E + for ; + Tue, 14 Jan 2003 11:31:31 -0500 (EST) +Received: from web21106.mail.yahoo.com (web21106.mail.yahoo.com + [216.136.227.108]) + by postgresql.org (Postfix) with SMTP id D708B47637C + for ; + Tue, 14 Jan 2003 11:29:52 -0500 (EST) +Message-ID: <20030114162957.93069.qmail@web21106.mail.yahoo.com> +Received: from [131.142.161.245] by web21106.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 08:29:57 PST +Date: Tue, 14 Jan 2003 08:29:57 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac +To: pgsql-performance@postgresql.org +In-Reply-To: <15908.14449.469992.977688@kelvin.csl.co.uk> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/91 +X-Sequence-Number: 738 + + +--- Lee Kindness wrote: +> CaptainX0r writes: +>> I'm having some serious performance issues with PostgreSQL on +>> our newish SunFire 280R (1 900MHz ultrasparc III, 1 GB RAM). +>> It's painfully slow. +> +> What has PostgreSQL been compiled by? Personal past experience +> has +> shown the Sun Workshop C compiler to result in much better +> performance +> compared to GCC... + +I used gcc - mostly because I have in the past, but also because +I've read that it is "the one to use". Am I wrong on this one? +I'm certainly willing to try the one from Sun Workshop. + +Thanks for the input, + +-X + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 11:40:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7A8BD476B6F + for ; + Tue, 14 Jan 2003 11:40:53 -0500 (EST) +Received: from web21107.mail.yahoo.com (web21107.mail.yahoo.com + [216.136.227.109]) + by postgresql.org (Postfix) with SMTP id 6B27347608D + for ; + Tue, 14 Jan 2003 11:38:20 -0500 (EST) +Message-ID: <20030114163825.45392.qmail@web21107.mail.yahoo.com> +Received: from [131.142.161.245] by web21107.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 08:38:25 PST +Date: Tue, 14 Jan 2003 08:38:25 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac +To: pgsql-performance@postgresql.org +In-Reply-To: <20030114110852.E5335@mail.libertyrms.com> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/92 +X-Sequence-Number: 739 + +> You'll need to increase the number of available semaphores +> more than +> likely, if you add any connections. You do indeed need to fix +> shmmax, but if the postmaster starts, you're fine. + +Thanks, I'll take a closer look at this. + +> That's what you need. Without any doubt at all. The xlog on +> the same UFS filesystem (and disk) as the rest of $PGDATA is a +> nightmare. + +The disks are on order - but that can't be the only thing hold +it up, can it? I've got to check out the IO, as you suggest. + +> > > Also, certain sort routines are abysmal. Replace the +> > > Solaris-provided qsort(). +> > +> > I've read about this as well - but haven't even gotten that +> > far on the testing/configuring yet. +> +> If you're doing any sorting that is not by an index, forget +> about it. +> Change it now. It's something like a multiple of 40 slower. + +I double checked, and this was one of the reasons I was glad to +try 7.3 on Solaris - it's already got it built in. + +Thanks much for the input, + +-X + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 11:58:51 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C47214764E6 + for ; + Tue, 14 Jan 2003 11:58:50 -0500 (EST) +Received: from web21110.mail.yahoo.com (web21110.mail.yahoo.com + [216.136.227.112]) + by postgresql.org (Postfix) with SMTP id 3984D47656B + for ; + Tue, 14 Jan 2003 11:54:28 -0500 (EST) +Message-ID: <20030114165433.63951.qmail@web21110.mail.yahoo.com> +Received: from [131.142.161.245] by web21110.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 08:54:33 PST +Date: Tue, 14 Jan 2003 08:54:33 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac +To: pgsql-performance@postgresql.org +In-Reply-To: <16237.1042560292@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/93 +X-Sequence-Number: 740 + +All, + +> Let me get this straight: the Sun is slower even with fsync +> off? That + +Correct. This really helped a lot, especially with the dump +load, but I've clearly got some more work ahead of me. + +> Andrew Sullivan's nearby recommendation to replace qsort() is +> a good +> one, but PG 7.3 is already configured to do that by default. +> (Look in +> src/Makefile.global to confirm that qsort.o is mentioned in +> LIBOBJS.) + +Thanks for confirming. I've got LIBOBJS = isinf.o qsort.o + +> I'd suggest starting with some elementary measurements, for +> example looking at I/O rates and CPU idle percentage while +> running the same task on both Solaris and G3. That would at +> least give us a clue whether I/O or CPU is the bottleneck. + +Good thoughts - I'm working on it right now, though I'm not +really sure how to check I/O rates.... + +Thanks much for the input, + +-X + + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 12:51:01 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6A5614767C1 + for ; + Tue, 14 Jan 2003 12:51:00 -0500 (EST) +Received: from web21101.mail.yahoo.com (web21101.mail.yahoo.com + [216.136.227.103]) + by postgresql.org (Postfix) with SMTP id 4B8D84765D2 + for ; + Tue, 14 Jan 2003 12:49:59 -0500 (EST) +Message-ID: <20030114175004.15074.qmail@web21101.mail.yahoo.com> +Received: from [131.142.161.245] by web21101.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 09:50:04 PST +Date: Tue, 14 Jan 2003 09:50:04 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac +To: pgsql-performance@postgresql.org +In-Reply-To: <16237.1042560292@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/95 +X-Sequence-Number: 742 + +> I'd suggest starting with some elementary measurements, for +> example looking at I/O rates and CPU idle percentage while +> running the same task on both Solaris and G3. That would at +> least give us a clue whether I/O or CPU is the bottleneck. + +Well, I've got the Sun box now, but I don't really have acces to +the G3. FWIW, top shows postgres slowly taking up all the CPU - +over the course of a minute or so it gradually ramps up to +around 90%. Once the query is complete, however, top shows the +CPU ramping down slowly, ~1-2% per second over the next 2 +minutes which I find very strange. The CPU idle is 0% for the +duration of the query, while the user state is around 100% for +the same period. This kind of makes me think top is wrong (100% +idle and 75% postgres?) + +iostat gives: (sorry for line wrap). + +# iostat -DcxnzP + cpu + us sy wt id + 10 1 4 85 + extended device statistics + r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b +device + 11.2 1.0 65.5 13.1 0.1 0.1 9.5 9.6 0 3 +c1t0d0s0 + 0.0 0.0 0.0 0.1 0.0 0.0 0.0 6.0 0 0 +c1t0d0s1 + 7.3 0.1 502.3 0.5 0.0 0.0 0.0 2.3 0 1 +c1t0d0s3 + 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0 0 +host:vold(pid313) + + +This doesn't really tell me much, except I'm guessing that PG is +CPU bound? + +-X + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 13:02:28 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CA79B4761AD + for ; + Tue, 14 Jan 2003 13:02:27 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 85FF4476B78 + for ; + Tue, 14 Jan 2003 12:58:42 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18YVKq-0005oX-00 + for ; Tue, 14 Jan 2003 12:58:48 -0500 +Date: Tue, 14 Jan 2003 12:58:48 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac +Message-ID: <20030114125848.P5335@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <16237.1042560292@sss.pgh.pa.us> + <20030114175004.15074.qmail@web21101.mail.yahoo.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <20030114175004.15074.qmail@web21101.mail.yahoo.com>; + from captainx0r@yahoo.com on Tue, Jan 14, 2003 at 09:50:04AM -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/96 +X-Sequence-Number: 743 + +On Tue, Jan 14, 2003 at 09:50:04AM -0800, CaptainX0r wrote: +> the G3. FWIW, top shows postgres slowly taking up all the CPU - + +Son't use top on Solaris 8. It's inaccurate, and it affects the +results itself. Use prstat instead. + +> This doesn't really tell me much, except I'm guessing that PG is +> CPU bound? + +It looks that way. I've had iostat show CPU-bound, however, when the +problem actually turned out to be memory contention. I think you may +want to have a poke with vmstat, and also have a look at the SE +toolkit. + +A + +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 13:11:34 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 01D90476920 + for ; + Tue, 14 Jan 2003 13:11:33 -0500 (EST) +Received: from web21109.mail.yahoo.com (web21109.mail.yahoo.com + [216.136.227.111]) + by postgresql.org (Postfix) with SMTP id 4A7DA4760AB + for ; + Tue, 14 Jan 2003 13:10:55 -0500 (EST) +Message-ID: <20030114181054.25701.qmail@web21109.mail.yahoo.com> +Received: from [131.142.161.245] by web21109.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 10:10:54 PST +Date: Tue, 14 Jan 2003 10:10:54 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac - best Postgres platform? +To: pgsql-performance@postgresql.org +In-Reply-To: <1042572384.15544.84.camel@huli> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/97 +X-Sequence-Number: 744 + +> could you post your $PGDATA/postgresql.conf for our viewing +> pleasure ? + +max_connections = 64 +shared_buffers = 65536 # 1/2 total RAM /8K +sort_mem = 100000 # min 64, size in KB +checkpoint_timeout = 300 # range 30-3600, in seconds +fsync = false +effective_cache_size = 65536 # typically 8KB each +log_timestamp = true +notice, warning, error +stats_command_string = true +stats_row_level = true +stats_block_level = true +LC_MESSAGES = 'C' +LC_MONETARY = 'C' +LC_NUMERIC = 'C' +LC_TIME = 'C' + +I've stripped out the default lines (grep -v ^#) comments and +blank lines. + +> Another CPU will probably not help with bulk loads or other +> single-user stuff. +> +[snip] +> +> For single-user tasks you will probably be better off by +> getting a gray box with Athlon 2600+ with 3 Gigs of memory and + +> IDE disks and running Linux or *BSD . + +Hannu brings up a good point - one that was debated before my +attempts at making Solaris faster. If you were going to make a +fast postgres server what would you use? Assuming you could +afford a SunFire 280R (~$8k?), would that money be better spent +on a (say) Dell server running (say) linux? We're doing light +multiuser (I guess effectively single user) but at some point +(years) this may grow considereably. I'm not particular to +Macs, but I've got to say, that stock out the box, postgres +loves it. That old G3 was faster than the Sun, and still is +faster than my (years newer) linux laptop (on which I've done no +performance tweaking). So maybe a dual G4 Xserver would scream? + +Any suggestions? It's still not too late for us to change our +minds on this one. + +Thanks much, + +-X + + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 13:17:40 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C5B5E475EE4 + for ; + Tue, 14 Jan 2003 13:17:37 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 3AA5147655A + for ; + Tue, 14 Jan 2003 13:15:55 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0EIFs5u017343; + Tue, 14 Jan 2003 13:15:54 -0500 (EST) +To: captainx0r@yahoo.com +Cc: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac +In-reply-to: <20030114175004.15074.qmail@web21101.mail.yahoo.com> +References: <20030114175004.15074.qmail@web21101.mail.yahoo.com> +Comments: In-reply-to CaptainX0r + message dated "Tue, 14 Jan 2003 09:50:04 -0800" +Date: Tue, 14 Jan 2003 13:15:54 -0500 +Message-ID: <17342.1042568154@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/98 +X-Sequence-Number: 745 + +CaptainX0r writes: +> Well, I've got the Sun box now, but I don't really have acces to +> the G3. FWIW, top shows postgres slowly taking up all the CPU - +> over the course of a minute or so it gradually ramps up to +> around 90%. Once the query is complete, however, top shows the +> CPU ramping down slowly, ~1-2% per second over the next 2 +> minutes which I find very strange. + +I believe top's percent-of-CPU numbers for individual processes are time +averages over a minute or so, so the ramping effect is unsurprising. + +> This doesn't really tell me much, except I'm guessing that PG is +> CPU bound? + +Yup, that seems pretty clear. Next step is to find out what the heck +it's doing. My instinct would be to use gprof. Recompile with +profiling enabled --- if you're using gcc, this should work + cd postgres-distribution/src/backend + make clean + make PROFILE=-pg all + make install-bin -- may need to stop postmaster before install +Next run some sample queries (put them all into one session). After +quitting the session, find gmon.out in the $PGDATA/base/nnn/ +subdirectory corresponding to your database, and feed it to gprof. +The results should show where the code hotspot is. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Jan 14 13:28:45 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6F6C547686C + for ; + Tue, 14 Jan 2003 13:28:44 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id 15D4B476383 + for ; + Tue, 14 Jan 2003 13:26:58 -0500 (EST) +Received: from css120.ihs.com (css120.ihs.com [170.207.105.120]) + by mail1.ihs.com (8.12.6/8.12.6) with ESMTP id h0EIOmW4002653; + Tue, 14 Jan 2003 11:24:48 -0700 (MST) +Date: Tue, 14 Jan 2003 11:26:09 -0700 (MST) +From: "scott.marlowe" +To: CaptainX0r +Cc: +Subject: Re: Sun vs. Mac +In-Reply-To: <20030114150008.49425.qmail@web21103.mail.yahoo.com> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-MailScanner: Found to be clean +X-MailScanner-SpamCheck: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/99 +X-Sequence-Number: 746 + +On Tue, 14 Jan 2003, CaptainX0r wrote: + +> Hello, +> +> I'm having some serious performance issues with PostgreSQL on +> our newish SunFire 280R (1 900MHz ultrasparc III, 1 GB RAM). +> It's painfully slow. It took me almost a week of tuning to get +> it in the range of an old Mac G3 laptop. Now, a few days later, +> after tweaking every nearly every parameter (only noting +> decreased performance on some) in /etc/system and +> $PGDATA/postgresql.conf it's about as fast as I can make it, but +> still horribly slow. A few simple queries that take 1.5-7 +> minutes on the G3 take 1-1.5 minutes on the Sun. A bulk load of +> roughly 2.4 GB database dump takes ~1 hour on each machine. It +> took almost 2 hours on the Sun before I turned off fsync. + +Just for giggles, do you have a spare drive or something you can try +loading debian or some other Sparc compatible linux distro and get some +numbers? My experience has been that on the same basic hardware, Linux +runs postgresql about twice as fast as Solaris, and no amount of tweaking +seemed to ever get postgresql up to the same performance on Solaris. It's +so bad a Sparc 20 with 256 Meg ram and a 50 MHz 32 bit CPU running linux +was outrunning our Sun Ultra 1 with 512 Meg ram and a 150 MHz 64 bit CPU +by about 50%. That was with the 2.0.x kernel for linux and Solaris 7 on +the Ultra I believe. Could have been older on the Solaris version, as I +wasn't the SA on that box. + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 13:29:27 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9B216475D64 + for ; + Tue, 14 Jan 2003 13:29:26 -0500 (EST) +Received: from web21110.mail.yahoo.com (web21110.mail.yahoo.com + [216.136.227.112]) + by postgresql.org (Postfix) with SMTP id 3F41B476A37 + for ; + Tue, 14 Jan 2003 13:27:36 -0500 (EST) +Message-ID: <20030114182736.85732.qmail@web21110.mail.yahoo.com> +Received: from [131.142.161.245] by web21110.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 10:27:36 PST +Date: Tue, 14 Jan 2003 10:27:36 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac +To: pgsql-performance@postgresql.org +In-Reply-To: <20030114125848.P5335@mail.libertyrms.com> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/100 +X-Sequence-Number: 747 + + +--- Andrew Sullivan wrote: +> On Tue, Jan 14, 2003 at 09:50:04AM -0800, CaptainX0r wrote: +> > the G3. FWIW, top shows postgres slowly taking up all the +> CPU - +> +> Son't use top on Solaris 8. It's inaccurate, and it affects +> the results itself. Use prstat instead. + +Thanks for the tip. Unfortunately it shows the same exact +thing. + +> > This doesn't really tell me much, except I'm guessing that +> PG is +> > CPU bound? +> +> It looks that way. I've had iostat show CPU-bound, however, +> when the problem actually turned out to be memory contention. + +> I think you may want to have a poke with vmstat, and also have + +> a look at the SE toolkit. + +I'll have a look at the SE toolkit - thanks. + +vmstat shows me this: +# vmstat -s + 0 swap ins + 0 swap outs + 0 pages swapped in + 0 pages swapped out + 125452 total address trans. faults taken + 35245 page ins + 60 page outs + 194353 pages paged in + 229 pages paged out + 184621 total reclaims + 184563 reclaims from free list + 0 micro (hat) faults + 125452 minor (as) faults + 31764 major faults + 10769 copy-on-write faults + 80220 zero fill page faults + 0 pages examined by the clock daemon + 0 revolutions of the clock hand + 170 pages freed by the clock daemon + 601 forks + 19 vforks + 577 execs + 370612 cpu context switches + 1288431 device interrupts + 148288 traps + 1222653 system calls + 294090 total name lookups (cache hits 48%) + 43510 user cpu + 4002 system cpu + 480912 idle cpu + 13805 wait cpu + + procs memory page disk +faults cpu + r b w swap free re mf pi po fr de sr s6 sd -- -- in sy + cs us sy id + 0 0 0 815496 538976 31 21 261 0 0 0 0 0 12 0 0 136 209 + 65 7 1 92 + +I've not much experience with this, it looks like there are +considerably more page ins than outs as compared to our other +solaris boxen but otherwise pretty normal. + +-X + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 13:32:04 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 58F04475F5A + for ; + Tue, 14 Jan 2003 13:32:03 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id F0E0F476E48 + for ; + Tue, 14 Jan 2003 13:30:46 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18YVpm-0006Vm-00 + for ; Tue, 14 Jan 2003 13:30:46 -0500 +Date: Tue, 14 Jan 2003 13:30:46 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac - best Postgres platform? +Message-ID: <20030114133046.T5335@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <1042572384.15544.84.camel@huli> + <20030114181054.25701.qmail@web21109.mail.yahoo.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <20030114181054.25701.qmail@web21109.mail.yahoo.com>; + from captainx0r@yahoo.com on Tue, Jan 14, 2003 at 10:10:54AM -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/101 +X-Sequence-Number: 748 + +On Tue, Jan 14, 2003 at 10:10:54AM -0800, CaptainX0r wrote: +> > could you post your $PGDATA/postgresql.conf for our viewing +> > pleasure ? +> +> max_connections = 64 +> shared_buffers = 65536 # 1/2 total RAM /8K +> sort_mem = 100000 # min 64, size in KB + ^^^^^^ +There's your problem. Don't set that anywhere near that high. +If you run 2 queries that require sorting, _each sort_ can use up to +100000 K. Which can chew up all your memory pretty fast. + +> effective_cache_size = 65536 # typically 8KB each + +What basis did you have to change this? Have you done work figuring +out how big the kernel's disk cache is regularly on that system? + +> Hannu brings up a good point - one that was debated before my +> attempts at making Solaris faster. If you were going to make a +> fast postgres server what would you use? Assuming you could +> afford a SunFire 280R (~$8k?), would that money be better spent +> on a (say) Dell server running (say) linux? We're doing light + +I've been finding FreeBSD way faster than Linux. But yes. + +A +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 13:39:14 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A785747612D + for ; + Tue, 14 Jan 2003 13:39:12 -0500 (EST) +Received: from l2.socialecology.com (unknown [4.42.179.131]) + by postgresql.org (Postfix) with ESMTP id 2B7EC4760AB + for ; + Tue, 14 Jan 2003 13:39:12 -0500 (EST) +Received: from 4.42.179.151 (broccoli.socialecology.com [4.42.179.151]) + by l2.socialecology.com (Postfix) with SMTP id E704D329D01 + for ; + Tue, 14 Jan 2003 09:56:08 -0800 (PST) +X-Mailer: UserLand Frontier 9.1b1 (Macintosh OS) (mailServer v1.1..142) +Mime-Version: 1.0 +Message-Id: <17122703.1169581751@[4.42.179.151]> +X-authenticated-sender: erics +In-reply-to: <20030114181054.25701.qmail@web21109.mail.yahoo.com> +Date: Tue, 14 Jan 2003 10:39:05 -0800 +To: pgsql-performance@postgresql.org +From: eric soroos +Subject: Re: Sun vs. Mac - best Postgres platform? +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/102 +X-Sequence-Number: 749 + + +> > For single-user tasks you will probably be better off by +> > getting a gray box with Athlon 2600+ with 3 Gigs of memory and +> +> > IDE disks and running Linux or *BSD . +> + +> I'm not particular to +> Macs, but I've got to say, that stock out the box, postgres +> loves it. That old G3 was faster than the Sun, and still is +> faster than my (years newer) linux laptop (on which I've done no +> performance tweaking). So maybe a dual G4 Xserver would scream? +> +> Any suggestions? It's still not too late for us to change our +> minds on this one. + +I can't recommend macs for either brute force speed or price/performance. + +My current flock of machines are mostly OSX g4 boxes (single 400s and dual 800), with a couple of linux boxen thrown in for good measure. + +The mac's biggest issues are: + +1) Tweakability - you've got one file system, and it doesn't really do useful mount options like noatime. +2) There are bugs in mount and traversing symlinks that make it hard to move pg_xlog onto another file system and retain performance (in 10.1.5, I don't have test hardware with enough drives to test 10.2) +3) vm_stat gives vm status, iostat gives nothing. Looks like this is working on my 10.2 laptop, but it's annoyed me for a while on 10.1.5 +4) SW raid is not that much of a help for speed. +5) Bus bandwidth is a good factor behind x86 linux boxen. (DDR ram isn't really taken advantage of in current designs) + +Having said that, I'm getting reasonable performance out of all the macs, in fact, I'm getting reasonably similar performance out of all of them desplite the 4x difference in processor power. And that's because they basically have the same low end disk system. + +I'm piecing together something that I hope will be faster out of a x86 box loaded with more drives in a sw raid mirroring setup. (tentative is 1x system+logs, mirror for pg_xlog, mirror for pg data) + +I'm planning on running some comparative benchmarks prior to going live, so I should be able to tell how much faster it is. + +eric + + + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 13:41:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 07B5D475F5A + for ; + Tue, 14 Jan 2003 13:41:07 -0500 (EST) +Received: from web21102.mail.yahoo.com (web21102.mail.yahoo.com + [216.136.227.104]) + by postgresql.org (Postfix) with SMTP id 5A07D475F25 + for ; + Tue, 14 Jan 2003 13:41:06 -0500 (EST) +Message-ID: <20030114184106.93556.qmail@web21102.mail.yahoo.com> +Received: from [131.142.161.245] by web21102.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 10:41:06 PST +Date: Tue, 14 Jan 2003 10:41:06 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac +To: pgsql-performance@postgresql.org +In-Reply-To: +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/103 +X-Sequence-Number: 750 + +Hi, + +> Just for giggles, do you have a spare drive or something you +> can try +> loading debian or some other Sparc compatible linux distro and +> get some +> numbers? My experience has been that on the same basic + +This was on the todo list, "just to see", but I'm not sure how +much time we want to spend trying a myriad of options when +concentrating on one should (maybe?) do the trick. + +> hardware, Linux runs postgresql about twice as fast as +> Solaris, and no amount of tweaking seemed to ever get +> postgresql up to the same performance on Solaris. It's +> so bad a Sparc 20 with 256 Meg ram and a 50 MHz 32 bit CPU +> running linux was outrunning our Sun Ultra 1 with 512 Meg ram + +> and a 150 MHz 64 bit CPU by about 50%. That was with the +> 2.0.x kernel for linux and + +This is not encouraging..... We may be revisiting the linux +option. + +Thanks much for the input, + +-X + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 14:01:51 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C8CE0475D22 + for ; + Tue, 14 Jan 2003 14:01:49 -0500 (EST) +Received: from web21104.mail.yahoo.com (web21104.mail.yahoo.com + [216.136.227.106]) + by postgresql.org (Postfix) with SMTP id 2AB1C475BA1 + for ; + Tue, 14 Jan 2003 14:01:49 -0500 (EST) +Message-ID: <20030114190149.7293.qmail@web21104.mail.yahoo.com> +Received: from [131.142.161.245] by web21104.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 11:01:49 PST +Date: Tue, 14 Jan 2003 11:01:49 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac - best Postgres platform? +To: pgsql-performance@postgresql.org +In-Reply-To: <20030114133046.T5335@mail.libertyrms.com> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/105 +X-Sequence-Number: 752 + + +--- Andrew Sullivan wrote: +> On Tue, Jan 14, 2003 at 10:10:54AM -0800, CaptainX0r wrote: +> > > could you post your $PGDATA/postgresql.conf for our +> viewing +> > > pleasure ? +> > +> > max_connections = 64 +> > shared_buffers = 65536 # 1/2 total RAM /8K +> > sort_mem = 100000 # min 64, size in KB +> ^^^^^^ +> There's your problem. Don't set that anywhere near that high. +> If you run 2 queries that require sorting, _each sort_ can use +> up to +> 100000 K. Which can chew up all your memory pretty fast. + +I changed back to the default 1024, and down to the minimum, 64 +- no change. I think that was changed simultaneously with some +other parameter (bad, I know) that actually had an affect. I +guess I can remove it. + +> > effective_cache_size = 65536 # typically 8KB each +> +> What basis did you have to change this? Have you done work +> figuring out how big the kernel's disk cache is regularly on +> that system? + +I read somewhere that this should be set to half the system RAM +size, 64k*8k=512m = 1/2 of the 1 Gig RAM. I guess this is way +off since you're saying that it's disk cache. This agrees with +the documentation. I can't really rely on the (precious little +Solaris postgres) info I find on the net.... ;) + +Unfortunately, setting back to 1000 doesn't appear to help. + +> > Hannu brings up a good point - one that was debated before +> > my attempts at making Solaris faster. If you were going to +> make a +> > fast postgres server what would you use? Assuming you could +> > afford a SunFire 280R (~$8k?), would that money be better +> > spent on a (say) Dell server running (say) linux? We're +> > doing light +> +> I've been finding FreeBSD way faster than Linux. But yes. + +I like to hear this since I'm a big FreeBSD fan. So far I think +I've understood this as: FreeBSD > Linux > OSX > Solaris. + +Thanks much for the input, + +-X + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 14:18:57 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 637324764E0 + for ; + Tue, 14 Jan 2003 14:18:56 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 81A0A4764CE + for ; + Tue, 14 Jan 2003 14:18:53 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18YWaL-0007PS-00 + for ; Tue, 14 Jan 2003 14:18:53 -0500 +Date: Tue, 14 Jan 2003 14:18:53 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac - best Postgres platform? +Message-ID: <20030114141853.V5335@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <20030114133046.T5335@mail.libertyrms.com> + <20030114190149.7293.qmail@web21104.mail.yahoo.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <20030114190149.7293.qmail@web21104.mail.yahoo.com>; + from captainx0r@yahoo.com on Tue, Jan 14, 2003 at 11:01:49AM -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/106 +X-Sequence-Number: 753 + +On Tue, Jan 14, 2003 at 11:01:49AM -0800, CaptainX0r wrote: + +> I changed back to the default 1024, and down to the minimum, 64 +> - no change. I think that was changed simultaneously with some +> other parameter (bad, I know) that actually had an affect. I +> guess I can remove it. + +Very bad to change two things at once. You think it's saving you +time, but now . . . well, you already know what happens ;-) Anyway, +you _still_ shouldn't have it that high. + +> > > effective_cache_size = 65536 # typically 8KB each +> +> I read somewhere that this should be set to half the system RAM +> size, 64k*8k=512m = 1/2 of the 1 Gig RAM. I guess this is way +> off since you're saying that it's disk cache. This agrees with +> the documentation. I can't really rely on the (precious little +> Solaris postgres) info I find on the net.... ;) + +I think you should rely on the Postgres documentation, which has way +fewer errors than just about any other technical documentation I've +ever seen. Yes, it's disk cache. + +I wouldn't set _anything_ to half the system RAM. It'd be real nice +if your disk cache was half your RAM, but I'd be amazed if anyone's +system were that efficient. + +It sounds like you need to follow Tom Lane's advice, though, and do +some profiling. + +A +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 12:33:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id DBBD6475EE4 + for ; + Tue, 14 Jan 2003 12:33:07 -0500 (EST) +Received: from localhost.localdomain (sein.itera.ee [194.126.109.126]) + by postgresql.org (Postfix) with ESMTP id 2F4E1476315 + for ; + Tue, 14 Jan 2003 12:32:34 -0500 (EST) +Received: (from hannu@localhost) + by localhost.localdomain (8.11.6/8.11.6) id h0EJQPo15967; + Tue, 14 Jan 2003 19:26:25 GMT +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: Sun vs. Mac +From: Hannu Krosing +To: captainx0r@yahoo.com +Cc: "pgsql-performance@postgresql.org" +In-Reply-To: <20030114150008.49425.qmail@web21103.mail.yahoo.com> +References: <20030114150008.49425.qmail@web21103.mail.yahoo.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1042572384.15544.84.camel@huli> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 14 Jan 2003 19:26:24 +0000 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/94 +X-Sequence-Number: 741 + +On Tue, 2003-01-14 at 15:00, CaptainX0r wrote: +> Hello, +> +> I'm having some serious performance issues with PostgreSQL on +> our newish SunFire 280R (1 900MHz ultrasparc III, 1 GB RAM). +> It's painfully slow. It took me almost a week of tuning to get +> it in the range of an old Mac G3 laptop. Now, a few days later, +> after tweaking every nearly every parameter (only noting +> decreased performance on some) in /etc/system and +> $PGDATA/postgresql.conf + +could you post your $PGDATA/postgresql.conf for our viewing pleasure ? + +> it's about as fast as I can make it, but +> still horribly slow. A few simple queries that take 1.5-7 +> minutes on the G3 take 1-1.5 minutes on the Sun. A bulk load of +> roughly 2.4 GB database dump takes ~1 hour on each machine. It +> took almost 2 hours on the Sun before I turned off fsync. +> +> We have plans to add another CPU, RAM and another disk, which +> should all help, + +Another CPU will probably not help with bulk loads or other single-user +stuff. + +> but in its current state, I (and many others) +> would think that it should run circles around the G3. I'm +> thinking that I'm missing something big and obvious because this +> can't be right. Otherwise we might as well just get a bunch of +> ibooks to run our databases - they're a lot smaller and much +> more quiet. + +For single-user tasks you will probably be better off by getting a +gray box with Athlon 2600+ with 3 Gigs of memory and IDE disks +and running Linux or *BSD . + +> Can someone please point me in the right direction? +> +> Thanks, +> +> -X +> +> __________________________________________________ +> Do you Yahoo!? +> Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +> http://mailplus.yahoo.com +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Wed Jan 15 15:17:55 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id AFFE74771CD + for ; + Wed, 15 Jan 2003 15:17:53 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 5045D476624 + for ; + Wed, 15 Jan 2003 14:30:29 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2315106; Wed, 15 Jan 2003 11:30:32 -0800 +Content-Type: text/plain; + charset="utf-8" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: "Roman Fail" , + +Subject: Re: 7.3.1 New install, large queries are slow +Date: Tue, 14 Jan 2003 11:32:32 -0800 +X-Mailer: KMail [version 1.4] +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301141132.32277.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/120 +X-Sequence-Number: 767 + +Roman, + +First, if this is a dedicated PostgreSQL server, you should try increasing= +=20 +your shared_buffers to at least 512mb (65536) if not 1GB (double that) and= +=20 +adjust your shmmax and shmmall to match. + +Second, you will probably want to increase your sort_mem as well. How much= +=20 +depeneds on the number of concurrent queries you expect to be running and= +=20 +their relative complexity. Give me that information, and I'll offer you= +=20 +some suggestions. Part of your slow query=20 + +Your query problem is hopefully relatively easy. The following clause is 9= +5%=20 +of your query time: + +> -> Index Scan using=20 +batchdetail_ix_tranamount_idx on batchdetail d (cost=3D0.00..176768.18=20 +rows=3D44010 width=3D293) (actual time=3D35.48..1104625.54 rows=3D370307 lo= +ops=3D1)=20 +>=20 + +See the actual time figures? This one clause is taking 1,104,590 msec!=20= +=20=20 + +Now, why? + +Well, look at the cost estimate figures in contrast to the actual row count: +estimate rows =3D 44,010 real rows 370,307 +That's off by a factor of 9. This index scan is obviously very cumbersome= +=20 +and is slowing the query down. Probably it should be using a seq scan=20 +instead ... my guess is, you haven't run ANALYZE in a while and the incorre= +ct=20 +row estimate is causing the parser to choose a very slow index scan. + +Try running ANALYZE on your database and re-running the query. Also try= +=20 +using REINDEX on batchdetail_ix_tranamount_idx . + +Second, this clause near the bottom: + + -> Seq Scan on purc1 p1 (cost=3D0.00..442= +59.70=20 +rows=3D938770 width=3D19) (actual time=3D98.09..4187.32 rows=3D938770 loops= +=3D5)=20 + +... suggests that you could save an additional 4 seconds by figuring out a = +way=20 +for the criteria on purc1 to use a relevant index -- but only after you've= +=20 +solved the problem with batchdetail_ix_tranamount_idx. + +Finally, if you really want help, post the query. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 14:39:13 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A9149475D01 + for ; + Tue, 14 Jan 2003 14:39:11 -0500 (EST) +Received: from web21106.mail.yahoo.com (web21106.mail.yahoo.com + [216.136.227.108]) + by postgresql.org (Postfix) with SMTP id 5A8F24765D2 + for ; + Tue, 14 Jan 2003 14:38:28 -0500 (EST) +Message-ID: <20030114193828.37133.qmail@web21106.mail.yahoo.com> +Received: from [131.142.161.245] by web21106.mail.yahoo.com via HTTP; + Tue, 14 Jan 2003 11:38:28 PST +Date: Tue, 14 Jan 2003 11:38:28 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac +To: pgsql-performance@postgresql.org +In-Reply-To: <17342.1042568154@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/107 +X-Sequence-Number: 754 + +> I believe top's percent-of-CPU numbers for individual +> processes are time +> averages over a minute or so, so the ramping effect is +> unsurprising. + +Thanks - this makes much more sense. + +> > This doesn't really tell me much, except I'm guessing that +> > PG is CPU bound? +> +> Yup, that seems pretty clear. Next step is to find out what +> the heck +> it's doing. My instinct would be to use gprof. Recompile +> with +> profiling enabled --- if you're using gcc, this should work +> cd postgres-distribution/src/backend +> make clean +> make PROFILE=-pg all +> make install-bin -- may need to stop postmaster +> Next run some sample queries (put them all into one session). +> After quitting the session, find gmon.out in the +> $PGDATA/base/nnn/ subdirectory corresponding to your database, + +> and feed it to gprof. +> The results should show where the code hotspot is. + +Well if that isn't a fancy bit of info.... Thanks! + +gprof says: + +Fatal ELF error: can't read ehdr (Request error: class +file/memory mismatch) + +I'm guessing that's not what we're expecting... I'm using +/usr/ccs/bin/gprof - maybe there's a better one? + +-X + + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Jan 14 14:44:12 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 83CC1475BA1 + for ; + Tue, 14 Jan 2003 14:44:11 -0500 (EST) +Received: from pd6mo1so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net + [24.71.223.10]) by postgresql.org (Postfix) with ESMTP id 0DDF2475B8F + for ; + Tue, 14 Jan 2003 14:44:11 -0500 (EST) +Received: from pd6mr1so.prod.shaw.ca + (pd6mr1so-qfe3.prod.shaw.ca [10.0.141.216]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H8P00FP3YTNCN@l-daemon> for + pgsql-performance@postgresql.org; + Tue, 14 Jan 2003 12:44:11 -0700 (MST) +Received: from pn2ml5so.prod.shaw.ca + (pn2ml5so-qfe0.prod.shaw.ca [10.0.121.149]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H8P003NTYTN5S@l-daemon> for + pgsql-performance@postgresql.org; + Tue, 14 Jan 2003 12:44:11 -0700 (MST) +Received: from kimiko (h24-78-132-76.vc.shawcable.net [24.78.132.76]) + by l-daemon (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 + 2002)) with SMTP id <0H8P0088WYTMNK@l-daemon> for + pgsql-performance@postgresql.org; + Tue, 14 Jan 2003 12:44:11 -0700 (MST) +Date: Tue, 14 Jan 2003 11:42:07 -0800 +From: Vernon Wu +Subject: How good I can get +To: pgsql-performance@postgresql.org +Reply-To: vernonw@gatewaytech.com +Message-id: <65TWVMK3ZVRRMF0DYTHF74KGKE08CA.3e24680f@kimiko> +MIME-version: 1.0 +X-Mailer: Opera 6.05 build 1140 +Content-type: text/plain; charset=iso-8859-1 +Content-transfer-encoding: 7BIT +X-Priority: 3 (Normal) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/108 +X-Sequence-Number: 755 + +In my current project, among of over twenty main tables, three of them are the master tables and result are the +multivalued detail tables. All of those table have the field name userid which is varchar data type. + +A selection statement, having a level of subquery, can involve up to twenty tables. After some query statement tuning +and indexing (on all of the multivalued field of all the detail table), a query performance improves spectacularly. The +following is the output of ?explain analyze? on a query involved ten tables. + +NOTICE: QUERY PLAN: + +Result (cost=0.00..23.42 rows=1 width=939) (actual time=28.00..28.00 rows=0 loops=1) +. . . +Total runtime: 31.00 msec + +I would like to find any performance improvement potentiality in terms of DB table design (indexing always can be done +later). The first thing I know I can do is to change the join key, userid, to numeral. Since implementing the change +requests some work on the system, I would like to know how significant performance improement it can bring. + +Almost all fields of those tables are a single digit character. I can guess that change them to number type also can +improve the selection performance. My question again is how much it can get. The application is a web application. All +data on a page is a string, or text type. All number type data has to be parsed from a string to the back-end, and +converted into a string from the back end. So that change will have performance overhead on the application. + +Thanks for your input. + +Vernon + + + + + +From pgsql-performance-owner@postgresql.org Wed Jan 15 16:33:27 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5CBDF476D2E + for ; + Wed, 15 Jan 2003 16:21:18 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id D50AB476E7C + for ; + Wed, 15 Jan 2003 15:34:11 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2315206; Wed, 15 Jan 2003 12:34:15 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Tomasz Myrta +Subject: Re: complicated queries in pl/pgsql +Date: Tue, 14 Jan 2003 12:36:15 -0800 +X-Mailer: KMail [version 1.4] +Cc: PgSQL Performance ML +References: <3E23EC83.9060802@klaster.net> + <200301131044.50424.josh@agliodbs.com> + <3E25B29C.9040408@klaster.net> +In-Reply-To: <3E25B29C.9040408@klaster.net> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301141236.15915.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/124 +X-Sequence-Number: 771 + + +Tomasz, + +> Thanks a lot. +> I'm asking, because I use some queries which are easy to change into=20 +> views. Most of their execution time takes planning, they use 5-10=20 +> explicit table joins with not too many rows in these tables and returns= +=20 +> few values. + +You might want to investigate the new "prepared query" functionality in 7.3= +.1. + +I haven't used it yet, so I can't help much. + + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 15:51:16 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id ED3684761D1 + for ; + Tue, 14 Jan 2003 15:51:15 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 717D5476009 + for ; + Tue, 14 Jan 2003 15:51:15 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP id C70121479C + for ; + Tue, 14 Jan 2003 15:51:16 -0500 (EST) +Date: Tue, 14 Jan 2003 15:51:16 -0500 +Mime-Version: 1.0 (Apple Message framework v551) +Content-Type: text/plain; charset=US-ASCII; format=flowed +Subject: Multiple databases +From: Noah Silverman +To: pgsql-performance@postgresql.org +Content-Transfer-Encoding: 7bit +Message-Id: +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/109 +X-Sequence-Number: 756 + +Hi, + +A quick configuration question for everybody... + +When we create more than one database with psql, it appears as if +everything is thrown into the same directory. +I can understand having all the tables and indexes for a given database +in the same directory, but multiple databases? + +Do we need to configure something differently, or is this just how +postgres works? + +Thanks, + +-Noah + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 15:54:50 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BEE1D475D01 + for ; + Tue, 14 Jan 2003 15:54:48 -0500 (EST) +Received: from jester.senspire.com (unknown [216.208.117.7]) + by postgresql.org (Postfix) with ESMTP id 109A8475B8F + for ; + Tue, 14 Jan 2003 15:54:48 -0500 (EST) +Received: from [127.0.0.1] (localhost [127.0.0.1]) + by jester.senspire.com (8.12.6/8.12.6) with ESMTP id h0EKsscb015604; + Tue, 14 Jan 2003 15:54:54 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: Multiple databases +From: Rod Taylor +To: Noah Silverman +Cc: Pgsql Performance +In-Reply-To: +References: +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-/ecQ6gKMtPf4fQYWobvE" +Organization: +Message-Id: <1042577693.14661.73.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 14 Jan 2003 15:54:54 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/110 +X-Sequence-Number: 757 + +--=-/ecQ6gKMtPf4fQYWobvE +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +> Do we need to configure something differently, or is this just how=20 +> postgres works? + +Thats just how it works. Under 'base' there are a number of numbered +directories which represent various databases. + +If you really want, take a look at the "WITH LOCATION" option for create +database. + + +Command: CREATE DATABASE +Description: create a new database +Syntax: +CREATE DATABASE name + [ [ WITH ] [ OWNER [=3D] dbowner ] + [ LOCATION [=3D] 'dbpath' ] + [ TEMPLATE [=3D] template ] + [ ENCODING [=3D] encoding ] ] + +> Thanks, +>=20 +> -Noah +>=20 +>=20 +> ---------------------------(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 +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-/ecQ6gKMtPf4fQYWobvE +Content-Type: application/pgp-signature; name=signature.asc +Content-Description: This is a digitally signed message part + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (FreeBSD) + +iD8DBQA+JHkd6DETLow6vwwRAmVCAJ9+5oIg4NfRkk8RSO1NDmBPTg+WSgCfZYsJ +YRb4yKYT1AG3BcWHXzcL0GQ= +=B3+k +-----END PGP SIGNATURE----- + +--=-/ecQ6gKMtPf4fQYWobvE-- + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 15:58:03 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 243FE475D01 + for ; + Tue, 14 Jan 2003 15:58:03 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id A8202475B8F + for ; + Tue, 14 Jan 2003 15:58:02 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP + id 4036913F44; Tue, 14 Jan 2003 15:58:04 -0500 (EST) +Date: Tue, 14 Jan 2003 15:58:03 -0500 +Subject: Re: Multiple databases +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: Pgsql Performance +To: Rod Taylor +From: Noah Silverman +In-Reply-To: <1042577693.14661.73.camel@jester> +Message-Id: +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/111 +X-Sequence-Number: 758 + +Thanks, + +Can someone give me a good description of what the various directories +and files actually are. I have RTFMed, but the descriptions there +don't seem to match what I have on my machine. + +Thanks. + + +On Tuesday, January 14, 2003, at 03:54 PM, Rod Taylor wrote: + +>> Do we need to configure something differently, or is this just how +>> postgres works? +> +> Thats just how it works. Under 'base' there are a number of numbered +> directories which represent various databases. +> +> If you really want, take a look at the "WITH LOCATION" option for +> create +> database. +> +> +> Command: CREATE DATABASE +> Description: create a new database +> Syntax: +> CREATE DATABASE name +> [ [ WITH ] [ OWNER [=] dbowner ] +> [ LOCATION [=] 'dbpath' ] +> [ TEMPLATE [=] template ] +> [ ENCODING [=] encoding ] ] +> +>> Thanks, +>> +>> -Noah +>> +>> +>> ---------------------------(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 +> -- +> Rod Taylor +> +> PGP Key: http://www.rbt.ca/rbtpub.asc +> + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 18:56:55 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 21DCC4764B3 + for ; + Tue, 14 Jan 2003 18:56:53 -0500 (EST) +Received: from new-smtp2.ihug.com.au (new-smtp2.ihug.com.au [203.109.250.28]) + by postgresql.org (Postfix) with ESMTP id 1777847611B + for ; + Tue, 14 Jan 2003 18:56:33 -0500 (EST) +Received: from p96-tnt1.adl.ihug.com.au (postgresql.org) [203.173.248.96] + by new-smtp2.ihug.com.au with esmtp (Exim 3.22 #1 (Debian)) + id 18Yav4-0003Qi-00; Wed, 15 Jan 2003 10:56:34 +1100 +Message-ID: <3E24A472.6040706@postgresql.org> +Date: Wed, 15 Jan 2003 10:29:46 +1030 +From: Justin Clift +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Andrew Sullivan +Cc: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac - best Postgres platform? +References: <1042572384.15544.84.camel@huli> + <20030114181054.25701.qmail@web21109.mail.yahoo.com> + <20030114133046.T5335@mail.libertyrms.com> +In-Reply-To: <20030114133046.T5335@mail.libertyrms.com> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/113 +X-Sequence-Number: 760 + +Andrew Sullivan wrote: + + > I've been finding FreeBSD way faster than Linux. But yes. + +Out of curiosity, have you been trying FreeBSD 4.7x or the developer +releases of 5.0? Apparently there are new kernel scheduling +improvements in FreeBSD 5.0 that will help certain types of tasks and +might boost our performance further. + +Would be interested in seeing if the profiling/optimisation options of +GCC 3.2.x are useful as well. + +:-) + +Regards and best wishes, + +Justin Clift + + + > A + + +-- +"My grandfather once told me that there are two kinds of people: those +who work and those who take the credit. He told me to try to be in the +first group; there was less competition there." +- Indira Gandhi + + +From pgsql-performance-owner@postgresql.org Tue Jan 14 19:02:23 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 787624763F2 + for ; + Tue, 14 Jan 2003 19:02:21 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id E87CE475B8F + for ; + Tue, 14 Jan 2003 19:01:58 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18Yb0L-0004Yk-00 + for ; Tue, 14 Jan 2003 19:02:01 -0500 +Date: Tue, 14 Jan 2003 19:02:01 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac - best Postgres platform? +Message-ID: <20030114190201.A17481@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <1042572384.15544.84.camel@huli> + <20030114181054.25701.qmail@web21109.mail.yahoo.com> + <20030114133046.T5335@mail.libertyrms.com> + <3E24A472.6040706@postgresql.org> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <3E24A472.6040706@postgresql.org>; + from justin@postgresql.org on Wed, Jan 15, 2003 at 10:29:46AM + +1030 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/114 +X-Sequence-Number: 761 + +On Wed, Jan 15, 2003 at 10:29:46AM +1030, Justin Clift wrote: +> Andrew Sullivan wrote: +> +> > I've been finding FreeBSD way faster than Linux. But yes. +> +> Out of curiosity, have you been trying FreeBSD 4.7x or the developer + +Just 4.7x. And mostly for little jobs for myself, so I can't speak +about testing it in a production case. + +A + + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Wed Jan 15 00:12:35 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5AA19475E75 + for ; + Wed, 15 Jan 2003 00:12:33 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 88A9C475E22 + for ; + Wed, 15 Jan 2003 00:12:32 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0F5Cb5u001984; + Wed, 15 Jan 2003 00:12:37 -0500 (EST) +To: captainx0r@yahoo.com +Cc: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac +In-reply-to: <20030114193828.37133.qmail@web21106.mail.yahoo.com> +References: <20030114193828.37133.qmail@web21106.mail.yahoo.com> +Comments: In-reply-to CaptainX0r + message dated "Tue, 14 Jan 2003 11:38:28 -0800" +Date: Wed, 15 Jan 2003 00:12:37 -0500 +Message-ID: <1983.1042607557@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/115 +X-Sequence-Number: 762 + +CaptainX0r writes: +> gprof says: +> Fatal ELF error: can't read ehdr (Request error: class +> file/memory mismatch) + +Hm, that's a new one on me. Just to eliminate the obvious: you did +read the gprof man page? It typically needs both the pathname of the +postgres executable and that of the gmon.out file. + +If that's not it, I fear you need a gprof expert, which I ain't. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Wed Jan 15 13:13:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 243704773AB + for ; + Wed, 15 Jan 2003 13:13:14 -0500 (EST) +Received: from web21110.mail.yahoo.com (web21110.mail.yahoo.com + [216.136.227.112]) + by postgresql.org (Postfix) with SMTP id 3B8F147757B + for ; + Wed, 15 Jan 2003 12:22:46 -0500 (EST) +Message-ID: <20030115172250.54953.qmail@web21110.mail.yahoo.com> +Received: from [140.247.91.110] by web21110.mail.yahoo.com via HTTP; + Wed, 15 Jan 2003 09:22:50 PST +Date: Wed, 15 Jan 2003 09:22:50 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac - gprof output +To: pgsql-performance@postgresql.org +In-Reply-To: <1983.1042607557@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/116 +X-Sequence-Number: 763 + +All, + +> Hm, that's a new one on me. Just to eliminate the obvious: +> you did read the gprof man page? It typically needs both the +> pathname of the postgres executable and that of the gmon.out + +I read it, but apparently not very well. It appears that as long as gmon.out +is in the current dir, all that's needed is the name of the executeable (with +full path). The way it's formated I read it as all that's needed is the +image-file. Anyways... + +There's a ton of output, so I'm picking what appear to be the highlights. + +granularity: each sample hit covers 4 byte(s) for 0.00% of 705.17 seconds + + called/total parents +index %time self descendents called+self name index + called/total children + +[1] 63.6 446.05 2.65 44386289+57463869 [1] + 442.08 2.50 59491100+2566048020 +[2] + 2.91 0.00 23045572+366 _fini [23] + 0.57 0.00 17763681 _rl_input_available + [42] + 0.11 0.15 478216+7 history_expand [54] + 0.21 0.00 7 history_tokenize_internal + [56] + 0.10 0.00 1071137 tilde_expand [68] + 0.07 0.00 397 rl_gather_tyi [70] + 0.00 0.00 31 qsort [81] + 0.00 0.00 17 rl_insert_close [82] +----------------------------------------------- + +[3] 32.3 0.65 227.47 rl_get_termcap [3] + 226.13 1.34 22502064/44386289 +[2] +----------------------------------------------- + +[4] 26.3 0.78 184.35 rl_stuff_char [4] + 178.51 1.06 17763681/44386289 +[2] + 4.78 0.00 17763681/17763681 rl_clear_signals [18] +----------------------------------------------- + +[5] 15.8 111.61 0.00 rl_signal_handler [5] + 0.00 0.00 1/44386289 +[2] +----------------------------------------------- + +[6] 4.3 30.57 0.00 rl_sigwinch_handler [6] +----------------------------------------------- + +And: + +granularity: each sample hit covers 4 byte(s) for 0.00% of 705.17 seconds + + % cumulative self self total + time seconds seconds calls ms/call ms/call name + 15.8 111.61 111.61 rl_signal_handler [5] + 4.3 142.18 30.57 rl_sigwinch_handler [6] + 1.9 155.42 13.24 rl_set_sighandler [8] + 1.9 168.52 13.10 rl_maybe_set_sighandler +[9] + 1.1 176.37 7.85 _rl_next_macro_key [11] + 0.9 182.38 6.01 rl_read_key [12] + 0.8 188.07 5.69 rl_backward_kill_line [13] + 0.8 193.56 5.49 rl_unix_word_rubout [14] + 0.8 198.91 5.35 _rl_pop_executing_macro +[15] + 0.7 203.73 4.82 _rl_fix_last_undo_of_type +[17] + 0.7 208.51 4.78 17763681 0.00 0.00 rl_clear_signals [18] + 0.6 212.87 4.36 rl_modifying [19] + 0.6 216.95 4.08 rl_begin_undo_group [20] + 0.6 221.00 4.05 rl_tilde_expand [21] + 0.4 223.98 2.98 region_kill_internal [22] + 0.4 226.89 2.91 23045572 0.00 0.00 _fini [23] + + +So. Any thoughts? This looks really useful in the hands of someone who knows +what it all means. Looks like some signal handlers are using up most of the +time. Good? Bad? Am I reading that first part correctly in that a good part +of the time spent is external to Postgres? This report also seems to verify +that qsort isn't a problem since it was the 81st index, with 31 calls (not +much) and 0.00 self seconds. + +Thanks much, + +-X + + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Wed Jan 15 13:47:37 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 34E7E476662 + for ; + Wed, 15 Jan 2003 13:47:35 -0500 (EST) +Received: from pos_pdc.posportal.com (unknown [12.158.169.100]) + by postgresql.org (Postfix) with ESMTP id C4AAF4766E7 + for ; + Wed, 15 Jan 2003 13:00:05 -0500 (EST) +X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3 +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="utf-8" +Content-Transfer-Encoding: base64 +Subject: 7.3.1 New install, large queries are slow +Date: Wed, 15 Jan 2003 10:00:04 -0800 +Message-ID: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [PERFORM] 7.3.1 New install, large queries are slow +Thread-Index: AcK8v+5ZAEtKuS2jTYa5+fDHnXwnag== +From: "Roman Fail" +To: 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+cz01KQ0KVG90YWwgcnVudGltZTogMTE2ODg4MS4xMiBtc2VjDQo= + +From pgsql-performance-owner@postgresql.org Wed Jan 15 14:58:32 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CFBAF476672 + for ; + Wed, 15 Jan 2003 14:58:31 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 97AF6477391 + for ; + Wed, 15 Jan 2003 14:08:27 -0500 (EST) +Received: from klaster.net (pc148.krakow.cvx.ppp.tpnet.pl [213.76.38.148]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP + id C7BCA2B2AE; Wed, 15 Jan 2003 20:05:15 +0100 (CET) +Message-ID: <3E25B29C.9040408@klaster.net> +Date: Wed, 15 Jan 2003 20:12:28 +0100 +From: Tomasz Myrta +User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; + rv:1.2b) Gecko/20021016 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: josh@agliodbs.com +Cc: PgSQL Performance ML +Subject: Re: complicated queries in pl/pgsql +References: <3E23EC83.9060802@klaster.net> + <200301131044.50424.josh@agliodbs.com> +In-Reply-To: <3E23EC83.9060802@klaster.net> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/118 +X-Sequence-Number: 765 + +Josh Berkus wrote: + + > Tomasz, + > + > + > >What happens to view planning - is it performed + > >during view creation, or rather each time view is quered? + > + > + > Each time the view is executed. The only savings in running a view +over a + > regular query is that the view will have taken care of some reference + > expansion and JOIN explication during the CREATE process, but not +planning. + > Also, views can actually be slower if the view is complex enough that +any + > query-time parameters cannot be "pushed down" into the view. + +Thanks a lot. +I'm asking, because I use some queries which are easy to change into +views. Most of their execution time takes planning, they use 5-10 +explicit table joins with not too many rows in these tables and returns +few values. + +Now I know, that queries inside pl/pgsql functions are better in these +situations: +- complex queries whith deep parameters +- execution several times during conection lifetime. + +Can anyone add something? + +Tomasz Myrta + + +From pgsql-performance-owner@postgresql.org Wed Jan 15 15:14:32 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8560B476171 + for ; + Wed, 15 Jan 2003 15:14:31 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id ACD80477031 + for ; + Wed, 15 Jan 2003 14:27:29 -0500 (EST) +Received: from klaster.net (pe106.krakow.cvx.ppp.tpnet.pl [213.76.40.106]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP + id CF6E42B2AE; Wed, 15 Jan 2003 20:24:20 +0100 (CET) +Message-ID: <3E25B716.4090401@klaster.net> +Date: Wed, 15 Jan 2003 20:31:34 +0100 +From: Tomasz Myrta +User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; + rv:1.2b) Gecko/20021016 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Roman Fail +Cc: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/119 +X-Sequence-Number: 766 + +Roman Fail wrote: + + +EXPLAIN ANALYZE RESULTS: +Limit (cost=370518.31..370518.31 rows=1 width=540) (actual time=1168722.18..1168722.20 rows=5 loops=1) + -> Sort (cost=370518.31..370518.31 rows=1 width=540) (actual time=1168722.18..1168722.18 rows=5 loops=1) + Sort Key: b.batchdate + -> Nested Loop (cost=314181.17..370518.30 rows=1 width=540) (actual time=1148191.12..1168722.09 rows=5 loops=1) + Join Filter: ("inner".batchdetailid = "outer".batchdetailid) + -> Nested Loop (cost=314181.17..370461.79 rows=1 width=502) (actual time=1148167.55..1168671.80 rows=5 loops=1) + Join Filter: ("inner".batchdetailid = "outer".batchdetailid) + -> Nested Loop (cost=314181.17..370429.29 rows=1 width=485) (actual time=1148167.48..1168671.45 rows=5 loops=1) + Join Filter: ("inner".batchdetailid = "outer".batchdetailid) + -> Nested Loop (cost=314181.17..370396.79 rows=1 width=476) (actual time=1148167.41..1168671.08 rows=5 loops=1) + Join Filter: ("inner".batchdetailid = "outer".batchdetailid) + -> Nested Loop (cost=314181.17..314402.47 rows=1 width=457) (actual time=1139099.39..1139320.79 rows=5 loops=1) + Join Filter: ("outer".cardtypeid = "inner".cardtypeid) + -> Merge Join (cost=314181.17..314401.24 rows=1 width=443) (actual time=1138912.13..1139133.00 rows=5 loops=1) + Merge Cond: ("outer".batchid = "inner".batchid) + -> Sort (cost=127418.59..127418.59 rows=3 width=150) (actual time=9681.91..9681.93 rows=17 loops=1) + Sort Key: b.batchid + -> Hash Join (cost=120787.32..127418.56 rows=3 width=150) (actual time=7708.04..9681.83 rows=17 loops=1) + Hash Cond: ("outer".merchantid = "inner".merchantid) + -> Merge Join (cost=120781.58..125994.80 rows=283597 width=72) (actual time=7655.57..9320.49 rows=213387 loops=1) + Merge Cond: ("outer".tranheaderid = "inner".tranheaderid) + -> Index Scan using tranheader_ix_tranheaderid_idx on tranheader t (cost=0.00..121.15 rows=1923 width=16) (actual time=0.15..10.86 rows=1923 loops=1) + Filter: (clientid = 6) + -> Sort (cost=120781.58..121552.88 rows=308520 width=56) (actual time=7611.75..8162.81 rows=329431 loops=1) + Sort Key: b.tranheaderid + -> Seq Scan on batchheader b (cost=0.00..79587.23 rows=308520 width=56) (actual time=0.90..4186.30 rows=329431 loops=1) + Filter: (batchdate > '2002-12-15 00:00:00'::timestamp without time zone) + -> Hash (cost=5.74..5.74 rows=1 width=78) (actual time=31.39..31.39 rows=0 loops=1) + -> Index Scan using merchants_ix_merchid_idx on merchants m (cost=0.00..5.74 rows=1 width=78) (actual time=31.38..31.38 rows=1 loops=1) + Index Cond: (merchid = '701252267'::character varying) + -> Sort (cost=186762.59..186872.62 rows=44010 width=293) (actual time=1127828.96..1128725.39 rows=368681 loops=1) + Sort Key: d.batchid + -> Index Scan using batchdetail_ix_tranamount_idx on batchdetail d (cost=0.00..176768.18 rows=44010 width=293) (actual time=35.48..1104625.54 rows=370307 loops=1) + Index Cond: ((tranamount >= 500.0) AND (tranamount <= 700.0)) + -> Seq Scan on cardtype c (cost=0.00..1.10 rows=10 width=14) (actual time=37.44..37.47 rows=10 loops=5) + -> Seq Scan on purc1 p1 (cost=0.00..44259.70 rows=938770 width=19) (actual time=98.09..4187.32 rows=938770 loops=5) + -> Seq Scan on direct dr (cost=0.00..20.00 rows=1000 width=9) (actual time=0.00..0.00 rows=0 loops=5) + -> Seq Scan on carrental cr (cost=0.00..20.00 rows=1000 width=17) (actual time=0.00..0.00 rows=0 loops=5) + -> Seq Scan on checks ck (cost=0.00..40.67 rows=1267 width=38) (actual time=1.03..7.63 rows=1267 loops=5) +Total runtime: 1168881.12 msec + + +It looks like your execution time is not a hardware, but query problem. +Query nearly doesn't use indexes at all. You said, that that you have normalized database, +so you should have a lot of explicit joins, which work pretty well on Postgresql. + +Can you add some examples of your queries? If it is difficult for you, +at least create one example, when you get "Join Filter" on "explain analyze". + + From your analyze result: +Seq Scan on batchheader b (cost=0.00..79587.23 rows=308520 width=56) +Can you write what condition and indexes does batchheader have? + +Regards, +Tomasz Myrta + + +From pgsql-performance-owner@postgresql.org Wed Jan 15 15:37:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id DB4E4477423 + for ; + Wed, 15 Jan 2003 15:37:16 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id C068A477240 + for ; + Wed, 15 Jan 2003 14:44:01 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id DE0EDD60D; Wed, 15 Jan 2003 11:44:01 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id D3D555C02; Wed, 15 Jan 2003 11:44:01 -0800 (PST) +Date: Wed, 15 Jan 2003 11:44:01 -0800 (PST) +From: Stephan Szabo +To: Roman Fail +Cc: +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +Message-ID: <20030115113159.F91182-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/121 +X-Sequence-Number: 768 + + +On Wed, 15 Jan 2003, Roman Fail wrote: + +> The disks are not reading at max speed during the query - when I ran a +> VACUUM ANALYZE (after data migration), sar -b was consistently 100,000 +> block reads/sec. It does not seem like the hardware is holding back +> things here. I read something about 'fsync' recently, would changing +> that setting apply in this case? + +You ran vacuum analyze, but some of the explain still looks suspiciously +like it's using default statistics (dr and cr for example, unless they +really do have 1000 rows). + +What are the actual query and table definitions for the query? + + +From pgsql-performance-owner@postgresql.org Wed Jan 15 15:51:19 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1C5D3477494 + for ; + Wed, 15 Jan 2003 15:51:17 -0500 (EST) +Received: from jester.senspire.com (unknown [216.208.117.7]) + by postgresql.org (Postfix) with ESMTP id D075D476C5B + for ; + Wed, 15 Jan 2003 14:53:01 -0500 (EST) +Received: from [127.0.0.1] (localhost [127.0.0.1]) + by jester.senspire.com (8.12.6/8.12.6) with ESMTP id h0FJrC57055306; + Wed, 15 Jan 2003 14:53:12 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: 7.3.1 New install, large queries are slow +From: Rod Taylor +To: Roman Fail +Cc: Pgsql Performance +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-TKYLVvCycETYl5CgONyR" +Organization: +Message-Id: <1042660391.61110.36.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 15 Jan 2003 14:53:11 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/122 +X-Sequence-Number: 769 + +--=-TKYLVvCycETYl5CgONyR +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +I didn't see the query itself in the message, but it looks to me like +it's poorly formed. Could you send it?=20 + +By quick glance, either you're using a bunch of explicit joins that are +poorly formed (you've made a bad choice in order) or those particular +IDs are really popular. There are a number of sequential scans that +possibly should be index scans. + +> EXPLAIN ANALYZE RESULTS: +> Limit (cost=3D370518.31..370518.31 rows=3D1 width=3D540) (actual time=3D= +1168722.18..1168722.20 rows=3D5 loops=3D1) +> -> Sort (cost=3D370518.31..370518.31 rows=3D1 width=3D540) (actual ti= +me=3D1168722.18..1168722.18 rows=3D5 loops=3D1) +> Sort Key: b.batchdate + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-TKYLVvCycETYl5CgONyR +Content-Type: application/pgp-signature; name=signature.asc +Content-Description: This is a digitally signed message part + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (FreeBSD) + +iD8DBQA+Jbwm6DETLow6vwwRAvdWAJ9babghSXR90MBRe5c/J0iYvmEi5QCcD7WL +37Udyk8vi5YZ+LBBPM0vif4= +=ZuPQ +-----END PGP SIGNATURE----- + +--=-TKYLVvCycETYl5CgONyR-- + + +From pgsql-performance-owner@postgresql.org Wed Jan 15 16:03:39 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 313C44770AD + for ; + Wed, 15 Jan 2003 16:03:35 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 0C1E2477070 + for ; + Wed, 15 Jan 2003 15:10:12 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18YtrY-0005zb-00 + for ; Wed, 15 Jan 2003 15:10:12 -0500 +Date: Wed, 15 Jan 2003 15:10:12 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +Message-ID: <20030115151012.A21930@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com>; + from rfail@posportal.com on Wed, Jan 15, 2003 at 10:00:04AM -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/123 +X-Sequence-Number: 770 + +On Wed, Jan 15, 2003 at 10:00:04AM -0800, Roman Fail wrote: +> I have a query that does many joins (including two very big tables) +> which is slow on Postgres. On PGSQL the query takes 19 minutes, + +There are three things I can think of right off the bat. + +First, the performance of foreign keys is flat-out awful in Postgres. +I suggest avoiding them if you can. + +Second, ordering joins explicitly (with the JOIN keyword) constrains +the planner, and may select bad plan. The explain analyse output +was nice, but I didn't see the query, so I can't tell what the plan +maybe ought to be. + +Third, I didn't see any suggestion that you'd moved the WAL onto its +own disk. That will mostly help when you are under write load; I +guess it's not a problem here, but it's worth keeping in mind. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Wed Jan 15 16:46:14 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8B843476609 + for ; + Wed, 15 Jan 2003 16:38:03 -0500 (EST) +Received: from rh72.home.ee (unknown [194.204.44.121]) + by postgresql.org (Postfix) with ESMTP id 24CD7475DD0 + for ; + Wed, 15 Jan 2003 15:43:10 -0500 (EST) +Received: from rh72.home.ee (localhost.localdomain [127.0.0.1]) + by rh72.home.ee (8.12.5/8.12.5) with ESMTP id h0FKh5Dv002012; + Thu, 16 Jan 2003 01:43:06 +0500 +Received: (from hannu@localhost) + by rh72.home.ee (8.12.5/8.12.5/Submit) id h0FKh0cC002010; + Thu, 16 Jan 2003 01:43:00 +0500 +X-Authentication-Warning: rh72.home.ee: hannu set sender to hannu@tm.ee using + -f +Subject: Re: 7.3.1 New install, large queries are slow +From: Hannu Krosing +To: Roman Fail +Cc: pgsql-performance@postgresql.org +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1042663379.1951.1.camel@rh72.home.ee> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 16 Jan 2003 01:42:59 +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/125 +X-Sequence-Number: 772 + +Roman Fail kirjutas K, 15.01.2003 kell 23:00: +> I am trying to get a PostgreSQL server into production (moving from MSSQL2K) but having some serious performance issues. PostgreSQL is new to me, and I'm only just now comfortable with Linux. So far I've succesfully compiled postgres from source and migrated all the data from MSSQL. Postgres is primarily accessed using JDBC. +> +> I really want to use Postgres for production, but if I can't get better results out of it by the end of the week we are dropping it forever and going back to MSSQL despite the $$$. I'm basically at a point where I've got to find help from the list. Please help me make this server fly! +> +> I have a query that does many joins (including two very big tables) which is slow on Postgres. On PGSQL the query takes 19 minutes, but only 3 seconds on MSSQL. The two servers have the same indexes created (including primary key indexes). I finally gave up on creating all the foreign keys in Postgres - after 12 hours of 100% CPU. It's hard for me to believe that the hardware is the bottleneck - the $20k Postgres server far outclasses the MSSQL server (see below for stats). When I ran EXPLAIN ANALYZE for this query the CPU averaged 5%, sar -b shows about 6,000 block reads/sec, and vmstat had zero swapping. EXPLAIN results are below, I'm not sure how to interpret them. +> + +Two questions: + +1) Have you run analyze on this database (after loading the data ?) + +2) could you also post the actual query - it would make interpreting the +EXPLAIN ANALYZE RESULTS easier. + +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Wed Jan 15 21:03:06 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0402347671F + for ; + Wed, 15 Jan 2003 19:08:00 -0500 (EST) +Received: from pos_pdc.posportal.com (unknown [12.158.169.100]) + by postgresql.org (Postfix) with ESMTP id 3C17C4770C0 + for ; + Wed, 15 Jan 2003 18:30:53 -0500 (EST) +X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3 +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="utf-8" +Content-Transfer-Encoding: base64 +Subject: Re: 7.3.1 New install, large queries are slow +Date: Wed, 15 Jan 2003 15:30:55 -0800 +Message-ID: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [PERFORM] 7.3.1 New install, large queries are slow +Thread-Index: AcK8zJAtURIYvO7lT4yitE5PKXLVXwAB6nQw +From: "Roman Fail" +To: , +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/126 +X-Sequence-Number: 773 + +VGhhbmtzIHRvIGV2ZXJ5b25lIGZvciB0aGUgcXVpY2sgcmVwbGllcyEgIEkn +bSBzdXJlIHRoYXQgbXkgbGFjayBvZiBza2lsbCB3aXRoIFNRTCBxdWVyaWVz +IGlzIHRoZSBtYWluIHByb2JsZW0uICBXaGF0J3Mgc3RyYW5nZSB0byBtZSBp +cyBob3cgTVNTUUwgdGFrZXMgbXkgYmFkIHF1ZXJpZXMgYW5kIG1ha2VzIHRo +ZW0gbG9vayBnb29kIGFueXdheS4gIEl0IG11c3QgaGF2ZSBhIHJlYWwgc21h +cnQgcGxhbm5lci4NCiANClNldmVyYWwgY2hhbmdlczogIHNoYXJlZF9idWZm +ZXJzID0gMTMxMDcyLCBzb3J0X21lbSA9IDMyNzY4LCBzaG1tYXggPSAyMDk3 +MTUyMDAwLCBzaG1hbGwgPSAxMzEwNzIwMDAuICBJIGNvdWxkbid0IGZpbmQg +YW55IGluZm8gb3V0IHRoZXJlIG9uIHRoZSByZWxhdGlvbnNoaXAgYmV0d2Vl +biBzaG1tYXggYW5kIHNobWFsbCwgc28gSSBqdXN0IHByZXNlcnZlZCB0aGUg 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+Received: from filer (12-235-198-106.client.attbi.com [12.235.198.106]) + by postgresql.org (Postfix) with ESMTP id B1F054772A2 + for ; + Wed, 15 Jan 2003 21:05:21 -0500 (EST) +Received: from localhost (localhost [127.0.0.1]) (uid 1000) + by filer with local; Wed, 15 Jan 2003 18:05:27 -0800 +Date: Wed, 15 Jan 2003 18:05:27 -0800 +From: Kevin Brown +To: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +Message-ID: <20030116020527.GA28172@filer> +Mail-Followup-To: Kevin Brown , + pgsql-performance@postgresql.org +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BF9@pos_pdc.posportal.com> +User-Agent: Mutt/1.4i +Organization: Frobozzco International +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/127 +X-Sequence-Number: 774 + +Roman Fail wrote: +> I am trying to get a PostgreSQL server into production (moving from +> MSSQL2K) but having some serious performance issues. PostgreSQL is +> new to me, and I'm only just now comfortable with Linux. So far +> I've succesfully compiled postgres from source and migrated all the +> data from MSSQL. Postgres is primarily accessed using JDBC. + +[...] + +> POSTGRESQL SYSTEM: +> Red Hat Linux 8.0, PostgreSQL 7.3.1 (dedicated, besides SSH daemon) +> Dell PE6600 Dual Xeon MP 2.0GHz, 2MB L3 cache,HyperThreading enabled +> 4.0 GB Physical RAM +> /dev/sda1: ext3 101MB /boot +> /dev/sda2: ext3 34GB / (sda is 2 disk RAID-1) +> none : swap 1.8GB +> /dev/sdb1: ext3 104GB /usr/local/pgsql/data (sdb is 6 disk RAID-10) +> All 8 drives are 36GB, 15k RPM, Ultra160 SCSI +> PERC3/DC 128MB RAID controller + +Ext3, huh? Ext3 is a journalling filesystem that is capable of +journalling data as well as metadata. But if you mount it such that +it journals data, writes will be significantly slower. + +The default for ext3 is to do ordered writes: data is written before +the associated metadata transaction commits, but the data itself isn't +journalled. But because PostgreSQL synchronously writes the +transaction log (using fsync() by default, if I'm not mistaken) and +uses sync() during a savepoint, I would think that ordered writes at +the filesystem level would probably buy you very little in the way of +additional data integrity in the event of a crash. + +So if I'm right about that, then you might consider using the +"data=writeback" option to ext3 on the /usr/local/pgsql/data +filesystem. I'd recommend the default ("data=ordered") for everything +else. + + +That said, I doubt the above change will make the orders of magnitude +difference you're looking for. But every little bit helps... + +You might also consider experimenting with different filesystems, but +others here may be able to chime in with better information on that. + + +People, please correct me if I'm wrong in my analysis of PostgreSQL on +ext3 above. If the database on an ext3 filesystem mounted in +writeback mode is subject to corruption upon a crash despite the +efforts PostgreSQL makes to keep things sane, then writeback mode +shouldn't be used! And clearly it shouldn't be used if it doesn't +make a significant performance difference. + + + + + +-- +Kevin Brown kevin@sysexperts.com + +From pgsql-performance-owner@postgresql.org Wed Jan 15 22:44:59 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 83AC8476226 + for ; + Wed, 15 Jan 2003 22:43:33 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 242C447667D + for ; + Wed, 15 Jan 2003 22:40:00 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 8E30FD60D; Wed, 15 Jan 2003 19:40:04 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 83EA95C02; Wed, 15 Jan 2003 19:40:04 -0800 (PST) +Date: Wed, 15 Jan 2003 19:40:04 -0800 (PST) +From: Stephan Szabo +To: Roman Fail +Cc: , +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> +Message-ID: <20030115192815.T98147-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/128 +X-Sequence-Number: 775 + + +> So here's the query, and another EXPLAIN ANALYZE to go with it +> (executed after all setting changes). The same result columns and +> JOINS are performed all day with variations on the WHERE clause; other +> possible search columns are the ones that are indexed (see below). +> The 4 tables that use LEFT JOIN only sometimes have matching records, +> hence the OUTER join. +> +> EXPLAIN ANALYZE +> SELECT b.batchdate, d.batchdetailid, t.bankno, d.trandate, d.tranamount, +> d.submitinterchange, d.authamount, d.authno, d.cardtypeid, d.mcccode, +> m.name AS merchantname, c.cardtype, m.merchid, +> p1.localtaxamount, p1.productidentifier, dr.avsresponse, +> cr.checkoutdate, cr.noshowindicator, ck.checkingacctno, +> ck.abaroutingno, ck.checkno +> FROM tranheader t +> INNER JOIN batchheader b ON t.tranheaderid = b.tranheaderid +> INNER JOIN merchants m ON m.merchantid = b.merchantid +> INNER JOIN batchdetail d ON d.batchid = b.batchid +> INNER JOIN cardtype c ON d.cardtypeid = c.cardtypeid +> LEFT JOIN purc1 p1 ON p1.batchdetailid = d.batchdetailid +> LEFT JOIN direct dr ON dr.batchdetailid = d.batchdetailid +> LEFT JOIN carrental cr ON cr.batchdetailid = d.batchdetailid +> LEFT JOIN checks ck ON ck.batchdetailid = d.batchdetailid +> WHERE t.clientid = 6 +> AND d.tranamount BETWEEN 500.0 AND 700.0 +> AND b.batchdate > '2002-12-15' +> AND m.merchid = '701252267' +> ORDER BY b.batchdate DESC +> LIMIT 50 + +Well, you might get a little help by replace the from with + something like: + +FROM transheader t, batchheader b, merchants m, cardtype c, +batchdetail d +LEFT JOIN purc1 p1 on p1.batchdetailid=d.batchdetailid +LEFT JOIN direct dr ON dr.batchdetailid = d.batchdetailid +LEFT JOIN carrental cr ON cr.batchdetailid = d.batchdetailid +LEFT JOIN checks ck ON ck.batchdetailid = d.batchdetailid + +and adding +AND t.tranheaderid=b.tranheaderid +AND m.merchantid=b.merchantid +AND d.batchid=b.batchid +AND c.cardtypeid=d.cardtypeid +to the WHERE conditions. + +That should at least allow it to do some small reordering +of the joins. I don't think that alone is going to do much, +since most of the time seems to be on the scan of d. + +What does vacuum verbose batchdetail give you (it'll give +an idea of pages anyway) + + + + + + +From pgsql-performance-owner@postgresql.org Wed Jan 15 22:46:23 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7DE64475BEC + for ; + Wed, 15 Jan 2003 22:46:21 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id B64CD47635A + for ; + Wed, 15 Jan 2003 22:46:11 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 31052D60D; Wed, 15 Jan 2003 19:46:16 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 26BE55C02; Wed, 15 Jan 2003 19:46:16 -0800 (PST) +Date: Wed, 15 Jan 2003 19:46:16 -0800 (PST) +From: Stephan Szabo +To: Roman Fail +Cc: , +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> +Message-ID: <20030115194528.U98448-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/129 +X-Sequence-Number: 776 + + +On Wed, 15 Jan 2003, Roman Fail wrote: + +> Thanks to everyone for the quick replies! I'm sure that my lack of +> skill with SQL queries is the main problem. What's strange to me is +> how MSSQL takes my bad queries and makes them look good anyway. It +> must have a real smart planner. + +As a followup, if you do +set enable_indexscan=off; +before running the explain analyze, what does that give you? + + +From pgsql-performance-owner@postgresql.org Wed Jan 15 23:35:24 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 22181475E23 + for ; + Wed, 15 Jan 2003 23:35:22 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 880EF475DC0 + for ; + Wed, 15 Jan 2003 23:35:21 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0G4Z05u011548; + Wed, 15 Jan 2003 23:35:00 -0500 (EST) +To: "Roman Fail" +Cc: josh@agliodbs.com, pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> +Comments: In-reply-to "Roman Fail" + message dated "Wed, 15 Jan 2003 15:30:55 -0800" +Date: Wed, 15 Jan 2003 23:35:00 -0500 +Message-ID: <11547.1042691700@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/130 +X-Sequence-Number: 777 + +"Roman Fail" writes: +> Thanks to everyone for the quick replies! I'm sure that my lack of +> skill with SQL queries is the main problem. What's strange to me is +> how MSSQL takes my bad queries and makes them look good anyway. It +> must have a real smart planner. + +I think more likely the issue is that your use of JOIN syntax is forcing +Postgres into a bad plan. MSSQL probably doesn't assign any semantic +significance to the use of "a JOIN b" syntax as opposed to "FROM a, b" +syntax. Postgres does. Whether this is a bug or a feature depends on +your point of view --- but there are folks out there who find it to be +a life-saver. You can find some explanations at +http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/explicit-joins.html + +> Is it pretty much universally accepted that I should drop all my +> foreign keys? + +No. They don't have any effect on SELECT performance in Postgres. +They will impact update speed, but that's not your complaint (at the +moment). Don't throw away data integrity protection until you know +you need to. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Wed Jan 15 23:41:56 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2FC46476673 + for ; + Wed, 15 Jan 2003 23:41:53 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 550284766CB + for ; + Wed, 15 Jan 2003 23:41:04 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2315724; Wed, 15 Jan 2003 20:41:11 -0800 +From: "Josh Berkus" +Subject: Re: 7.3.1 New install, large queries are slow +To: Tom Lane , "Roman Fail" +Cc: josh@agliodbs.com, pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Wed, 15 Jan 2003 20:41:11 -0800 +Message-ID: +In-Reply-To: <11547.1042691700@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/131 +X-Sequence-Number: 778 + +Tom, Roman, + +> I think more likely the issue is that your use of JOIN syntax is +> forcing +> Postgres into a bad plan. MSSQL probably doesn't assign any semantic +> significance to the use of "a JOIN b" syntax as opposed to "FROM a, +> b" +> syntax. + +That's correct. MSSQL will reorder equijoins, even when explicitly +declared. + +Hey, Roman, how many records in BatchDetail, anyway? + +Josh Berkus + +From pgsql-performance-owner@postgresql.org Wed Jan 15 23:48:43 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 229F5475C22 + for ; + Wed, 15 Jan 2003 23:48:40 -0500 (EST) +Received: from filer (12-235-198-106.client.attbi.com [12.235.198.106]) + by postgresql.org (Postfix) with ESMTP id 7E0B1475BEC + for ; + Wed, 15 Jan 2003 23:48:39 -0500 (EST) +Received: from localhost (localhost [127.0.0.1]) (uid 1000) + by filer with local; Wed, 15 Jan 2003 20:48:47 -0800 +Date: Wed, 15 Jan 2003 20:48:47 -0800 +From: Kevin Brown +To: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +Message-ID: <20030116044847.GA29781@filer> +Mail-Followup-To: Kevin Brown , + pgsql-performance@postgresql.org +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> + <11547.1042691700@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +In-Reply-To: <11547.1042691700@sss.pgh.pa.us> +User-Agent: Mutt/1.4i +Organization: Frobozzco International +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/132 +X-Sequence-Number: 779 + +Tom Lane wrote: +> "Roman Fail" writes: +> > Thanks to everyone for the quick replies! I'm sure that my lack of +> > skill with SQL queries is the main problem. What's strange to me is +> > how MSSQL takes my bad queries and makes them look good anyway. It +> > must have a real smart planner. +> +> I think more likely the issue is that your use of JOIN syntax is forcing +> Postgres into a bad plan. MSSQL probably doesn't assign any semantic +> significance to the use of "a JOIN b" syntax as opposed to "FROM a, b" +> syntax. Postgres does. Whether this is a bug or a feature depends on +> your point of view --- but there are folks out there who find it to be +> a life-saver. + +Since it *does* depend on one's point of view, would it be possible to +have control over this implemented in a session-defined variable (with +the default in the GUC, of course)? I wouldn't be surprised if a lot +of people get bitten by this. + + +-- +Kevin Brown kevin@sysexperts.com + +From pgsql-performance-owner@postgresql.org Thu Jan 16 00:07:52 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1336E475DC0 + for ; + Thu, 16 Jan 2003 00:07:48 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 607C8475C22 + for ; + Thu, 16 Jan 2003 00:07:47 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0G57q5u011771; + Thu, 16 Jan 2003 00:07:52 -0500 (EST) +To: Kevin Brown +Cc: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: <20030116044847.GA29781@filer> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> + <11547.1042691700@sss.pgh.pa.us> <20030116044847.GA29781@filer> +Comments: In-reply-to Kevin Brown + message dated "Wed, 15 Jan 2003 20:48:47 -0800" +Date: Thu, 16 Jan 2003 00:07:52 -0500 +Message-ID: <11770.1042693672@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/133 +X-Sequence-Number: 780 + +Kevin Brown writes: +> Tom Lane wrote: +>> ... Whether this is a bug or a feature depends on +>> your point of view --- but there are folks out there who find it to be +>> a life-saver. + +> Since it *does* depend on one's point of view, would it be possible to +> have control over this implemented in a session-defined variable (with +> the default in the GUC, of course)? + +I have no objection to doing that --- anyone care to contribute code to +make it happen? (I think the trick would be to fold plain-JOIN jointree +entries into FROM-list items in planner.c, somewhere near the code that +hoists sub-SELECTs into the main join tree. But I haven't tried it, and +have no time to in the near future.) + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 16 01:11:53 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id AF5F947648B + for ; + Thu, 16 Jan 2003 01:11:50 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 0C14F4764A7 + for ; + Thu, 16 Jan 2003 01:11:49 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0G6Bm5u012203; + Thu, 16 Jan 2003 01:11:48 -0500 (EST) +To: captainx0r@yahoo.com +Cc: pgsql-performance@postgresql.org +Subject: Re: Sun vs. Mac - gprof output +In-reply-to: <20030115172250.54953.qmail@web21110.mail.yahoo.com> +References: <20030115172250.54953.qmail@web21110.mail.yahoo.com> +Comments: In-reply-to CaptainX0r + message dated "Wed, 15 Jan 2003 09:22:50 -0800" +Date: Thu, 16 Jan 2003 01:11:48 -0500 +Message-ID: <12202.1042697508@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/134 +X-Sequence-Number: 781 + +CaptainX0r writes: +> % cumulative self self total +> time seconds seconds calls ms/call ms/call name +> 15.8 111.61 111.61 rl_signal_handler [5] +> 4.3 142.18 30.57 rl_sigwinch_handler [6] +> 1.9 155.42 13.24 rl_set_sighandler [8] +> 1.9 168.52 13.10 rl_maybe_set_sighandler +> [9] +> 1.1 176.37 7.85 _rl_next_macro_key [11] +> 0.9 182.38 6.01 rl_read_key [12] +> 0.8 188.07 5.69 rl_backward_kill_line [13] + +All of these names correspond to internal routines in libreadline. + +It'd not be surprising for libreadline to suck a good deal of the +runtime of psql ... but I don't believe the backend will call it at all. +So, either this trace is erroneous, or you profiled the wrong process +(client instead of backend), or there's something truly weird going on. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 16 04:03:51 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 375BB476128 + for ; + Thu, 16 Jan 2003 04:03:49 -0500 (EST) +Received: from pos_pdc.posportal.com (unknown [12.158.169.100]) + by postgresql.org (Postfix) with ESMTP id ABD77475D93 + for ; + Thu, 16 Jan 2003 04:03:47 -0500 (EST) +X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3 +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="utf-8" +Content-Transfer-Encoding: base64 +Subject: Re: 7.3.1 New install, large queries are slow +Date: Thu, 16 Jan 2003 01:03:43 -0800 +Message-ID: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C02@pos_pdc.posportal.com> +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [PERFORM] 7.3.1 New install, large queries are slow +Thread-Index: AcK9GX1//W2i8AeRQnaE5W1F2Gh0lAAGCuHA +From: "Roman Fail" +To: "Josh Berkus" , + "Tom Lane" , +Cc: 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+Lml0IHNlZW1zIHRoaXMgaW5kZXggc2NhbiBpcyBhIGJpZyBwYXJ0IG9mIHRo +ZSBwcm9ibGVtLiAgSSdtIHN0aWxsIHJlYWxseSBjdXJpb3VzIHdoeSB0aGUg +ZGlzayByZWFkcyBhcmUgc28gZmV3IHdpdGggdGhlIGluZGV4IHNjYW4uICBM +ZXQncyBob3BlIEkgY2FuIGdldCBpdCBuZWFyIHRoZSAzIHNlY29uZCB0aW1l +IGZvciBNU1NRTCBieSBGcmlkYXkhDQogDQpSb21hbiBGYWlsDQogDQo= + +From pgsql-performance-owner@postgresql.org Thu Jan 16 05:40:23 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 80EB247621A + for ; + Thu, 16 Jan 2003 05:40:21 -0500 (EST) +Received: from filer (12-235-198-106.client.attbi.com [12.235.198.106]) + by postgresql.org (Postfix) with ESMTP id DF1DF47618E + for ; + Thu, 16 Jan 2003 05:40:20 -0500 (EST) +Received: from localhost (localhost [127.0.0.1]) (uid 1000) + by filer with local; Thu, 16 Jan 2003 02:40:26 -0800 +Date: Thu, 16 Jan 2003 02:40:25 -0800 +From: Kevin Brown +To: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +Message-ID: <20030116104025.GB29781@filer> +Mail-Followup-To: Kevin Brown , + pgsql-performance@postgresql.org +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> + <11547.1042691700@sss.pgh.pa.us> <20030116044847.GA29781@filer> + <11770.1042693672@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +In-Reply-To: <11770.1042693672@sss.pgh.pa.us> +User-Agent: Mutt/1.4i +Organization: Frobozzco International +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/137 +X-Sequence-Number: 784 + +Tom Lane wrote: +> Kevin Brown writes: +> > Tom Lane wrote: +> >> ... Whether this is a bug or a feature depends on +> >> your point of view --- but there are folks out there who find it to be +> >> a life-saver. +> +> > Since it *does* depend on one's point of view, would it be possible to +> > have control over this implemented in a session-defined variable (with +> > the default in the GUC, of course)? +> +> I have no objection to doing that --- anyone care to contribute code to +> make it happen? (I think the trick would be to fold plain-JOIN jointree +> entries into FROM-list items in planner.c, somewhere near the code that +> hoists sub-SELECTs into the main join tree. But I haven't tried it, and +> have no time to in the near future.) + +I'm looking at the code now (the 7.2.3 code in particular, but I +suspect for this purpose the code is likely to be very similar to the +CVS tip), but it's all completely new to me and the developer +documentation isn't very revealing of the internals. The optimizer +code (I've been looking especially at make_jointree_rel() and +make_fromexpr_rel()) looks a bit tricky...it'll take me some time to +completely wrap my brain around it. Any pointers to revealing +documentation would be quite helpful! + + +-- +Kevin Brown kevin@sysexperts.com + +From pgsql-performance-owner@postgresql.org Thu Jan 16 07:29:55 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BBFF14766ED + for ; + Thu, 16 Jan 2003 07:29:49 -0500 (EST) +Received: from lakemtao02.cox.net (lakemtao02.cox.net [68.1.17.243]) + by postgresql.org (Postfix) with ESMTP id C06AE4766AB + for ; + Thu, 16 Jan 2003 07:29:46 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao02.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030116122948.ITVZ6744.lakemtao02.cox.net@[192.168.1.1]> + for ; + Thu, 16 Jan 2003 07:29:48 -0500 +Subject: Re: 7.3.1 New install, large queries are slow +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C02@pos_pdc.posportal.com> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C02@pos_pdc.posportal.com> +Content-Type: text/plain +Organization: +Message-Id: <1042720183.892.18.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 16 Jan 2003 06:29:43 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/139 +X-Sequence-Number: 786 + +On Thu, 2003-01-16 at 03:03, Roman Fail wrote: +> *********************** +> > Josh Berkus wrote: +> > Hey, Roman, how many records in BatchDetail, anyway? +> +> 23 million. + +What are the indexes on batchdetail? + +There's one on batchid and a seperate one on tranamount? + +If so, what about dropping them and create a single multi-segment +index on "batchid, tranamount". (A constraint can then enforce +uniqueness on batchid. + +> *********************** +> > Stephan Szabo wrote: +> > What does vacuum verbose batchdetail give you (it'll give an idea of pages anyway) +> +> trans=# VACUUM VERBOSE batchdetail; +> INFO: --Relation public.batchdetail-- +> INFO: Pages 1669047: Changed 0, Empty 0; Tup 23316674: Vac 0, Keep 0, UnUsed 0. +> Total CPU 85.36s/9.38u sec elapsed 253.38 sec. +> INFO: --Relation pg_toast.pg_toast_8604247-- +> INFO: Pages 0: Changed 0, Empty 0; Tup 0: Vac 0, Keep 0, UnUsed 0. +> Total CPU 0.00s/0.00u sec elapsed 0.00 sec. +> VACUUM +> trans=# +> +> *********************** +> At Stephan Szabo and Tom Lane's suggestion, I reorganized the query +> so the JOIN syntax was only used in the outer joins. This did not +> seem to help at all. Of note: during this query 'sar -b' showed a +> consistent 6000 blocks read/sec, CPU was about 2%. +> +> EXPLAIN ANALYZE +> SELECT b.batchdate, d.batchdetailid, t.bankno, d.trandate, d.tranamount, +> d.submitinterchange, d.authamount, d.authno, d.cardtypeid, d.mcccode, +> m.name AS merchantname, c.cardtype, m.merchid, +> p1.localtaxamount, p1.productidentifier, dr.avsresponse, +> cr.checkoutdate, cr.noshowindicator, ck.checkingacctno, +> ck.abaroutingno, ck.checkno +> FROM tranheader t, batchheader b, merchants m, cardtype c, batchdetail d +> LEFT JOIN purc1 p1 on p1.batchdetailid=d.batchdetailid +> LEFT JOIN direct dr ON dr.batchdetailid = d.batchdetailid +> LEFT JOIN carrental cr ON cr.batchdetailid = d.batchdetailid +> LEFT JOIN checks ck ON ck.batchdetailid = d.batchdetailid +> WHERE t.tranheaderid=b.tranheaderid +> AND m.merchantid=b.merchantid +> AND d.batchid=b.batchid +> AND c.cardtypeid=d.cardtypeid +> AND t.clientid = 6 +> AND d.tranamount BETWEEN 500.0 AND 700.0 +> AND b.batchdate > '2002-12-15' +> AND m.merchid = '701252267' +> ORDER BY b.batchdate DESC +> LIMIT 50 +> Limit (cost=1789105.21..1789105.22 rows=1 width=285) (actual time=1222029.59..1222029.61 rows=5 loops=1) +> -> Sort (cost=1789105.21..1789105.22 rows=1 width=285) (actual time=1222029.58..1222029.59 rows=5 loops=1) +> Sort Key: b.batchdate +> -> Nested Loop (cost=1787171.22..1789105.20 rows=1 width=285) (actual time=1221815.14..1222019.46 rows=5 loops=1) +> Join Filter: ("inner".tranheaderid = "outer".tranheaderid) +> -> Nested Loop (cost=1787171.22..1789026.02 rows=1 width=269) (actual time=1221809.33..1221978.62 rows=5 loops=1) +> Join Filter: ("inner".cardtypeid = "outer".cardtypeid) +> -> Merge Join (cost=1787171.22..1789024.79 rows=1 width=255) (actual time=1221802.47..1221971.48 rows=5 loops=1) +> Merge Cond: ("outer".batchid = "inner".batchid) +> -> Sort (cost=476.17..476.18 rows=4 width=102) (actual time=678.05..678.07 rows=17 loops=1) +> Sort Key: b.batchid +> -> Nested Loop (cost=0.00..476.14 rows=4 width=102) (actual time=161.62..677.95 rows=17 loops=1) +> -> Index Scan using merchants_ix_merchid_idx on merchants m (cost=0.00..5.65 rows=1 width=78) (actual time=13.87..13.88 rows=1 loops=1) +> Index Cond: (merchid = '701252267'::character varying) +> -> Index Scan using batchheader_ix_merchantid_idx on batchheader b (cost=0.00..470.30 rows=15 width=24) (actual time=147.72..663.94 rows=17 loops=1) +> Index Cond: ("outer".merchantid = b.merchantid) +> Filter: (batchdate > '2002-12-15 00:00:00'::timestamp without time zone) +> -> Sort (cost=1786695.05..1787621.82 rows=370710 width=153) (actual time=1220080.34..1220722.19 rows=368681 loops=1) +> Sort Key: d.batchid +> -> Merge Join (cost=1704191.25..1713674.49 rows=370710 width=153) (actual time=1200184.91..1213352.77 rows=370307 loops=1) +> Merge Cond: ("outer".batchdetailid = "inner".batchdetailid) +> -> Merge Join (cost=1704085.28..1712678.33 rows=370710 width=115) (actual time=1199705.71..1210336.37 rows=370307 loops=1) +> Merge Cond: ("outer".batchdetailid = "inner".batchdetailid) +> -> Merge Join (cost=1704085.27..1711751.54 rows=370710 width=98) (actual time=1199705.65..1208122.73 rows=370307 loops=1) +> Merge Cond: ("outer".batchdetailid = "inner".batchdetailid) +> -> Merge Join (cost=1704085.26..1710824.75 rows=370710 width=89) (actual time=1199705.55..1205977.76 rows=370307 loops=1) +> Merge Cond: ("outer".batchdetailid = "inner".batchdetailid) +> -> Sort (cost=1543119.01..1544045.79 rows=370710 width=70) (actual time=1181172.79..1181902.77 rows=370307 loops=1) +> Sort Key: d.batchdetailid +> -> Index Scan using batchdetail_ix_tranamount_idx on batchdetail d (cost=0.00..1489103.46 rows=370710 width=70) (actual time=14.45..1176074.90 rows=370307 loops=1) +> Index Cond: ((tranamount >= 500.0) AND (tranamount <= 700.0)) +> -> Sort (cost=160966.25..163319.59 rows=941335 width=19) (actual time=18532.70..20074.09 rows=938770 loops=1) +> Sort Key: p1.batchdetailid +> -> Seq Scan on purc1 p1 (cost=0.00..44285.35 rows=941335 width=19) (actual time=9.44..9119.83 rows=938770 loops=1) +> -> Sort (cost=0.01..0.02 rows=1 width=9) (actual time=0.08..0.08 rows=0 loops=1) +> Sort Key: dr.batchdetailid +> -> Seq Scan on direct dr (cost=0.00..0.00 rows=1 width=9) (actual time=0.01..0.01 rows=0 loops=1) +> -> Sort (cost=0.01..0.02 rows=1 width=17) (actual time=0.04..0.04 rows=0 loops=1) +> Sort Key: cr.batchdetailid +> -> Seq Scan on carrental cr (cost=0.00..0.00 rows=1 width=17) (actual time=0.00..0.00 rows=0 loops=1) +> -> Sort (cost=105.97..109.13 rows=1267 width=38) (actual time=479.17..480.74 rows=1267 loops=1) +> Sort Key: ck.batchdetailid +> -> Seq Scan on checks ck (cost=0.00..40.67 rows=1267 width=38) (actual time=447.88..475.60 rows=1267 loops=1) +> -> Seq Scan on cardtype c (cost=0.00..1.10 rows=10 width=14) (actual time=1.37..1.39 rows=10 loops=5) +> -> Seq Scan on tranheader t (cost=0.00..55.15 rows=1923 width=16) (actual time=0.01..5.14 rows=1923 loops=5) +> Filter: (clientid = 6) +> Total runtime: 1222157.28 msec +> +> *********************** +> Just to see what would happen, I executed: +> ALTER TABLE batchdetail ALTER COLUMN tranamount SET STATISTICS 1000; +> ANALYZE; +> It seemed to hurt performance if anything. But the EXPLAIN estimate +> for rows was much closer to the real value than it was previously. +> +> *********************** +> It seems to me that the big, big isolated problem is the index scan on +> batchdetail.tranamount. During this small query, 'sar -b' showed +> consistent 90,000 block reads/sec. (contrast with only 6,000 with +> larger query index scan). 'top' shows the CPU is at 20% user, 30% +> system the whole time (contrast with 2% total in larger query above). +> This results here still seem pretty bad (although not as bad as +> above), but I still don't know what is the bottleneck. And the +> strange sar stats are confusing me. +> +> EXPLAIN ANALYZE SELECT * FROM batchdetail WHERE tranamount BETWEEN 300 AND 499; +> Seq Scan on batchdetail (cost=0.00..2018797.11 rows=783291 width=440) (actual time=45.66..283926.58 rows=783687 loops=1) +> Filter: ((tranamount >= 300::numeric) AND (tranamount <= 499::numeric)) +> Total runtime: 285032.47 msec +> +> +> *********************** +> > Stephan Szabo wrote: +> > As a followup, if you do set enable_indexscan=off; +> > before running the explain analyze, what does that give you? +> +> Now this is very interesting: 'sar -b' shows about 95,000 block +> reads/sec; CPU is at 20% user 30% system, vmstat shows no swapping, +> query takes only 5 minutes to execute (which is one-quarter of the +> time WITH the index scan!!!!). Obviously the execution plan is pretty +> different on this one (query is identical the larger one above). +> +> EXPLAIN ANALYZE +> SELECT b.batchdate, d.batchdetailid, t.bankno, d.trandate, d.tranamount, +> d.submitinterchange, d.authamount, d.authno, d.cardtypeid, d.mcccode, +> m.name AS merchantname, c.cardtype, m.merchid, +> p1.localtaxamount, p1.productidentifier, dr.avsresponse, +> cr.checkoutdate, cr.noshowindicator, ck.checkingacctno, +> ck.abaroutingno, ck.checkno +> FROM tranheader t, batchheader b, merchants m, cardtype c, +> batchdetail d +> LEFT JOIN purc1 p1 on p1.batchdetailid=d.batchdetailid +> LEFT JOIN direct dr ON dr.batchdetailid = d.batchdetailid +> LEFT JOIN carrental cr ON cr.batchdetailid = d.batchdetailid +> LEFT JOIN checks ck ON ck.batchdetailid = d.batchdetailid +> WHERE t.tranheaderid=b.tranheaderid +> AND m.merchantid=b.merchantid +> AND d.batchid=b.batchid +> AND c.cardtypeid=d.cardtypeid +> AND t.clientid = 6 +> AND d.tranamount BETWEEN 500.0 AND 700.0 +> AND b.batchdate > '2002-12-15' +> AND m.merchid = '701252267' +> ORDER BY b.batchdate DESC +> LIMIT 50 +> Limit (cost=2321460.56..2321460.57 rows=1 width=285) (actual time=308194.57..308194.59 rows=5 loops=1) +> -> Sort (cost=2321460.56..2321460.57 rows=1 width=285) (actual time=308194.57..308194.58 rows=5 loops=1) +> Sort Key: b.batchdate +> -> Nested Loop (cost=2319526.57..2321460.55 rows=1 width=285) (actual time=307988.56..308194.46 rows=5 loops=1) +> Join Filter: ("inner".tranheaderid = "outer".tranheaderid) +> -> Nested Loop (cost=2319526.57..2321381.37 rows=1 width=269) (actual time=307982.80..308153.22 rows=5 loops=1) +> Join Filter: ("inner".cardtypeid = "outer".cardtypeid) +> -> Merge Join (cost=2319526.57..2321380.14 rows=1 width=255) (actual time=307982.69..308152.82 rows=5 loops=1) +> Merge Cond: ("outer".batchid = "inner".batchid) +> -> Sort (cost=2316388.70..2317315.47 rows=370710 width=153) (actual time=305976.74..306622.88 rows=368681 loops=1) +> Sort Key: d.batchid +> -> Merge Join (cost=2233884.90..2243368.15 rows=370710 width=153) (actual time=286452.12..299485.43 rows=370307 loops=1) +> Merge Cond: ("outer".batchdetailid = "inner".batchdetailid) +> -> Merge Join (cost=2233778.93..2242371.98 rows=370710 width=115) (actual time=286428.77..296939.66 rows=370307 loops=1) +> Merge Cond: ("outer".batchdetailid = "inner".batchdetailid) +> -> Merge Join (cost=2233778.92..2241445.19 rows=370710 width=98) (actual time=286428.72..294750.01 rows=370307 loops=1) +> Merge Cond: ("outer".batchdetailid = "inner".batchdetailid) +> -> Merge Join (cost=2233778.91..2240518.40 rows=370710 width=89) (actual time=286428.60..292606.56 rows=370307 loops=1) +> Merge Cond: ("outer".batchdetailid = "inner".batchdetailid) +> -> Sort (cost=2072812.66..2073739.44 rows=370710 width=70) (actual time=269738.34..270470.83 rows=370307 loops=1) +> Sort Key: d.batchdetailid +> -> Seq Scan on batchdetail d (cost=0.00..2018797.11 rows=370710 width=70) (actual time=41.66..266568.83 rows=370307 loops=1) +> Filter: ((tranamount >= 500.0) AND (tranamount <= 700.0)) +> -> Sort (cost=160966.25..163319.59 rows=941335 width=19) (actual time=16690.20..18202.65 rows=938770 loops=1) +> Sort Key: p1.batchdetailid +> -> Seq Scan on purc1 p1 (cost=0.00..44285.35 rows=941335 width=19) (actual time=6.88..7779.31 rows=938770 loops=1) +> -> Sort (cost=0.01..0.02 rows=1 width=9) (actual time=0.10..0.10 rows=0 loops=1) +> Sort Key: dr.batchdetailid +> -> Seq Scan on direct dr (cost=0.00..0.00 rows=1 width=9) (actual time=0.00..0.00 rows=0 loops=1) +> -> Sort (cost=0.01..0.02 rows=1 width=17) (actual time=0.03..0.03 rows=0 loops=1) +> Sort Key: cr.batchdetailid +> -> Seq Scan on carrental cr (cost=0.00..0.00 rows=1 width=17) (actual time=0.00..0.00 rows=0 loops=1) +> -> Sort (cost=105.97..109.13 rows=1267 width=38) (actual time=23.32..24.89 rows=1267 loops=1) +> Sort Key: ck.batchdetailid +> -> Seq Scan on checks ck (cost=0.00..40.67 rows=1267 width=38) (actual time=6.51..19.59 rows=1267 loops=1) +> -> Sort (cost=3137.87..3137.88 rows=4 width=102) (actual time=954.18..954.20 rows=19 loops=1) +> Sort Key: b.batchid +> -> Nested Loop (cost=0.00..3137.84 rows=4 width=102) (actual time=236.26..954.04 rows=17 loops=1) +> -> Seq Scan on merchants m (cost=0.00..2667.35 rows=1 width=78) (actual time=2.48..227.71 rows=1 loops=1) +> Filter: (merchid = '701252267'::character varying) +> -> Index Scan using batchheader_ix_merchantid_idx on batchheader b (cost=0.00..470.30 rows=15 width=24) (actual time=233.75..726.22 rows=17 loops=1) +> Index Cond: ("outer".merchantid = b.merchantid) +> Filter: (batchdate > '2002-12-15 00:00:00'::timestamp without time zone) +> -> Seq Scan on cardtype c (cost=0.00..1.10 rows=10 width=14) (actual time=0.02..0.04 rows=10 loops=5) +> -> Seq Scan on tranheader t (cost=0.00..55.15 rows=1923 width=16) (actual time=0.01..5.21 rows=1923 loops=5) +> Filter: (clientid = 6) +> Total runtime: 308323.60 msec +> +> *********************** +> I hope we can come up with something soon.....it seems this index +> scan is a big part of the problem. I'm still really curious why the +> disk reads are so few with the index scan. Let's hope I can get it +> near the 3 second time for MSSQL by Friday! + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 06:05:14 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 313494766DE + for ; + Thu, 16 Jan 2003 06:05:11 -0500 (EST) +Received: from localhost.localdomain (sein.itera.ee [194.126.109.126]) + by postgresql.org (Postfix) with ESMTP id E0997476A10 + for ; + Thu, 16 Jan 2003 06:03:22 -0500 (EST) +Received: (from hannu@localhost) + by localhost.localdomain (8.11.6/8.11.6) id h0GCsxq02689; + Thu, 16 Jan 2003 12:54:59 GMT +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: 7.3.1 New install, large queries are slow +From: Hannu Krosing +To: Stephan Szabo +Cc: Roman Fail , josh@agliodbs.com, + "pgsql-performance@postgresql.org" +In-Reply-To: <20030115192815.T98147-100000@megazone23.bigpanda.com> +References: <20030115192815.T98147-100000@megazone23.bigpanda.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1042721698.2502.109.camel@huli> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 16 Jan 2003 12:54:58 +0000 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/138 +X-Sequence-Number: 785 + +On Thu, 2003-01-16 at 03:40, Stephan Szabo wrote: +> > So here's the query, and another EXPLAIN ANALYZE to go with it +> > (executed after all setting changes). The same result columns and +> > JOINS are performed all day with variations on the WHERE clause; other +> > possible search columns are the ones that are indexed (see below). +> > The 4 tables that use LEFT JOIN only sometimes have matching records, +> > hence the OUTER join. +> > +> > EXPLAIN ANALYZE +> > SELECT b.batchdate, d.batchdetailid, t.bankno, d.trandate, d.tranamount, +> > d.submitinterchange, d.authamount, d.authno, d.cardtypeid, d.mcccode, +> > m.name AS merchantname, c.cardtype, m.merchid, +> > p1.localtaxamount, p1.productidentifier, dr.avsresponse, +> > cr.checkoutdate, cr.noshowindicator, ck.checkingacctno, +> > ck.abaroutingno, ck.checkno +> > FROM tranheader t +> > INNER JOIN batchheader b ON t.tranheaderid = b.tranheaderid +> > INNER JOIN merchants m ON m.merchantid = b.merchantid +> > INNER JOIN batchdetail d ON d.batchid = b.batchid +> > INNER JOIN cardtype c ON d.cardtypeid = c.cardtypeid +> > LEFT JOIN purc1 p1 ON p1.batchdetailid = d.batchdetailid +> > LEFT JOIN direct dr ON dr.batchdetailid = d.batchdetailid +> > LEFT JOIN carrental cr ON cr.batchdetailid = d.batchdetailid +> > LEFT JOIN checks ck ON ck.batchdetailid = d.batchdetailid +> > WHERE t.clientid = 6 +> > AND d.tranamount BETWEEN 500.0 AND 700.0 + +How much of data in d has tranamount BETWEEN 500.0 AND 700.0 ? + +Do you have an index on d.tranamount ? + +> > AND b.batchdate > '2002-12-15' + +again - how much of b.batchdate > '2002-12-15' ? + +is there an index + +> > AND m.merchid = '701252267' + +ditto + +> > ORDER BY b.batchdate DESC +> > LIMIT 50 + +these two together make me think that perhaps + +b.batchdate between '2003-12-12' and '2002-12-15' + +could be better at making the optimiser see that reverse index scan on +b.batchdate would be the way to go. + +> Well, you might get a little help by replace the from with + +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Thu Jan 16 08:17:37 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 53B644766F0 + for ; + Thu, 16 Jan 2003 08:17:35 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id CCB854766BC + for ; + Thu, 16 Jan 2003 08:17:34 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18Z9tq-0006BP-00 + for ; Thu, 16 Jan 2003 08:17:38 -0500 +Date: Thu, 16 Jan 2003 08:17:38 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +Message-ID: <20030116081738.B22344@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com>; + from rfail@posportal.com on Wed, Jan 15, 2003 at 03:30:55PM -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/140 +X-Sequence-Number: 787 + +On Wed, Jan 15, 2003 at 03:30:55PM -0800, Roman Fail wrote: +> Thanks to everyone for the quick replies! I'm sure that my lack of skill with SQL queries is the main problem. What's strange to me is how MSSQL takes my bad queries and makes them look good anyway. It must have a real smart planner. +> Andrew Sullivan wrote: +> >First, the performance of foreign keys is flat-out awful in Postgres. +> >I suggest avoiding them if you can. +> +> I don't have any problem getting rid of FKs, especially if it might +> actually help performance. The nightly data import is well-defined + +Sorry, I think I sent this too quickly. FKs make no difference to +SELECT performance, so if you're not doing updates and the like at +the same time as the SELECTs, there's no advantage. So you should +leave the FKs in place. + +> I think this is the most likely problem. I've read through Chapter +> 10 of the 7.3 docs, but I still don't feel like I know what would +> be a good order. How do you learn this stuff anyway? Trial and +> error? + +Sorry, but yes. + +A +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 08:45:03 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E716847621F + for ; + Thu, 16 Jan 2003 08:44:59 -0500 (EST) +Received: from web21105.mail.yahoo.com (web21105.mail.yahoo.com + [216.136.227.107]) + by postgresql.org (Postfix) with SMTP id 574DC47621A + for ; + Thu, 16 Jan 2003 08:44:59 -0500 (EST) +Message-ID: <20030116134502.36697.qmail@web21105.mail.yahoo.com> +Received: from [140.247.91.110] by web21105.mail.yahoo.com via HTTP; + Thu, 16 Jan 2003 05:45:02 PST +Date: Thu, 16 Jan 2003 05:45:02 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: Re: Sun vs. Mac - gprof output +To: pgsql-performance@postgresql.org +In-Reply-To: <12202.1042697508@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/141 +X-Sequence-Number: 788 + +> It'd not be surprising for libreadline to suck a good deal of the +> runtime of psql ... but I don't believe the backend will call it at all. +> So, either this trace is erroneous, or you profiled the wrong process +> (client instead of backend), or there's something truly weird going on. + +You're right, I got the client, here's the backend: + + % cumulative self self total + time seconds seconds calls ms/call ms/call name + 23.4 125.31 125.31 internal_mcount [13] + 21.2 239.07 113.76 79296415 0.00 0.00 ExecMakeFunctionResult + [14] + 7.8 280.68 41.61 98971658 0.00 0.00 AllocSetReset [23] + 6.8 317.13 36.45 193735603 0.00 0.00 ExecEvalVar [18] + 5.2 345.21 28.08 280731963 0.00 0.00 ExecEvalExpr [15] + 2.7 359.93 14.72 38140599 0.00 0.00 nocachegetattr [35] + 2.7 374.28 14.35 320207 0.04 0.04 _read [38] + 2.2 385.97 11.69 78969393 0.00 0.00 ExecQual [34] + 2.1 397.46 11.49 79296415 0.00 0.00 ExecEvalFuncArgs [42] + 1.4 404.71 7.25 _mcount (6219) + 1.3 411.73 7.02 11293115 0.00 0.00 heapgettup [31] + 1.2 418.34 6.61 98975017 0.00 0.00 ExecClearTuple [43] + 1.0 423.93 5.59 98971592 0.00 0.00 ExecStoreTuple [33] + 0.9 428.87 4.94 197952332 0.00 0.00 MemoryContextSwitchTo +[53] + 0.9 433.53 4.66 7612547 0.00 0.00 heap_formtuple [39] + 0.8 437.96 4.43 7609318 0.00 0.01 ExecScanHashBucket + [17] + 0.8 442.34 4.38 8 547.50 547.50 .rem [55] + 0.8 446.64 4.30 79296261 0.00 0.00 ExecEvalOper [56] + + +I'm not sure what to make of this. + +Thanks, + +-X + + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Thu Jan 16 08:54:44 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A6028476819 + for ; + Thu, 16 Jan 2003 08:54:37 -0500 (EST) +Received: from web21106.mail.yahoo.com (web21106.mail.yahoo.com + [216.136.227.108]) + by postgresql.org (Postfix) with SMTP id 4E0A7476B85 + for ; + Thu, 16 Jan 2003 08:51:37 -0500 (EST) +Message-ID: <20030116135140.32097.qmail@web21106.mail.yahoo.com> +Received: from [140.247.91.110] by web21106.mail.yahoo.com via HTTP; + Thu, 16 Jan 2003 05:51:40 PST +Date: Thu, 16 Jan 2003 05:51:40 -0800 (PST) +From: CaptainX0r +Reply-To: captainx0r@yahoo.com +Subject: schema/db design wrt performance +To: pgsql-performance@postgresql.org +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/142 +X-Sequence-Number: 789 + +All, + +I just noted in another thread that use of foreign keys in postgres +significantly hinders performance. I'm wondering what other aspects we should +take into consideration in the design of our database. We're coming from +Sybase and trying to design a more encompassing, modular, generic database that +won't take a serious performance hit under postgres. + +Thanks, + +-X + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Thu Jan 16 09:08:27 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6FE22476757 + for ; + Thu, 16 Jan 2003 09:08:25 -0500 (EST) +Received: from mx5.claxson.com (unknown [200.32.96.144]) + by postgresql.org (Postfix) with ESMTP id 8F721476BF9 + for ; + Thu, 16 Jan 2003 09:07:22 -0500 (EST) +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="us-ascii" +Content-Transfer-Encoding: quoted-printable +Subject: Re: schema/db design wrt performance +Date: Thu, 16 Jan 2003 11:07:25 -0300 +Message-ID: + +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [PERFORM] schema/db design wrt performance +Thread-Index: AcK9ZtfL0RIwYBa3QHSI7Zs7EHCr+QAAOQxg +From: "Fernando Papa" +To: , +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/143 +X-Sequence-Number: 790 + +I think FK on every database (oracle and MSSQL too) may hit performance, +but only in DML (insert/update/delete). These are tradeoffs... +referencial integrity vs. problems with batchload for example. +My Oracle experience say when I need to do batchload, I disable +constraints and then apply and work over exceptions. +If you don't make referencial integrity on database maybe you need to do +it on you application... and I think will be very painfull. + +-- +Fernando O. Papa +DBA +=20 + +> -----Mensaje original----- +> De: CaptainX0r [mailto:captainx0r@yahoo.com]=20 +> Enviado el: jueves, 16 de enero de 2003 10:52 +> Para: pgsql-performance@postgresql.org +> Asunto: [PERFORM] schema/db design wrt performance +>=20 +>=20 +> All, +>=20 +> I just noted in another thread that use of foreign keys in=20 +> postgres significantly hinders performance. I'm wondering=20 +> what other aspects we should take into consideration in the=20 +> design of our database. We're coming from Sybase and trying=20 +> to design a more encompassing, modular, generic database that=20 +> won't take a serious performance hit under postgres. +>=20 +> Thanks, +>=20 +> -X +>=20 +> __________________________________________________ +> Do you Yahoo!? +> Yahoo! Mail Plus - Powerful. Affordable. Sign up now.=20 +http://mailplus.yahoo.com + +---------------------------(end of broadcast)--------------------------- +TIP 5: Have you checked our extensive FAQ? + +http://www.postgresql.org/users-lounge/docs/faq.html + +From pgsql-performance-owner@postgresql.org Thu Jan 16 09:20:04 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 859F1475FD5 + for ; + Thu, 16 Jan 2003 09:20:02 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 07D23475CEE + for ; + Thu, 16 Jan 2003 09:20:02 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18ZAsH-000797-00 + for ; Thu, 16 Jan 2003 09:20:05 -0500 +Date: Thu, 16 Jan 2003 09:20:05 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: schema/db design wrt performance +Message-ID: <20030116092005.C22344@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <20030116135140.32097.qmail@web21106.mail.yahoo.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <20030116135140.32097.qmail@web21106.mail.yahoo.com>; + from captainx0r@yahoo.com on Thu, Jan 16, 2003 at 05:51:40AM -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/144 +X-Sequence-Number: 791 + +On Thu, Jan 16, 2003 at 05:51:40AM -0800, CaptainX0r wrote: +> All, +> +> I just noted in another thread that use of foreign keys in postgres +> significantly hinders performance. I'm wondering what other + +Since I think I'm the one responsible for this, I'd better say +something clearer for the record. + +The foreign keys implementation in PostgreSQL essentially uses SELECT +. . . FOR UPDATE to ensure that referenced data doesn't go away while a +referencing datum is being inserted or altered. + +The problem with this is that frequently-referenced data are +therefore effectively locked during the operation. Other writers +will block on the locked data until the first writer finishes. + +So, for instance, consider two artificial-example tables: + +create table account (acct_id serial primary key); + +create table acct_activity (acct_id int references +account(acct_id), trans_on timestamp, val numeric(12,2)); + +If a user has multiple connections and charges things to the same +account in more than one connection at the same time, the +transactions will have to be processed, effectively, in series: each +one will have to wait for another to commit in order to complete. + +This is just a performance bottleneck. But it gets worse. Suppose +the account table is like this: + +create table account (acct_id serial primary key, con_id int +references contact(con_id)); + +create table contact (con_id serial primary key, name text, address1 +text [. . .]); + +Now, if another transaction is busy trying to delete a contact at the +same time the account table is being updated to reflect, say, a new +contact, you run the risk of deadlock. + +The FK support in PostgreSQL is therefore mostly useful for +low-volume applications. It can be made to work under heavier load +if you use it very carefully and program your application for it. +But I suggest avoiding it for heavy-duty use if you really can. + +> take into consideration in the design of our database. We're +> coming from Sybase and trying to design a more encompassing, +> modular, generic database that won't take a serious performance hit +> under postgres. + +Avoid NOT IN. This is difficult, because the workaround in Postgres +(NOT EXISTS) is frequently lousy on other systems. Apparently there +is some fix for this contemplated for 7.4, but I've been really busy +lately, so I haven't been following -hackers. Someone else can +probably say something more useful about it. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 09:23:29 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id DFFDD475FD5 + for ; + Thu, 16 Jan 2003 09:23:27 -0500 (EST) +Received: from jester.senspire.com + (CPE00508b028d7d-CM00803785c5e0.cpe.net.cable.rogers.com + [24.103.51.175]) + by postgresql.org (Postfix) with ESMTP id 31CCB475CEE + for ; + Thu, 16 Jan 2003 09:23:27 -0500 (EST) +Received: from [127.0.0.1] (localhost [127.0.0.1]) + by jester.senspire.com (8.12.6/8.12.6) with ESMTP id h0GENXfe033690; + Thu, 16 Jan 2003 09:23:33 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: 7.3.1 New install, large queries are slow +From: Rod Taylor +To: Roman Fail +Cc: PgSQL Performance ML +In-Reply-To: <1042720183.892.18.camel@haggis> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C02@pos_pdc.posportal.com> + <1042720183.892.18.camel@haggis> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-h6okXiXg4P76ZXXA2EZx" +Organization: +Message-Id: <1042727012.82534.50.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 16 Jan 2003 09:23:32 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/145 +X-Sequence-Number: 792 + +--=-h6okXiXg4P76ZXXA2EZx +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +On Thu, 2003-01-16 at 07:29, Ron Johnson wrote: +> On Thu, 2003-01-16 at 03:03, Roman Fail wrote: +> > *********************** +> > > Josh Berkus wrote: +> > > Hey, Roman, how many records in BatchDetail, anyway? +> >=20 +> > 23 million. +>=20 +> What are the indexes on batchdetail? +>=20 +> There's one on batchid and a seperate one on tranamount? +>=20 +> If so, what about dropping them and create a single multi-segment +> index on "batchid, tranamount". (A constraint can then enforce +> uniqueness on batchid. + +Thats a good step. Once done, CLUSTER by that index -- might buy 10 to +20% extra. + + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-h6okXiXg4P76ZXXA2EZx +Content-Type: application/pgp-signature; name=signature.asc +Content-Description: This is a digitally signed message part + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (FreeBSD) + +iD8DBQA+JsBj6DETLow6vwwRAgHAAJ9Uxj4BQ/tMQooJ0l7z0/PjV+EAhACfZT5U +OR5Ig7+qxeprpC93ckBJX4s= +=MKW8 +-----END PGP SIGNATURE----- + +--=-h6okXiXg4P76ZXXA2EZx-- + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 09:35:29 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 70F6E476742 + for ; + Thu, 16 Jan 2003 09:35:28 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 2F5A1476809 + for ; + Thu, 16 Jan 2003 09:34:35 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030116143439.KAGI8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Thu, 16 Jan 2003 09:34:39 -0500 +Subject: Re: schema/db design wrt performance +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <20030116092005.C22344@mail.libertyrms.com> +References: <20030116135140.32097.qmail@web21106.mail.yahoo.com> + <20030116092005.C22344@mail.libertyrms.com> +Content-Type: text/plain +Organization: +Message-Id: <1042727678.892.31.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 16 Jan 2003 08:34:38 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/146 +X-Sequence-Number: 793 + +On Thu, 2003-01-16 at 08:20, Andrew Sullivan wrote: +> On Thu, Jan 16, 2003 at 05:51:40AM -0800, CaptainX0r wrote: +> > All, +> > +> > I just noted in another thread that use of foreign keys in postgres +> > significantly hinders performance. I'm wondering what other +> +> Since I think I'm the one responsible for this, I'd better say +> something clearer for the record. +> +> The foreign keys implementation in PostgreSQL essentially uses SELECT +> . . . FOR UPDATE to ensure that referenced data doesn't go away while a +> referencing datum is being inserted or altered. +> +> The problem with this is that frequently-referenced data are +> therefore effectively locked during the operation. Other writers +> will block on the locked data until the first writer finishes. +> +> So, for instance, consider two artificial-example tables: +> +> create table account (acct_id serial primary key); +> +> create table acct_activity (acct_id int references +> account(acct_id), trans_on timestamp, val numeric(12,2)); +> +> If a user has multiple connections and charges things to the same +> account in more than one connection at the same time, the +> transactions will have to be processed, effectively, in series: each +> one will have to wait for another to commit in order to complete. + +This is true even though the default transaction mode is +READ COMMITTED? + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 10:13:43 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9CD794761AF + for ; + Thu, 16 Jan 2003 10:13:41 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id ABC7D475CEE + for ; + Thu, 16 Jan 2003 10:13:40 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0GFDc5u014737; + Thu, 16 Jan 2003 10:13:38 -0500 (EST) +To: "Roman Fail" +Cc: "Josh Berkus" , + sszabo@megazone23.bigpanda.com, pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C02@pos_pdc.posportal.com> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C02@pos_pdc.posportal.com> +Comments: In-reply-to "Roman Fail" + message dated "Thu, 16 Jan 2003 01:03:43 -0800" +Date: Thu, 16 Jan 2003 10:13:37 -0500 +Message-ID: <14736.1042730017@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/147 +X-Sequence-Number: 794 + +"Roman Fail" writes: +> SELECT ... +> FROM tranheader t, batchheader b, merchants m, cardtype c, (batchdetail d +> LEFT JOIN purc1 p1 on p1.batchdetailid=d.batchdetailid +> LEFT JOIN direct dr ON dr.batchdetailid = d.batchdetailid +> LEFT JOIN carrental cr ON cr.batchdetailid = d.batchdetailid +> LEFT JOIN checks ck ON ck.batchdetailid = d.batchdetailid) +> WHERE t.tranheaderid=b.tranheaderid +> AND m.merchantid=b.merchantid +> AND d.batchid=b.batchid +> AND c.cardtypeid=d.cardtypeid +> AND t.clientid = 6 +> AND d.tranamount BETWEEN 500.0 AND 700.0 +> AND b.batchdate > '2002-12-15' +> AND m.merchid = '701252267' + +No no no ... this is even worse than before. Your big tables are +batchdetail (d) and purc1 (p1). What you've got to do is arrange the +computation so that those are trimmed to just the interesting records as +soon as possible. The constraint on d.tranamount helps, but after that +you proceed to join d to p1 *first*, before any of the other constraints +can be applied. That's a huge join that you then proceed to throw away +most of, as shown by the row counts in the EXPLAIN output. + +Note the parentheses I added above to show how the system interprets +your FROM clause. Since dr,cr,ck are contributing nothing to +elimination of records, you really want them joined last, not first. + +What would probably work better is + +SELECT ... +FROM + (SELECT ... + FROM tranheader t, batchheader b, merchants m, cardtype c, batchdetail d + WHERE t.tranheaderid=b.tranheaderid + AND m.merchantid=b.merchantid + AND d.batchid=b.batchid + AND c.cardtypeid=d.cardtypeid + AND t.clientid = 6 + AND d.tranamount BETWEEN 500.0 AND 700.0 + AND b.batchdate > '2002-12-15' + AND m.merchid = '701252267') ss + LEFT JOIN purc1 p1 on p1.batchdetailid=ss.batchdetailid + LEFT JOIN direct dr ON dr.batchdetailid = ss.batchdetailid + LEFT JOIN carrental cr ON cr.batchdetailid = ss.batchdetailid + LEFT JOIN checks ck ON ck.batchdetailid = ss.batchdetailid + +which lets the system get the useful restrictions applied before it has +to finish expanding out the star query. Since cardtype isn't +contributing any restrictions, you might think about moving it into the +LEFT JOIN series too (although I think the planner will choose to join +it last in the subselect, anyway). + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 16 10:39:33 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7C66E4766BC + for ; + Thu, 16 Jan 2003 10:39:30 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 421144766BA + for ; + Thu, 16 Jan 2003 10:39:29 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18ZC7B-0008Vq-00 + for ; Thu, 16 Jan 2003 10:39:33 -0500 +Date: Thu, 16 Jan 2003 10:39:33 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: schema/db design wrt performance +Message-ID: <20030116103933.B32288@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <20030116135140.32097.qmail@web21106.mail.yahoo.com> + <20030116092005.C22344@mail.libertyrms.com> + <1042727678.892.31.camel@haggis> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <1042727678.892.31.camel@haggis>; + from ron.l.johnson@cox.net on Thu, Jan 16, 2003 at 08:34:38AM + -0600 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/148 +X-Sequence-Number: 795 + +On Thu, Jan 16, 2003 at 08:34:38AM -0600, Ron Johnson wrote: +> On Thu, 2003-01-16 at 08:20, Andrew Sullivan wrote: + +> > If a user has multiple connections and charges things to the same +> > account in more than one connection at the same time, the +> > transactions will have to be processed, effectively, in series: each +> > one will have to wait for another to commit in order to complete. +> +> This is true even though the default transaction mode is +> READ COMMITTED? + +Yes. Remember, _both_ of these are doing SELECT. . .FOR UPDATE. +Which means they both try to lock the corresponding record. But they +can't _both_ lock the same record; that's what the lock prevents. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 10:46:31 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BFE3B47682B + for ; + Thu, 16 Jan 2003 10:46:30 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id A15A1476758 + for ; + Thu, 16 Jan 2003 10:46:18 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0GFkN5u015060; + Thu, 16 Jan 2003 10:46:23 -0500 (EST) +To: Kevin Brown +Cc: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: <20030116104025.GB29781@filer> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> + <11547.1042691700@sss.pgh.pa.us> <20030116044847.GA29781@filer> + <11770.1042693672@sss.pgh.pa.us> <20030116104025.GB29781@filer> +Comments: In-reply-to Kevin Brown + message dated "Thu, 16 Jan 2003 02:40:25 -0800" +Date: Thu, 16 Jan 2003 10:46:22 -0500 +Message-ID: <15059.1042731982@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/149 +X-Sequence-Number: 796 + +Kevin Brown writes: +> I'm looking at the code now (the 7.2.3 code in particular, but I +> suspect for this purpose the code is likely to be very similar to the +> CVS tip), but it's all completely new to me and the developer +> documentation isn't very revealing of the internals. The optimizer +> code (I've been looking especially at make_jointree_rel() and +> make_fromexpr_rel()) looks a bit tricky...it'll take me some time to +> completely wrap my brain around it. Any pointers to revealing +> documentation would be quite helpful! + +src/backend/optimizer/README is a good place to start. + +I'd recommend working with CVS tip; there is little point in doing any +nontrivial development in the 7.2 branch. You'd have to port it forward +anyway. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 16 10:50:05 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2DDE4475CEE + for ; + Thu, 16 Jan 2003 10:50:03 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 5503C4767C0 + for ; + Thu, 16 Jan 2003 10:50:00 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030116155005.KTXQ8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Thu, 16 Jan 2003 10:50:05 -0500 +Subject: Re: schema/db design wrt performance +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <20030116103933.B32288@mail.libertyrms.com> +References: <20030116135140.32097.qmail@web21106.mail.yahoo.com> + <20030116092005.C22344@mail.libertyrms.com> + <1042727678.892.31.camel@haggis> + <20030116103933.B32288@mail.libertyrms.com> +Content-Type: text/plain +Organization: +Message-Id: <1042732204.892.35.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 16 Jan 2003 09:50:04 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/150 +X-Sequence-Number: 797 + +On Thu, 2003-01-16 at 09:39, Andrew Sullivan wrote: +> On Thu, Jan 16, 2003 at 08:34:38AM -0600, Ron Johnson wrote: +> > On Thu, 2003-01-16 at 08:20, Andrew Sullivan wrote: +> +> > > If a user has multiple connections and charges things to the same +> > > account in more than one connection at the same time, the +> > > transactions will have to be processed, effectively, in series: each +> > > one will have to wait for another to commit in order to complete. +> > +> > This is true even though the default transaction mode is +> > READ COMMITTED? +> +> Yes. Remember, _both_ of these are doing SELECT. . .FOR UPDATE. +> Which means they both try to lock the corresponding record. But they +> can't _both_ lock the same record; that's what the lock prevents. + +Could BEFORE INSERT|UPDATE|DELETE triggers perform the same +functionality while touching only the desired records, thus +decreasing conflict? + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 10:53:16 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id DB7B34766BA + for ; + Thu, 16 Jan 2003 10:53:14 -0500 (EST) +Received: from clearmetrix.com (unknown [209.92.142.67]) + by postgresql.org (Postfix) with ESMTP id 35E77476632 + for ; + Thu, 16 Jan 2003 10:53:14 -0500 (EST) +Received: from clearmetrix.com (chw.muvpn.clearmetrix.com [172.16.1.3]) + by clearmetrix.com (8.11.6/linuxconf) with ESMTP id h0GFrCM02459; + Thu, 16 Jan 2003 10:53:12 -0500 +Message-ID: <3E26D564.1060209@clearmetrix.com> +Date: Thu, 16 Jan 2003 10:53:08 -0500 +From: "Charles H. Woloszynski" +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; + rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Tom Lane +Cc: Roman Fail , josh@agliodbs.com, + pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> + <11547.1042691700@sss.pgh.pa.us> +In-Reply-To: <11547.1042691700@sss.pgh.pa.us> +Content-Type: text/plain; charset=ISO-8859-1; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/151 +X-Sequence-Number: 798 + +I was surprised to hear that JOIN syntax constrained the planner. We +have a policy of using JOIN syntax to describe the table relationships +and where clauses to describe the selection process for our queries. It +was our understanding that the JOIN syntax was introduced to support +this approach, but not to contrain the planner. + +Is there any way to sell the planner to consider JOIN syntax as +equivalent to WHERE clauses and to not use them to force the planner +down a specific path? Can we get that added as an option (and then made +available to use JDBC folks as a URL parameter). It would make my team +very happy :-). + + +I think that making this an option will help all those migrating to +Postgres who did not expect that JOINs forced the planner down specific +plans. Is it possible/reasonable to add? + +Charlie + + +Tom Lane wrote: + +>"Roman Fail" writes: +> +> +>>Thanks to everyone for the quick replies! I'm sure that my lack of +>>skill with SQL queries is the main problem. What's strange to me is +>>how MSSQL takes my bad queries and makes them look good anyway. It +>>must have a real smart planner. +>> +>> +> +>I think more likely the issue is that your use of JOIN syntax is forcing +>Postgres into a bad plan. MSSQL probably doesn't assign any semantic +>significance to the use of "a JOIN b" syntax as opposed to "FROM a, b" +>syntax. Postgres does. Whether this is a bug or a feature depends on +>your point of view --- but there are folks out there who find it to be +>a life-saver. You can find some explanations at +>http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/explicit-joins.html +> +> +> +>>Is it pretty much universally accepted that I should drop all my +>>foreign keys? +>> +>> +> +>No. They don't have any effect on SELECT performance in Postgres. +>They will impact update speed, but that's not your complaint (at the +>moment). Don't throw away data integrity protection until you know +>you need to. +> +> regards, tom lane +> +>---------------------------(end of broadcast)--------------------------- +>TIP 4: Don't 'kill -9' the postmaster +> +> + +-- + + +Charles H. Woloszynski + +ClearMetrix, Inc. +115 Research Drive +Bethlehem, PA 18015 + +tel: 610-419-2210 x400 +fax: 240-371-3256 +web: www.clearmetrix.com + + + + + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 11:04:38 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 25C9847675C + for ; + Thu, 16 Jan 2003 11:04:36 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 82518476D75 + for ; + Thu, 16 Jan 2003 11:02:35 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 24504D606; Thu, 16 Jan 2003 08:02:40 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 1A04C5C02; Thu, 16 Jan 2003 08:02:40 -0800 (PST) +Date: Thu, 16 Jan 2003 08:02:40 -0800 (PST) +From: Stephan Szabo +To: Ron Johnson +Cc: PgSQL Performance ML +Subject: Re: schema/db design wrt performance +In-Reply-To: <1042732204.892.35.camel@haggis> +Message-ID: <20030116080132.A4962-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/152 +X-Sequence-Number: 799 + + +On 16 Jan 2003, Ron Johnson wrote: + +> On Thu, 2003-01-16 at 09:39, Andrew Sullivan wrote: +> > On Thu, Jan 16, 2003 at 08:34:38AM -0600, Ron Johnson wrote: +> > > On Thu, 2003-01-16 at 08:20, Andrew Sullivan wrote: +> > +> > > > If a user has multiple connections and charges things to the same +> > > > account in more than one connection at the same time, the +> > > > transactions will have to be processed, effectively, in series: each +> > > > one will have to wait for another to commit in order to complete. +> > > +> > > This is true even though the default transaction mode is +> > > READ COMMITTED? +> > +> > Yes. Remember, _both_ of these are doing SELECT. . .FOR UPDATE. +> > Which means they both try to lock the corresponding record. But they +> > can't _both_ lock the same record; that's what the lock prevents. +> +> Could BEFORE INSERT|UPDATE|DELETE triggers perform the same +> functionality while touching only the desired records, thus +> decreasing conflict? + +It does limit it to the corresponding records, but if you +say insert a row pointing at customer 1, and in another transaction +insert a row pointing at customer 1, the second waits on the first. + + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 11:06:26 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 30B9D476809 + for ; + Thu, 16 Jan 2003 11:06:25 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 3D5A24766ED + for ; + Thu, 16 Jan 2003 11:05:17 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18ZCWA-0000Z2-00 + for ; Thu, 16 Jan 2003 11:05:22 -0500 +Date: Thu, 16 Jan 2003 11:05:22 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: schema/db design wrt performance +Message-ID: <20030116110522.F32288@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <20030116135140.32097.qmail@web21106.mail.yahoo.com> + <20030116092005.C22344@mail.libertyrms.com> + <1042727678.892.31.camel@haggis> + <20030116103933.B32288@mail.libertyrms.com> + <1042732204.892.35.camel@haggis> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <1042732204.892.35.camel@haggis>; + from ron.l.johnson@cox.net on Thu, Jan 16, 2003 at 09:50:04AM + -0600 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/153 +X-Sequence-Number: 800 + +On Thu, Jan 16, 2003 at 09:50:04AM -0600, Ron Johnson wrote: +> +> Could BEFORE INSERT|UPDATE|DELETE triggers perform the same +> functionality while touching only the desired records, thus +> decreasing conflict? + +You can make the constraint DEFERRABLE INITIALY DEFERRED. It helps +somewhat. But the potential for deadlock, and the backing up, will +still happen to some degree. It's a well-known flaw in the FK +system. I beleive the FK implementation was mostly intended as a +proof of concept. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 11:19:49 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 32AB14766BA + for ; + Thu, 16 Jan 2003 11:19:48 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP id 1E463476A4A + for ; + Thu, 16 Jan 2003 11:18:52 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id h0GGIZi16755; + Thu, 16 Jan 2003 11:18:35 -0500 (EST) +From: Bruce Momjian +Message-Id: <200301161618.h0GGIZi16755@candle.pha.pa.us> +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <3E26D564.1060209@clearmetrix.com> +To: "Charles H. Woloszynski" +Date: Thu, 16 Jan 2003 11:18:35 -0500 (EST) +Cc: Tom Lane , Roman Fail , + josh@agliodbs.com, pgsql-performance@postgresql.org +X-Mailer: ELM [version 2.4ME+ PL99 (25)] +MIME-Version: 1.0 +Content-Transfer-Encoding: 7bit +Content-Type: text/plain; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/154 +X-Sequence-Number: 801 + + +Is this a TODO item? + +--------------------------------------------------------------------------- + +Charles H. Woloszynski wrote: +> I was surprised to hear that JOIN syntax constrained the planner. We +> have a policy of using JOIN syntax to describe the table relationships +> and where clauses to describe the selection process for our queries. It +> was our understanding that the JOIN syntax was introduced to support +> this approach, but not to contrain the planner. +> +> Is there any way to sell the planner to consider JOIN syntax as +> equivalent to WHERE clauses and to not use them to force the planner +> down a specific path? Can we get that added as an option (and then made +> available to use JDBC folks as a URL parameter). It would make my team +> very happy :-). +> +> +> I think that making this an option will help all those migrating to +> Postgres who did not expect that JOINs forced the planner down specific +> plans. Is it possible/reasonable to add? +> +> Charlie +> +> +> Tom Lane wrote: +> +> >"Roman Fail" writes: +> > +> > +> >>Thanks to everyone for the quick replies! I'm sure that my lack of +> >>skill with SQL queries is the main problem. What's strange to me is +> >>how MSSQL takes my bad queries and makes them look good anyway. It +> >>must have a real smart planner. +> >> +> >> +> > +> >I think more likely the issue is that your use of JOIN syntax is forcing +> >Postgres into a bad plan. MSSQL probably doesn't assign any semantic +> >significance to the use of "a JOIN b" syntax as opposed to "FROM a, b" +> >syntax. Postgres does. Whether this is a bug or a feature depends on +> >your point of view --- but there are folks out there who find it to be +> >a life-saver. You can find some explanations at +> >http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/explicit-joins.html +> > +> > +> > +> >>Is it pretty much universally accepted that I should drop all my +> >>foreign keys? +> >> +> >> +> > +> >No. They don't have any effect on SELECT performance in Postgres. +> >They will impact update speed, but that's not your complaint (at the +> >moment). Don't throw away data integrity protection until you know +> >you need to. +> > +> > regards, tom lane +> > +> >---------------------------(end of broadcast)--------------------------- +> >TIP 4: Don't 'kill -9' the postmaster +> > +> > +> +> -- +> +> +> Charles H. Woloszynski +> +> ClearMetrix, Inc. +> 115 Research Drive +> Bethlehem, PA 18015 +> +> tel: 610-419-2210 x400 +> fax: 240-371-3256 +> web: www.clearmetrix.com +> +> +> +> +> +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 2: you can get off all lists at once with the unregister command +> (send "unregister YourEmailAddressHere" to majordomo@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 Jan 16 11:27:49 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4D63E47687A + for ; + Thu, 16 Jan 2003 11:27:47 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id D65DA476CC6 + for ; + Thu, 16 Jan 2003 11:25:32 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030116162538.LDCY8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Thu, 16 Jan 2003 11:25:38 -0500 +Subject: Re: schema/db design wrt performance +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <20030116080132.A4962-100000@megazone23.bigpanda.com> +References: <20030116080132.A4962-100000@megazone23.bigpanda.com> +Content-Type: text/plain +Organization: +Message-Id: <1042734336.892.42.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 16 Jan 2003 10:25:36 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/155 +X-Sequence-Number: 802 + +On Thu, 2003-01-16 at 10:02, Stephan Szabo wrote: +> On 16 Jan 2003, Ron Johnson wrote: +> +> > On Thu, 2003-01-16 at 09:39, Andrew Sullivan wrote: +> > > On Thu, Jan 16, 2003 at 08:34:38AM -0600, Ron Johnson wrote: +> > > > On Thu, 2003-01-16 at 08:20, Andrew Sullivan wrote: +> > > +> > > > > If a user has multiple connections and charges things to the same +> > > > > account in more than one connection at the same time, the +> > > > > transactions will have to be processed, effectively, in series: each +> > > > > one will have to wait for another to commit in order to complete. +> > > > +> > > > This is true even though the default transaction mode is +> > > > READ COMMITTED? +> > > +> > > Yes. Remember, _both_ of these are doing SELECT. . .FOR UPDATE. +> > > Which means they both try to lock the corresponding record. But they +> > > can't _both_ lock the same record; that's what the lock prevents. +> > +> > Could BEFORE INSERT|UPDATE|DELETE triggers perform the same +> > functionality while touching only the desired records, thus +> > decreasing conflict? +> +> It does limit it to the corresponding records, but if you +> say insert a row pointing at customer 1, and in another transaction +> insert a row pointing at customer 1, the second waits on the first. + +2 points: + +1. Don't you *want* TXN2 to wait on TXN1? +2. In an OLTP environment (heck, in *any* environment), the goal + is to minimize txn length, so TXN2 shouldn't be waiting on + TXN1 for more than a fraction of a second anyway. + +Am I missing something? + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 11:38:39 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 72BBF476227 + for ; + Thu, 16 Jan 2003 11:38:38 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 6FCA9476306 + for ; + Thu, 16 Jan 2003 11:38:03 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 46E81D606; Thu, 16 Jan 2003 08:38:08 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 3CA3A5C02; Thu, 16 Jan 2003 08:38:08 -0800 (PST) +Date: Thu, 16 Jan 2003 08:38:08 -0800 (PST) +From: Stephan Szabo +To: Ron Johnson +Cc: PgSQL Performance ML +Subject: Re: schema/db design wrt performance +In-Reply-To: <1042734336.892.42.camel@haggis> +Message-ID: <20030116083403.X4962-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/156 +X-Sequence-Number: 803 + +On 16 Jan 2003, Ron Johnson wrote: + +> On Thu, 2003-01-16 at 10:02, Stephan Szabo wrote: +> > On 16 Jan 2003, Ron Johnson wrote: +> > +> > > On Thu, 2003-01-16 at 09:39, Andrew Sullivan wrote: +> > > > On Thu, Jan 16, 2003 at 08:34:38AM -0600, Ron Johnson wrote: +> > > > > On Thu, 2003-01-16 at 08:20, Andrew Sullivan wrote: +> > > > +> > > > > > If a user has multiple connections and charges things to the same +> > > > > > account in more than one connection at the same time, the +> > > > > > transactions will have to be processed, effectively, in series: each +> > > > > > one will have to wait for another to commit in order to complete. +> > > > > +> > > > > This is true even though the default transaction mode is +> > > > > READ COMMITTED? +> > > > +> > > > Yes. Remember, _both_ of these are doing SELECT. . .FOR UPDATE. +> > > > Which means they both try to lock the corresponding record. But they +> > > > can't _both_ lock the same record; that's what the lock prevents. +> > > +> > > Could BEFORE INSERT|UPDATE|DELETE triggers perform the same +> > > functionality while touching only the desired records, thus +> > > decreasing conflict? +> > +> > It does limit it to the corresponding records, but if you +> > say insert a row pointing at customer 1, and in another transaction +> > insert a row pointing at customer 1, the second waits on the first. +> +> 2 points: +> +> 1. Don't you *want* TXN2 to wait on TXN1? + +Not really. Maybe I was unclear though. + +Given +create table pktable(a int primary key); +create table fktable(a int references pktable); +insert into pktable values (1); + +The blocking would occur on: +T1: begin; +T2: begin; +T1: insert into fktable values (1); +T2: insert into fktable values (1); + +This doesn't need to block. The reason for +the lock is to prevent someone from updating +or deleting the row out of pktable, but it +also prevents this kind of thing. This becomes +an issue if you say have tables that store mappings +and a table that has an fk to that. You'll +be inserting lots of rows with say +customertype=7 which points into a table with +types and they'll block. Worse, if you say +do inserts with different customertypes in +different orders in two transactions you +can deadlock yourself. + + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 11:46:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 92867475EF9 + for ; + Thu, 16 Jan 2003 11:46:13 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 229C8475BD7 + for ; + Thu, 16 Jan 2003 11:46:13 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18ZD9m-0001ne-00 + for ; Thu, 16 Jan 2003 11:46:18 -0500 +Date: Thu, 16 Jan 2003 11:46:18 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: schema/db design wrt performance +Message-ID: <20030116114618.G32288@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <20030116080132.A4962-100000@megazone23.bigpanda.com> + <1042734336.892.42.camel@haggis> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <1042734336.892.42.camel@haggis>; + from ron.l.johnson@cox.net on Thu, Jan 16, 2003 at 10:25:36AM + -0600 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/157 +X-Sequence-Number: 804 + +On Thu, Jan 16, 2003 at 10:25:36AM -0600, Ron Johnson wrote: +> +> 2 points: +> +> 1. Don't you *want* TXN2 to wait on TXN1? + +Not really. You really just want a tag which prevents TXN2 from +committing when its reference data might go away. So what you want +is a lock which says "don't delete, no matter what", until TXN2 +commits. Then TXN1 could fail or not, depending on what it's trying +to do. The problem is that there isn't a lock of the right strength +to do that. + +> 2. In an OLTP environment (heck, in *any* environment), the goal +> is to minimize txn length, so TXN2 shouldn't be waiting on +> TXN1 for more than a fraction of a second anyway. + +Right. But it's possible to have multiple REFERENCES constraints +to the same table; that's why I picked an account table, for +instance, because you might have a large number of different kinds of +things that the same account can do. So while you're correct that +one wants to minimize txn length, it's also true that, when the +effects are followed across a large system, you can easily start +tripping over the FKs. The real problem, then, only shows up on a +busy system with a table which gets referenced a lot. + +I should note, by the way, that the tremendous performance +improvements available in 7.2.x have reduced the problem considerably +from 7.1.x, at least in my experience. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 12:03:05 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C6C7F476585 + for ; + Thu, 16 Jan 2003 12:03:02 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 6E1B3476306 + for ; + Thu, 16 Jan 2003 12:02:33 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 6FA5BD606; Thu, 16 Jan 2003 09:02:38 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 6554C5C02; Thu, 16 Jan 2003 09:02:38 -0800 (PST) +Date: Thu, 16 Jan 2003 09:02:38 -0800 (PST) +From: Stephan Szabo +To: Roman Fail +Cc: Josh Berkus , Tom Lane , + +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C02@pos_pdc.posportal.com> +Message-ID: <20030116085358.E5729-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/158 +X-Sequence-Number: 805 + + +On Thu, 16 Jan 2003, Roman Fail wrote: + +> *********************** + +Hmm, I wonder if maybe we're going about things backwards in this +case. Does the original database have something like EXPLAIN +that'll show what it's doing? Perhaps that'll give an idea. + +> > What does vacuum verbose batchdetail give you (it'll give an idea of pages anyway) +> +> trans=# VACUUM VERBOSE batchdetail; +> INFO: --Relation public.batchdetail-- +> INFO: Pages 1669047: Changed 0, Empty 0; Tup 23316674: Vac 0, Keep 0, UnUsed 0. + +So about 12 gigabytes of data, then? + + +> It seems to me that the big, big isolated problem is the index scan on +> batchdetail.tranamount. During this small query, 'sar -b' showed +> consistent 90,000 block reads/sec. (contrast with only 6,000 with +> larger query index scan). 'top' shows the CPU is at 20% user, 30% +> system the whole time (contrast with 2% total in larger query above). + +Note that in this case below, you've gotten a sequence scan not an +index scan. (similar to setting enable_indexscan=off performance) + +> This results here still seem pretty bad (although not as bad as +> above), but I still don't know what is the bottleneck. And the +> strange sar stats are confusing me. +> +> EXPLAIN ANALYZE SELECT * FROM batchdetail WHERE tranamount BETWEEN 300 AND 499; +> Seq Scan on batchdetail (cost=0.00..2018797.11 rows=783291 width=440) (actual time=45.66..283926.58 rows=783687 loops=1) +> Filter: ((tranamount >= 300::numeric) AND (tranamount <= 499::numeric)) +> Total runtime: 285032.47 msec + +I'd assume that tranamount values are fairly randomly distributed +throughout the table, right? It takes about 5 minutes for the +system to read the entire table and more for the index scan, so +you're probably reading most of the table randomly and the index +as well. + +What values on batchdetail do you use in query where clauses +regularly? It's possible that occasional clusters would help +if this was the main field you filtered on. The cluster +itself is time consuming, but it might help make the index +scans actually read fewer pages. + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 12:16:29 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 782E1475F6A + for ; + Thu, 16 Jan 2003 12:16:26 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id ACEBB475BD7 + for ; + Thu, 16 Jan 2003 12:16:25 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2316163; Thu, 16 Jan 2003 09:16:33 -0800 +From: "Josh Berkus" +Subject: Re: 7.3.1 New install, large queries are slow +To: Tom Lane , "Roman Fail" +Cc: "Josh Berkus" , + sszabo@megazone23.bigpanda.com, pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Thu, 16 Jan 2003 09:16:33 -0800 +Message-ID: +In-Reply-To: <14736.1042730017@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/159 +X-Sequence-Number: 806 + +Roman, Tom: + +> No no no ... this is even worse than before. Your big tables are +> batchdetail (d) and purc1 (p1). What you've got to do is arrange the +> computation so that those are trimmed to just the interesting records +> as +> soon as possible. + +When joining disproportionally large tables, I've also had some success +with the following method: + +SELECT b.batchdate, d.batchdetailid, t.bankno, d.trandate, +d.tranamount, +d.submitinterchange, d.authamount, d.authno, d.cardtypeid, d.mcccode, +m.name AS merchantname, c.cardtype, m.merchid, +p1.localtaxamount, p1.productidentifier, dr.avsresponse, +cr.checkoutdate, cr.noshowindicator, ck.checkingacctno, +ck.abaroutingno, ck.checkno +FROM tranheader t +JOIN batchheader b ON (t.tranheaderid = b.tranheaderid AND b.batchdate +> '2002-12-15') +JOIN merchants m ON (m.merchantid = b.merchantid AND mmerchid = +'701252267') +JOIN batchdetail d ON (d.batchid = b.batchid AND d.tranamount BETWEEN +500 and 700) +JOIN cardtype c ON d.cardtypeid = c.cardtypeid +LEFT JOIN purc1 p1 ON p1.batchdetailid = d.batchdetailid +LEFT JOIN direct dr ON dr.batchdetailid = d.batchdetailid +LEFT JOIN carrental cr ON cr.batchdetailid = d.batchdetailid +LEFT JOIN checks ck ON ck.batchdetailid = d.batchdetailid +WHERE t.clientid = 6 +AND d.tranamount BETWEEN 500.0 AND 700.0 +AND b.batchdate > '2002-12-15' +AND m.merchid = '701252267' +ORDER BY b.batchdate DESC +LIMIT 50 + +This could be re-arranged some, but I think you get the idea ... I've +been able, in some queries, to get the planner to use a better and +faster join strategy by repeating my WHERE conditions in the JOIN +criteria. + +-Josh + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 12:25:56 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E7119476615 + for ; + Thu, 16 Jan 2003 12:25:53 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id CCEE4476122 + for ; + Thu, 16 Jan 2003 12:24:47 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030116172454.LRLW8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Thu, 16 Jan 2003 12:24:54 -0500 +Subject: Re: schema/db design wrt performance +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <20030116083403.X4962-100000@megazone23.bigpanda.com> +References: <20030116083403.X4962-100000@megazone23.bigpanda.com> +Content-Type: text/plain +Organization: +Message-Id: <1042737892.889.56.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 16 Jan 2003 11:24:52 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/160 +X-Sequence-Number: 807 + +On Thu, 2003-01-16 at 10:38, Stephan Szabo wrote: +> On 16 Jan 2003, Ron Johnson wrote: +> +> > On Thu, 2003-01-16 at 10:02, Stephan Szabo wrote: +> > > On 16 Jan 2003, Ron Johnson wrote: +> > > +> > > > On Thu, 2003-01-16 at 09:39, Andrew Sullivan wrote: +> > > > > On Thu, Jan 16, 2003 at 08:34:38AM -0600, Ron Johnson wrote: +> > > > > > On Thu, 2003-01-16 at 08:20, Andrew Sullivan wrote: +> > > > > +> > > > > > > If a user has multiple connections and charges things to the same +> > > > > > > account in more than one connection at the same time, the +> > > > > > > transactions will have to be processed, effectively, in series: each +> > > > > > > one will have to wait for another to commit in order to complete. +> > > > > > +> > > > > > This is true even though the default transaction mode is +> > > > > > READ COMMITTED? +> > > > > +> > > > > Yes. Remember, _both_ of these are doing SELECT. . .FOR UPDATE. +> > > > > Which means they both try to lock the corresponding record. But they +> > > > > can't _both_ lock the same record; that's what the lock prevents. +> > > > +> > > > Could BEFORE INSERT|UPDATE|DELETE triggers perform the same +> > > > functionality while touching only the desired records, thus +> > > > decreasing conflict? +> > > +> > > It does limit it to the corresponding records, but if you +> > > say insert a row pointing at customer 1, and in another transaction +> > > insert a row pointing at customer 1, the second waits on the first. +> > +> > 2 points: +> > +> > 1. Don't you *want* TXN2 to wait on TXN1? +> +> Not really. Maybe I was unclear though. +> +> Given +> create table pktable(a int primary key); +> create table fktable(a int references pktable); +> insert into pktable values (1); +> +> The blocking would occur on: +> T1: begin; +> T2: begin; +> T1: insert into fktable values (1); +> T2: insert into fktable values (1); +> +> This doesn't need to block. The reason for +> the lock is to prevent someone from updating +> or deleting the row out of pktable, but it +> also prevents this kind of thing. This becomes +> an issue if you say have tables that store mappings +> and a table that has an fk to that. You'll +> be inserting lots of rows with say +> customertype=7 which points into a table with +> types and they'll block. Worse, if you say +> do inserts with different customertypes in +> different orders in two transactions you +> can deadlock yourself. + +So Postgres will think it's possible that I could modify the +reference table that "customertype=7" refers to? If so, bummer. + +The commercial RDBMS that I use (Rdb/VMS) allows one to specify +that certain tables are only for read access. + +For example: +SET TRANSACTION READ WRITE + RESERVING T_MASTER, T_DETAIL FOR SHARED WRITE, + T_MAPPING1, T_MAPPING2, T_MAPPING3 FOR SHARED READ; + +Thus, only minimal locking is taken out on T_MAPPING1, T_MAPPING2 +& T_MAPPING3, but if I try to "UPDATE T_MAPPING1" or reference any +other table, even in a SELECT statement, then the statement will +fail. + +Rdb also alows for exclusive write locks: +SET TRANSACTION READ WRITE + RESERVING T_MASTER, T_DETAIL FOR SHARED WRITE, + T_MAPPING1, T_MAPPING2, T_MAPPING3 FOR SHARED READ, + T_FOOBAR FOR EXCLUSIVE WRITE; + +Thus, even though there is concurrent access to the other tables, +a table lock on T_FOOBAR is taken out. This cuts IO usage in 1/2, +but obviously must be used with great discretion. + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 12:28:23 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 851F54761DD + for ; + Thu, 16 Jan 2003 12:28:21 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id CCEF147619E + for ; + Thu, 16 Jan 2003 12:28:20 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2316193; Thu, 16 Jan 2003 09:28:28 -0800 +From: "Josh Berkus" +Subject: Re: 7.3.1 New install, large queries are slow +To: "Roman Fail" , + "Josh Berkus" , "Tom Lane" , + +Cc: +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Thu, 16 Jan 2003 09:28:28 -0800 +Message-ID: +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C02@pos_pdc.posportal.com> +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/161 +X-Sequence-Number: 808 + +Roman, + +> > Hey, Roman, how many records in BatchDetail, anyway? +> +> 23 million. + +And MSSQL is returning results in 3 seconds? I find that a bit hard +to believe, unless this query is called repeatedly and that's the +figure for the last call, where the records are being cached. I'll +have to look at your hardware descriptions again. + +> It seems to me that the big, big isolated problem is the index scan +> on batchdetail.tranamount. + +Nope. This was a misimpression caused by batchdetail waiting for a +bunch of other processes to complete. Sometimes the parallelizing +gives me a wrong impression of what's holding up the query. Sorry if I +confused you. + +> I hope we can come up with something soon.....it seems this index +> scan is a big part of the problem. I'm still really curious why the +> disk reads are so few with the index scan. Let's hope I can get it +> near the 3 second time for MSSQL by Friday! + +Um, Roman, keep in mind this is a mailing list. I'm sure that +everyone here is happy to give you the tools to figure out how to fix +things, but only in a DIY fashion, and not on your schedule. + +If you have a deadline, you'd better hire some paid query/database +tuning help. DB Tuning experts .... whether on MSSQL or Postgres ... +run about $250/hour last I checked. + +-Josh Berkus + +From pgsql-performance-owner@postgresql.org Thu Jan 16 12:30:11 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D80B4476547 + for ; + Thu, 16 Jan 2003 12:30:08 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id BF3784764AB + for ; + Thu, 16 Jan 2003 12:30:07 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0GHU95u016506; + Thu, 16 Jan 2003 12:30:09 -0500 (EST) +To: "Josh Berkus" +Cc: "Roman Fail" , + sszabo@megazone23.bigpanda.com, pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: +References: +Comments: In-reply-to "Josh Berkus" + message dated "Thu, 16 Jan 2003 09:16:33 -0800" +Date: Thu, 16 Jan 2003 12:30:09 -0500 +Message-ID: <16505.1042738209@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/162 +X-Sequence-Number: 809 + +"Josh Berkus" writes: +> This could be re-arranged some, but I think you get the idea ... I've +> been able, in some queries, to get the planner to use a better and +> faster join strategy by repeating my WHERE conditions in the JOIN +> criteria. + +Hm. It shouldn't be necessary to do that --- the planner should be able +to push down the WHERE conditions to the right place without that help. + +The list of explicit JOINs as you have here is a good way to proceed +*if* you write the JOINs in an appropriate order for implementation. +I believe the problem with Roman's original query was that he listed +the JOINs in a bad order. Unfortunately I didn't keep a copy of that +message, and the list archives seem to be a day or more behind... +but at least for these WHERE conditions, it looks like the best bet +would to join m to b (I'm assuming m.merchid is unique), then to t, +then to d, then add on the others. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 16 12:47:00 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6C11747619E + for ; + Thu, 16 Jan 2003 12:46:57 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id EE9CA47610B + for ; + Thu, 16 Jan 2003 12:46:56 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 614AAD606; Thu, 16 Jan 2003 09:47:02 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 5704B5C02; Thu, 16 Jan 2003 09:47:02 -0800 (PST) +Date: Thu, 16 Jan 2003 09:47:02 -0800 (PST) +From: Stephan Szabo +To: Josh Berkus +Cc: Roman Fail , Tom Lane , + +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: +Message-ID: <20030116094210.L6318-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/163 +X-Sequence-Number: 810 + + +On Thu, 16 Jan 2003, Josh Berkus wrote: + +> Roman, +> +> > > Hey, Roman, how many records in BatchDetail, anyway? +> > +> > 23 million. +> +> And MSSQL is returning results in 3 seconds? I find that a bit hard +> to believe, unless this query is called repeatedly and that's the +> figure for the last call, where the records are being cached. I'll +> have to look at your hardware descriptions again. +> +> > It seems to me that the big, big isolated problem is the index scan +> > on batchdetail.tranamount. +> +> Nope. This was a misimpression caused by batchdetail waiting for a +> bunch of other processes to complete. Sometimes the parallelizing +> gives me a wrong impression of what's holding up the query. Sorry if I +> confused you. + +I'm still not sure that it isn't a big part given that the time went down +by a factor of about 4 when index scans were disabled and a sequence scan +was done and that a sequence scan over the table with no other tables +joined looked to take about 5 minutes itself and the difference between +that seqscan and the big query was only about 20 seconds when +enable_indexscan was off unless I'm misreading those results. + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 12:52:51 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 116804760CE + for ; + Thu, 16 Jan 2003 12:52:50 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 61A734767DA + for ; + Thu, 16 Jan 2003 12:52:39 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2316240; Thu, 16 Jan 2003 09:52:47 -0800 +From: "Josh Berkus" +Subject: Re: 7.3.1 New install, large queries are slow +To: Tom Lane , "Josh Berkus" +Cc: "Roman Fail" , + sszabo@megazone23.bigpanda.com, pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Thu, 16 Jan 2003 09:52:47 -0800 +Message-ID: +In-Reply-To: <16505.1042738209@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/164 +X-Sequence-Number: 811 + +Tom, + +> The list of explicit JOINs as you have here is a good way to proceed +> *if* you write the JOINs in an appropriate order for implementation. +> I believe the problem with Roman's original query was that he listed +> the JOINs in a bad order. Unfortunately I didn't keep a copy of that +> message, and the list archives seem to be a day or more behind... +> but at least for these WHERE conditions, it looks like the best bet +> would to join m to b (I'm assuming m.merchid is unique), then to t, +> then to d, then add on the others. + +I realize that I've contributed nothing other than bug reports to the +parser design. But shouldn't Postgres, given a free hand, figure out +the above automatically? I'd be embarassed if MS could one-up us in +parser planning anywhere, theirs sucks on sub-selects .... + +-Josh Berkus + +From pgsql-performance-owner@postgresql.org Thu Jan 16 13:40:44 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D72554753A1 + for ; + Thu, 16 Jan 2003 13:40:41 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id B139A476547 + for ; + Thu, 16 Jan 2003 13:40:36 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0GIeW5u026147; + Thu, 16 Jan 2003 13:40:33 -0500 (EST) +To: "Josh Berkus" +Cc: "Roman Fail" , + sszabo@megazone23.bigpanda.com, pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: +References: +Comments: In-reply-to "Josh Berkus" + message dated "Thu, 16 Jan 2003 09:52:47 -0800" +Date: Thu, 16 Jan 2003 13:40:32 -0500 +Message-ID: <26146.1042742432@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/165 +X-Sequence-Number: 812 + +"Josh Berkus" writes: +>> but at least for these WHERE conditions, it looks like the best bet +>> would to join m to b (I'm assuming m.merchid is unique), then to t, +>> then to d, then add on the others. + +> I realize that I've contributed nothing other than bug reports to the +> parser design. But shouldn't Postgres, given a free hand, figure out +> the above automatically? + +I believe it will. So far I've not seen an EXPLAIN from a query that +was structured to give it a free hand. + +As noted elsewhere, the fact that we allow JOIN syntax to constrain the +planner is a real pain if you are accustomed to databases that don't do +that. On the other hand, it's a real lifesaver for people who need to +pare the planning time for dozen-way joins; it was only a day or two +back in this same mailing list that we last had a discussion about that +end of the problem. So even though it started out as an implementation +shortcut rather than an intended feature, I'm loathe to just disable the +behavior entirely. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 16 13:51:28 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 682AD476C13 + for ; + Thu, 16 Jan 2003 13:43:44 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 52AB1476D69 + for ; + Thu, 16 Jan 2003 13:43:02 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 2918AD606; Thu, 16 Jan 2003 10:43:02 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 1AC8B5C02; Thu, 16 Jan 2003 10:43:02 -0800 (PST) +Date: Thu, 16 Jan 2003 10:43:02 -0800 (PST) +From: Stephan Szabo +To: Roman Fail +Cc: , +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4BFD@pos_pdc.posportal.com> +Message-ID: <20030116103622.K6828-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/166 +X-Sequence-Number: 813 + + +On Wed, 15 Jan 2003, Roman Fail wrote: + +I just had new thoughts. + +If you make an index on batchdetail(batchid) +does that help? + +I realized that it was doing a merge join +to join d and the (t,b,m) combination when it +was expecting 3 rows out of the latter, and +batchid is presumably fairly selective on +the batchdetail table, right? I'd have expected +a nested loop over the id column, but it +doesn't appear you have an index on it in +batchdetail. + +Then I realized that batchheader.batchid and +batchdetail.batchid don't even have the same +type, and that's probably something else you'd +need to fix. + +> batchheader has 2.6 million records: +> CREATE TABLE public.batchheader ( +> batchid int8 DEFAULT nextval('"batchheader_batchid_key"'::text) NOT NULL, + +> And here's batchdetail too, just for kicks. 23 million records. +> CREATE TABLE public.batchdetail ( +> batchid int4, + + + + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 14:51:34 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3DBAF4768F9 + for ; + Thu, 16 Jan 2003 14:50:46 -0500 (EST) +Received: from pos_pdc.posportal.com (unknown [12.158.169.100]) + by postgresql.org (Postfix) with ESMTP id 4C51B4771B6 + for ; + Thu, 16 Jan 2003 14:22:22 -0500 (EST) +X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3 +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="utf-8" +Content-Transfer-Encoding: base64 +Subject: Re: 7.3.1 New install, large queries are slow +Date: Thu, 16 Jan 2003 11:22:03 -0800 +Message-ID: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C06@pos_pdc.posportal.com> +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [PERFORM] 7.3.1 New install, large queries are slow +Thread-Index: AcK9hK1eAKq/LDlWSFqachkkBnyCAAABkDvh +From: "Roman Fail" +To: "Josh Berkus" , + "Tom Lane" , +Cc: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/167 +X-Sequence-Number: 814 + +PiBKb3NoIEJlcmt1cyB3cm90ZToNCj4gQW5kIE1TU1FMIGlzIHJldHVybmlu +ZyByZXN1bHRzIGluIDMgc2Vjb25kcz8gICAgSSBmaW5kIHRoYXQgYSBiaXQg +aGFyZA0KPiB0byBiZWxpZXZlLCB1bmxlc3MgdGhpcyBxdWVyeSBpcyBjYWxs +ZWQgcmVwZWF0ZWRseSBhbmQgdGhhdCdzIHRoZQ0KPiBmaWd1cmUgZm9yIHRo +ZSBsYXN0IGNhbGwsIHdoZXJlIHRoZSByZWNvcmRzIGFyZSBiZWluZyBjYWNo 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+bmdzLCBidXQgb25seSBpbiBhIERJWSBmYXNoaW9uLCBhbmQgbm90IG9uIHlv +dXIgc2NoZWR1bGUuIA0KDQpJIGhhdGUgYmVpbmcgZGVmZW5zaXZlLCBidXQg +SSBkb24ndCByZW1lbWJlciBzYXlpbmcgdGhhdCBJIGV4cGVjdCBhbnlvbmUg +dG8gZml4IG15IHByb2JsZW1zIGZvciBtZSBvbiBteSBzY2hlZHVsZS4gICpJ +KiBob3BlIHRoYXQgKkkqIGNhbiBnZXQgdGhpcyBkb25lIGJ5IEZyaWRheSwg +YmVjYXVzZSBvdGhlcndpc2UgbXkgYm9zcyBpcyBnb2luZyB0byB0ZWxsIG1l +IHRvIGR1bXAgUG9zdGdyZXMgYW5kIGluc3RhbGwgTVNTUUwgb24gdGhlIHNl +cnZlci4gIEkgb25seSBtZW50aW9uIHRoaXMgZmFjdCBiZWNhdXNlIGl0J3Mg +YSBibG93IGFnYWluc3QgUG9zdGdyZVNRTCdzIHJlcHV0YXRpb24gaWYgSSBo +YXZlIHRvIGdpdmUgdXAuICBUaGVyZSBpcyBubyBwcmVzc3VyZSBvbiB5b3Us +IGFuZCBJIGFwb2xvZ2l6ZSBpZiBzb21ldGhpbmcgSSBzYWlkIHNvdW5kZWQg +bGlrZSB3aGluaW5nLg0KIA0KSSBhbSBWRVJZIGdyYXRlZnVsIGZvciB0aGUg +dGltZSB0aGF0IGFsbCBvZiB5b3UgaGF2ZSBnaXZlbiB0byB0aGlzIHByb2Js +ZW0uDQogDQpSb21hbiBGYWlsDQpTci4gV2ViIEFwcGxpY2F0aW9uIFByb2dy +YW1tZXINClBPUyBQb3J0YWwsIEluYy4NCiANCg== + +From pgsql-performance-owner@postgresql.org Thu Jan 16 14:54:09 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B7ADC476DDC + for ; + Thu, 16 Jan 2003 14:54:05 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id BA168476386 + for ; + Thu, 16 Jan 2003 14:36:05 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id D5D9AD606; Thu, 16 Jan 2003 11:35:55 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id CB8385C02; Thu, 16 Jan 2003 11:35:55 -0800 (PST) +Date: Thu, 16 Jan 2003 11:35:55 -0800 (PST) +From: Stephan Szabo +To: Roman Fail +Cc: Josh Berkus , Tom Lane , + +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C06@pos_pdc.posportal.com> +Message-ID: <20030116112424.S7433-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/168 +X-Sequence-Number: 815 + + +On Thu, 16 Jan 2003, Roman Fail wrote: + +> > Stephan Szabo wrote: +> > I'd assume that tranamount values are fairly randomly distributed +> > throughout the table, right? It takes about 5 minutes for the +> > system to read the entire table and more for the index scan, so +> > you're probably reading most of the table randomly and the index +> > as well. +> > What values on batchdetail do you use in query where clauses regularly? + +> Yes, tranamount values are randomly distributed. I don't understand +> why an index scan would be "random", isn't the whole point of an index +> to have an ordered reference into the data? batchdetail has 5 columns +> that can be in the WHERE clause, all of which are indexed. None is +> more likely than the other to be searched, so a clustered index +> doesn't make much sense to me. The whole thing needs to be fast. + +Yeah, in that case a clustered index doesn't help. +Indexes give you an ordered way to find the rows that meet a condition, +but say you had three rows in your table in this order (note that this is +an amazing oversimplification): +(1,'a') +(2,'b') +(0,'c') + +And you want to scan the index from values with the first number between 0 +and 2. It reads the third row, then the first, then the second (to get +the letter associated). Between those reads, it's got to seek back and +forth through the heap file and the order in which it hits them is pretty +random seeming (to the kernel). + +> > Ron Johnson wrote: +> > What are the indexes on batchdetail? +> > There's one on batchid and a seperate one on tranamount? +> > If so, what about dropping them and create a single multi-segment +> > index on "batchid, tranamount". (A constraint can then enforce +> > uniqueness on batchid. +> There is no index on batchid, I think it is a good idea to create +> one. Stephan also suggested this. After I try the single batchid +> index, I might try to multi-segment index idea as well. I'll post +> results later today. + +I think we may all have misread the index list to include an index on +batchid. Also you have two indexes on batchdetailid right now (primary key +also creates one) which added to the confusion. + +> > Stephan Szabo wrote: +> > Then I realized that batchheader.batchid and +> > batchdetail.batchid don't even have the same +> > type, and that's probably something else you'd +> > need to fix. +> +> Yes, that's a mistake on my part....batchdetail(batchid) should be an +> int8. It looks to me like converting this datatype can't be done with +> a single ALTER TABLE ALTER COLUMN statement.....so I guess I'll work +> around it with an ADD, UPDATE, DROP, and RENAME. + +Don't forget to do a vacuum full in there as well. + + + + +From pgsql-performance-owner@postgresql.org Thu Jan 16 14:57:44 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6A6204768A5 + for ; + Thu, 16 Jan 2003 14:56:51 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 18DAC4769AF + for ; + Thu, 16 Jan 2003 14:46:43 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0GJkX5u026713; + Thu, 16 Jan 2003 14:46:34 -0500 (EST) +To: "Roman Fail" +Cc: "Josh Berkus" , + sszabo@megazone23.bigpanda.com, pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C06@pos_pdc.posportal.com> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C06@pos_pdc.posportal.com> +Comments: In-reply-to "Roman Fail" + message dated "Thu, 16 Jan 2003 11:22:03 -0800" +Date: Thu, 16 Jan 2003 14:46:33 -0500 +Message-ID: <26712.1042746393@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/169 +X-Sequence-Number: 816 + +"Roman Fail" writes: +> -> Merge Join (cost=1543595.18..1545448.76 rows=1 width=172) (actual time=1195311.88..1195477.32 rows=5 loops=1) +> Merge Cond: ("outer".batchid = "inner".batchid) +> -> Sort (cost=476.17..476.18 rows=4 width=102) (actual time=30.57..30.59 rows=17 loops=1) +> Sort Key: b.batchid +> -> Nested Loop (cost=0.00..476.14 rows=4 width=102) (actual time=25.21..30.47 rows=17 loops=1) +> -> Index Scan using merchants_ix_merchid_idx on merchants m (cost=0.00..5.65 rows=1 width=78) (actual time=23.81..23.82 rows=1 loops=1) +> Index Cond: (merchid = '701252267'::character varying) +> -> Index Scan using batchheader_ix_merchantid_idx on batchheader b (cost=0.00..470.30 rows=15 width=24) (actual time=1.38..6.55 rows=17 loops=1) +> Index Cond: ("outer".merchantid = b.merchantid) +> Filter: (batchdate > '2002-12-15 00:00:00'::timestamp without time zone) +> -> Sort (cost=1543119.01..1544045.79 rows=370710 width=70) (actual time=1194260.51..1194892.79 rows=368681 loops=1) +> Sort Key: d.batchid +> -> Index Scan using batchdetail_ix_tranamount_idx on batchdetail d (cost=0.00..1489103.46 rows=370710 width=70) (actual time=5.26..1186051.44 rows=370307 loops=1) +> Index Cond: ((tranamount >= 500.0) AND (tranamount <= 700.0)) + +The expensive part of this is clearly the sort and merge of the rows +extracted from batchdetail. The index on tranamount is not helping +you at all, because the condition (between 500 and 700) isn't very +selective --- it picks up 370000 rows --- and since those rows are +totally randomly scattered in the table, you do a ton of random +seeking. It's actually faster to scan the table linearly --- that's why +enable_indexscan=off was faster. + +However, I'm wondering why the thing picked this plan, when it knew it +would get only a few rows out of the m/b join (estimate 4, actual 17, +not too bad). I would have expected it to use an inner indexscan on +d.batchid. Either you've not got an index on d.batchid, or there's a +datatype mismatch that prevents the index from being used. What are the +datatypes of d.batchid and b.batchid, exactly? If they're not the same, +either make them the same or add an explicit coercion to the query, like + WHERE d.batchid = b.batchid::typeof_d_batchid + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 16 16:25:15 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 467D8476D5C + for ; + Thu, 16 Jan 2003 16:12:33 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 3CC7B476299 + for ; + Thu, 16 Jan 2003 15:51:51 -0500 (EST) +Received: by serwer.skawsoft.com.pl (Postfix, from userid 1000) + id 517F22B26E; Thu, 16 Jan 2003 21:48:26 +0100 (CET) +Date: Thu, 16 Jan 2003 21:48:26 +0100 +To: Tom Lane +Cc: Roman Fail , + Josh Berkus , sszabo@megazone23.bigpanda.com, + pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +Message-ID: <20030116204826.GA26576@serwer> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C06@pos_pdc.posportal.com> + <26712.1042746393@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <26712.1042746393@sss.pgh.pa.us> +User-Agent: Mutt/1.3.28i +From: jasiek@klaster.net +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/170 +X-Sequence-Number: 817 + +Tom said: +> datatype mismatch that prevents the index from being used. What are the +> datatypes of d.batchid and b.batchid, exactly? If they're not the same, +> either make them the same or add an explicit coercion to the query, like +> WHERE d.batchid = b.batchid::typeof_d_batchid +> +It can be source of problem. I found in one of Roman's mail, that +batchid is declared as int8 in master table and as int4 in detail table. +Regards, +Tomasz Myrta + +From pgsql-performance-owner@postgresql.org Fri Jan 17 00:54:41 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 299CD476543 + for ; + Fri, 17 Jan 2003 00:54:36 -0500 (EST) +Received: from pos_pdc.posportal.com (unknown [12.158.169.100]) + by postgresql.org (Postfix) with ESMTP id 301D947651E + for ; + Fri, 17 Jan 2003 00:54:34 -0500 (EST) +X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3 +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="utf-8" +Content-Transfer-Encoding: base64 +Subject: Re: 7.3.1 New install, large queries are slow +Date: Thu, 16 Jan 2003 21:54:39 -0800 +Message-ID: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C09@pos_pdc.posportal.com> +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [PERFORM] 7.3.1 New install, large queries are slow +Thread-Index: AcK9l/wPnT5XK39ZSQKMu5my8Z07QgAKAnUG +From: "Roman Fail" +To: "Tom Lane" +Cc: "Josh Berkus" , + , +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/171 +X-Sequence-Number: 818 + +VG9tIGFuZCBUb21hc3o6DQpJIGhhdmUgdG8gY2hhbmdlIHRoZSBkYXRhdHlw +ZSBvZiBiYXRjaGRldGFpbC5iYXRjaGlkIGZyb20gaW50NCB0byBpbnQ4LiAg +QWZ0ZXIgb3ZlciA0IGhvdXJzLCB0aGUgVVBEQVRFIHRyYW5zZmVyIGZyb20g +dGhlIG9sZCBjb2x1bW4gdG8gbmV3IGhhcyBub3QgeWV0IGNvbXBsZXRlZC4g +IEFmdGVyIHRoYXQgSSBzdGlsbCBoYXZlIHRvIGJ1aWxkIGEgbmV3IGluZGV4 +IGFuZCBydW4gVkFDVVVNIEZVTEwuICBXaGVuIHRoYXQgaXMgYWxsIGRvbmUg +SSdsbCByZS1ydW4gdGhlIHZhcmlvdXMgcXVlcmllcywgaW5jbHVkaW5nIGEg +c3BlY2lmaWMgc21hbGwgb25lIHRoYXQgSm9zaCByZXF1ZXN0ZWQuICANCiAN +CkNoYWQgVGhvbXBzb24gc3VnZ2VzdGVkIHRoYXQgSSBhZGQgc2luZ2xlIHF1 +b3RlcyBhcm91bmQgdGhlIGxpdGVyYWxzIGluIHRoZSBXSEVSRSBjbGF1c2Us +IHdoaWNoIHNvdW5kZWQgbGlrZSBhIGdyZWF0IGlkZWEgYmFzZWQgb24gaGlz +IGV4cGVyaWVuY2UuICBVbmZvcnR1bmF0ZWx5LCBpdCBkaWQgbm90IG1ha2Ug 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2003 01:06:17 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 28AC647592C + for ; + Fri, 17 Jan 2003 01:06:17 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0H66A5u004982; + Fri, 17 Jan 2003 01:06:10 -0500 (EST) +To: "Roman Fail" +Cc: "Josh Berkus" , + sszabo@megazone23.bigpanda.com, pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C09@pos_pdc.posportal.com> +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C09@pos_pdc.posportal.com> +Comments: In-reply-to "Roman Fail" + message dated "Thu, 16 Jan 2003 21:54:39 -0800" +Date: Fri, 17 Jan 2003 01:06:10 -0500 +Message-ID: <4981.1042783570@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/172 +X-Sequence-Number: 819 + +"Roman Fail" writes: +> shared_buffers = 131072 + +Yipes! Try about a tenth that much. Or less. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 17 02:00:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C6122475C5F + for ; + Fri, 17 Jan 2003 02:00:49 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 4CBB4475BC3 + for ; + Fri, 17 Jan 2003 02:00:49 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 11B2DD602; Thu, 16 Jan 2003 23:00:49 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 076C75C03; Thu, 16 Jan 2003 23:00:48 -0800 (PST) +Date: Thu, 16 Jan 2003 23:00:48 -0800 (PST) +From: Stephan Szabo +To: Roman Fail +Cc: +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C09@pos_pdc.posportal.com> +Message-ID: <20030116225602.G17408-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/173 +X-Sequence-Number: 820 + + +On Thu, 16 Jan 2003, Roman Fail wrote: + +> > Stephan Szabo wrote: +> > Also you have two indexes on batchdetailid right now (primary key +> > also creates one) which added to the confusion. +> +> The 7.3.1 docs for CREATE TABLE don't mention anything about automatic +> index creation for a PRIMARY KEY. I didn't see any PK indexes via +> pgAdminII, so I read this line from the docs and decided to create +> them separately. +> "Technically, PRIMARY KEY is merely a combination of UNIQUE and NOT NULL" + +Right, but the implementation of UNIQUE constraints in postgresql right +now is through a unique index. That's not necessarily a guarantee for +the future, but for right now you can rely on it. + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 06:47:55 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D9EB6475E18 + for ; + Fri, 17 Jan 2003 06:47:54 -0500 (EST) +Received: from mail.sarkor.com (unknown [81.95.224.36]) + by postgresql.org (Postfix) with SMTP id 5BC2F475EC9 + for ; + Fri, 17 Jan 2003 06:47:52 -0500 (EST) +Received: (qmail 10337 invoked by uid 507); 17 Jan 2003 11:47:51 -0000 +Received: from thor@sarkor.com by mail.sarkor.com by uid 504 with + qmail-scanner-1.14 (clamscan: 0.51. Clear:. + Processed in 0.440657 secs); 17 Jan 2003 11:47:51 -0000 +Received: from unknown (HELO timur) (81.95.224.66) + by mail.sarkor.com with SMTP; 17 Jan 2003 11:47:50 -0000 +Date: Fri, 17 Jan 2003 16:48:00 +0500 +From: Timur Irmatov +X-Mailer: The Bat! (v1.61) +Reply-To: Timur Irmatov +X-Priority: 3 (Normal) +Message-ID: <10597430257.20030117164800@sarkor.com> +To: pgsql-performance@postgresql.org +Subject: index usage +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/174 +X-Sequence-Number: 821 + +Hi, everyone! + +I have a simple query which takes almost 3 seconds to complete, but +disabling sequence scans leads to a new plan using index. This second +plan takes less than 1 millisecond to run. + +So, I'd like to hear any comments and suggestions. + +Details. + +CREATE TABLE MediumStats ( + year SMALLINT NOT NULL, + month SMALLINT NOT NULL, + day SMALLINT NOT NULL, + hour SMALLINT NOT NULL, + --- and then goes few data fields + figureId INTEGER NOT NULL, + typeId INTEGER NOT NULL + PRIMARY KEY (figureId, typeId, year, month, day, hour) +); + +CREATE FUNCTION indexHelper (INT2, INT2, INT2, INT2) +RETURNS CHARACTER(10) AS ' +return sprintf("%d%02d%02d%02d", @_); +' LANGUAGE 'plperl' WITH (isCachable); + +CREATE INDEX timeIndex ON MediumStats (indexHelper(year,month,day,hour)); + +and that is the query: +SELECT * FROM MediumStats +WHERE indexHelper(year,month,day,hour) < '2002121500' +LIMIT 1; + +First, original plan: +Limit (cost=0.00..0.09 rows=1 width=22) (actual time=2969.30..2969.30 rows=0 loops=1) + -> Seq Scan on mediumstats (cost=0.00..1332.33 rows=15185 width=22) (actual time=2969.29..2969.29 rows=0 loops=1) +Total runtime: 2969.39 msec + +Second plan, seq scans disabled: + +Limit (cost=0.00..0.19 rows=1 width=6) (actual time=0.43..0.43 rows=0 loops=1) + -> Index Scan using timeindex on mediumstats (cost=0.00..2898.96 rows=15185 width=6) (actual time=0.42..0.42 rows=0 loops=1) +Total runtime: 0.54 msec + +Table MediumStats currently has 45000 rows, all rows belong to this +month. + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 08:29:37 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5138C4760B7 + for ; + Fri, 17 Jan 2003 08:29:36 -0500 (EST) +Received: from clearmetrix.com (unknown [209.92.142.67]) + by postgresql.org (Postfix) with ESMTP id 9F009476078 + for ; + Fri, 17 Jan 2003 08:29:35 -0500 (EST) +Received: from clearmetrix.com (chw.muvpn.clearmetrix.com [172.16.1.3]) + by clearmetrix.com (8.11.6/linuxconf) with ESMTP id h0HDTNM10103; + Fri, 17 Jan 2003 08:29:23 -0500 +Message-ID: <3E280535.1090909@clearmetrix.com> +Date: Fri, 17 Jan 2003 08:29:25 -0500 +From: "Charles H. Woloszynski" +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; + rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Bruce Momjian +Cc: Tom Lane , Roman Fail , + josh@agliodbs.com, pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +References: <200301161618.h0GGIZi16755@candle.pha.pa.us> +In-Reply-To: <200301161618.h0GGIZi16755@candle.pha.pa.us> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/175 +X-Sequence-Number: 822 + +I'd love to see this as a TODO item, but I am hardly one to add to the +list... + +Charlie + + +Bruce Momjian wrote: + +>Is this a TODO item? +> +>--------------------------------------------------------------------------- +> +>Charles H. Woloszynski wrote: +> +> +>>I was surprised to hear that JOIN syntax constrained the planner. We +>>have a policy of using JOIN syntax to describe the table relationships +>>and where clauses to describe the selection process for our queries. It +>>was our understanding that the JOIN syntax was introduced to support +>>this approach, but not to contrain the planner. +>> +>>Is there any way to sell the planner to consider JOIN syntax as +>>equivalent to WHERE clauses and to not use them to force the planner +>>down a specific path? Can we get that added as an option (and then made +>>available to use JDBC folks as a URL parameter). It would make my team +>>very happy :-). +>> +>> +>>I think that making this an option will help all those migrating to +>>Postgres who did not expect that JOINs forced the planner down specific +>>plans. Is it possible/reasonable to add? +>> +>>Charlie +>> +>> +>>Tom Lane wrote: +>> +>> +>> +>>>"Roman Fail" writes: +>>> +>>> +>>> +>>> +>>>>Thanks to everyone for the quick replies! I'm sure that my lack of +>>>>skill with SQL queries is the main problem. What's strange to me is +>>>>how MSSQL takes my bad queries and makes them look good anyway. It +>>>>must have a real smart planner. +>>>> +>>>> +>>>> +>>>> +>>>I think more likely the issue is that your use of JOIN syntax is forcing +>>>Postgres into a bad plan. MSSQL probably doesn't assign any semantic +>>>significance to the use of "a JOIN b" syntax as opposed to "FROM a, b" +>>>syntax. Postgres does. Whether this is a bug or a feature depends on +>>>your point of view --- but there are folks out there who find it to be +>>>a life-saver. You can find some explanations at +>>>http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/explicit-joins.html +>>> +>>> +>>> +>>> +>>> +>>>>Is it pretty much universally accepted that I should drop all my +>>>>foreign keys? +>>>> +>>>> +>>>> +>>>> +>>>No. They don't have any effect on SELECT performance in Postgres. +>>>They will impact update speed, but that's not your complaint (at the +>>>moment). Don't throw away data integrity protection until you know +>>>you need to. +>>> +>>> regards, tom lane +>>> +>>>---------------------------(end of broadcast)--------------------------- +>>>TIP 4: Don't 'kill -9' the postmaster +>>> +>>> +>>> +>>> +>>-- +>> +>> +>>Charles H. Woloszynski +>> +>>ClearMetrix, Inc. +>>115 Research Drive +>>Bethlehem, PA 18015 +>> +>>tel: 610-419-2210 x400 +>>fax: 240-371-3256 +>>web: www.clearmetrix.com +>> +>> +>> +>> +>> +>> +>>---------------------------(end of broadcast)--------------------------- +>>TIP 2: you can get off all lists at once with the unregister command +>> (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) +>> +>> +>> +> +> +> + +-- + + +Charles H. Woloszynski + +ClearMetrix, Inc. +115 Research Drive +Bethlehem, PA 18015 + +tel: 610-419-2210 x400 +fax: 240-371-3256 +web: www.clearmetrix.com + + + + + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 09:01:22 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C1BE14771F5 + for ; + Fri, 17 Jan 2003 09:01:20 -0500 (EST) +Received: from jefftrout.com (h00a0cc4084e5.ne.client2.attbi.com + [24.128.215.169]) + by postgresql.org (Postfix) with SMTP id 7FC02477272 + for ; + Fri, 17 Jan 2003 09:00:12 -0500 (EST) +Received: (qmail 55163 invoked from network); 17 Jan 2003 14:00:19 -0000 +Received: from unknown (HELO torgo) (threshar@10.10.10.10) + by 10.10.10.10 with SMTP; 17 Jan 2003 14:00:19 -0000 +Date: Fri, 17 Jan 2003 09:00:19 -0500 (EST) +From: Jeff +To: Roman Fail +Cc: Tom Lane , Josh Berkus , + "sszabo@megazone23.bigpanda.com" , + "pgsql-performance@postgresql.org" +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C09@pos_pdc.posportal.com> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/176 +X-Sequence-Number: 823 + +On Thu, 16 Jan 2003, Roman Fail wrote: + +> +> HOWEVER.....look at this: +> EXPLAIN ANALYZE select batchdetailid from batchdetail where batchdetailid = 27321::bigint; +> Index Scan using batchdetail_pkey on batchdetail (cost=0.00..4.13 rows=1 width=8) (actual time=0.03..0.03 rows=1 loops=1) +> Index Cond: (batchdetailid = 27321::bigint) +> Total runtime: 0.07 msec +> + +We had this happen to us - we had a serial8 column (int8) and our query +was straight forward where id = 12345; which ran craptacularly. After +much head banging and cursing I had tried where id = '12345' and it +magically worked. I think the parser is interpreting a "number" to be an +int4 instead of int8. (instead of quotes you can also cast via +12345::int8 like you did) + +Perhaps this should go on the TODO - when one side is an int8 and the +other is a literal number assume the number to be int8 instead of int4? + +------------------------------------------------------------------------------ +Jeff Trout http://www.jefftrout.com/ + Ronald McDonald, with the help of cheese soup, + controls America from a secret volkswagon hidden in the past +------------------------------------------------------------------------------- + + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 09:49:12 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7EECE4763AE + for ; + Fri, 17 Jan 2003 09:49:11 -0500 (EST) +Received: from pos_pdc.posportal.com (unknown [12.158.169.100]) + by postgresql.org (Postfix) with ESMTP id 6DF6147721D + for ; + Fri, 17 Jan 2003 09:48:29 -0500 (EST) +X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3 +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="utf-8" +Content-Transfer-Encoding: base64 +Subject: Implicit casting and JOIN syntax constraints +Date: Fri, 17 Jan 2003 06:48:28 -0800 +Message-ID: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C0B@pos_pdc.posportal.com> +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [PERFORM] 7.3.1 New install, large queries are slow +Thread-Index: AcK+MMt5Ej1+jTmlTVq88jlphHkjhwABVroz +From: "Roman Fail" +To: "Jeff" +Cc: "Tom Lane" , + "Josh Berkus" , , + +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/177 +X-Sequence-Number: 824 + +Pj4gSE9XRVZFUi4uLi4ubG9vayBhdCB0aGlzOg0KPj4gRVhQTEFJTiBBTkFM +WVpFIHNlbGVjdCBiYXRjaGRldGFpbGlkIGZyb20gYmF0Y2hkZXRhaWwgd2hl +cmUgYmF0Y2hkZXRhaWxpZCA9IDI3MzIxOjpiaWdpbnQ7DQo+PiAgSW5kZXgg +U2NhbiB1c2luZyBiYXRjaGRldGFpbF9wa2V5IG9uIGJhdGNoZGV0YWlsICAo +Y29zdD0wLjAwLi40LjEzIHJvd3M9MSB3aWR0aD04KSAoYWN0dWFsIHRpbWU9 +MC4wMy4uMC4wMyByb3dzPTEgbG9vcHM9MSkNCj4+ICAgIEluZGV4IENvbmQ6 +IChiYXRjaGRldGFpbGlkID0gMjczMjE6OmJpZ2ludCkNCj4+ICBUb3RhbCBy +dW50aW1lOiAwLjA3IG1zZWMNCg0KPiBKZWZmIFRyb3V0IHdyb3RlOg0KPiBX +ZSBoYWQgdGhpcyBoYXBwZW4gdG8gdXMgLSB3ZSBoYWQgYSBzZXJpYWw4IGNv +bHVtbiAoaW50OCkgYW5kIG91ciBxdWVyeQ0KPiB3YXMgc3RyYWlnaHQgZm9y +d2FyZCB3aGVyZSBpZCA9IDEyMzQ1OyB3aGljaCByYW4gY3JhcHRhY3VsYXJs +eS4gIEFmdGVyDQo+IG11Y2ggaGVhZCBiYW5naW5nIGFuZCBjdXJzaW5nIEkg +aGFkIHRyaWVkIHdoZXJlIGlkID0gJzEyMzQ1JyBhbmQgaXQNCj4gbWFnaWNh +bGx5IHdvcmtlZC4gSSB0aGluayB0aGUgcGFyc2VyIGlzIGludGVycHJldGlu +ZyBhICJudW1iZXIiIHRvIGJlIGFuDQo+IGludDQgaW5zdGVhZCBvZiBpbnQ4 +LiAgKGluc3RlYWQgb2YgcXVvdGVzIHlvdSBjYW4gYWxzbyBjYXN0IHZpYQ0K +PiAxMjM0NTo6aW50OCBsaWtlIHlvdSBkaWQpDQoNCj4gUGVyaGFwcyB0aGlz +IHNob3VsZCBnbyBvbiB0aGUgVE9ETyAtIHdoZW4gb25lIHNpZGUgaXMgYW4g +aW50OCBhbmQgdGhlDQo+IG90aGVyIGlzIGEgbGl0ZXJhbCBudW1iZXIgYXNz +dW1lIHRoZSBudW1iZXIgdG8gYmUgaW50OCBpbnN0ZWFkIG9mIGludDQ/DQoN +Ckl0IHNlZW1zIHRvIG1lIHRoYXQgdGhpcyBzaG91bGQgYWJzb2x1dGVseSBn +byBvbiB0aGUgVE9ETyBsaXN0LiAgV2h5IGRvZXMgdGhlIHBsYW5uZXIgcmVx +dWlyZSBhbiBleHBsaWNpdCBjYXN0IHdoZW4gdGhlIGltcGxpY2l0IGNhc3Qg +aXMgc28gb2J2aW91cz8gIERvZXMgT3JhY2xlIGRvIHRoaXM/ICBJIGNhbiBh +c3N1cmUgeW91IHRoYXQgTVNTUUwgZG9lcyBub3QuICANCiANCklmIGdldHRp +bmcgbW9yZSBwZW9wbGUgdG8gbWlncmF0ZSB0byBQb3N0Z3JlU1FMIGlzIGEg +bWFqb3IgZ29hbCB0aGVzZSBkYXlzLCBpdCdzIGdvdCB0byBiZSByZWxhdGl2 +ZWx5IGVhc3kuICBJIHRoaW5rIHRoYXQgYWxtb3N0IGV2ZXJ5b25lIGNvbWlu +ZyBmcm9tIGEgTVNTUUwgb3IgQWNjZXNzIGJhY2tncm91bmQgaXMgZ29pbmcg +dG8gaGF2ZSBiaWcgcHJvYmxlbXMgd2l0aCB0aGlzLiAgQW5kIHRoZSBvdGhl +ciBpc3N1ZSBvZiB0aGUgSk9JTiBzeW50YXggY29uc3RyYWluaW5nIHRoZSBw +bGFubmVyIC0geW91J3ZlIGdvdCB0byBiZSBhYmxlIHRvIHR1cm4gdGhhdCBv +ZmYgdG9vLiAgSSd2ZSBiZWVuIHdyaXRpbmcgU1FMIHF1ZXJpZXMgZm9yIDEw +IHllYXJzIGluIEZveFBybywgQWNjZXNzLCBTUUwgU2VydmVyLCBNeVNRTCwg +YW5kIFN5YmFzZS4gIEkgaGF2ZSBuZXZlciBjb21lIGFjcm9zcyB0aGlzIHZl +cnkgY29uZnVzaW5nICJmZWF0dXJlIiB1bnRpbCBub3cuICANCiANCkhvdyBk +byB3ZSBnbyBhYm91dCB2b3RpbmcgYW4gaXNzdWUgb250byB0aGUgVE9ETyBs +aXN0PyAgVGhlc2UgdHdvIGdldCBteSB2b3RlIGZvciBzdXJlIQ0KIA0KUm9t +YW4NCg== + +From pgsql-performance-owner@postgresql.org Fri Jan 17 09:57:02 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E2D814762EB + for ; + Fri, 17 Jan 2003 09:57:01 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 50161476199 + for ; + Fri, 17 Jan 2003 09:57:01 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0HEv45u011752; + Fri, 17 Jan 2003 09:57:04 -0500 (EST) +To: Timur Irmatov +Cc: pgsql-performance@postgresql.org +Subject: Re: index usage +In-reply-to: <10597430257.20030117164800@sarkor.com> +References: <10597430257.20030117164800@sarkor.com> +Comments: In-reply-to Timur Irmatov + message dated "Fri, 17 Jan 2003 16:48:00 +0500" +Date: Fri, 17 Jan 2003 09:57:04 -0500 +Message-ID: <11751.1042815424@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/178 +X-Sequence-Number: 825 + +Timur Irmatov writes: +> Limit (cost=0.00..0.19 rows=1 width=6) (actual time=0.43..0.43 rows=0 loops=1) +> -> Index Scan using timeindex on mediumstats (cost=0.00..2898.96 rows=15185 width=6) (actual time=0.42..0.42 rows=0 loops=1) + +The planner has absolutely no clue about the behavior of your function, +and so its estimate of the number of rows matched is way off, leading to +a poor estimate of the cost of an indexscan. There is not much to be +done about this in the current system (though I've speculated about the +possibility of computing statistics for functional indexes). + +Just out of curiosity, why don't you lose all this year/month/day stuff +and use a timestamp column? Less space, more functionality. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 17 10:09:30 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 957E04773B2 + for ; + Fri, 17 Jan 2003 10:09:28 -0500 (EST) +Received: from mail.sarkor.com (unknown [81.95.224.36]) + by postgresql.org (Postfix) with SMTP id 46FDA4772E0 + for ; + Fri, 17 Jan 2003 10:08:04 -0500 (EST) +Received: (qmail 30518 invoked by uid 507); 17 Jan 2003 15:08:04 -0000 +Received: from thor@sarkor.com by mail.sarkor.com by uid 504 with + qmail-scanner-1.14 (clamscan: 0.51. Clear:. + Processed in 0.814302 secs); 17 Jan 2003 15:08:04 -0000 +Received: from unknown (HELO timur) (81.95.224.66) + by mail.sarkor.com with SMTP; 17 Jan 2003 15:08:03 -0000 +Date: Fri, 17 Jan 2003 20:08:14 +0500 +From: Timur Irmatov +X-Mailer: The Bat! (v1.61) +Reply-To: Timur Irmatov +X-Priority: 3 (Normal) +Message-ID: <87109443711.20030117200814@sarkor.com> +To: Tom Lane +Cc: pgsql-performance@postgresql.org +Subject: Re: index usage +In-Reply-To: <11751.1042815424@sss.pgh.pa.us> +References: <10597430257.20030117164800@sarkor.com> + <11751.1042815424@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/179 +X-Sequence-Number: 826 + +TL> Timur Irmatov writes: +>> Limit (cost=0.00..0.19 rows=1 width=6) (actual time=0.43..0.43 rows=0 loops=1) +>> -> Index Scan using timeindex on mediumstats (cost=0.00..2898.96 rows=15185 width=6) (actual time=0.42..0.42 rows=0 loops=1) + +TL> The planner has absolutely no clue about the behavior of your function, +TL> and so its estimate of the number of rows matched is way off, leading to +TL> a poor estimate of the cost of an indexscan. There is not much to be +TL> done about this in the current system (though I've speculated about the +TL> possibility of computing statistics for functional indexes). + +you're absolutely right. +thanks. + +TL> Just out of curiosity, why don't you lose all this year/month/day stuff +TL> and use a timestamp column? Less space, more functionality. + +:-) +Well, I've a seen a lot of people on pgsql-general mailing list with +problems with dates, timestamps, and I was just scared of using +PostreSQL date and time types and functions.. + +May be, I should just try it myself before doing it other way... + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 10:11:31 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3FCD64772A6 + for ; + Fri, 17 Jan 2003 10:11:30 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id D6555477264 + for ; + Fri, 17 Jan 2003 10:11:19 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0HFBH5u011881; + Fri, 17 Jan 2003 10:11:19 -0500 (EST) +To: Jeff +Cc: Roman Fail , Josh Berkus , + "sszabo@megazone23.bigpanda.com" , + "pgsql-performance@postgresql.org" +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: +References: +Comments: In-reply-to Jeff + message dated "Fri, 17 Jan 2003 09:00:19 -0500" +Date: Fri, 17 Jan 2003 10:11:17 -0500 +Message-ID: <11880.1042816277@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/180 +X-Sequence-Number: 827 + +Jeff writes: +> Perhaps this should go on the TODO - when one side is an int8 and the +> other is a literal number assume the number to be int8 instead of int4? + +It's been on TODO for so long that it's buried near the bottom. + +* Allow SELECT * FROM tab WHERE int2col = 4 to use int2col index, int8, + float4, numeric/decimal too [optimizer] + +This behavior interacts with enough other stuff that we can't just +change it willy-nilly. See many past discussions in the pghackers +archives if you want details. A recent example of a promising-looking +fix crashing and burning is +http://fts.postgresql.org/db/mw/msg.html?mid=1357121 + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 17 10:16:45 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B9614476813 + for ; + Fri, 17 Jan 2003 10:16:44 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id CEB5D477361 + for ; + Fri, 17 Jan 2003 10:15:29 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18ZYDW-0006FL-00 + for ; Fri, 17 Jan 2003 10:15:34 -0500 +Date: Fri, 17 Jan 2003 10:15:34 -0500 +From: Andrew Sullivan +To: "pgsql-performance@postgresql.org" +Subject: Re: 7.3.1 New install, large queries are slow +Message-ID: <20030117101534.A23422@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + "pgsql-performance@postgresql.org" +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C09@pos_pdc.posportal.com> + +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: ; + from threshar@torgo.978.org on Fri, Jan 17, 2003 at 09:00:19AM + -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/181 +X-Sequence-Number: 828 + +On Fri, Jan 17, 2003 at 09:00:19AM -0500, Jeff wrote: +> Perhaps this should go on the TODO - when one side is an int8 and the +> other is a literal number assume the number to be int8 instead of int4? + +Actually, this is a broader problem having to do with type coercion. +There are a couple of TODO items which refer to this, it looks to me, +but in any case there has been _plenty_ of discussion on -general and +-hackers about what's wrong here. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 10:33:42 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8FC86475EBF + for ; + Fri, 17 Jan 2003 10:33:37 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 66243475E91 + for ; + Fri, 17 Jan 2003 10:33:36 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18ZYV3-0006Ug-00 + for ; Fri, 17 Jan 2003 10:33:41 -0500 +Date: Fri, 17 Jan 2003 10:33:41 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: index usage +Message-ID: <20030117103341.E23422@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <10597430257.20030117164800@sarkor.com> + <11751.1042815424@sss.pgh.pa.us> + <87109443711.20030117200814@sarkor.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <87109443711.20030117200814@sarkor.com>; + from thor@sarkor.com on Fri, Jan 17, 2003 at 08:08:14PM +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/182 +X-Sequence-Number: 829 + +On Fri, Jan 17, 2003 at 08:08:14PM +0500, Timur Irmatov wrote: +> Well, I've a seen a lot of people on pgsql-general mailing list with +> problems with dates, timestamps, and I was just scared of using +> PostreSQL date and time types and functions.. + +What problems? The only problems I know of with datetime stuff are +on those machines with the utterly silly glibc hobbling, and even +that has been worked around in recent releases. I think the date and +time handling in PostgreSQL beats most systems. It just works, and +handles all the time-zone conversions for you and everything. + +A + + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 10:41:10 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 387C7475F39 + for ; + Fri, 17 Jan 2003 10:41:06 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id A1522475EBF + for ; + Fri, 17 Jan 2003 10:41:05 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18ZYcI-0006cl-00 + for ; Fri, 17 Jan 2003 10:41:10 -0500 +Date: Fri, 17 Jan 2003 10:41:10 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: Implicit casting and JOIN syntax constraints +Message-ID: <20030117104110.G23422@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C0B@pos_pdc.posportal.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C0B@pos_pdc.posportal.com>; + from rfail@posportal.com on Fri, Jan 17, 2003 at 06:48:28AM -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/183 +X-Sequence-Number: 830 + +On Fri, Jan 17, 2003 at 06:48:28AM -0800, Roman Fail wrote: +> It seems to me that this should absolutely go on the TODO list. +> Why does the planner require an explicit cast when the implicit +> cast is so obvious? Does Oracle do this? I can assure you that +> MSSQL does not. + +The reason it happens is because of the flexible datatype system in +PostgreSQL. Because it's easy to add a datatype, you pay in other +ways. The problem is coming up with a nice, clean set of rules for +coercion. See the link that Tom Lane posted, and the thousands of +other discussions around this in the archives. Yes, it's a pain. +Everyone knows that. A complete solution is what's missing. + +> too. I've been writing SQL queries for 10 years in FoxPro, Access, +> SQL Server, MySQL, and Sybase. I have never come across this very +> confusing "feature" until now. + +Well, there are differences between every system. Indeed, the "SQL" +of MySQL is so far from anything resembling the standard that one +could argue it doesn't comply at all. You're right that it means a +steep learning curve for some things, and the problems can be +frustrating. But that doesn't mean you want to throw the baby out +with the bathwater. The ability to give the planner hints through +the JOIN syntax is, frankly, a real help when you're faced with +certain kinds of performance problems. Some systems don't give you a +knob to tune there at all. Is it different from other systems? +Sure. Is that automatically a reason to pitch the feature? No. +(Further discussion of this probably belongs on -general, if +anywhere, by the way.) + +A + +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 12:14:36 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 37D2C475EAE + for ; + Fri, 17 Jan 2003 12:08:52 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 36CA4475E60 + for ; + Fri, 17 Jan 2003 12:08:51 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2317350; Fri, 17 Jan 2003 09:08:54 -0800 +From: "Josh Berkus" +Subject: Re: 7.3.1 New install, large queries are slow +To: Tom Lane , "Roman Fail" +Cc: sszabo@megazone23.bigpanda.com, pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Fri, 17 Jan 2003 09:08:54 -0800 +Message-ID: +In-Reply-To: <4981.1042783570@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/184 +X-Sequence-Number: 831 + +Tom, + +> > shared_buffers = 131072 +> +> Yipes! Try about a tenth that much. Or less. + +Why? He has 4GB RAM on the machine. + +-Josh Berkus + +From pgsql-performance-owner@postgresql.org Fri Jan 17 12:33:56 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 506F84764FA + for ; + Fri, 17 Jan 2003 12:33:52 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 2544547743A + for ; + Fri, 17 Jan 2003 12:28:30 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP + id 465BD1557D; Fri, 17 Jan 2003 12:28:35 -0500 (EST) +Date: Fri, 17 Jan 2003 12:28:35 -0500 +Subject: Strange Join question +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +From: Noah Silverman +To: pgsql-performance@postgresql.org +Content-Transfer-Encoding: 7bit +In-Reply-To: +Message-Id: <1B62AFA4-2A41-11D7-8B2D-000393AA8F3C@allresearch.com> +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/185 +X-Sequence-Number: 832 + +Hi, + +I have a challenging (for me) SQL question: + +Two tables +(Note: these are fictitious, the real tables actually make sense, so no +need to re-design our table structure) + +Table 1 +id | name | count +------------------------ +1 | foo | 10 +1 | foo | 20 +2 | bar | 100 + + +Table 2 +id | f1 | f2 | t1ref +----------------------- +1 | 10 | 20 | 1 +2 | 50 | 40 | 2 + + +The question: + +I want to do the following select: +select table2.f1, table1.name from table1,table2 where table1.id = +table 2.id and table2.id = 2; + +The problem is that I really only need the name from table2 returned +once. With this query, I get two records back. Clearly this is +because of the join that I am doing. Is there a different way to +perform this join, so that I only get back ONE record from table1 that +matches? + +Thanks, + +-Noah + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 12:37:13 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 690044772A6 + for ; + Fri, 17 Jan 2003 12:37:09 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id A026F4773F7 + for ; + Fri, 17 Jan 2003 12:33:18 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0HHXB5u013110; + Fri, 17 Jan 2003 12:33:11 -0500 (EST) +To: "Josh Berkus" +Cc: "Roman Fail" , + sszabo@megazone23.bigpanda.com, pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: +References: +Comments: In-reply-to "Josh Berkus" + message dated "Fri, 17 Jan 2003 09:08:54 -0800" +Date: Fri, 17 Jan 2003 12:33:11 -0500 +Message-ID: <13109.1042824791@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/186 +X-Sequence-Number: 833 + +"Josh Berkus" writes: +>>> shared_buffers = 131072 +>> +>> Yipes! Try about a tenth that much. Or less. + +> Why? He has 4GB RAM on the machine. + +I think a gig of shared buffers is overkill no matter what. + +One reason not to crank up shared_buffers "just because you can" is that +there are operations (such as CHECKPOINT) that have to scan through all +the buffers, linearly. I don't *think* any of these are in +performance-critical paths, but nonetheless you're wasting CPU. I trust +the kernel to manage a huge number of buffers efficiently more than I +trust Postgres. + +There's another issue, which is somewhat platform-dependent; I'm not +sure if it applies to whatever OS Roman is using. But if you have a +machine where SysV shared memory is not locked into RAM, then a huge +shared buffer arena creates the probability that some of it will be +touched seldom enough that the kernel will decide to swap it out. When +that happens, you *really* pay through the nose --- a page that you +might have been able to get from kernel cache without incurring I/O will +now certainly cost you I/O to touch. It's even worse if the buffer +contained a dirty page at the time it was swapped out --- now that page +is going to require being read back in and written out again, a net cost +of three I/Os where there should have been one. Bottom line is that +shared_buffers should be kept small enough that the space all looks like +a hot spot to the kernel's memory allocation manager. + +In short, I believe in keeping shared_buffers relatively small --- one +to ten thousand seems like the right ballpark --- and leaving the kernel +to allocate the rest of RAM as kernel disk cache. + +I have been thinking recently about proposing that we change the factory +default shared_buffers to 1000, which if this line of reasoning is +correct would eliminate the need for average installations to tune it. +The reason the default is 64 is that on some older Unixen, the default +SHMMAX is only one meg --- but it's been a long time since our default +shared memory request was less than a meg anyway, because of bloat in +other components of shared memory. It's probably time to change the +default to something more reasonable from a performance standpoint, and +put some burden on users of older Unixen to either reduce the setting +or fix their SHMMAX parameter. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 17 12:51:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 0A110476987; Fri, 17 Jan 2003 12:51:04 -0500 (EST) +Received: from fddlnint05.fds.com (fddlnint05.fds.com [208.15.91.52]) + by postgresql.org (Postfix) with ESMTP + id 3B6D4477416; Fri, 17 Jan 2003 12:43:01 -0500 (EST) +Subject: Re: Strange Join question +To: "Noah Silverman +Cc: pgsql-performance@postgresql.org, + pgsql-performance-owner@postgresql.org +X-Mailer: Lotus Notes Release 5.0.4 June 8, 2000 +Message-ID: +From: "Patrick Hatcher" +Date: Fri, 17 Jan 2003 09:38:42 -0800 +X-MIMETrack: Serialize by Router on FDDLNINT05/FSG/SVR/FDD(Release 5.0.4 |June + 8, 2000) at 01/17/2003 12:40:07 PM +MIME-Version: 1.0 +Content-type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/187 +X-Sequence-Number: 834 + + +Can you do +select table2.f1, table1.name +from table1,table2 +where table1.id = +table 2.id and table2.id = 2 +GROUP BY table2.f1, table1.name; + + +Patrick Hatcher +Macys.Com +Legacy Integration Developer +415-422-1610 office +HatcherPT - AIM + + + + + + Noah Silverman + To: pgsql-performance@postgresql.org + Sent by: cc: + pgsql-performance-owner@post Subject: [PERFORM] Strange Join question + gresql.org + + + 01/17/2003 09:28 AM + + + + + + +Hi, + +I have a challenging (for me) SQL question: + +Two tables +(Note: these are fictitious, the real tables actually make sense, so no +need to re-design our table structure) + +Table 1 +id | name | count +------------------------ +1 | foo | 10 +1 | foo | 20 +2 | bar | 100 + + +Table 2 +id | f1 | f2 | t1ref +----------------------- +1 | 10 | 20 | 1 +2 | 50 | 40 | 2 + + +The question: + +I want to do the following select: +select table2.f1, table1.name from table1,table2 where table1.id = +table 2.id and table2.id = 2; + +The problem is that I really only need the name from table2 returned +once. With this query, I get two records back. Clearly this is +because of the join that I am doing. Is there a different way to +perform this join, so that I only get back ONE record from table1 that +matches? + +Thanks, + +-Noah + + +---------------------------(end of broadcast)--------------------------- +TIP 2: you can get off all lists at once with the unregister command + (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) + + + + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 12:56:13 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 04144477478 + for ; + Fri, 17 Jan 2003 12:56:06 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP id 91EA9477425 + for ; + Fri, 17 Jan 2003 12:52:38 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id h0HHqLR27486; + Fri, 17 Jan 2003 12:52:21 -0500 (EST) +From: Bruce Momjian +Message-Id: <200301171752.h0HHqLR27486@candle.pha.pa.us> +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <13109.1042824791@sss.pgh.pa.us> +To: Tom Lane +Date: Fri, 17 Jan 2003 12:52:21 -0500 (EST) +Cc: Josh Berkus , + Roman Fail , sszabo@megazone23.bigpanda.com, + pgsql-performance@postgresql.org +X-Mailer: ELM [version 2.4ME+ PL99 (25)] +MIME-Version: 1.0 +Content-Transfer-Encoding: 7bit +Content-Type: text/plain; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/188 +X-Sequence-Number: 835 + +Tom Lane wrote: +> "Josh Berkus" writes: +> >>> shared_buffers = 131072 +> >> +> >> Yipes! Try about a tenth that much. Or less. +> +> > Why? He has 4GB RAM on the machine. +> +> I think a gig of shared buffers is overkill no matter what. +> +> One reason not to crank up shared_buffers "just because you can" is that +> there are operations (such as CHECKPOINT) that have to scan through all +> the buffers, linearly. I don't *think* any of these are in +> performance-critical paths, but nonetheless you're wasting CPU. I trust +> the kernel to manage a huge number of buffers efficiently more than I +> trust Postgres. +> +> There's another issue, which is somewhat platform-dependent; I'm not +> sure if it applies to whatever OS Roman is using. But if you have a +> machine where SysV shared memory is not locked into RAM, then a huge +> shared buffer arena creates the probability that some of it will be +> touched seldom enough that the kernel will decide to swap it out. When +> that happens, you *really* pay through the nose --- a page that you +> might have been able to get from kernel cache without incurring I/O will +> now certainly cost you I/O to touch. It's even worse if the buffer +> contained a dirty page at the time it was swapped out --- now that page +> is going to require being read back in and written out again, a net cost +> of three I/Os where there should have been one. Bottom line is that +> shared_buffers should be kept small enough that the space all looks like +> a hot spot to the kernel's memory allocation manager. + +Just as a data point, I believe other database systems recommend very +large shared memory areas if a lot of data is being accessed. I seem to +remember Informix doing that. + +-- + 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 Jan 17 13:03:30 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5A0754763AE + for ; + Fri, 17 Jan 2003 13:03:25 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id B65164773A6 + for ; + Fri, 17 Jan 2003 12:59:39 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18ZamJ-0000pY-00 + for ; Fri, 17 Jan 2003 12:59:39 -0500 +Date: Fri, 17 Jan 2003 12:59:39 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +Message-ID: <20030117125939.J23422@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: + <13109.1042824791@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <13109.1042824791@sss.pgh.pa.us>; + from tgl@sss.pgh.pa.us on Fri, Jan 17, 2003 at 12:33:11PM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/189 +X-Sequence-Number: 836 + +On Fri, Jan 17, 2003 at 12:33:11PM -0500, Tom Lane wrote: +> One reason not to crank up shared_buffers "just because you can" is that +> there are operations (such as CHECKPOINT) that have to scan through all +> the buffers, linearly. I don't *think* any of these are in +> performance-critical paths, but nonetheless you're wasting CPU. I trust +> the kernel to manage a huge number of buffers efficiently more than I +> trust Postgres. + +For what it's worth, we have exactly that experience on our Sun +E4500s. I had machines with 12 gig I was testing on, and I increased +the buffers to 2 Gig, because truss was showing us some sluggishness +in the system was tripping on the system call to get a page. It was +satisifed right away by the kernel's cache, but the system call was +still the most expensive part of the operation. + +After we'd increased the shared buffers, however, performance +_degraded_ considerably. It now spent all its time instead managing +the huge shared buffer, and the cost of that was much worse than the +cost of the system call. + +So it is extremely dependent on the efficiency of PostgreSQL's use of +shared memory as compared to the efficiency of the system call. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Fri Jan 17 13:04:02 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 452F9476726 + for ; + Fri, 17 Jan 2003 13:03:58 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 16E93477395 + for ; + Fri, 17 Jan 2003 13:01:19 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0HI195u013373; + Fri, 17 Jan 2003 13:01:09 -0500 (EST) +To: Bruce Momjian +Cc: Josh Berkus , + Roman Fail , sszabo@megazone23.bigpanda.com, + pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: <200301171752.h0HHqLR27486@candle.pha.pa.us> +References: <200301171752.h0HHqLR27486@candle.pha.pa.us> +Comments: In-reply-to Bruce Momjian + message dated "Fri, 17 Jan 2003 12:52:21 -0500" +Date: Fri, 17 Jan 2003 13:01:09 -0500 +Message-ID: <13372.1042826469@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/190 +X-Sequence-Number: 837 + +Bruce Momjian writes: +> Just as a data point, I believe other database systems recommend very +> large shared memory areas if a lot of data is being accessed. I seem to +> remember Informix doing that. + +Yeah, but isn't that theory a hangover from pre-Unix operating systems? +In all modern Unixen, you can expect the kernel to make use of any spare +RAM for disk buffer cache --- and that behavior makes it pointless for +Postgres to try to do large amounts of its own buffering. + +Having a page in our own buffer instead of kernel buffer saves a context +swap to access the page, but it doesn't save I/O, so the benefit is a +lot less than you might think. I think there's seriously diminishing +returns in pushing shared_buffers beyond a few thousand, and once you +get to the point where it distorts the kernel's ability to manage +memory for processes, you're really shooting yourself in the foot. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 17 14:04:06 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4B1BA476939 + for ; + Fri, 17 Jan 2003 13:41:54 -0500 (EST) +Received: from jefftrout.com (h00a0cc4084e5.ne.client2.attbi.com + [24.128.215.169]) + by postgresql.org (Postfix) with SMTP id 0B4884773E0 + for ; + Fri, 17 Jan 2003 13:39:38 -0500 (EST) +Received: (qmail 56672 invoked from network); 17 Jan 2003 18:39:42 -0000 +Received: from unknown (HELO torgo) (threshar@10.10.10.10) + by 10.10.10.10 with SMTP; 17 Jan 2003 18:39:42 -0000 +Date: Fri, 17 Jan 2003 13:39:41 -0500 (EST) +From: Jeff +To: Tom Lane +Cc: Bruce Momjian , + Josh Berkus , Roman Fail , + "sszabo@megazone23.bigpanda.com" , + "pgsql-performance@postgresql.org" +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <13372.1042826469@sss.pgh.pa.us> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/191 +X-Sequence-Number: 838 + +On Fri, 17 Jan 2003, Tom Lane wrote: + +> +> Yeah, but isn't that theory a hangover from pre-Unix operating systems? +> In all modern Unixen, you can expect the kernel to make use of any spare +> RAM for disk buffer cache --- and that behavior makes it pointless for +> Postgres to try to do large amounts of its own buffering. +> + +Informix, oracle, etc all do raw device access bypassing the kernels +buffering, etc. So they need heaping gobules of memory to do the same +thing the kernel does.. but since they know the exact patterns of data and +how things will be done they can fine tune their buffer caches to get much +better performance than the kernel (15-20% in informix's case) since the +kernel needs to be a "works good generally" + +probably the desire to crank that up stems from using those other db's I +know I used to do that with pgsql. (Ahh, I crank that setting up through +the roof on informix, I'll do the same with pg) + +perhaps a FAQ entry or comment in the shipped config about it? +I think if people realize it isn't quite the same as what it does in +oracle/informix/etc then they'll be less inclined to cranking it. + +------------------------------------------------------------------------------ +Jeff Trout http://www.jefftrout.com/ + Ronald McDonald, with the help of cheese soup, + controls America from a secret volkswagon hidden in the past +------------------------------------------------------------------------------- + + + +From pgsql-general-owner@postgresql.org Fri Jan 17 14:39:13 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 925F1475957 + for ; + Fri, 17 Jan 2003 14:39:07 -0500 (EST) +Received: from polaris.pinpointresearch.com (66-7-238-176.cust.telepacific.net + [66.7.238.176]) by postgresql.org (Postfix) with ESMTP id BC051477378 + for ; + Fri, 17 Jan 2003 14:37:30 -0500 (EST) +Received: from there (66-7-238-179.cust.telepacific.net [66.7.238.179]) + by polaris.pinpointresearch.com (Postfix) with SMTP id 1CFCB103E5 + for ; + Fri, 17 Jan 2003 11:37:26 -0800 (PST) +Content-Type: text/plain; + charset="iso-8859-15" +From: Steve Crawford +Organization: Pinpoint Research +To: pgsql-general@postgresql.org +Subject: Terrible performance on wide selects +Date: Fri, 17 Jan 2003 11:37:26 -0800 +X-Mailer: KMail [version 1.3.1] +MIME-Version: 1.0 +Content-Transfer-Encoding: 8bit +Message-Id: <20030117193726.1CFCB103E5@polaris.pinpointresearch.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/659 +X-Sequence-Number: 35780 + +I have a table which is rather wide (~800 columns) and consists of a few +columns of identifying data (run time, channel and such) and up to several +hundred columns of collected data (no, normalization does not suggest putting +collected data in another table - collected item 1 always corresponds to +collected item 1 but is completely different than item 3). + +My test table is very short (62 rows) but in production would grow by several +thousand rows per day. Unfortunately if my test data is correct, performance +on wide selects is so bad that it will render the system unusable. + +Here's the test. I have created two versions of the table - one stores the +collected data in an array of text and the other stores the data in +individual columns, no joins, no indexes. Times are averages of many runs - +the times varied very little and the data is small enough that I'm sure it +was served from RAM. Postgres CPU utilization observed on the longer runs was +98-99%. Changing the output format didn't seem to change things significantly. + +Times for selecting all the columns in the table: +select * from columnversion; +8,000 ms + +select * from arrayversion; +110 ms + +select * from arraytocolumnview (data in the array version but converted to +columns in the view) +10,000 ms + +Times to select a single column in a table: +select runstarttime from columversion; +32 ms + +select runstarttime from arrayversion; +6 ms + +So the question is, does it seem reasonable that a query on fundamentally +identical data should take 70-90 times as long when displayed as individual +columns vs. when output as a raw array and, more imporantly, what can I do to +get acceptable performance on this query? + +Cheers, +Steve + +From pgsql-general-owner@postgresql.org Fri Jan 17 18:18:11 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A5F8C4773E2 + for ; + Fri, 17 Jan 2003 18:18:05 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 92DB2476A5B + for ; + Fri, 17 Jan 2003 18:12:24 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0HN6q5u019507; + Fri, 17 Jan 2003 18:06:54 -0500 (EST) +To: Steve Crawford +Cc: pgsql-general@postgresql.org +Subject: Re: Terrible performance on wide selects +In-reply-to: <20030117193726.1CFCB103E5@polaris.pinpointresearch.com> +References: <20030117193726.1CFCB103E5@polaris.pinpointresearch.com> +Comments: In-reply-to Steve Crawford + message dated "Fri, 17 Jan 2003 11:37:26 -0800" +Date: Fri, 17 Jan 2003 18:06:52 -0500 +Message-ID: <19506.1042844812@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/671 +X-Sequence-Number: 35792 + +Steve Crawford writes: +> So the question is, does it seem reasonable that a query on fundamentally +> identical data should take 70-90 times as long when displayed as individual +> columns vs. when output as a raw array and, more imporantly, what can I do to +> get acceptable performance on this query? + +There are undoubtedly some places that are O(N^2) in the number of +targetlist items. Feel free to do some profiling to identify them. +It probably won't be real hard to fix 'em once identified. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 17 23:51:27 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E50A0476324 + for ; + Fri, 17 Jan 2003 23:51:10 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 9F91C47680A + for ; + Fri, 17 Jan 2003 23:50:10 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0I4nV5u021624; + Fri, 17 Jan 2003 23:49:34 -0500 (EST) +To: Jeff +Cc: Bruce Momjian , + Josh Berkus , Roman Fail , + "sszabo@megazone23.bigpanda.com" , + "pgsql-performance@postgresql.org" +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: +References: +Comments: In-reply-to Jeff + message dated "Fri, 17 Jan 2003 13:39:41 -0500" +Date: Fri, 17 Jan 2003 23:49:31 -0500 +Message-ID: <21623.1042865371@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/192 +X-Sequence-Number: 839 + +Jeff writes: +> On Fri, 17 Jan 2003, Tom Lane wrote: +>> Yeah, but isn't that theory a hangover from pre-Unix operating systems? + +> Informix, oracle, etc all do raw device access bypassing the kernels +> buffering, etc. So they need heaping gobules of memory to do the same +> thing the kernel does.. + +D'oh, I believe Jeff's put his finger on it. You need lotsa RAM if you +are trying to bypass the OS. But Postgres would like to work with the +OS, not bypass it. + +> but since they know the exact patterns of data and +> how things will be done they can fine tune their buffer caches to get much +> better performance than the kernel (15-20% in informix's case) since the +> kernel needs to be a "works good generally" + +They go to all that work for 15-20% ??? Remind me not to follow that +primrose path. I can think of lots of places where we can buy 20% for +less work than implementing (and maintaining) our own raw-device access +layer. + +> perhaps a FAQ entry or comment in the shipped config about it? +> I think if people realize it isn't quite the same as what it does in +> oracle/informix/etc then they'll be less inclined to cranking it. + +Good thought. But we do need to set the default to something a tad +more realistic-for-2003 than 64 buffers ... + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Sat Jan 18 00:38:28 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BC22D475AD7 + for ; + Sat, 18 Jan 2003 00:29:47 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 072814758E1 + for ; + Sat, 18 Jan 2003 00:29:47 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030118052952.GMJC8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Sat, 18 Jan 2003 00:29:52 -0500 +Subject: x86-64 and PostgreSQL +From: Ron Johnson +To: PgSQL Performance ML +Content-Type: text/plain +Organization: +Message-Id: <1042867764.889.181.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 17 Jan 2003 23:29:25 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/193 +X-Sequence-Number: 840 + +Hi, + +Will there be any advantages to running Pg on a 64-bit CPU rather +than 32-bit? + +The recent discussions in the "7.3.1 New install, large queries are +slow" thread make me think not, since Pg says that the OS can manage +buffers better: + +Yeah, but isn't that theory a hangover from pre-Unix operating systems? +In all modern Unixen, you can expect the kernel to make use of any spare +RAM for disk buffer cache --- and that behavior makes it pointless for +Postgres to try to do large amounts of its own buffering. + +Having a page in our own buffer instead of kernel buffer saves a context +swap to access the page, but it doesn't save I/O, so the benefit is a +lot less than you might think. I think there's seriously diminishing +returns in pushing shared_buffers beyond a few thousand, and once you +get to the point where it distorts the kernel's ability to manage +memory for processes, you're really shooting yourself in the foot. + + +Also, would int8 then become a more "natural" default integer, rather +than the int4 that all of us millions of i386, PPC & Sparc users use? + +Thanks, +Ron +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Sat Jan 18 02:07:38 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 252114763C3 + for ; + Sat, 18 Jan 2003 01:44:38 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 5859C47636B + for ; + Sat, 18 Jan 2003 01:44:37 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0I6iZ5u022329; + Sat, 18 Jan 2003 01:44:36 -0500 (EST) +To: Ron Johnson +Cc: PgSQL Performance ML +Subject: Re: x86-64 and PostgreSQL +In-reply-to: <1042867764.889.181.camel@haggis> +References: <1042867764.889.181.camel@haggis> +Comments: In-reply-to Ron Johnson + message dated "17 Jan 2003 23:29:25 -0600" +Date: Sat, 18 Jan 2003 01:44:35 -0500 +Message-ID: <22328.1042872275@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/195 +X-Sequence-Number: 842 + +Ron Johnson writes: +> Will there be any advantages to running Pg on a 64-bit CPU rather +> than 32-bit? + +Not so's you'd notice. PG is designed to be cross-platform, and at +the moment that means 32-bit-centric. There's been occasional talk +of improving the performance of float8 and int8 types on 64-bit +machines, but so far it's only idle talk; and in any case I think +that performance improvements for those two datatypes wouldn't have +much effect for average applications. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Sat Jan 18 02:07:30 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1A0C6475AD7 + for ; + Sat, 18 Jan 2003 01:55:09 -0500 (EST) +Received: from lakemtao02.cox.net (lakemtao02.cox.net [68.1.17.243]) + by postgresql.org (Postfix) with ESMTP id 824EA474E53 + for ; + Sat, 18 Jan 2003 01:55:08 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao02.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030118065508.GYLM6744.lakemtao02.cox.net@[192.168.1.1]> + for ; + Sat, 18 Jan 2003 01:55:08 -0500 +Subject: Re: x86-64 and PostgreSQL +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <22328.1042872275@sss.pgh.pa.us> +References: <1042867764.889.181.camel@haggis> <22328.1042872275@sss.pgh.pa.us> +Content-Type: text/plain +Organization: +Message-Id: <1042872864.7792.43.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 18 Jan 2003 00:55:04 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/194 +X-Sequence-Number: 841 + +On Sat, 2003-01-18 at 00:44, Tom Lane wrote: +> Ron Johnson writes: +> > Will there be any advantages to running Pg on a 64-bit CPU rather +> > than 32-bit? +> +> Not so's you'd notice. PG is designed to be cross-platform, and at +> the moment that means 32-bit-centric. There's been occasional talk +> of improving the performance of float8 and int8 types on 64-bit +> machines, but so far it's only idle talk; and in any case I think +> that performance improvements for those two datatypes wouldn't have +> much effect for average applications. + +That's kinda what I expected. + +The ability to /relatively/ inexpensively get a box chock full of +RAM couldn't hurt, though... + +Putting a 12GB database on a box with 8GB RAM has to make it run +pretty fast. (As long as you aren't joining mismatched types!!!) + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Sat Jan 18 02:39:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id ABCCF474E53 + for ; + Sat, 18 Jan 2003 02:39:49 -0500 (EST) +Received: from zigo.dhs.org (as2-4-3.an.g.bonet.se [194.236.34.191]) + by postgresql.org (Postfix) with ESMTP id 9663E475AD7 + for ; + Sat, 18 Jan 2003 02:39:48 -0500 (EST) +Received: from localhost (db@localhost) + by zigo.dhs.org (8.11.6/8.11.6) with ESMTP id h0I7d8S02797; + Sat, 18 Jan 2003 08:39:09 +0100 +Date: Sat, 18 Jan 2003 08:39:08 +0100 (CET) +From: =?ISO-8859-1?Q?Dennis_Bj=F6rklund?= +To: Roman Fail +Cc: Josh Berkus , + , +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C09@pos_pdc.posportal.com> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/196 +X-Sequence-Number: 843 + +On Thu, 16 Jan 2003, Roman Fail wrote: + +> It sort of feels like a magic moment. I went back and looked through a +> lot of the JOIN columns and found that I was mixing int4 with int8 in a +> lot of them. + +There is note about it in the docs: + +http://www.postgresql.org/idocs/index.php?datatype.html#DATATYPE-INT + +I don't know if this is in a faq anywhere, but it should be. I myself have +helped a number of persons with this. Every once in a while there come +someone in to the #postgresql irc channel with the exact same problem. +Usually they leave the channel very happy, when their queries take less +then a second instead of minutes. + +-- +/Dennis + + +From pgsql-performance-owner@postgresql.org Sat Jan 18 14:55:18 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8B380475CE5 + for ; + Sat, 18 Jan 2003 11:26:21 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 7EF2D475E26 + for ; + Sat, 18 Jan 2003 11:24:21 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18Zvli-0006Hg-00 + for ; Sat, 18 Jan 2003 11:24:26 -0500 +Date: Sat, 18 Jan 2003 11:24:26 -0500 +From: Andrew Sullivan +To: "pgsql-performance@postgresql.org" +Subject: Re: 7.3.1 New install, large queries are slow +Message-ID: <20030118112426.A23790@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + "pgsql-performance@postgresql.org" +References: + <21623.1042865371@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <21623.1042865371@sss.pgh.pa.us>; + from tgl@sss.pgh.pa.us on Fri, Jan 17, 2003 at 11:49:31PM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/198 +X-Sequence-Number: 845 + +On Fri, Jan 17, 2003 at 11:49:31PM -0500, Tom Lane wrote: +> Jeff writes: +> > Informix, oracle, etc all do raw device access bypassing the kernels +> > buffering, etc. So they need heaping gobules of memory to do the same +> > thing the kernel does.. +> +> D'oh, I believe Jeff's put his finger on it. You need lotsa RAM if you +> are trying to bypass the OS. But Postgres would like to work with the +> OS, not bypass it. + +One of the interesting things I have been playing with on Solaris +recently is the various no-buffer settings you can give to the kernel +for filesystems. The idea is that you don't have the kernel do the +buffering, and you set your database's shared memory setting +_reeeeal_ high. + +As nearly as I can tell, there is again no benefit with PostgreSQL. +I'd also be amazed if this approach is a win for other systems. But +a lot of DBAs seem to believe that they know better than their +computers which tables are "really" accessed frequently. I think +they must be smarter than I am: I'd rather trust a system that was +designed to track these things and change the tuning on the fly, +myself. + +(To be fair, there are some cases where you have an +infrequently-accessed table which nevertheless is required to be fast +for some reason or other, so you might want to force it to stay in +memory.) + +A + +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Sat Jan 18 14:54:58 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0480B475ED1 + for ; + Sat, 18 Jan 2003 11:39:31 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 71918475AD7 + for ; + Sat, 18 Jan 2003 11:39:30 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18Zw0N-0006ZM-00 + for ; Sat, 18 Jan 2003 11:39:35 -0500 +Date: Sat, 18 Jan 2003 11:39:35 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: x86-64 and PostgreSQL +Message-ID: <20030118113935.C23790@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <1042867764.889.181.camel@haggis> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <1042867764.889.181.camel@haggis>; + from ron.l.johnson@cox.net on Fri, Jan 17, 2003 at 11:29:25PM + -0600 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/197 +X-Sequence-Number: 844 + +On Fri, Jan 17, 2003 at 11:29:25PM -0600, Ron Johnson wrote: +> Hi, +> +> Will there be any advantages to running Pg on a 64-bit CPU rather +> than 32-bit? + +In my experience, not really. We use SPARCs under Solaris 7 and, +now, 8. We haven't found any terribly obvious advantages with the +system compiled as a 64 bit app, but we _did_ find problems with the +64 bit libraries combined with gcc. As a result of that and +pressures to get working on some other things, we stopped testing +Postgres as a 64 bit app on Solaris. We haven't done any work on +Solaris 8 with it, and that system is a little more mature in the +64-bit-support department, so when I have a chance do to more +investigation, I will. + +> Also, would int8 then become a more "natural" default integer, rather +> than the int4 that all of us millions of i386, PPC & Sparc users use? + +I think the problem with int8s in a lot of cases has more to do with +typer coercion. So at least in systems < 7.4, I'm not sure you'll +see a big win, unless you make sure to cast everything correctly. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Mon Jan 20 01:29:43 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9049C475D22 + for ; + Mon, 20 Jan 2003 01:29:42 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 38D45475B8F + for ; + Mon, 20 Jan 2003 01:29:40 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id h0K6Tcs30556 + for ; Mon, 20 Jan 2003 11:59:38 +0530 +Received: from daithan (daithan.intranet.pspl.co.in [192.168.7.161]) + by www.pspl.co.in (8.11.6/8.11.0) with ESMTP id h0K6TcU30551 + for ; Mon, 20 Jan 2003 11:59:38 +0530 +From: "Shridhar Daithankar" +To: PgSQL Performance ML +Date: Mon, 20 Jan 2003 11:59:59 +0530 +MIME-Version: 1.0 +Subject: Re: x86-64 and PostgreSQL +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3E2BE4BF.28150.D33005A@localhost> +In-reply-to: <20030118113935.C23790@mail.libertyrms.com> +References: <1042867764.889.181.camel@haggis>; + from ron.l.johnson@cox.net on Fri, Jan 17, 2003 at 11:29:25PM -0600 +X-mailer: Pegasus Mail for Windows (v4.02) +Content-type: text/plain; charset=US-ASCII +Content-transfer-encoding: 7BIT +Content-description: Mail message body +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/199 +X-Sequence-Number: 846 + +On 18 Jan 2003 at 11:39, Andrew Sullivan wrote: +> On Fri, Jan 17, 2003 at 11:29:25PM -0600, Ron Johnson wrote: +> > Hi, +> > +> > Will there be any advantages to running Pg on a 64-bit CPU rather +> > than 32-bit? +> +> In my experience, not really. We use SPARCs under Solaris 7 and, +> now, 8. We haven't found any terribly obvious advantages with the +> system compiled as a 64 bit app, but we _did_ find problems with the +> 64 bit libraries combined with gcc. As a result of that and +> pressures to get working on some other things, we stopped testing +> Postgres as a 64 bit app on Solaris. We haven't done any work on +> Solaris 8 with it, and that system is a little more mature in the +> 64-bit-support department, so when I have a chance do to more +> investigation, I will. + +I remember reading in one of the HP guides regarding 64 bit that 64 bit is a +tool provided for applications. In general no app. should be 64 bit unless +required. In fact they advice that fastest performance one can get is by +running 32 bit app. on 64 bit machine because registers are wide and can be +filled in is less number of fetches. + +Sounds reasonable to me. + + + +Bye + Shridhar + +-- +Tip of the Day: Never fry bacon in the nude. [Correction: always fry bacon in +the nude; you'll learn not to burn it] + + +From pgsql-performance-owner@postgresql.org Mon Jan 20 01:34:29 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A339F475AE6 + for ; + Mon, 20 Jan 2003 01:34:27 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id CD0ED475AA1 + for ; + Mon, 20 Jan 2003 01:34:25 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id h0K6YOG31276 + for ; Mon, 20 Jan 2003 12:04:24 +0530 +Received: from daithan (daithan.intranet.pspl.co.in [192.168.7.161]) + by www.pspl.co.in (8.11.6/8.11.0) with ESMTP id h0K6YOU31271 + for ; Mon, 20 Jan 2003 12:04:24 +0530 +From: "Shridhar Daithankar" +To: pgsql-performance@postgresql.org +Date: Mon, 20 Jan 2003 12:04:45 +0530 +MIME-Version: 1.0 +Subject: Re: 7.3.1 New install, large queries are slow +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3E2BE5DD.30158.D375D9A@localhost> +References: +In-reply-to: <13109.1042824791@sss.pgh.pa.us> +X-mailer: Pegasus Mail for Windows (v4.02) +Content-type: text/plain; charset=US-ASCII +Content-transfer-encoding: 7BIT +Content-description: Mail message body +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/200 +X-Sequence-Number: 847 + +On 17 Jan 2003 at 12:33, Tom Lane wrote: + +> "Josh Berkus" writes: +> >>> shared_buffers = 131072 +> >> +> >> Yipes! Try about a tenth that much. Or less. +> +> > Why? He has 4GB RAM on the machine. +> +> I think a gig of shared buffers is overkill no matter what. +> +> One reason not to crank up shared_buffers "just because you can" is that +> there are operations (such as CHECKPOINT) that have to scan through all +> the buffers, linearly. I don't *think* any of these are in +> performance-critical paths, but nonetheless you're wasting CPU. I trust + +Assuming that one knows what he/she is doing, would it help in such cases i.e. +the linear search thing, to bump up page size to day 16K/32K? + +and that is also the only way to make postgresql use more than couple of gigs +of RAM, isn't it? + +Bye + Shridhar + +-- +Arithmetic: An obscure art no longer practiced in the world's developed +countries. + + +From pgsql-performance-owner@postgresql.org Mon Jan 20 02:14:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id DC8F9475AE6 + for ; + Mon, 20 Jan 2003 02:14:52 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 4AE12475AA1 + for ; + Mon, 20 Jan 2003 02:14:52 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0K7Ei5u027221; + Mon, 20 Jan 2003 02:14:44 -0500 (EST) +To: shridhar_daithankar@persistent.co.in +Cc: pgsql-performance@postgresql.org +Subject: Re: 7.3.1 New install, large queries are slow +In-reply-to: <3E2BE5DD.30158.D375D9A@localhost> +References: + <3E2BE5DD.30158.D375D9A@localhost> +Comments: In-reply-to "Shridhar Daithankar" + + message dated "Mon, 20 Jan 2003 12:04:45 +0530" +Date: Mon, 20 Jan 2003 02:14:43 -0500 +Message-ID: <27220.1043046883@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/201 +X-Sequence-Number: 848 + +"Shridhar Daithankar" writes: +> On 17 Jan 2003 at 12:33, Tom Lane wrote: +>> One reason not to crank up shared_buffers "just because you can" is that +>> there are operations (such as CHECKPOINT) that have to scan through all +>> the buffers, linearly. I don't *think* any of these are in +>> performance-critical paths, but nonetheless you're wasting CPU. I trust + +> Assuming that one knows what he/she is doing, would it help in such cases i.e. +> the linear search thing, to bump up page size to day 16K/32K? + +You mean increase page size and decrease the number of buffers +proportionately? It'd save on buffer-management overhead, but +I wouldn't assume there'd be an overall performance gain. The +system would have to do more I/O per page read or written; which +might be a wash for sequential scans, but I bet it would hurt for +random access. + +> and that is also the only way to make postgresql use more than couple of gigs +> of RAM, isn't it? + +It seems quite unrelated. The size of our shared memory segment is +limited by INT_MAX --- chopping it up differently won't change that. + +In any case, I think worrying because you can't push shared buffers +above two gigs is completely wrongheaded, for the reasons already +discussed in this thread. The notion that Postgres can't use more +than two gig because its shared memory is limited to that is +*definitely* wrongheaded. We can exploit however much memory your +kernel can manage for kernel disk cache. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Mon Jan 20 02:44:10 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id DB8B7475D22 + for ; + Mon, 20 Jan 2003 02:44:08 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 0CC2D475AE6 + for ; + Mon, 20 Jan 2003 02:44:07 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id h0K7i6v06628 + for ; Mon, 20 Jan 2003 13:14:06 +0530 +Received: from daithan (daithan.intranet.pspl.co.in [192.168.7.161]) + by www.pspl.co.in (8.11.6/8.11.0) with ESMTP id h0K7i6J06623 + for ; Mon, 20 Jan 2003 13:14:06 +0530 +From: "Shridhar Daithankar" +To: pgsql-performance@postgresql.org +Date: Mon, 20 Jan 2003 13:14:27 +0530 +MIME-Version: 1.0 +Subject: Re: 7.3.1 New install, large queries are slow +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3E2BF633.14532.D772D99@localhost> +References: <3E2BE5DD.30158.D375D9A@localhost> +In-reply-to: <27220.1043046883@sss.pgh.pa.us> +X-mailer: Pegasus Mail for Windows (v4.02) +Content-type: text/plain; charset=US-ASCII +Content-transfer-encoding: 7BIT +Content-description: Mail message body +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/202 +X-Sequence-Number: 849 + +On 20 Jan 2003 at 2:14, Tom Lane wrote: + +> "Shridhar Daithankar" writes: +> > Assuming that one knows what he/she is doing, would it help in such cases i.e. +> > the linear search thing, to bump up page size to day 16K/32K? +> +> You mean increase page size and decrease the number of buffers +> proportionately? It'd save on buffer-management overhead, but +> I wouldn't assume there'd be an overall performance gain. The +> system would have to do more I/O per page read or written; which +> might be a wash for sequential scans, but I bet it would hurt for +> random access. + +Right. But it has its own applications. If I am saving huge data blocks like +say gene stuff, I might be better off living with a relatively bigger page +fragmentation. + +> > and that is also the only way to make postgresql use more than couple of gigs +> > of RAM, isn't it? +> +> It seems quite unrelated. The size of our shared memory segment is +> limited by INT_MAX --- chopping it up differently won't change that. + +Well, if my page size is doubled, I can get double amount of shared buffers. +That was the logic nothing else. + +> In any case, I think worrying because you can't push shared buffers +> above two gigs is completely wrongheaded, for the reasons already +> discussed in this thread. The notion that Postgres can't use more +> than two gig because its shared memory is limited to that is +> *definitely* wrongheaded. We can exploit however much memory your +> kernel can manage for kernel disk cache. + +Well, I agree completely. However there are folks and situation which demands +things because they can be done. This is just to check out the absolute limit +what it can manage. + + +Bye + Shridhar + +-- +Bagdikian's Observation: Trying to be a first-rate reporter on the average +American newspaper is like trying to play Bach's "St. Matthew Passion" on a +ukelele. + + +From pgsql-performance-owner@postgresql.org Mon Jan 20 04:41:32 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3C77D476538 + for ; + Mon, 20 Jan 2003 04:41:31 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 6A1B947646C + for ; + Mon, 20 Jan 2003 04:41:24 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030120094126.LQFD8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Mon, 20 Jan 2003 04:41:26 -0500 +Subject: Very large caches (was Re: 7.3.1 New install, large queries are slow) +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <27220.1043046883@sss.pgh.pa.us> +References: + <3E2BE5DD.30158.D375D9A@localhost> <27220.1043046883@sss.pgh.pa.us> +Content-Type: text/plain +Organization: +Message-Id: <1043055681.15592.156.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 20 Jan 2003 03:41:21 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/203 +X-Sequence-Number: 850 + +On Mon, 2003-01-20 at 01:14, Tom Lane wrote: +> "Shridhar Daithankar" writes: +> > On 17 Jan 2003 at 12:33, Tom Lane wrote: +[snip] +> > and that is also the only way to make postgresql use more than couple of gigs +> > of RAM, isn't it? +> +> It seems quite unrelated. The size of our shared memory segment is +> limited by INT_MAX --- chopping it up differently won't change that. +> +> In any case, I think worrying because you can't push shared buffers +> above two gigs is completely wrongheaded, for the reasons already +> discussed in this thread. The notion that Postgres can't use more +> than two gig because its shared memory is limited to that is +> *definitely* wrongheaded. We can exploit however much memory your +> kernel can manage for kernel disk cache. + +http://www.redhat.com/services/techsupport/production/GSS_caveat.html +"RAM Limitations on IA32 +Red Hat Linux releases based on the 2.4 kernel -- including Red Hat +Linux 7.1, 7.2, 7.3 and Red Hat Linux Advanced Server 2.1 -- support +a maximum of 16GB of RAM." + +So if I have some honking "big" Compaq Xeon SMP server w/ 16GB RAM, +and top(1) shows that there is 8GB of buffers, then Pg will be happy +as a pig in the mud? + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Jan 20 04:52:19 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6B582475E14 + for ; + Mon, 20 Jan 2003 04:52:18 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 83970475D22 + for ; + Mon, 20 Jan 2003 04:52:17 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030120095219.LTFL8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Mon, 20 Jan 2003 04:52:19 -0500 +Subject: Re: x86-64 and PostgreSQL +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <3E2BE4BF.28150.D33005A@localhost> +References: <1042867764.889.181.camel@haggis> ; + from ron.l.johnson@cox.net on Fri, Jan 17, 2003 at 11:29:25PM -0600 + <3E2BE4BF.28150.D33005A@localhost> +Content-Type: text/plain +Organization: +Message-Id: <1043056334.15592.167.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 20 Jan 2003 03:52:15 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/204 +X-Sequence-Number: 851 + +On Mon, 2003-01-20 at 00:29, Shridhar Daithankar wrote: +> On 18 Jan 2003 at 11:39, Andrew Sullivan wrote: +> > On Fri, Jan 17, 2003 at 11:29:25PM -0600, Ron Johnson wrote: +> > > Hi, +> > > +> > > Will there be any advantages to running Pg on a 64-bit CPU rather +> > > than 32-bit? +> > +> > In my experience, not really. We use SPARCs under Solaris 7 and, +> > now, 8. We haven't found any terribly obvious advantages with the +> > system compiled as a 64 bit app, but we _did_ find problems with the +> > 64 bit libraries combined with gcc. As a result of that and +> > pressures to get working on some other things, we stopped testing +> > Postgres as a 64 bit app on Solaris. We haven't done any work on +> > Solaris 8 with it, and that system is a little more mature in the +> > 64-bit-support department, so when I have a chance do to more +> > investigation, I will. +> +> I remember reading in one of the HP guides regarding 64 bit that 64 bit is a +> tool provided for applications. In general no app. should be 64 bit unless +> required. In fact they advice that fastest performance one can get is by +> running 32 bit app. on 64 bit machine because registers are wide and can be +> filled in is less number of fetches. +> +> Sounds reasonable to me. + +Dou you, the programmer or SysAdmin, always know when 64 bits is +needed? + +Take, for simple example, a memcpy() of 1024 bytes. Most CPUs don't +have direct core-core copy instruction. (The RISC philosophy, after +all, is load-and-store.) A 32-bit executable would need 1024/32 = 32 +pairs of load-store operations, while a 64-bit executable would only +need 16. Yes, L1 & L2 caching would help some, but not if you are +moving huge amounts of data... + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Jan 20 04:59:23 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2878B475D22 + for ; + Mon, 20 Jan 2003 04:59:22 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 4B878475CED + for ; + Mon, 20 Jan 2003 04:59:20 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id h0K9xLJ27009 + for ; Mon, 20 Jan 2003 15:29:21 +0530 +Received: from daithan (daithan.intranet.pspl.co.in [192.168.7.161]) + by www.pspl.co.in (8.11.6/8.11.0) with ESMTP id h0K9xKn27004 + for ; Mon, 20 Jan 2003 15:29:20 +0530 +From: "Shridhar Daithankar" +To: PgSQL Performance ML +Date: Mon, 20 Jan 2003 15:29:42 +0530 +MIME-Version: 1.0 +Subject: Re: x86-64 and PostgreSQL +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3E2C15E6.9191.DF2FEFC@localhost> +References: <3E2BE4BF.28150.D33005A@localhost> +In-reply-to: <1043056334.15592.167.camel@haggis> +X-mailer: Pegasus Mail for Windows (v4.02) +Content-type: text/plain; charset=US-ASCII +Content-transfer-encoding: 7BIT +Content-description: Mail message body +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/205 +X-Sequence-Number: 852 + +On 20 Jan 2003 at 3:52, Ron Johnson wrote: + +> On Mon, 2003-01-20 at 00:29, Shridhar Daithankar wrote: +> > I remember reading in one of the HP guides regarding 64 bit that 64 bit is a +> > tool provided for applications. In general no app. should be 64 bit unless +> > required. In fact they advice that fastest performance one can get is by +> > running 32 bit app. on 64 bit machine because registers are wide and can be +> > filled in is less number of fetches. +> > +> > Sounds reasonable to me. +> +> Dou you, the programmer or SysAdmin, always know when 64 bits is +> needed? +> +> Take, for simple example, a memcpy() of 1024 bytes. Most CPUs don't +> have direct core-core copy instruction. (The RISC philosophy, after +> all, is load-and-store.) A 32-bit executable would need 1024/32 = 32 +> pairs of load-store operations, while a 64-bit executable would only +> need 16. Yes, L1 & L2 caching would help some, but not if you are +> moving huge amounts of data... + +Well, that wasn't intended application aera of that remark. I was more on the +line of, I have 16GB data of double precision which I need to shuffle thr. once +in a while, should I use 32 bit or 64 bit? + +Something like that.. bit more macroscopic. + +I work on an application which is 32 bit on HP-UX 64 bit. It handles more than +15GB of data at some sites pretty gracefully..No need to move to 64 bit as +yet.. + +Bye + Shridhar + +-- +Kramer's Law: You can never tell which way the train went by looking at the +tracks. + + +From pgsql-performance-owner@postgresql.org Mon Jan 20 07:06:13 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7F6BF475CED + for ; + Mon, 20 Jan 2003 07:06:11 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id BDBDA475CE7 + for ; + Mon, 20 Jan 2003 07:06:10 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030120120613.NETK8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Mon, 20 Jan 2003 07:06:13 -0500 +Subject: Re: x86-64 and PostgreSQL +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <3E2C15E6.9191.DF2FEFC@localhost> +References: <3E2BE4BF.28150.D33005A@localhost> + <3E2C15E6.9191.DF2FEFC@localhost> +Content-Type: text/plain +Organization: +Message-Id: <1043064363.15592.187.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 20 Jan 2003 06:06:04 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/206 +X-Sequence-Number: 853 + +On Mon, 2003-01-20 at 03:59, Shridhar Daithankar wrote: +> On 20 Jan 2003 at 3:52, Ron Johnson wrote: +> +> > On Mon, 2003-01-20 at 00:29, Shridhar Daithankar wrote: +> > > I remember reading in one of the HP guides regarding 64 bit that 64 bit is a +> > > tool provided for applications. In general no app. should be 64 bit unless +> > > required. In fact they advice that fastest performance one can get is by +> > > running 32 bit app. on 64 bit machine because registers are wide and can be +> > > filled in is less number of fetches. +> > > +> > > Sounds reasonable to me. +> > +> > Dou you, the programmer or SysAdmin, always know when 64 bits is +> > needed? +> > +> > Take, for simple example, a memcpy() of 1024 bytes. Most CPUs don't +> > have direct core-core copy instruction. (The RISC philosophy, after +> > all, is load-and-store.) A 32-bit executable would need 1024/32 = 32 +> > pairs of load-store operations, while a 64-bit executable would only +> > need 16. Yes, L1 & L2 caching would help some, but not if you are +> > moving huge amounts of data... +> +> Well, that wasn't intended application aera of that remark. I was more on the +> line of, I have 16GB data of double precision which I need to shuffle thr. once +> in a while, should I use 32 bit or 64 bit? +> +> Something like that.. bit more macroscopic. +> +> I work on an application which is 32 bit on HP-UX 64 bit. It handles more than +> 15GB of data at some sites pretty gracefully..No need to move to 64 bit as +> yet.. + +Maybe you wouldn't get a speed boost on HP-UX, but I bet you would on +x86-64. Why? 64 bit programs get to use the new registers that AMD +created just for 64 bit mode. Thus, the compiler should, hopefully, +be able to generate more efficient code. + +Also, since (at least on the gcc-3.2 compiler) a "long" and "int" are +still 32 bits (64 bit scalars are of type "long long"), existing +programs (that all use "long" and "int") will still only fill up 1/2 +of each register (attaining the speed that HP alleges), but, as I +mentioned above, would be able to use the extra registers if recompiled +into native 64-bit apps... + +$ cat test.c +#include +#include +int main (int argc, char **argv) +{ + printf("%d %d %d\n", sizeof(long), + sizeof(int), + sizeof(long long)); +}; +$ gcc-3.2 test.c && ./a.out +4 4 8 + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Basically, I got on the plane with a bomb. Basically, I | +| tried to ignite it. Basically, yeah, I intended to damage | +| the plane." | +| RICHARD REID, who tried to blow up American Airlines | +| Flight 63 | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Jan 20 07:11:39 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D5653475CED + for ; + Mon, 20 Jan 2003 07:11:38 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 23E74475CE7 + for ; + Mon, 20 Jan 2003 07:11:36 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id h0KCBbs13104 + for ; Mon, 20 Jan 2003 17:41:37 +0530 +Received: from daithan (daithan.intranet.pspl.co.in [192.168.7.161]) + by www.pspl.co.in (8.11.6/8.11.0) with ESMTP id h0KCBbw13099 + for ; Mon, 20 Jan 2003 17:41:37 +0530 +From: "Shridhar Daithankar" +To: PgSQL Performance ML +Date: Mon, 20 Jan 2003 17:41:59 +0530 +MIME-Version: 1.0 +Subject: Re: x86-64 and PostgreSQL +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3E2C34E7.25952.E6C1A58@localhost> +References: <3E2C15E6.9191.DF2FEFC@localhost> +In-reply-to: <1043064363.15592.187.camel@haggis> +X-mailer: Pegasus Mail for Windows (v4.02) +Content-type: text/plain; charset=US-ASCII +Content-transfer-encoding: 7BIT +Content-description: Mail message body +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/207 +X-Sequence-Number: 854 + +On 20 Jan 2003 at 6:06, Ron Johnson wrote: + +> On Mon, 2003-01-20 at 03:59, Shridhar Daithankar wrote: +> > On 20 Jan 2003 at 3:52, Ron Johnson wrote: +> > I work on an application which is 32 bit on HP-UX 64 bit. It handles more than +> > 15GB of data at some sites pretty gracefully..No need to move to 64 bit as +> > yet.. +> +> Maybe you wouldn't get a speed boost on HP-UX, but I bet you would on +> x86-64. Why? 64 bit programs get to use the new registers that AMD +> created just for 64 bit mode. Thus, the compiler should, hopefully, +> be able to generate more efficient code. + +Well, that is not the issue exactly. The app. is commercial with oracle under +it and it si going nowhere but oracle/HP-UX for its remaining lifecycle.. I was +just quoting it as an example. + +> Also, since (at least on the gcc-3.2 compiler) a "long" and "int" are +> still 32 bits (64 bit scalars are of type "long long"), existing +> programs (that all use "long" and "int") will still only fill up 1/2 +> of each register (attaining the speed that HP alleges), but, as I +> mentioned above, would be able to use the extra registers if recompiled +> into native 64-bit apps... + +I am not too sure, but most 64bit migration guides talk of ILP paradigm that is +integer/long/pointer with later two going to 8 bits. If gcc puts long at 4 +bytes on a 64 bit platform, it is wrong. + +Bye + Shridhar + +-- +Painting, n.: The art of protecting flat surfaces from the weather, and +exposing them to the critic. -- Ambrose Bierce + + +From pgsql-performance-owner@postgresql.org Mon Jan 20 10:16:47 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 63276476075 + for ; + Mon, 20 Jan 2003 10:16:45 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 710E1476021 + for ; + Mon, 20 Jan 2003 10:16:44 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0KFGl5u002996; + Mon, 20 Jan 2003 10:16:47 -0500 (EST) +To: Ron Johnson +Cc: PgSQL Performance ML +Subject: Re: Very large caches (was Re: 7.3.1 New install, + large queries are slow) +In-reply-to: <1043055681.15592.156.camel@haggis> +References: + <3E2BE5DD.30158.D375D9A@localhost> <27220.1043046883@sss.pgh.pa.us> + <1043055681.15592.156.camel@haggis> +Comments: In-reply-to Ron Johnson + message dated "20 Jan 2003 03:41:21 -0600" +Date: Mon, 20 Jan 2003 10:16:47 -0500 +Message-ID: <2995.1043075807@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/208 +X-Sequence-Number: 855 + +Ron Johnson writes: +> So if I have some honking "big" Compaq Xeon SMP server w/ 16GB RAM, +> and top(1) shows that there is 8GB of buffers, then Pg will be happy +> as a pig in the mud? + +Sounds good to me ... + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Mon Jan 20 16:40:49 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E29F7476B7A + for ; + Mon, 20 Jan 2003 16:40:44 -0500 (EST) +Received: from pos_pdc.posportal.com (unknown [12.158.169.100]) + by postgresql.org (Postfix) with ESMTP id DDEAE476CDE + for ; + Mon, 20 Jan 2003 16:32:41 -0500 (EST) +X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3 +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="utf-8" +Content-Transfer-Encoding: base64 +Subject: Re: 7.3.1 New install, large queries are slow +Date: Mon, 20 Jan 2003 13:32:42 -0800 +Message-ID: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C0F@pos_pdc.posportal.com> +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [PERFORM] 7.3.1 New install, large queries are slow +Thread-Index: AcK+xLE/Sv/ROSiNRa6IWzg15iBHMgB61ut7 +From: "Roman Fail" +To: =?utf-8?Q?Dennis_Bj=C3=B6rklund?= +Cc: "Josh Berkus" , + "Stephan Szabo" , + , "Tom Lane" +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/209 +X-Sequence-Number: 856 + +Pj4gSXQgc29ydCBvZiBmZWVscyBsaWtlIGEgbWFnaWMgbW9tZW50LiAgSSB3 +ZW50IGJhY2sgYW5kIGxvb2tlZCB0aHJvdWdoIGENCj4+IGxvdCBvZiB0aGUg +Sk9JTiBjb2x1bW5zIGFuZCBmb3VuZCB0aGF0IEkgd2FzIG1peGluZyBpbnQ0 +IHdpdGggaW50OCBpbiBhDQo+PiBsb3Qgb2YgdGhlbS4NCg0KPlRoZXJlIGlz +IG5vdGUgYWJvdXQgaXQgaW4gdGhlIGRvY3M6DQo+aHR0cDovL3d3dy5wb3N0 +Z3Jlc3FsLm9yZy9pZG9jcy9pbmRleC5waHA/ZGF0YXR5cGUuaHRtbCNEQVRB +VFlQRS1JTlQNCj4NCj5JIGRvbid0IGtub3cgaWYgdGhpcyBpcyBpbiBhIGZh +cSBhbnl3aGVyZSwgYnV0IGl0IHNob3VsZCBiZS4gSSBteXNlbGYgaGF2ZQ0K +PmhlbHBlZCBhIG51bWJlciBvZiBwZXJzb25zIHdpdGggdGhpcy4gRXZlcnkg +b25jZSBpbiBhIHdoaWxlIHRoZXJlIGNvbWUNCj5zb21lb25lIGluIHRvIHRo +ZSAjcG9zdGdyZXNxbCBpcmMgY2hhbm5lbCB3aXRoIHRoZSBleGFjdCBzYW1l +IHByb2JsZW0uIA0KPlVzdWFsbHkgdGhleSBsZWF2ZSB0aGUgY2hhbm5lbCB2 +ZXJ5IGhhcHB5LCB3aGVuIHRoZWlyIHF1ZXJpZXMgdGFrZSBsZXNzDQo+dGhl +biBhIHNlY29uZCBpbnN0ZWFkIG9mIG1pbnV0ZXMuDQo+DQo+LS0NCj4vRGVu +bmlzDQoNCkknbSByZWFsbHkgc3VycHJpc2VkIHRoYXQgdGhpcyBpc3N1ZSBk +b2Vzbid0IHBvcCB1cCBhbGwgdGhlIHRpbWUuICBBcyB0aGUgY29tbXVuaXR5 +IGdyb3dzLCBJIHRoaW5rIGl0IHdpbGwgc3RhcnQgdG8uICBJIGNhbWUgdmVy +eSwgdmVyeSBjbG9zZSB0byBkcm9wcGluZyBQb3N0Z3JlU1FMIGVudGlyZWx5 +IGJlY2F1c2Ugb2YgaXQuICBIb3BlZnVsbHkgdGhlIFRPRE8gaXNzdWUgb24g +aW1wbGljaXQgdHlwZSBjYXN0aW5nIHdpbGwgbW92ZSBjbG9zZXIgdG8gdGhl +IHRvcCBvZiB0aGUgaGFja2VycyBsaXN0LiAgQnV0IEknbSBqdXN0IGEgYmVn +Z2FyIHNvIEkgd29uJ3QgcHJldGVuZCB0byBiZSBhIGNob29zZXIuDQogDQpC +YWNrIHRvIG15IG9yaWdpbmFsIHByb2JsZW1zOiAgSSByZS1jcmVhdGVkIGV2 +ZXJ5dGhpbmcgZnJvbSBzY3JhdGNoIGFuZCBtYWRlIHN1cmUgdGhlcmUgYXJl +IG5vIGludDgncyBpbiBteSBlbnRpcmUgZGF0YWJhc2UuICAgSSBmb3VuZCBh +IGZldyBtb3JlIHBsYWNlcyB0aGF0IEkgY291bGQgY3JlYXRlIHVzZWZ1bCBp +bmRleGVzIGFzIHdlbGwuICBJIGRpZG4ndCBnZXQgdG8gdGVzdCBpdCBvdmVy +IHRoZSB3ZWVrZW5kLCBidXQgdG9kYXkgSSBwbGF5ZWQgd2l0aCBpdCBmb3Ig +c2V2ZXJhbCBob3VycyBhbmQgY291bGQgbm90IGdldCB0aGUgcXVlcmllcyB0 +byBwZXJmb3JtIG11Y2ggYmV0dGVyIHRoYW4gbGFzdCB3ZWVrLiAgSSB3YXMg +YWJvdXQgcmVhZHkgdG8gZ2l2ZSB1cCwgdGhyb3cgUG9zdGdyZXMgaW4gdGhl +IGp1bmsgcGlsZSwgYW5kIGdldCBvdXQgdGhlIE1TU1FMIENELiAgDQogDQpM +dWNraWx5LCBhbiB1bnJlbGF0ZWQgcG9zdCBvbiBvbmUgb2YgdGhlIGxpc3Rz +IG1lbnRpb25lZCBzb21ldGhpbmcgYWJvdXQgQU5BTFlaRSwgYW5kIEkgcmVh +bGl6ZWQgdGhhdCBJIGhhZCBmb3Jnb3R0ZW4gdG8gcnVuIGl0IGFmdGVyIGFs +bCB0aGUgbmV3IGRhdGEgd2FzIGltcG9ydGVkIChhbHRob3VnaCBJIGRpZCBy +ZW1lbWJlciBhIFZBQ1VVTSBGVUxMKS4gIEFmdGVyIHJ1bm5pbmcgQU5BTFla +RSwgSSBzdGFydGVkIGdldHRpbmcgYW1hemluZyByZXN1bHRzLi4uLi5saWtl +IGEgcXVlcnkgdGhhdCB0b29rIDIwIG1pbnV0ZXMgbGFzdCB3ZWVrIHdhcyB0 +YWtpbmcgb25seSA2IG1pbGxpc2Vjb25kcyBub3cuICBUaGF0IGtpY2tzIHRo +ZSBNU1NRTCBzZXJ2ZXIncyBhc3MgYWxsIG92ZXIgdGhlIG1hcCAoYXMgSSBo +YWQgb3JpZ2luYWxseSBleHBlY3RlZCBpdCB3b3VsZCEhISkuDQogDQpTbyB0 +aGluZ3MgYXJlIHdvcmtpbmcgcHJldHR5IGdvb2Qgbm93Li4uLmFuZCBpdCBs +b29rcyBsaWtlIHRoZSB3aG9sZSBwcm9ibGVtIHdhcyB0aGUgZGF0YSB0eXBl +IG1pc21hdGNoIGlzc3VlLiAgSSBoYXRlIHRvIHBvaW50IGZpbmdlcnMsIGJ1 +dCB0aGUgcGdBZG1pbklJIE1pZ3JhdGlvbiBXaXphcmQgZm9yY2VzIGFsbCB5 +b3VyIHByaW1hcnkga2V5cyB0byBiZSBpbnQ4IGV2ZW4gaWYgeW91IHNldCB0 +aGUgVHlwZSBNYXAgdG8gaW50NC4gIFRoZSBzZWNvbmQgdGltZSB0aHJvdWdo +IEkgcmVjb2duaXplZCB0aGlzIGFuZCBkaWQgYSBwZ19kdW1wIHNvIEkgY291 +bGQgc3dpdGNoIGV2ZXJ5dGhpbmcgdG8gaW50NC4gIE5vdyBJJ20gZ29pbmcg +dG8gd3JpdGUgc29tZSBtaW5vciBtb2RzIGluIG15IEphdmEgcHJvZ3JhbXMg +Zm9yIFBHU1FMLXN5bnRheCBjb21wYXRpYmlsaXR5LCBhbmQgd2lsbCBob3Bl +ZnVsbHkgaGF2ZSB0aGUgUG9zdGdyZVNRTCBzZXJ2ZXIgaW4gcHJvZHVjdGlv +biBzaG9ydGx5LiAgDQogDQpUSEFOSyBZT1UgdG8gZXZlcnlvbmUgb24gcGdz +cWwtcGVyZm9ybWFuY2UgZm9yIGFsbCB5b3VyIGhlbHAuICBZb3UgYXJlIHRo +ZSByZWFzb24gdGhhdCBJJ2xsIGJlIGEgbG9uZyB0ZXJtIG1lbWJlciBvZiB0 +aGUgUG9zdGdyZXMgY29tbXVuaXR5LiAgSSBob3BlIHRoYXQgSSBjYW4gYXNz +aXN0IHNvbWVvbmUgZWxzZSBvdXQgaW4gdGhlIGZ1dHVyZS4gIA0KIA0KUm9t +YW4gRmFpbA0KU3IuIFdlYiBBcHBsaWNhdGlvbiBEZXZlbG9wZXINClBPUyBQ +b3J0YWwsIEluYy4NCiANCiANCg== + +From pgsql-performance-owner@postgresql.org Mon Jan 20 17:15:20 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2AC854764B8 + for ; + Mon, 20 Jan 2003 17:15:19 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id B0F324765CB + for ; + Mon, 20 Jan 2003 17:14:41 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2320112; Mon, 20 Jan 2003 14:14:46 -0800 +From: "Josh Berkus" +Subject: Re: 7.3.1 New install, large queries are slow +To: "Roman Fail" +Cc: +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Mon, 20 Jan 2003 14:14:46 -0800 +Message-ID: +In-Reply-To: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C0F@pos_pdc.posportal.com> +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/210 +X-Sequence-Number: 857 + +Roman, + +> I'm really surprised that this issue doesn't pop up all the time. As +> the community grows, I think it will start to. + +Actually, in the general sense of intelligent casting, the issue *does* +come up all the time. Unfortunately, this is one of those issues that +requires both an inspired solution and program-wide overhaul work to +fix. In fact, in the FTP achives you can find an alternate version of +Postgres (7.1 I think) where someone tried to fix the "stupid casting" +issue and succeeded in making Postgres crash and burn instead. + +> Luckily, an unrelated post on one of the lists mentioned something +> about ANALYZE, and I realized that I had forgotten to run it after +> all the new data was imported (although I did remember a VACUUM +> FULL). After running ANALYZE, I started getting amazing +> results.....like a query that took 20 minutes last week was taking +> only 6 milliseconds now. That kicks the MSSQL server's ass all over +> the map (as I had originally expected it would!!!). + +That's great! + +> So things are working pretty good now....and it looks like the whole +> problem was the data type mismatch issue. I hate to point fingers, +> but the pgAdminII Migration Wizard forces all your primary keys to be +> int8 even if you set the Type Map to int4. + +So? Send Dave Page (address at pgadmin.postgresql.org) a quick note +documenting the problem. I'm sure he'll patch it, or at least fix it +for PGAdmin III. + +> THANK YOU to everyone on pgsql-performance for all your help. You +> are the reason that I'll be a long term member of the Postgres +> community. I hope that I can assist someone else out in the future. + +You're welcome! If you can get your boss to authorize it, the +Advocacy page (advocacy.postgresql.org) could use some more business +testimonials. + +-Josh Berkus + + +From pgsql-performance-owner@postgresql.org Mon Jan 20 17:33:50 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 373FE4764EB + for ; + Mon, 20 Jan 2003 17:33:49 -0500 (EST) +Received: from pos_pdc.posportal.com (unknown [12.158.169.100]) + by postgresql.org (Postfix) with ESMTP id BA6E54768AC + for ; + Mon, 20 Jan 2003 17:33:23 -0500 (EST) +X-MimeOLE: Produced By Microsoft Exchange V6.0.5762.3 +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="utf-8" +Content-Transfer-Encoding: base64 +Subject: Re: 7.3.1 New install, large queries are slow +Date: Mon, 20 Jan 2003 14:33:25 -0800 +Message-ID: <9B1C77393DED0D4B9DAA1AA1742942DA0E4C11@pos_pdc.posportal.com> +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [PERFORM] 7.3.1 New install, large queries are slow +Thread-Index: AcLAzrojSfxhtVV6SFKZ2/vr+e/ZegAAziiJ +From: "Roman Fail" +To: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/211 +X-Sequence-Number: 858 + +PiBKb2NoZW0gdmFuIERpZXRlbiB3cm90ZToNCj4gSnVzdCBvdXQgb2YgY3Vy +aW9zaXR5IGFuZCBmb3IgYXJjaGl2aW5nIHB1cnBvc2VzLCBjb3VsZCB5b3Ug +cG9zdCB0aGUgbmV3DQo+IEVYUExBSU4gQU5BTFlaRSBvdXRwdXQgdG8gdGhl +IGxpc3Q/DQoNClRvIHJlaXRlcmF0ZSwgdGhlIGJhdGNoZGV0YWlsIHRhYmxl +IGlzIDI0IG1pbGxpb24gcm93cywgYmF0Y2hoZWFkZXIgaXMgMi43IG1pbGxp +b24sIGFuZCBwdXJjMSBpcyAxIG1pbGxpb24uICBUaGUgcmVzdCBhcmUgMjAw +MCByb3dzIG9yIGxlc3MuICBJIHRoaW5rIGhhdmluZyB0aGUgNi1kaXNrIFJB +SUQtMTAgZGV2b3RlZCB0byAvdXNyL2xvY2FsL3Bnc3FsL2RhdGEgaGVscHMg +b3V0IGEgbGl0dGxlIGhlcmUuICAgSSBkaWQgdHJ5IGNoYW5naW5nIHRoZSBX +SEVSRSBjbGF1c2VzIHRvIHJhZGljYWxseSBkaWZmZXJlbnQgdmFsdWVzIGFu +ZCBpdCB3YXMgc3RpbGwganVzdCBhcyBmYXN0LiAgVGhpcyBpcyB0aGUgb3Jp +Z2luYWwgcXVlcnkgSSB3YXMgd29ya2luZyB3aXRoIChwbHVzIHN1Z2dlc3Rl 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+X-Authentication-Warning: water.oasis.net.au: Host guardian [210.8.139.5] + claimed to be oasis.net.au +Message-ID: <3E2C88DD.6090808@oasis.net.au> +Date: Tue, 21 Jan 2003 09:40:13 +1000 +From: Rudi Starcevic +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; + rv:1.1) Gecko/20020826 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: pgsql-performance@postgresql.org +Subject: subscribe +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/212 +X-Sequence-Number: 859 + +subscribe + + +From pgsql-performance-owner@postgresql.org Tue Jan 21 03:21:14 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 45A04475DB3 + for ; + Tue, 21 Jan 2003 03:21:12 -0500 (EST) +Received: from ore.jhcloos.com (ore.jhcloos.com [64.240.156.239]) + by postgresql.org (Postfix) with ESMTP id 9B2A3475BEC + for ; + Tue, 21 Jan 2003 03:21:11 -0500 (EST) +Received: from lugabout.jhcloos.org (ppp505.tc-1.buf-ch.ny.localnet.com + [207.251.222.251]) + (using TLSv1 with cipher EDH-RSA-DES-CBC3-SHA (168/168 bits)) + (Client CN "lugabout.jhcloos.org", + Issuer "ca.jhcloos.com" (verified OK)) + by ore.jhcloos.com (Postfix) with ESMTP + id 3C8301C36B; Tue, 21 Jan 2003 02:21:11 -0600 (CST) +Received: from lugabout.jhcloos.org (localhost [127.0.0.1]) + by lugabout.jhcloos.org (Postfix on SuSE Linux 7.3 (i386)) with ESMTP + id B8FBA3F16; Tue, 21 Jan 2003 08:21:03 +0000 (GMT) +To: Ron Johnson +Cc: PgSQL Performance ML +Subject: Re: x86-64 and PostgreSQL +References: <3E2BE4BF.28150.D33005A@localhost> + <3E2C15E6.9191.DF2FEFC@localhost> <1043064363.15592.187.camel@haggis> +From: "James H. Cloos Jr." +In-Reply-To: <1043064363.15592.187.camel@haggis> +Date: 21 Jan 2003 03:21:03 -0500 +Message-ID: +Lines: 14 +User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.1 +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/213 +X-Sequence-Number: 860 + +>>>>> "Ron" == Ron Johnson writes: + +Ron> Also, since (at least on the gcc-3.2 compiler) a "long" and "int" +Ron> are still 32 bits (64 bit scalars are of type "long long"), + +According to the draft x86-64 psABI�, which is to become the +System V psABI for the x86-64 architecture, sizeof(long) == 8. + +This does seem necessary as most code tends to presume that an +unsigned long can hold a pointer.... + +-JimC + +� http://www.x86-64.org/abi.pdf + + +From pgsql-performance-owner@postgresql.org Tue Jan 21 16:21:02 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6FEA5475CE7 + for ; + Tue, 21 Jan 2003 16:21:00 -0500 (EST) +Received: from martin.sysdetect.com (martin.sysdetect.com [65.209.102.1]) + by postgresql.org (Postfix) with ESMTP id F09DF475425 + for ; + Tue, 21 Jan 2003 16:20:53 -0500 (EST) +Received: (from mail@localhost) + by martin.sysdetect.com (8.11.3/8.11.3) id h0LLKtH20808 + for ; Tue, 21 Jan 2003 21:20:55 GMT +Received: from winwood.sysdetect.com(172.16.1.1) + via SMTP by mail.sysdetect.com, id smtpdm26056; Tue Jan 21 21:20:49 2003 +Received: from winwood.sysdetect.com (seth@localhost) + by winwood.sysdetect.com (8.11.6/8.11.6) with ESMTP id h0LLKn820463 + for ; Tue, 21 Jan 2003 16:20:49 -0500 +Message-Id: <200301212120.h0LLKn820463@winwood.sysdetect.com> +To: pgsql-performance@postgresql.org +From: "Seth Robertson" +Subject: Postgres 7.3.1 poor insert/update/search performance esp WRT Oracle +MIME-Version: 1.0 +Content-Type: multipart/mixed; boundary="----- =_aaaaaaaaaa0" +Content-ID: <20460.1043184020.0@winwood.sysdetect.com> +Date: Tue, 21 Jan 2003 16:20:49 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/214 +X-Sequence-Number: 861 + +------- =_aaaaaaaaaa0 +Content-Type: text/plain; charset="us-ascii" +Content-ID: <20460.1043184020.1@winwood.sysdetect.com> +Content-Description: text + +I'm trying to get converted over to Postgres from Oracle (Postgres is +billions of times more straightforward and pragmatically clean than +Oracle), but I'm having some severe performance problems on what +naively appears to be a very straightforward dead-simple test. + +The test is comprised of two parts: a write part which attempts to +accumulate (sum) numbers by distinct keys, and a read part which +searches for keys in the database (some of which will be present, some +of which will not). In a more realistic scenario, both will be +happening all of the time, but we can start off easy. + +However, performance is terrible: around 39 write transactions/second +and 69 searches/second. Oracle, by comparison, writes at 314 and +reads at 395--practically an order of magnitude better performance. +Both are using the same hardware (obviously not at the same time) +which is a dual-processor AMD 2000+ with 3GB memory and both oracle +and postgres loaded on a 105GB ``MD'' striped (no redundancy) 2 SCSI +disks running ext3 fs (no special flags) with Linux 2.4.18-10smp. + +I actually have seven different schemes for performing the writes +using Postgres: + +---------------------------------------------------------------------- +"normal" C libpq 39 t/s +"normal" Perl DBI 39 t/s +"DBI Prepared Statement" Perl DBI 39 t/s +"Batching" Perl DBI 45 t/s +"arrays" Perl DBI 26 t/s +"server-side function" Perl DBI 39 t/s +"server-side trigger" Perl DBI 39 t/s +"normal" Perl DBI read 69 t/s +"normal" Perl DBI for Oracle 314 t/s +"normal" Perl DBI read for Oracle 395 t/s +---------------------------------------------------------------------- + +Only batching had a statistically significant improvement, and it +wasn't that major. I couldn't use true Postgres prepared statements +since you cannot determine the success/failure of the statements yet. +I was planning on using arrays as well, but the additional 33% +performance impact is not amusing (though I suppose it is only an +additional 3% if you consider the 87% performance drop of Postgres +from Oracle). + +I'll include all methods in the attached file, but since there was no +significant difference, I'll concentrate on the basic one: + +Example table: +---------------------------------------------------------------------- +CREATE TABLE test ( + val BIGINT PRIMARY KEY, # "vals" may be between 0 and 2^32-1 + accum INTEGER +); +---------------------------------------------------------------------- + +Basic algorithm for writes +---------------------------------------------------------------------- + while (<>) + { + chomp; + @A = split; + + if (dosql($dbh, "UPDATE test SET accum = accum + $A[1] WHERE val = '$A[0]';",0) eq "0E0") + { + dosql($dbh, "INSERT INTO test VALUES ( $A[0], $A[1] );"); + } + } +---------------------------------------------------------------------- + +Basic algorithm for reads +---------------------------------------------------------------------- +while (<>) +{ + chomp; + @A = split; + $sth = querysql($dbh,"SELECT accum FROM test WHERE val = $A[0];"); + $hit++ if ($sth && ($row = $sth->fetchrow_arrayref)); + $tot++; +} +---------------------------------------------------------------------- + +What could be simpler. + +In my randomly generated write data, I usually have about 18K inserts +and 82K updates. In my randomly generated read data, I have 100K keys +which will be found and 100K keys which will not be found. + +The postgresql.conf file is default (my sysadmin nuked all of my +changes when he upgraded to 7.3.1--grr) and there are some shared +memory configs: kernel.sem = 250 32000 100 128, kernel.shmmax = +2147483648, kernel.shmmni = 100, kernel.shmmax = 134217728 The +WAL is not seperated (but see below). + +A "vacuum analyze" is performed between the write phase and the read +phase. However, for your analysis pleasure, here are the results +of a full verbose analyze and some explain results (both before and after). + +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ +seth=> explain update test set accum = accum + 53 where val = '5'; + QUERY PLAN +----------------------------------------------------- + Seq Scan on test (cost=0.00..0.00 rows=1 width=18) + Filter: (val = 5::bigint) +(2 rows) +seth=> explain insert into test values (5, 53); + QUERY PLAN +------------------------------------------ + Result (cost=0.00..0.01 rows=1 width=0) +(1 row) +seth=> vacuum full verbose analyze test; +INFO: --Relation public.test-- +INFO: Pages 541: Changed 2, reaped 540, Empty 0, New 0; Tup 18153: Vac 81847, Keep/VTL 0/0, UnUsed 0, MinLen 40, MaxLen 40; Re-using: Free/Avail. Space 3294932/3294932; EndEmpty/Avail. Pages 0/541. + CPU 0.00s/0.03u sec elapsed 0.02 sec. +INFO: Index test_pkey: Pages 355; Tuples 18153: Deleted 81847. + CPU 0.03s/0.34u sec elapsed 0.65 sec. +INFO: Rel test: Pages: 541 --> 99; Tuple(s) moved: 18123. + CPU 1.01s/0.31u sec elapsed 9.65 sec. +INFO: Index test_pkey: Pages 355; Tuples 18153: Deleted 18123. + CPU 0.02s/0.06u sec elapsed 0.19 sec. +INFO: Analyzing public.test +VACUUM + +seth=> explain select accum from test where val = 5; + QUERY PLAN +---------------------------------------------------------------------- + Index Scan using test_pkey on test (cost=0.00..5.99 rows=1 width=4) + Index Cond: (val = 5) +(2 rows) +seth=> explain update test set accum = accum + 53 where val = '5'; + QUERY PLAN +----------------------------------------------------------------------- + Index Scan using test_pkey on test (cost=0.00..5.99 rows=1 width=18) + Index Cond: (val = 5::bigint) +(2 rows) +seth=> explain insert into test values (5, 53); + QUERY PLAN +------------------------------------------ + Result (cost=0.00..0.01 rows=1 width=0) +(1 row) +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ + +I certainly understand that using an index scan might well speed +things up WRT the update policy, but considering the search +performance is post-analyze (pre-analyze it is even more deadly slow), +I am dubious that doing it during the updates will get me within +striking distance of Oracle since read performance has got to be +better than write performance, right?. This is also why I am dubious +that moving the WAL to another filesystem or futzing with the fsync +policy will do anything. + +I will include below a compressed tarball of the programs I used (and +the corresponding RUNME script) in case you wish to play along at +home. I don't claim they are pretty, BTW :-) + + -Seth Robertson + + +------- =_aaaaaaaaaa0 +Content-Type: application/tar; name="perftest.tar.gz" +Content-ID: <20460.1043184020.2@winwood.sysdetect.com> +Content-Transfer-Encoding: base64 + +H4sIALO4LT4AA+09a3vaxtL9Wv2KCSYFbDAX2/H7GNsNwYrjpwQ7gJv0TV1X +oAXUgkR08eWkPr/9zOyuQOJinNR2knYnMUir3ZnZmdXszGhXjJjb9Znn5797 +OCgUNgvbW1v4XShsbz+j72Jxs8TPJXxX2H5W3NjY2Cxt4fVisbSx+R1sPSBP +Ywg833ABvvOY37+tnskuHoOdx4ZRqP/Gab2lN1sPQaNQLNymfyyK6L9A+i9t +bBS+g8JDMDMN/3L9rzzJty077/W1FW0F9CtjOBowGLlOzzWG4DvgBjYYgwHQ +IPGwkoaCghzTsPa7d++gqtebxw3tuFGp1vTzV8ev9b08tv4j77hGZ8A0djVy +XB8i17WTSuvV3vpOkr7DE9Fm5Hh+z2UesbQTRcMLRIP66euf9WrruNHcK/Lh +o50039TOq8f1OhY3W42j+uFeIteHrhtYZmLR1UvHNpmLlw9nLubMdh8ZGSNY +XCNEgr2bV8c2hmyPYwE6DTzm7nUdh5+MDM/baxtLGgsCk9bGZZv0MMEgCxIa +9vKkdtqcxoTk8kjluezLgloSS15+Pw/7FVOxxjp9Bw6ZzVzDZ5CcKAJcwzad +IVj2KPDhgnV8x/U0wpTrYfULZvvro0GsxT7k/eEof7Vu2VDal8dO4Gva1d7v +OGbcWO3UagpKvwsGEpIDy+5B8ooPSzqUVCEdbWcGIy+T0NIdw5/QK8OtnCE3 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+y6PAlA91i98XuixLHL8v3SEFnwTx+9/vBw/wA1BL3/9bnHn/U6n0TN3/jwHf +4vo/KpfO779vc5fsuHoQ+O9+EPhtvwgk3udwSN9MsuG37rMaZ3Fu/2WTmRe5 +kTz/COw/Zx48QvjkMZK6if9sEkaPlXrzrd4Y41YbudSDOvWgTj2oUw/qFChQ +oECBAgUKFChQoECBAgUKFChQoECBAgUKFChQoECBAgUKFChQoECBAgUKFChQ +8EjwP+/zYX4AyAAA + +------- =_aaaaaaaaaa0-- + +From pgsql-performance-owner@postgresql.org Tue Jan 21 16:46:18 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3E8E3475BD7 + for ; + Tue, 21 Jan 2003 16:46:16 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id C57F1475425 + for ; + Tue, 21 Jan 2003 16:46:15 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 1FAA2D605; Tue, 21 Jan 2003 13:46:17 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 114DB5C04; Tue, 21 Jan 2003 13:46:17 -0800 (PST) +Date: Tue, 21 Jan 2003 13:46:17 -0800 (PST) +From: Stephan Szabo +To: Seth Robertson +Cc: +Subject: Re: Postgres 7.3.1 poor insert/update/search performance +In-Reply-To: <200301212120.h0LLKn820463@winwood.sysdetect.com> +Message-ID: <20030121134242.Q84028-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/215 +X-Sequence-Number: 862 + + +On Tue, 21 Jan 2003, Seth Robertson wrote: + +> The postgresql.conf file is default (my sysadmin nuked all of my +> changes when he upgraded to 7.3.1--grr) and there are some shared +> memory configs: kernel.sem = 250 32000 100 128, kernel.shmmax = +> 2147483648, kernel.shmmni = 100, kernel.shmmax = 134217728 The +> WAL is not seperated (but see below). + +You almost certainly want to raise shared_buffers from the default (64?) +to say 1k-10k. I'm not sure how much that'll help but it should help +some. + +> A "vacuum analyze" is performed between the write phase and the read +> phase. However, for your analysis pleasure, here are the results +> of a full verbose analyze and some explain results (both before and after). + +BTW: what does explain analyze (rather than plain explain) show? + + +From pgsql-performance-owner@postgresql.org Tue Jan 21 17:09:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5D38E4762DE + for ; + Tue, 21 Jan 2003 17:09:51 -0500 (EST) +Received: from martin.sysdetect.com (martin.sysdetect.com [65.209.102.1]) + by postgresql.org (Postfix) with ESMTP id 25952475CE7 + for ; + Tue, 21 Jan 2003 17:07:25 -0500 (EST) +Received: (from mail@localhost) + by martin.sysdetect.com (8.11.3/8.11.3) id h0LM7IR12412; + Tue, 21 Jan 2003 22:07:18 GMT +Received: from winwood.sysdetect.com(172.16.1.1) + via SMTP by mail.sysdetect.com, id smtpdx15237; Tue Jan 21 22:07:15 2003 +Received: from winwood.sysdetect.com (seth@localhost) + by winwood.sysdetect.com (8.11.6/8.11.6) with ESMTP id h0LM7Dt21080; + Tue, 21 Jan 2003 17:07:13 -0500 +Message-Id: <200301212207.h0LM7Dt21080@winwood.sysdetect.com> +To: pgsql-performance@postgresql.org +Cc: Stephan Szabo +From: Seth Robertson +Subject: Re: Postgres 7.3.1 poor insert/update/search performance +In-reply-to: <20030121134242.Q84028-100000@megazone23.bigpanda.com> +References: <200301212120.h0LLKn820463> + <20030121134242.Q84028-100000@megazone23.bigpanda.com> +Comments: In reply to a message from "Stephan Szabo + " dated "Tue, + 21 Jan 2003 13:46:17 -0800." +Date: Tue, 21 Jan 2003 17:07:13 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/216 +X-Sequence-Number: 863 + + +In message <20030121134242.Q84028-100000@megazone23.bigpanda.com>, Stephan Szabo writes: + + On Tue, 21 Jan 2003, Seth Robertson wrote: + + > The postgresql.conf file is default (my sysadmin nuked all of my + > changes when he upgraded to 7.3.1--grr) and there are some shared + > memory configs: kernel.sem = 250 32000 100 128, kernel.shmmax = + > 2147483648, kernel.shmmni = 100, kernel.shmmax = 134217728 The + > WAL is not seperated (but see below). + + You almost certainly want to raise shared_buffers from the default (64?) + to say 1k-10k. I'm not sure how much that'll help but it should help + some. + +I'll try that and report back later, but I was under the (false?) +impression that it was primarily important when you had multiple +database connections using the same table. + + > A "vacuum analyze" is performed between the write phase and the + > read phase. However, for your analysis pleasure, here are the + > results of a full verbose analyze and some explain results (both + > before and after). + + BTW: what does explain analyze (rather than plain explain) show? + + +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ +seth=> explain analyze select accum from test where val = 5; + QUERY PLAN +---------------------------------------------------------------------------------------------- + Seq Scan on test (cost=0.00..0.00 rows=1 width=4) (actual time=94.55..94.55 rows=0 loops=1) + Filter: (val = 5) + Total runtime: 99.20 msec +(3 rows) + +seth=> explain analyze update test set accum = accum + 53 where val = '5'; + QUERY PLAN +----------------------------------------------------------------------------------------------- + Seq Scan on test (cost=0.00..0.00 rows=1 width=18) (actual time=31.95..31.95 rows=0 loops=1) + Filter: (val = 5::bigint) + Total runtime: 32.04 msec +(3 rows) + +seth=> explain analyze insert into test values (5, 53); + QUERY PLAN +---------------------------------------------------------------------------------- + Result (cost=0.00..0.01 rows=1 width=0) (actual time=0.01..0.01 rows=1 loops=1) + Total runtime: 7.50 msec +(2 rows) + +seth=> vacuum full verbose analyze test +seth-> ; +INFO: --Relation public.test-- +INFO: Pages 541: Changed 1, reaped 539, Empty 0, New 0; Tup 18071: Vac 81930, Keep/VTL 0/0, UnUsed 0, MinLen 40, MaxLen 40; Re-using: Free/Avail. Space 3298208/3298176; EndEmpty/Avail. Pages 0/540. + CPU 0.03s/0.00u sec elapsed 0.02 sec. +INFO: Index test_pkey: Pages 355; Tuples 18071: Deleted 81930. + CPU 0.04s/0.41u sec elapsed 1.96 sec. +INFO: Rel test: Pages: 541 --> 98; Tuple(s) moved: 18046. + CPU 0.95s/0.42u sec elapsed 12.74 sec. +INFO: Index test_pkey: Pages 355; Tuples 18071: Deleted 18046. + CPU 0.02s/0.05u sec elapsed 0.31 sec. +INFO: Analyzing public.test +VACUUM +seth=> explain analyze select accum from test where val = 5; + QUERY PLAN +----------------------------------------------------------------------------------------------- + Seq Scan on test (cost=0.00..323.89 rows=1 width=4) (actual time=0.13..14.20 rows=1 loops=1) + Filter: (val = 5) + Total runtime: 14.26 msec +(3 rows) + +seth=> explain analyze select accum from test where val = 2147483648; + QUERY PLAN +-------------------------------------------------------------------------------------------------------------- + Index Scan using test_pkey on test (cost=0.00..5.99 rows=1 width=4) (actual time=0.11..0.11 rows=0 loops=1) + Index Cond: (val = 2147483648::bigint) + Total runtime: 0.16 msec +(3 rows) + +seth=> explain analyze update test set accum = accum + 53 where val = '5'; + QUERY PLAN +--------------------------------------------------------------------------------------------------------------- + Index Scan using test_pkey on test (cost=0.00..5.99 rows=1 width=18) (actual time=0.24..0.24 rows=1 loops=1) + Index Cond: (val = 5::bigint) + Total runtime: 0.39 msec +(3 rows) + +seth=> explain analyze insert into test values (6, 53); + QUERY PLAN +---------------------------------------------------------------------------------- + Result (cost=0.00..0.01 rows=1 width=0) (actual time=0.01..0.01 rows=1 loops=1) + Total runtime: 0.08 msec +(2 rows) + +seth=> explain analyze insert into test values (2147483647, 53); + QUERY PLAN +---------------------------------------------------------------------------------- + Result (cost=0.00..0.01 rows=1 width=0) (actual time=0.01..0.01 rows=1 loops=1) + Total runtime: 0.33 msec +(2 rows) +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ + + -Seth Robertson + +From pgsql-performance-owner@postgresql.org Tue Jan 21 17:33:38 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8BC6D4767CB + for ; + Tue, 21 Jan 2003 17:33:36 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 90559476B91 + for ; + Tue, 21 Jan 2003 17:31:34 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0LMVZ5u013166; + Tue, 21 Jan 2003 17:31:35 -0500 (EST) +To: Seth Robertson +Cc: pgsql-performance@postgresql.org, + Stephan Szabo +Subject: Re: Postgres 7.3.1 poor insert/update/search performance +In-reply-to: <200301212207.h0LM7Dt21080@winwood.sysdetect.com> +References: <200301212120.h0LLKn820463> + <20030121134242.Q84028-100000@megazone23.bigpanda.com> + <200301212207.h0LM7Dt21080@winwood.sysdetect.com> +Comments: In-reply-to Seth Robertson + message dated "Tue, 21 Jan 2003 17:07:13 -0500" +Date: Tue, 21 Jan 2003 17:31:35 -0500 +Message-ID: <13165.1043188295@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/217 +X-Sequence-Number: 864 + +Seth Robertson writes: +> I'll try that and report back later, but I was under the (false?) +> impression that it was primarily important when you had multiple +> database connections using the same table. + +Definitely false. shared_buffers needs to be 1000 or so for +production-grade performance. There are varying schools of thought +about whether it's useful to raise it even higher, but in any case +64 is just a toy-installation setting. + +> seth=> explain analyze select accum from test where val = 5; +> QUERY PLAN +> ----------------------------------------------------------------------------------------------- +> Seq Scan on test (cost=0.00..323.89 rows=1 width=4) (actual time=0.13..14.20 rows=1 loops=1) +> Filter: (val = 5) +> Total runtime: 14.26 msec +> (3 rows) + +> seth=> explain analyze update test set accum = accum + 53 where val = '5'; +> QUERY PLAN +> --------------------------------------------------------------------------------------------------------------- +> Index Scan using test_pkey on test (cost=0.00..5.99 rows=1 width=18) (actual time=0.24..0.24 rows=1 loops=1) +> Index Cond: (val = 5::bigint) +> Total runtime: 0.39 msec +> (3 rows) + +The quotes are important when you are dealing with BIGINT indexes. +You won't get an indexscan if the constant looks like int4 rather than int8. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Jan 21 20:44:47 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A6FC4475EF9 + for ; + Tue, 21 Jan 2003 20:44:45 -0500 (EST) +Received: from homer.berkhirt.com (unknown [207.88.49.100]) + by postgresql.org (Postfix) with ESMTP id 9A03C475F85 + for ; + Tue, 21 Jan 2003 20:44:44 -0500 (EST) +Received: from mobygames.com (fwbhirt.independence.net [204.144.177.199]) + (authenticated bits=0) + by homer.berkhirt.com (8.12.6/8.12.6) with ESMTP id h0M1iVI0029060 + (version=TLSv1/SSLv3 cipher=DES-CBC3-SHA bits=168 verify=NO); + Tue, 21 Jan 2003 19:44:33 -0600 +Date: Tue, 21 Jan 2003 18:44:57 -0700 +Subject: Re: Postgres 7.3.1 poor insert/update/search performance +Content-Type: text/plain; delsp=yes; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: bhirt@mobygames.com +To: pgsql-performance@postgresql.org +From: Brian Hirt +In-Reply-To: <13165.1043188295@sss.pgh.pa.us> +Message-Id: <1CE2D1AE-2DAB-11D7-BE6C-000393D9FD00@mobygames.com> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/218 +X-Sequence-Number: 865 + +Tom and others: + +There has been a lot of talk about shared memory size recently, along +with many conflicting statements from various people. Earlier threads +said that setting the shared buffer to a high values (like 512MB on a +2GB dedicated DB server) is not a good idea. A couple of reasons were +mentioned. a) potential inefficiencies with the kernel and VM system +b) modern kernels aggressive caching with all free memory and c) the +shared memory stealing from memory the kernel would use to cache, etc. + +So my question is: if the kernel is caching all this data, what's the +benefit of setting this to 1000 or higher? Why wouldn't i just set it +to 0 if I believe my kernel is doing a good job. + + + From all the discussion on this topic, it's still not clear to me how +to calculate what value this should be set at and why. I've read these +documents and others and have yet to find explanations and +recommendations that i can use. + +http://www.postgresql.org/docs/momjian/hw_performance.pdf +http://www.postgresql.org/idocs/index.php?runtime-config.html +http://www.postgresql.org/idocs/index.php?kernel-resources.html +http://www.postgresql.org/idocs/index.php?performance-tips.html +http://www.ca.postgresql.org/docs/momjian/hw_performance/node6.html +http://www.ca.postgresql.org/docs/momjian/hw_performance/node5.html +http://www.ca.postgresql.org/docs/faq-english.html#3.6 + +This is such a common topic, it would be nice to see a more definitive +and comprehensive section in the docs for tuning. Google searches for +"shared_buffers site:www.postgresql.org" and "tuning +site:www.postgresql.org" come up with little info. + +FYI: I've been running our database which is mostly read only with 1500 +buffers. On a whole, we see very little IO. postgresql performs +many many million queries a day, many simple, many complex. Though the +database is relatively small, around 3GB. + +--brian + +On Tuesday, January 21, 2003, at 03:31 PM, Tom Lane wrote: + +> Seth Robertson writes: +>> I'll try that and report back later, but I was under the (false?) +>> impression that it was primarily important when you had multiple +>> database connections using the same table. +> +> Definitely false. shared_buffers needs to be 1000 or so for +> production-grade performance. There are varying schools of thought +> about whether it's useful to raise it even higher, but in any case +> 64 is just a toy-installation setting. +> +>> seth=> explain analyze select accum from test where val = 5; +>> QUERY PLAN +>> ---------------------------------------------------------------------- +>> ------------------------- +>> Seq Scan on test (cost=0.00..323.89 rows=1 width=4) (actual +>> time=0.13..14.20 rows=1 loops=1) +>> Filter: (val = 5) +>> Total runtime: 14.26 msec +>> (3 rows) +> +>> seth=> explain analyze update test set accum = accum + 53 where val = +>> '5'; +>> QUERY PLAN +>> ---------------------------------------------------------------------- +>> ----------------------------------------- +>> Index Scan using test_pkey on test (cost=0.00..5.99 rows=1 +>> width=18) (actual time=0.24..0.24 rows=1 loops=1) +>> Index Cond: (val = 5::bigint) +>> Total runtime: 0.39 msec +>> (3 rows) +> +> The quotes are important when you are dealing with BIGINT indexes. +> You won't get an indexscan if the constant looks like int4 rather than +> int8. +> +> regards, tom lane +> +> ---------------------------(end of +> broadcast)--------------------------- +> TIP 2: you can get off all lists at once with the unregister command +> (send "unregister YourEmailAddressHere" to +> majordomo@postgresql.org) + + +From pgsql-performance-owner@postgresql.org Tue Jan 21 21:50:39 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 211F047627A + for ; + Tue, 21 Jan 2003 21:50:37 -0500 (EST) +Received: from web80302.mail.yahoo.com (web80302.mail.yahoo.com + [66.218.79.18]) + by postgresql.org (Postfix) with SMTP id 74195476256 + for ; + Tue, 21 Jan 2003 21:50:35 -0500 (EST) +Message-ID: <20030122025039.18791.qmail@web80302.mail.yahoo.com> +Received: from [203.87.150.116] by web80302.mail.yahoo.com via HTTP; + Tue, 21 Jan 2003 18:50:39 PST +Date: Tue, 21 Jan 2003 18:50:39 -0800 (PST) +From: Ludwig Lim +Subject: Performance between triggers/functions written in C and PL/PGSQL +To: PostgreSQL Mailing List +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/219 +X-Sequence-Number: 866 + +Hi: + + + Has anyone done performance comparison between +triggers/functions in C vs. PL/PGSQL? + + What are the drawbacks of functions written using +C? + + +ludwig. + + + +__________________________________________________ +Do you Yahoo!? +New DSL Internet Access from SBC & Yahoo! +http://sbc.yahoo.com + +From pgsql-performance-owner@postgresql.org Wed Jan 22 02:19:52 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7213C475FBF + for ; + Wed, 22 Jan 2003 02:19:51 -0500 (EST) +Received: from martin.sysdetect.com (martin.sysdetect.com [65.209.102.1]) + by postgresql.org (Postfix) with ESMTP id A1CE347592C + for ; + Wed, 22 Jan 2003 02:19:50 -0500 (EST) +Received: (from mail@localhost) + by martin.sysdetect.com (8.11.3/8.11.3) id h0M7JnB04192; + Wed, 22 Jan 2003 07:19:49 GMT +Received: from winwood.sysdetect.com(172.16.1.1) + via SMTP by mail.sysdetect.com, id smtpdBs5148; Wed Jan 22 07:19:45 2003 +Received: from winwood.sysdetect.com (seth@localhost) + by winwood.sysdetect.com (8.11.6/8.11.6) with ESMTP id h0M7JjA04509; + Wed, 22 Jan 2003 02:19:45 -0500 +Message-Id: <200301220719.h0M7JjA04509@winwood.sysdetect.com> +From: Seth Robertson +Cc: pgsql-performance@postgresql.org, + Stephan Szabo +Subject: Re: Postgres 7.3.1 poor insert/update/search performance +In-reply-to: <13165.1043188295@sss.pgh.pa.us> +References: <200301212120.h0LLKn820463> + <20030121134242.Q84028-100000@megazone23.bigpanda.com> + <200301212207.h0LM7Dt21080@winwood.sysdetect.com> + <13165.1043188295@sss.pgh.pa.us> +Comments: In reply to a message from "Tom Lane " dated + "Tue, + 21 Jan 2003 17:31:35 -0500." +Date: Wed, 22 Jan 2003 02:19:45 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/220 +X-Sequence-Number: 867 + + +In message <13165.1043188295@sss.pgh.pa.us>, Tom Lane writes: + + Seth Robertson writes: + > I'll try that and report back later, but I was under the (false?) + > impression that it was primarily important when you had multiple + > database connections using the same table. + + Definitely false. shared_buffers needs to be 1000 or so for + production-grade performance. There are varying schools of thought + about whether it's useful to raise it even higher, but in any case + 64 is just a toy-installation setting. + +Increasing the setting to 4096 improved write performance by 20%. +Increasing the setting to 8192 had no additional effect. I could try +a few more probes if anyone cared. + + The quotes are important when you are dealing with BIGINT indexes. + You won't get an indexscan if the constant looks like int4 rather + than int8. + +You are not kidding!!!! Changing this increased the search +performance to 2083 transactions/second. This is 30 times faster than +before, and 5 times faster than Oracle! Go Tom Lane!!! + +Unfortunately, the update accidentally already used the quoting, so +this top did not directly help the write case. However, it did +inspire me to check some other suggestions I have read since obviously +performance was to be had. + +---------------------------------------------------------------------- +Oracle read performance: 395 +Original read performance: 69 +shared_buffer = 4096 118 ++ quoted where (WHERE val = '5') 2083 +---------------------------------------------------------------------- + +---------------------------------------------------------------------- +Oracle write performance: 314 +Original write performance: 39 +shared_buffer = 4096: 47 ++ Occassional (@ 10K & 60K vectors) vacuum analyze in bg: 121 ++ Periodic (every 10K vectors) vacuum analyze in background: 124 ++ wal_buffers = 24: 125 ++ wal_method = fdatasync 127 ++ wal_method = open_sync 248 ++ wal_method = open_datasync Not Supported ++ fsync=false: 793 +---------------------------------------------------------------------- + +Just to round out my report, using the fastest safe combination I was +able to find (open_sync *is* safe, isn't it?), I reran all 7 +performance tests to see if there was any different using the +different access methods: + +---------------------------------------------------------------------- +"normal" C libpq 256 t/s +"normal" Perl DBI 251 t/s +"DBI Prepared Statement" Perl DBI 254 t/s +"Batching" Perl DBI 1149 t/s +"arrays" Perl DBI 43 t/s +"server-side function" Perl DBI 84 t/s +"server-side trigger" Perl DBI 84 t/s +"normal" Perl DBI read 1960 t/s +"normal" Perl DBI for Oracle 314 t/s +"normal" Perl DBI read for Oracle 395 t/s +---------------------------------------------------------------------- + +With a batching update of 1149 transactions per second (2900% +improvement), I am willing to call it a day unless anyone else has any +brilliant ideas. However, it looks like my hope to use arrays is +doomed though, I'm not sure I can handle the performance penalty. + + -Seth Robertson + +From pgsql-general-owner@postgresql.org Wed Jan 22 05:30:35 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EE7CF475DC5 + for ; + Wed, 22 Jan 2003 05:30:32 -0500 (EST) +Received: from biomax.de (unknown [212.6.137.236]) + by postgresql.org (Postfix) with ESMTP id A82A2475BC3 + for ; + Wed, 22 Jan 2003 05:30:31 -0500 (EST) +Received: from biomax.de (guffert.biomax.de [192.168.3.166]) + by biomax.de (8.8.8/8.8.8) with ESMTP id LAA32055 + for ; Wed, 22 Jan 2003 11:30:32 +0100 +Message-ID: <3E2E72C8.2080703@biomax.de> +Date: Wed, 22 Jan 2003 11:30:32 +0100 +From: Chantal Ackermann +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: pgsql-general@postgresql.org +Subject: optimizing query +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/854 +X-Sequence-Number: 35975 + +hello all, + +I am getting the following output from EXPLAIN, concerning a query with +joins. The merge uses index scans but takes too long, in my opinion. The +query is in fact only a part (subquery) of another one, but it is the +bottle neck. + +As I am quite ignorant in optimizing queries, and I have no idea where +to find documentation on the net on how to learn optimizing my queries, +I am posting this here in hope someone will give me either tips how to +optimize, or where to find some tutorial that could help me get along on +my own. + +dropping the "DISTINCT" has some effect, but I can't really do without. + +Thank you +Chantal + ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + +relate=# explain SELECT DISTINCT gene.gene_name, +gene_occurrences_puid.puid FROM disease, gene, disease_occurrences_puid, +gene_occurrences_puid WHERE +disease_occurrences_puid.puid=gene_occurrences_puid.puid AND +disease.disease_id=disease_occurrences_puid.disease_id AND +gene.gene_id=gene_occurrences_puid.gene_id; + QUERY PLAN +------------------------------------------------------------------------------------------------------------------------------------------ + Unique (cost=426503.59..436839.47 rows=137812 width=41) + -> Sort (cost=426503.59..429948.88 rows=1378118 width=41) + Sort Key: gene.gene_name, gene_occurrences_puid.puid + -> Hash Join (cost=67813.96..162375.07 rows=1378118 width=41) + Hash Cond: ("outer".disease_id = "inner".disease_id) + -> Merge Join (cost=63671.50..98237.36 rows=1378118 +width=37) + Merge Cond: ("outer".puid = "inner".puid) + -> Index Scan using disease_occpd_puid_i on +disease_occurrences_puid (cost=0.00..14538.05 rows=471915 width=8) + -> Sort (cost=63671.50..64519.87 rows=339347 +width=29) + Sort Key: gene_occurrences_puid.puid + -> Merge Join (cost=0.00..22828.18 +rows=339347 width=29) + Merge Cond: ("outer".gene_id = +"inner".gene_id) + -> Index Scan using gene_pkey on gene + (cost=0.00..7668.59 rows=218085 width=21) + -> Index Scan using gene_id_puid_uni +on gene_occurrences_puid (cost=0.00..9525.57 rows=339347 width=8) + -> Hash (cost=3167.97..3167.97 rows=164597 width=4) + -> Seq Scan on disease (cost=0.00..3167.97 +rows=164597 width=4) +(16 rows) + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 07:05:23 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 44707475CA9 + for ; + Wed, 22 Jan 2003 07:05:22 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id ADA1B475BC3 + for ; + Wed, 22 Jan 2003 07:05:21 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18bJdE-00029x-00 + for ; Wed, 22 Jan 2003 07:05:24 -0500 +Date: Wed, 22 Jan 2003 07:05:24 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: Postgres 7.3.1 poor insert/update/search performance +Message-ID: <20030122070524.F27014@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <13165.1043188295@sss.pgh.pa.us> + <1CE2D1AE-2DAB-11D7-BE6C-000393D9FD00@mobygames.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <1CE2D1AE-2DAB-11D7-BE6C-000393D9FD00@mobygames.com>; + from bhirt@mobygames.com on Tue, Jan 21, 2003 at 06:44:57PM -0700 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/221 +X-Sequence-Number: 868 + +On Tue, Jan 21, 2003 at 06:44:57PM -0700, Brian Hirt wrote: +> +> So my question is: if the kernel is caching all this data, what's the +> benefit of setting this to 1000 or higher? Why wouldn't i just set it +> to 0 if I believe my kernel is doing a good job. + +If Postgres tries to fetch a bit of data which is in its own shared +buffer, it does not even need to make a system call in order to fetch +it. The data fetch is extremely fast. + +The problem is that managing that shared memory comes at some cost. + +If the data is not in a shared buffer, then Postgres makes exactly +the same call, no matter what, to the OS kernel, asking for the data +from disk. It might happen, however, that the kernel will have the +data in its disk cache, however. The total cost of the operation, +therefore, is much lower in case the data is in the kernel's disk +cache than in the case where it is actually on the disk. It is +nevertheless still higher (atomically speaking) than fetching the +data from Postgres's own shared buffer. + +So the question is this: where is the "sweet spot" where it costs +little enough for Postgres to manage the shared buffer that the +reduced cost of a system call is worth it. (As you point out, this +caclulation is complicated by the potential to waste memory by +caching the data twice -- once in the shared buffer and once in the +disk cache. Some systems, like Solaris, allow you to turn off the +disk cache, so the problem may not be one you face.) The trouble is +that there is no agreement on the answer to that question, and +precious little evidence which seems to settle the question. + +The only way to determine the best setting, then, is to use your +system with more-or-less simulated production loads, and see where +the best setting lies. You have to do this over time, because +sometimes inefficiencies turn up only after running for a while. In +an experiment we tried, we used a 2G shared buffer on a 12G machine. +It looked brilliantly fast at first, but 48 hours later was +_crawling_; that indicates a problem with shared-buffer management on +the part of Postgres, I guess, but it was hard to say more than that. +We ultimately settled on a value somewhere less than 1 G as +appropriate for our use. But if I had to justify the number I picked +(as opposed to one a few hundred higher or lower), I'd have a tough +time. + +> From all the discussion on this topic, it's still not clear to me how +> to calculate what value this should be set at and why. I've read these +> documents and others and have yet to find explanations and +> recommendations that i can use. + +I'm afraid what I'm saying is that it's a bit of a black art. The +pg_autotune project is an attempt to help make this a little more +scientific. It relies on pgbench, which has its own problems, +however. + +Hope that's helpful, but I fear it doesn't give you the answer you'd +like. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 11:21:14 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A665E476F7C + for ; + Wed, 22 Jan 2003 11:21:13 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 673424759AF + for ; + Wed, 22 Jan 2003 11:09:56 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0MG9x5u019953; + Wed, 22 Jan 2003 11:09:59 -0500 (EST) +To: Brian Hirt +Cc: pgsql-performance@postgresql.org +Subject: Re: Postgres 7.3.1 poor insert/update/search performance +In-reply-to: <1CE2D1AE-2DAB-11D7-BE6C-000393D9FD00@mobygames.com> +References: <1CE2D1AE-2DAB-11D7-BE6C-000393D9FD00@mobygames.com> +Comments: In-reply-to Brian Hirt + message dated "Tue, 21 Jan 2003 18:44:57 -0700" +Date: Wed, 22 Jan 2003 11:09:58 -0500 +Message-ID: <19952.1043251798@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/222 +X-Sequence-Number: 869 + +Brian Hirt writes: +> So my question is: if the kernel is caching all this data, what's the +> benefit of setting this to 1000 or higher? Why wouldn't i just set it +> to 0 if I believe my kernel is doing a good job. + +Well, setting it to 0 won't work ;-). There's some minimum number of +buffers needed for PG to work at all; depending on complexity of your +queries and number of active backends it's probably around 25-100. +(You'll get "out of buffers" failures if too few.) But more to the +point, when shared_buffers is too small you'll waste CPU cycles on +unnecessary data transfers between kernel and user memory. It seems to +be pretty well established that 64 is too small for most applications. +I'm not sure how much is enough, but I suspect that a few thousand is +plenty to get past the knee of the performance curve in most scenarios. + + regards, tom lane + +From pgsql-general-owner@postgresql.org Wed Jan 22 11:33:07 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 3473A476EF0; Wed, 22 Jan 2003 11:33:04 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP + id D6850476F21; Wed, 22 Jan 2003 11:20:10 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 94101D611; Wed, 22 Jan 2003 08:20:15 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 89BC25C03; Wed, 22 Jan 2003 08:20:15 -0800 (PST) +Date: Wed, 22 Jan 2003 08:20:15 -0800 (PST) +From: Stephan Szabo +To: Chantal Ackermann +Cc: , + +Subject: Re: optimizing query +In-Reply-To: <3E2E72C8.2080703@biomax.de> +Message-ID: <20030122081422.Y96911-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/862 +X-Sequence-Number: 35983 + + +(Replying to general and performance in a hope to move this +to performance after a couple of replies). + +On Wed, 22 Jan 2003, Chantal Ackermann wrote: + +> I am getting the following output from EXPLAIN, concerning a query with +> joins. The merge uses index scans but takes too long, in my opinion. The +> query is in fact only a part (subquery) of another one, but it is the +> bottle neck. +> +> As I am quite ignorant in optimizing queries, and I have no idea where +> to find documentation on the net on how to learn optimizing my queries, +> I am posting this here in hope someone will give me either tips how to +> optimize, or where to find some tutorial that could help me get along on +> my own. +> +> dropping the "DISTINCT" has some effect, but I can't really do without. + +The first thing is, have you done ANALYZE recently to make sure that the +statistics are correct and what does EXPLAIN ANALYZE give you (that will +run the query and give the estimate and actual). Also, if you haven't +vacuumed recently, you may want to vacuum full. + +How many rows are there on gene, disease and both occurrances tables? +I'd wonder if perhaps using explicit sql join syntax (which postgres uses +to constrain order) to join disease and disease_occurrences_puid before +joining it to the other two would be better or worse in practice. + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 13:15:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 68BB4476391 + for ; + Wed, 22 Jan 2003 13:15:07 -0500 (EST) +Received: from martin.sysdetect.com (martin.sysdetect.com [65.209.102.1]) + by postgresql.org (Postfix) with ESMTP id D5F28476E57 + for ; + Wed, 22 Jan 2003 12:45:21 -0500 (EST) +Received: (from mail@localhost) + by martin.sysdetect.com (8.11.3/8.11.3) id h0MHjPJ23547 + for ; Wed, 22 Jan 2003 17:45:25 GMT +Received: from winwood.sysdetect.com(172.16.1.1) + via SMTP by mail.sysdetect.com, id smtpdZ15586; Wed Jan 22 17:45:24 2003 +Received: from winwood.sysdetect.com (seth@localhost) + by winwood.sysdetect.com (8.11.6/8.11.6) with ESMTP id h0MHjOs14488 + for ; Wed, 22 Jan 2003 12:45:24 -0500 +Message-Id: <200301221745.h0MHjOs14488@winwood.sysdetect.com> +From: Seth Robertson +To: pgsql-performance@postgresql.org +Subject: Re: Postgres 7.3.1 poor insert/update/search performance +References: <200301212120.h0LLKn820463> + <20030121134242.Q84028-100000@megazone23.bigpanda.com> + <200301212207.h0LM7Dt21080@winwood.sysdetect.com> + <13165.1043188295@sss.pgh.pa.us> +Comments: In reply to a message from "Seth Robertson + " dated "Wed, + 22 Jan 2003 02:19:45 -0500." +Date: Wed, 22 Jan 2003 12:45:24 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/224 +X-Sequence-Number: 871 + + +Seth Robertson writes: + + + However, it looks like my hope to use arrays is + doomed though, I'm not sure I can handle the performance penalty. + +Just in case I get the person who implemented arrays annoyed or +worried, I did not properly modify the "array" test and was vacuum'ing +the wrong table every 10000 vectors during the test. I realized that +this morning and the new array results are listed below. I also +experimented with batching read operations, and I was surprised to find +that this helps a great deal as well. + +---------------------------------------------------------------------- +"normal" C libpq 256 t/s +"normal" Perl DBI 251 t/s +"DBI Prepared Statement" Perl DBI 254 t/s +"Batching" Perl DBI 1149 t/s +"arrays" Perl DBI 250 t/s (*) +"arrays with batching" Perl DBI 1020 t/s (*) +"server-side function" Perl DBI 84 t/s +"server-side trigger" Perl DBI 84 t/s +"normal" Perl DBI read 1960 t/s +"batched" Perl DBI read 3076 t/s (*) +"array" Perl DBI read 1754 t/s (*) +"batched array" Perl DBI read 2702 t/s (*) +"normal" Perl DBI for Oracle 314 t/s +"normal" Perl DBI read for Oracle 395 t/s +---------------------------------------------------------------------- +(*) New/updated from this morning + +This brings array code to within 11% of the performance of batched +non-arrays, and close enough to be an option. I may well be doing +something wrong with the server-side functions, but I don't see +anything quite so obviously wrong. + + -Seth Robertson + +From pgsql-performance-owner@postgresql.org Wed Jan 22 13:56:46 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3F211476EF0 + for ; + Wed, 22 Jan 2003 13:56:46 -0500 (EST) +Received: from fddlnint05.fds.com (fddlnint05.fds.com [208.15.91.52]) + by postgresql.org (Postfix) with ESMTP id 38810476F09 + for ; + Wed, 22 Jan 2003 13:30:42 -0500 (EST) +Subject: Slow query on OS X box +To: pgsql-performance@postgresql.org +X-Mailer: Lotus Notes Release 5.0.8 June 18, 2001 +Message-ID: +From: "Patrick Hatcher" +Date: Wed, 22 Jan 2003 10:26:17 -0800 +X-MIMETrack: Serialize by Router on FDDLNINT05/FSG/SVR/FDD(Release 5.0.4 |June + 8, 2000) at 01/22/2003 01:27:40 PM +MIME-Version: 1.0 +Content-type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/225 +X-Sequence-Number: 872 + +I have a table that contains over 13 million rows. This query takes an +extremely long time to return. I've vacuum full, analyzed, and re-indexed +the table. Still the results are the same. Any ideas? +TIA +Patrick + +mdc_oz=# explain analyze select wizard from search_log where wizard +='Keyword' and sdate between '2002-12-01' and '2003-01-15'; + QUERY PLAN +----------------------------------------------------------------------------------------------------------------------------- + Seq Scan on search_log (cost=0.00..609015.34 rows=3305729 width=10) +(actual time=99833.83..162951.25 rows=3280573 loops=1) + Filter: ((wizard = 'Keyword'::character varying) AND (sdate > += '2002-12-01'::date) AND (sdate <= '2003-01-15'::date)) + Total runtime: 174713.25 msec +(3 rows) + +My box I'm running PG on: +Dual 500 Mac OS X +1g ram +Pg 7.3.0 + +Conf settings +max_connections = 200 +shared_buffers = 15200 +#max_fsm_relations = 100 # min 10, fsm is free space map, ~40 bytes +#max_fsm_pages = 10000 # min 1000, fsm is free space map, ~6 bytes +#max_locks_per_transaction = 64 # min 10 +#wal_buffers = 8 # min 4, typically 8KB each + + + + +CREATE TABLE public.search_log ( + wizard varchar(50) NOT NULL, + sub_wizard varchar(50), + timestamp varchar(75), + department int4, + gender varchar(25), + occasion varchar(50), + age varchar(25), + product_type varchar(2000), + price_range varchar(1000), + brand varchar(2000), + keyword varchar(1000), + result_count int4, + html_count int4, + fragrance_type varchar(50), + frag_type varchar(50), + frag_gender char(1), + trip_length varchar(25), + carry_on varchar(25), + suiter varchar(25), + expandable varchar(25), + wheels varchar(25), + style varchar(1000), + heel_type varchar(25), + option varchar(50), + metal varchar(255), + gem varchar(255), + bra_size varchar(25), + feature1 varchar(50), + feature2 varchar(50), + feature3 varchar(50), + sdate date, + stimestamp timestamptz, + file_name text +) WITH OIDS; + +CREATE INDEX date_idx ON search_log USING btree (sdate); +CREATE INDEX slog_wizard_idx ON search_log USING btree (wizard); + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 14:22:16 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 34F7B477031 + for ; + Wed, 22 Jan 2003 14:22:14 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 725094770AD + for ; + Wed, 22 Jan 2003 13:55:02 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2322107; Wed, 22 Jan 2003 10:55:00 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Ludwig Lim , + PostgreSQL Mailing List +Subject: Re: Performance between triggers/functions written in C and PL/PGSQL +Date: Wed, 22 Jan 2003 10:57:29 -0800 +X-Mailer: KMail [version 1.4] +References: <20030122025039.18791.qmail@web80302.mail.yahoo.com> +In-Reply-To: <20030122025039.18791.qmail@web80302.mail.yahoo.com> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301221057.29207.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/226 +X-Sequence-Number: 873 + + +Ludwig, + +> Has anyone done performance comparison between +> triggers/functions in C vs. PL/PGSQL? + +On simple ON UPDATE triggers that update an archive table, but are called m= +any=20 +times per minute, about 20:1 in favor of C triggers. Partly that depends o= +n=20 +whether you load the C function as an external file or compile it into the= +=20 +database. The latter is, of course, faster by far less flexible. + +Partly this is because C is fast, being a lower-level language. Partly thi= +s=20 +is because the PL/pgSQL parser is in *desperate* need of an overhaul, as it= +=20 +was written in a hurry and has since suffered incremental development. + +> What are the drawbacks of functions written using +> C? + +Writing C is harder. Gotta manage your own memory. Plus a badly written C= +=20 +function can easily crash Postgres, whereas that's much harder to do with= +=20 +PL/pgSQL. + +Usually I just write the original Trigger in PL/pgSQL, test & debug for dat= +a=20 +errors, and then farm it out to a crack C programmer to convert to C. + + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 15:27:42 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E9457476F70 + for ; + Wed, 22 Jan 2003 15:27:38 -0500 (EST) +Received: from jester.senspire.com + (CPE00508b028d7d-CM00803785c5e0.cpe.net.cable.rogers.com + [24.103.51.175]) + by postgresql.org (Postfix) with ESMTP id 31C9A47678E + for ; + Wed, 22 Jan 2003 15:02:16 -0500 (EST) +Received: from [127.0.0.1] (localhost [127.0.0.1]) + by jester.senspire.com (8.12.6/8.12.6) with ESMTP id h0MK25YJ059162; + Wed, 22 Jan 2003 15:02:05 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: Slow query on OS X box +From: Rod Taylor +To: Patrick Hatcher +Cc: Postgresql Performance +In-Reply-To: +References: +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-3K4M2hH3Gjt/xjJBmSiX" +Organization: +Message-Id: <1043265724.83856.147.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 22 Jan 2003 15:02:05 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/227 +X-Sequence-Number: 874 + +--=-3K4M2hH3Gjt/xjJBmSiX +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +On Wed, 2003-01-22 at 13:26, Patrick Hatcher wrote: +> I have a table that contains over 13 million rows. This query takes an +> extremely long time to return. I've vacuum full, analyzed, and re-indexed +> the table. Still the results are the same. Any ideas? + +Yeah, you're pulling out 3.2 million rows from (possibly) a wide table +bytewise. Do all of those fields actually have data? Thats always +going to take a while -- and I find it hard to believe you're actually +doing something with all of those rows that runs regularly. + +If every one of those rows was maxed out (ignoring the text field at the +end) you could have ~ 15GB of data to pull out. Without knowing the +type of data actually in the table, I'm going to bet it's a harddrive +limitation. + +The index on 'wizard' is next to useless as at least 1/4 of the data in +the table is under the same key. You might try a partial index on +'wizard' (skip the value 'Keyword'). It won't help this query, but +it'll help ones looking for values other than 'Keyword'. + +Anyway, you might try a CURSOR. Fetch rows out 5000 at a time, do some +work with them, then grab some more. This -- more or less -- will allow +you to process the rows received while awaiting the remaining lines to +be processed by the database. Depending on what you're doing with them +it'll give a chance for the diskdrive to catch up. If the kernels smart +it'll read ahead of the scan. This doesn't remove read time, but hides +it while you're transferring the data out (from the db to your client) +or processing it. + +> mdc_oz=3D# explain analyze select wizard from search_log where wizard +> =3D'Keyword' and sdate between '2002-12-01' and '2003-01-15'; +> QUERY PLAN +> -------------------------------------------------------------------------= +---------------------------------------------------- +> Seq Scan on search_log (cost=3D0.00..609015.34 rows=3D3305729 width=3D1= +0) +> (actual time=3D99833.83..162951.25 rows=3D3280573 loops=3D1) +> Filter: ((wizard =3D 'Keyword'::character varying) AND (sdate > +> =3D '2002-12-01'::date) AND (sdate <=3D '2003-01-15'::date)) +> Total runtime: 174713.25 msec +> (3 rows) +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-3K4M2hH3Gjt/xjJBmSiX +Content-Type: application/pgp-signature; name=signature.asc +Content-Description: This is a digitally signed message part + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (FreeBSD) + +iD8DBQA+Lvi76DETLow6vwwRAk3jAJ4gFieqU+UzgBQppmLx9Hhbp0A1nwCggud0 +bS/lcI4nTc8OHQpTVQ+YB60= +=pSvF +-----END PGP SIGNATURE----- + +--=-3K4M2hH3Gjt/xjJBmSiX-- + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 16:10:25 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id AE9A4476FF4 + for ; + Wed, 22 Jan 2003 16:10:23 -0500 (EST) +Received: from lakemtao01.cox.net (lakemtao01.cox.net [68.1.17.244]) + by postgresql.org (Postfix) with ESMTP id 5BDAA476FFA + for ; + Wed, 22 Jan 2003 15:35:27 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao01.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030122203528.CDZB16369.lakemtao01.cox.net@[192.168.1.1]> + for ; + Wed, 22 Jan 2003 15:35:28 -0500 +Subject: Re: Slow query on OS X box +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: +References: +Content-Type: text/plain +Organization: +Message-Id: <1043267721.22135.141.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 22 Jan 2003 14:35:22 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/228 +X-Sequence-Number: 875 + +What about creating a multi-segment index on wizard/sdate? + +On a side note: that record is ~8KB long, which is kinda big. You could +split those column into a seperate table (or tables), so that when you +want to query, say, gender, department & trip_length, you won't have to +read in *so*much* extra data, slowing the query down. + +Also, these column sizes seem kind excessive, and allow for bad data to +seep in to the table: + timestamp varchar(75), + age varchar(25), + metal varchar(255), + gem varchar(255), + bra_size varchar(25), + +On Wed, 2003-01-22 at 12:26, Patrick Hatcher wrote: +> I have a table that contains over 13 million rows. This query takes an +> extremely long time to return. I've vacuum full, analyzed, and re-indexed +> the table. Still the results are the same. Any ideas? +> TIA +> Patrick +> +> mdc_oz=# explain analyze select wizard from search_log where wizard +> ='Keyword' and sdate between '2002-12-01' and '2003-01-15'; +> QUERY PLAN +> ----------------------------------------------------------------------------- +> Seq Scan on search_log (cost=0.00..609015.34 rows=3305729 width=10) +> (actual time=99833.83..162951.25 rows=3280573 loops=1) +> Filter: ((wizard = 'Keyword'::character varying) AND (sdate > +> = '2002-12-01'::date) AND (sdate <= '2003-01-15'::date)) +> Total runtime: 174713.25 msec +> (3 rows) +> +> My box I'm running PG on: +> Dual 500 Mac OS X +> 1g ram +> Pg 7.3.0 +> +> Conf settings +> max_connections = 200 +> shared_buffers = 15200 +> #max_fsm_relations = 100 # min 10, fsm is free space map, ~40 bytes +> #max_fsm_pages = 10000 # min 1000, fsm is free space map, ~6 bytes +> #max_locks_per_transaction = 64 # min 10 +> #wal_buffers = 8 # min 4, typically 8KB each +> +> +> +> +> CREATE TABLE public.search_log ( +> wizard varchar(50) NOT NULL, +> sub_wizard varchar(50), +> timestamp varchar(75), +> department int4, +> gender varchar(25), +> occasion varchar(50), +> age varchar(25), +> product_type varchar(2000), +> price_range varchar(1000), +> brand varchar(2000), +> keyword varchar(1000), +> result_count int4, +> html_count int4, +> fragrance_type varchar(50), +> frag_type varchar(50), +> frag_gender char(1), +> trip_length varchar(25), +> carry_on varchar(25), +> suiter varchar(25), +> expandable varchar(25), +> wheels varchar(25), +> style varchar(1000), +> heel_type varchar(25), +> option varchar(50), +> metal varchar(255), +> gem varchar(255), +> bra_size varchar(25), +> feature1 varchar(50), +> feature2 varchar(50), +> feature3 varchar(50), +> sdate date, +> stimestamp timestamptz, +> file_name text +> ) WITH OIDS; +> +> CREATE INDEX date_idx ON search_log USING btree (sdate); +> CREATE INDEX slog_wizard_idx ON search_log USING btree (wizard); +> +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 5: Have you checked our extensive FAQ? +> +> http://www.postgresql.org/users-lounge/docs/faq.html +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "My advice to you is to get married: If you find a good wife, | +| you will be happy; if not, you will become a philosopher." | +| Socrates | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 16:25:55 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1B8C5475D64 + for ; + Wed, 22 Jan 2003 16:25:53 -0500 (EST) +Received: from fddlnint05.fds.com (fddlnint05.fds.com [208.15.91.52]) + by postgresql.org (Postfix) with ESMTP id D80604766F8 + for ; + Wed, 22 Jan 2003 15:54:11 -0500 (EST) +Subject: Re: Slow query on OS X box +To: "Rod Taylor +Cc: Postgresql Performance +X-Mailer: Lotus Notes Release 5.0.8 June 18, 2001 +Message-ID: +From: "Patrick Hatcher" +Date: Wed, 22 Jan 2003 12:49:49 -0800 +X-MIMETrack: Serialize by Router on FDDLNINT05/FSG/SVR/FDD(Release 5.0.4 |June + 8, 2000) at 01/22/2003 03:51:11 PM +MIME-Version: 1.0 +Content-type: multipart/mixed; + Boundary="0__=88256CB6006EA4498f9e8a93df938690918c88256CB6006EA449" +Content-Disposition: inline +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/229 +X-Sequence-Number: 876 + +--0__=88256CB6006EA4498f9e8a93df938690918c88256CB6006EA449 +Content-type: text/plain; charset=us-ascii + + +Sorry I'm being really dense today. I didn't even notice the 3.2 million +row being returned. :( + +To answer your question, no, all fields would not have data. The data we +receive is from a Web log file. It's parsed and then uploaded to this +table. + +I guess the bigger issue is that when trying to do aggregates, grouping by +the wizard field, it takes just as long. + +Ex: +mdc_oz=# explain analyze select wizard,count(wizard) from search_log where +sdate + between '2002-12-01' and '2003-01-15' group by wizard; + QUERY +PLAN +----------------------------------------------------------------------------------------------------------------------------------------------- + Aggregate (cost=1083300.43..1112411.55 rows=388148 width=10) (actual +time=229503.85..302617.75 rows=14 loops=1) + -> Group (cost=1083300.43..1102707.84 rows=3881482 width=10) (actual +time=229503.60..286014.83 rows=3717161 loops=1) + -> Sort (cost=1083300.43..1093004.14 rows=3881482 width=10) +(actual time=229503.57..248415.81 rows=3717161 loops=1) + Sort Key: wizard + -> Seq Scan on search_log (cost=0.00..575217.57 +rows=3881482 width=10) (actual time=91235.76..157559.58 rows=3717161 +loops=1) + Filter: ((sdate >= '2002-12-01'::date) AND (sdate +<= '2003-01-15'::date)) + Total runtime: 302712.48 msec +(7 rows) + +Thanks again for the help +Patrick Hatcher + + + + + + Rod Taylor + To: Patrick Hatcher + cc: Postgresql Performance + 01/22/2003 Subject: Re: [PERFORM] Slow query on OS X box + 12:02 PM + + + + + + +On Wed, 2003-01-22 at 13:26, Patrick Hatcher wrote: +> I have a table that contains over 13 million rows. This query takes an +> extremely long time to return. I've vacuum full, analyzed, and +re-indexed +> the table. Still the results are the same. Any ideas? + +Yeah, you're pulling out 3.2 million rows from (possibly) a wide table +bytewise. Do all of those fields actually have data? Thats always +going to take a while -- and I find it hard to believe you're actually +doing something with all of those rows that runs regularly. + +If every one of those rows was maxed out (ignoring the text field at the +end) you could have ~ 15GB of data to pull out. Without knowing the +type of data actually in the table, I'm going to bet it's a harddrive +limitation. + +The index on 'wizard' is next to useless as at least 1/4 of the data in +the table is under the same key. You might try a partial index on +'wizard' (skip the value 'Keyword'). It won't help this query, but +it'll help ones looking for values other than 'Keyword'. + +Anyway, you might try a CURSOR. Fetch rows out 5000 at a time, do some +work with them, then grab some more. This -- more or less -- will allow +you to process the rows received while awaiting the remaining lines to +be processed by the database. Depending on what you're doing with them +it'll give a chance for the diskdrive to catch up. If the kernels smart +it'll read ahead of the scan. This doesn't remove read time, but hides +it while you're transferring the data out (from the db to your client) +or processing it. + +> mdc_oz=# explain analyze select wizard from search_log where wizard +> ='Keyword' and sdate between '2002-12-01' and '2003-01-15'; +> QUERY PLAN +> +----------------------------------------------------------------------------------------------------------------------------- + +> Seq Scan on search_log (cost=0.00..609015.34 rows=3305729 width=10) +> (actual time=99833.83..162951.25 rows=3280573 loops=1) +> Filter: ((wizard = 'Keyword'::character varying) AND (sdate > +> = '2002-12-01'::date) AND (sdate <= '2003-01-15'::date)) +> Total runtime: 174713.25 msec +> (3 rows) +-- +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc +(See attached file: signature.asc) + + +--0__=88256CB6006EA4498f9e8a93df938690918c88256CB6006EA449 +Content-type: application/octet-stream; + name="signature.asc" +Content-Disposition: attachment; filename="signature.asc" +Content-transfer-encoding: base64 + +LS0tLS1CRUdJTiBQR1AgU0lHTkFUVVJFLS0tLS0NClZlcnNpb246IEdudVBH +IHYxLjIuMSAoRnJlZUJTRCkNCg0KaUQ4REJRQStMdmk3NkRFVExvdzZ2d3dS +QWszakFKNGdGaWVxVStVemdCUXBwbUx4OUhoYnAwQTFud0NnZ3VkMA0KYlMv +bGNJNG5UYzhPSFFwVFZRK1lCNjA9DQo9cFN2Rg0KLS0tLS1FTkQgUEdQIFNJ +R05BVFVSRS0tLS0tDQo= + +--0__=88256CB6006EA4498f9e8a93df938690918c88256CB6006EA449-- + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 16:25:59 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 327284761E9 + for ; + Wed, 22 Jan 2003 16:25:53 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 1C63F476581 + for ; + Wed, 22 Jan 2003 15:54:30 -0500 (EST) +Received: from klaster.net (ph159.krakow.cvx.ppp.tpnet.pl [217.99.208.159]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP + id 461922B864; Wed, 22 Jan 2003 21:50:09 +0100 (CET) +Message-ID: <3E2F060E.9000509@klaster.net> +Date: Wed, 22 Jan 2003 21:58:54 +0100 +From: Tomasz Myrta +User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; + rv:1.2b) Gecko/20021016 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Patrick Hatcher +Cc: pgsql-performance@postgresql.org +Subject: Re: Slow query on OS X box +References: +In-Reply-To: +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/230 +X-Sequence-Number: 877 + +Patrick Hatcher wrote: + +>I have a table that contains over 13 million rows. This query takes an +>extremely long time to return. I've vacuum full, analyzed, and re-indexed +>the table. Still the results are the same. Any ideas? +>TIA +>Patrick +> +>mdc_oz=# explain analyze select wizard from search_log where wizard +>='Keyword' and sdate between '2002-12-01' and '2003-01-15'; +> QUERY PLAN +>----------------------------------------------------------------------------------------------------------------------------- +> Seq Scan on search_log (cost=0.00..609015.34 rows=3305729 width=10) +>(actual time=99833.83..162951.25 rows=3280573 loops=1) +> Filter: ((wizard = 'Keyword'::character varying) AND (sdate > +>= '2002-12-01'::date) AND (sdate <= '2003-01-15'::date)) +> Total runtime: 174713.25 msec +>(3 rows) +> +>My box I'm running PG on: +>Dual 500 Mac OS X +>1g ram +>Pg 7.3.0 +> +>Conf settings +>max_connections = 200 +>shared_buffers = 15200 +>#max_fsm_relations = 100 # min 10, fsm is free space map, ~40 bytes +>#max_fsm_pages = 10000 # min 1000, fsm is free space map, ~6 bytes +>#max_locks_per_transaction = 64 # min 10 +>#wal_buffers = 8 # min 4, typically 8KB each +> +> +> +> +>CREATE TABLE public.search_log ( +> wizard varchar(50) NOT NULL, +> sub_wizard varchar(50), +> timestamp varchar(75), +> department int4, +> gender varchar(25), +> occasion varchar(50), +> age varchar(25), +> product_type varchar(2000), +> price_range varchar(1000), +> brand varchar(2000), +> keyword varchar(1000), +> result_count int4, +> html_count int4, +> fragrance_type varchar(50), +> frag_type varchar(50), +> frag_gender char(1), +> trip_length varchar(25), +> carry_on varchar(25), +> suiter varchar(25), +> expandable varchar(25), +> wheels varchar(25), +> style varchar(1000), +> heel_type varchar(25), +> option varchar(50), +> metal varchar(255), +> gem varchar(255), +> bra_size varchar(25), +> feature1 varchar(50), +> feature2 varchar(50), +> feature3 varchar(50), +> sdate date, +> stimestamp timestamptz, +> file_name text +>) WITH OIDS; +> +>CREATE INDEX date_idx ON search_log USING btree (sdate); +>CREATE INDEX slog_wizard_idx ON search_log USING btree (wizard); + +Did you try to change theses 2 indexes into 1? +CREATE INDEX date_wizard_idx on search_log USING btree(wizard,sdate) + +How selective are these fields: + - if you ask about + wizard="Keyword", + the answer is 0.1% or 5% or 50% of rows? + - if you ask about + sdate >= '2002-12-01'::date) AND (sdate <= '2003-01-15'::date) + what is the answer? + +Consider creating table "wizards", and changing field "wizard" in table "search_log" +into integer field "wizardid". Searching by integer is faster than by varchar. + +Regards, +Tomasz Myrta + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 17:27:51 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EF88D476FAE + for ; + Wed, 22 Jan 2003 17:27:49 -0500 (EST) +Received: from johnlaptop.darkcore.net (link.clearoption.com [205.200.121.81]) + by postgresql.org (Postfix) with ESMTP id E262B47711C + for ; + Wed, 22 Jan 2003 16:44:41 -0500 (EST) +Received: by johnlaptop.darkcore.net (Postfix, from userid 501) + id 51237F1EB4; Wed, 22 Jan 2003 16:44:42 -0500 (EST) +Subject: Query plan and Inheritance. Weird behavior +From: John Lange +To: pgsql-performance@postgresql.org +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +X-Mailer: Ximian Evolution 1.0.8-3mdk +Date: 22 Jan 2003 15:44:42 -0600 +Message-Id: <1043271882.11373.158.camel@johnlaptop.darkcore.net> +Mime-Version: 1.0 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/231 +X-Sequence-Number: 878 + +I have a database that makes fairly extensive use of table Inheritance. + +Structure is one parent table and 5 child tables as follows: + +tbl_objects (parent table) + -> tbl_viewers + -> tbl_documents + -> tbl_icons + -> tbl_massemails + -> tbl_formats + +I have two questions: + +First, if I create an index on the parent table will queries to the +child tables use that index? + +Secondly, I tried to use explain to find out but I got very strange +results. It appears to read all the child tables even when you specify +only the parent table. In this case this appears to make the select do 6 +queries instead of only 1. Obviously a huge performance hit. And none of +them uses the index though the table only has 420 rows at the moment so +that might be why its just doing a scan (though IMHO 'explain' should +explain that it isn't using the available index and why). + +I can't say that I'm reading these results properly but here they are: + +"EXPLAIN select * from tbl_objects where id = 1;" + +Gives: + +NOTICE: QUERY PLAN: + +Result (cost=0.00..27.25 rows=6 width=138) + -> Append (cost=0.00..27.25 rows=6 width=138) + -> Seq Scan on tbl_objects (cost=0.00..12.24 rows=1 width=73) + -> Seq Scan on tbl_viewers tbl_objects (cost=0.00..1.07 rows=1 +width=83) + -> Seq Scan on tbl_documents tbl_objects (cost=0.00..11.56 +rows=1 width=78) + -> Seq Scan on tbl_massemails tbl_objects (cost=0.00..0.00 +rows=1 width=138) + -> Seq Scan on tbl_formats tbl_objects (cost=0.00..1.12 rows=1 +width=80) + -> Seq Scan on tbl_icons tbl_objects (cost=0.00..1.25 rows=1 +width=89) + + +Can anyone tell me if these results are making any sense and why +postgres is doing 6 reads when I only need one? + +John Lange + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 17:39:18 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9A513477335 + for ; + Wed, 22 Jan 2003 17:39:17 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id D79A1476F02 + for ; + Wed, 22 Jan 2003 17:04:03 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0MM3u5u024610; + Wed, 22 Jan 2003 17:03:56 -0500 (EST) +To: "Patrick Hatcher" +Cc: pgsql-performance@postgresql.org +Subject: Re: Slow query on OS X box +In-reply-to: +References: +Comments: In-reply-to "Patrick Hatcher" + message dated "Wed, 22 Jan 2003 10:26:17 -0800" +Date: Wed, 22 Jan 2003 17:03:55 -0500 +Message-ID: <24609.1043273035@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/232 +X-Sequence-Number: 879 + +"Patrick Hatcher" writes: +> I have a table that contains over 13 million rows. This query takes an +> extremely long time to return. I've vacuum full, analyzed, and re-indexed +> the table. Still the results are the same. Any ideas? + +> mdc_oz=# explain analyze select wizard from search_log where wizard +> ='Keyword' and sdate between '2002-12-01' and '2003-01-15'; +> QUERY PLAN +> ----------------------------------------------------------------------------------------------------------------------------- +> Seq Scan on search_log (cost=0.00..609015.34 rows=3305729 width=10) +> (actual time=99833.83..162951.25 rows=3280573 loops=1) +> Filter: ((wizard = 'Keyword'::character varying) AND (sdate > +> = '2002-12-01'::date) AND (sdate <= '2003-01-15'::date)) +> Total runtime: 174713.25 msec +> (3 rows) + +This query is selecting 3280573 rows out of your 13 million. I'd say +the machine is doing the best it can. Returning 19000 rows per second +is not all that shabby. + +Perhaps you should rethink what you're doing. Do you actually need to +return 3 million rows to the client? + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Wed Jan 22 18:41:44 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 16E5E47635D + for ; + Wed, 22 Jan 2003 18:41:43 -0500 (EST) +Received: from jester.senspire.com + (CPE00508b028d7d-CM00803785c5e0.cpe.net.cable.rogers.com + [24.103.51.175]) + by postgresql.org (Postfix) with ESMTP id 216C7476A0E + for ; + Wed, 22 Jan 2003 17:54:33 -0500 (EST) +Received: from [127.0.0.1] (localhost [127.0.0.1]) + by jester.senspire.com (8.12.6/8.12.6) with ESMTP id h0MMsKYJ059528; + Wed, 22 Jan 2003 17:54:21 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: Slow query on OS X box +From: Rod Taylor +To: Patrick Hatcher +Cc: Postgresql Performance +In-Reply-To: +References: +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-Ddx8v7ZEOD45HkgRKSwg" +Organization: +Message-Id: <1043276059.83856.180.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 22 Jan 2003 17:54:20 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/233 +X-Sequence-Number: 880 + +--=-Ddx8v7ZEOD45HkgRKSwg +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +Yup, since you still need to pull everything off the disk (the slowest +part), which is quite a bit of data. You're simply dealing with a lot +of data for a single query -- not much you can do. + +Is this a dedicated -- one client doing big selects like this? + +Knock your shared_buffers down to about 2000, bump your sort mem up to +around 32MB (128MB or so if it's a dedicated box with a vast majority of +queries like the below). + + +Okay, need to do something about the rest of the data. 13million * 2k is +a big number. Do you have a set of columns that are rarely used? If +so, toss them into a separate table and link via a unique identifier +(int4). It'll cost extra when you do hit them, but pulling out a few of +the large ones information wise would buy quite a bit. + +Now, wizard. For that particular query it would be best if entries were +made for all the values of wizard into a lookup table, and change +search_log.wizard into a reference to that entry in the lookup. Index +the lookup table well (one in the wizard primary key -- int4, and a +unique index on the 'wizard' varchar). Group by the number, join to the +lookup table for the name. + +Any other values with highly repetitive data? Might want to consider +doing the same for them. + +In search_log, index the numeric representation of 'wizard' (key from +lookup table), but don't bother indexing numbers that occur regularly. +Look up how to create a partial index. Ie. The value 'Keyword' could be +skipped as it occurs once in four tuples -- too often for an index to be +useful. + + +On Wed, 2003-01-22 at 15:49, Patrick Hatcher wrote: +> Sorry I'm being really dense today. I didn't even notice the 3.2 million +> row being returned. :( +>=20 +> To answer your question, no, all fields would not have data. The data we +> receive is from a Web log file. It's parsed and then uploaded to this +> table. +>=20 +> I guess the bigger issue is that when trying to do aggregates, grouping by +> the wizard field, it takes just as long. +>=20 +> Ex: +> mdc_oz=3D# explain analyze select wizard,count(wizard) from search_log wh= +ere +> sdate +> between '2002-12-01' and '2003-01-15' group by wizard; +> QUERY +> PLAN +> -------------------------------------------------------------------------= +---------------------------------------------------------------------- +> Aggregate (cost=3D1083300.43..1112411.55 rows=3D388148 width=3D10) (act= +ual +> time=3D229503.85..302617.75 rows=3D14 loops=3D1) +> -> Group (cost=3D1083300.43..1102707.84 rows=3D3881482 width=3D10) (= +actual +> time=3D229503.60..286014.83 rows=3D3717161 loops=3D1) +> -> Sort (cost=3D1083300.43..1093004.14 rows=3D3881482 width=3D= +10) +> (actual time=3D229503.57..248415.81 rows=3D3717161 loops=3D1) +> Sort Key: wizard +> -> Seq Scan on search_log (cost=3D0.00..575217.57 +> rows=3D3881482 width=3D10) (actual time=3D91235.76..157559.58 rows=3D3717= +161 +> loops=3D1) +> Filter: ((sdate >=3D '2002-12-01'::date) AND (sdate +> <=3D '2003-01-15'::date)) +> Total runtime: 302712.48 msec +> (7 rows) + +> On Wed, 2003-01-22 at 13:26, Patrick Hatcher wrote: +> > I have a table that contains over 13 million rows. This query takes an +> > extremely long time to return. I've vacuum full, analyzed, and +> re-indexed +> > the table. Still the results are the same. Any ideas? + +> > mdc_oz=3D# explain analyze select wizard from search_log where wizard +> > =3D'Keyword' and sdate between '2002-12-01' and '2003-01-15'; +> > QUERY PLAN +> > +> -------------------------------------------------------------------------= +---------------------------------------------------- +>=20 +> > Seq Scan on search_log (cost=3D0.00..609015.34 rows=3D3305729 width= +=3D10) +> > (actual time=3D99833.83..162951.25 rows=3D3280573 loops=3D1) +> > Filter: ((wizard =3D 'Keyword'::character varying) AND (sdate > +> > =3D '2002-12-01'::date) AND (sdate <=3D '2003-01-15'::date)) +> > Total runtime: 174713.25 msec +> > (3 rows) +> -- +> Rod Taylor +>=20 +> PGP Key: http://www.rbt.ca/rbtpub.asc +> (See attached file: signature.asc) +>=20 +>=20 +> ______________________________________________________________________ +>=20 +> ---------------------------(end of broadcast)--------------------------- +> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-Ddx8v7ZEOD45HkgRKSwg +Content-Type: application/pgp-signature; name=signature.asc +Content-Description: This is a digitally signed message part + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (FreeBSD) + +iD8DBQA+LyEa6DETLow6vwwRAozBAJ0UfoOxkmyVKfFX/mk5EQWGhzx9WgCdGPOl +BFCJvs11Hd2cujy6g5jrfBg= +=ZU4w +-----END PGP SIGNATURE----- + +--=-Ddx8v7ZEOD45HkgRKSwg-- + + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 18:45:52 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id D38D4476FA6; Wed, 22 Jan 2003 18:45:51 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 3FC3E4770F2; Wed, 22 Jan 2003 18:01:51 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0MN1r5u025072; + Wed, 22 Jan 2003 18:01:53 -0500 (EST) +To: pgsql-hackers@postgreSQL.org, pgsql-performance@postgreSQL.org +Subject: Proposal: relaxing link between explicit JOINs and execution order +Date: Wed, 22 Jan 2003 18:01:53 -0500 +Message-ID: <25071.1043276513@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/849 +X-Sequence-Number: 34459 + +There's been some recent discussion about the fact that Postgres treats +explicit JOIN syntax as constraining the actual join plan, cf +http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/explicit-joins.html + +This behavior was originally in there simply because of lack of time to +consider alternatives. I now realize that it wouldn't be hard to get +the planner to do better --- basically, preprocess_jointree just has to +be willing to fold JoinExpr-under-JoinExpr into a FromExpr when the +joins are inner joins. + +But in the meantime, some folks have found the present behavior to be +a feature rather than a bug, since it lets them control planning time +on many-table queries. If we are going to change it, I think we need +some way to accommodate both camps. + +What I've been toying with is inventing a GUC variable or two. I am +thinking of defining a variable that sets the maximum size of a FromExpr +that preprocess_jointree is allowed to create by folding JoinExprs. +If this were set to 2, the behavior would be the same as before: no +collapsing of JoinExprs can occur. If it were set to a large number, +inner JOIN syntax would never affect the planner at all. In practice +it'd be smart to leave it at some value less than GEQO_THRESHOLD, so +that folding a large number of JOINs wouldn't leave you with a query +that takes a long time to plan or produces unpredictable plans. + +There is already a need for a GUC variable to control the existing +behavior of preprocess_jointree: right now, it arbitrarily uses +GEQO_THRESHOLD/2 as the limit for the size of a FromExpr that can be +made by collapsing FromExprs together. This ought to be a separately +settable parameter, I think. + +Comments? In particular, can anyone think of pithy names for these +variables? The best I'd been able to come up with is MAX_JOIN_COLLAPSE +and MAX_FROM_COLLAPSE, but neither of these exactly sing... + + regards, tom lane + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 18:51:38 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id A1726476FF9; Wed, 22 Jan 2003 18:51:37 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id A5D6D477161; Wed, 22 Jan 2003 18:14:31 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0MNEU5u025183; + Wed, 22 Jan 2003 18:14:32 -0500 (EST) +To: Steve Crawford +Cc: pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +Subject: Re: Terrible performance on wide selects +In-reply-to: <20030122224814.ECF47103E6@polaris.pinpointresearch.com> +References: <20030117193726.1CFCB103E5@polaris.pinpointresearch.com> + <20030122212901.EDF00103E6@polaris.pinpointresearch.com> + <24808.1043274411@sss.pgh.pa.us> + <20030122224814.ECF47103E6@polaris.pinpointresearch.com> +Comments: In-reply-to Steve Crawford + message dated "Wed, 22 Jan 2003 14:48:15 -0800" +Date: Wed, 22 Jan 2003 18:14:30 -0500 +Message-ID: <25182.1043277270@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/850 +X-Sequence-Number: 34460 + +Steve Crawford sent me some profiling results for queries involving wide +tuples (hundreds of columns). + +> Done, results attached. nocachegetattr seems to be the likely suspect. + +Yipes, you can say that again. + + % cumulative self self total + time seconds seconds calls ms/call ms/call name + 93.38 26.81 26.81 885688 0.03 0.03 nocachegetattr + + 0.00 0.00 1/885688 heapgettup [159] + 0.00 0.00 1/885688 CatalogCacheComputeTupleHashValue [248] + 0.00 0.00 5/885688 SearchCatCache [22] + 13.40 0.00 442840/885688 ExecEvalVar [20] + 13.40 0.00 442841/885688 printtup [12] +[11] 93.4 26.81 0.00 885688 nocachegetattr [11] + + +Half of the calls are coming from printtup(), which seems relatively easy +to fix. + + /* + * send the attributes of this tuple + */ + for (i = 0; i < natts; ++i) + { + ... + origattr = heap_getattr(tuple, i + 1, typeinfo, &isnull); + ... + } + +The trouble here is that in the presence of variable-width fields, +heap_getattr requires a linear scan over the tuple --- and so the total +time spent in it is O(N^2) in the number of fields. + +What we could do is reinstitute heap_deformtuple() as the inverse of +heap_formtuple() --- but make it extract Datums for all the columns in +a single pass over the tuple. This would reduce the time in printtup() +from O(N^2) to O(N), which would pretty much wipe out that part of the +problem. + +The other half of the calls are coming from ExecEvalVar, which is a +harder problem to solve, since those calls are scattered all over the +place. It's harder to see how to get them to share work. Any ideas +out there? + + regards, tom lane + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:26:02 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id C3BCD476792; Wed, 22 Jan 2003 19:26:01 -0500 (EST) +Received: from voyager.corporate.connx.com (unknown [209.20.248.131]) + by postgresql.org (Postfix) with ESMTP + id 9F4264764FF; Wed, 22 Jan 2003 18:56:52 -0500 (EST) +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="us-ascii" +Content-Transfer-Encoding: quoted-printable +Subject: Re: Terrible performance on wide selects +X-MimeOLE: Produced By Microsoft Exchange V6.0.6249.0 +Date: Wed, 22 Jan 2003 15:56:55 -0800 +Message-ID: + +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [HACKERS] Terrible performance on wide selects +Thread-Index: AcLCcUCKv2Dzdt+2S5KSGmsm2QIFGQAADl6w +From: "Dann Corbit" +To: "Tom Lane" , + "Steve Crawford" +Cc: , + +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/851 +X-Sequence-Number: 34461 + +> -----Original Message----- +> From: Tom Lane [mailto:tgl@sss.pgh.pa.us]=20 +> Sent: Wednesday, January 22, 2003 3:15 PM +> To: Steve Crawford +> Cc: pgsql-performance@postgreSQL.org; pgsql-hackers@postgreSQL.org +> Subject: Re: [HACKERS] Terrible performance on wide selects=20 +>=20 +>=20 +> Steve Crawford sent me some profiling results for queries=20 +> involving wide tuples (hundreds of columns). +>=20 +> > Done, results attached. nocachegetattr seems to be the=20 +> likely suspect. +>=20 +> Yipes, you can say that again. +>=20 +> % cumulative self self total=20=20=20=20=20=20=20= +=20=20=20=20 +> time seconds seconds calls ms/call ms/call name=20=20=20=20 +> 93.38 26.81 26.81 885688 0.03 0.03 nocachegetattr +>=20 +> 0.00 0.00 1/885688 heapgettup [159] +> 0.00 0.00 1/885688=20=20=20=20=20=20 +> CatalogCacheComputeTupleHashValue [248] +> 0.00 0.00 5/885688 SearchCatCache [22] +> 13.40 0.00 442840/885688 ExecEvalVar [20] +> 13.40 0.00 442841/885688 printtup [12] +> [11] 93.4 26.81 0.00 885688 nocachegetattr [11] +>=20 +>=20 +> Half of the calls are coming from printtup(), which seems=20 +> relatively easy to fix. +>=20 +> /* +> * send the attributes of this tuple +> */ +> for (i =3D 0; i < natts; ++i) +> { +> ... +> origattr =3D heap_getattr(tuple, i + 1, typeinfo,=20 +> &isnull); +> ... +> } +>=20 +> The trouble here is that in the presence of variable-width=20 +> fields, heap_getattr requires a linear scan over the tuple=20 +> --- and so the total time spent in it is O(N^2) in the number=20 +> of fields. +>=20 +> What we could do is reinstitute heap_deformtuple() as the inverse of +> heap_formtuple() --- but make it extract Datums for all the=20 +> columns in a single pass over the tuple. This would reduce=20 +> the time in printtup() from O(N^2) to O(N), which would=20 +> pretty much wipe out that part of the problem. +>=20 +> The other half of the calls are coming from ExecEvalVar,=20 +> which is a harder problem to solve, since those calls are=20 +> scattered all over the place. It's harder to see how to get=20 +> them to share work. Any ideas out there? + +Is it possible that the needed information could be retrieved by +querying the system metadata to collect the column information? + +Once the required tuple attributes are described, it could form a +binding list that allocates a buffer of sufficient size with pointers to +the required column start points. + +Maybe I don't really understand the problem, but it seems simple enough +to do it once for the whole query. + +If this is utter stupidity, please disregard and have a hearty laugh at +my expense. +;-) + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:27:14 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 2E220476F8B; Wed, 22 Jan 2003 19:27:14 -0500 (EST) +Received: from perrin.int.nxad.com (internal.ext.nxad.com [66.250.180.251]) + by postgresql.org (Postfix) with ESMTP + id BC38947707B; Wed, 22 Jan 2003 18:59:47 -0500 (EST) +Received: by perrin.int.nxad.com (Postfix, from userid 1001) + id A685E2105F; Wed, 22 Jan 2003 15:59:31 -0800 (PST) +Date: Wed, 22 Jan 2003 15:59:31 -0800 +From: Sean Chittenden +To: Tom Lane +Cc: pgsql-hackers@postgreSQL.org, pgsql-performance@postgreSQL.org +Subject: Re: [PERFORM] Proposal: relaxing link between explicit JOINs and + execution order +Message-ID: <20030122235931.GE12075@perrin.int.nxad.com> +References: <25071.1043276513@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <25071.1043276513@sss.pgh.pa.us> +User-Agent: Mutt/1.4i +X-PGP-Key: finger seanc@FreeBSD.org +X-PGP-Fingerprint: 6CEB 1B06 BFD3 70F6 95BE 7E4D 8E85 2E0A 5F5B 3ECB +X-Web-Homepage: http://sean.chittenden.org/ +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/852 +X-Sequence-Number: 34462 + +> There's been some recent discussion about the fact that Postgres +> treats explicit JOIN syntax as constraining the actual join plan, cf +> http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/explicit-joins.html +> +> This behavior was originally in there simply because of lack of time +> to consider alternatives. I now realize that it wouldn't be hard to +> get the planner to do better --- basically, preprocess_jointree just +> has to be willing to fold JoinExpr-under-JoinExpr into a FromExpr +> when the joins are inner joins. +> +> But in the meantime, some folks have found the present behavior to be +> a feature rather than a bug, since it lets them control planning time +> on many-table queries. If we are going to change it, I think we need +> some way to accommodate both camps. +[snip] +> Comments? In particular, can anyone think of pithy names for these +> variables? The best I'd been able to come up with is +> MAX_JOIN_COLLAPSE and MAX_FROM_COLLAPSE, but neither of these +> exactly sing... + +How about something that's runtime tunable via a SET/SHOW config var? +There are some queries that I have that I haven't spent any time +tuning and would love to have the planner spend its CPU thinking about +it instead of mine. Setting it to 2 by default, then on my tuned +queries, setting to something obscenely high so the planner won't muck +with what I know is fastest (or so I think at least). + +I know this is a can of worms, but what about piggy backing on an +Oracle notation and having an inline way of setting this inside of a +comment? + +SELECT /* +planner:collapse_tables=12 */ .... ? + ^^^^^^^ ^^^^^^^^^^^^^^^ ^^^ + system variable value + +::shrug:: In brainstorm mode. Anyway, a few names: + +auto_order_join +auto_order_join_max +auto_reorder_table_limit +auto_collapse_join +auto_collapse_num_join +auto_join_threshold + +When I'm thinking about what this variable will do for me as a DBA, I +think it will make the plan more intelligent by reordering the joins. +My $0.02. -sc + +-- +Sean Chittenden + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:28:13 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 3F186476FBA; Wed, 22 Jan 2003 19:28:12 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 3125947610E; Wed, 22 Jan 2003 19:04:03 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0N0435u025522; + Wed, 22 Jan 2003 19:04:03 -0500 (EST) +To: "Dann Corbit" +Cc: "Steve Crawford" , + pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +Subject: Re: Terrible performance on wide selects +In-reply-to: + +References: + +Comments: In-reply-to "Dann Corbit" + message dated "Wed, 22 Jan 2003 15:56:55 -0800" +Date: Wed, 22 Jan 2003 19:04:02 -0500 +Message-ID: <25521.1043280242@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/853 +X-Sequence-Number: 34463 + +"Dann Corbit" writes: +> Maybe I don't really understand the problem, but it seems simple enough +> to do it once for the whole query. + +We already do cache column offsets when they are fixed. The code that's +the problem executes when there's a variable-width column in the table +--- which means that all columns to its right are not at fixed offsets, +and have to be scanned for separately in each tuple, AFAICS. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Wed Jan 22 19:30:34 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 2696E477117; Wed, 22 Jan 2003 19:30:30 -0500 (EST) +Received: from fddlnint05.fds.com (fddlnint05.fds.com [208.15.91.52]) + by postgresql.org (Postfix) with ESMTP + id 829BE47630A; Wed, 22 Jan 2003 19:10:11 -0500 (EST) +Subject: Re: Slow query on OS X box +To: "Rod Taylor +Cc: Postgresql Performance , + pgsql-performance-owner@postgresql.org +X-Mailer: Lotus Notes Release 5.0.8 June 18, 2001 +Message-ID: +From: "Patrick Hatcher" +Date: Wed, 22 Jan 2003 16:05:39 -0800 +X-MIMETrack: Serialize by Router on FDDLNINT05/FSG/SVR/FDD(Release 5.0.4 |June + 8, 2000) at 01/22/2003 07:07:12 PM +MIME-Version: 1.0 +Content-type: multipart/mixed; + Boundary="0__=88256CB7000066218f9e8a93df938690918c88256CB700006621" +Content-Disposition: inline +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/241 +X-Sequence-Number: 888 + +--0__=88256CB7000066218f9e8a93df938690918c88256CB700006621 +Content-type: text/plain; charset=us-ascii + + +Thanks everyone. I'll give your suggestions a try and report back. + +Patrick Hatcher +Macys.Com +Legacy Integration Developer +415-422-1610 office +HatcherPT - AIM + + + + + + Rod Taylor + Sent by: To: Patrick Hatcher + pgsql-performance-owner@post cc: Postgresql Performance + gresql.org Subject: Re: [PERFORM] Slow query on OS X box + + + 01/22/2003 02:54 PM + + + + + + +Yup, since you still need to pull everything off the disk (the slowest +part), which is quite a bit of data. You're simply dealing with a lot +of data for a single query -- not much you can do. + +Is this a dedicated -- one client doing big selects like this? + +Knock your shared_buffers down to about 2000, bump your sort mem up to +around 32MB (128MB or so if it's a dedicated box with a vast majority of +queries like the below). + + +Okay, need to do something about the rest of the data. 13million * 2k is +a big number. Do you have a set of columns that are rarely used? If +so, toss them into a separate table and link via a unique identifier +(int4). It'll cost extra when you do hit them, but pulling out a few of +the large ones information wise would buy quite a bit. + +Now, wizard. For that particular query it would be best if entries were +made for all the values of wizard into a lookup table, and change +search_log.wizard into a reference to that entry in the lookup. Index +the lookup table well (one in the wizard primary key -- int4, and a +unique index on the 'wizard' varchar). Group by the number, join to the +lookup table for the name. + +Any other values with highly repetitive data? Might want to consider +doing the same for them. + +In search_log, index the numeric representation of 'wizard' (key from +lookup table), but don't bother indexing numbers that occur regularly. +Look up how to create a partial index. Ie. The value 'Keyword' could be +skipped as it occurs once in four tuples -- too often for an index to be +useful. + + +On Wed, 2003-01-22 at 15:49, Patrick Hatcher wrote: +> Sorry I'm being really dense today. I didn't even notice the 3.2 million +> row being returned. :( +> +> To answer your question, no, all fields would not have data. The data we +> receive is from a Web log file. It's parsed and then uploaded to this +> table. +> +> I guess the bigger issue is that when trying to do aggregates, grouping +by +> the wizard field, it takes just as long. +> +> Ex: +> mdc_oz=# explain analyze select wizard,count(wizard) from search_log +where +> sdate +> between '2002-12-01' and '2003-01-15' group by wizard; +> QUERY +> PLAN +> +----------------------------------------------------------------------------------------------------------------------------------------------- + +> Aggregate (cost=1083300.43..1112411.55 rows=388148 width=10) (actual +> time=229503.85..302617.75 rows=14 loops=1) +> -> Group (cost=1083300.43..1102707.84 rows=3881482 width=10) (actual +> time=229503.60..286014.83 rows=3717161 loops=1) +> -> Sort (cost=1083300.43..1093004.14 rows=3881482 width=10) +> (actual time=229503.57..248415.81 rows=3717161 loops=1) +> Sort Key: wizard +> -> Seq Scan on search_log (cost=0.00..575217.57 +> rows=3881482 width=10) (actual time=91235.76..157559.58 rows=3717161 +> loops=1) +> Filter: ((sdate >= '2002-12-01'::date) AND (sdate +> <= '2003-01-15'::date)) +> Total runtime: 302712.48 msec +> (7 rows) + +> On Wed, 2003-01-22 at 13:26, Patrick Hatcher wrote: +> > I have a table that contains over 13 million rows. This query takes an +> > extremely long time to return. I've vacuum full, analyzed, and +> re-indexed +> > the table. Still the results are the same. Any ideas? + +> > mdc_oz=# explain analyze select wizard from search_log where wizard +> > ='Keyword' and sdate between '2002-12-01' and '2003-01-15'; +> > QUERY PLAN +> > +> +----------------------------------------------------------------------------------------------------------------------------- + +> +> > Seq Scan on search_log (cost=0.00..609015.34 rows=3305729 width=10) +> > (actual time=99833.83..162951.25 rows=3280573 loops=1) +> > Filter: ((wizard = 'Keyword'::character varying) AND (sdate > +> > = '2002-12-01'::date) AND (sdate <= '2003-01-15'::date)) +> > Total runtime: 174713.25 msec +> > (3 rows) +> -- +> Rod Taylor +> +> PGP Key: http://www.rbt.ca/rbtpub.asc +> (See attached file: signature.asc) +> +> +> ______________________________________________________________________ +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org +-- +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc +(See attached file: signature.asc) + + +--0__=88256CB7000066218f9e8a93df938690918c88256CB700006621 +Content-type: application/octet-stream; + name="signature.asc" +Content-Disposition: attachment; filename="signature.asc" +Content-transfer-encoding: base64 + +LS0tLS1CRUdJTiBQR1AgU0lHTkFUVVJFLS0tLS0NClZlcnNpb246IEdudVBH +IHYxLjIuMSAoRnJlZUJTRCkNCg0KaUQ4REJRQStMeUVhNkRFVExvdzZ2d3dS +QW96QkFKMFVmb094a215VktmRlgvbWs1RVFXR2h6eDlXZ0NkR1BPbA0KQkZD +SnZzMTFIZDJjdWp5Nmc1anJmQmc9DQo9WlU0dw0KLS0tLS1FTkQgUEdQIFNJ +R05BVFVSRS0tLS0tDQo= + +--0__=88256CB7000066218f9e8a93df938690918c88256CB700006621-- + + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:28:24 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id CA74F47610E; Wed, 22 Jan 2003 19:28:23 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 3174F476932; Wed, 22 Jan 2003 19:06:11 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0N06C5u025542; + Wed, 22 Jan 2003 19:06:12 -0500 (EST) +To: Sean Chittenden +Cc: pgsql-hackers@postgreSQL.org, pgsql-performance@postgreSQL.org +Subject: Re: [PERFORM] Proposal: relaxing link between explicit JOINs and + execution order +In-reply-to: <20030122235931.GE12075@perrin.int.nxad.com> +References: <25071.1043276513@sss.pgh.pa.us> + <20030122235931.GE12075@perrin.int.nxad.com> +Comments: In-reply-to Sean Chittenden + message dated "Wed, 22 Jan 2003 15:59:31 -0800" +Date: Wed, 22 Jan 2003 19:06:12 -0500 +Message-ID: <25541.1043280372@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/854 +X-Sequence-Number: 34464 + +Sean Chittenden writes: +> How about something that's runtime tunable via a SET/SHOW config var? + +Er, that's what I was talking about. + +> I know this is a can of worms, but what about piggy backing on an +> Oracle notation and having an inline way of setting this inside of a +> comment? + +I don't want to go there ... + + regards, tom lane + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:28:31 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id AF5574763AE; Wed, 22 Jan 2003 19:28:26 -0500 (EST) +Received: from voyager.corporate.connx.com (unknown [209.20.248.131]) + by postgresql.org (Postfix) with ESMTP + id 30BCC476225; Wed, 22 Jan 2003 19:06:24 -0500 (EST) +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="us-ascii" +Content-Transfer-Encoding: quoted-printable +Subject: Re: Terrible performance on wide selects +X-MimeOLE: Produced By Microsoft Exchange V6.0.6249.0 +Date: Wed, 22 Jan 2003 16:06:26 -0800 +Message-ID: + +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [HACKERS] Terrible performance on wide selects +Thread-Index: AcLCcvHqCIiFc580TV+dnOY8b5QwgQAABbnw +From: "Dann Corbit" +To: "Tom Lane" +Cc: "Steve Crawford" , + , +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/855 +X-Sequence-Number: 34465 + +> -----Original Message----- +> From: Tom Lane [mailto:tgl@sss.pgh.pa.us]=20 +> Sent: Wednesday, January 22, 2003 4:04 PM +> To: Dann Corbit +> Cc: Steve Crawford; pgsql-performance@postgreSQL.org;=20 +> pgsql-hackers@postgreSQL.org +> Subject: Re: [HACKERS] Terrible performance on wide selects=20 +>=20 +>=20 +> "Dann Corbit" writes: +> > Maybe I don't really understand the problem, but it seems simple=20 +> > enough to do it once for the whole query. +>=20 +> We already do cache column offsets when they are fixed. The=20 +> code that's the problem executes when there's a=20 +> variable-width column in the table +> --- which means that all columns to its right are not at=20 +> fixed offsets, and have to be scanned for separately in each=20 +> tuple, AFAICS. + +Why not waste a bit of memory and make the row buffer the maximum +possible length? +E.g. for varchar(2000) allocate 2000 characters + size element and point +to the start of that thing. + +If we have 64K rows, even at that it is a pittance. If someone designs +10,000 row tables, then it will allocate an annoyingly large block of +memory, but bad designs are always going to cause a fuss. + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:35:36 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 0FD50476E52; Wed, 22 Jan 2003 19:35:30 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP + id D5F5F476026; Wed, 22 Jan 2003 19:17:09 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2322649; Wed, 22 Jan 2003 16:17:16 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Tom Lane , pgsql-hackers@postgreSQL.org, + pgsql-performance@postgreSQL.org +Subject: Re: [PERFORM] Proposal: relaxing link between explicit JOINs and + execution order +Date: Wed, 22 Jan 2003 16:17:41 -0800 +X-Mailer: KMail [version 1.4] +References: <25071.1043276513@sss.pgh.pa.us> +In-Reply-To: <25071.1043276513@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301221617.41680.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/856 +X-Sequence-Number: 34466 + +Tom, + +I am very strongly in favor of this idea. I would personally prefer it if= +=20 +the Join collapsing parmeter could be set at query time through a SET=20 +statement, but will of course defer to the difficulty level in doing so. + +> Comments? In particular, can anyone think of pithy names for these +> variables? The best I'd been able to come up with is MAX_JOIN_COLLAPSE +> and MAX_FROM_COLLAPSE, but neither of these exactly sing... + +How about: +EXPLICIT_JOIN_MINIMUM +and +FROM_COLLAPSE_LIMIT + +Just to make the two params not sound so identical? + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:35:50 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 43A17477178; Wed, 22 Jan 2003 19:35:49 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 71418476680; Wed, 22 Jan 2003 19:18:07 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0N0I75u025623; + Wed, 22 Jan 2003 19:18:07 -0500 (EST) +To: "Dann Corbit" +Cc: "Steve Crawford" , + pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +Subject: Re: Terrible performance on wide selects +In-reply-to: + +References: + +Comments: In-reply-to "Dann Corbit" + message dated "Wed, 22 Jan 2003 16:06:26 -0800" +Date: Wed, 22 Jan 2003 19:18:07 -0500 +Message-ID: <25622.1043281087@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/857 +X-Sequence-Number: 34467 + +"Dann Corbit" writes: +> Why not waste a bit of memory and make the row buffer the maximum +> possible length? +> E.g. for varchar(2000) allocate 2000 characters + size element and point +> to the start of that thing. + +Surely you're not proposing that we store data on disk that way. + +The real issue here is avoiding overhead while extracting columns out of +a stored tuple. We could perhaps use a different, less space-efficient +format for temporary tuples in memory than we do on disk, but I don't +think that will help a lot. The nature of O(N^2) bottlenecks is you +have to kill them all --- for example, if we fix printtup and don't do +anything with ExecEvalVar, we can't do more than double the speed of +Steve's example, so it'll still be slow. So we must have a solution for +the case where we are disassembling a stored tuple, anyway. + +I have been sitting here toying with a related idea, which is to use the +heap_deformtuple code I suggested before to form an array of pointers to +Datums in a specific tuple (we could probably use the TupleTableSlot +mechanisms to manage the memory for these). Then subsequent accesses to +individual columns would just need an array-index operation, not a +nocachegetattr call. The trick with that would be that if only a few +columns are needed out of a row, it might be a net loss to compute the +Datum values for all columns. How could we avoid slowing that case down +while making the wide-tuple case faster? + + regards, tom lane + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:37:29 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 4BDCA4771FE; Wed, 22 Jan 2003 19:37:28 -0500 (EST) +Received: from voyager.corporate.connx.com (unknown [209.20.248.131]) + by postgresql.org (Postfix) with ESMTP + id 11828476DC3; Wed, 22 Jan 2003 19:21:16 -0500 (EST) +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="us-ascii" +Content-Transfer-Encoding: quoted-printable +Subject: Re: Terrible performance on wide selects +X-MimeOLE: Produced By Microsoft Exchange V6.0.6249.0 +Date: Wed, 22 Jan 2003 16:21:18 -0800 +Message-ID: + +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [HACKERS] Terrible performance on wide selects +Thread-Index: AcLCdOk7m8zPEW2kS6KRnU56l4FJ/AAACQgA +From: "Dann Corbit" +To: "Tom Lane" +Cc: "Steve Crawford" , + , +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/858 +X-Sequence-Number: 34468 + +> -----Original Message----- +> From: Tom Lane [mailto:tgl@sss.pgh.pa.us]=20 +> Sent: Wednesday, January 22, 2003 4:18 PM +> To: Dann Corbit +> Cc: Steve Crawford; pgsql-performance@postgreSQL.org;=20 +> pgsql-hackers@postgreSQL.org +> Subject: Re: [HACKERS] Terrible performance on wide selects=20 +>=20 +>=20 +> "Dann Corbit" writes: +> > Why not waste a bit of memory and make the row buffer the maximum=20 +> > possible length? E.g. for varchar(2000) allocate 2000 characters +=20 +> > size element and point to the start of that thing. +>=20 +> Surely you're not proposing that we store data on disk that way. +>=20 +> The real issue here is avoiding overhead while extracting=20 +> columns out of a stored tuple. We could perhaps use a=20 +> different, less space-efficient format for temporary tuples=20 +> in memory than we do on disk, but I don't think that will=20 +> help a lot. The nature of O(N^2) bottlenecks is you have to=20 +> kill them all --- for example, if we fix printtup and don't=20 +> do anything with ExecEvalVar, we can't do more than double=20 +> the speed of Steve's example, so it'll still be slow. So we=20 +> must have a solution for the case where we are disassembling=20 +> a stored tuple, anyway. +>=20 +> I have been sitting here toying with a related idea, which is=20 +> to use the heap_deformtuple code I suggested before to form=20 +> an array of pointers to Datums in a specific tuple (we could=20 +> probably use the TupleTableSlot mechanisms to manage the=20 +> memory for these). Then subsequent accesses to individual=20 +> columns would just need an array-index operation, not a=20 +> nocachegetattr call. The trick with that would be that if=20 +> only a few columns are needed out of a row, it might be a net=20 +> loss to compute the Datum values for all columns. How could=20 +> we avoid slowing that case down while making the wide-tuple=20 +> case faster? + +For the disk case, why not have the start of the record contain an array +of offsets to the start of the data for each column? It would only be +necessary to have a list for variable fields. + +So (for instance) if you have 12 variable fields, you would store 12 +integers at the start of the record. + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:38:10 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id C1882476E89; Wed, 22 Jan 2003 19:38:08 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id E3970476F45; Wed, 22 Jan 2003 19:21:43 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0N0LO5u025651; + Wed, 22 Jan 2003 19:21:24 -0500 (EST) +To: josh@agliodbs.com +Cc: pgsql-hackers@postgreSQL.org, pgsql-performance@postgreSQL.org +Subject: Re: [PERFORM] Proposal: relaxing link between explicit JOINs and + execution order +In-reply-to: <200301221617.41680.josh@agliodbs.com> +References: <25071.1043276513@sss.pgh.pa.us> + <200301221617.41680.josh@agliodbs.com> +Comments: In-reply-to Josh Berkus + message dated "Wed, 22 Jan 2003 16:17:41 -0800" +Date: Wed, 22 Jan 2003 19:21:24 -0500 +Message-ID: <25650.1043281284@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/859 +X-Sequence-Number: 34469 + +Josh Berkus writes: +> I am very strongly in favor of this idea. I would personally prefer it if +> the Join collapsing parmeter could be set at query time through a SET +> statement, but will of course defer to the difficulty level in doing so. + +I guess I failed to make it clear that that's what I meant. GUC +variables are those things that you can set via SET, or in the +postgresql.conf file, etc. These values would be just as manipulable +as, say, ENABLE_SEQSCAN. + +> How about: +> EXPLICIT_JOIN_MINIMUM +> and +> FROM_COLLAPSE_LIMIT + +> Just to make the two params not sound so identical? + +Hmm. The two parameters would have closely related functions, so I'd +sort of think that the names *should* be pretty similar. + + regards, tom lane + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:38:29 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 0F135477253; Wed, 22 Jan 2003 19:38:28 -0500 (EST) +Received: from voyager.corporate.connx.com (unknown [209.20.248.131]) + by postgresql.org (Postfix) with ESMTP + id 0D9A9476EAB; Wed, 22 Jan 2003 19:22:49 -0500 (EST) +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="us-ascii" +Content-Transfer-Encoding: quoted-printable +Subject: Re: Terrible performance on wide selects +X-MimeOLE: Produced By Microsoft Exchange V6.0.6249.0 +Date: Wed, 22 Jan 2003 16:22:51 -0800 +Message-ID: + +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [HACKERS] Terrible performance on wide selects +Thread-Index: AcLCdOk7m8zPEW2kS6KRnU56l4FJ/AAACQgAAAAXHfA= +From: "Dann Corbit" +To: "Dann Corbit" , "Tom Lane" +Cc: "Steve Crawford" , + , +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/860 +X-Sequence-Number: 34470 + +[snip] +> So (for instance) if you have 12 variable fields, you would=20 +> store 12 integers at the start of the record. + +Additionally, you could implicitly size the integers from the properties +of the column. A varchar(255) would only need an unsigned char to store +the offset, but a varchar(80000) would require an unsigned int. + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 19:49:21 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 92EAE476FB1; Wed, 22 Jan 2003 19:49:19 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id EF2054770BE; Wed, 22 Jan 2003 19:30:05 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0N0U45u025726; + Wed, 22 Jan 2003 19:30:04 -0500 (EST) +To: "Dann Corbit" +Cc: "Steve Crawford" , + pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +Subject: Re: Terrible performance on wide selects +In-reply-to: + +References: + +Comments: In-reply-to "Dann Corbit" + message dated "Wed, 22 Jan 2003 16:21:18 -0800" +Date: Wed, 22 Jan 2003 19:30:04 -0500 +Message-ID: <25725.1043281804@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/861 +X-Sequence-Number: 34471 + +"Dann Corbit" writes: +> For the disk case, why not have the start of the record contain an array +> of offsets to the start of the data for each column? It would only be +> necessary to have a list for variable fields. + +No, you'd need an entry for *every* column (or at least, every one to +the right of the first variable-width column or NULL). That's a lot of +overhead, especially in comparison to datatypes like bool or int4 ... + + regards, tom lane + +From pgsql-hackers-owner@postgresql.org Wed Jan 22 20:14:49 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 35404475D99; Wed, 22 Jan 2003 20:14:47 -0500 (EST) +Received: from voyager.corporate.connx.com (unknown [209.20.248.131]) + by postgresql.org (Postfix) with ESMTP + id AFBB64772C7; Wed, 22 Jan 2003 19:39:54 -0500 (EST) +content-class: urn:content-classes:message +MIME-Version: 1.0 +Content-Type: text/plain; + charset="us-ascii" +Content-Transfer-Encoding: quoted-printable +Subject: Re: Terrible performance on wide selects +X-MimeOLE: Produced By Microsoft Exchange V6.0.6249.0 +Date: Wed, 22 Jan 2003 16:39:57 -0800 +Message-ID: + +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: [HACKERS] Terrible performance on wide selects +Thread-Index: AcLCdOk7m8zPEW2kS6KRnU56l4FJ/AAACQgAAACuH1A= +From: "Dann Corbit" +To: "Dann Corbit" , "Tom Lane" +Cc: "Steve Crawford" , + , +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/862 +X-Sequence-Number: 34472 + +[snip] +> For the disk case, why not have the start of the record=20 +> contain an array of offsets to the start of the data for each=20 +> column? It would only be necessary to have a list for=20 +> variable fields. +>=20 +> So (for instance) if you have 12 variable fields, you would=20 +> store 12 integers at the start of the record. + +You have to store this information anyway (for variable length objects). +By storing it at the front of the record you would lose nothing (except +the logical coupling of an object with its length). But I would think +that it would not consume any additional storage. + +From pgsql-performance-owner@postgresql.org Wed Jan 22 20:29:40 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0E14D47620C + for ; + Wed, 22 Jan 2003 20:29:40 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id CAB6A4768BF + for ; + Wed, 22 Jan 2003 19:59:10 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id B3591D616; Wed, 22 Jan 2003 16:59:13 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id A90665C03; Wed, 22 Jan 2003 16:59:13 -0800 (PST) +Date: Wed, 22 Jan 2003 16:59:13 -0800 (PST) +From: Stephan Szabo +To: John Lange +Cc: +Subject: Re: Query plan and Inheritance. Weird behavior +In-Reply-To: <1043271882.11373.158.camel@johnlaptop.darkcore.net> +Message-ID: <20030122165418.Q4204-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/249 +X-Sequence-Number: 896 + + +On 22 Jan 2003, John Lange wrote: + +> I have a database that makes fairly extensive use of table Inheritance. +> +> Structure is one parent table and 5 child tables as follows: +> +> tbl_objects (parent table) +> -> tbl_viewers +> -> tbl_documents +> -> tbl_icons +> -> tbl_massemails +> -> tbl_formats +> +> I have two questions: +> +> First, if I create an index on the parent table will queries to the +> child tables use that index? + +AFAIK no since indices aren't inherited. + +> Secondly, I tried to use explain to find out but I got very strange +> results. It appears to read all the child tables even when you specify +> only the parent table. In this case this appears to make the select do 6 +> queries instead of only 1. Obviously a huge performance hit. And none of +> them uses the index though the table only has 420 rows at the moment so +> that might be why its just doing a scan (though IMHO 'explain' should +> explain that it isn't using the available index and why). + +It seems reasonable to me since given the # of rows and the estimated +row width the table is probably only like 5 or 6 pages. Reading the index +is unlikely to make life much better given an index read, seek in heap +file, read heap file page. + +> I can't say that I'm reading these results properly but here they are: +> +> "EXPLAIN select * from tbl_objects where id = 1;" + +This gets any rows in tbl_objects that have id=1 and any rows in any +subtables that have id=1. Is that the intended effect? + + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 21:11:57 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 41AA8475D99 + for ; + Wed, 22 Jan 2003 21:11:56 -0500 (EST) +Received: from johnlaptop.darkcore.net (h24-82-231-93.wp.shawcable.net + [24.82.231.93]) by postgresql.org (Postfix) with ESMTP id EE3A3475AE4 + for ; + Wed, 22 Jan 2003 21:11:54 -0500 (EST) +Received: by johnlaptop.darkcore.net (Postfix, from userid 501) + id 1DA89F1EB4; Wed, 22 Jan 2003 21:11:57 -0500 (EST) +Subject: Re: Query plan and Inheritance. Weird behavior +From: John Lange +To: Stephan Szabo +Cc: pgsql-performance@postgresql.org +In-Reply-To: <20030122165418.Q4204-100000@megazone23.bigpanda.com> +References: <20030122165418.Q4204-100000@megazone23.bigpanda.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +X-Mailer: Ximian Evolution 1.0.8-3mdk +Date: 22 Jan 2003 20:11:56 -0600 +Message-Id: <1043287916.2142.76.camel@johnlaptop.darkcore.net> +Mime-Version: 1.0 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/250 +X-Sequence-Number: 897 + +> This gets any rows in tbl_objects that have id=1 and any rows in any +> subtables that have id=1. Is that the intended effect? + +It is the intended result, but not the expected implementation. + +Doing more investigation I think I figured out why Postgres does what it +does. + +Creating child tables by inheriting from another table doesn't really do +what I consider to be 'true' inheritance, at least not in the way I +expected as a programmer. + +Postgres seems to create "child" tables by first fully duplicating the +parent table and then adding the new columns to it. It then links the +tables internally some how so that a query on a parent table also +queries the child tables. + +IHO this seems like inheritance by 'brute force' and a parent table that +has many children will cause a significant performance hit. + +When I say "as a programmer" what I mean is I had expected it to be done +entirely the opposite way. In other words, child tables would simply be +linked internally to the parent table and a new table created which only +contains the new columns. + +In this way the parent table would not need to know, nor would it care +about child tables in any way (just like inheritance in most programming +languages). If done this way a select on a parent table would only +require the retrieval of a single row and a select on a child table +would only require the retrieval of two rows (one in the child table and +one in the parent table). + +I don't pretend to know the intricacies of Postgres performance but this +is the way I'm interpreting the data from the explains. + +At this time, now that I (think I) understand how the inheritance is +implemented I'm considering abandoning it in Postgres and solving the +issue entirely pragmatically. + +I hoping someone on the list will tell me where I'm going wrong here or +what wrong assumptions I'm making. + +John Lange + +On Wed, 2003-01-22 at 18:59, Stephan Szabo wrote: +> +> On 22 Jan 2003, John Lange wrote: +> +> > I have a database that makes fairly extensive use of table Inheritance. +> > +> > Structure is one parent table and 5 child tables as follows: +> > +> > tbl_objects (parent table) +> > -> tbl_viewers +> > -> tbl_documents +> > -> tbl_icons +> > -> tbl_massemails +> > -> tbl_formats +> > +> > I have two questions: +> > +> > First, if I create an index on the parent table will queries to the +> > child tables use that index? +> +> AFAIK no since indices aren't inherited. +> +> > Secondly, I tried to use explain to find out but I got very strange +> > results. It appears to read all the child tables even when you specify +> > only the parent table. In this case this appears to make the select do 6 +> > queries instead of only 1. Obviously a huge performance hit. And none of +> > them uses the index though the table only has 420 rows at the moment so +> > that might be why its just doing a scan (though IMHO 'explain' should +> > explain that it isn't using the available index and why). +> +> It seems reasonable to me since given the # of rows and the estimated +> row width the table is probably only like 5 or 6 pages. Reading the index +> is unlikely to make life much better given an index read, seek in heap +> file, read heap file page. +> +> > I can't say that I'm reading these results properly but here they are: +> > +> > "EXPLAIN select * from tbl_objects where id = 1;" +> +> This gets any rows in tbl_objects that have id=1 and any rows in any +> subtables that have id=1. Is that the intended effect? +> +> + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 21:27:22 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4E757475D99 + for ; + Wed, 22 Jan 2003 21:27:21 -0500 (EST) +Received: from spirit.aldeiadigital.com.br + (iplus-fac-137.xdsl-fixo.ctbcnetsuper.com.br [200.225.213.137]) + by postgresql.org (Postfix) with ESMTP id BE14C475AE4 + for ; + Wed, 22 Jan 2003 21:27:18 -0500 (EST) +Received: from aldeiadigital.com.br (localhost.localdomain [127.0.0.1]) + by spirit.aldeiadigital.com.br (8.11.6/8.11.6) with SMTP id + h0N2Qil03476 + for ; Thu, 23 Jan 2003 00:26:44 -0200 +Received: from 200.225.202.15 (SquirrelMail authenticated user alepaes) + by webmail.ad2.com.br with HTTP; + Thu, 23 Jan 2003 00:26:44 -0200 (BRST) +Message-ID: <10635.200.225.202.15.1043288804.squirrel@webmail.ad2.com.br> +Date: Thu, 23 Jan 2003 00:26:44 -0200 (BRST) +Subject: Same query, same performance +From: "alexandre :: aldeia digital" +To: +X-Priority: 3 +Importance: Normal +X-MSMail-Priority: Normal +X-Mailer: SquirrelMail (version 1.2.7) +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by amavisd-milter (http://amavis.org/) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/251 +X-Sequence-Number: 898 + +Hi all, + +First, sorry for the long mail... + +I have a system with 7 Million of records in 600 tables. +My actual production machine is: P4 1.6G, 3 IDE 7200, 1GB PC133 +My new machine production is: Dual Xeon 2.0G HT, 1GB DDR266 ECC +3 SCSI with HW Raid 5 + +The postgresql.conf is the SAME in both systems and I test +with no other connections, only my local test. + +shared_buffers = 80000 +effective_cache_size = 60000 +random_page_cost = 2.5 +cpu_tuple_cost = 0.001 +cpu_index_tuple_cost = 0.0001 +cpu_operator_cost = 0.00025 + +My question is: + +If I execute the same query executed a lot of times, the +duration is praticaly the same in both systems ? + +1) ! 1.185424 elapsed 1.090000 user 0.100000 system sec +2) ! 1.184415 elapsed 1.070000 user 0.120000 system sec +3) ! 1.185209 elapsed 1.100000 user 0.080000 system sec + +If the disks is not read directly, the system must find +the rows in RAM. If it find in RAM, why so diffrents machines +have the times of execution and why the times does not down ??? + +The variations of query show bellow have the times pratically +equals and my system send thousands os this querys with a +thousands of 1.18 seconds... :( + +Very thank�s + +Alexandre + + +Query: +[postgres@host1 data]$ psql -c "explain SELECT T2.fi15emp05, +T2.fi15flagcf, T2.fi15codcf, T1.Fn06Emp07, T1.Fn06TipTit, T1.Fn06TitBan, +T1.Fn06Conta1, T1.Fn06NumTit, T1.Fn06Desdob, T1.Fn05CodPre, T1.Fn06eCli1, +T1.Fn06tCli1, T1.Fn06cCli1, T2.fi15nome FROM (FN06T T1 LEFT JOIN FI15T +T2 ON T2.fi15emp05 = T1.Fn06eCli1 AND T2.fi15flagcf = T1.Fn06tCli1 AND +T2.fi15codcf = T1.Fn06cCli1) WHERE ( T1.Fn06Emp07 = '1' AND +T1.Fn06TipTit = 'R' ) AND ( T1.Fn06TitBan = '002021001525 +' ) ORDER BY T1.Fn06Emp07, T1.Fn06TipTit, T1.Fn06NumTit, T1.Fn06Desdob, +T1.Fn05CodPre, T1.Fn06eCli1, T1.Fn06tCli1, T1.Fn06cCli1" Pro13Z + QUERY PLAN +----------------------------------------------------------------------------------------------------------------------------------------------- + Sort (cost=25875.53..25875.53 rows=15 width=155) + Sort Key: t1.fn06emp07, t1.fn06tiptit, t1.fn06numtit, t1.fn06desdob, +t1.fn05codpre, t1.fn06ecli1, t1.fn06tcli1, t1.fn06ccli1 + -> Nested Loop (cost=0.00..25875.50 rows=15 width=155) + -> Seq Scan on fn06t t1 (cost=0.00..25808.30 rows=15 width=95) + Filter: ((fn06emp07 = 1::smallint) AND (fn06tiptit = +'R'::bpchar) AND (fn06titban = '002021001525 + '::bpchar)) + -> Index Scan using fi15t_pkey on fi15t t2 (cost=0.00..4.33 +rows=1 width=60) + Index Cond: ((t2.fi15emp05 = "outer".fn06ecli1) AND +(t2.fi15flagcf = "outer".fn06tcli1) AND (t2.fi15codcf = +"outer".fn06ccli1)) +(7 rows) + +*** AND FROM LOG when a execute the query: + +2003-01-23 00:09:49 [3372] LOG: duration: 1.285900 sec +2003-01-23 00:09:49 [3372] LOG: QUERY STATISTICS +! system usage stats: +! 1.286001 elapsed 1.240000 user 0.040000 system sec +! [1.250000 user 0.040000 sys total] +! 0/0 [0/0] filesystem blocks in/out +! 50526/130 [50693/372] page faults/reclaims, 0 [0] swaps +! 0 [0] signals rcvd, 0/0 [0/0] messages rcvd/sent +! 0/0 [0/0] voluntary/involuntary context switches +! buffer usage stats: +! Shared blocks: 0 read, 0 written, buffer hit +rate = 100.00% +! Local blocks: 0 read, 0 written, buffer hit +rate = 0.00% +! Direct blocks: 0 read, 0 written + + + + +From pgsql-performance-owner@postgresql.org Wed Jan 22 21:45:16 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6D0E04760DF + for ; + Wed, 22 Jan 2003 21:45:15 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id A513A4760B7 + for ; + Wed, 22 Jan 2003 21:45:14 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 88368D616; Wed, 22 Jan 2003 18:45:18 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 7DEF35C03; Wed, 22 Jan 2003 18:45:18 -0800 (PST) +Date: Wed, 22 Jan 2003 18:45:18 -0800 (PST) +From: Stephan Szabo +To: John Lange +Cc: +Subject: Re: Query plan and Inheritance. Weird behavior +In-Reply-To: <1043287916.2142.76.camel@johnlaptop.darkcore.net> +Message-ID: <20030122183939.I5182-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/252 +X-Sequence-Number: 899 + + +On 22 Jan 2003, John Lange wrote: + +> Creating child tables by inheriting from another table doesn't really do +> what I consider to be 'true' inheritance, at least not in the way I +> expected as a programmer. +> +> Postgres seems to create "child" tables by first fully duplicating the +> parent table and then adding the new columns to it. It then links the +> tables internally some how so that a query on a parent table also +> queries the child tables. + +That pretty much sums up my understanding of it. + +[snip] +> In this way the parent table would not need to know, nor would it care +> about child tables in any way (just like inheritance in most programming +> languages). If done this way a select on a parent table would only +> require the retrieval of a single row and a select on a child table +> would only require the retrieval of two rows (one in the child table and +> one in the parent table). + +As opposed to needing one row from a select on a child table and +effectively a union all when selecting from the parent. There are up and +down sides of both implementations, and I haven't played with it enough +to speak meaningfully on it. + +> I don't pretend to know the intricacies of Postgres performance but this +> is the way I'm interpreting the data from the explains. + +As a side note, for a better understanding of timings, explain analyze is +much better than plain explain which only gives the plan and estimates. + + +From pgsql-performance-owner@postgresql.org Thu Jan 23 01:08:20 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1EDCE476501 + for ; + Thu, 23 Jan 2003 01:08:17 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 2E26C476393 + for ; + Thu, 23 Jan 2003 01:07:50 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0N67l5u023642; + Thu, 23 Jan 2003 01:07:47 -0500 (EST) +To: Stephan Szabo +Cc: John Lange , pgsql-performance@postgresql.org +Subject: Re: Query plan and Inheritance. Weird behavior +In-reply-to: <20030122183939.I5182-100000@megazone23.bigpanda.com> +References: <20030122183939.I5182-100000@megazone23.bigpanda.com> +Comments: In-reply-to Stephan Szabo + message dated "Wed, 22 Jan 2003 18:45:18 -0800" +Date: Thu, 23 Jan 2003 01:07:47 -0500 +Message-ID: <23641.1043302067@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/253 +X-Sequence-Number: 900 + +> On 22 Jan 2003, John Lange wrote: +>> In this way the parent table would not need to know, nor would it care +>> about child tables in any way (just like inheritance in most programming +>> languages). If done this way a select on a parent table would only +>> require the retrieval of a single row and a select on a child table +>> would only require the retrieval of two rows (one in the child table and +>> one in the parent table). + +No, it'd require the retrieval of N rows: you're failing to think about +multiple levels of inheritance or multi-parent inheritance, both of +which are supported reasonably effectively by the current model. +My guess is that this scheme would crash and burn just on locking +considerations. (When you want to update a child row, what locks do you +have to get in what order? With pieces of the row scattered through +many tables, it'd be pretty messy.) + +You may care to look in the pghackers archives for prior discussions. +The variant scheme that's sounded most interesting to me so far is to +store *all* rows of an inheritance hierarchy in a single physical table. +This'd require giving up multiple inheritance, but few people seem to +use that, and the other benefits (like being able to enforce uniqueness +constraints over the whole hierarchy with just a standard unique index) +seem worth it. No one's stepped up to bat to do the legwork on the idea +yet, though. One bit that looks pretty tricky is ALTER TABLE ADD +COLUMN. + + regards, tom lane + +From pgsql-general-owner@postgresql.org Thu Jan 23 17:24:22 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8F1A4476FB1 + for ; + Thu, 23 Jan 2003 03:21:30 -0500 (EST) +Received: from mail.sarkor.com (unknown [81.95.224.36]) + by postgresql.org (Postfix) with SMTP id 5BBE94769B2 + for ; + Thu, 23 Jan 2003 03:14:24 -0500 (EST) +Received: (qmail 8423 invoked by uid 507); 23 Jan 2003 08:14:20 -0000 +Received: from thor@sarkor.com by mail.sarkor.com by uid 504 with + qmail-scanner-1.14 (clamscan: 0.51. Clear:. + Processed in 0.685745 secs); 23 Jan 2003 08:14:20 -0000 +Received: from unknown (HELO timur) (81.95.224.66) + by mail.sarkor.com with SMTP; 23 Jan 2003 08:14:19 -0000 +Date: Thu, 23 Jan 2003 13:14:25 +0500 +From: Timur Irmatov +X-Mailer: The Bat! (v1.61) +Reply-To: Timur Irmatov +X-Priority: 3 (Normal) +Message-ID: <746750156.20030123131425@sarkor.com> +To: pgsql-performance@postgresql.org +Cc: pgsql-general@postgresql.org +Subject: types & index usage +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/967 +X-Sequence-Number: 36088 + +Hi! + +I have a table with year, month, day and hour fields (all SMALLINT +type). Selecting one row from it takes about 40 msecs, and I am +trying now to use DATE type instead of first three fields. + +Now select time decreased to less than millisecond, but I found that i +must use this form: hour=10::smallint instead of simple hour=10, +because in the latter case PostgreSQL does sequential scan. + +I've heard something about type coercion issues, so I just want to say +that it is very funny to see such sort of things... + + +From pgsql-performance-owner@postgresql.org Thu Jan 23 03:23:55 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E71A5476837 + for ; + Thu, 23 Jan 2003 03:23:53 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 32F45476653 + for ; + Thu, 23 Jan 2003 03:15:39 -0500 (EST) +Received: from klaster.net (pa158.krakow.cvx.ppp.tpnet.pl [213.76.36.158]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP id 5CFE22B87B + for ; + Thu, 23 Jan 2003 09:11:13 +0100 (CET) +Message-ID: <3E2FA5B9.1030105@klaster.net> +Date: Thu, 23 Jan 2003 09:20:09 +0100 +From: Tomasz Myrta +User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; + rv:1.2b) Gecko/20021016 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: pgsql-performance@postgresql.org +Subject: Re: Same query, same performance +References: <10635.200.225.202.15.1043288804.squirrel@webmail.ad2.com.br> +In-Reply-To: <10635.200.225.202.15.1043288804.squirrel@webmail.ad2.com.br> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/255 +X-Sequence-Number: 902 + +alexandre :: aldeia digital wrote: + +>Hi all, +> +>First, sorry for the long mail... +> +>I have a system with 7 Million of records in 600 tables. +>My actual production machine is: P4 1.6G, 3 IDE 7200, 1GB PC133 +>My new machine production is: Dual Xeon 2.0G HT, 1GB DDR266 ECC +>3 SCSI with HW Raid 5 +> +>The postgresql.conf is the SAME in both systems and I test +>with no other connections, only my local test. +> +>shared_buffers = 80000 +>effective_cache_size = 60000 +>random_page_cost = 2.5 +>cpu_tuple_cost = 0.001 +>cpu_index_tuple_cost = 0.0001 +>cpu_operator_cost = 0.00025 +> +>My question is: +> +>If I execute the same query executed a lot of times, the +>duration is praticaly the same in both systems ? +> +>1) ! 1.185424 elapsed 1.090000 user 0.100000 system sec +>2) ! 1.184415 elapsed 1.070000 user 0.120000 system sec +>3) ! 1.185209 elapsed 1.100000 user 0.080000 system sec +> +>If the disks is not read directly, the system must find +>the rows in RAM. If it find in RAM, why so diffrents machines +>have the times of execution and why the times does not down ??? + +Here is your problem: +-> Seq Scan on fn06t t1 (cost=0.00..25808.30 rows=15 width=95) + Filter: ((fn06emp07 = 1::smallint) AND (fn06tiptit = +'R'::bpchar) AND (fn06titban = '002021001525 + '::bpchar)) + +Problably system has to read from disk whole table fn06t each time, beacuse it +doesn't use index scan. + +Do you have any indexes on table fn06t? How selective are conditions above +How big is this table? Can you use indexes on multiple fields on this table +- it should help, because conditions above return only 15 rows? + +Regards, +Tomasz Myrta + + + + +From pgsql-general-owner@postgresql.org Thu Jan 23 04:16:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 8CBA44762B0; Thu, 23 Jan 2003 04:16:16 -0500 (EST) +Received: from biomax.de (unknown [212.6.137.236]) + by postgresql.org (Postfix) with ESMTP + id 76DEF475ADE; Thu, 23 Jan 2003 04:16:04 -0500 (EST) +Received: from biomax.de (guffert.biomax.de [192.168.3.166]) + by biomax.de (8.8.8/8.8.8) with ESMTP id KAA04877; + Thu, 23 Jan 2003 10:16:01 +0100 +Message-ID: <3E2FB2D1.9020904@biomax.de> +Date: Thu, 23 Jan 2003 10:16:01 +0100 +From: Chantal Ackermann +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Stephan Szabo +Cc: pgsql-general@postgresql.org, pgsql-performance@postgresql.org +Subject: Re: optimizing query +References: <20030122081422.Y96911-100000@megazone23.bigpanda.com> +In-Reply-To: <20030122081422.Y96911-100000@megazone23.bigpanda.com> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/911 +X-Sequence-Number: 36032 + +hi Stephan, + +thank you for your reply. + +I ran vacuum analyze before calling explain. As this is a newly built +database where no rows have been deleted, yet, I thought vacuum full +would have no effect. In fact, BEFORE running vacuum full, the cost of +the query is estimates by explain analyze as 33 secs, and AFTER running +it, the cost is estimate to be 43 secs??? (Hey, I want at least the 10 +secs back ;-) ) + +I have just installed this database on a "bigger" (see the system info +further down) machine, and I expected the queries would run _really_ +fast. especially, as there is a lot more data to be inserted in the +occurrences tables. + +This is the row count of the tables and the output of explain analyze +before and after running vacuum full (after that, I listed some system +and postgresql information): + +relate=# select count(*) from gene; + count +-------- + 218085 +(1 row) + +relate=# select count(*) from disease; + count +-------- + 164597 +(1 row) + +relate=# select count(*) from disease_occurrences_puid; + count +-------- + 471915 +(1 row) + +relate=# select count(*) from gene_occurrences_puid; + count +-------- + 339347 +(1 row) + +relate=# explain analyze SELECT DISTINCT gene.gene_name, +gene_occurrences_puid.puid FROM gene, disease_occurrences_puid, +gene_occurrences_puid WHERE +disease_occurrences_puid.puid=gene_occurrences_puid.puid AND +gene.gene_id=gene_occurrences_puid.gene_id; + + QUERY PLAN + +------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ + Unique (cost=342175.89..352511.77 rows=137812 width=33) (actual +time=32112.66..33139.23 rows=219435 loops=1) + -> Sort (cost=342175.89..345621.18 rows=1378118 width=33) (actual +time=32112.65..32616.14 rows=695158 loops=1) + Sort Key: gene.gene_name, gene_occurrences_puid.puid + -> Merge Join (cost=63671.50..98237.36 rows=1378118 +width=33) (actual time=10061.83..17940.02 rows=695158 loops=1) + Merge Cond: ("outer".puid = "inner".puid) + -> Index Scan using disease_occpd_puid_i on +disease_occurrences_puid (cost=0.00..14538.05 rows=471915 width=4) +(actual time=0.03..3917.99 rows=471915 loops=1) + -> Sort (cost=63671.50..64519.87 rows=339347 width=29) +(actual time=10061.69..10973.64 rows=815068 loops=1) + Sort Key: gene_occurrences_puid.puid + -> Merge Join (cost=0.00..22828.18 rows=339347 +width=29) (actual time=0.21..3760.59 rows=339347 loops=1) + Merge Cond: ("outer".gene_id = "inner".gene_id) + -> Index Scan using gene_pkey on gene +(cost=0.00..7668.59 rows=218085 width=21) (actual time=0.02..955.19 +rows=218073 loops=1) + -> Index Scan using gene_id_puid_uni on +gene_occurrences_puid (cost=0.00..9525.57 rows=339347 width=8) (actual +time=0.02..1523.81 rows=339347 loops=1) + Total runtime: 33244.81 msec +(13 rows) + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +AFTER + +relate=# vacuum full verbose analyze; + +relate=# explain analyze SELECT DISTINCT gene.gene_name, +gene_occurrences_puid.puid FROM gene, disease_occurrences_puid, +gene_occurrences_puid WHERE +disease_occurrences_puid.puid=gene_occurrences_puid.puid AND +gene.gene_id=gene_occurrences_puid.gene_id; + + QUERY PLAN + +------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- + Unique (cost=359069.64..369948.41 rows=145050 width=33) (actual +time=42195.60..43229.04 rows=219435 loops=1) + -> Sort (cost=359069.64..362695.90 rows=1450503 width=33) (actual +time=42195.59..42694.70 rows=695158 loops=1) + Sort Key: gene.gene_name, gene_occurrences_puid.puid + -> Merge Join (cost=63732.51..99264.24 rows=1450503 +width=33) (actual time=13172.40..27973.79 rows=695158 loops=1) + Merge Cond: ("outer".puid = "inner".puid) + -> Index Scan using disease_occpd_puid_i on +disease_occurrences_puid (cost=0.00..14543.06 rows=471915 width=4) +(actual time=36.50..10916.29 rows=471915 loops=1) + -> Sort (cost=63732.51..64580.88 rows=339347 width=29) +(actual time=13126.56..14048.38 rows=815068 loops=1) + Sort Key: gene_occurrences_puid.puid + -> Merge Join (cost=0.00..22889.19 rows=339347 +width=29) (actual time=58.00..6775.55 rows=339347 loops=1) + Merge Cond: ("outer".gene_id = "inner".gene_id) + -> Index Scan using gene_pkey on gene +(cost=0.00..7739.91 rows=218085 width=21) (actual time=29.00..3416.01 +rows=218073 +loops=1) + -> Index Scan using gene_id_puid_uni on +gene_occurrences_puid (cost=0.00..9525.57 rows=339347 width=8) (actual +time=28.69..1936.83 rows=339347 loops=1) + Total runtime: 43338.94 msec + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + +Postgres Version: 7.3.1 +CPU: 1666.767 MHz +RAM: 2070492 kB +shmmax/shmall: 1048576000 + +postgresql.conf: +shared_buffers: 121600 +max_connections: 64 +max_fsm_relations = 200 +max_fsm_pages = 40000 +effective_cache_size = 8000 + +******************************************************************** + +Thank you again for your interest and help! + +Chantal + + +Stephan Szabo wrote: +> (Replying to general and performance in a hope to move this +> to performance after a couple of replies). +> +> On Wed, 22 Jan 2003, Chantal Ackermann wrote: +> +> +>>I am getting the following output from EXPLAIN, concerning a query with +>>joins. The merge uses index scans but takes too long, in my opinion. The +>>query is in fact only a part (subquery) of another one, but it is the +>>bottle neck. +>> +>>As I am quite ignorant in optimizing queries, and I have no idea where +>>to find documentation on the net on how to learn optimizing my queries, +>>I am posting this here in hope someone will give me either tips how to +>>optimize, or where to find some tutorial that could help me get along on +>>my own. +>> +>>dropping the "DISTINCT" has some effect, but I can't really do without. +> +> +> The first thing is, have you done ANALYZE recently to make sure that the +> statistics are correct and what does EXPLAIN ANALYZE give you (that will +> run the query and give the estimate and actual). Also, if you haven't +> vacuumed recently, you may want to vacuum full. +> +> How many rows are there on gene, disease and both occurrances tables? +> I'd wonder if perhaps using explicit sql join syntax (which postgres uses +> to constrain order) to join disease and disease_occurrences_puid before +> joining it to the other two would be better or worse in practice. +> +> + + +From pgsql-hackers-owner@postgresql.org Thu Jan 23 05:12:36 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 3C26F476279; Thu, 23 Jan 2003 05:12:34 -0500 (EST) +Received: from localhost.localdomain (unknown [194.204.44.121]) + by postgresql.org (Postfix) with ESMTP + id 9192D475AE4; Thu, 23 Jan 2003 05:12:19 -0500 (EST) +Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) + by localhost.localdomain (8.12.5/8.12.5) with ESMTP id h0NABSHf002506; + Thu, 23 Jan 2003 12:11:28 +0200 +Received: (from hannu@localhost) + by localhost.localdomain (8.12.5/8.12.5/Submit) id h0NAB87w002504; + Thu, 23 Jan 2003 12:11:08 +0200 +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: Terrible performance on wide selects +From: Hannu Krosing +To: Tom Lane +Cc: Dann Corbit , + Steve Crawford , + pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +In-Reply-To: <25622.1043281087@sss.pgh.pa.us> +References: + + <25622.1043281087@sss.pgh.pa.us> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1043316668.2348.15.camel@localhost.localdomain> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 23 Jan 2003 12:11:08 +0200 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/871 +X-Sequence-Number: 34481 + +Tom Lane kirjutas N, 23.01.2003 kell 02:18: +> "Dann Corbit" writes: +> > Why not waste a bit of memory and make the row buffer the maximum +> > possible length? +> > E.g. for varchar(2000) allocate 2000 characters + size element and point +> > to the start of that thing. +> +> Surely you're not proposing that we store data on disk that way. +> +> The real issue here is avoiding overhead while extracting columns out of +> a stored tuple. We could perhaps use a different, less space-efficient +> format for temporary tuples in memory than we do on disk, but I don't +> think that will help a lot. The nature of O(N^2) bottlenecks is you +> have to kill them all --- for example, if we fix printtup and don't do +> anything with ExecEvalVar, we can't do more than double the speed of +> Steve's example, so it'll still be slow. So we must have a solution for +> the case where we are disassembling a stored tuple, anyway. +> +> I have been sitting here toying with a related idea, which is to use the +> heap_deformtuple code I suggested before to form an array of pointers to +> Datums in a specific tuple (we could probably use the TupleTableSlot +> mechanisms to manage the memory for these). Then subsequent accesses to +> individual columns would just need an array-index operation, not a +> nocachegetattr call. The trick with that would be that if only a few +> columns are needed out of a row, it might be a net loss to compute the +> Datum values for all columns. How could we avoid slowing that case down +> while making the wide-tuple case faster? + +make the pointer array incrementally for O(N) performance: + +i.e. for tuple with 100 cols, allocate an array of 100 pointers, plus +keep count of how many are actually valid, + +so the first call to get col[5] will fill first 5 positions in the array +save said nr 5 and then access tuple[ptrarray[5]] + +next call to get col[75] will start form col[5] and fill up to col[75] + +next call to col[76] will start form col[75] and fill up to col[76] + +next call to col[60] will just get tuple[ptrarray[60]] + +the above description assumes 1-based non-C arrays ;) + +-- +Hannu Krosing + +From pgsql-hackers-owner@postgresql.org Thu Jan 23 05:29:09 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id AB3B247628E; Thu, 23 Jan 2003 05:29:06 -0500 (EST) +Received: from localhost.localdomain (unknown [194.204.44.121]) + by postgresql.org (Postfix) with ESMTP + id 4CD92475AE4; Thu, 23 Jan 2003 05:29:05 -0500 (EST) +Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) + by localhost.localdomain (8.12.5/8.12.5) with ESMTP id h0NASNHf002570; + Thu, 23 Jan 2003 12:28:24 +0200 +Received: (from hannu@localhost) + by localhost.localdomain (8.12.5/8.12.5/Submit) id h0NASLSs002568; + Thu, 23 Jan 2003 12:28:21 +0200 +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: [PERFORM] Terrible performance on wide selects +From: Hannu Krosing +To: Dann Corbit +Cc: Tom Lane , + Steve Crawford , + pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +In-Reply-To: + +References: + +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1043317701.2348.32.camel@localhost.localdomain> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 23 Jan 2003 12:28:21 +0200 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/872 +X-Sequence-Number: 34482 + +Dann Corbit kirjutas N, 23.01.2003 kell 02:39: +> [snip] +> > For the disk case, why not have the start of the record +> > contain an array of offsets to the start of the data for each +> > column? It would only be necessary to have a list for +> > variable fields. +> > +> > So (for instance) if you have 12 variable fields, you would +> > store 12 integers at the start of the record. +> +> You have to store this information anyway (for variable length objects). +> By storing it at the front of the record you would lose nothing (except +> the logical coupling of an object with its length). But I would think +> that it would not consume any additional storage. + +I don't think it will win much either (except for possible cache +locality with really huge page sizes), as the problem is _not_ scanning +over big strings finding their end marker, but instead is chasing long +chains of pointers. + +There could be some merit in the idea of storing in the beginning of +tuple all pointers starting with first varlen field (16 bit int should +be enough) +so people can minimize the overhead by moving fixlen fields to the +beginning. once we have this setup, we no longer need the varlen fields +/stored/ together with field data. + +this adds complexity of converting form (len,data) to ptr,...,data) when +constructing the tuple + +as tuple (int,int,int,varchar,varchar) + +which is currently stored as + +(intdata1, intdata2, intdata3, (len4, vardata4), (len5,vardata5)) + +should be rewritten on storage to + +(ptr4,ptr5),(intdata1, intdata2, intdata3, vardata4,vardata5) + +but it seems to solve the O(N) problem quite nicely (and forces no +storage growth for tuples with fixlen fields in the beginning of tuple) + +and we must also account for NULL fields in calculations . + +-- +Hannu Krosing + +From pgsql-hackers-owner@postgresql.org Thu Jan 23 05:33:02 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 1FA9A4768F7; Thu, 23 Jan 2003 05:32:59 -0500 (EST) +Received: from localhost.localdomain (unknown [194.204.44.121]) + by postgresql.org (Postfix) with ESMTP + id 1BF9F476A0F; Thu, 23 Jan 2003 05:30:55 -0500 (EST) +Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) + by localhost.localdomain (8.12.5/8.12.5) with ESMTP id h0NAUsHf002610; + Thu, 23 Jan 2003 12:30:55 +0200 +Received: (from hannu@localhost) + by localhost.localdomain (8.12.5/8.12.5/Submit) id h0NAUmw0002608; + Thu, 23 Jan 2003 12:30:48 +0200 +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: Terrible performance on wide selects +From: Hannu Krosing +To: Tom Lane +Cc: Dann Corbit , + Steve Crawford , + pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +In-Reply-To: <25521.1043280242@sss.pgh.pa.us> +References: + + <25521.1043280242@sss.pgh.pa.us> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1043317847.2347.35.camel@localhost.localdomain> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 23 Jan 2003 12:30:48 +0200 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/873 +X-Sequence-Number: 34483 + +Tom Lane kirjutas N, 23.01.2003 kell 02:04: +> "Dann Corbit" writes: +> > Maybe I don't really understand the problem, but it seems simple enough +> > to do it once for the whole query. +> +> We already do cache column offsets when they are fixed. The code that's +> the problem executes when there's a variable-width column in the table +> --- which means that all columns to its right are not at fixed offsets, +> and have to be scanned for separately in each tuple, AFAICS. + +Not only varlen columns, but also NULL columns forbid knowing the +offsets beforehand. + +-- +Hannu Krosing + +From pgsql-hackers-owner@postgresql.org Thu Jan 23 05:44:28 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id CF19A476DC6; Thu, 23 Jan 2003 05:44:24 -0500 (EST) +Received: from localhost.localdomain (unknown [194.204.44.121]) + by postgresql.org (Postfix) with ESMTP + id 1CF06476E42; Thu, 23 Jan 2003 05:41:52 -0500 (EST) +Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) + by localhost.localdomain (8.12.5/8.12.5) with ESMTP id h0NAfpHf002670; + Thu, 23 Jan 2003 12:41:52 +0200 +Received: (from hannu@localhost) + by localhost.localdomain (8.12.5/8.12.5/Submit) id h0NAfmZ1002668; + Thu, 23 Jan 2003 12:41:48 +0200 +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: Terrible performance on wide selects +From: Hannu Krosing +To: Tom Lane +Cc: Dann Corbit , + Steve Crawford , + pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +In-Reply-To: <1043316668.2348.15.camel@localhost.localdomain> +References: + + <25622.1043281087@sss.pgh.pa.us> + <1043316668.2348.15.camel@localhost.localdomain> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1043318508.2347.39.camel@localhost.localdomain> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 23 Jan 2003 12:41:48 +0200 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/874 +X-Sequence-Number: 34484 + +Hannu Krosing kirjutas N, 23.01.2003 kell 12:11: + +> make the pointer array incrementally for O(N) performance: +> +> i.e. for tuple with 100 cols, allocate an array of 100 pointers, plus +> keep count of how many are actually valid, + +Additionally, this should also make repeted determining of NULL fields +faster - just put a NULL-pointer in and voila - no more bit-shifting and +AND-ing to find out if the field is null. + +One has to watch the NULL bitmap on fist pass anyway. + +> so the first call to get col[5] will fill first 5 positions in the array +> save said nr 5 and then access tuple[ptrarray[5]] +> +> next call to get col[75] will start form col[5] and fill up to col[75] +> +> next call to col[76] will start form col[75] and fill up to col[76] +> +> next call to col[60] will just get tuple[ptrarray[60]] +> +> the above description assumes 1-based non-C arrays ;) +-- +Hannu Krosing + +From pgsql-hackers-owner@postgresql.org Thu Jan 23 05:56:11 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 82BD7476EF4; Thu, 23 Jan 2003 05:56:09 -0500 (EST) +Received: from dcave.digsys.bg (dcave.digsys.bg [192.92.129.5]) + by postgresql.org (Postfix) with ESMTP + id 4AAA14765DD; Thu, 23 Jan 2003 05:49:56 -0500 (EST) +Received: from dcave.digsys.bg (daniel@localhost.digsys.bg [127.0.0.1]) + by dcave.digsys.bg (8.11.6/8.10.1) with ESMTP id h0NAi8Y21333; + Thu, 23 Jan 2003 12:44:12 +0200 (EET) +Message-Id: <200301231044.h0NAi8Y21333@dcave.digsys.bg> +X-Mailer: exmh version 2.1.0 09/18/1999 +To: Hannu Krosing +Cc: Tom Lane , Dann Corbit , + Steve Crawford , + pgsql-performance@postgresql.org, pgsql-hackers@postgresql.org +Subject: Re: Terrible performance on wide selects +In-reply-to: Your message of "23 Jan 2003 12:30:48 +0200." + <1043317847.2347.35.camel@localhost.localdomain> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Date: Thu, 23 Jan 2003 12:44:04 +0200 +From: Daniel Kalchev +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/875 +X-Sequence-Number: 34485 + +>>>Hannu Krosing said: + > Tom Lane kirjutas N, 23.01.2003 kell 02:04: + > > We already do cache column offsets when they are fixed. The code that's + > > the problem executes when there's a variable-width column in the table + > > --- which means that all columns to its right are not at fixed offsets, + > > and have to be scanned for separately in each tuple, AFAICS. + > + > Not only varlen columns, but also NULL columns forbid knowing the + > offsets beforehand. + +Does this mean, that constructing tables where fixed length fields are +'before' variable lenght fields and 'possibly null' fields might increase +performance? + +Daniel + + +From pgsql-hackers-owner@postgresql.org Thu Jan 23 09:42:05 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 265904769B2 + for ; + Thu, 23 Jan 2003 09:42:01 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id C58794768C4 + for ; + Thu, 23 Jan 2003 09:41:36 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0NEfP5u025662; + Thu, 23 Jan 2003 09:41:25 -0500 (EST) +To: Hannu Krosing +Cc: Dann Corbit , + Steve Crawford , + pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +Subject: Re: Terrible performance on wide selects +In-reply-to: <1043318508.2347.39.camel@localhost.localdomain> +References: + + <25622.1043281087@sss.pgh.pa.us> + <1043316668.2348.15.camel@localhost.localdomain> + <1043318508.2347.39.camel@localhost.localdomain> +Comments: In-reply-to Hannu Krosing + message dated "23 Jan 2003 12:41:48 +0200" +Date: Thu, 23 Jan 2003 09:41:25 -0500 +Message-ID: <25661.1043332885@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/881 +X-Sequence-Number: 34491 + +Hannu Krosing writes: +>> i.e. for tuple with 100 cols, allocate an array of 100 pointers, plus +>> keep count of how many are actually valid, + +> Additionally, this should also make repeted determining of NULL fields +> faster - just put a NULL-pointer in and voila - no more bit-shifting and +> AND-ing to find out if the field is null. + +Right, the output of the operation would be a pair of arrays: Datum +values and is-null flags. (NULL pointers don't work for pass-by-value +datatypes.) + +I like the idea of keeping track of a last-known-column position and +incrementally extending that as needed. + +I think the way to manage this is to add the overhead data (the output +arrays and last-column state) to TupleTableSlots. Then we'd have +a routine similar to heap_getattr except that it takes a TupleTableSlot +and makes use of the extra state data. The infrastructure to manage +the state data is already in place: for example, ExecStoreTuple would +reset the last-known-column to 0, ExecSetSlotDescriptor would be +responsible for allocating the output arrays using the natts value from +the provided tupdesc, etc. + +This wouldn't help for accesses that are not in the context of a slot, +but certainly all the ones from ExecEvalVar are. The executor always +works with tuples stored in slots, so I think we could fix all the +high-traffic cases this way. + + regards, tom lane + +From pgsql-hackers-owner@postgresql.org Thu Jan 23 09:47:42 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 178A1476910 + for ; + Thu, 23 Jan 2003 09:47:41 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id DE3FF476A55 + for ; + Thu, 23 Jan 2003 09:46:52 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0NEko5u025702; + Thu, 23 Jan 2003 09:46:51 -0500 (EST) +To: Hannu Krosing +Cc: Dann Corbit , + Steve Crawford , + pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +Subject: Re: [PERFORM] Terrible performance on wide selects +In-reply-to: <1043317701.2348.32.camel@localhost.localdomain> +References: + + <1043317701.2348.32.camel@localhost.localdomain> +Comments: In-reply-to Hannu Krosing + message dated "23 Jan 2003 12:28:21 +0200" +Date: Thu, 23 Jan 2003 09:46:50 -0500 +Message-ID: <25701.1043333210@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/882 +X-Sequence-Number: 34492 + +Hannu Krosing writes: +> as tuple (int,int,int,varchar,varchar) +> which is currently stored as +> (intdata1, intdata2, intdata3, (len4, vardata4), (len5,vardata5)) +> should be rewritten on storage to +> (ptr4,ptr5),(intdata1, intdata2, intdata3, vardata4,vardata5) + +I do not see that this buys anything at all. heap_getattr still has to +make essentially the same calculation as before to determine column +locations, namely adding up column widths. All you've done is move the +data that it has to fetch to make the calculation. If anything, this +will be slower not faster, because now heap_getattr has to keep track +of two positions not one --- not just the next column offset, but also +the index of the next "ptr" to use. In the existing method it only +needs the column offset, because that's exactly where it can pick up +the next length from. + +But the really serious objection is that the datatype functions that +access the data would now also need to be passed two pointers, since +after all they would like to know the length too. That breaks APIs +far and wide :-( + + regards, tom lane + +From pgsql-hackers-owner@postgresql.org Thu Jan 23 09:52:48 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 22295475FB0 + for ; + Thu, 23 Jan 2003 09:52:46 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 2669A476FAE + for ; + Thu, 23 Jan 2003 09:50:24 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0NEo25u025739; + Thu, 23 Jan 2003 09:50:03 -0500 (EST) +To: Daniel Kalchev +Cc: Hannu Krosing , Dann Corbit , + Steve Crawford , + pgsql-performance@postgresql.org, pgsql-hackers@postgresql.org +Subject: Re: Terrible performance on wide selects +In-reply-to: <200301231044.h0NAi8Y21333@dcave.digsys.bg> +References: <200301231044.h0NAi8Y21333@dcave.digsys.bg> +Comments: In-reply-to Daniel Kalchev + message dated "Thu, 23 Jan 2003 12:44:04 +0200" +Date: Thu, 23 Jan 2003 09:50:02 -0500 +Message-ID: <25738.1043333402@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/883 +X-Sequence-Number: 34493 + +Daniel Kalchev writes: +> Does this mean, that constructing tables where fixed length fields are +> 'before' variable lenght fields and 'possibly null' fields might increase +> performance? + +There'd have to be no nulls, period, to get any useful performance +difference --- but yes, in theory putting fixed-length columns before +variable-length ones is a win. + +I wouldn't bother going out to rearrange your schemas though ... at +least not before you do some tests to prove that it's worthwhile. + + regards, tom lane + +From pgsql-general-owner@postgresql.org Thu Jan 23 10:09:22 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 4ADCA476F9A; Thu, 23 Jan 2003 10:09:20 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP + id 8FE98476F74; Thu, 23 Jan 2003 10:05:24 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id A4E17D61B; Thu, 23 Jan 2003 07:05:28 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 9895D5C03; Thu, 23 Jan 2003 07:05:28 -0800 (PST) +Date: Thu, 23 Jan 2003 07:05:28 -0800 (PST) +From: Stephan Szabo +To: Chantal Ackermann +Cc: , + +Subject: Re: optimizing query +In-Reply-To: <3E2FB2D1.9020904@biomax.de> +Message-ID: <20030123070120.Y11731-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/924 +X-Sequence-Number: 36045 + + +On Thu, 23 Jan 2003, Chantal Ackermann wrote: + +> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +> +> Postgres Version: 7.3.1 +> CPU: 1666.767 MHz +> RAM: 2070492 kB +> shmmax/shmall: 1048576000 +> +> postgresql.conf: +> shared_buffers: 121600 +> max_connections: 64 +> max_fsm_relations = 200 +> max_fsm_pages = 40000 +> effective_cache_size = 8000 +> +> ******************************************************************** + +Hmm, how about how many pages are in the various tables, (do a +vacuum verbose for the various tables and what is sort_mem +set to? It's picking the index scan to get the tables in sorted +order, but I wonder if that's really the best plan given it's getting +a large portion of the tables. + +Hmm, what does it do if you set enable_indexscan=off; ? + + +From pgsql-general-owner@postgresql.org Thu Jan 23 10:39:45 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 41E5F475A9E; Thu, 23 Jan 2003 10:39:43 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 9737A476FAE; Thu, 23 Jan 2003 10:26:22 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0NFQJ5u025977; + Thu, 23 Jan 2003 10:26:19 -0500 (EST) +To: Chantal Ackermann +Cc: Stephan Szabo , + pgsql-general@postgresql.org, pgsql-performance@postgresql.org +Subject: Re: [PERFORM] optimizing query +In-reply-to: <3E2FB2D1.9020904@biomax.de> +References: <20030122081422.Y96911-100000@megazone23.bigpanda.com> + <3E2FB2D1.9020904@biomax.de> +Comments: In-reply-to Chantal Ackermann + message dated "Thu, 23 Jan 2003 10:16:01 +0100" +Date: Thu, 23 Jan 2003 10:26:19 -0500 +Message-ID: <25976.1043335579@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/927 +X-Sequence-Number: 36048 + +Chantal Ackermann writes: +> Unique (cost=359069.64..369948.41 rows=145050 width=33) (actual +> time=42195.60..43229.04 rows=219435 loops=1) +> -> Sort (cost=359069.64..362695.90 rows=1450503 width=33) (actual +> time=42195.59..42694.70 rows=695158 loops=1) +> Sort Key: gene.gene_name, gene_occurrences_puid.puid +> -> Merge Join (cost=63732.51..99264.24 rows=1450503 +> width=33) (actual time=13172.40..27973.79 rows=695158 loops=1) +> Merge Cond: ("outer".puid = "inner".puid) +> -> Index Scan using disease_occpd_puid_i on +> disease_occurrences_puid (cost=0.00..14543.06 rows=471915 width=4) +> (actual time=36.50..10916.29 rows=471915 loops=1) +> -> Sort (cost=63732.51..64580.88 rows=339347 width=29) +> (actual time=13126.56..14048.38 rows=815068 loops=1) +> Sort Key: gene_occurrences_puid.puid +> -> Merge Join (cost=0.00..22889.19 rows=339347 +> width=29) (actual time=58.00..6775.55 rows=339347 loops=1) +> Merge Cond: ("outer".gene_id = "inner".gene_id) +> -> Index Scan using gene_pkey on gene +> (cost=0.00..7739.91 rows=218085 width=21) (actual time=29.00..3416.01 +> rows=218073 +> loops=1) +> -> Index Scan using gene_id_puid_uni on +> gene_occurrences_puid (cost=0.00..9525.57 rows=339347 width=8) (actual +> time=28.69..1936.83 rows=339347 loops=1) +> Total runtime: 43338.94 msec + +Seems like most of the time is going into the sort steps. + +> postgresql.conf: +> shared_buffers: 121600 +> max_connections: 64 +> max_fsm_relations = 200 +> max_fsm_pages = 40000 +> effective_cache_size = 8000 + +Try increasing sort_mem. + +Also, I'd back off on shared_buffers if I were you. There's no evidence +that values above a few thousand buy anything. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Jan 23 10:47:16 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id AA0F14771D9 + for ; + Thu, 23 Jan 2003 10:47:14 -0500 (EST) +Received: from johnlaptop.darkcore.net (link.clearoption.com [205.200.121.81]) + by postgresql.org (Postfix) with ESMTP id B3ADD4770B7 + for ; + Thu, 23 Jan 2003 10:36:17 -0500 (EST) +Received: by johnlaptop.darkcore.net (Postfix, from userid 501) + id 0E755F1EB4; Thu, 23 Jan 2003 10:36:11 -0500 (EST) +Subject: Re: Query plan and Inheritance. Weird behavior +From: John Lange +To: Tom Lane +Cc: pgsql-performance@postgresql.org +In-Reply-To: <23641.1043302067@sss.pgh.pa.us> +References: <20030122183939.I5182-100000@megazone23.bigpanda.com> + <23641.1043302067@sss.pgh.pa.us> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +X-Mailer: Ximian Evolution 1.0.8-3mdk +Date: 23 Jan 2003 09:36:11 -0600 +Message-Id: <1043336171.2048.35.camel@johnlaptop.darkcore.net> +Mime-Version: 1.0 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/267 +X-Sequence-Number: 914 + +On Thu, 2003-01-23 at 00:07, Tom Lane wrote: +> > On 22 Jan 2003, John Lange wrote: +> >> In this way the parent table would not need to know, nor would it care +> >> about child tables in any way (just like inheritance in most programming +> >> languages). If done this way a select on a parent table would only +> >> require the retrieval of a single row and a select on a child table +> >> would only require the retrieval of two rows (one in the child table and +> >> one in the parent table). +> +> No, it'd require the retrieval of N rows: you're failing to think about +> multiple levels of inheritance or multi-parent inheritance, both of +> which are supported reasonably effectively by the current model. + +Lets not be too nit-picky here. In the case of multiple layers of +inheritance you are still only selecting two rows (at a time), one +child, one parent. However if the parent also has a parent, then the +process repeats, once for every layer. + +This is entirely reasonable and efficient compared to the current model +where a select on a parent table requires the same select to be executed +on EVERY child table. If it's a large expensive JOIN of some kind then +this is verging on un-workable. + +> My guess is that this scheme would crash and burn just on locking +> considerations. (When you want to update a child row, what locks do you +> have to get in what order? With pieces of the row scattered through +> many tables, it'd be pretty messy.) + +You lock the parent on down to the last child. I'm not a database +developer but that seems fairly straight forward? + +The choice between the schema I've suggested and the way it is currently +implemented is a trade off between more efficient selects vs. more +efficient updates. If you are selecting on the parent table more than +updating then my idea is vastly more efficient. If you INSERT a lot then +the current way is marginally better. + +With apologies to the developers, I don't feel the current +implementation is really usable for the simple fact that expensive +operations performed on the parent table causes them to be repeated for +every child table. And, as an added penalty, indexes on parent tables +are NOT inherited to the children so the child operations can be even +more expensive. + +This solution is not that large and I've already got 6 child tables. It +just so happens that I do a LOT of selects on the parent so I'm going to +have to make a decision on where to go from here. + +Solving this programmatically is not really that hard but I've gone a +ways down this path now so I'm not anxious to redo the entire database +schema since we do have customers already using this. + +> You may care to look in the pghackers archives for prior discussions. + +I will, thanks. + +> The variant scheme that's sounded most interesting to me so far is to +> store *all* rows of an inheritance hierarchy in a single physical table. + +Unless I'm not understanding I don't think that works. In my case for +example, a single parent has 4-5 children so the only columns they have +in common are the ones in the parent. Combining them all into a single +table means a big de-normalized table (loads of empty columns). If you +are going to go this route then you might as well just do it. It doesn't +need to be implemented on the DBMS. + +Regards, + +John Lange + +> This'd require giving up multiple inheritance, but few people seem to +> use that, and the other benefits (like being able to enforce uniqueness +> constraints over the whole hierarchy with just a standard unique index) +> seem worth it. No one's stepped up to bat to do the legwork on the idea +> yet, though. One bit that looks pretty tricky is ALTER TABLE ADD +> COLUMN. +> +> regards, tom lane + + +From pgsql-hackers-owner@postgresql.org Thu Jan 23 11:18:34 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 4B3454768C4; Thu, 23 Jan 2003 11:18:33 -0500 (EST) +Received: from platonic.cynic.net (platonic.cynic.net [204.80.150.245]) + by postgresql.org (Postfix) with ESMTP + id 1A5AD477219; Thu, 23 Jan 2003 10:53:50 -0500 (EST) +Received: from angelic.cynic.net (angelic-platonic.cvpn.cynic.net + [198.73.220.226]) by platonic.cynic.net (Postfix) with ESMTP + id A2B85BF4C; Thu, 23 Jan 2003 15:53:34 +0000 (UTC) +Received: from localhost (localhost [127.0.0.1]) + by angelic.cynic.net (Postfix) with ESMTP + id D14B48736; Fri, 24 Jan 2003 00:50:27 +0900 (JST) +Date: Fri, 24 Jan 2003 00:50:27 +0900 (JST) +From: Curt Sampson +To: Daniel Kalchev +Cc: Hannu Krosing , Tom Lane , + Dann Corbit , + Steve Crawford , + pgsql-performance@postgresql.org, pgsql-hackers@postgresql.org +Subject: Re: [PERFORM] Terrible performance on wide selects +In-Reply-To: <200301231044.h0NAi8Y21333@dcave.digsys.bg> +Message-ID: +References: <200301231044.h0NAi8Y21333@dcave.digsys.bg> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/892 +X-Sequence-Number: 34502 + +On Thu, 23 Jan 2003, Daniel Kalchev wrote: + +> Does this mean, that constructing tables where fixed length fields are +> 'before' variable lenght fields and 'possibly null' fields might increase +> performance? + +This, I believe, is why DB2 always puts (in physical storage) all of the +fixed-length fields before the variable-length fields. + +cjs +-- +Curt Sampson +81 90 7737 2974 http://www.netbsd.org + Don't you know, in this new Dark Age, we're all light. --XTC + +From pgsql-general-owner@postgresql.org Thu Jan 23 11:17:52 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id EDE4A476FC7; Thu, 23 Jan 2003 11:17:50 -0500 (EST) +Received: from biomax.de (unknown [212.6.137.236]) + by postgresql.org (Postfix) with ESMTP + id 45FD74770A3; Thu, 23 Jan 2003 10:53:09 -0500 (EST) +Received: from biomax.de (guffert.biomax.de [192.168.3.166]) + by biomax.de (8.8.8/8.8.8) with ESMTP id QAA18901; + Thu, 23 Jan 2003 16:52:51 +0100 +Message-ID: <3E300FD3.3030100@biomax.de> +Date: Thu, 23 Jan 2003 16:52:51 +0100 +From: Chantal Ackermann +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Tom Lane , + Stephan Szabo +Cc: pgsql-general@postgresql.org, pgsql-performance@postgresql.org +Subject: Re: [PERFORM] optimizing query +References: <20030122081422.Y96911-100000@megazone23.bigpanda.com> + <3E2FB2D1.9020904@biomax.de> <25976.1043335579@sss.pgh.pa.us> +In-Reply-To: <25976.1043335579@sss.pgh.pa.us> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/928 +X-Sequence-Number: 36049 + +hi Stephan, hi Tom, + +sort_mem was at its default: 1024. I increased it, and the query takes +even longer (~ 36 secs). I tried two different values: 4096 and 8192, +this last time I reduced the shared_buffers to 25600 (--> ~ 37 secs). +Another point is: after a vacuum, the cost would slightly increase. + +would it help to cluster the index? but as I am using several indexes I +find it difficult to decide on which index to cluster. + +(I paste the output from vacuum full verbose analyze) + +Thanks! +Chantal + + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + +INFO: --Relation public.disease_occurrences_puid-- +INFO: Pages 2079: Changed 0, reaped 0, Empty 0, New 0; Tup 471915: Vac +0, Keep/VTL 0/0, UnUsed 0, MinLen 32, MaxLen 32; Re-using: Free/Avail. +Space 648/648; EndEmpty/Avail. Pages 0/1. + CPU 0.02s/0.05u sec elapsed 0.07 sec. +INFO: Index disease_occpd_puid_i: Pages 1036; Tuples 471915. + CPU 0.00s/0.03u sec elapsed 0.03 sec. +INFO: Index disease_id_puid_uni: Pages 1297; Tuples 471915. + CPU 0.03s/0.05u sec elapsed 0.23 sec. +INFO: Rel disease_occurrences_puid: Pages: 2079 --> 2079; Tuple(s) +moved: 0. + CPU 0.00s/0.00u sec elapsed 0.00 sec. +INFO: Analyzing public.disease_occurrences_puid + +INFO: --Relation public.gene_occurrences_puid-- +INFO: Pages 1495: Changed 0, reaped 0, Empty 0, New 0; Tup 339347: Vac +0, Keep/VTL 0/0, UnUsed 0, MinLen 32, MaxLen 32; Re-using: Free/Avail. +Space 648/648; EndEmpty/Avail. Pages 0/1. + CPU 0.01s/0.04u sec elapsed 0.05 sec. +INFO: Index gene_occpd_puid_i: Pages 746; Tuples 339347. + CPU 0.01s/0.02u sec elapsed 0.03 sec. +INFO: Index gene_id_puid_uni: Pages 934; Tuples 339347. + CPU 0.00s/0.02u sec elapsed 0.02 sec. +INFO: Rel gene_occurrences_puid: Pages: 1495 --> 1495; Tuple(s) moved: 0. + CPU 0.00s/0.00u sec elapsed 0.00 sec. +INFO: Analyzing public.gene_occurrences_puid + +INFO: --Relation public.disease-- +INFO: Pages 1522: Changed 0, reaped 0, Empty 0, New 0; Tup 164597: Vac +0, Keep/VTL 0/0, UnUsed 0, MinLen 44, MaxLen 232; Re-using: Free/Avail. +Space 56920/38388; EndEmpty/Avail. Pages 0/603. + CPU 0.00s/0.04u sec elapsed 0.04 sec. +INFO: Index disease_name_i: Pages 1076; Tuples 164597. + CPU 0.05s/0.02u sec elapsed 0.18 sec. +INFO: Index disease_pkey: Pages 364; Tuples 164597. + CPU 0.00s/0.00u sec elapsed 0.03 sec. +INFO: Index disease_uni: Pages 1168; Tuples 164597. + CPU 0.08s/0.04u sec elapsed 0.22 sec. +INFO: Rel disease: Pages: 1522 --> 1521; Tuple(s) moved: 75. + CPU 0.00s/0.03u sec elapsed 0.04 sec. +INFO: Index disease_name_i: Pages 1077; Tuples 164597: Deleted 75. + CPU 0.00s/0.03u sec elapsed 0.03 sec. +INFO: Index disease_pkey: Pages 364; Tuples 164597: Deleted 75. + CPU 0.01s/0.02u sec elapsed 0.02 sec. +INFO: Index disease_uni: Pages 1168; Tuples 164597: Deleted 75. + CPU 0.00s/0.03u sec elapsed 0.03 sec. +INFO: --Relation pg_toast.pg_toast_7114632-- +INFO: Pages 0: Changed 0, reaped 0, Empty 0, New 0; Tup 0: Vac 0, +Keep/VTL 0/0, UnUsed 0, MinLen 0, MaxLen 0; Re-using: Free/Avail. Space +0/0; EndEmpty/Avail. Pages 0/0. + CPU 0.00s/0.00u sec elapsed 0.00 sec. +INFO: Index pg_toast_7114632_index: Pages 1; Tuples 0. + CPU 0.00s/0.00u sec elapsed 0.01 sec. +INFO: Analyzing public.disease + +INFO: --Relation public.gene-- +INFO: Pages 1566: Changed 0, reaped 0, Empty 0, New 0; Tup 218085: Vac +0, Keep/VTL 0/0, UnUsed 0, MinLen 44, MaxLen 348; Re-using: Free/Avail. +Space 48692/25408; EndEmpty/Avail. Pages 0/365. + CPU 0.01s/0.04u sec elapsed 0.04 sec. +INFO: Index gene_pkey: Pages 481; Tuples 218085. + CPU 0.00s/0.01u sec elapsed 0.01 sec. +INFO: Index gene_uni: Pages 1038; Tuples 218085. + CPU 0.04s/0.01u sec elapsed 0.19 sec. +INFO: Index gene_name_uni: Pages 917; Tuples 218085. + CPU 0.06s/0.00u sec elapsed 0.15 sec. +INFO: Rel gene: Pages: 1566 --> 1564; Tuple(s) moved: 230. + CPU 0.01s/0.06u sec elapsed 0.11 sec. +INFO: Index gene_pkey: Pages 482; Tuples 218085: Deleted 230. + CPU 0.00s/0.03u sec elapsed 0.02 sec. +INFO: Index gene_uni: Pages 1041; Tuples 218085: Deleted 230. + CPU 0.00s/0.04u sec elapsed 0.03 sec. +INFO: Index gene_name_uni: Pages 918; Tuples 218085: Deleted 230. + CPU 0.00s/0.04u sec elapsed 0.03 sec. +INFO: --Relation pg_toast.pg_toast_7114653-- +INFO: Pages 0: Changed 0, reaped 0, Empty 0, New 0; Tup 0: Vac 0, +Keep/VTL 0/0, UnUsed 0, MinLen 0, MaxLen 0; Re-using: Free/Avail. Space +0/0; EndEmpty/Avail. Pages 0/0. + CPU 0.00s/0.00u sec elapsed 0.00 sec. +INFO: Index pg_toast_7114653_index: Pages 1; Tuples 0. + CPU 0.00s/0.00u sec elapsed 0.01 sec. +INFO: Analyzing public.gene + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + + +From pgsql-performance-owner@postgresql.org Thu Jan 23 12:15:49 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1CA7247718F + for ; + Thu, 23 Jan 2003 12:15:48 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 5F1234770F1 + for ; + Thu, 23 Jan 2003 11:59:58 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2323224; Thu, 23 Jan 2003 09:00:02 -0800 +From: "Josh Berkus" +Subject: Re: Same query, same performance +To: "alexandre :: aldeia digital" , + +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Thu, 23 Jan 2003 09:00:02 -0800 +Message-ID: +In-Reply-To: <10635.200.225.202.15.1043288804.squirrel@webmail.ad2.com.br> +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/270 +X-Sequence-Number: 917 + +Alexandre, + +> I have a system with 7 Million of records in 600 tables. +> My actual production machine is: P4 1.6G, 3 IDE 7200, 1GB PC133 +> My new machine production is: Dual Xeon 2.0G HT, 1GB DDR266 ECC +> 3 SCSI with HW Raid 5 + +Well, first of all, those two systems are almost equivalent as far as +Postgres is concerned for simple queries. The extra processor power +will only help you with very complex queries. 3-disk RAID 5 is no +faster ... and sometimes slower ... than IDE for database purposes. + The only real boost to the Xeon is the faster RAM ... which may not +help you if your drive array is the bottleneck. + +> +> The postgresql.conf is the SAME in both systems and I test +> with no other connections, only my local test. +> +> shared_buffers = 80000 +> effective_cache_size = 60000 +> random_page_cost = 2.5 +> cpu_tuple_cost = 0.001 +> cpu_index_tuple_cost = 0.0001 +> cpu_operator_cost = 0.00025 + +Not that it affects the query below, but what about SORT_MEM? + +> If I execute the same query executed a lot of times, the +> duration is praticaly the same in both systems ? +> +> 1) ! 1.185424 elapsed 1.090000 user 0.100000 system sec +> 2) ! 1.184415 elapsed 1.070000 user 0.120000 system sec +> 3) ! 1.185209 elapsed 1.100000 user 0.080000 system sec +> +> If the disks is not read directly, the system must find +> the rows in RAM. If it find in RAM, why so diffrents machines +> have the times of execution and why the times does not down ??? + +I'm pretty sure that PostgreSQL always checks on disk, even when the +same query is run repeatedly. Tom? + +> [postgres@host1 data]$ psql -c "explain SELECT T2.fi15emp05, +> T2.fi15flagcf, T2.fi15codcf, T1.Fn06Emp07, T1.Fn06TipTit, +> T1.Fn06TitBan, +> T1.Fn06Conta1, T1.Fn06NumTit, T1.Fn06Desdob, T1.Fn05CodPre, +> T1.Fn06eCli1, +> T1.Fn06tCli1, T1.Fn06cCli1, T2.fi15nome FROM (FN06T T1 LEFT JOIN +> FI15T +> T2 ON T2.fi15emp05 = T1.Fn06eCli1 AND T2.fi15flagcf = T1.Fn06tCli1 +> AND +> T2.fi15codcf = T1.Fn06cCli1) WHERE ( T1.Fn06Emp07 = '1' AND +> T1.Fn06TipTit = 'R' ) AND ( T1.Fn06TitBan = '002021001525 +> +> ' ) ORDER BY T1.Fn06Emp07, T1.Fn06TipTit, T1.Fn06NumTit, +> T1.Fn06Desdob, +> T1.Fn05CodPre, T1.Fn06eCli1, T1.Fn06tCli1, T1.Fn06cCli1" Pro13Z + +Actually, from your stats, Postgres is doing a pretty good job. 1.18 +seconds to return 15 rows from a 7 million row table searching on not +Indexed columns? I don't think you have anything to complain about. + +If you want less-than-1 second respose time: Add some indexes and keep +the tables VACUUMed so the indexes work. Particularly, add a +multi-column index on ( T1.Fn06Emp07, T1.Fn06TipTit, T1.Fn06TitBan ) + +If you want single-digit-msec response: Get a better disk set for +Postgres: I recommend dual-channel RAID 1 (n addition to indexing). + +-Josh Berkus + + + +From pgsql-hackers-owner@postgresql.org Thu Jan 23 12:58:41 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id B67F7475F32; Thu, 23 Jan 2003 12:58:38 -0500 (EST) +Received: from localhost.localdomain (unknown [194.204.44.121]) + by postgresql.org (Postfix) with ESMTP + id 43EA247651B; Thu, 23 Jan 2003 12:42:35 -0500 (EST) +Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) + by localhost.localdomain (8.12.5/8.12.5) with ESMTP id h0NHgULV001458; + Thu, 23 Jan 2003 19:42:31 +0200 +Received: (from hannu@localhost) + by localhost.localdomain (8.12.5/8.12.5/Submit) id h0NHgQli001456; + Thu, 23 Jan 2003 19:42:26 +0200 +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: Terrible performance on wide selects +From: Hannu Krosing +To: Dann Corbit +Cc: Tom Lane , + Steve Crawford , + pgsql-performance@postgreSQL.org, pgsql-hackers@postgreSQL.org +In-Reply-To: + +References: + +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1043343746.1368.6.camel@localhost.localdomain> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 23 Jan 2003 19:42:26 +0200 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/895 +X-Sequence-Number: 34505 + +Dann Corbit kirjutas N, 23.01.2003 kell 02:22: +> [snip] +> > So (for instance) if you have 12 variable fields, you would +> > store 12 integers at the start of the record. +> +> Additionally, you could implicitly size the integers from the properties +> of the column. A varchar(255) would only need an unsigned char to store +> the offset, but a varchar(80000) would require an unsigned int. + +I guess that the pointer could always be 16-bit, as the offset inside a +tuple will never be more (other issues constrain max page size to 32K) + +varchar(80000) will use TOAST (another file) anyway, but this will be +hidden inside the field storage in the page) + +> ---------------------------(end of broadcast)--------------------------- +> TIP 4: Don't 'kill -9' the postmaster +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Thu Jan 23 17:27:00 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A53C7476768 + for ; + Thu, 23 Jan 2003 16:26:54 -0500 (EST) +Received: from spirit.aldeiadigital.com.br + (iplus-fac-137.xdsl-fixo.ctbcnetsuper.com.br [200.225.213.137]) + by postgresql.org (Postfix) with ESMTP id 1C86F476860 + for ; + Thu, 23 Jan 2003 14:50:27 -0500 (EST) +Received: from aldeiadigital.com.br (localhost.localdomain [127.0.0.1]) + by spirit.aldeiadigital.com.br (8.11.6/8.11.6) with SMTP id + h0NJnbl21150 + for ; Thu, 23 Jan 2003 17:49:37 -0200 +Received: from 200.225.202.15 (SquirrelMail authenticated user alepaes) + by webmail.ad2.com.br with HTTP; + Thu, 23 Jan 2003 17:49:37 -0200 (BRST) +Message-ID: <10840.200.225.202.15.1043351377.squirrel@webmail.ad2.com.br> +Date: Thu, 23 Jan 2003 17:49:37 -0200 (BRST) +Subject: Re: Same query, same performance +From: "alexandre :: aldeia digital" +To: +In-Reply-To: <3E2FA5B9.1030105@klaster.net> +References: <10635.200.225.202.15.1043288804.squirrel@webmail.ad2.com.br> + <3E2FA5B9.1030105@klaster.net> +X-Priority: 3 +Importance: Normal +X-MSMail-Priority: Normal +X-Mailer: SquirrelMail (version 1.2.7) +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by amavisd-milter (http://amavis.org/) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/272 +X-Sequence-Number: 919 + +Tomasz, + +>>1) ! 1.185424 elapsed 1.090000 user 0.100000 system sec +>>2) ! 1.184415 elapsed 1.070000 user 0.120000 system sec +>>3) ! 1.185209 elapsed 1.100000 user 0.080000 system sec +>> +>>If the disks is not read directly, the system must find +>>the rows in RAM. If it find in RAM, why so diffrents machines +>>have the times of execution and why the times does not down ??? +> +> Here is your problem: +> -> Seq Scan on fn06t t1 (cost=0.00..25808.30 rows=15 width=95) +> Filter: ((fn06emp07 = 1::smallint) AND (fn06tiptit = +> 'R'::bpchar) AND (fn06titban = '002021001525 +> '::bpchar)) + +Really! I do not attemp that fn06t does not have an index +with fn06titban ... :) + +Now, tehe time of the querys are < 0.02 sec on P4 +and <0.05 on Xeon. + +Very Thank�s + +Alexandre, + + + +From pgsql-performance-owner@postgresql.org Thu Jan 23 18:03:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E9B83479F13 + for ; + Thu, 23 Jan 2003 17:26:00 -0500 (EST) +Received: from spirit.aldeiadigital.com.br + (iplus-fac-137.xdsl-fixo.ctbcnetsuper.com.br [200.225.213.137]) + by postgresql.org (Postfix) with ESMTP id 74685477146 + for ; + Thu, 23 Jan 2003 15:31:40 -0500 (EST) +Received: from aldeiadigital.com.br (localhost.localdomain [127.0.0.1]) + by spirit.aldeiadigital.com.br (8.11.6/8.11.6) with SMTP id + h0NKV3l21659 + for ; Thu, 23 Jan 2003 18:31:03 -0200 +Received: from 200.225.202.15 (SquirrelMail authenticated user alepaes) + by webmail.ad2.com.br with HTTP; + Thu, 23 Jan 2003 18:31:03 -0200 (BRST) +Message-ID: <10520.200.225.202.15.1043353863.squirrel@webmail.ad2.com.br> +Date: Thu, 23 Jan 2003 18:31:03 -0200 (BRST) +Subject: Re: Same query, same performance +From: "alexandre :: aldeia digital" +To: +In-Reply-To: +References: <10635.200.225.202.15.1043288804.squirrel@webmail.ad2.com.br> + +X-Priority: 3 +Importance: Normal +X-MSMail-Priority: Normal +X-Mailer: SquirrelMail (version 1.2.7) +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Transfer-Encoding: 8bit +X-Virus-Scanned: by amavisd-milter (http://amavis.org/) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/273 +X-Sequence-Number: 920 + +Josh, + +> Alexandre, +> +>> I have a system with 7 Million of records in 600 tables. +>> My actual production machine is: P4 1.6G, 3 IDE 7200, 1GB PC133 +>> My new machine production is: Dual Xeon 2.0G HT, 1GB DDR266 ECC +>> 3 SCSI with HW Raid 5 +> +> Well, first of all, those two systems are almost equivalent as far as +> Postgres is concerned for simple queries. The extra processor power +> will only help you with very complex queries. 3-disk RAID 5 is no +> faster ... and sometimes slower ... than IDE for database purposes. +> The only real boost to the Xeon is the faster RAM ... which may not +> help you if your drive array is the bottleneck. + +Today, I will add more one HD and I will make an RAID 10 ... +In next week i will report my tests to the list... + +> +>> +>> The postgresql.conf is the SAME in both systems and I test +>> with no other connections, only my local test. +>> +>> shared_buffers = 80000 +>> effective_cache_size = 60000 +>> random_page_cost = 2.5 +>> cpu_tuple_cost = 0.001 +>> cpu_index_tuple_cost = 0.0001 +>> cpu_operator_cost = 0.00025 +> +> Not that it affects the query below, but what about SORT_MEM? + +Sort_mem = 32000 + +> Actually, from your stats, Postgres is doing a pretty good job. 1.18 +> seconds to return 15 rows from a 7 million row table searching on not +> Indexed columns? I don't think you have anything to complain about. + +The table have 300000 tuples, the entire database have 7 million. +Tomazs answer the question: a missing index on fn06t ... + +But the query time difference of the systems continue. +I will change the discs and tell to list after... + +Thank�s Josh, + + +Alexandre + + + + + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 00:22:27 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2A9CA477373 + for ; + Fri, 24 Jan 2003 00:22:25 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id BA69B47717F + for ; + Thu, 23 Jan 2003 22:32:41 -0500 (EST) +Received: from [10.0.1.133] (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP id 60AC73BFF4 + for ; + Thu, 23 Jan 2003 22:32:45 -0500 (EST) +Date: Thu, 23 Jan 2003 22:32:58 -0500 +From: Noah Silverman +To: pgsql-performance@postgresql.org +Subject: Crash Recovery +Message-ID: <2147483647.1043361178@[10.0.1.133]> +X-Mailer: Mulberry/3.0.0 (Mac OS X Demo) +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/274 +X-Sequence-Number: 921 + +To preface my question, we are still in the process of evaluating postgres +to determine if we want to switch our production environment over. + +I'm curious about where I can find documentation about crash recovery in +postgres. In mysql, there is a nice table recovery utility (myisamchk). +is there something similar in postgres? What do we do if a table or +database becomes corrupted? (I'm aware of backup techniques, but it isn't +feasible for some of our larger tables. We're already running on raid 5, +but can't do much more) + +Thanks, + +-N + +From pgsql-performance-owner@postgresql.org Fri Jan 24 00:37:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 86DB7477438 + for ; + Fri, 24 Jan 2003 00:37:53 -0500 (EST) +Received: from torque.intervideoinc.com (mail.intervideo.com + [206.112.112.151]) + by postgresql.org (Postfix) with ESMTP id 6C2E84771E9 + for ; + Thu, 23 Jan 2003 23:16:09 -0500 (EST) +Received: from antares.intervideo.com [206.112.112.139] by + torque.intervideoinc.com with ESMTP + (SMTPD32-5.05) id A286AF302A6; Thu, 23 Jan 2003 20:35:18 -0800 +Date: Thu, 23 Jan 2003 20:16:09 -0800 (PST) +From: Ron Mayer +X-X-Sender: ron@localhost.localdomain +To: pgsql-performance@postgresql.org +Cc: Ron Mayer +Subject: Does "correlation" mislead the optimizer on large tables? +In-Reply-To: <10520.200.225.202.15.1043353863.squirrel@webmail.ad2.com.br> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/275 +X-Sequence-Number: 922 + + +Short summary: + + On a large tables, I think the "correlation" pg_stats field as calculated + by "vacuum analyze" or "analyze" can mislead the optimizer. + + By forcing index scans on some queries shown below, some queries + in my database speed up from 197 seconds to under 30 seconds. + + I'd like feedback on whether or not having a smarter "analyze" + function (which I think I could write as a separate utility) would + help me situations like this. + +Longer: + + In particular, if I have a large table t with columns 'a','b','c', etc, + and I cluster the table as follows: + + create table t_ordered as select * from t order by a,b; + vacuum analyze t_ordered; + + Column "b" will (correctly) get a very low "correlation" in + the pg_stats table -- but I think the optimizer would do better + assuming a high correlation because similar 'b' values are still + grouped closely on the same disk pages. + + + + Below is a real-world example of this issue. + + The table "fact" is a large one (reltuples = 1e8, relpages = 1082385) + and contains about 1 years worth of data. The data was loaded + sequentialy (ordered by dat,tim). + + logs=# \d fact; + Table "fact" + Column | Type | Modifiers + --------+------------------------+----------- + dat | date | + tim | time without time zone | + ip_id | integer | + bid_id | integer | + req_id | integer | + ref_id | integer | + uag_id | integer | + Indexes: i_fact_2__bid_id, + i_fact_2__dat, + i_fact_2__tim, + i_fact_2__ip_id, + i_fact_2__ref_id, + i_fact_2__req_id + + + With a table this large, each day's worth of data contains + about 3000 pages; or conversely, each page contains only about + a 30 second range of values for "tim". + + As shown in the queries below, the optimizer wanted to do + a sequential scan when looking at a 10 minute part of the day. + However also as shown, forcing an index scan did much better. + + I'm guessing this happened because the optimizer saw the + horrible correlation, and decided it would have to read + an enormous number of pages if it did an index scan. + +=========================================== + +logs=# select tablename,attname,n_distinct,correlation from pg_stats where tablename='fact'; + tablename | attname | n_distinct | correlation +-----------+---------+------------+------------- + fact | dat | 365 | 1 + fact | tim | 80989 | -0.00281447 + fact | ip_id | 44996 | 0.660689 + fact | bid_id | 742850 | 0.969026 + fact | req_id | 2778 | 0.67896 + fact | ref_id | 595 | 0.258023 + fact | uag_id | 633 | 0.234216 +(7 rows) + + +logs=# explain analyze select * from fact where tim<'00:10:00'; + QUERY PLAN +------------------------------------------------------------------------------------------------------------------ + Seq Scan on fact (cost=0.00..1949838.40 rows=526340 width=32) (actual time=0.39..197447.50 rows=402929 loops=1) + Filter: (tim < '00:10:00'::time without time zone) + Total runtime: 197810.01 msec +(3 rows) + +logs=# explain analyze select * from fact where tim<'00:10:00'; + QUERY PLAN +------------------------------------------------------------------------------------------------------------------- + Seq Scan on fact (cost=0.00..1949838.40 rows=526340 width=32) (actual time=15.25..156705.76 rows=402929 loops=1) + Filter: (tim < '00:10:00'::time without time zone) + Total runtime: 157089.15 msec +(3 rows) + +logs=# set enable_seqscan = off; +SET +logs=# explain analyze select * from fact where tim<'00:10:00'; + QUERY PLAN +---------------------------------------------------------------------------------------------------------------------------------------- + Index Scan using i__fact__tim on fact (cost=0.00..2110978.39 rows=526340 width=32) (actual time=104.41..23307.84 rows=402929 loops=1) + Index Cond: (tim < '00:10:00'::time without time zone) + Total runtime: 23660.95 msec +(3 rows) + +logs=# explain analyze select * from fact where tim<'00:10:00'; + QUERY PLAN +------------------------------------------------------------------------------------------------------------------------------------- + Index Scan using i__fact__tim on fact (cost=0.00..2110978.39 rows=526340 width=32) (actual time=0.03..1477.35 rows=402929 loops=1) + Index Cond: (tim < '00:10:00'::time without time zone) + Total runtime: 1827.94 msec +(3 rows) + + + +logs=# + +******************************************************************************* +******************************************************************************* + + +So two questions: + + a) Am I on to something.... or is something else the reason why + the optimizer chose the much slower sequential scan? + + b) If I did write an "analyze" that tried to set "correlation" values + that took into account such local grouping of data, would anyone + be interested? + + + Ron + + + + + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 02:08:59 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2488847609C + for ; + Fri, 24 Jan 2003 02:08:57 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 0967647669A + for ; + Fri, 24 Jan 2003 01:29:37 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0O6Ta5u010920; + Fri, 24 Jan 2003 01:29:36 -0500 (EST) +To: Noah Silverman +Cc: pgsql-performance@postgresql.org +Subject: Re: Crash Recovery +In-reply-to: <2147483647.1043361178@[10.0.1.133]> +References: <2147483647.1043361178@[10.0.1.133]> +Comments: In-reply-to Noah Silverman + message dated "Thu, 23 Jan 2003 22:32:58 -0500" +Date: Fri, 24 Jan 2003 01:29:35 -0500 +Message-ID: <10919.1043389775@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/276 +X-Sequence-Number: 923 + +Noah Silverman writes: +> I'm curious about where I can find documentation about crash recovery in +> postgres. In mysql, there is a nice table recovery utility (myisamchk). +> is there something similar in postgres? + +There are no automated recovery tools for Postgres, because there are +no known failure modes that are systematic enough to allow automatic +recovery. We prefer to fix such bugs rather than patch around them. + +There are some last-ditch tools for reconstructing indexes (REINDEX) +and for throwing away the WAL log (pg_resetxlog) but I have not seen +any recent cases where I would have felt that blind invocation of either +would be a good move. + +> What do we do if a table or +> database becomes corrupted? (I'm aware of backup techniques, but it isn't +> feasible for some of our larger tables. + +Reconsider that. If your data center burns down tonight, what is your +fallback? Ultimately, you *must* have a backup copy, or you're just not +taking the possibility of failure seriously. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 02:35:52 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 691804769C8 + for ; + Fri, 24 Jan 2003 02:35:50 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 75741477248 + for ; + Fri, 24 Jan 2003 01:48:20 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0O6mJ5u011026; + Fri, 24 Jan 2003 01:48:19 -0500 (EST) +To: Ron Mayer +Cc: pgsql-performance@postgresql.org +Subject: Re: Does "correlation" mislead the optimizer on large tables? +In-reply-to: +References: +Comments: In-reply-to Ron Mayer + message dated "Thu, 23 Jan 2003 20:16:09 -0800" +Date: Fri, 24 Jan 2003 01:48:19 -0500 +Message-ID: <11025.1043390899@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/277 +X-Sequence-Number: 924 + +Ron Mayer writes: +> On a large tables, I think the "correlation" pg_stats field as calculated +> by "vacuum analyze" or "analyze" can mislead the optimizer. + +If you look in the pghackers archives, you will find some discussion +about changing the equation that cost_index() uses to estimate the +impact of correlation on indexscan cost. The existing equation is +ad-hoc and surely wrong, but so far no one's proposed a replacement +that can be justified any better. If you've got such a replacement +then we're all ears... + +> In particular, if I have a large table t with columns 'a','b','c', etc, +> and I cluster the table as follows: +> create table t_ordered as select * from t order by a,b; +> vacuum analyze t_ordered; +> Column "b" will (correctly) get a very low "correlation" in +> the pg_stats table -- but I think the optimizer would do better +> assuming a high correlation because similar 'b' values are still +> grouped closely on the same disk pages. + +How would that be? They'll be separated by the stride of 'a'. + +It seems likely to me that a one-dimensional correlation statistic may +be inadequate, but I haven't seen any proposals for better stats. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 08:22:20 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 96020475EDF + for ; + Fri, 24 Jan 2003 08:22:16 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 0A338475D87 + for ; + Fri, 24 Jan 2003 08:22:16 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18c3ml-0007Dz-00 + for ; Fri, 24 Jan 2003 08:22:19 -0500 +Date: Fri, 24 Jan 2003 08:22:19 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: Crash Recovery +Message-ID: <20030124082219.B26558@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <2147483647.1043361178@[10.0.1.133]> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <2147483647.1043361178@[10.0.1.133]>; + from noah@allresearch.com on Thu, Jan 23, 2003 at 10:32:58PM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/278 +X-Sequence-Number: 925 + +On Thu, Jan 23, 2003 at 10:32:58PM -0500, Noah Silverman wrote: +> To preface my question, we are still in the process of evaluating postgres +> to determine if we want to switch our production environment over. +> +> I'm curious about where I can find documentation about crash recovery in +> postgres. In mysql, there is a nice table recovery utility (myisamchk). + +It recovers automatically. Make sure you run with fsync turned on. +That calls fsync on the WAL at the point of every COMMIT, and COMMIT +isn't finished before the fsync returns. Then, in case of a crash, +the WAL just plays back and fixes up the data area. + +> is there something similar in postgres? What do we do if a table or +> database becomes corrupted? (I'm aware of backup techniques, but it isn't + +I have never had a table become corrupted under Postgres. There have +been some recent cases where people's bad hardware caused bad data to +make it into a table. Postgres's error reporting usually saves you +there, because you can go in and stomp on the bad tuple if need be. +There are some utilities to help in this; one of them, from Red Hat, +allows you to look at the binary data in various formats (it's pretty +slick). I believe it's available from sources.redhat.com/rhdb. + +> feasible for some of our larger tables. We're already running on raid 5, +> but can't do much more) + +I suspect you can. First, are you using ECC memory in your +production machines? If not, start doing so. Now. It is _the most +important_ thing, aside from RAID, that you can do to protect your +data. Almost every problem of inconsistency I've seen on the lists +in the past year and a bit has been to do with bad hardware -- +usually memory or disk controllers. (BTW, redundant disk +controllers, and ones with some intelligence built in so that they +check themsleves, are also mighty valuable here. But memory goes bad +way more often.) + +Also, I'm not sure just what you mean about backups "not being +feasible" for some of the larger tables, but you need to back up +daily. Since pg_dump takes a consistent snapshot, there's no data +inconsistency trouble, and you can just start the backup and go away. +If the resulting files are too large, use split. And if the problem +is space, well, disk is cheap these days, and so is tape, compared to +having to re-get the data you lost. + +A +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 08:53:02 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C178547632B + for ; + Fri, 24 Jan 2003 08:52:59 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 112704762E3 + for ; + Fri, 24 Jan 2003 08:52:59 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030124135303.BQWH8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Fri, 24 Jan 2003 08:53:03 -0500 +Subject: Re: Crash Recovery +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <2147483647.1043361178@[10.0.1.133]> +References: <2147483647.1043361178@[10.0.1.133]> +Content-Type: text/plain +Organization: +Message-Id: <1043416377.29437.70.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 24 Jan 2003 07:52:57 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/279 +X-Sequence-Number: 926 + +On Thu, 2003-01-23 at 21:32, Noah Silverman wrote: +> To preface my question, we are still in the process of evaluating postgres +> to determine if we want to switch our production environment over. +> +> I'm curious about where I can find documentation about crash recovery in +> postgres. In mysql, there is a nice table recovery utility (myisamchk). +> is there something similar in postgres? What do we do if a table or +> database becomes corrupted? (I'm aware of backup techniques, but it isn't +> feasible for some of our larger tables. We're already running on raid 5, +> but can't do much more) + +Of course it's feasible!! If corporations can backup terrabyte-sized +databases, then you can backup your comparatively puny DB. + +In fact, if your data is vital to your company, you *must* back it +up. Otherwise, poof goes the company if the computer is destroyed. + +Now, it might cost some bucks to buy a tape drive, or a multi-loader, +if you have *lots* of data, but it *can* be done... + +Btw, what happens if an obscure bug in the RAID controller shows is +head, and starts corrupting your data? A table recovery utility +wouldn't do squat, then... + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 09:12:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 61376475C8B + for ; + Fri, 24 Jan 2003 09:12:16 -0500 (EST) +Received: from lakemtao02.cox.net (lakemtao02.cox.net [68.1.17.243]) + by postgresql.org (Postfix) with ESMTP id A8A01475B8E + for ; + Fri, 24 Jan 2003 09:12:15 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao02.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030124141219.END6744.lakemtao02.cox.net@[192.168.1.1]> + for ; + Fri, 24 Jan 2003 09:12:19 -0500 +Subject: Crash Recovery, pt 2 +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <20030124082219.B26558@mail.libertyrms.com> +References: <2147483647.1043361178@[10.0.1.133]> + <20030124082219.B26558@mail.libertyrms.com> +Content-Type: text/plain +Organization: +Message-Id: <1043417539.29437.82.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 24 Jan 2003 08:12:19 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/280 +X-Sequence-Number: 927 + +On Fri, 2003-01-24 at 07:22, Andrew Sullivan wrote: +> On Thu, Jan 23, 2003 at 10:32:58PM -0500, Noah Silverman wrote: +> > To preface my question, we are still in the process of evaluating postgres +> > to determine if we want to switch our production environment over. +> > +> > I'm curious about where I can find documentation about crash recovery in +> > postgres. In mysql, there is a nice table recovery utility (myisamchk). +> +> It recovers automatically. Make sure you run with fsync turned on. +> That calls fsync on the WAL at the point of every COMMIT, and COMMIT +> isn't finished before the fsync returns. Then, in case of a crash, +> the WAL just plays back and fixes up the data area. + +On commercial databases, there's a command to flush the roll-forward +logs to tape at intervals during the day. + +Thus, if the disk(s) get corrupted, one can restore the database to +new disks, then apply the on-tape roll-forward logs to the database, +and you'd have only lost a few hours of data, instead of however +many hours (or days) it's been since the last database backup. + +Also, flushing them to tape (or a different partition) ensures that +they don't fill up the partition during a particularly intensive +batch job. + +Are there any FM's that explain how this works in Postgres? + +Thanks, +Ron +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 10:26:33 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9AD824766DF + for ; + Fri, 24 Jan 2003 10:26:32 -0500 (EST) +Received: from VL-MS-MR002.sc1.videotron.ca (relais.videotron.ca + [24.201.245.36]) + by postgresql.org (Postfix) with ESMTP id 85311477182 + for ; + Fri, 24 Jan 2003 10:17:54 -0500 (EST) +Received: from mochima.com ([66.131.15.233]) by VL-MS-MR002.sc1.videotron.ca + (iPlanet Messaging Server 5.2 HotFix 0.9 (built Jul 29 2002)) + with ESMTP id <0H98008GU55V58@VL-MS-MR002.sc1.videotron.ca> for + pgsql-performance@postgresql.org; Fri, 24 Jan 2003 10:17:55 -0500 (EST) +Date: Fri, 24 Jan 2003 10:16:42 -0500 +From: Carlos Moreno +Subject: Having trouble with backups (was: Re: Crash Recovery) +Cc: PgSQL Performance ML +Message-id: <3E3158DA.7080807@mochima.com> +MIME-version: 1.0 +Content-type: text/plain; charset=us-ascii; format=flowed +Content-transfer-encoding: 7BIT +X-Accept-Language: en-us +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:0.9.4.1) + Gecko/20020508 Netscape6/6.2.3 +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/281 +X-Sequence-Number: 928 + + +Speaking about daily backups... We are running into some serious +trouble with our backup policy. + +First (and less important), the size of our backups is increasing +a lot; yet information is not changing, only being added; so, the +obvious question: is there a way to make incremental backup? + +And the second (and intriguing) problem: whenever I run pg_dump, +my system *freezes* until pg_dump finishes. When I say "system", +I mean the software that is running and sending data to the PG +database. It just freezes, users are unable to connect during +several minutes, and the ones already connected think the server +died, so they end up disconnecting after one or two minutes +seeing that the server does not respond. + +Is this normal? Is there any way to avoid it? (I guess if I +have a solution to the first problem -- i.e., doing incremental +backups -- then that would solve this one, since it would only +"freeze" the system for a few seconds, which wouldn't be that +bad...) + +Thanks for any comments! + +Carlos +-- + + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 11:07:56 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 75BB247730F + for ; + Fri, 24 Jan 2003 11:07:55 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id A1C224758FE + for ; + Fri, 24 Jan 2003 10:48:29 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18c64I-0001GX-00 + for ; Fri, 24 Jan 2003 10:48:34 -0500 +Date: Fri, 24 Jan 2003 10:48:34 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: Crash Recovery, pt 2 +Message-ID: <20030124104834.B32645@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <2147483647.1043361178@[10.0.1.133]> + <20030124082219.B26558@mail.libertyrms.com> + <1043417539.29437.82.camel@haggis> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <1043417539.29437.82.camel@haggis>; + from ron.l.johnson@cox.net on Fri, Jan 24, 2003 at 08:12:19AM + -0600 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/282 +X-Sequence-Number: 929 + +On Fri, Jan 24, 2003 at 08:12:19AM -0600, Ron Johnson wrote: + +> On commercial databases, there's a command to flush the roll-forward +> logs to tape at intervals during the day. + +[. . .] + +> Are there any FM's that explain how this works in Postgres? + +Not yet, because you can't do it. + +There is, I understand, some code currently being included in 7.4 to +do this. So that's when it'll happen. Look for "point in time +recovery" or "PITR" on the -hackers list to see the progress. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 11:31:48 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id ED299475BC3 + for ; + Fri, 24 Jan 2003 11:31:47 -0500 (EST) +Received: from jester.senspire.com + (CPE00508b028d7d-CM00803785c5e0.cpe.net.cable.rogers.com + [24.103.51.175]) + by postgresql.org (Postfix) with ESMTP id 8959147705C + for ; + Fri, 24 Jan 2003 11:08:47 -0500 (EST) +Received: from [127.0.0.1] (localhost [127.0.0.1]) + by jester.senspire.com (8.12.6/8.12.6) with ESMTP id h0OG8tBt065380; + Fri, 24 Jan 2003 11:08:57 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +From: Rod Taylor +To: Carlos Moreno +Cc: PgSQL Performance ML +In-Reply-To: <3E3158DA.7080807@mochima.com> +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> <3E3158DA.7080807@mochima.com> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-1pw3W80GWt4Hc/tZSe3s" +Organization: +Message-Id: <1043424535.58142.65.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 24 Jan 2003 11:08:55 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/283 +X-Sequence-Number: 930 + +--=-1pw3W80GWt4Hc/tZSe3s +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +On Fri, 2003-01-24 at 10:16, Carlos Moreno wrote: +> Speaking about daily backups... We are running into some serious +> trouble with our backup policy. +>=20 +> First (and less important), the size of our backups is increasing +> a lot; yet information is not changing, only being added; so, the +> obvious question: is there a way to make incremental backup? + +Incremental backups are coming. Some folks at RedHat are working on +finishing a PIT implementation, with with any luck 7.4 will do what you +want. + +For the time being you might be able to cheat. If you're not touching +the old data, it should come out in roughly the same order every time. + +You might be able to get away with doing a diff between the new backup +and an older one, and simply store that. When restoring, you'll need to +patch together the proper restore file. + +> And the second (and intriguing) problem: whenever I run pg_dump, +> my system *freezes* until pg_dump finishes. When I say "system", + +No, this isn't normal -- nor do I believe it. The only explanation would +be a hardware or operating system limitation. I.e. with heavy disk usage +it used to be possible to peg the CPU -- making everything else CPU +starved, but the advent of DMA drives put an end to that. + +A pg_dump is not resource friendly, simply due to the quantity of +information its dealing with. Are you dumping across a network? Perhaps +the NIC is maxed out. + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-1pw3W80GWt4Hc/tZSe3s +Content-Type: application/pgp-signature; name=signature.asc +Content-Description: This is a digitally signed message part + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (FreeBSD) + +iD8DBQA+MWUW6DETLow6vwwRAiAfAJ4vg1s0uo3+KL78kLgrTUFWPxcQagCfXGZO +AaCChZInF1yJD0GA5c8l/Jw= +=Gujt +-----END PGP SIGNATURE----- + +--=-1pw3W80GWt4Hc/tZSe3s-- + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 11:32:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 62BD5476FAF + for ; + Fri, 24 Jan 2003 11:32:16 -0500 (EST) +Received: from smtp3.ihug.com.au (smtp3.ihug.com.au [203.109.250.76]) + by postgresql.org (Postfix) with ESMTP id 6165F4772E8 + for ; + Fri, 24 Jan 2003 11:09:04 -0500 (EST) +Received: from 203-30-124-221.cust.iweb.net.au (postgresql.org) + [203.30.124.221] + by smtp3.ihug.com.au with esmtp (Exim 3.22 #1 (Debian)) + id 18c6OA-0000re-00; Sat, 25 Jan 2003 03:09:07 +1100 +Message-ID: <3E31651C.9060306@postgresql.org> +Date: Sat, 25 Jan 2003 02:39:00 +1030 +From: Justin Clift +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; + rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Carlos Moreno +Cc: PgSQL Performance ML +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> <3E3158DA.7080807@mochima.com> +In-Reply-To: <3E3158DA.7080807@mochima.com> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/284 +X-Sequence-Number: 931 + +Carlos Moreno wrote: + +> And the second (and intriguing) problem: whenever I run pg_dump, +> my system *freezes* until pg_dump finishes. When I say "system", +> I mean the software that is running and sending data to the PG +> database. It just freezes, users are unable to connect during +> several minutes, and the ones already connected think the server +> died, so they end up disconnecting after one or two minutes +> seeing that the server does not respond. + +Is there any chance that you have hardware problems? For example a +couple of disk areas that are defective and the system is not happy +about, or maybe hard drive controller problems? + +With PC's, this sort of thing generally seems to mean hardware problems +of some sort that are being triggered by PostgreSQL having to run +through the entire dataset. Could be caused by I/O load, could be +caused by hard drive errors, etc. + +? + +> Is this normal? + +No. + +Out of curiosity, which operating system are you using? + +:-( + +Regards and best wishes, + +Justin Clift + + + > Is there any way to avoid it? (I guess if I +> have a solution to the first problem -- i.e., doing incremental +> backups -- then that would solve this one, since it would only +> "freeze" the system for a few seconds, which wouldn't be that +> bad...) +> +> Thanks for any comments! +> +> Carlos +> -- +> +> +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 6: Have you searched our list archives? +> +> http://archives.postgresql.org + + +-- +"My grandfather once told me that there are two kinds of people: those +who work and those who take the credit. He told me to try to be in the +first group; there was less competition there." +- Indira Gandhi + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 11:37:27 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C483F476F4A + for ; + Fri, 24 Jan 2003 11:37:25 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id C65784770E2 + for ; + Fri, 24 Jan 2003 11:13:28 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18c6ST-0001o8-00 + for ; Fri, 24 Jan 2003 11:13:33 -0500 +Date: Fri, 24 Jan 2003 11:13:33 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +Message-ID: <20030124111333.C32645@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> <3E3158DA.7080807@mochima.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <3E3158DA.7080807@mochima.com>; + from moreno@mochima.com on Fri, Jan 24, 2003 at 10:16:42AM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/285 +X-Sequence-Number: 932 + +On Fri, Jan 24, 2003 at 10:16:42AM -0500, Carlos Moreno wrote: +> obvious question: is there a way to make incremental backup? + +Not really, at the moment. Sorry. It's supposed to be coming soon +(see my other message about PITR). + +> my system *freezes* until pg_dump finishes. When I say "system", + +> Is this normal? Is there any way to avoid it? (I guess if I + +No, it's not normal. I think some additional digging is needed. + +One thing that is important is to make sure your pg_dump doesn't +cause swapping on the machine. Causing swapping is easy if you have +been too aggressive in shared-memory allocation for the postmaster, +and your OS is careless about who gets to be a candidate for paging. +(Solaris 7.1 without priority paging was subject to this problem, for +instance). + +A +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 11:50:21 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8F3F447630B + for ; + Fri, 24 Jan 2003 11:50:20 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 001C3477243 + for ; + Fri, 24 Jan 2003 11:26:58 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 92B6DD896; Fri, 24 Jan 2003 08:27:03 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 87EFA5C21; Fri, 24 Jan 2003 08:27:03 -0800 (PST) +Date: Fri, 24 Jan 2003 08:27:03 -0800 (PST) +From: Stephan Szabo +To: Tom Lane +Cc: Ron Mayer , + +Subject: Re: Does "correlation" mislead the optimizer on large +In-Reply-To: <11025.1043390899@sss.pgh.pa.us> +Message-ID: <20030124081405.W30842-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/286 +X-Sequence-Number: 933 + +On Fri, 24 Jan 2003, Tom Lane wrote: + +> Ron Mayer writes: +> > In particular, if I have a large table t with columns 'a','b','c', etc, +> > and I cluster the table as follows: +> > create table t_ordered as select * from t order by a,b; +> > vacuum analyze t_ordered; +> > Column "b" will (correctly) get a very low "correlation" in +> > the pg_stats table -- but I think the optimizer would do better +> > assuming a high correlation because similar 'b' values are still +> > grouped closely on the same disk pages. +> +> How would that be? They'll be separated by the stride of 'a'. + +I think it's a clumping effect. + +For example, I made a table (ordered) with 20 values of a, 50 values of b +(each showing up in each a) and 100 values of c (not used, just means 100 +rows for each (a,b) combination. It's got 541 pages it looks like. Analyze +sets the correlation to about 0.08 on the table and so a query like: +select * from test1 where b=1; prefers a sequence scan (1791 vs 2231) +while the index scan actually performs about 5 times better. + +I guess the reason is that in general, the index scan *really* is reading +something on the order of 40 pages rather than the much larger estimate +(I'd guess something on the order of say 300-400? I'm not sure how to +find that except by trying to reverse engineer the estimate number), +because pretty much each value of a will probably have 1 or 2 pages with +b=1. + +I'm not really sure how to measure that, however. + + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 14:26:57 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C41E6477182 + for ; + Fri, 24 Jan 2003 14:26:56 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 1937B4773A2 + for ; + Fri, 24 Jan 2003 13:46:50 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030124184651.ETFT8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Fri, 24 Jan 2003 13:46:51 -0500 +Subject: Re: Crash Recovery, pt 2 +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <20030124104834.B32645@mail.libertyrms.com> +References: <2147483647.1043361178@[10.0.1.133]> + <20030124082219.B26558@mail.libertyrms.com> + <1043417539.29437.82.camel@haggis> + <20030124104834.B32645@mail.libertyrms.com> +Content-Type: text/plain +Organization: +Message-Id: <1043434008.30882.8.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 24 Jan 2003 12:46:49 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/287 +X-Sequence-Number: 934 + +On Fri, 2003-01-24 at 09:48, Andrew Sullivan wrote: +> On Fri, Jan 24, 2003 at 08:12:19AM -0600, Ron Johnson wrote: +> +> > On commercial databases, there's a command to flush the roll-forward +> > logs to tape at intervals during the day. +> +> [. . .] +> +> > Are there any FM's that explain how this works in Postgres? +> +> Not yet, because you can't do it. +> +> There is, I understand, some code currently being included in 7.4 to +> do this. So that's when it'll happen. Look for "point in time +> recovery" or "PITR" on the -hackers list to see the progress. + +Great! That's a big step towards enterprise functiomality. + +Another big step would be aggregate functions using indexes, but +that's been discussed before... + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 14:57:12 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 32A6E477581 + for ; + Fri, 24 Jan 2003 14:57:10 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 2129E47731F + for ; + Fri, 24 Jan 2003 14:19:38 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2324561 for pgsql-performance@postgresql.org; + Fri, 24 Jan 2003 11:19:42 -0800 +Content-Type: text/plain; + charset="us-ascii" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: +Subject: Mount options for Ext3? +Date: Fri, 24 Jan 2003 11:20:14 -0800 +X-Mailer: KMail [version 1.4] +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301241120.14404.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/288 +X-Sequence-Number: 935 + +Folks, + +What mount options to people use for Ext3, particularly what do you set "da= +ta=20 +=3D " for a high-transaction database? I'm used to ReiserFS ("noatime,=20 +notail") and am not really sure where to go with Ext3. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 15:10:11 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B907E4773E1 + for ; + Fri, 24 Jan 2003 15:10:10 -0500 (EST) +Received: from torque.intervideoinc.com (mail.intervideo.com + [206.112.112.151]) + by postgresql.org (Postfix) with ESMTP id 2045F477400 + for ; + Fri, 24 Jan 2003 14:36:42 -0500 (EST) +Received: from antares.intervideo.com [206.112.112.139] by + torque.intervideoinc.com with ESMTP + (SMTPD32-5.05) id AA48157B029A; Fri, 24 Jan 2003 11:55:52 -0800 +Date: Fri, 24 Jan 2003 11:36:50 -0800 (PST) +From: Ron Mayer +X-X-Sender: ron@localhost.localdomain +To: Tom Lane +Cc: pgsql-performance@postgresql.org +Subject: Re: Does "correlation" mislead the optimizer on large +In-Reply-To: <11025.1043390899@sss.pgh.pa.us> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/289 +X-Sequence-Number: 936 + + +On Fri, 24 Jan 2003, Tom Lane wrote: +> +> Ron Mayer writes: +> > On a large tables, I think the "correlation" pg_stats field as calculated +> > by "vacuum analyze" or "analyze" can mislead the optimizer. +> +> If you look in the pghackers archives, you will find some discussion +> about changing the equation that cost_index() uses to estimate the +> impact of correlation on indexscan cost. The existing equation is +> ad-hoc and surely wrong, but so far no one's proposed a replacement +> that can be justified any better. If you've got such a replacement +> then we're all ears... + +I've got a very slow one (full table scan perl script) that helps +my database... I don't know if it's a good general purpose solution. + +That's why I'm asking if the concept is good here. :-) + + +> > In particular, if I have a large table t with columns 'a','b','c', etc, +> > and I cluster the table as follows: +> > create table t_ordered as select * from t order by a,b; +> > vacuum analyze t_ordered; +> > Column "b" will (correctly) get a very low "correlation" in +> > the pg_stats table -- but I think the optimizer would do better +> > assuming a high correlation because similar 'b' values are still +> > grouped closely on the same disk pages. +> +> How would that be? They'll be separated by the stride of 'a'. + + +In the case of date/time (for the queries I showed) the issue was +that 'a's were not at all unique so I had data like this: + + dat | time | value + ------------|----------|-------------------------------- + 2002-01-01 | 00:00:00 | whatever + 2002-01-01 | 00:00:00 | + 2002-01-01 | 00:00:00 | + 2002-01-01 | 00:00:01 | + 2002-01-01 | 00:00:01 | [many pages of 12am] + 2002-01-01 | 00:00:01 | + 2002-01-01 | 00:00:01 | + ... thousands more rows.... + 2002-01-01 | 00:00:59 | + 2002-01-01 | 00:01:00 | [many pages of 1am] + ... tens of thousands of rows. + 2002-01-01 | 23:59:59 | + 2002-01-01 | 23:59:59 | + 2002-01-01 | 23:59:59 | [many pages of 11pm] + 2002-01-02 | 00:00:00 | [many *MORE* pages of 12am] + 2002-01-02 | 00:00:00 | + 2002-01-02 | 00:00:00 | + ... tens of thousands of rows... + 2002-01-02 | 23:59:59 | [many pages of 11pm] + 2002-01-03 | 00:00:00 | [many *MORE* pages of 12am] + ... millions more rows ... + + +A similar problem actually shows up again in the dimention tables +of my database; where I bulk load many pages at a time (which can +easily be ordered to give a good correlation for a single load) ... +but then the next week's data gets appended to the end. + + id | value + ------|---------------------------------- + 1 | aalok mehta [many pages of all 'a's] + 2 | aamir khan + 3 | aaron beall + | [...] + 6234 | axel rose + 6234 | austin wolf + 6123 | barbara boxer [many pages of all 'b's] + | [...] + 123456 | young + 123457 | zebra + | [...data loaded later..] + 123458 | aaron whatever [more pages of all 'a's] + 123458 | aaron something else + 123458 | aaron something else + | [...] + 512344 | zelany + + +In this case I get many clustered blocks of "a" values, but these +clustered blocks happen at many different times across the table. + + +> It seems likely to me that a one-dimensional correlation statistic may +> be inadequate, but I haven't seen any proposals for better stats. + +The idea is it walks the whole table and looks for more local +correlations and replaces the correlation value with a "good" +value if values "close" to each other on the disk are similar. + +This way a single "correlation" value still works ... so I didn't +have to change the optimizer logic, just the "analyze" logic. + + +Basically if data within each block is highly correlated, it doesn't +matter as much (yeah, I now the issue about sequential reads vs. random +reads). + + + Ron + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 15:41:43 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4E689477310 + for ; + Fri, 24 Jan 2003 15:41:42 -0500 (EST) +Received: from torque.intervideoinc.com (mail.intervideo.com + [206.112.112.151]) + by postgresql.org (Postfix) with ESMTP id CC3314773C0 + for ; + Fri, 24 Jan 2003 15:04:05 -0500 (EST) +Received: from antares.intervideo.com [206.112.112.139] by + torque.intervideoinc.com with ESMTP + (SMTPD32-5.05) id A0B3221701C2; Fri, 24 Jan 2003 12:23:15 -0800 +Date: Fri, 24 Jan 2003 12:04:12 -0800 (PST) +From: Ron Mayer +X-X-Sender: ron@localhost.localdomain +To: Stephan Szabo +Cc: Tom Lane , +Subject: Re: Does "correlation" mislead the optimizer on large +In-Reply-To: <20030124081405.W30842-100000@megazone23.bigpanda.com> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/290 +X-Sequence-Number: 937 + + +On Fri, 24 Jan 2003, Stephan Szabo wrote: +> +> I think it's a clumping effect. + + +Yup, I think that's exactly the effect. + +A proposal.... (yes I I'm volunteering if people point me in the right +direction)... would be to have a "plugable" set of analyze functions so that a +huge database that runs analyze infrequently could choose to have a very slow +analyze that might work better for it's data. + +I see no reason different analyze functions would to be compiled into +the source code ... but could probably exists as PL/pgSQL languages. + +The one thing compiling it in would help with is to let me know +the exact number of tuples on each individual page, but I guess +reltuples/relpages from pg_class is a good estimate. + + +> For example, I made a table (ordered) with 20 values of a, 50 values of b +> (each showing up in each a) and 100 values of c (not used, just means 100 +> rows for each (a,b) combination. It's got 541 pages it looks like. Analyze +> sets the correlation to about 0.08 on the table and so a query like: +> select * from test1 where b=1; prefers a sequence scan (1791 vs 2231) +> while the index scan actually performs about 5 times better. + +That sounds like the same situation I was in. If my logic is right, this +means you had about 184 tuples/page (200*50*100/541), so it looks to me +like for each "a", you get half-a-page where "b=1". + +If you had 'c' have 200 values, I think you'd get even a bigger speedup +because half the page is still "wasted" with b=2 values. + +If you had 'c' have 10000 values, I think you'd get even a slightly bigger +speedup because you'd have so many b=1 pages next to each other you'd +benefit from more sequential disk access. + + +> I guess the reason is that in general, the index scan *really* is reading +> something on the order of 40 pages rather than the much larger estimate +> (I'd guess something on the order of say 300-400? I'm not sure how to +> find that except by trying to reverse engineer the estimate number), + +Or by adding a printf()... I think it'd be in cost_index in costsize.c. + +> because pretty much each value of a will probably have 1 or 2 pages with +> b=1. +> +> I'm not really sure how to measure that, however. + + +As I said... I'm happy to volunteer and experiment if people point +me in a good direction. + + Ron + + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 16:02:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 315F7477198 + for ; + Fri, 24 Jan 2003 16:02:16 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 5F894476B41 + for ; + Fri, 24 Jan 2003 15:22:27 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0OKML5u021094; + Fri, 24 Jan 2003 15:22:21 -0500 (EST) +To: Ron Mayer +Cc: Stephan Szabo , + pgsql-performance@postgresql.org +Subject: Re: Does "correlation" mislead the optimizer on large +In-reply-to: +References: +Comments: In-reply-to Ron Mayer + message dated "Fri, 24 Jan 2003 12:04:12 -0800" +Date: Fri, 24 Jan 2003 15:22:21 -0500 +Message-ID: <21093.1043439741@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/291 +X-Sequence-Number: 938 + +Ron Mayer writes: +> A proposal.... (yes I I'm volunteering if people point me in the right +> direction)... would be to have a "plugable" set of analyze functions so that a +> huge database that runs analyze infrequently could choose to have a very slow +> analyze that might work better for it's data. + +I do not think ANALYZE is the problem here; at least, it's premature to +worry about that end of things until you've defined (a) what's to be +stored in pg_statistic, and (b) what computation the planner needs to +make to derive a cost estimate given the stats. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 16:27:57 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EE0CF475EE2 + for ; + Fri, 24 Jan 2003 16:27:56 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 20339476027 + for ; + Fri, 24 Jan 2003 16:01:42 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0OL1f5u022651; + Fri, 24 Jan 2003 16:01:42 -0500 (EST) +To: Carlos Moreno +Cc: PgSQL Performance ML +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +In-reply-to: <3E3158DA.7080807@mochima.com> +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> <3E3158DA.7080807@mochima.com> +Comments: In-reply-to Carlos Moreno + message dated "Fri, 24 Jan 2003 10:16:42 -0500" +Date: Fri, 24 Jan 2003 16:01:41 -0500 +Message-ID: <22650.1043442101@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/292 +X-Sequence-Number: 939 + +Carlos Moreno writes: +> And the second (and intriguing) problem: whenever I run pg_dump, +> my system *freezes* until pg_dump finishes. When I say "system", +> I mean the software that is running and sending data to the PG +> database. + +Other people have responded on the assumption that this is a performance +problem, but you should also consider the possibility that it's bad +coding of your application software. Does your app try to grab +exclusive table locks? If so, it'll sit there waiting for the pg_dump +to complete. pg_dump only takes ACCESS SHARE lock on the tables it's +working on, which is the weakest type of lock and does not conflict with +most database operations ... but it does conflict with ACCESS EXCLUSIVE +lock requests. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 17:21:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BE965476030 + for ; + Fri, 24 Jan 2003 17:21:06 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 940174773C0 + for ; + Fri, 24 Jan 2003 16:55:44 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP id 4FF653C1D1 + for ; + Fri, 24 Jan 2003 16:55:46 -0500 (EST) +Date: Fri, 24 Jan 2003 16:55:45 -0500 +Subject: Re: Does "correlation" mislead the optimizer on large +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: pgsql-performance@postgresql.org +To: pgsql-performance@postgresql.org +From: Noah Silverman +In-Reply-To: <21093.1043439741@sss.pgh.pa.us> +Message-Id: <975BA89C-2FE6-11D7-A3A3-000393AA8F3C@allresearch.com> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/293 +X-Sequence-Number: 940 + +Hi! + +Another fun question in our ongoing analysis on whether to switch from +mysql to postgres. (Just as an update, Postgres has performed +flawlessly on all of our stress tests so far.) + +We have a situation where we will be creating two fairly large and +complex databases with many tables (thousands) each. From what I +understand, postgres keeps everything in one big data directory. + +Would there be an advantage to putting each of the two databases into a +separate directory and starting two instances of postgres? Is it +better to just lump everything together. + +In a perfect world, we would buy another database server and raid for +the second database, but being a small company, we just don't have the +budget right now. The raid on our current server is much bigger than we +need. + +Thanks, + +-N + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 18:06:37 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1C67E475E3E + for ; + Fri, 24 Jan 2003 18:06:37 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 86E23476160 + for ; + Fri, 24 Jan 2003 17:39:40 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP id B329E2D3D5 + for ; + Fri, 24 Jan 2003 17:39:42 -0500 (EST) +Date: Fri, 24 Jan 2003 17:39:42 -0500 +Subject: Multiple databases one directory +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +From: Noah Silverman +To: pgsql-performance@postgresql.org +Content-Transfer-Encoding: 7bit +In-Reply-To: <975BA89C-2FE6-11D7-A3A3-000393AA8F3C@allresearch.com> +Message-Id: +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/294 +X-Sequence-Number: 941 + +Hi! + +Another fun question in our ongoing analysis on whether to switch from +mysql to postgres. (Just as an update, Postgres has performed +flawlessly on all of our stress tests so far.) + +We have a situation where we will be creating two fairly large and +complex databases with many tables (thousands) each. From what I +understand, postgres keeps everything in one big data directory. + +Would there be an advantage to putting each of the two databases into a +separate directory and starting two instances of postgres? Is it +better to just lump everything together. + +In a perfect world, we would buy another database server and raid for +the second database, but being a small company, we just don't have the +budget right now. The raid on our current server is much bigger than we +need. + +Thanks, + +-N + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 18:23:02 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 45F5F476F55 + for ; + Fri, 24 Jan 2003 18:23:01 -0500 (EST) +Received: from torque.intervideoinc.com (mail.intervideo.com + [206.112.112.151]) + by postgresql.org (Postfix) with ESMTP id C350C476A6D + for ; + Fri, 24 Jan 2003 18:09:08 -0500 (EST) +Received: from antares.intervideo.com [206.112.112.139] by + torque.intervideoinc.com with ESMTP + (SMTPD32-5.05) id AC1414EB01B0; Fri, 24 Jan 2003 15:28:20 -0800 +Date: Fri, 24 Jan 2003 15:09:19 -0800 (PST) +From: Ron Mayer +X-X-Sender: ron@localhost.localdomain +To: Tom Lane +Cc: Stephan Szabo , + +Subject: Re: Does "correlation" mislead the optimizer on large +In-Reply-To: <21093.1043439741@sss.pgh.pa.us> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/295 +X-Sequence-Number: 942 + + +On Fri, 24 Jan 2003, Tom Lane wrote: +> +> Ron Mayer writes: +> > A proposal.... (yes I I'm volunteering if people point me in the right +> > direction)... +> +> I do not think ANALYZE is the problem here; at least, it's premature to +> worry about that end of things until you've defined (a) what's to be +> stored in pg_statistic, and (b) what computation the planner needs to +> make to derive a cost estimate given the stats. + +Cool. Thanks for a good starting point. If I wanted to brainstorm +further, should I do so here, or should I encourage interested people +to take it off line with me (ron@intervideo.com) and I can post +a summary of the conversation? + + Ron + +For those who do want to brainstorm with me, my starting point is this: + + With my particular table, I think the main issue is still that I have a + lot of data that looks like: + + values: aaaaaaaaaaabbbbbbbbccccccccddddddddddaaaabbbbbbbccccccccddddd... + disk page: |page 1|page 2|page 3|page 4|page 5|page 6|page 7|page 8|page 9| + + The problem I'm trying to address is that the current planner guesses + that most of the pages will need to be read; however the local clustering + means that in fact only a small subset need to be accessed. My first + guess is that modifying the definition of "correlation" to account for + page-sizes would be a good approach. + + I.e. Instead of the correlation across the whole table, for each row + perform an auto-correlation + (http://astronomy.swin.edu.au/~pbourke/analysis/correlate/) + and keep only the values with a "delay" of less than 1 page-size. + +If you want to share thoughts offline (ron@intervideo.com), I'll gladly +post a summary of responses here to save the bandwidth of the group. + + + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 18:28:39 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 59E1A476242 + for ; + Fri, 24 Jan 2003 18:28:38 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 2BB1A476246 + for ; + Fri, 24 Jan 2003 18:21:50 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2324884; Fri, 24 Jan 2003 15:21:56 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Noah Silverman , + pgsql-performance@postgresql.org +Subject: Re: Multiple databases one directory +Date: Fri, 24 Jan 2003 15:22:28 -0800 +X-Mailer: KMail [version 1.4] +References: +In-Reply-To: +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301241522.28521.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/296 +X-Sequence-Number: 943 + + +Noah, + +> Would there be an advantage to putting each of the two databases into a= +=20 +> separate directory and starting two instances of postgres? Is it=20 +> better to just lump everything together. + +You can use the WITH LOCATION option in CREATE DATABASE to put the two=20 +databases into seperate directories *without* running two instances of=20 +postgres. + +For that matter, the databases each have their own directories, by OID numb= +er. + +Of course, this only helps you if the seperate directories are on seperate= +=20 +disks/arrays/channels. If everying is on the same disk or array, don't=20 +bother. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 18:59:59 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3FF2347580B + for ; + Fri, 24 Jan 2003 18:59:56 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 06233475461 + for ; + Fri, 24 Jan 2003 18:59:56 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP + id E80FC3C1DE; Fri, 24 Jan 2003 18:59:58 -0500 (EST) +Date: Fri, 24 Jan 2003 18:59:58 -0500 +Subject: WEIRD CRASH?!?! +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: pgsql-performance@postgresql.org +To: josh@agliodbs.com +From: Noah Silverman +In-Reply-To: <200301241522.28521.josh@agliodbs.com> +Message-Id: +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/297 +X-Sequence-Number: 944 + +I think my server crashed and then restarted itself. Does anybody know +what all this means: + +2003-01-24 18:28:06 PANIC: link from +/RAID/pgsql/pg_xlog/00000009000000BC to +/RAID/pgsql/pg_xlog/00000009000000C4 (initialization of log file 9, +segment 196) failed: File exists +2003-01-24 18:28:06 LOG: server process (pid 1574) was terminated by +signal 6 +2003-01-24 18:28:06 LOG: terminating any other active server processes +2003-01-24 18:28:06 WARNING: Message from PostgreSQL backend: + The Postmaster has informed me that some other backend + died abnormally and possibly corrupted shared memory. + I have rolled back the current transaction and am + going to terminate your database system connection and exit. + Please reconnect to the database system and repeat your query. +2003-01-24 18:28:06 LOG: all server processes terminated; +reinitializing shared memory and semaphores +2003-01-24 18:28:06 LOG: database system was interrupted at 2003-01-24 +18:28:06 EST +2003-01-24 18:28:06 LOG: checkpoint record is at 9/C4574974 +2003-01-24 18:28:06 LOG: redo record is at 9/C200D144; undo record is +at 0/0; shutdown FALSE +2003-01-24 18:28:06 LOG: next transaction id: 5159292; next oid: +50856954 +2003-01-24 18:28:06 LOG: database system was not properly shut down; +automatic recovery in progress +2003-01-24 18:28:06 LOG: redo starts at 9/C200D144 +2003-01-24 18:28:13 LOG: ReadRecord: record with zero length at +9/C4578CC0 +2003-01-24 18:28:13 LOG: redo done at 9/C4578C9C +2003-01-24 18:29:02 LOG: recycled transaction log file 00000009000000C0 +2003-01-24 18:29:02 LOG: recycled transaction log file 00000009000000C1 +2003-01-24 18:29:02 LOG: recycled transaction log file 00000009000000BC +2003-01-24 18:29:02 LOG: recycled transaction log file 00000009000000BD +2003-01-24 18:29:02 LOG: recycled transaction log file 00000009000000BE +2003-01-24 18:29:02 LOG: recycled transaction log file 00000009000000BF +2003-01-24 18:29:02 LOG: database system is ready + + + + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 19:03:05 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id DAEFB475ADD + for ; + Fri, 24 Jan 2003 19:03:03 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 227B54758E6 + for ; + Fri, 24 Jan 2003 19:03:03 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2324930; Fri, 24 Jan 2003 16:03:09 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Noah Silverman +Subject: Re: WEIRD CRASH?!?! +Date: Fri, 24 Jan 2003 16:03:42 -0800 +X-Mailer: KMail [version 1.4] +Cc: pgsql-performance@postgresql.org +References: +In-Reply-To: +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301241603.42263.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/298 +X-Sequence-Number: 945 + +Noah, + +> I think my server crashed and then restarted itself. Does anybody know= +=20 +> what all this means: +>=20 +> 2003-01-24 18:28:06 PANIC: link from=20 +> /RAID/pgsql/pg_xlog/00000009000000BC to=20 +> /RAID/pgsql/pg_xlog/00000009000000C4 (initialization of log file 9,=20 +> segment 196) failed: File exists +> 2003-01-24 18:28:06 LOG: server process (pid 1574) was terminated by=20 +> signal 6 +> 2003-01-24 18:28:06 LOG: terminating any other active server processes +> 2003-01-24 18:28:06 WARNING: Message from PostgreSQL backend: +> The Postmaster has informed me that some other backend +> died abnormally and possibly corrupted shared memory. +> I have rolled back the current transaction and am +> going to terminate your database system connection and exit. +> Please reconnect to the database system and repeat your query. + +This means that somebody KILL -9'd a postgres process or the postmaster, an= +d=20 +Postgres restarted in order to clear the shared buffers. If the database= +=20 +started up again, you are fine. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 19:08:29 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8DF374758E6 + for ; + Fri, 24 Jan 2003 19:08:27 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 0B859475461 + for ; + Fri, 24 Jan 2003 19:08:27 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP + id 09CC335EAF; Fri, 24 Jan 2003 19:08:30 -0500 (EST) +Date: Fri, 24 Jan 2003 19:08:29 -0500 +Subject: Re: WEIRD CRASH?!?! +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: pgsql-performance@postgresql.org +To: josh@agliodbs.com +From: Noah Silverman +In-Reply-To: <200301241603.42263.josh@agliodbs.com> +Message-Id: <22021C37-2FF9-11D7-A3A3-000393AA8F3C@allresearch.com> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/299 +X-Sequence-Number: 946 + +Yes, +but I'm the only one logged into this box, and I didn't kill anything. +It appears to have died all by itself. + +Thanks, + +-N + + +On Friday, January 24, 2003, at 07:03 PM, Josh Berkus wrote: + +> Noah, +> +>> I think my server crashed and then restarted itself. Does anybody +>> know +>> what all this means: +>> +>> 2003-01-24 18:28:06 PANIC: link from +>> /RAID/pgsql/pg_xlog/00000009000000BC to +>> /RAID/pgsql/pg_xlog/00000009000000C4 (initialization of log file 9, +>> segment 196) failed: File exists +>> 2003-01-24 18:28:06 LOG: server process (pid 1574) was terminated by +>> signal 6 +>> 2003-01-24 18:28:06 LOG: terminating any other active server +>> processes +>> 2003-01-24 18:28:06 WARNING: Message from PostgreSQL backend: +>> The Postmaster has informed me that some other backend +>> died abnormally and possibly corrupted shared memory. +>> I have rolled back the current transaction and am +>> going to terminate your database system connection and exit. +>> Please reconnect to the database system and repeat your +>> query. +> +> This means that somebody KILL -9'd a postgres process or the +> postmaster, and +> Postgres restarted in order to clear the shared buffers. If the +> database +> started up again, you are fine. +> +> -- +> -Josh Berkus +> Aglio Database Solutions +> San Francisco +> +> + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 19:21:33 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8B2ED4763E6 + for ; + Fri, 24 Jan 2003 19:21:32 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id 39B4B476247 + for ; + Fri, 24 Jan 2003 19:19:28 -0500 (EST) +Received: from css120.ihs.com (css120.ihs.com [170.207.105.120]) + by mail1.ihs.com (8.12.6/8.12.6) with ESMTP id h0P0IAXv027326; + Fri, 24 Jan 2003 17:18:11 -0700 (MST) +Date: Fri, 24 Jan 2003 17:13:49 -0700 (MST) +From: "scott.marlowe" +To: Noah Silverman +Cc: , +Subject: Re: WEIRD CRASH?!?! +In-Reply-To: <22021C37-2FF9-11D7-A3A3-000393AA8F3C@allresearch.com> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-MailScanner: Found to be clean +X-MailScanner-SpamCheck: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/302 +X-Sequence-Number: 949 + +On Fri, 24 Jan 2003, Noah Silverman wrote: + +> Yes, +> but I'm the only one logged into this box, and I didn't kill anything. +> It appears to have died all by itself. +> + +It certainly sounds that way. Can you recreate the circumstances and make +it happen reliably? If not, the likely it's just an isolated occurance +and nothing to get too worried about. Your data is still coherent, that's +why all the backends were forced to reset, to cleanse the buffers from +possible corruption. + + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 19:14:47 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 38DC5475DDB + for ; + Fri, 24 Jan 2003 19:14:46 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 7D663475DBC + for ; + Fri, 24 Jan 2003 19:14:45 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2324959; Fri, 24 Jan 2003 16:14:52 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Noah Silverman +Subject: Re: WEIRD CRASH?!?! +Date: Fri, 24 Jan 2003 16:15:24 -0800 +X-Mailer: KMail [version 1.4] +Cc: pgsql-performance@postgresql.org +References: <22021C37-2FF9-11D7-A3A3-000393AA8F3C@allresearch.com> +In-Reply-To: <22021C37-2FF9-11D7-A3A3-000393AA8F3C@allresearch.com> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301241615.24767.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/300 +X-Sequence-Number: 947 + + +Noah, + +> but I'm the only one logged into this box, and I didn't kill anything.=20= +=20 +> It appears to have died all by itself. + +I'd check your disk array, then. It doesn't happen to be a Mylex, does it? + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 19:20:36 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5C28E4762F7 + for ; + Fri, 24 Jan 2003 19:20:34 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 06419476381 + for ; + Fri, 24 Jan 2003 19:17:46 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP + id F33A314535; Fri, 24 Jan 2003 19:17:48 -0500 (EST) +Date: Fri, 24 Jan 2003 19:17:48 -0500 +Subject: Re: WEIRD CRASH?!?! +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: pgsql-performance@postgresql.org +To: josh@agliodbs.com +From: Noah Silverman +In-Reply-To: <200301241615.24767.josh@agliodbs.com> +Message-Id: <6F2E6C98-2FFA-11D7-A3A3-000393AA8F3C@allresearch.com> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/301 +X-Sequence-Number: 948 + +We are using a 3ware escalade on this box. + +One clue. + +I actually moved the pg_xlog directory to another drive and then +symbolically linked it back to the data directory. + +Another idea is that Linux killed one of the processes because postgres +was using up too much memory. I belive the part of the kernel is +called "oomkiller". We're not sure if this happened, just a guess. + +Thanks, + +-N + + + +On Friday, January 24, 2003, at 07:15 PM, Josh Berkus wrote: + +> +> Noah, +> +>> but I'm the only one logged into this box, and I didn't kill anything. +>> It appears to have died all by itself. +> +> I'd check your disk array, then. It doesn't happen to be a Mylex, +> does it? +> +> -- +> -Josh Berkus +> Aglio Database Solutions +> San Francisco +> +> + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 19:29:09 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B69D3475E30 + for ; + Fri, 24 Jan 2003 19:29:08 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 4EF4D4761A1 + for ; + Fri, 24 Jan 2003 19:27:48 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id DC1E1D9A7; Fri, 24 Jan 2003 16:27:50 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id D13245C29; Fri, 24 Jan 2003 16:27:50 -0800 (PST) +Date: Fri, 24 Jan 2003 16:27:50 -0800 (PST) +From: Stephan Szabo +To: Josh Berkus +Cc: Noah Silverman , +Subject: Re: WEIRD CRASH?!?! +In-Reply-To: <200301241603.42263.josh@agliodbs.com> +Message-ID: <20030124162229.K38264-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/303 +X-Sequence-Number: 950 + +On Fri, 24 Jan 2003, Josh Berkus wrote: + +> Noah, +> +> > I think my server crashed and then restarted itself. Does anybody know +> > what all this means: +> > +> > 2003-01-24 18:28:06 PANIC: link from +> > /RAID/pgsql/pg_xlog/00000009000000BC to +> > /RAID/pgsql/pg_xlog/00000009000000C4 (initialization of log file 9, +> > segment 196) failed: File exists +> > 2003-01-24 18:28:06 LOG: server process (pid 1574) was terminated by +> > signal 6 +> > 2003-01-24 18:28:06 LOG: terminating any other active server processes +> > 2003-01-24 18:28:06 WARNING: Message from PostgreSQL backend: +> > The Postmaster has informed me that some other backend +> > died abnormally and possibly corrupted shared memory. +> > I have rolled back the current transaction and am +> > going to terminate your database system connection and exit. +> > Please reconnect to the database system and repeat your query. +> +> This means that somebody KILL -9'd a postgres process or the postmaster, and +> Postgres restarted in order to clear the shared buffers. If the database +> started up again, you are fine. + +Actually, it looks like an abort() (signal 6) to me. Probably from the +PANIC listed. + +The question is why did it get confused and end up linking to a filename +that already existed? + + + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 19:30:58 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 83D584758E6 + for ; + Fri, 24 Jan 2003 19:30:56 -0500 (EST) +Received: from VL-MS-MR002.sc1.videotron.ca (relais.videotron.ca + [24.201.245.36]) + by postgresql.org (Postfix) with ESMTP id 46FB847630B + for ; + Fri, 24 Jan 2003 19:30:52 -0500 (EST) +Received: from mochima.com ([66.131.15.233]) by VL-MS-MR002.sc1.videotron.ca + (iPlanet Messaging Server 5.2 HotFix 0.9 (built Jul 29 2002)) + with ESMTP id <0H98003HXURGVE@VL-MS-MR002.sc1.videotron.ca> for + pgsql-performance@postgresql.org; Fri, 24 Jan 2003 19:30:52 -0500 (EST) +Date: Fri, 24 Jan 2003 19:29:52 -0500 +From: Carlos Moreno +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +To: PgSQL Performance ML +Message-id: <3E31DA80.7000000@mochima.com> +MIME-version: 1.0 +Content-type: text/plain; charset=ISO-8859-1; format=flowed +Content-transfer-encoding: 7BIT +X-Accept-Language: en-us, en +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020827 +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> <3E3158DA.7080807@mochima.com> + <22650.1043442101@sss.pgh.pa.us> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/305 +X-Sequence-Number: 952 + +Tom Lane wrote: + +>Carlos Moreno writes: +> +>>And the second (and intriguing) problem: whenever I run pg_dump, +>>my system *freezes* until pg_dump finishes. When I say "system", +>>I mean the software that is running and sending data to the PG +>>database. +>> +> +>Other people have responded on the assumption that this is a performance +>problem, but you should also consider the possibility that it's bad +>coding of your application software. Does your app try to grab +>exclusive table locks? If so, it'll sit there waiting for the pg_dump +>to complete. +> + +Thanks Tom and the others that have replied. + +One quick question, Tom, before some general comments and +reply to the other messages... Where would I specify any +locks the software wants to do? Is it something you do +when connecting to the database, or when executing the +query?? (I ask this because, that I know, we're not doing +any locks; but this may just be lack of knowledge on my +part; I may be doing that without being aware of it) + +(I guess I'll check the docs, instead of asking you guys +to do my homework! :-)) + +Assuming that I indeed am not locking any tables, I tend to +suspect that it is a problem of excessive workload; I'd +like to doubt the possibility of defective hardware -- +it's a dedicated server hired from a company that I'd like +to believe are serious guys :-) (Rackforce.com, in case +someone wants to break some bad news to me :-O ) + +The server is a Dual Athlon 1.8GHz, with 1GB of RAM, +running Linux 7.3, and approx. 250MB for shared buffers. +I installed PostgreSQL from the sources (7.2.3). It's +running nothing else (I mean, no apache, no public ftp +or downloads), other than our application, that is. + +"vmstat -n 1" reports ZERO swaps (si and so columns) +during normal operation at peak times, and also during +pg_dump (CPU idle time typically is around 95%, maybe +going down to70 or 80 at peak times, and drops to approx. +40-60% during the time pg_dump is running -- would that +be high enough load to make the software slow down to +a crawl?). + +And no, as I said above, I don't think the software locks +any tables -- in fact, if you ask me, I would say *there +is* bad coding in the application, but precisely because +there are no locks, no transactions (I know, shame on me! +That's near the top in the list of most important things +to do...), so that's why I was so reluctant to believe +my colleague when he insisted that the pg_dump's were +"freezing" the application... I had to see it with my +own eyes, and on two different occasions, to be convinced +:-( + +In case this tells you something... The size of the +backup files (in plain ASCII) are around 300MB (the +command is "nice pg_dump -c -f file.sql dbname"). + + +Any further comments will be welcome and highly +appreciated. But thank you all for the replies so +far! It gives me a good starting point to do some +digging. + +Thanks, + +Carlos +-- + + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 19:30:11 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 862CC475E30 + for ; + Fri, 24 Jan 2003 19:30:10 -0500 (EST) +Received: from filer (12-235-198-106.client.attbi.com [12.235.198.106]) + by postgresql.org (Postfix) with ESMTP id F34B2475E2E + for ; + Fri, 24 Jan 2003 19:30:08 -0500 (EST) +Received: from localhost (localhost [127.0.0.1]) (uid 1000) + by filer with local; Fri, 24 Jan 2003 16:30:11 -0800 +Date: Fri, 24 Jan 2003 16:30:11 -0800 +From: Kevin Brown +To: pgsql-performance@postgresql.org +Subject: Re: Mount options for Ext3? +Message-ID: <20030125003011.GA28252@filer> +Mail-Followup-To: Kevin Brown , + pgsql-performance@postgresql.org +References: <200301241120.14404.josh@agliodbs.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +In-Reply-To: <200301241120.14404.josh@agliodbs.com> +User-Agent: Mutt/1.4i +Organization: Frobozzco International +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/304 +X-Sequence-Number: 951 + +Josh Berkus wrote: +> Folks, +> +> What mount options to people use for Ext3, particularly what do you set "data +> = " for a high-transaction database? I'm used to ReiserFS ("noatime, +> notail") and am not really sure where to go with Ext3. + +For ReiserFS, I can certainly understand using "noatime", but I'm not +sure why you use "notail" except to allow LILO to operate properly on +it. + +The default for ext3 is to do ordered writes: data is written before +the associated metadata transaction commits, but the data itself isn't +journalled. But because PostgreSQL synchronously writes the +transaction log (using fsync() by default, if I'm not mistaken) and +uses sync() during a savepoint, I would think that ordered writes at +the filesystem level would probably buy you very little in the way of +additional data integrity in the event of a crash. + +So if I'm right about that, then you might consider using the +"data=writeback" option for the filesystem that contains the actual +data (usually /usr/local/pgsql/data), but I'd use the default +("data=ordered") at the very least (I suppose there's no harm in using +"data=journal" if you're willing to put up with the performance hit, +but it's not clear to me what benefit, if any, there is) for +everything else. + + +I use ReiserFS also, so I'm basing the above on what knowledge I have +of the ext3 filesystem and the way PostgreSQL writes data. + + +The more interesting question in my mind is: if you use PostgreSQL on +an ext3 filesystem with "data=ordered" or "data=journal", can you get +away with turning off PostgreSQL's fsync altogether and still get the +same kind of data integrity that you'd get with fsync enabled? If the +operating system is able to guarantee data integrity, is it still +necessary to worry about it at the database level? + +I suspect the answer to that is that you can safely turn off fsync +only if the operating system will guarantee that write transactions +from a process are actually committed in the order they arrive from +that process. Otherwise you'd have to worry about write transactions +to the transaction log committing before the writes to the data files +during a savepoint, which would leave the overall database in an +inconsistent state if the system were to crash after the transaction +log write (which marks the savepoint as completed) committed but +before the data file writes committed. And my suspicion is that the +operating system rarely makes any such guarantee, journalled +filesystem or not. + + + +-- +Kevin Brown kevin@sysexperts.com + +From pgsql-performance-owner@postgresql.org Fri Jan 24 19:50:39 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7BD63476179 + for ; + Fri, 24 Jan 2003 19:50:36 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 003AE475E3E + for ; + Fri, 24 Jan 2003 19:50:21 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0P0oO5u027965; + Fri, 24 Jan 2003 19:50:24 -0500 (EST) +To: Noah Silverman +Cc: pgsql-performance@postgresql.org +Subject: Re: Multiple databases one directory +In-reply-to: +References: +Comments: In-reply-to Noah Silverman + message dated "Fri, 24 Jan 2003 17:39:42 -0500" +Date: Fri, 24 Jan 2003 19:50:24 -0500 +Message-ID: <27964.1043455824@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/306 +X-Sequence-Number: 953 + +Noah Silverman writes: +> We have a situation where we will be creating two fairly large and +> complex databases with many tables (thousands) each. From what I +> understand, postgres keeps everything in one big data directory. + +Yeah. You're kind of at the mercy of the operating system when you do +that: if it copes well with big directories, no problem, but if lookups +in big directories are slow then you'll take a performance hit. + +The first thing I'd ask is *why* you think you need thousands of +tables. How will you keep track of them? Are there really thousands of +different table schemas? Maybe you can combine tables by introducing +an extra key column. + +Perhaps a little bit of rethinking will yield a small design screaming +to get out of this big one ... + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 19:59:50 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 66CC14762B8 + for ; + Fri, 24 Jan 2003 19:59:49 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id C1B77476127 + for ; + Fri, 24 Jan 2003 19:56:58 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP + id 3A3453C178; Fri, 24 Jan 2003 19:57:02 -0500 (EST) +Date: Fri, 24 Jan 2003 19:57:01 -0500 +Subject: Re: Multiple databases one directory +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: pgsql-performance@postgresql.org +To: Tom Lane +From: Noah Silverman +In-Reply-To: <27964.1043455824@sss.pgh.pa.us> +Message-Id: +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/307 +X-Sequence-Number: 954 + +Thanks, + +We're considering this. + +On an unrelated note, it looks like our crash was due to running out of +file descriptors for the bash shell. + +Linux won't let me increase the limit for a user other than root. Does +anyone know how to change this (We're running slackware) + + +Thanks, + +-N + + +On Friday, January 24, 2003, at 07:50 PM, Tom Lane wrote: + +> Noah Silverman writes: +>> We have a situation where we will be creating two fairly large and +>> complex databases with many tables (thousands) each. From what I +>> understand, postgres keeps everything in one big data directory. +> +> Yeah. You're kind of at the mercy of the operating system when you do +> that: if it copes well with big directories, no problem, but if lookups +> in big directories are slow then you'll take a performance hit. +> +> The first thing I'd ask is *why* you think you need thousands of +> tables. How will you keep track of them? Are there really thousands +> of +> different table schemas? Maybe you can combine tables by introducing +> an extra key column. +> +> Perhaps a little bit of rethinking will yield a small design screaming +> to get out of this big one ... +> +> regards, tom lane +> + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 20:10:00 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4C77D47613F + for ; + Fri, 24 Jan 2003 20:09:59 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id D697F4764C9 + for ; + Fri, 24 Jan 2003 20:04:26 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0P1475u028080; + Fri, 24 Jan 2003 20:04:08 -0500 (EST) +To: Noah Silverman +Cc: josh@agliodbs.com, pgsql-performance@postgresql.org +Subject: Re: WEIRD CRASH?!?! +In-reply-to: <6F2E6C98-2FFA-11D7-A3A3-000393AA8F3C@allresearch.com> +References: <6F2E6C98-2FFA-11D7-A3A3-000393AA8F3C@allresearch.com> +Comments: In-reply-to Noah Silverman + message dated "Fri, 24 Jan 2003 19:17:48 -0500" +Date: Fri, 24 Jan 2003 20:04:07 -0500 +Message-ID: <28079.1043456647@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/308 +X-Sequence-Number: 955 + +Noah Silverman writes: +> One clue. +> I actually moved the pg_xlog directory to another drive and then +> symbolically linked it back to the data directory. + +Uh, did you have the postmaster shut down while you did that? + +This looks like a collision between two processes both trying to create +the next segment of the xlog at about the same time. But there are +interlocks that are supposed to prevent that. + +I don't think you need to worry about the integrity of your data; the +panic reset should put everything right. But I'd sure be interested +if you can reproduce this problem. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 20:10:10 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9916C476260 + for ; + Fri, 24 Jan 2003 20:10:07 -0500 (EST) +Received: from filer (12-235-198-106.client.attbi.com [12.235.198.106]) + by postgresql.org (Postfix) with ESMTP id 1D8CB476852 + for ; + Fri, 24 Jan 2003 20:04:33 -0500 (EST) +Received: from localhost (localhost [127.0.0.1]) (uid 1000) + by filer with local; Fri, 24 Jan 2003 17:04:36 -0800 +Date: Fri, 24 Jan 2003 17:04:36 -0800 +From: Kevin Brown +To: PgSQL Performance ML +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +Message-ID: <20030125010436.GB28252@filer> +Mail-Followup-To: Kevin Brown , + PgSQL Performance ML +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> + <3E3158DA.7080807@mochima.com> <22650.1043442101@sss.pgh.pa.us> + <3E31DA80.7000000@mochima.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +In-Reply-To: <3E31DA80.7000000@mochima.com> +User-Agent: Mutt/1.4i +Organization: Frobozzco International +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/309 +X-Sequence-Number: 956 + +Carlos Moreno wrote: +> And no, as I said above, I don't think the software locks +> any tables -- in fact, if you ask me, I would say *there +> is* bad coding in the application, but precisely because +> there are no locks, no transactions (I know, shame on me! +> That's near the top in the list of most important things +> to do...), so that's why I was so reluctant to believe +> my colleague when he insisted that the pg_dump's were +> "freezing" the application... I had to see it with my +> own eyes, and on two different occasions, to be convinced +> :-( +> +> In case this tells you something... The size of the +> backup files (in plain ASCII) are around 300MB (the +> command is "nice pg_dump -c -f file.sql dbname"). + +One thing you can do to help track this down is to place + + stats_command_string = on + +in your postgresql.conf and restart the database (it may be sufficient +to tell the database to reread the config file via "pg_ctl reload"). +Then, when the backup is going, run the application. + +When it "freezes", connect to the database via psql as the user +postgres and do a "select * from pg_stat_activity". You'll see the +list of connected processes and the current query being executed by +each, if any. + +Do that multiple times and you should see the progress, if any, the +application is making in terms of database queries. + + +Hope this helps... + + +-- +Kevin Brown kevin@sysexperts.com + +From pgsql-performance-owner@postgresql.org Fri Jan 24 20:11:41 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 06B474761A1 + for ; + Fri, 24 Jan 2003 20:11:40 -0500 (EST) +Received: from jester.senspire.com + (CPE00508b028d7d-CM00803785c5e0.cpe.net.cable.rogers.com + [24.103.51.175]) + by postgresql.org (Postfix) with ESMTP id 1F23C475E3E + for ; + Fri, 24 Jan 2003 20:09:04 -0500 (EST) +Received: from [127.0.0.1] (localhost [127.0.0.1]) + by jester.senspire.com (8.12.6/8.12.6) with ESMTP id h0P18Oe5080765; + Fri, 24 Jan 2003 20:08:25 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: WEIRD CRASH?!?! +From: Rod Taylor +To: Noah Silverman +Cc: josh@agliodbs.com, + Postgresql Performance +In-Reply-To: <6F2E6C98-2FFA-11D7-A3A3-000393AA8F3C@allresearch.com> +References: <6F2E6C98-2FFA-11D7-A3A3-000393AA8F3C@allresearch.com> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-oBQQt+Qyi65FG5beWoGY" +Organization: +Message-Id: <1043456904.58142.96.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 24 Jan 2003 20:08:24 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/310 +X-Sequence-Number: 957 + +--=-oBQQt+Qyi65FG5beWoGY +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +On Fri, 2003-01-24 at 19:17, Noah Silverman wrote: +> We are using a 3ware escalade on this box. +>=20 +> One clue. +>=20 +> I actually moved the pg_xlog directory to another drive and then=20 +> symbolically linked it back to the data directory. + +You shut it down first right? + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-oBQQt+Qyi65FG5beWoGY +Content-Type: application/pgp-signature; name=signature.asc +Content-Description: This is a digitally signed message part + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (FreeBSD) + +iD8DBQA+MeOH6DETLow6vwwRAuqcAJ0YxcnV3HZ2huNrrWLPaKxVqbHluQCfdKwL +XyFYWGP9QFu3P5bY+aG1cmA= +=Lp5M +-----END PGP SIGNATURE----- + +--=-oBQQt+Qyi65FG5beWoGY-- + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 20:14:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1AB0047607D + for ; + Fri, 24 Jan 2003 20:14:05 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 98CE7476167 + for ; + Fri, 24 Jan 2003 20:12:08 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0P1C75u028127; + Fri, 24 Jan 2003 20:12:07 -0500 (EST) +To: Stephan Szabo +Cc: Josh Berkus , Noah Silverman , + pgsql-performance@postgresql.org +Subject: Re: WEIRD CRASH?!?! +In-reply-to: <20030124162229.K38264-100000@megazone23.bigpanda.com> +References: <20030124162229.K38264-100000@megazone23.bigpanda.com> +Comments: In-reply-to Stephan Szabo + message dated "Fri, 24 Jan 2003 16:27:50 -0800" +Date: Fri, 24 Jan 2003 20:12:06 -0500 +Message-ID: <28126.1043457126@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/311 +X-Sequence-Number: 958 + +Stephan Szabo writes: +> The question is why did it get confused and end up linking to a filename +> that already existed? + +The message comes from InstallXLogFileSegment(), which is careful to +ensure that the link() cannot fail, either by unlinking the previous +file, or searching for an unused name. But it failed anyway. + +It seems to me that there are only two possible explanations: a race +condition (but holding ControlFileLock should prevent that) or +BasicOpenFile() failed for a reason other than nonexistence of the file. + +Hmm ... I wonder if Noah's machine could have been running out of kernel +file table slots, or something like that? It does seem that it'd be +more robust to use something like stat(2) to probe for an existing file. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 20:14:35 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4E8864762DC + for ; + Fri, 24 Jan 2003 20:14:34 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 4E1354760CC + for ; + Fri, 24 Jan 2003 20:14:06 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP + id 9BEB93C235; Fri, 24 Jan 2003 20:14:09 -0500 (EST) +Date: Fri, 24 Jan 2003 20:14:09 -0500 +Subject: Re: WEIRD CRASH?!?! +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: Postgresql Performance , + josh@agliodbs.com +To: Rod Taylor +From: Noah Silverman +In-Reply-To: <1043456904.58142.96.camel@jester> +Message-Id: <4E61F6E7-3002-11D7-A3A3-000393AA8F3C@allresearch.com> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/312 +X-Sequence-Number: 959 + +OF COURSE! + +It actually looks like the problem was with file descriptors. Our +shell only had 1024 set, and we also have mysql running and using up a +bunch of those. We just upped to limit to 8000 to see it that would +give postgres more room to breathe. + +-N + +On Friday, January 24, 2003, at 08:08 PM, Rod Taylor wrote: + +> On Fri, 2003-01-24 at 19:17, Noah Silverman wrote: +>> We are using a 3ware escalade on this box. +>> +>> One clue. +>> +>> I actually moved the pg_xlog directory to another drive and then +>> symbolically linked it back to the data directory. +> +> You shut it down first right? +> +> -- +> Rod Taylor +> +> PGP Key: http://www.rbt.ca/rbtpub.asc +> + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 20:16:46 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1A39C475B33 + for ; + Fri, 24 Jan 2003 20:16:46 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 514A9475461 + for ; + Fri, 24 Jan 2003 20:16:45 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0P1Gm5u028177; + Fri, 24 Jan 2003 20:16:48 -0500 (EST) +To: Kevin Brown +Cc: pgsql-performance@postgresql.org +Subject: Re: Mount options for Ext3? +In-reply-to: <20030125003011.GA28252@filer> +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> +Comments: In-reply-to Kevin Brown + message dated "Fri, 24 Jan 2003 16:30:11 -0800" +Date: Fri, 24 Jan 2003 20:16:48 -0500 +Message-ID: <28176.1043457408@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/313 +X-Sequence-Number: 960 + +Kevin Brown writes: +> I suspect the answer to that is that you can safely turn off fsync +> only if the operating system will guarantee that write transactions +> from a process are actually committed in the order they arrive from +> that process. + +Yeah. We use fsync partly so that when we tell a client a transaction +is committed, it really is committed (ie, down to disk) --- but also +as a means of controlling write order. I strongly doubt that any modern +filesystem will promise to execute writes exactly in the order issued, +unless prodded by means such as fsync. + +> Otherwise you'd have to worry about write transactions +> to the transaction log committing before the writes to the data files +> during a savepoint, + +Actually, the other way around is the problem. The WAL algorithm works +so long as log writes hit disk before the data-file changes they +describe (that's why it's called write *ahead* log). + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 20:19:03 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D5D57475F1A + for ; + Fri, 24 Jan 2003 20:19:01 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 2780C475D17 + for ; + Fri, 24 Jan 2003 20:19:01 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0P1J35u028205; + Fri, 24 Jan 2003 20:19:03 -0500 (EST) +To: Carlos Moreno +Cc: PgSQL Performance ML +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +In-reply-to: <3E31DA80.7000000@mochima.com> +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> + <3E3158DA.7080807@mochima.com> <22650.1043442101@sss.pgh.pa.us> + <3E31DA80.7000000@mochima.com> +Comments: In-reply-to Carlos Moreno + message dated "Fri, 24 Jan 2003 19:29:52 -0500" +Date: Fri, 24 Jan 2003 20:19:02 -0500 +Message-ID: <28204.1043457542@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/314 +X-Sequence-Number: 961 + +Carlos Moreno writes: +> Tom Lane wrote: +>> Other people have responded on the assumption that this is a performance +>> problem, but you should also consider the possibility that it's bad +>> coding of your application software. Does your app try to grab +>> exclusive table locks? + +> One quick question, Tom, before some general comments and +> reply to the other messages... Where would I specify any +> locks the software wants to do? + +If you are not issuing any explicit "LOCK" SQL commands, then you can +disregard my theory. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 20:20:01 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8190B475B33 + for ; + Fri, 24 Jan 2003 20:19:59 -0500 (EST) +Received: from jester.senspire.com + (CPE00508b028d7d-CM00803785c5e0.cpe.net.cable.rogers.com + [24.103.51.175]) + by postgresql.org (Postfix) with ESMTP id 0AE11475461 + for ; + Fri, 24 Jan 2003 20:19:58 -0500 (EST) +Received: from [127.0.0.1] (localhost [127.0.0.1]) + by jester.senspire.com (8.12.6/8.12.6) with ESMTP id h0P1KBe5080819; + Fri, 24 Jan 2003 20:20:15 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: WEIRD CRASH?!?! +From: Rod Taylor +To: Noah Silverman +Cc: Postgresql Performance , + josh@agliodbs.com +In-Reply-To: <4E61F6E7-3002-11D7-A3A3-000393AA8F3C@allresearch.com> +References: <4E61F6E7-3002-11D7-A3A3-000393AA8F3C@allresearch.com> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-Wp5XeiECyJWSJvOp1B35" +Organization: +Message-Id: <1043457611.58142.99.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 24 Jan 2003 20:20:11 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/315 +X-Sequence-Number: 962 + +--=-Wp5XeiECyJWSJvOp1B35 +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +On Fri, 2003-01-24 at 20:14, Noah Silverman wrote: +> OF COURSE! + +Sorry, but I've seen people try to do that stuff before. + + +> On Friday, January 24, 2003, at 08:08 PM, Rod Taylor wrote: +>=20 +> > On Fri, 2003-01-24 at 19:17, Noah Silverman wrote: +> >> We are using a 3ware escalade on this box. +> >> +> >> One clue. +> >> +> >> I actually moved the pg_xlog directory to another drive and then +> >> symbolically linked it back to the data directory. +> > +> > You shut it down first right? +> > +> > --=20 +> > Rod Taylor +> > +> > PGP Key: http://www.rbt.ca/rbtpub.asc +> > +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-Wp5XeiECyJWSJvOp1B35 +Content-Type: application/pgp-signature; name=signature.asc +Content-Description: This is a digitally signed message part + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (FreeBSD) + +iD8DBQA+MeZL6DETLow6vwwRAhDnAJ9Go/2GrHMRVPVzc2dAIEh9uml5xACfe+uU +yjvoG5gwcQd+PvQIX1Kvd1s= +=V4FH +-----END PGP SIGNATURE----- + +--=-Wp5XeiECyJWSJvOp1B35-- + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 20:29:42 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 66875475B33 + for ; + Fri, 24 Jan 2003 20:29:40 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 52CBB475461 + for ; + Fri, 24 Jan 2003 20:29:39 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0P1Tf5u028261; + Fri, 24 Jan 2003 20:29:41 -0500 (EST) +To: Carlos Moreno , + PgSQL Performance ML +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +In-reply-to: <28204.1043457542@sss.pgh.pa.us> +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> + <3E3158DA.7080807@mochima.com> <22650.1043442101@sss.pgh.pa.us> + <3E31DA80.7000000@mochima.com> <28204.1043457542@sss.pgh.pa.us> +Comments: In-reply-to Tom Lane + message dated "Fri, 24 Jan 2003 20:19:02 -0500" +Date: Fri, 24 Jan 2003 20:29:41 -0500 +Message-ID: <28260.1043458181@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/316 +X-Sequence-Number: 963 + +I said: +> Carlos Moreno writes: +>> One quick question, Tom, before some general comments and +>> reply to the other messages... Where would I specify any +>> locks the software wants to do? + +> If you are not issuing any explicit "LOCK" SQL commands, then you can +> disregard my theory. + +Actually, that's too simple. Are you creating and dropping tables, +or issuing schema-change commands (such as ADD COLUMN or RENAME)? +All of those things take exclusive locks on the tables they modify. +Ordinary SELECT/INSERT/UPDATE/DELETE operations can run in parallel with +pg_dump, but messing with the database structure is another story. + +I guess the real question here is whether your app is actually stopped +dead (as it would be if waiting for a lock), or just slowed to a crawl +(as a performance problem could do). I cannot tell if your "frozen" +description is hyperbole or literal truth. + +One thing that might help diagnose it is to look at the output of ps +auxww (or ps -ef on SysV-ish platforms) to see what all the backends are +currently doing while the problem exists. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 20:38:43 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5217E475B33 + for ; + Fri, 24 Jan 2003 20:38:43 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 8F2F7475461 + for ; + Fri, 24 Jan 2003 20:38:42 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0P1ci5u028321; + Fri, 24 Jan 2003 20:38:44 -0500 (EST) +To: Noah Silverman +Cc: Rod Taylor , + Postgresql Performance , + josh@agliodbs.com +Subject: Re: WEIRD CRASH?!?! +In-reply-to: <4E61F6E7-3002-11D7-A3A3-000393AA8F3C@allresearch.com> +References: <4E61F6E7-3002-11D7-A3A3-000393AA8F3C@allresearch.com> +Comments: In-reply-to Noah Silverman + message dated "Fri, 24 Jan 2003 20:14:09 -0500" +Date: Fri, 24 Jan 2003 20:38:44 -0500 +Message-ID: <28320.1043458724@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/317 +X-Sequence-Number: 964 + +Noah Silverman writes: +> It actually looks like the problem was with file descriptors. Our +> shell only had 1024 set, and we also have mysql running and using up a +> bunch of those. We just upped to limit to 8000 to see it that would +> give postgres more room to breathe. + +Ah-hah. You might also want to set max_files_per_process (in +postgresql.conf) to something small enough to ensure Postgres can't run +you out of descriptors. Linux has a bad habit of promising more than +it can deliver when Postgres asks how many FDs are okay to use. The +max_files_per_process setting is useful to prevent Postgres from +believing whatever fairy-tale sysconf(3) tells it. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 21:11:59 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C1FF1475F1A + for ; + Fri, 24 Jan 2003 21:11:58 -0500 (EST) +Received: from filer (12-235-198-106.client.attbi.com [12.235.198.106]) + by postgresql.org (Postfix) with ESMTP id 136CF475E2E + for ; + Fri, 24 Jan 2003 21:11:56 -0500 (EST) +Received: from localhost (localhost [127.0.0.1]) (uid 1000) + by filer with local; Fri, 24 Jan 2003 18:11:59 -0800 +Date: Fri, 24 Jan 2003 18:11:59 -0800 +From: Kevin Brown +To: pgsql-performance@postgresql.org +Subject: Re: Mount options for Ext3? +Message-ID: <20030125021159.GC28252@filer> +Mail-Followup-To: Kevin Brown , + pgsql-performance@postgresql.org +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> <28176.1043457408@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +In-Reply-To: <28176.1043457408@sss.pgh.pa.us> +User-Agent: Mutt/1.4i +Organization: Frobozzco International +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/318 +X-Sequence-Number: 965 + +Tom Lane wrote: +> > Otherwise you'd have to worry about write transactions +> > to the transaction log committing before the writes to the data files +> > during a savepoint, +> +> Actually, the other way around is the problem. The WAL algorithm works +> so long as log writes hit disk before the data-file changes they +> describe (that's why it's called write *ahead* log). + +Hmm...a case where the transaction data gets written to the files +before the transaction itself even manages to get written to the log? +True. But I was thinking about the following: + +I was presuming that when a savepoint occurs, a marker is written to +the log indicating which transactions had been committed to the data +files, and that this marker was paid attention to during database +startup. + +So suppose the marker makes it to the log but not all of the data the +marker refers to makes it to the data files. Then the system crashes. + +When the database starts back up, the savepoint marker in the +transaction log shows that the transactions had already been committed +to disk. But because the OS wrote the requested data (including the +savepoint marker) out of order, the savepoint marker made it to the +disk before some of the data made it to the data files. And so, the +database is in an inconsistent state and it has no way to know about +it. + +But then, I guess the easy way around the above problem is to always +commit all the transactions in the log to disk when the database comes +up, which renders the savepoint marker moot...and leads back to the +scenario you were referring to... + +If the savepoint only commits the older transactions in the log (and +not all of them) to disk, the possibility of the situation you're +referring would, I'd think, be reduced (possibly quite considerably). + + + +...or is my understanding of how all this works completely off? + + + + +-- +Kevin Brown kevin@sysexperts.com + +From pgsql-performance-owner@postgresql.org Fri Jan 24 21:22:10 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6E09C475F1A + for ; + Fri, 24 Jan 2003 21:22:09 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 0CD604758E6 + for ; + Fri, 24 Jan 2003 21:21:53 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2325202; Fri, 24 Jan 2003 18:22:00 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Kevin Brown , + pgsql-performance@postgresql.org +Subject: Re: Mount options for Ext3? +Date: Fri, 24 Jan 2003 18:22:33 -0800 +X-Mailer: KMail [version 1.4] +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> +In-Reply-To: <20030125003011.GA28252@filer> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301241822.33731.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/319 +X-Sequence-Number: 966 + + +Kevin, + +> So if I'm right about that, then you might consider using the +> "data=3Dwriteback" option for the filesystem that contains the actual +> data (usually /usr/local/pgsql/data), but I'd use the default +> ("data=3Dordered") at the very least (I suppose there's no harm in using +> "data=3Djournal" if you're willing to put up with the performance hit, +> but it's not clear to me what benefit, if any, there is) for +> everything else. + +Well, the only reason I use Ext3 rather than Ext2 is to prevent fsck's on= +=20 +restart after a crash. So I'm interested in the data option that gives t= +he=20 +minimum performance hit, even if it means that I sacrifice some reliability= +.=20=20=20 +I'm running with fsynch on, and the DB is on a mirrored drive array, so I'm= +=20 +not too worried about filesystem-level errors. + +So would that be "data=3Dwriteback"? + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Jan 24 21:50:07 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E202C4758E6 + for ; + Fri, 24 Jan 2003 21:50:05 -0500 (EST) +Received: from filer (12-235-198-106.client.attbi.com [12.235.198.106]) + by postgresql.org (Postfix) with ESMTP id 2F2C8475461 + for ; + Fri, 24 Jan 2003 21:50:05 -0500 (EST) +Received: from localhost (localhost [127.0.0.1]) (uid 1000) + by filer with local; Fri, 24 Jan 2003 18:50:08 -0800 +Date: Fri, 24 Jan 2003 18:50:08 -0800 +From: Kevin Brown +To: pgsql-performance@postgresql.org +Subject: Re: Mount options for Ext3? +Message-ID: <20030125025008.GD28252@filer> +Mail-Followup-To: Kevin Brown , + pgsql-performance@postgresql.org +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> + <200301241822.33731.josh@agliodbs.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +In-Reply-To: <200301241822.33731.josh@agliodbs.com> +User-Agent: Mutt/1.4i +Organization: Frobozzco International +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/320 +X-Sequence-Number: 967 + +Josh Berkus wrote: +> Well, the only reason I use Ext3 rather than Ext2 is to prevent fsck's on +> restart after a crash. So I'm interested in the data option that gives the +> minimum performance hit, even if it means that I sacrifice some reliability. +> I'm running with fsynch on, and the DB is on a mirrored drive array, so I'm +> not too worried about filesystem-level errors. +> +> So would that be "data=writeback"? + +Yes. That should give almost the same semantics as ext2 does by +default, except that metadata is journalled, so no fsck needed. :-) + +In fact, I believe that's exactly how ReiserFS works, if I'm not +mistaken (I saw someone claim that it does data journalling, but I've +never seen any references to how to get ReiserFS to journal data). + + +BTW, why exactly are you running ext3? It has some nice journalling +features but it sounds like you don't want to use them. But at the +same time, it uses pre-allocated inodes just like ext2 does, so it's +possible to run out of inodes on ext2/3 while AFAIK that's not +possible under ReiserFS. That's not likely to be a problem unless +you're running a news server or something, though. :-) + +On the other hand, ext3 with data=writeback will probably be faster +than ReiserFS for a number of things. + +No idea how stable ext3 is versus ReiserFS... + + + +-- +Kevin Brown kevin@sysexperts.com + +From pgsql-performance-owner@postgresql.org Fri Jan 24 21:58:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 08EAD4758E6 + for ; + Fri, 24 Jan 2003 21:58:53 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 3490B475461 + for ; + Fri, 24 Jan 2003 21:58:52 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0P2wu5u001261; + Fri, 24 Jan 2003 21:58:56 -0500 (EST) +To: Kevin Brown +Cc: pgsql-performance@postgresql.org +Subject: Re: Mount options for Ext3? +In-reply-to: <20030125021159.GC28252@filer> +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> <28176.1043457408@sss.pgh.pa.us> + <20030125021159.GC28252@filer> +Comments: In-reply-to Kevin Brown + message dated "Fri, 24 Jan 2003 18:11:59 -0800" +Date: Fri, 24 Jan 2003 21:58:55 -0500 +Message-ID: <1260.1043463535@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/321 +X-Sequence-Number: 968 + +Kevin Brown writes: +> I was presuming that when a savepoint occurs, a marker is written to +> the log indicating which transactions had been committed to the data +> files, and that this marker was paid attention to during database +> startup. + +Not quite. The marker says that all datafile updates described by +log entries before point X have been flushed to disk by the checkpoint +--- and, therefore, if we need to restart we need only replay log +entries occurring after the last checkpoint's point X. + +This has nothing directly to do with which transactions are committed +or not committed. If we based checkpoint behavior on that, we'd need +to maintain an indefinitely large amount of WAL log to cope with +long-running transactions. + +The actual checkpoint algorithm is + + take note of current logical end of WAL (this will be point X) + write() all dirty buffers in shared buffer arena + sync() to ensure that above writes, as well as previous ones, + are on disk + put checkpoint record referencing point X into WAL; write and + fsync WAL + update pg_control with new checkpoint record, fsync it + +Since pg_control is what's examined after restart, the checkpoint is +effectively committed when the pg_control write hits disk. At any +instant before that, a crash would result in replaying from the +prior checkpoint's point X. The algorithm is correct if and only if +the pg_control write hits disk after all the other writes mentioned. + +The key assumption we are making about the filesystem's behavior is that +writes scheduled by the sync() will occur before the pg_control write +that's issued after it. People have occasionally faulted this algorithm +by quoting the sync() man page, which saith (in the Gospel According To +HP) + + The writing, although scheduled, is not necessarily complete upon + return from sync. + +This, however, is not a problem in itself. What we need to know is +whether the filesystem will allow writes issued after the sync() to +complete before those "scheduled" by the sync(). + + +> So suppose the marker makes it to the log but not all of the data the +> marker refers to makes it to the data files. Then the system crashes. + +I think that this analysis is not relevant to what we're doing. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 22:10:32 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D10EB475D17 + for ; + Fri, 24 Jan 2003 22:10:30 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 16E1B475B33 + for ; + Fri, 24 Jan 2003 22:10:30 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0P3AR5u001331; + Fri, 24 Jan 2003 22:10:28 -0500 (EST) +To: Stephan Szabo , + Josh Berkus , Noah Silverman , + pgsql-performance@postgresql.org +Subject: Re: WEIRD CRASH?!?! +In-reply-to: <28126.1043457126@sss.pgh.pa.us> +References: <20030124162229.K38264-100000@megazone23.bigpanda.com> + <28126.1043457126@sss.pgh.pa.us> +Comments: In-reply-to Tom Lane + message dated "Fri, 24 Jan 2003 20:12:06 -0500" +Date: Fri, 24 Jan 2003 22:10:27 -0500 +Message-ID: <1330.1043464227@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/322 +X-Sequence-Number: 969 + +I wrote: +> Hmm ... I wonder if Noah's machine could have been running out of kernel +> file table slots, or something like that? It does seem that it'd be +> more robust to use something like stat(2) to probe for an existing file. + +I've applied a patch to do it that way in CVS HEAD. After examining the +code further I'm inclined not to risk back-patching it into 7.3, though. +xlog.c is full of open() calls that will elog(PANIC) if they fail, so +I think there was only a very small window of opportunity for Noah to +see this failure and not another one. The patch thus probably +contributes little real gain in reliability. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Jan 24 23:13:17 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EC9B1475461 + for ; + Fri, 24 Jan 2003 23:13:15 -0500 (EST) +Received: from filer (12-235-198-106.client.attbi.com [12.235.198.106]) + by postgresql.org (Postfix) with ESMTP id 2182E474E42 + for ; + Fri, 24 Jan 2003 23:13:15 -0500 (EST) +Received: from localhost (localhost [127.0.0.1]) (uid 1000) + by filer with local; Fri, 24 Jan 2003 20:13:19 -0800 +Date: Fri, 24 Jan 2003 20:13:19 -0800 +From: Kevin Brown +To: pgsql-performance@postgresql.org +Subject: Re: Mount options for Ext3? +Message-ID: <20030125041319.GE28252@filer> +Mail-Followup-To: Kevin Brown , + pgsql-performance@postgresql.org +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> <28176.1043457408@sss.pgh.pa.us> + <20030125021159.GC28252@filer> <1260.1043463535@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +In-Reply-To: <1260.1043463535@sss.pgh.pa.us> +User-Agent: Mutt/1.4i +Organization: Frobozzco International +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/323 +X-Sequence-Number: 970 + +Tom Lane wrote: +> Kevin Brown writes: +> > I was presuming that when a savepoint occurs, a marker is written to +> > the log indicating which transactions had been committed to the data +> > files, and that this marker was paid attention to during database +> > startup. +> +> Not quite. The marker says that all datafile updates described by +> log entries before point X have been flushed to disk by the checkpoint +> --- and, therefore, if we need to restart we need only replay log +> entries occurring after the last checkpoint's point X. +> +> This has nothing directly to do with which transactions are committed +> or not committed. If we based checkpoint behavior on that, we'd need +> to maintain an indefinitely large amount of WAL log to cope with +> long-running transactions. + +Ah. My apologies for my imprecise wording. I should have said +"...indicating which transactions had been written to the data files" +instead of "...had been committed to the data files", and meant to say +"checkpoint" but instead said "savepoint". I'll try to do better +here. + +> The actual checkpoint algorithm is +> +> take note of current logical end of WAL (this will be point X) +> write() all dirty buffers in shared buffer arena +> sync() to ensure that above writes, as well as previous ones, +> are on disk +> put checkpoint record referencing point X into WAL; write and +> fsync WAL +> update pg_control with new checkpoint record, fsync it +> +> Since pg_control is what's examined after restart, the checkpoint is +> effectively committed when the pg_control write hits disk. At any +> instant before that, a crash would result in replaying from the +> prior checkpoint's point X. The algorithm is correct if and only if +> the pg_control write hits disk after all the other writes mentioned. + +[...] + +> > So suppose the marker makes it to the log but not all of the data the +> > marker refers to makes it to the data files. Then the system crashes. +> +> I think that this analysis is not relevant to what we're doing. + +Agreed. The context of that analysis is when synchronous writes by +the database are turned off and one is left to rely on the operating +system to do the right thing. Clearly it doesn't apply when +synchronous writes are enabled. As long as only one process handles a +checkpoint, an operating system that guarantees that a process' writes +are committed to disk in the same order that they were requested, +combined with a journalling filesystem that at least wrote all data +prior to committing the associated metadata transactions, would be +sufficient to guarantee the integrity of the database even if all +synchronous writes by the database were turned off. This would hold +even if the operating system reordered writes from multiple processes. +It suggests an operating system feature that could be considered +highly desirable (and relates to the discussion elsewhere about +trading off shared buffers against OS file cache: it's often better to +rely on the abilities of the OS rather than roll your own mechanism). + +One question I have is: in the event of a crash, why not simply replay +all the transactions found in the WAL? Is the startup time of the +database that badly affected if pg_control is ignored? + +If there exists somewhere a reasonably succinct description of the +reasoning behind the current transaction management scheme (including +an analysis of the pros and cons), I'd love to read it and quit +bugging you. :-) + + +-- +Kevin Brown kevin@sysexperts.com + +From pgsql-performance-owner@postgresql.org Fri Jan 24 23:21:00 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BA26E475B33 + for ; + Fri, 24 Jan 2003 23:20:58 -0500 (EST) +Received: from platonic.cynic.net (platonic.cynic.net [204.80.150.245]) + by postgresql.org (Postfix) with ESMTP id C9405475AAC + for ; + Fri, 24 Jan 2003 23:20:57 -0500 (EST) +Received: from angelic.cynic.net (angelic-platonic.cvpn.cynic.net + [198.73.220.226]) by platonic.cynic.net (Postfix) with ESMTP + id 0F76AC003; Sat, 25 Jan 2003 04:20:58 +0000 (UTC) +Received: from localhost (localhost [127.0.0.1]) + by angelic.cynic.net (Postfix) with ESMTP + id 2AF268736; Sat, 25 Jan 2003 13:20:49 +0900 (JST) +Date: Sat, 25 Jan 2003 13:20:49 +0900 (JST) +From: Curt Sampson +To: Carlos Moreno +Cc: PgSQL Performance ML +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +In-Reply-To: <3E31DA80.7000000@mochima.com> +Message-ID: +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> + <3E3158DA.7080807@mochima.com> <22650.1043442101@sss.pgh.pa.us> + <3E31DA80.7000000@mochima.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/324 +X-Sequence-Number: 971 + +On Fri, 24 Jan 2003, Carlos Moreno wrote: + + +> The server is a Dual Athlon 1.8GHz, with 1GB of RAM, +> running Linux 7.3, and approx. 250MB for shared buffers. +> ... +> In case this tells you something... The size of the +> backup files (in plain ASCII) are around 300MB (the +> command is "nice pg_dump -c -f file.sql dbname"). + +I was going to ask you to check your disk I/O statistics, but that tells +me that disk I/O is probably not the problem. If the ASCII dump file +(I assume by "plain ASCII" you mean uncompressed as well) is only 300 +MB, your database size is likely well under 100 MB. In which case the +entire database ought to be residing in the buffer cache, and you should +see maximum CPU utilisation during the dump, and not too much disk +I/O. (This is, however, assuming that that's the only database on your +machine. You don't have another 250 GB database that gets lots of random +access hiding there, do you? :-)) + +On a big machine like that, with such a small database, you should be +able to do a dump in a couple of minutes with little noticable impact on +the performance of clients. + +I would probably start with carefully tracing what your clients are doing +during backup, and where they're blocking. + +cjs +-- +Curt Sampson +81 90 7737 2974 http://www.netbsd.org + Don't you know, in this new Dark Age, we're all light. --XTC + +From pgsql-hackers-owner@postgresql.org Sat Jan 25 01:46:03 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 1089A476E5B; Sat, 25 Jan 2003 01:46:03 -0500 (EST) +Received: from sss.pgh.pa.us (sss-backup.pgh.pa.us [216.151.103.158]) + by postgresql.org (Postfix) with ESMTP + id 5858D476E4E; Sat, 25 Jan 2003 01:46:01 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0P5eX5u006918; + Sat, 25 Jan 2003 00:40:33 -0500 (EST) +To: Kevin Brown +Cc: pgsql-performance@postgresql.org, pgsql-hackers@postgresql.org +Subject: WAL replay logic (was Re: [PERFORM] Mount options for Ext3?) +In-reply-to: <20030125041319.GE28252@filer> +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> <28176.1043457408@sss.pgh.pa.us> + <20030125021159.GC28252@filer> <1260.1043463535@sss.pgh.pa.us> + <20030125041319.GE28252@filer> +Comments: In-reply-to Kevin Brown + message dated "Fri, 24 Jan 2003 20:13:19 -0800" +Date: Sat, 25 Jan 2003 00:40:33 -0500 +Message-ID: <6917.1043473233@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/943 +X-Sequence-Number: 34553 + +Kevin Brown writes: +> One question I have is: in the event of a crash, why not simply replay +> all the transactions found in the WAL? Is the startup time of the +> database that badly affected if pg_control is ignored? + +Interesting thought, indeed. Since we truncate the WAL after each +checkpoint, seems like this approach would no more than double the time +for restart. The win is it'd eliminate pg_control as a single point of +failure. It's always bothered me that we have to update pg_control on +every checkpoint --- it should be a write-pretty-darn-seldom file, +considering how critical it is. + +I think we'd have to make some changes in the code for deleting old +WAL segments --- right now it's not careful to delete them in order. +But surely that can be coped with. + +OTOH, this might just move the locus for fatal failures out of +pg_control and into the OS' algorithms for writing directory updates. +We would have no cross-check that the set of WAL file names visible in +pg_xlog is sensible or aligned with the true state of the datafile area. +We'd have to take it on faith that we should replay the visible files +in their name order. This might mean we'd have to abandon the current +hack of recycling xlog segments by renaming them --- which would be a +nontrivial performance hit. + +Comments anyone? + +> If there exists somewhere a reasonably succinct description of the +> reasoning behind the current transaction management scheme (including +> an analysis of the pros and cons), I'd love to read it and quit +> bugging you. :-) + +Not that I know of. Would you care to prepare such a writeup? There +is a lot of material in the source-code comments, but no coherent +presentation. + + regards, tom lane + +From pgsql-hackers-owner@postgresql.org Sat Jan 25 03:00:03 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0AB66475EE4 + for ; + Sat, 25 Jan 2003 03:00:02 -0500 (EST) +Received: from platonic.cynic.net (platonic.cynic.net [204.80.150.245]) + by postgresql.org (Postfix) with ESMTP id 99932475E2B + for ; + Sat, 25 Jan 2003 02:59:59 -0500 (EST) +Received: from angelic.cynic.net (angelic-platonic.cvpn.cynic.net + [198.73.220.226]) by platonic.cynic.net (Postfix) with ESMTP + id DD1F2C005; Sat, 25 Jan 2003 07:59:51 +0000 (UTC) +Received: from localhost (localhost [127.0.0.1]) + by angelic.cynic.net (Postfix) with ESMTP + id 7644D8736; Sat, 25 Jan 2003 16:59:17 +0900 (JST) +Date: Sat, 25 Jan 2003 16:59:17 +0900 (JST) +From: Curt Sampson +To: Tom Lane +Cc: Kevin Brown , pgsql-hackers@postgresql.org +Subject: Re: WAL replay logic (was Re: [PERFORM] Mount options for Ext3?) +In-Reply-To: <6917.1043473233@sss.pgh.pa.us> +Message-ID: +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> + <28176.1043457408@sss.pgh.pa.us> <20030125021159.GC28252@filer> + <1260.1043463535@sss.pgh.pa.us> <20030125041319.GE28252@filer> + <6917.1043473233@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/944 +X-Sequence-Number: 34554 + +On Sat, 25 Jan 2003, Tom Lane wrote: + +> We'd have to take it on faith that we should replay the visible files +> in their name order. + +Couldn't you could just put timestamp information at the beginning if +each file, (or perhaps use that of the first transaction), and read the +beginning of each file to find out what order to run them in. Perhaps +you could even check the last transaction in each file as well to see if +there are "holes" between the available logs. + +> This might mean we'd have to abandon the current +> hack of recycling xlog segments by renaming them --- which would be a +> nontrivial performance hit. + +Rename and write a "this is an empty logfile" record at the beginning? +Though I don't see how you could do this in an atomic manner.... Maybe if +you included the filename in the WAL file header, you'd see that if the name +doesn't match the header, it's a recycled file.... + +(This response sent only to hackers.) + +cjs +-- +Curt Sampson +81 90 7737 2974 http://www.netbsd.org + Don't you know, in this new Dark Age, we're all light. --XTC + +From pgsql-hackers-owner@postgresql.org Sat Jan 25 05:11:22 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 76451475EC7; Sat, 25 Jan 2003 05:11:16 -0500 (EST) +Received: from filer (12-235-198-106.client.attbi.com [12.235.198.106]) + by postgresql.org (Postfix) with ESMTP + id 9737E475EE4; Sat, 25 Jan 2003 05:11:15 -0500 (EST) +Received: from localhost (localhost [127.0.0.1]) (uid 1000) + by filer with local; Sat, 25 Jan 2003 02:11:12 -0800 +Date: Sat, 25 Jan 2003 02:11:12 -0800 +From: Kevin Brown +To: pgsql-performance@postgresql.org, pgsql-hackers@postgresql.org +Subject: Re: WAL replay logic (was Re: [PERFORM] Mount options for Ext3?) +Message-ID: <20030125101111.GB12957@filer> +Mail-Followup-To: Kevin Brown , + pgsql-performance@postgresql.org, pgsql-hackers@postgresql.org +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> <28176.1043457408@sss.pgh.pa.us> + <20030125021159.GC28252@filer> <1260.1043463535@sss.pgh.pa.us> + <20030125041319.GE28252@filer> <6917.1043473233@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +In-Reply-To: <6917.1043473233@sss.pgh.pa.us> +User-Agent: Mutt/1.4i +Organization: Frobozzco International +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/945 +X-Sequence-Number: 34555 + +Tom Lane wrote: +> Kevin Brown writes: +> > One question I have is: in the event of a crash, why not simply replay +> > all the transactions found in the WAL? Is the startup time of the +> > database that badly affected if pg_control is ignored? +> +> Interesting thought, indeed. Since we truncate the WAL after each +> checkpoint, seems like this approach would no more than double the time +> for restart. + +Hmm...truncating the WAL after each checkpoint minimizes the amount of +disk space eaten by the WAL, but on the other hand keeping older +segments around buys you some safety in the event that things get +really hosed. But your later comments make it sound like the older +WAL segments are kept around anyway, just rotated. + +> The win is it'd eliminate pg_control as a single point of +> failure. It's always bothered me that we have to update pg_control on +> every checkpoint --- it should be a write-pretty-darn-seldom file, +> considering how critical it is. +> +> I think we'd have to make some changes in the code for deleting old +> WAL segments --- right now it's not careful to delete them in order. +> But surely that can be coped with. + +Even that might not be necessary. See below. + +> OTOH, this might just move the locus for fatal failures out of +> pg_control and into the OS' algorithms for writing directory updates. +> We would have no cross-check that the set of WAL file names visible in +> pg_xlog is sensible or aligned with the true state of the datafile +> area. + +Well, what we somehow need to guarantee is that there is always WAL +data that is older than the newest consistent data in the datafile +area, right? Meaning that if the datafile area gets scribbled on in +an inconsistent manner, you always have WAL data to fill in the gaps. + +Right now we do that by using fsync() and sync(). But I think it +would be highly desirable to be able to more or less guarantee +database consistency even if fsync were turned off. The price for +that might be too high, though. + +> We'd have to take it on faith that we should replay the visible files +> in their name order. This might mean we'd have to abandon the current +> hack of recycling xlog segments by renaming them --- which would be a +> nontrivial performance hit. + +It's probably a bad idea for the replay to be based on the filenames. +Instead, it should probably be based strictly on the contents of the +xlog segment files. Seems to me the beginning of each segment file +should have some kind of header information that makes it clear where +in the scheme of things it belongs. Additionally, writing some sort +of checksum, either at the beginning or the end, might not be a bad +idea either (doesn't have to be a strict checksum, but it needs to be +something that's reasonably likely to catch corruption within a +segment). + +Do that, and you don't have to worry about renaming xlog segments at +all: you simply move on to the next logical segment in the list (a +replay just reads the header info for all the segments and orders the +list as it sees fit, and discards all segments prior to any gap it +finds. It may be that you simply have to bail out if you find a gap, +though). As long as the xlog segment checksum information is +consistent with the contents of the segment and as long as its +transactions pick up where the previous segment's left off (assuming +it's not the first segment, of course), you can safely replay the +transactions it contains. + +I presume we're recycling xlog segments in order to avoid file +creation and unlink overhead? Otherwise you can simply create new +segments as needed and unlink old segments as policy dictates. + +> Comments anyone? +> +> > If there exists somewhere a reasonably succinct description of the +> > reasoning behind the current transaction management scheme (including +> > an analysis of the pros and cons), I'd love to read it and quit +> > bugging you. :-) +> +> Not that I know of. Would you care to prepare such a writeup? There +> is a lot of material in the source-code comments, but no coherent +> presentation. + +Be happy to. Just point me to any non-obvious source files. + +Thus far on my plate: + + 1. PID file locking for postmaster startup (doesn't strictly need + to be the PID file but it may as well be, since we're already + messing with it anyway). I'm currently looking at how to do + the autoconf tests, since I've never developed using autoconf + before. + + 2. Documenting the transaction management scheme. + +I was initially interested in implementing the explicit JOIN +reordering but based on your recent comments I think you have a much +better handle on that than I. I'll be very interested to see what you +do, to see if it's anything close to what I figure has to happen... + + +-- +Kevin Brown kevin@sysexperts.com + +From pgsql-performance-owner@postgresql.org Sat Jan 25 10:20:53 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E107C475C14 + for ; + Sat, 25 Jan 2003 10:20:50 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 67852476179 + for ; + Sat, 25 Jan 2003 10:20:45 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18cS6z-0003lF-00 + for ; Sat, 25 Jan 2003 10:20:49 -0500 +Date: Sat, 25 Jan 2003 10:20:49 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +Message-ID: <20030125102049.A14300@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> + <3E3158DA.7080807@mochima.com> <22650.1043442101@sss.pgh.pa.us> + <3E31DA80.7000000@mochima.com> <28204.1043457542@sss.pgh.pa.us> + <28260.1043458181@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <28260.1043458181@sss.pgh.pa.us>; + from tgl@sss.pgh.pa.us on Fri, Jan 24, 2003 at 08:29:41PM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/327 +X-Sequence-Number: 974 + +On Fri, Jan 24, 2003 at 08:29:41PM -0500, Tom Lane wrote: +> auxww (or ps -ef on SysV-ish platforms) to see what all the backends are + +Except Solaris, where ps -ef gives you no information at all. Use +/usr/ucb/ps -auxww. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Sat Jan 25 10:23:57 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E26F8475D22 + for ; + Sat, 25 Jan 2003 10:23:54 -0500 (EST) +Received: from VL-MS-MR001.sc1.videotron.ca (relais.videotron.ca + [24.201.245.36]) + by postgresql.org (Postfix) with ESMTP id 4CF32475CED + for ; + Sat, 25 Jan 2003 10:23:54 -0500 (EST) +Received: from mochima.com ([66.131.15.233]) by VL-MS-MR001.sc1.videotron.ca + (iPlanet Messaging Server 5.2 HotFix 0.9 (built Jul 29 2002)) + with ESMTP id <0H9A0068F049WE@VL-MS-MR001.sc1.videotron.ca> for + pgsql-performance@postgresql.org; Sat, 25 Jan 2003 10:24:09 -0500 (EST) +Date: Sat, 25 Jan 2003 10:22:51 -0500 +From: Carlos Moreno +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +To: PgSQL Performance ML +Message-id: <3E32ABCB.6070003@mochima.com> +MIME-version: 1.0 +Content-type: text/plain; charset=us-ascii; format=flowed +Content-transfer-encoding: 7BIT +X-Accept-Language: en-us +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:0.9.4.1) + Gecko/20020508 Netscape6/6.2.3 +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> <3E3158DA.7080807@mochima.com> + <22650.1043442101@sss.pgh.pa.us> <3E31DA80.7000000@mochima.com> + <28204.1043457542@sss.pgh.pa.us> <28260.1043458181@sss.pgh.pa.us> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/328 +X-Sequence-Number: 975 + + +Tom Lane wrote: + +>I said: +> +>>Carlos Moreno writes: +>> +>>>One quick question, Tom, before some general comments and +>>>reply to the other messages... Where would I specify any +>>>locks the software wants to do? +>>> +> +>>If you are not issuing any explicit "LOCK" SQL commands, then you can +>>disregard my theory. +>> + +Well, it was a good thing that you brought it to my attention. +Yes, two minutes after I wrote the message I found the docs +that told me it is an SQL command -- which means that I'm +positively sure that I'm not doing any of those :-) I guess +a well-developed software could use some locks here and there, +and the risk of making a mistake and "over-blocking" things is +there... + + + +>>Actually, that's too simple. Are you creating and dropping tables, +>>or issuing schema-change commands (such as ADD COLUMN or RENAME)? +>>All of those things take exclusive locks on the tables they modify. +>>Ordinary SELECT/INSERT/UPDATE/DELETE operations can run in parallel with +>>pg_dump, but messing with the database structure is another story. +>> + + +I do that (changing the database schema while the system is +running) once in a while -- but not on a regular basis, and +definitely never during the time a pg_dump is in progress +(*that* would have scared me to death ;-)) + + +> +>I guess the real question here is whether your app is actually stopped +>dead (as it would be if waiting for a lock), or just slowed to a crawl +>(as a performance problem could do). I cannot tell if your "frozen" +>description is hyperbole or literal truth. +> + +Actually, you got me on that one... From the "practical" point of +view, you could say it's literal truth (i.e., the system responsiveness +falls to ZERO). The system is an online multi-player game, where the +main things the database is doing is holding the users information +to process the login authentications, and logging results and the +progress of games (to later -- offline -- compute statistics, +rankings, etc.). Logging is done on a separate worker thread, so +it shouldn't matter if that stops for a few minutes (the lists of +SQL's pending to be executed would just grow during that time)... + +But the thing is, when I run pg_dump, the games freeze, you are +absolutely unable to connect (the server does not respond, period), +and the players that are in a game, playing, massively abandon +games, and you then see comments in the chat window that the +server went down, etc. (i.e., I take it the server stopped +responding to them and they abandoned thinking that the connection +had dropped, or that the server had died). + +Now, I guess a more specific answer to your question is important +(i.e., is the above behaviour the result of the system slowing to +a crawl, or is it that the software just hung on a single db.Exec +statement in the main loop and no single line of code is being +executed until the pg_dump finishes? -- according to the comments +so far, I would say this last option is not possible), and I think +I'll get such an answer when running some tests as suggested by you +and others that replied. + +>One thing that might help diagnose it is to look at the output of ps +>auxww (or ps -ef on SysV-ish platforms) to see what all the backends are +>currently doing while the problem exists. +> + +We have done (IIRC) top (the command "top", that is), and yes, the +postmaster process takes a lot of CPU... (not sure of the exact +numbers, but it was at the top). + +Anyway, thanks again guys for the valuable comments and ideas!! + +Carlos +-- + + + + + +From pgsql-hackers-owner@postgresql.org Sat Jan 25 11:16:24 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9C0FC475CED + for ; + Sat, 25 Jan 2003 11:16:22 -0500 (EST) +Received: from sss.pgh.pa.us (sss-backup.pgh.pa.us [216.151.103.158]) + by postgresql.org (Postfix) with ESMTP id 3F511475CB4 + for ; + Sat, 25 Jan 2003 11:16:21 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0PGGC5u010918; + Sat, 25 Jan 2003 11:16:12 -0500 (EST) +To: Curt Sampson +Cc: Kevin Brown , pgsql-hackers@postgresql.org +Subject: Re: WAL replay logic (was Re: [PERFORM] Mount options for Ext3?) +In-reply-to: +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> <28176.1043457408@sss.pgh.pa.us> + <20030125021159.GC28252@filer> <1260.1043463535@sss.pgh.pa.us> + <20030125041319.GE28252@filer> <6917.1043473233@sss.pgh.pa.us> + +Comments: In-reply-to Curt Sampson + message dated "Sat, 25 Jan 2003 16:59:17 +0900" +Date: Sat, 25 Jan 2003 11:16:12 -0500 +Message-ID: <10916.1043511372@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/946 +X-Sequence-Number: 34556 + +Curt Sampson writes: +> On Sat, 25 Jan 2003, Tom Lane wrote: +>> We'd have to take it on faith that we should replay the visible files +>> in their name order. + +> Couldn't you could just put timestamp information at the beginning if +> each file, + +Good thought --- there's already an xlp_pageaddr field on every page +of WAL, and you could examine that to be sure it matches the file name. +If not, the file csn be ignored. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Sat Jan 25 12:17:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E7FF9475BF9 + for ; + Sat, 25 Jan 2003 12:17:05 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 3266A475AD4 + for ; + Sat, 25 Jan 2003 12:17:05 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18cTva-0005Z4-00 + for ; Sat, 25 Jan 2003 12:17:10 -0500 +Date: Sat, 25 Jan 2003 12:17:10 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: Having trouble with backups (was: Re: Crash Recovery) +Message-ID: <20030125121710.F20026@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <2147483647.1043361178@[10.0.1.133]> + <1043416377.29437.70.camel@haggis> + <3E3158DA.7080807@mochima.com> <22650.1043442101@sss.pgh.pa.us> + <3E31DA80.7000000@mochima.com> <28204.1043457542@sss.pgh.pa.us> + <28260.1043458181@sss.pgh.pa.us> <3E32ABCB.6070003@mochima.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <3E32ABCB.6070003@mochima.com>; + from moreno@mochima.com on Sat, Jan 25, 2003 at 10:22:51AM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/329 +X-Sequence-Number: 976 + +On Sat, Jan 25, 2003 at 10:22:51AM -0500, Carlos Moreno wrote: + +> Well, it was a good thing that you brought it to my attention. +> Yes, two minutes after I wrote the message I found the docs +> that told me it is an SQL command -- which means that I'm +> positively sure that I'm not doing any of those :-) I guess + +If you have a lot of foreign keys and are doing long-running UPDATES +(or other related things), I think you might also see the same thing. +You could spot this with ps -auxww (or friends) by looking for [some +db operation] waiting. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Sat Jan 25 13:44:14 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B6BB1475D1C + for ; + Sat, 25 Jan 2003 13:44:12 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id F3146475BF9 + for ; + Sat, 25 Jan 2003 13:44:11 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18cVHo-0006nM-00 + for ; Sat, 25 Jan 2003 13:44:12 -0500 +Date: Sat, 25 Jan 2003 13:44:12 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: WEIRD CRASH?!?! +Message-ID: <20030125134412.K20026@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <200301241603.42263.josh@agliodbs.com> + <22021C37-2FF9-11D7-A3A3-000393AA8F3C@allresearch.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <22021C37-2FF9-11D7-A3A3-000393AA8F3C@allresearch.com>; + from noah@allresearch.com on Fri, Jan 24, 2003 at 07:08:29PM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/330 +X-Sequence-Number: 977 + +On Fri, Jan 24, 2003 at 07:08:29PM -0500, Noah Silverman wrote: +> Yes, +> but I'm the only one logged into this box, and I didn't kill anything. +> It appears to have died all by itself. + +Is this on Linux, and were you short on memory? Linux, in a +completely brain-dead design, runs around 'kill -9'-ing random +processes when it starts to think the machine is going to exhaust its +memory (or at least it used to. I dunno if it still does). + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Sat Jan 25 13:57:41 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E4A23475AD4 + for ; + Sat, 25 Jan 2003 13:57:38 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 2BA3C474E61 + for ; + Sat, 25 Jan 2003 13:57:38 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030125185735.QHYY8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Sat, 25 Jan 2003 13:57:35 -0500 +Subject: LOCK TABLE & speeding up mass data loads +From: Ron Johnson +To: PgSQL Performance ML +Content-Type: text/plain +Organization: +Message-Id: <1043521053.818.32.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 25 Jan 2003 12:57:33 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/331 +X-Sequence-Number: 978 + +Hi, + +Would LOCK TABLE ACCESS EXCLUSIVE MODE speed things up, when I have +a script that loads data by setting transactions, and then committing +works after every few thousand INSERTs? + +Thanks, +Ron +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Sat Jan 25 14:07:38 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B6A6C475AD4 + for ; + Sat, 25 Jan 2003 14:07:36 -0500 (EST) +Received: from jester.senspire.com + (CPE00508b028d7d-CM00803785c5e0.cpe.net.cable.rogers.com + [24.103.51.175]) + by postgresql.org (Postfix) with ESMTP id CE468474E61 + for ; + Sat, 25 Jan 2003 14:07:35 -0500 (EST) +Received: from [127.0.0.1] (localhost [127.0.0.1]) + by jester.senspire.com (8.12.6/8.12.6) with ESMTP id h0PJ7kqu081649; + Sat, 25 Jan 2003 14:07:46 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: LOCK TABLE & speeding up mass data loads +From: Rod Taylor +To: Ron Johnson +Cc: PgSQL Performance ML +In-Reply-To: <1043521053.818.32.camel@haggis> +References: <1043521053.818.32.camel@haggis> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-SoMw60ebdgyBE0D1x2w5" +Organization: +Message-Id: <1043521665.58142.135.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 25 Jan 2003 14:07:46 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/332 +X-Sequence-Number: 979 + +--=-SoMw60ebdgyBE0D1x2w5 +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +On Sat, 2003-01-25 at 13:57, Ron Johnson wrote: +> Hi, +>=20 +> Would LOCK TABLE ACCESS EXCLUSIVE MODE speed things up, when I have +> a script that loads data by setting transactions, and then committing +> works after every few thousand INSERTs? + +If you're the only person working on the database, then no. If you're +fighting for resources with a bunch of other people -- then possibly, +but the others won't get anything done during this timeframe (of +course). + +Oh, and you're using COPY right? + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-SoMw60ebdgyBE0D1x2w5 +Content-Type: application/pgp-signature; name=signature.asc +Content-Description: This is a digitally signed message part + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (FreeBSD) + +iD8DBQA+MuCB6DETLow6vwwRAsQeAJ97EljImU0a+5PVu8zynHY+xg6kqgCfZU9F +rqHwa5faLDcJkakZX0gOMbI= +=cJNP +-----END PGP SIGNATURE----- + +--=-SoMw60ebdgyBE0D1x2w5-- + + +From pgsql-performance-owner@postgresql.org Sat Jan 25 14:19:12 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 05B2F475BF9 + for ; + Sat, 25 Jan 2003 14:19:11 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 1D9F3475AD4 + for ; + Sat, 25 Jan 2003 14:19:10 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030125191911.QNEL8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Sat, 25 Jan 2003 14:19:11 -0500 +Subject: Re: LOCK TABLE & speeding up mass data loads +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <1043521665.58142.135.camel@jester> +References: <1043521053.818.32.camel@haggis> + <1043521665.58142.135.camel@jester> +Content-Type: text/plain +Organization: +Message-Id: <1043522349.818.36.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 25 Jan 2003 13:19:09 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/333 +X-Sequence-Number: 980 + +On Sat, 2003-01-25 at 13:07, Rod Taylor wrote: +> On Sat, 2003-01-25 at 13:57, Ron Johnson wrote: +> > Hi, +> > +> > Would LOCK TABLE ACCESS EXCLUSIVE MODE speed things up, when I have +> > a script that loads data by setting transactions, and then committing +> > works after every few thousand INSERTs? +> +> If you're the only person working on the database, then no. If you're +> fighting for resources with a bunch of other people -- then possibly, +> but the others won't get anything done during this timeframe (of +> course). + +Ok. + +> Oh, and you're using COPY right? + +No. Too much data manipulation to do 1st. Also, by committing every +X thousand rows, then if the process must be aborted, then there's +no huge rollback, and the script can then skip to the last comitted +row and pick up from there. + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Sat Jan 25 18:21:57 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 98644475E52 + for ; + Sat, 25 Jan 2003 18:21:54 -0500 (EST) +Received: from mail2.mediadesign.nl (md2.mediadesign.nl [212.19.205.67]) + by postgresql.org (Postfix) with SMTP id 7DC55475E14 + for ; + Sat, 25 Jan 2003 18:21:53 -0500 (EST) +Received: (qmail 13771 invoked by uid 666); 25 Jan 2003 23:21:54 -0000 +Date: Sun, 26 Jan 2003 00:21:54 +0100 +From: pgsql.spam@vinz.nl +To: pgsql-performance@postgresql.org +Subject: Re: Mount options for Ext3? +Message-ID: <20030125232154.GK14898@md2.mediadesign.nl> +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> <28176.1043457408@sss.pgh.pa.us> + <20030125021159.GC28252@filer> <1260.1043463535@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <1260.1043463535@sss.pgh.pa.us> +User-Agent: Mutt/1.3.28i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/334 +X-Sequence-Number: 981 + +On 2003-01-24 21:58:55 -0500, Tom Lane wrote: +> The key assumption we are making about the filesystem's behavior is that +> writes scheduled by the sync() will occur before the pg_control write +> that's issued after it. People have occasionally faulted this algorithm +> by quoting the sync() man page, which saith (in the Gospel According To +> HP) +> +> The writing, although scheduled, is not necessarily complete upon +> return from sync. +> +> This, however, is not a problem in itself. What we need to know is +> whether the filesystem will allow writes issued after the sync() to +> complete before those "scheduled" by the sync(). +> + +Certain linux 2.4.* kernels (not sure which, newer ones don't seem to have +it) have the following kernel config option: + +Use the NOOP Elevator (WARNING) +CONFIG_BLK_DEV_ELEVATOR_NOOP + If you are using a raid class top-level driver above the ATA/IDE core, + one may find a performance boost by preventing a merging and re-sorting + of the new requests. + + If unsure, say N. + +If one were certain his OS wouldn't do any re-ordering of writes, would it be +safe to run with fsync = off? (not that I'm going to try this, but I'm just +curious) + + +Vincent van Leeuwen +Media Design + +From pgsql-hackers-owner@postgresql.org Sun Jan 26 00:27:53 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 2B385475E4D; Sun, 26 Jan 2003 00:27:51 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP + id 68405475D91; Sun, 26 Jan 2003 00:27:50 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0Q5Rp5u026546; + Sun, 26 Jan 2003 00:27:52 -0500 (EST) +To: josh@agliodbs.com +Cc: pgsql-hackers@postgreSQL.org, pgsql-performance@postgreSQL.org +Subject: Re: [PERFORM] Proposal: relaxing link between explicit JOINs and + execution order +In-reply-to: <200301221617.41680.josh@agliodbs.com> +References: <25071.1043276513@sss.pgh.pa.us> + <200301221617.41680.josh@agliodbs.com> +Comments: In-reply-to Josh Berkus + message dated "Wed, 22 Jan 2003 16:17:41 -0800" +Date: Sun, 26 Jan 2003 00:27:51 -0500 +Message-ID: <26545.1043558871@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/968 +X-Sequence-Number: 34578 + +Josh Berkus writes: +> How about: +> EXPLICIT_JOIN_MINIMUM +> and +> FROM_COLLAPSE_LIMIT + +I've implemented this using FROM_COLLAPSE_LIMIT and JOIN_COLLAPSE_LIMIT +as the variable names. It'd be easy enough to change if someone comes +up with better names. You can read updated documentation at +http://developer.postgresql.org/docs/postgres/explicit-joins.html + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Sun Jan 26 00:35:31 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id AFB414764CF + for ; + Sun, 26 Jan 2003 00:35:29 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id ADE38476902 + for ; + Sun, 26 Jan 2003 00:34:43 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0Q5Ym5u026593; + Sun, 26 Jan 2003 00:34:48 -0500 (EST) +To: pgsql@vinz.nl +Cc: pgsql-performance@postgresql.org +Subject: Re: Mount options for Ext3? +In-reply-to: <20030125232154.GK14898@md2.mediadesign.nl> +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> <28176.1043457408@sss.pgh.pa.us> + <20030125021159.GC28252@filer> <1260.1043463535@sss.pgh.pa.us> + <20030125232154.GK14898@md2.mediadesign.nl> +Comments: In-reply-to pgsql.spam@vinz.nl + message dated "Sun, 26 Jan 2003 00:21:54 +0100" +Date: Sun, 26 Jan 2003 00:34:48 -0500 +Message-ID: <26592.1043559288@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/336 +X-Sequence-Number: 983 + +pgsql.spam@vinz.nl writes: +> If one were certain his OS wouldn't do any re-ordering of writes, would it be +> safe to run with fsync = off? (not that I'm going to try this, but I'm just +> curious) + +I suppose so ... but if your OS doesn't do *any* re-ordering of writes, +I'd say you need a better OS. Even in Postgres, we'd often like the OS +to collapse multiple writes of the same disk page into one write. And +we certainly want the various writes forced by a sync() to be done with +some intelligence about disk layout, not blindly in order of issuance. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Sun Jan 26 03:04:51 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9ABED475E3E + for ; + Sun, 26 Jan 2003 03:04:49 -0500 (EST) +Received: from lakemtao01.cox.net (lakemtao01.cox.net [68.1.17.244]) + by postgresql.org (Postfix) with ESMTP id B0E0A475E23 + for ; + Sun, 26 Jan 2003 03:04:48 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao01.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030126080448.WIXR16369.lakemtao01.cox.net@[192.168.1.1]> + for ; + Sun, 26 Jan 2003 03:04:48 -0500 +Subject: Re: Mount options for Ext3? +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <26592.1043559288@sss.pgh.pa.us> +References: <200301241120.14404.josh@agliodbs.com> + <20030125003011.GA28252@filer> <28176.1043457408@sss.pgh.pa.us> + <20030125021159.GC28252@filer> <1260.1043463535@sss.pgh.pa.us> + <20030125232154.GK14898@md2.mediadesign.nl> + <26592.1043559288@sss.pgh.pa.us> +Content-Type: text/plain +Organization: +Message-Id: <1043568285.818.241.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 26 Jan 2003 02:04:45 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/337 +X-Sequence-Number: 984 + +On Sat, 2003-01-25 at 23:34, Tom Lane wrote: +> pgsql.spam@vinz.nl writes: +> > If one were certain his OS wouldn't do any re-ordering of writes, would it be +> > safe to run with fsync = off? (not that I'm going to try this, but I'm just +> > curious) +> +> I suppose so ... but if your OS doesn't do *any* re-ordering of writes, +> I'd say you need a better OS. Even in Postgres, we'd often like the OS +> to collapse multiple writes of the same disk page into one write. And +> we certainly want the various writes forced by a sync() to be done with +> some intelligence about disk layout, not blindly in order of issuance. + +And anyway, wouldn't SCSI's Tagged Command Queueing override it all, +no matter if the OS did re-ordering or not? + +But then, it really means it when it says that fsync() succeeds, so does +TCQ matter in this case? + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Sun Jan 26 16:24:05 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E1EE44758C9 + for ; + Sun, 26 Jan 2003 16:24:03 -0500 (EST) +Received: from smtp.enternet.hu (smtp.enternet.hu [62.112.192.21]) + by postgresql.org (Postfix) with ESMTP id 0310D475843 + for ; + Sun, 26 Jan 2003 16:24:03 -0500 (EST) +Received: from localhost.localdomain (maci@3e70db28.adsl.enternet.hu + [62.112.219.40]) + by smtp.enternet.hu (8.12.6/8.12.6) with ESMTP id h0QLNwrb036283 + for ; + Sun, 26 Jan 2003 22:23:59 +0100 (CET) + (envelope-from eire@enternet.hu) +Subject: bigserial vs serial - which one I'd have to use? +From: Medve Gabor +To: pgsql-performance@postgresql.org +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +X-Mailer: Ximian Evolution 1.0.5 +Date: 26 Jan 2003 22:24:41 +0100 +Message-Id: <1043616281.829.38.camel@maci> +Mime-Version: 1.0 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/338 +X-Sequence-Number: 985 + +Hi all, + +Have you got any data (ie in percentage) of around how much more CPU +work needed with the bigserial type in the queries? + +I have a log database with 100million records (the biggest table +contains 65million records) and I use bigserial data type as primary key +now. The primary key looks this way: YYYYMMDD1xxxxxxx where the first 8 +numbers are the date, and the x's are the record sequence number on that +day. This way the records are in ascendant order. Almost all of the +queries contains date constraints (PK like 'YYYYMMDD%'). I'd like to +know if I do it in a stupid way or not. I'm not a DBA expert so every +idea are welcome. If you need more information about the +hardware/software environment, the DB structure then I'll post them. + +Thanks in advance for your help. + +Gabor + + +From pgsql-performance-owner@postgresql.org Sun Jan 26 18:10:33 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B0F7E475843 + for ; + Sun, 26 Jan 2003 18:10:32 -0500 (EST) +Received: from platonic.cynic.net (platonic.cynic.net [204.80.150.245]) + by postgresql.org (Postfix) with ESMTP id 37C4C47580B + for ; + Sun, 26 Jan 2003 18:10:32 -0500 (EST) +Received: from angelic.cynic.net (angelic-platonic.cvpn.cynic.net + [198.73.220.226]) by platonic.cynic.net (Postfix) with ESMTP + id 75C14C003; Sun, 26 Jan 2003 23:10:32 +0000 (UTC) +Received: from localhost (localhost [127.0.0.1]) + by angelic.cynic.net (Postfix) with ESMTP + id 471418736; Mon, 27 Jan 2003 08:10:09 +0900 (JST) +Date: Mon, 27 Jan 2003 08:10:09 +0900 (JST) +From: Curt Sampson +To: Ron Johnson +Cc: PgSQL Performance ML +Subject: Re: LOCK TABLE & speeding up mass data loads +In-Reply-To: <1043522349.818.36.camel@haggis> +Message-ID: +References: <1043521053.818.32.camel@haggis> + <1043521665.58142.135.camel@jester> + <1043522349.818.36.camel@haggis> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/339 +X-Sequence-Number: 986 + +On Sun, 25 Jan 2003, Ron Johnson wrote: + +> > Oh, and you're using COPY right? +> +> No. Too much data manipulation to do 1st. Also, by committing every +> X thousand rows, then if the process must be aborted, then there's +> no huge rollback, and the script can then skip to the last comitted +> row and pick up from there. + +I don't see how the amount of data manipulation makes a difference. +Where you now issue a BEGIN, issue a COPY instead. Where you now INSERT, +just print the data for the columns, separated by tabs. Where you now +issue a COMMIT, end the copy. + +cjs +-- +Curt Sampson +81 90 7737 2974 http://www.netbsd.org + Don't you know, in this new Dark Age, we're all light. --XTC + +From pgsql-general-owner@postgresql.org Sun Jan 26 19:54:52 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 9DF224761DD; Sun, 26 Jan 2003 19:54:50 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP + id 40915476128; Sun, 26 Jan 2003 19:54:49 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id h0R0sP721325; + Sun, 26 Jan 2003 19:54:25 -0500 (EST) +From: Bruce Momjian +Message-Id: <200301270054.h0R0sP721325@candle.pha.pa.us> +Subject: Re: [PERFORM] optimizing query +In-Reply-To: <25976.1043335579@sss.pgh.pa.us> +To: Tom Lane +Date: Sun, 26 Jan 2003 19:54:25 -0500 (EST) +Cc: Chantal Ackermann , + Stephan Szabo , + pgsql-general@postgresql.org, pgsql-performance@postgresql.org +X-Mailer: ELM [version 2.4ME+ PL99 (25)] +MIME-Version: 1.0 +Content-Transfer-Encoding: 7bit +Content-Type: text/plain; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/1102 +X-Sequence-Number: 36223 + +Tom Lane wrote: +> > postgresql.conf: +> > shared_buffers: 121600 +> > max_connections: 64 +> > max_fsm_relations = 200 +> > max_fsm_pages = 40000 +> > effective_cache_size = 8000 +> +> Try increasing sort_mem. +> +> Also, I'd back off on shared_buffers if I were you. There's no evidence +> that values above a few thousand buy anything. + +Increasing shared_buffers above several thousand will only be a win if +your entire working set will fit in the larger buffer pool, but didn't +in the previous size. If you working set is smaller or larger than +that, pushing it above several thousand isn't a win. Is that a more +definitive answer? + +-- + 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 Jan 27 03:18:22 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 77D12475425 + for ; + Mon, 27 Jan 2003 03:18:20 -0500 (EST) +Received: from perrin.int.nxad.com (internal.ext.nxad.com [66.250.180.251]) + by postgresql.org (Postfix) with ESMTP id 49F07476A02 + for ; + Mon, 27 Jan 2003 03:18:15 -0500 (EST) +Received: by perrin.int.nxad.com (Postfix, from userid 1001) + id 55B4220F01; Mon, 27 Jan 2003 00:17:45 -0800 (PST) +Date: Mon, 27 Jan 2003 00:17:45 -0800 +From: Sean Chittenden +To: Tom Lane +Cc: Jeff , Bruce Momjian , + Josh Berkus , Roman Fail , + "sszabo@megazone23.bigpanda.com" , + "pgsql-performance@postgresql.org" +Subject: Re: 7.3.1 New install, large queries are slow +Message-ID: <20030127081745.GK15936@perrin.int.nxad.com> +References: + <21623.1042865371@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <21623.1042865371@sss.pgh.pa.us> +User-Agent: Mutt/1.4i +X-PGP-Key: finger seanc@FreeBSD.org +X-PGP-Fingerprint: 6CEB 1B06 BFD3 70F6 95BE 7E4D 8E85 2E0A 5F5B 3ECB +X-Web-Homepage: http://sean.chittenden.org/ +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/341 +X-Sequence-Number: 988 + +> >> Yeah, but isn't that theory a hangover from pre-Unix operating systems? +> +> > Informix, oracle, etc all do raw device access bypassing the kernels +> > buffering, etc. So they need heaping gobules of memory to do the same +> > thing the kernel does.. +> +> D'oh, I believe Jeff's put his finger on it. You need lotsa RAM if you +> are trying to bypass the OS. But Postgres would like to work with the +> OS, not bypass it. +> +> > but since they know the exact patterns of data and +> > how things will be done they can fine tune their buffer caches to get much +> > better performance than the kernel (15-20% in informix's case) since the +> > kernel needs to be a "works good generally" +> +> They go to all that work for 15-20% ??? Remind me not to follow that +> primrose path. I can think of lots of places where we can buy 20% for +> less work than implementing (and maintaining) our own raw-device access +> layer. + +This is related somewhat to the raw device access discussion. This is +a quote from Matt Dillion (FreeBSD VM guru) on the topic of disk +caches (Message-Id: +<200301270657.h0R6v2qH071774@apollo.backplane.com>) and a few bits at +the end: + + +### Begin quote + Mmmmm. Basically what it comes down to is that without foreknowledge + of the data locations being accessed, it is not possible for any + cache algorithm to adapt to all the myriad ways data might be accessed. + If you focus the cache on one methodology it will probably perform + terribly when presented with some other methodology. + + What this means is that for the cases where you *KNOW* how a program + intends to access a dataset larger then main memory, it is better + to have the program explicitly cache/not-cache the data under program + control rather then trying to force the system cache to adapt. + + I'll also be nice and decode some of Terry's Jargon for the rest of + the readers. + +:will result in significant failure of random page replacement to +:result in cache hits; likewise, going to 85% overage will practically +:guarantee an almost 100% failure rate, as cyclical access with random +:replacement is statistically more likely, in aggregate, to replace +:the pages which are there longer (the probability is iterative and +:additive: it's effectively a permutation). + + What Terry is saying is that if you have a dataset that is 2x + the size of your cache, the cache hit rate on that data with random + page replacement is NOT going to be 50%. This is because with random + page replacement the likelihood of a piece of data being found in + the cache depends on how long the data has been sitting in the cache. + The longer the data has been sitting in the cache, the less likely you + will find it when you need it (because it is more likely to have been + replaced by the random replacement algorithm over time). + + So, again, the best caching methodology to use in the case where + you *know* how much data you will be accessing and how you will access + it is to build the caching directly into your program and not depend + on system caching at all (for datasets which are far larger then + main memory). + + This is true of all systems, not just BSD. This is one reason why + databases do their own caching (another is so databases know when an + access will require I/O for scheduling reasons, but that's a different + story). + + The FreeBSD VM caching system does prevent one process from exhausting + another process's cached data due to a sequential access, but the + FreeBSD VM cache does not try to outsmart sequential data accesses to + datasets which are larger then available cache space because it's an + insanely difficult (impossible) problem to solve properly without + foreknowledge of what data elements will be accessed when. + + This isn't to say that we can't improve on what we have now. + I certainly think we can. But there is no magic bullet that will + deal with every situation. + + -Matt +### End quote + +So if there really is only a 15-20% performance gain to be had from +using raw disk access, that 15-20% loss comes from not being able to +tell the OS what to cache, what not to cache, and what order to have +the pages in... which only really matters if there is RAM available to +the kernel to cache, and that it is able to determine what is valuable +to cache in the course of its operations. Predictive caching by the +OS isn't done because it understands PostgreSQL, because it +understands a generic algorithm for page hits/misses. + +What is interesting after reading this, however, is the prospect of a +15-20% speed up on certain tables that we know are accessed frequently +by implicitly specifying a set of data to be preferred in a user space +cache. It's impossible for the OS to cache the pages that make the +biggest impact on user visible performance given the OS has no +understanding of what pages make a big difference on user visible +performance, a user land database process, however, would. + +As things stand, it's entirely possible for a set of large queries to +come through and wipe the kernel's cache that smaller queries were +using. Once a cache misses, the kernel then has to fetch the data +again which could slow down over all number of transactions per +second. That said, this is something that an in-database scheduler +could avoid by placing a lower priority on larger, more complex +queries with the assumption being that having the smaller queries +continue to process and get in/out is more important than shaving a +few seconds off of a larger query that would deplete the cache used by +the smaller queries. Oh to be a DBA and being able to make those +decisions instead of the kernel... + +Hrm, so two ideas or questions come to mind: + +1) On some of my really large read only queries, it would be SUUUPER + nice to be able to re-nice the process from SQL land to 5, 10, or + even 20. IIRC, BSD's VM system is smart enough to prevent lower + priority jobs from monopolizing the disk cache, which would let the + smaller faster turn around queries, continue to exist with their + data in the kernel's disk cache. (some kind of query complexity + threshold that results in a reduction of priority or an explicit + directive to run at a lower priority) + +2) Is there any way of specifying that a particular set of tables + should be kept in RAM or some kind of write through cache? I know + data is selected into a backend out of the catalogs, but would it + be possible to have them kept in memory and only re-read on change + with some kind of semaphore? Now that all system tables are in + their own schemas (pg_catalog and pg_toast), would it be hard to + set a flag on a change to those tables that would cause the + postmaster, or children, to re-read then instead of rely on their + cache? With copy-on-write forking, this could be pretty efficient + if the postmaster did this and forked off a copy with the tables + already in memory instead of on disk. + +Just a few ideas/ramblings, hope someone finds them interesting... the +renice function is one that I think I'll spend some time looking into +here shortly actually. -sc + +-- +Sean Chittenden + +From pgsql-performance-owner@postgresql.org Mon Jan 27 04:08:32 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3E39D475E3A + for ; + Mon, 27 Jan 2003 04:08:29 -0500 (EST) +Received: from lakemtao01.cox.net (lakemtao01.cox.net [68.1.17.244]) + by postgresql.org (Postfix) with ESMTP id 8613B475425 + for ; + Mon, 27 Jan 2003 04:08:28 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao01.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030127090829.IXJQ16369.lakemtao01.cox.net@[192.168.1.1]> + for ; + Mon, 27 Jan 2003 04:08:29 -0500 +Subject: Re: LOCK TABLE & speeding up mass data loads +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: +References: <1043521053.818.32.camel@haggis> + <1043521665.58142.135.camel@jester> <1043522349.818.36.camel@haggis> + +Content-Type: text/plain +Organization: +Message-Id: <1043658500.818.398.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 27 Jan 2003 03:08:20 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/342 +X-Sequence-Number: 989 + +On Sun, 2003-01-26 at 17:10, Curt Sampson wrote: +> On Sun, 25 Jan 2003, Ron Johnson wrote: +> +> > > Oh, and you're using COPY right? +> > +> > No. Too much data manipulation to do 1st. Also, by committing every +> > X thousand rows, then if the process must be aborted, then there's +> > no huge rollback, and the script can then skip to the last comitted +> > row and pick up from there. +> +> I don't see how the amount of data manipulation makes a difference. +> Where you now issue a BEGIN, issue a COPY instead. Where you now INSERT, +> just print the data for the columns, separated by tabs. Where you now +> issue a COMMIT, end the copy. + +Yes, create an input file for COPY. Great idea. + +However, If I understand you correctly, then if I want to be able +to not have to roll-back and re-run and complete COPY (which may +entail millions of rows), then I'd have to have thousands of seperate +input files (which would get processed sequentially). + +Here's what I'd like to see: +COPY table [ ( column [, ...] ) ] + FROM { 'filename' | stdin } + [ [ WITH ] + [ BINARY ] + [ OIDS ] + [ DELIMITER [ AS ] 'delimiter' ] + [ NULL [ AS ] 'null string' ] ] + [COMMIT EVERY ... ROWS WITH LOGGING] <<<<<<<<<<<<< + [SKIP ... ROWS] <<<<<<<<<<<<< + +This way, if I'm loading 25M rows, I can have it commit every, say, +1000 rows, and if it pukes 1/2 way thru, then when I restart the +COPY, it can SKIP past what's already been loaded, and proceed apace. + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 04:18:46 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id AF2B3475F38 + for ; + Mon, 27 Jan 2003 04:18:44 -0500 (EST) +Received: from lakemtao04.cox.net (lakemtao04.cox.net [68.1.17.241]) + by postgresql.org (Postfix) with ESMTP id E538E475E75 + for ; + Mon, 27 Jan 2003 04:18:43 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao04.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030127091845.UCKR22825.lakemtao04.cox.net@[192.168.1.1]> + for ; + Mon, 27 Jan 2003 04:18:45 -0500 +Subject: Re: bigserial vs serial - which one I'd have to use? +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <1043616281.829.38.camel@maci> +References: <1043616281.829.38.camel@maci> +Content-Type: text/plain +Organization: +Message-Id: <1043659121.815.407.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 27 Jan 2003 03:18:41 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/343 +X-Sequence-Number: 990 + +On Sun, 2003-01-26 at 15:24, Medve Gabor wrote: +> Hi all, +> +> Have you got any data (ie in percentage) of around how much more CPU +> work needed with the bigserial type in the queries? +> +> I have a log database with 100million records (the biggest table +> contains 65million records) and I use bigserial data type as primary key +> now. The primary key looks this way: YYYYMMDD1xxxxxxx where the first 8 +> numbers are the date, and the x's are the record sequence number on that +> day. This way the records are in ascendant order. Almost all of the +> queries contains date constraints (PK like 'YYYYMMDD%'). I'd like to +> know if I do it in a stupid way or not. I'm not a DBA expert so every +> idea are welcome. If you need more information about the +> hardware/software environment, the DB structure then I'll post them. + +I think you can only do LIKE queries on CHAR-type fields. + +BETWEEN ought to help you, though: +SELECT * +FROM foo +where prim_key BETWEEN YYYYMMDD00000000 and YYYYMMDD999999999; + +Alternatively, if you really want to do 'YYYYMMDD%', you could create +a functional index on to_char(prim_key). + +Lastly, you could create 2 fields and create a compound PK: +PK_DATE DATE, +PK_SERIAL BIGINT + +Then you could say: +SELECT * +FROM foo +where pk_date = 'YYYY-MM-DD' + +Of course, then you'd be adding an extra 8 bytes to each column... + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 04:44:49 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 39B96476142 + for ; + Mon, 27 Jan 2003 04:44:46 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id D8A28476135 + for ; + Mon, 27 Jan 2003 04:44:43 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id h0R9il417579 + for ; Mon, 27 Jan 2003 15:14:47 +0530 +Received: from daithan (daithan.intranet.pspl.co.in [192.168.7.161]) + by www.pspl.co.in (8.11.6/8.11.0) with ESMTP id h0R9il717574 + for ; Mon, 27 Jan 2003 15:14:47 +0530 +From: "Shridhar Daithankar" +To: PgSQL Performance ML +Date: Mon, 27 Jan 2003 15:15:07 +0530 +MIME-Version: 1.0 +Subject: Re: LOCK TABLE & speeding up mass data loads +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3E354CFB.32732.A38120C@localhost> +References: +In-reply-to: <1043658500.818.398.camel@haggis> +X-mailer: Pegasus Mail for Windows (v4.02) +Content-type: text/plain; charset=US-ASCII +Content-transfer-encoding: 7BIT +Content-description: Mail message body +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/344 +X-Sequence-Number: 991 + +On 27 Jan 2003 at 3:08, Ron Johnson wrote: + +> Here's what I'd like to see: +> COPY table [ ( column [, ...] ) ] +> FROM { 'filename' | stdin } +> [ [ WITH ] +> [ BINARY ] +> [ OIDS ] +> [ DELIMITER [ AS ] 'delimiter' ] +> [ NULL [ AS ] 'null string' ] ] +> [COMMIT EVERY ... ROWS WITH LOGGING] <<<<<<<<<<<<< +> [SKIP ... ROWS] <<<<<<<<<<<<< +> +> This way, if I'm loading 25M rows, I can have it commit every, say, +> 1000 rows, and if it pukes 1/2 way thru, then when I restart the +> COPY, it can SKIP past what's already been loaded, and proceed apace. + +IIRc, there is a hook to \copy, not the postgreSQL command copy for how many +transactions you would like to see. I remember to have benchmarked that and +concluded that doing copy in one transaction is the fastest way of doing it. + +DOn't have a postgresql installation handy, me being in linux, but this is +definitely possible.. + +Bye + Shridhar + +-- +I still maintain the point that designing a monolithic kernel in 1991 is +afundamental error. Be thankful you are not my student. You would not get +ahigh grade for such a design :-)(Andrew Tanenbaum to Linus Torvalds) + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 04:54:30 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 87E56476099 + for ; + Mon, 27 Jan 2003 04:54:28 -0500 (EST) +Received: from lakemtao01.cox.net (lakemtao01.cox.net [68.1.17.244]) + by postgresql.org (Postfix) with ESMTP id 64849475E3A + for ; + Mon, 27 Jan 2003 04:54:27 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao01.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030127095428.JDDD16369.lakemtao01.cox.net@[192.168.1.1]> + for ; + Mon, 27 Jan 2003 04:54:28 -0500 +Subject: Re: LOCK TABLE & speeding up mass data loads +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <3E354CFB.32732.A38120C@localhost> +References: + <3E354CFB.32732.A38120C@localhost> +Content-Type: text/plain +Organization: +Message-Id: <1043661264.9231.8.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 27 Jan 2003 03:54:25 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/345 +X-Sequence-Number: 992 + +On Mon, 2003-01-27 at 03:45, Shridhar Daithankar wrote: +> On 27 Jan 2003 at 3:08, Ron Johnson wrote: +> +> > Here's what I'd like to see: +> > COPY table [ ( column [, ...] ) ] +> > FROM { 'filename' | stdin } +> > [ [ WITH ] +> > [ BINARY ] +> > [ OIDS ] +> > [ DELIMITER [ AS ] 'delimiter' ] +> > [ NULL [ AS ] 'null string' ] ] +> > [COMMIT EVERY ... ROWS WITH LOGGING] <<<<<<<<<<<<< +> > [SKIP ... ROWS] <<<<<<<<<<<<< +> > +> > This way, if I'm loading 25M rows, I can have it commit every, say, +> > 1000 rows, and if it pukes 1/2 way thru, then when I restart the +> > COPY, it can SKIP past what's already been loaded, and proceed apace. +> +> IIRc, there is a hook to \copy, not the postgreSQL command copy for how many + +I'll have to look into that. + +> transactions you would like to see. I remember to have benchmarked that and +> concluded that doing copy in one transaction is the fastest way of doing it. + +Boy Scout motto: Be prepared!! (Serves me well as a DBA.) + +So it takes a little longer. In case of failure, the time would be +more than made up. Also, wouldn't the WAL grow hugely if many millions +of rows were inserted in one txn? + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 04:56:50 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 01E35475425 + for ; + Mon, 27 Jan 2003 04:56:48 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 05B14476099 + for ; + Mon, 27 Jan 2003 04:56:45 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id h0R9ujO18925 + for ; Mon, 27 Jan 2003 15:26:45 +0530 +Received: from daithan (daithan.intranet.pspl.co.in [192.168.7.161]) + by www.pspl.co.in (8.11.6/8.11.0) with ESMTP id h0R9uj718920 + for ; Mon, 27 Jan 2003 15:26:45 +0530 +From: "Shridhar Daithankar" +To: PgSQL Performance ML +Date: Mon, 27 Jan 2003 15:27:05 +0530 +MIME-Version: 1.0 +Subject: Re: LOCK TABLE & speeding up mass data loads +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3E354FC9.21573.A43098B@localhost> +In-reply-to: <3E354CFB.32732.A38120C@localhost> +References: <1043658500.818.398.camel@haggis> +X-mailer: Pegasus Mail for Windows (v4.02) +Content-type: text/plain; charset=US-ASCII +Content-transfer-encoding: 7BIT +Content-description: Mail message body +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/346 +X-Sequence-Number: 993 + +On 27 Jan 2003 at 15:15, Shridhar Daithankar wrote: +> IIRc, there is a hook to \copy, not the postgreSQL command copy for how many +> transactions you would like to see. I remember to have benchmarked that and +> concluded that doing copy in one transaction is the fastest way of doing it. +> +> DOn't have a postgresql installation handy, me being in linux, but this is +> definitely possible.. + +I am sleeping. That should have read XP rather than linux. + +Grrr.. + +Bye + Shridhar + +-- +Lowery's Law: If it jams -- force it. If it breaks, it needed replacing +anyway. + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 05:00:18 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7C3064762C6 + for ; + Mon, 27 Jan 2003 05:00:17 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id A23E54762BE + for ; + Mon, 27 Jan 2003 05:00:15 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id h0RA0J219361 + for ; Mon, 27 Jan 2003 15:30:19 +0530 +Received: from daithan (daithan.intranet.pspl.co.in [192.168.7.161]) + by www.pspl.co.in (8.11.6/8.11.0) with ESMTP id h0RA0J719356 + for ; Mon, 27 Jan 2003 15:30:19 +0530 +From: "Shridhar Daithankar" +To: PgSQL Performance ML +Date: Mon, 27 Jan 2003 15:30:39 +0530 +MIME-Version: 1.0 +Subject: Re: LOCK TABLE & speeding up mass data loads +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3E35509F.29103.A464C91@localhost> +References: <3E354CFB.32732.A38120C@localhost> +In-reply-to: <1043661264.9231.8.camel@haggis> +X-mailer: Pegasus Mail for Windows (v4.02) +Content-type: text/plain; charset=US-ASCII +Content-transfer-encoding: 7BIT +Content-description: Mail message body +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/347 +X-Sequence-Number: 994 + +On 27 Jan 2003 at 3:54, Ron Johnson wrote: + +> On Mon, 2003-01-27 at 03:45, Shridhar Daithankar wrote: +> > transactions you would like to see. I remember to have benchmarked that and +> > concluded that doing copy in one transaction is the fastest way of doing it. +> +> Boy Scout motto: Be prepared!! (Serves me well as a DBA.) + +Goes for everything else as well.. +> +> So it takes a little longer. In case of failure, the time would be +> more than made up. Also, wouldn't the WAL grow hugely if many millions +> of rows were inserted in one txn? + +Nops.. If WAL starts recycling, postgresql should start flishing data from WAL +to data files. + +At any given moment, WAL will not exceed of what you have configured. They are +just read ahead logs most of the times intended for crash recovery. +(Consequently it does not help setting WAL bigger than required.) + +Bye + Shridhar + +-- +nominal egg: New Yorkerese for expensive. + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 05:23:13 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 79DC2475E75 + for ; + Mon, 27 Jan 2003 05:23:12 -0500 (EST) +Received: from platonic.cynic.net (platonic.cynic.net [204.80.150.245]) + by postgresql.org (Postfix) with ESMTP id C3670475E3A + for ; + Mon, 27 Jan 2003 05:23:11 -0500 (EST) +Received: from angelic.cynic.net (angelic-platonic.cvpn.cynic.net + [198.73.220.226]) by platonic.cynic.net (Postfix) with ESMTP + id 2C838C003; Mon, 27 Jan 2003 10:23:12 +0000 (UTC) +Received: from localhost (localhost [127.0.0.1]) + by angelic.cynic.net (Postfix) with ESMTP + id AD1AD8736; Mon, 27 Jan 2003 19:23:10 +0900 (JST) +Date: Mon, 27 Jan 2003 19:23:10 +0900 (JST) +From: Curt Sampson +To: Ron Johnson +Cc: PgSQL Performance ML +Subject: Re: LOCK TABLE & speeding up mass data loads +In-Reply-To: <1043658500.818.398.camel@haggis> +Message-ID: +References: <1043521053.818.32.camel@haggis> + <1043521665.58142.135.camel@jester> + <1043522349.818.36.camel@haggis> + + <1043658500.818.398.camel@haggis> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/348 +X-Sequence-Number: 995 + +On Mon, 27 Jan 2003, Ron Johnson wrote: + +> > I don't see how the amount of data manipulation makes a difference. +> > Where you now issue a BEGIN, issue a COPY instead. Where you now INSERT, +> > just print the data for the columns, separated by tabs. Where you now +> > issue a COMMIT, end the copy. +> +> Yes, create an input file for COPY. Great idea. + +That's not quite what I was thinking of. Don't create an input file, +just send the commands directly to the server (if your API supports it). +If worst comes to worst, you could maybe open up a subprocess for a psql +and write to its standard input. + +> However, If I understand you correctly, then if I want to be able +> to not have to roll-back and re-run and complete COPY (which may +> entail millions of rows), then I'd have to have thousands of seperate +> input files (which would get processed sequentially). + +Right. + +But you can probably commit much less often than 1000 rows. 10,000 or +100,000 would probably be more practical. + +cjs +-- +Curt Sampson +81 90 7737 2974 http://www.netbsd.org + Don't you know, in this new Dark Age, we're all light. --XTC + +From pgsql-performance-owner@postgresql.org Mon Jan 27 05:34:56 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0414A475E75 + for ; + Mon, 27 Jan 2003 05:34:55 -0500 (EST) +Received: from platonic.cynic.net (platonic.cynic.net [204.80.150.245]) + by postgresql.org (Postfix) with ESMTP id 4BBF3475E3A + for ; + Mon, 27 Jan 2003 05:34:54 -0500 (EST) +Received: from angelic.cynic.net (angelic-platonic.cvpn.cynic.net + [198.73.220.226]) by platonic.cynic.net (Postfix) with ESMTP + id E6116C003; Mon, 27 Jan 2003 10:34:52 +0000 (UTC) +Received: from localhost (localhost [127.0.0.1]) + by angelic.cynic.net (Postfix) with ESMTP + id 0CFC58736; Mon, 27 Jan 2003 19:34:42 +0900 (JST) +Date: Mon, 27 Jan 2003 19:34:42 +0900 (JST) +From: Curt Sampson +To: Sean Chittenden +Cc: Tom Lane , Jeff , + Bruce Momjian , + Josh Berkus , Roman Fail , + "sszabo@megazone23.bigpanda.com" , + "pgsql-performance@postgresql.org" +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <20030127081745.GK15936@perrin.int.nxad.com> +Message-ID: +References: + <21623.1042865371@sss.pgh.pa.us> + <20030127081745.GK15936@perrin.int.nxad.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/349 +X-Sequence-Number: 996 + +On Mon, 27 Jan 2003, Sean Chittenden wrote: + +> The FreeBSD VM caching system does prevent one process from exhausting +> another process's cached data due to a sequential access, but the +> FreeBSD VM cache does not try to outsmart sequential data accesses to +> datasets which are larger then available cache space because it's an +> insanely difficult (impossible) problem to solve properly without +> foreknowledge of what data elements will be accessed when. + +This is not impossible; Solaris does just this. I'm a little short of +time right now, but I can probably dig up the paper on google if nobody +else finds it. + +Also, it is not hard to give the OS foreknowledge of your access +pattern, if you use mmap. Just call madvise and use the MADV_RANDOM, +MADV_SEQUENTIAL, MADV_WILLNEED and MADV_DONTNEED flags. (This is one +of the reasons I think we might see a performance improvement from +switching from regular I/O to mmap I/O.) + +You can go back through the archives and see a much fuller discussion of +all of this. + +cjs +-- +Curt Sampson +81 90 7737 2974 http://www.netbsd.org + Don't you know, in this new Dark Age, we're all light. --XTC + +From pgsql-performance-owner@postgresql.org Mon Jan 27 10:17:30 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 01FB6475EDC + for ; + Mon, 27 Jan 2003 10:17:30 -0500 (EST) +Received: from lakemtao02.cox.net (lakemtao02.cox.net [68.1.17.243]) + by postgresql.org (Postfix) with ESMTP id 6363A475CA9 + for ; + Mon, 27 Jan 2003 10:17:29 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao02.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030127151734.JYVJ6744.lakemtao02.cox.net@[192.168.1.1]> + for ; + Mon, 27 Jan 2003 10:17:34 -0500 +Subject: Re: 7.3.1 New install, large queries are slow +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: +References: + <21623.1042865371@sss.pgh.pa.us> + <20030127081745.GK15936@perrin.int.nxad.com> + +Content-Type: text/plain +Organization: +Message-Id: <1043680648.9896.24.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 27 Jan 2003 09:17:28 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/350 +X-Sequence-Number: 997 + +On Mon, 2003-01-27 at 04:34, Curt Sampson wrote: +> On Mon, 27 Jan 2003, Sean Chittenden wrote: +> +> > The FreeBSD VM caching system does prevent one process from exhausting +> > another process's cached data due to a sequential access, but the +> > FreeBSD VM cache does not try to outsmart sequential data accesses to +> > datasets which are larger then available cache space because it's an +> > insanely difficult (impossible) problem to solve properly without +> > foreknowledge of what data elements will be accessed when. +> +> This is not impossible; Solaris does just this. I'm a little short of + +Quite. One way to do it is: +- the OS notices that process X has been sequentially reading thru + file Y for, say, 3 seconds. +- the OS knows that X is currently at the mid-point of file Y +- OS says, "Hey, I think I'll be a bit more agressive about, when I + have a bit of time, trying to read Y faster than X is requesting + it + +It wouldn't work well, though, in a client-server DB like Postgres, +which, in a busy multi-user system, is constantly hitting different +parts of different files. + +The algorithm, though, is used in the RDBMS Rdb. It uses the algorithm +above, substituting "process X" for "client X", and passes the agressive +reads of Y on to the OS. It's a big win when processing a complete +table, like during a CREATE INDEX, or "SELECT foo, COUNT(*)" where +there's no index on foo. + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 14:23:21 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CBC2C475C22 + for ; + Mon, 27 Jan 2003 14:23:19 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 37D71475843 + for ; + Mon, 27 Jan 2003 14:23:19 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2327352; Mon, 27 Jan 2003 11:23:14 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Kevin Brown , + pgsql-performance@postgresql.org +Subject: Re: Mount options for Ext3? +Date: Mon, 27 Jan 2003 11:23:58 -0800 +X-Mailer: KMail [version 1.4] +References: <200301241120.14404.josh@agliodbs.com> + <200301241822.33731.josh@agliodbs.com> + <20030125025008.GD28252@filer> +In-Reply-To: <20030125025008.GD28252@filer> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301271123.58727.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/351 +X-Sequence-Number: 998 + + +Kevin, + +> BTW, why exactly are you running ext3? It has some nice journalling +> features but it sounds like you don't want to use them.=20=20 + +Because our RAID array controller, an Adaptec 2200S, is only compatible wit= +h=20 +RedHat 8.0, without some fancy device driver hacking. It certainly wasn't = +my=20 +first choice, I've been using Reiser for 4 years and am very happy with it. + +Warning to anyone following this thread: The web site info for the 2200S s= +ays=20 +"Redhat and SuSE", but drivers are only available for RedHat. Adaptec's= +=20 +Linux guru, Brian, has been unable to get the web site maintainers to corre= +ct=20 +the information on the site. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 14:32:49 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 73629475C22 + for ; + Mon, 27 Jan 2003 14:32:48 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id C8D07475843 + for ; + Mon, 27 Jan 2003 14:32:47 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2327378; Mon, 27 Jan 2003 11:32:53 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Medve Gabor , pgsql-performance@postgresql.org +Subject: Re: bigserial vs serial - which one I'd have to use? +Date: Mon, 27 Jan 2003 11:33:37 -0800 +X-Mailer: KMail [version 1.4] +References: <1043616281.829.38.camel@maci> +In-Reply-To: <1043616281.829.38.camel@maci> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301271133.37738.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/352 +X-Sequence-Number: 999 + + +Medve, + +> Have you got any data (ie in percentage) of around how much more CPU +> work needed with the bigserial type in the queries? +>=20 +> I have a log database with 100million records (the biggest table +> contains 65million records) and I use bigserial data type as primary key +> now. The primary key looks this way: YYYYMMDD1xxxxxxx where the first 8 +> numbers are the date, and the x's are the record sequence number on that +> day. This way the records are in ascendant order. Almost all of the +> queries contains date constraints (PK like 'YYYYMMDD%'). I'd like to +> know if I do it in a stupid way or not. I'm not a DBA expert so every +> idea are welcome. If you need more information about the +> hardware/software environment, the DB structure then I'll post them. + +Given that structure, I'd personally create a table with a 2-column primary= +=20 +key, one column of type DATE and one SERIAL column. Alternately, if you fi= +nd=20 +the conversion of DATE to char for output purposes really slows things down= +,=20 +one column of INT and one of SERIAL. Either way, the two columns togethe= +r=20 +make up the primary key. + +I would definitely suggest avoiting the temptation to do this as a single= +=20 +column of type CHAR(). That would be vastly more costly than either=20 +strategy mentioned above: + +DATE + SERIAL (INT) =3D 8 bytes +INT + SERIAL (INT) =3D 8 bytes +CHAR(16) =3D 18 bytes + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 14:43:51 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A93AD4767D1 + for ; + Mon, 27 Jan 2003 14:43:49 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 0D91A4767B8 + for ; + Mon, 27 Jan 2003 14:43:49 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030127194350.OTHN8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Mon, 27 Jan 2003 14:43:50 -0500 +Subject: Re: Mount options for Ext3? +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <200301271123.58727.josh@agliodbs.com> +References: <200301241120.14404.josh@agliodbs.com> + <200301241822.33731.josh@agliodbs.com> <20030125025008.GD28252@filer> + <200301271123.58727.josh@agliodbs.com> +Content-Type: text/plain +Organization: +Message-Id: <1043696628.9899.49.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 27 Jan 2003 13:43:48 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/353 +X-Sequence-Number: 1000 + +On Mon, 2003-01-27 at 13:23, Josh Berkus wrote: +> Kevin, +> +> > BTW, why exactly are you running ext3? It has some nice journalling +> > features but it sounds like you don't want to use them. +> +> Because our RAID array controller, an Adaptec 2200S, is only compatible with +> RedHat 8.0, without some fancy device driver hacking. It certainly wasn't my + +Binary-only, or OSS and just tuned to their kernels? + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 14:55:11 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 144FB475C22 + for ; + Mon, 27 Jan 2003 14:55:11 -0500 (EST) +Received: from lakemtao02.cox.net (lakemtao02.cox.net [68.1.17.243]) + by postgresql.org (Postfix) with ESMTP id 7E32A475843 + for ; + Mon, 27 Jan 2003 14:55:10 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao02.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030127195511.NBQX6744.lakemtao02.cox.net@[192.168.1.1]> + for ; + Mon, 27 Jan 2003 14:55:11 -0500 +Subject: Re: bigserial vs serial - which one I'd have to use? +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <200301271133.37738.josh@agliodbs.com> +References: <1043616281.829.38.camel@maci> + <200301271133.37738.josh@agliodbs.com> +Content-Type: text/plain +Organization: +Message-Id: <1043697304.9899.60.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 27 Jan 2003 13:55:04 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/354 +X-Sequence-Number: 1001 + +On Mon, 2003-01-27 at 13:33, Josh Berkus wrote: +> Medve, +> +> > Have you got any data (ie in percentage) of around how much more CPU +> > work needed with the bigserial type in the queries? +> > +> > I have a log database with 100million records (the biggest table +> > contains 65million records) and I use bigserial data type as primary key +> > now. The primary key looks this way: YYYYMMDD1xxxxxxx where the first 8 +> > numbers are the date, and the x's are the record sequence number on that +> > day. This way the records are in ascendant order. Almost all of the +> > queries contains date constraints (PK like 'YYYYMMDD%'). I'd like to +> > know if I do it in a stupid way or not. I'm not a DBA expert so every +> > idea are welcome. If you need more information about the +> > hardware/software environment, the DB structure then I'll post them. +> +> Given that structure, I'd personally create a table with a 2-column primary +> key, one column of type DATE and one SERIAL column. Alternately, if you find +> the conversion of DATE to char for output purposes really slows things down, +> one column of INT and one of SERIAL. Either way, the two columns together +> make up the primary key. +> +> I would definitely suggest avoiting the temptation to do this as a single +> column of type CHAR(). That would be vastly more costly than either +> strategy mentioned above: +> +> DATE + SERIAL (INT) = 8 bytes + +Ah, cool. I thought DATE was 8 bytes. Should have RTFM, of course. + +> INT + SERIAL (INT) = 8 bytes +> +> CHAR(16) = 18 bytes + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 15:11:39 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0BD35476B62 + for ; + Mon, 27 Jan 2003 15:11:39 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP id A935D476B1D + for ; + Mon, 27 Jan 2003 15:11:33 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id h0RKBI227504; + Mon, 27 Jan 2003 15:11:18 -0500 (EST) +From: Bruce Momjian +Message-Id: <200301272011.h0RKBI227504@candle.pha.pa.us> +Subject: Re: Mount options for Ext3? +In-Reply-To: <20030125025008.GD28252@filer> +To: Kevin Brown +Date: Mon, 27 Jan 2003 15:11:18 -0500 (EST) +Cc: pgsql-performance@postgresql.org +X-Mailer: ELM [version 2.4ME+ PL99 (25)] +MIME-Version: 1.0 +Content-Transfer-Encoding: 7bit +Content-Type: text/plain; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/355 +X-Sequence-Number: 1002 + + +Let me add that I have heard that on Linux XFS is better for PostgreSQL +than either ext3 or Reiser. + +--------------------------------------------------------------------------- + +Kevin Brown wrote: +> Josh Berkus wrote: +> > Well, the only reason I use Ext3 rather than Ext2 is to prevent fsck's on +> > restart after a crash. So I'm interested in the data option that gives the +> > minimum performance hit, even if it means that I sacrifice some reliability. +> > I'm running with fsynch on, and the DB is on a mirrored drive array, so I'm +> > not too worried about filesystem-level errors. +> > +> > So would that be "data=writeback"? +> +> Yes. That should give almost the same semantics as ext2 does by +> default, except that metadata is journalled, so no fsck needed. :-) +> +> In fact, I believe that's exactly how ReiserFS works, if I'm not +> mistaken (I saw someone claim that it does data journalling, but I've +> never seen any references to how to get ReiserFS to journal data). +> +> +> BTW, why exactly are you running ext3? It has some nice journalling +> features but it sounds like you don't want to use them. But at the +> same time, it uses pre-allocated inodes just like ext2 does, so it's +> possible to run out of inodes on ext2/3 while AFAIK that's not +> possible under ReiserFS. That's not likely to be a problem unless +> you're running a news server or something, though. :-) +> +> On the other hand, ext3 with data=writeback will probably be faster +> than ReiserFS for a number of things. +> +> No idea how stable ext3 is versus ReiserFS... +> +> +> +> -- +> Kevin Brown kevin@sysexperts.com +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 1: subscribe and unsubscribe commands go to majordomo@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-hackers-owner@postgresql.org Mon Jan 27 15:28:52 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 64B5A476B1E; Mon, 27 Jan 2003 15:28:51 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP + id 8B75F476B96; Mon, 27 Jan 2003 15:26:45 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id h0RKQS329900; + Mon, 27 Jan 2003 15:26:28 -0500 (EST) +From: Bruce Momjian +Message-Id: <200301272026.h0RKQS329900@candle.pha.pa.us> +Subject: Re: WAL replay logic (was Re: [PERFORM] Mount options for Ext3?) +In-Reply-To: <20030125101111.GB12957@filer> +To: Kevin Brown +Date: Mon, 27 Jan 2003 15:26:27 -0500 (EST) +Cc: pgsql-performance@postgresql.org, pgsql-hackers@postgresql.org +X-Mailer: ELM [version 2.4ME+ PL99 (25)] +MIME-Version: 1.0 +Content-Transfer-Encoding: 7bit +Content-Type: text/plain; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/1027 +X-Sequence-Number: 34637 + + +Is there a TODO here? I like the idea of not writing pg_controldata, or +at least allowing it not to be read, perhaps with a pg_resetxlog flag so +we can cleanly recover from a corrupt pg_controldata if the WAL files +are OK. + +We don't want to get rid of the WAL file rename optimization because +those are 16mb files and keeping them from checkpoint to checkpoint is +probably a win. I also like the idea of allowing something between our +"at the instant" recovery, and no recovery with fsync off. A "recover +from last checkpooint time" option would be really valuable for some. + +--------------------------------------------------------------------------- + +Kevin Brown wrote: +> Tom Lane wrote: +> > Kevin Brown writes: +> > > One question I have is: in the event of a crash, why not simply replay +> > > all the transactions found in the WAL? Is the startup time of the +> > > database that badly affected if pg_control is ignored? +> > +> > Interesting thought, indeed. Since we truncate the WAL after each +> > checkpoint, seems like this approach would no more than double the time +> > for restart. +> +> Hmm...truncating the WAL after each checkpoint minimizes the amount of +> disk space eaten by the WAL, but on the other hand keeping older +> segments around buys you some safety in the event that things get +> really hosed. But your later comments make it sound like the older +> WAL segments are kept around anyway, just rotated. +> +> > The win is it'd eliminate pg_control as a single point of +> > failure. It's always bothered me that we have to update pg_control on +> > every checkpoint --- it should be a write-pretty-darn-seldom file, +> > considering how critical it is. +> > +> > I think we'd have to make some changes in the code for deleting old +> > WAL segments --- right now it's not careful to delete them in order. +> > But surely that can be coped with. +> +> Even that might not be necessary. See below. +> +> > OTOH, this might just move the locus for fatal failures out of +> > pg_control and into the OS' algorithms for writing directory updates. +> > We would have no cross-check that the set of WAL file names visible in +> > pg_xlog is sensible or aligned with the true state of the datafile +> > area. +> +> Well, what we somehow need to guarantee is that there is always WAL +> data that is older than the newest consistent data in the datafile +> area, right? Meaning that if the datafile area gets scribbled on in +> an inconsistent manner, you always have WAL data to fill in the gaps. +> +> Right now we do that by using fsync() and sync(). But I think it +> would be highly desirable to be able to more or less guarantee +> database consistency even if fsync were turned off. The price for +> that might be too high, though. +> +> > We'd have to take it on faith that we should replay the visible files +> > in their name order. This might mean we'd have to abandon the current +> > hack of recycling xlog segments by renaming them --- which would be a +> > nontrivial performance hit. +> +> It's probably a bad idea for the replay to be based on the filenames. +> Instead, it should probably be based strictly on the contents of the +> xlog segment files. Seems to me the beginning of each segment file +> should have some kind of header information that makes it clear where +> in the scheme of things it belongs. Additionally, writing some sort +> of checksum, either at the beginning or the end, might not be a bad +> idea either (doesn't have to be a strict checksum, but it needs to be +> something that's reasonably likely to catch corruption within a +> segment). +> +> Do that, and you don't have to worry about renaming xlog segments at +> all: you simply move on to the next logical segment in the list (a +> replay just reads the header info for all the segments and orders the +> list as it sees fit, and discards all segments prior to any gap it +> finds. It may be that you simply have to bail out if you find a gap, +> though). As long as the xlog segment checksum information is +> consistent with the contents of the segment and as long as its +> transactions pick up where the previous segment's left off (assuming +> it's not the first segment, of course), you can safely replay the +> transactions it contains. +> +> I presume we're recycling xlog segments in order to avoid file +> creation and unlink overhead? Otherwise you can simply create new +> segments as needed and unlink old segments as policy dictates. +> +> > Comments anyone? +> > +> > > If there exists somewhere a reasonably succinct description of the +> > > reasoning behind the current transaction management scheme (including +> > > an analysis of the pros and cons), I'd love to read it and quit +> > > bugging you. :-) +> > +> > Not that I know of. Would you care to prepare such a writeup? There +> > is a lot of material in the source-code comments, but no coherent +> > presentation. +> +> Be happy to. Just point me to any non-obvious source files. +> +> Thus far on my plate: +> +> 1. PID file locking for postmaster startup (doesn't strictly need +> to be the PID file but it may as well be, since we're already +> messing with it anyway). I'm currently looking at how to do +> the autoconf tests, since I've never developed using autoconf +> before. +> +> 2. Documenting the transaction management scheme. +> +> I was initially interested in implementing the explicit JOIN +> reordering but based on your recent comments I think you have a much +> better handle on that than I. I'll be very interested to see what you +> do, to see if it's anything close to what I figure has to happen... +> +> +> -- +> Kevin Brown kevin@sysexperts.com +> +> ---------------------------(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 Mon Jan 27 15:40:24 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id F0CE2476997 + for ; + Mon, 27 Jan 2003 15:40:22 -0500 (EST) +Received: from txsmtp03.texas.rr.com (ms-smtp-03.texas.rr.com [24.93.36.231]) + by postgresql.org (Postfix) with ESMTP id B28F6476B7D + for ; + Mon, 27 Jan 2003 15:39:56 -0500 (EST) +Received: from spaceship.com (cs24243214-140.austin.rr.com [24.243.214.140]) + by txsmtp03.texas.rr.com (8.12.5/8.12.2) with ESMTP id h0RKZxEL003881 + for ; + Mon, 27 Jan 2003 15:35:59 -0500 (EST) +Message-ID: <3E35991D.5050704@spaceship.com> +Date: Mon, 27 Jan 2003 14:39:57 -0600 +From: Matt Mello +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: pgsql-performance@postgresql.org +Subject: Indexing foreign keys +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/357 +X-Sequence-Number: 1004 + +Due to reasons that everyone can probably intuit, we are porting a large +server application from IBM Informix to PG. However, things that take +milliseconds in IFX are taking HOURS (not joking) in PG. I *think* I +may have come across some reasons why, but I would like to see if anyone +else has an opinion. I could not find anything relevant in docs (but if +it is there, please point me to it). + +Let me give an example of one of the problems... + +I have a table that utilizes 2 foreign keys. It has 400000 records of +approximately 512 bytes each (mostly text, except for the keys). When I +run a specific query on it, it takes 8000ms to complete, and it always +does a full scan. + +I "assumed" that since I did not have to create an index on those +foreign key fields in IFX, that I did not have to in PG. However, just +for kicks, I created an index on those 2 fields, and my query time +(after the first, longer attempt, which I presume is from loading an +index) went from 8000ms to 100ms. + +So, do we ALWAYS have to create indexes for foreign key fields in PG? +Do the docs say this? (I couldn't find the info.) + +I will create other threads for my other issues. + +Thanks! + +-- +Matt Mello + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 15:56:40 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 23E4A47603B + for ; + Mon, 27 Jan 2003 15:56:40 -0500 (EST) +Received: from txsmtp02.texas.rr.com (ms-smtp-02.texas.rr.com [24.93.36.230]) + by postgresql.org (Postfix) with ESMTP id 8B5614759AF + for ; + Mon, 27 Jan 2003 15:56:39 -0500 (EST) +Received: from spaceship.com (cs24243214-140.austin.rr.com [24.243.214.140]) + by txsmtp02.texas.rr.com (8.12.5/8.12.2) with ESMTP id h0RKsN5D021623 + for ; + Mon, 27 Jan 2003 15:54:23 -0500 (EST) +Message-ID: <3E359D06.5020408@spaceship.com> +Date: Mon, 27 Jan 2003 14:56:38 -0600 +From: Matt Mello +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: pgsql-performance@postgresql.org +Subject: Re: Indexing foreign keys +References: <3E35991D.5050704@spaceship.com> + <030201c2c644$e14cfcb0$32021aac@chad> +In-Reply-To: <030201c2c644$e14cfcb0$32021aac@chad> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/358 +X-Sequence-Number: 1005 + +Yes, I had not only done a "vacuum full analyze" on the PG db once I +stuffed it, but I also compared that with an IFX db that I had run +"update statistics high" on. Things are much better with the FK indexes. + +Did the docs say to index those FK fields (is that standard in the DB +industry?), or was I just spoiled by IFX doing it for me? ;) + +Thanks! + + + +Chad Thompson wrote: +> Make sure that you've run a vacuum and an analyze. There is also a +> performance hit if the types of the fields or values are different. ie int +> to int8 + +-- +Matt Mello + + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 16:10:57 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D5E86476CC6 + for ; + Mon, 27 Jan 2003 16:10:56 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP id C8DA1476B62 + for ; + Mon, 27 Jan 2003 16:09:04 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id h0RL8xA05911; + Mon, 27 Jan 2003 16:08:59 -0500 (EST) +From: Bruce Momjian +Message-Id: <200301272108.h0RL8xA05911@candle.pha.pa.us> +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <1043680648.9896.24.camel@haggis> +To: Ron Johnson +Date: Mon, 27 Jan 2003 16:08:59 -0500 (EST) +Cc: PgSQL Performance ML +X-Mailer: ELM [version 2.4ME+ PL99 (25)] +MIME-Version: 1.0 +Content-Transfer-Encoding: 7bit +Content-Type: text/plain; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/359 +X-Sequence-Number: 1006 + + +Detecting sequential scan and increasing read-ahead is a standard OS +capability, and most/all do that already. Solaris has code to detect +when a sequential scan is wiping the cache and adjusting the buffer +frees, called "free-behind." + +--------------------------------------------------------------------------- + +Ron Johnson wrote: +> On Mon, 2003-01-27 at 04:34, Curt Sampson wrote: +> > On Mon, 27 Jan 2003, Sean Chittenden wrote: +> > +> > > The FreeBSD VM caching system does prevent one process from exhausting +> > > another process's cached data due to a sequential access, but the +> > > FreeBSD VM cache does not try to outsmart sequential data accesses to +> > > datasets which are larger then available cache space because it's an +> > > insanely difficult (impossible) problem to solve properly without +> > > foreknowledge of what data elements will be accessed when. +> > +> > This is not impossible; Solaris does just this. I'm a little short of +> +> Quite. One way to do it is: +> - the OS notices that process X has been sequentially reading thru +> file Y for, say, 3 seconds. +> - the OS knows that X is currently at the mid-point of file Y +> - OS says, "Hey, I think I'll be a bit more agressive about, when I +> have a bit of time, trying to read Y faster than X is requesting +> it +> +> It wouldn't work well, though, in a client-server DB like Postgres, +> which, in a busy multi-user system, is constantly hitting different +> parts of different files. +> +> The algorithm, though, is used in the RDBMS Rdb. It uses the algorithm +> above, substituting "process X" for "client X", and passes the agressive +> reads of Y on to the OS. It's a big win when processing a complete +> table, like during a CREATE INDEX, or "SELECT foo, COUNT(*)" where +> there's no index on foo. +> +> -- +> +---------------------------------------------------------------+ +> | Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +> | Jefferson, LA USA http://members.cox.net/ron.l.johnson | +> | | +> | "Fear the Penguin!!" | +> +---------------------------------------------------------------+ +> +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 5: Have you checked our extensive FAQ? +> +> http://www.postgresql.org/users-lounge/docs/faq.html +> + +-- + 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 Jan 27 16:13:04 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7E384476CC6 + for ; + Mon, 27 Jan 2003 16:13:03 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id E98B1476C9D + for ; + Mon, 27 Jan 2003 16:11:18 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2334697; Mon, 27 Jan 2003 13:11:23 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Matt Mello , + pgsql-performance@postgresql.org +Subject: Re: Indexing foreign keys +Date: Mon, 27 Jan 2003 13:12:09 -0800 +X-Mailer: KMail [version 1.4] +References: <3E35991D.5050704@spaceship.com> + <030201c2c644$e14cfcb0$32021aac@chad> + <3E359D06.5020408@spaceship.com> +In-Reply-To: <3E359D06.5020408@spaceship.com> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301271312.09105.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/360 +X-Sequence-Number: 1007 + + +Matt, + +> Did the docs say to index those FK fields (is that standard in the DB=20 +> industry?), or was I just spoiled by IFX doing it for me? ;) + +It's pretty standard in the DB industry. + + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 16:15:37 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EC75A476BF8 + for ; + Mon, 27 Jan 2003 16:15:35 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 4129A476CED + for ; + Mon, 27 Jan 2003 16:13:33 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao03.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030127211335.PTRE8666.lakemtao03.cox.net@[192.168.1.1]> + for ; + Mon, 27 Jan 2003 16:13:35 -0500 +Subject: Re: Indexing foreign keys +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <3E35991D.5050704@spaceship.com> +References: <3E35991D.5050704@spaceship.com> +Content-Type: text/plain +Organization: +Message-Id: <1043702012.9896.72.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 27 Jan 2003 15:13:32 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/361 +X-Sequence-Number: 1008 + +On Mon, 2003-01-27 at 14:39, Matt Mello wrote: +> Due to reasons that everyone can probably intuit, we are porting a large +> server application from IBM Informix to PG. However, things that take +> milliseconds in IFX are taking HOURS (not joking) in PG. I *think* I +> may have come across some reasons why, but I would like to see if anyone +> else has an opinion. I could not find anything relevant in docs (but if +> it is there, please point me to it). +> +> Let me give an example of one of the problems... +> +> I have a table that utilizes 2 foreign keys. It has 400000 records of +> approximately 512 bytes each (mostly text, except for the keys). When I +> run a specific query on it, it takes 8000ms to complete, and it always +> does a full scan. +> +> I "assumed" that since I did not have to create an index on those +> foreign key fields in IFX, that I did not have to in PG. However, just +> for kicks, I created an index on those 2 fields, and my query time +> (after the first, longer attempt, which I presume is from loading an +> index) went from 8000ms to 100ms. +> +> So, do we ALWAYS have to create indexes for foreign key fields in PG? +> Do the docs say this? (I couldn't find the info.) + +When you say "I created an index on those 2 fields", so you mean on +the fields in the 400K row table, or on the keys in the "fact tables" +that the 400K row table? + +Also, in IFX, could the creation of the foreign indexes have implicitly +created indexes? +The reason I ask is that this is what happens in Pg when you create a +PK. + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 16:19:23 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A7C1D476C0D + for ; + Mon, 27 Jan 2003 16:19:22 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id D29DD476A75 + for ; + Mon, 27 Jan 2003 16:16:48 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 130F5D606; Mon, 27 Jan 2003 13:16:50 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 08CB35C03; Mon, 27 Jan 2003 13:16:50 -0800 (PST) +Date: Mon, 27 Jan 2003 13:16:49 -0800 (PST) +From: Stephan Szabo +To: Matt Mello +Cc: +Subject: Re: Indexing foreign keys +In-Reply-To: <3E35991D.5050704@spaceship.com> +Message-ID: <20030127131057.F81562-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/362 +X-Sequence-Number: 1009 + +On Mon, 27 Jan 2003, Matt Mello wrote: + +> Due to reasons that everyone can probably intuit, we are porting a large +> server application from IBM Informix to PG. However, things that take +> milliseconds in IFX are taking HOURS (not joking) in PG. I *think* I +> may have come across some reasons why, but I would like to see if anyone +> else has an opinion. I could not find anything relevant in docs (but if +> it is there, please point me to it). +> +> Let me give an example of one of the problems... +> +> I have a table that utilizes 2 foreign keys. It has 400000 records of +> approximately 512 bytes each (mostly text, except for the keys). When I +> run a specific query on it, it takes 8000ms to complete, and it always +> does a full scan. +> +> I "assumed" that since I did not have to create an index on those +> foreign key fields in IFX, that I did not have to in PG. However, just +> for kicks, I created an index on those 2 fields, and my query time +> (after the first, longer attempt, which I presume is from loading an +> index) went from 8000ms to 100ms. +> +> So, do we ALWAYS have to create indexes for foreign key fields in PG? +> Do the docs say this? (I couldn't find the info.) + +You don't always need to create them, because there are fk patterns where +an index is counterproductive, but if you're not in one of those cases you +should create them. I'm not sure the docs actually say anything about +this however. + + + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 16:25:06 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 39A15476B91 + for ; + Mon, 27 Jan 2003 16:25:05 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 86D78476CF4 + for ; + Mon, 27 Jan 2003 16:22:29 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2335945; Mon, 27 Jan 2003 13:22:34 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Stephan Szabo , + Matt Mello +Subject: Re: Indexing foreign keys +Date: Mon, 27 Jan 2003 13:23:19 -0800 +X-Mailer: KMail [version 1.4] +Cc: +References: <20030127131057.F81562-100000@megazone23.bigpanda.com> +In-Reply-To: <20030127131057.F81562-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301271323.19644.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/363 +X-Sequence-Number: 1010 + +Guys, + +> You don't always need to create them, because there are fk patterns where +> an index is counterproductive, but if you're not in one of those cases you +> should create them. I'm not sure the docs actually say anything about +> this however. + +See: +http://techdocs.postgresql.org/techdocs/pgsqladventuresep2.php +http://techdocs.postgresql.org/techdocs/pgsqladventuresep3.php + +(and yes, I know I need to finish this series ...) + + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 19:05:42 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5254747627E + for ; + Mon, 27 Jan 2003 19:05:41 -0500 (EST) +Received: from silmaril.syscor.priv (h24-77-52-251.sbm.shawcable.net + [24.77.52.251]) by postgresql.org (Postfix) with ESMTP id 3B39E475D64 + for ; + Mon, 27 Jan 2003 19:05:40 -0500 (EST) +Received: from syscor.com (strider.syscor.priv [192.168.1.3]) + by silmaril.syscor.priv (8.11.1/8.11.1) with ESMTP id h0S05l120238 + for ; Mon, 27 Jan 2003 16:05:47 -0800 +Message-ID: <3E35C99B.5020105@syscor.com> +Date: Mon, 27 Jan 2003 16:06:51 -0800 +From: "Ron St.Pierre" +User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.2) Gecko/20021126 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: pgsql-performance@postgresql.org +Subject: Re: Indexing foreign keys +References: <3E35991D.5050704@spaceship.com> + <030201c2c644$e14cfcb0$32021aac@chad> + <3E359D06.5020408@spaceship.com> + <200301271312.09105.josh@agliodbs.com> +In-Reply-To: <200301271312.09105.josh@agliodbs.com> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/364 +X-Sequence-Number: 1011 + +Josh Berkus wrote: +> Matt, +>>Did the docs say to index those FK fields (is that standard in the DB +>>industry?), or was I just spoiled by IFX doing it for me? ;) +> It's pretty standard in the DB industry. + +I didn't know that, but I'm new to the DB field. I've gleaned quite a +few tips from this group, especially from responses to people with slow +queries/databases, but this is the first I've noticed it this tip. I'll +try it on my db too. + + +-- +Ron St.Pierre +Syscor R&D +tel: 250-361-1681 +email: rstpierre@syscor.com + + +From pgsql-performance-owner@postgresql.org Mon Jan 27 20:42:43 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 88650475E1E + for ; + Mon, 27 Jan 2003 20:42:41 -0500 (EST) +Received: from lakemtao02.cox.net (lakemtao02.cox.net [68.1.17.243]) + by postgresql.org (Postfix) with ESMTP id 7BFBD475D64 + for ; + Mon, 27 Jan 2003 20:42:40 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao02.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030128014242.RREX6744.lakemtao02.cox.net@[192.168.1.1]> + for ; + Mon, 27 Jan 2003 20:42:42 -0500 +Subject: Re: 7.3.1 New install, large queries are slow +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <200301272108.h0RL8xA05911@candle.pha.pa.us> +References: <200301272108.h0RL8xA05911@candle.pha.pa.us> +Content-Type: text/plain +Organization: +Message-Id: <1043718161.9896.120.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 27 Jan 2003 19:42:41 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/365 +X-Sequence-Number: 1012 + +On Mon, 2003-01-27 at 15:08, Bruce Momjian wrote: +> Detecting sequential scan and increasing read-ahead is a standard OS +> capability, and most/all do that already. Solaris has code to detect +> when a sequential scan is wiping the cache and adjusting the buffer +> frees, called "free-behind." + +Ah, didn't know that. + +> --------------------------------------------------------------------------- +> +> Ron Johnson wrote: +> > On Mon, 2003-01-27 at 04:34, Curt Sampson wrote: +> > > On Mon, 27 Jan 2003, Sean Chittenden wrote: +> > > +> > > > The FreeBSD VM caching system does prevent one process from exhausting +> > > > another process's cached data due to a sequential access, but the +> > > > FreeBSD VM cache does not try to outsmart sequential data accesses to +> > > > datasets which are larger then available cache space because it's an +> > > > insanely difficult (impossible) problem to solve properly without +> > > > foreknowledge of what data elements will be accessed when. +> > > +> > > This is not impossible; Solaris does just this. I'm a little short of +> > +> > Quite. One way to do it is: +> > - the OS notices that process X has been sequentially reading thru +> > file Y for, say, 3 seconds. +> > - the OS knows that X is currently at the mid-point of file Y +> > - OS says, "Hey, I think I'll be a bit more agressive about, when I +> > have a bit of time, trying to read Y faster than X is requesting +> > it +> > +> > It wouldn't work well, though, in a client-server DB like Postgres, +> > which, in a busy multi-user system, is constantly hitting different +> > parts of different files. +> > +> > The algorithm, though, is used in the RDBMS Rdb. It uses the algorithm +> > above, substituting "process X" for "client X", and passes the agressive +> > reads of Y on to the OS. It's a big win when processing a complete +> > table, like during a CREATE INDEX, or "SELECT foo, COUNT(*)" where +> > there's no index on foo. + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Tue Jan 28 00:46:46 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D427C475FED + for ; + Tue, 28 Jan 2003 00:46:44 -0500 (EST) +Received: from txsmtp01.texas.rr.com (ms-smtp-01.texas.rr.com [24.93.36.229]) + by postgresql.org (Postfix) with ESMTP id 52179475FEC + for ; + Tue, 28 Jan 2003 00:46:44 -0500 (EST) +Received: from spaceship.com (cs24243214-140.austin.rr.com [24.243.214.140]) + by txsmtp01.texas.rr.com (8.12.5/8.12.2) with ESMTP id h0S5fxua013648 + for ; + Tue, 28 Jan 2003 00:41:59 -0500 (EST) +Message-ID: <3E361946.4060000@spaceship.com> +Date: Mon, 27 Jan 2003 23:46:46 -0600 +From: Matt Mello +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: PgSQL Performance ML +Subject: Re: Indexing foreign keys +References: <3E35991D.5050704@spaceship.com> <1043702012.9896.72.camel@haggis> +In-Reply-To: <1043702012.9896.72.camel@haggis> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/366 +X-Sequence-Number: 1013 + +Ron Johnson wrote: +> When you say "I created an index on those 2 fields", so you mean on +> the fields in the 400K row table, or on the keys in the "fact tables" +> that the 400K row table? +> +> Also, in IFX, could the creation of the foreign indexes have implicitly +> created indexes? +> The reason I ask is that this is what happens in Pg when you create a +> PK. +> + +The 400K row table has 2 fields that are FK fields. The already-indexed +PK fields that they reference are in another table. I just recently +added indexes to the 2 FK fields in the 400K row table to get the speed +boost. + +Yes. In IFX, when you create a FK, it seems to create indexes +automatically for you, just like PG does with PK's. + +In fact, I can't imagine a situation where you would NOT want a FK +indexed. I guess there must be one, or else I'm sure the developers +would have already added auto-creation of indexes to the FK creation, as +well. + +-- +Matt Mello + + +From pgsql-performance-owner@postgresql.org Tue Jan 28 00:51:27 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0F292475D99 + for ; + Tue, 28 Jan 2003 00:51:27 -0500 (EST) +Received: from txsmtp02.texas.rr.com (ms-smtp-02.texas.rr.com [24.93.36.230]) + by postgresql.org (Postfix) with ESMTP id 57F31475A71 + for ; + Tue, 28 Jan 2003 00:51:26 -0500 (EST) +Received: from spaceship.com (cs24243214-140.austin.rr.com [24.243.214.140]) + by txsmtp02.texas.rr.com (8.12.5/8.12.2) with ESMTP id h0S5nE5D023572 + for ; + Tue, 28 Jan 2003 00:49:15 -0500 (EST) +Message-ID: <3E361A63.6010409@spaceship.com> +Date: Mon, 27 Jan 2003 23:51:31 -0600 +From: Matt Mello +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: pgsql-performance@postgresql.org +Subject: Re: Indexing foreign keys +References: <20030127131057.F81562-100000@megazone23.bigpanda.com> +In-Reply-To: <20030127131057.F81562-100000@megazone23.bigpanda.com> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/367 +X-Sequence-Number: 1014 + +> You don't always need to create them, because there are fk patterns where +> an index is counterproductive, but if you're not in one of those cases you +> should create them. I'm not sure the docs actually say anything about +> this however. + +I would try to add a comment about this to the interactive docs if they +weren't so far behind already (7.2.1). :\ + +-- +Matt Mello + + +From pgsql-performance-owner@postgresql.org Tue Jan 28 02:49:54 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BB407475F13 + for ; + Tue, 28 Jan 2003 02:49:52 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 45D87475DD0 + for ; + Tue, 28 Jan 2003 02:49:52 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 9FF89D610; Mon, 27 Jan 2003 23:49:52 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 95B215C03; Mon, 27 Jan 2003 23:49:52 -0800 (PST) +Date: Mon, 27 Jan 2003 23:49:52 -0800 (PST) +From: Stephan Szabo +To: Matt Mello +Cc: PgSQL Performance ML +Subject: Re: Indexing foreign keys +In-Reply-To: <3E361946.4060000@spaceship.com> +Message-ID: <20030127234454.N88775-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/368 +X-Sequence-Number: 1015 + +On Mon, 27 Jan 2003, Matt Mello wrote: + +> Yes. In IFX, when you create a FK, it seems to create indexes +> automatically for you, just like PG does with PK's. +> +> In fact, I can't imagine a situation where you would NOT want a FK +> indexed. I guess there must be one, or else I'm sure the developers +> would have already added auto-creation of indexes to the FK creation, as +> well. + +Any case where the pk table is small enough and the values are fairly +evenly distributed so that the index isn't very selective. You end up not +using the index anyway because it's not selective and you pay the costs +involved in keeping it up to date. + + +From pgsql-performance-owner@postgresql.org Tue Jan 28 05:54:53 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7C7A8475D00 + for ; + Tue, 28 Jan 2003 05:54:52 -0500 (EST) +Received: from platonic.cynic.net (platonic.cynic.net [204.80.150.245]) + by postgresql.org (Postfix) with ESMTP id BCACD475CEE + for ; + Tue, 28 Jan 2003 05:54:51 -0500 (EST) +Received: from angelic.cynic.net (angelic-platonic.cvpn.cynic.net + [198.73.220.226]) by platonic.cynic.net (Postfix) with ESMTP + id C38ADBFFB; Tue, 28 Jan 2003 10:54:52 +0000 (UTC) +Received: from localhost (localhost [127.0.0.1]) + by angelic.cynic.net (Postfix) with ESMTP + id D07A58736; Tue, 28 Jan 2003 19:54:50 +0900 (JST) +Date: Tue, 28 Jan 2003 19:54:50 +0900 (JST) +From: Curt Sampson +To: Ron Johnson +Cc: PgSQL Performance ML +Subject: Re: 7.3.1 New install, large queries are slow +In-Reply-To: <1043680648.9896.24.camel@haggis> +Message-ID: +References: + <21623.1042865371@sss.pgh.pa.us> + <20030127081745.GK15936@perrin.int.nxad.com> + + <1043680648.9896.24.camel@haggis> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/369 +X-Sequence-Number: 1016 + +On Tue, 27 Jan 2003, Ron Johnson wrote: + +> [read-ahead detection stuff deleted] +> +> It wouldn't work well, though, in a client-server DB like Postgres, +> which, in a busy multi-user system, is constantly hitting different +> parts of different files. + +It works great. You just do it on a file-descriptor by file-descriptor +basis. + +Unfortunately, I don't know of any OSes that detect backwards scans. + +cjs +-- +Curt Sampson +81 90 7737 2974 http://www.netbsd.org + Don't you know, in this new Dark Age, we're all light. --XTC + +From pgsql-performance-owner@postgresql.org Tue Jan 28 10:15:10 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3E4CB475F39 + for ; + Tue, 28 Jan 2003 10:15:09 -0500 (EST) +Received: from lakemtao01.cox.net (lakemtao01.cox.net [68.1.17.244]) + by postgresql.org (Postfix) with ESMTP id C0BBB475D00 + for ; + Tue, 28 Jan 2003 10:15:05 -0500 (EST) +Received: from [192.168.1.1] ([68.11.66.83]) by lakemtao01.cox.net + (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP + id <20030128151508.ZUTQ16369.lakemtao01.cox.net@[192.168.1.1]> + for ; + Tue, 28 Jan 2003 10:15:08 -0500 +Subject: Re: Indexing foreign keys +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <3E361946.4060000@spaceship.com> +References: <3E35991D.5050704@spaceship.com> + <1043702012.9896.72.camel@haggis> <3E361946.4060000@spaceship.com> +Content-Type: text/plain +Organization: +Message-Id: <1043766909.9899.132.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 28 Jan 2003 09:15:09 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/370 +X-Sequence-Number: 1017 + +On Mon, 2003-01-27 at 23:46, Matt Mello wrote: +> Ron Johnson wrote: +> > When you say "I created an index on those 2 fields", so you mean on +> > the fields in the 400K row table, or on the keys in the "fact tables" +> > that the 400K row table? +> > +> > Also, in IFX, could the creation of the foreign indexes have implicitly +> > created indexes? +> > The reason I ask is that this is what happens in Pg when you create a +> > PK. +> > +> +> The 400K row table has 2 fields that are FK fields. The already-indexed +> PK fields that they reference are in another table. I just recently +> added indexes to the 2 FK fields in the 400K row table to get the speed +> boost. +> +> Yes. In IFX, when you create a FK, it seems to create indexes +> automatically for you, just like PG does with PK's. +> +> In fact, I can't imagine a situation where you would NOT want a FK +> indexed. I guess there must be one, or else I'm sure the developers +> would have already added auto-creation of indexes to the FK creation, as +> well. + +When I took my brain out of 1st gear, it was "Doh!": I realized that +I was thinking backwards... + +-- ++---------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "Fear the Penguin!!" | ++---------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Tue Jan 28 12:29:50 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 11DF24770C0 + for ; + Tue, 28 Jan 2003 12:29:49 -0500 (EST) +Received: from smtp.web.de (smtp03.web.de [217.72.192.158]) + by postgresql.org (Postfix) with ESMTP id DD21347713C + for ; + Tue, 28 Jan 2003 11:50:52 -0500 (EST) +Received: from p50818051.dip0.t-ipconnect.de ([80.129.128.81] helo=web.de) + by smtp.web.de with asmtp (WEB.DE(Exim) 4.93 #1) id 18dYwo-00075t-00 + for pgsql-performance@postgresql.org; Tue, 28 Jan 2003 17:50:55 +0100 +Message-ID: <3E36B4F2.1020506@web.de> +Date: Tue, 28 Jan 2003 17:50:58 +0100 +From: Andreas Pflug +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3a) Gecko/20021212 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: pgsql-performance@postgresql.org +Subject: inefficient query plan with left joined view +Content-Type: text/plain; charset=ISO-8859-1; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/371 +X-Sequence-Number: 1018 + +What I'm doing on V7.3.1: + +select t1.keycol, t2.keycol + from tab1 t1 + LEFT join myview t2 on t1.keycol=t2.keycol +where t1.keycol=1000001 + +t1 has 100 rows, t2 has 4000, both with keycol as PK. + +the view is created as +CREATE myview AS SELECT keycol, 22::integer as calc_col FROM tab2 + +The query plan will show an ugly subquery scan on all tab2 rows. If the +view is created without calculated columns, the query plan looks as +expected showing and index scan on tab2 with the correct condition, +inner join will always be ok. + +In real life, the view consists of a lot more tables, and the tables may +contain >1,000,000 rows so you may imagine the performance... + + + +From pgsql-performance-owner@postgresql.org Tue Jan 28 15:05:09 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 37E2F47728F + for ; + Tue, 28 Jan 2003 14:41:54 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 5054D4775DC + for ; + Tue, 28 Jan 2003 13:30:09 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0SIU85u022634; + Tue, 28 Jan 2003 13:30:08 -0500 (EST) +To: Andreas Pflug +Cc: pgsql-performance@postgresql.org +Subject: Re: inefficient query plan with left joined view +In-reply-to: <3E36B4F2.1020506@web.de> +References: <3E36B4F2.1020506@web.de> +Comments: In-reply-to Andreas Pflug + message dated "Tue, 28 Jan 2003 17:50:58 +0100" +Date: Tue, 28 Jan 2003 13:30:07 -0500 +Message-ID: <22633.1043778607@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/372 +X-Sequence-Number: 1019 + +Andreas Pflug writes: +> What I'm doing on V7.3.1: +> select t1.keycol, t2.keycol +> from tab1 t1 +> LEFT join myview t2 on t1.keycol=t2.keycol +> where t1.keycol=1000001 + +> the view is created as +> CREATE myview AS SELECT keycol, 22::integer as calc_col FROM tab2 + +The subquery isn't pulled up because it doesn't pass the +has_nullable_targetlist test in src/backend/optimizer/plan/planner.c. +If we did flatten it, then references to calc_col wouldn't correctly +go to NULL when the LEFT JOIN should make them do so --- they'd be +22 all the time. + +As the notes in that routine say, it could be made smarter: strict +functions of nullable variables could be allowed. So if your real +concern is not '22' but something like 'othercol + 22' then this is +fixable. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Jan 28 15:38:06 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A27A647933F + for ; + Tue, 28 Jan 2003 15:29:45 -0500 (EST) +Received: from smtp.web.de (smtp02.web.de [217.72.192.151]) + by postgresql.org (Postfix) with ESMTP id 8D35F476AD8 + for ; + Tue, 28 Jan 2003 14:31:48 -0500 (EST) +Received: from p50818051.dip0.t-ipconnect.de ([80.129.128.81] helo=web.de) + by smtp.web.de with asmtp (WEB.DE(Exim) 4.93 #1) id 18dbSV-0002QB-00 + for pgsql-performance@postgresql.org; Tue, 28 Jan 2003 20:31:47 +0100 +Message-ID: <3E36DAA2.4010003@web.de> +Date: Tue, 28 Jan 2003 20:31:46 +0100 +From: Andreas Pflug +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3a) Gecko/20021212 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: pgsql-performance@postgresql.org +Subject: Re: inefficient query plan with left joined view +References: <3E36B4F2.1020506@web.de> <22633.1043778607@sss.pgh.pa.us> +In-Reply-To: <22633.1043778607@sss.pgh.pa.us> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/373 +X-Sequence-Number: 1020 + +Tom Lane wrote: + +>The subquery isn't pulled up because it doesn't pass the +>has_nullable_targetlist test in src/backend/optimizer/plan/planner.c. +>If we did flatten it, then references to calc_col wouldn't correctly +>go to NULL when the LEFT JOIN should make them do so --- they'd be +>22 all the time. +> +>As the notes in that routine say, it could be made smarter: strict +>functions of nullable variables could be allowed. So if your real +>concern is not '22' but something like 'othercol + 22' then this is +>fixable. +> +> regards, tom lane +> +> +> +Tom, + +actually my views do use calculated columns (mostly concated strings, +e.g. full name from title/1st/last name). As the example shows even +columns that are never used will be taken into account when checking +has_nullable_targetlist. Unfortunately I have a lot of views containing +views which containing.... delivering a lot more columns than needed. +But they are checked anyway... + +I'd expect the parser to look at the join construction only to find out +about available data. Why should the selected (and even unselected) +columns be evaluated if the join delivers no result? Maybe this can be +achieved by checking only JOIN ON/WHERE columns with +has_nullable_targetlist? + + + +Regards, +Andreas + + +From pgsql-general-owner@postgresql.org Tue Jan 28 17:56:49 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 884F8479285 + for ; + Tue, 28 Jan 2003 17:56:47 -0500 (EST) +Received: from mail.com-stock.com (mail.com-stock.com [204.255.137.254]) + by postgresql.org (Postfix) with ESMTP id D283A4771CD + for ; + Tue, 28 Jan 2003 16:27:20 -0500 (EST) +Received: by mail.com-stock.com (Postfix, from userid 1000) + id 00D8713E; Tue, 28 Jan 2003 16:27:14 -0500 (EST) +Received: from deimos (deimos.com-stock.com [204.255.137.120]) + by mail.com-stock.com (Postfix) with SMTP id B2524DA36 + for ; + Tue, 28 Jan 2003 16:27:13 -0500 (EST) +Message-ID: <020301c2c715$03cef290$7889ffcc@comstock.com> +From: "Gregory Wood" +To: "PostgreSQL-General" +References: <20030127234454.N88775-100000@megazone23.bigpanda.com> +Subject: Re: [PERFORM] Indexing foreign keys +Date: Tue, 28 Jan 2003 16:23:08 -0500 +Organization: Comstock Net Services +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 6.00.2800.1106 +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/1274 +X-Sequence-Number: 36395 + +> > In fact, I can't imagine a situation where you would NOT want a FK +> > indexed. I guess there must be one, or else I'm sure the developers +> > would have already added auto-creation of indexes to the FK creation, as +> > well. +> +> Any case where the pk table is small enough and the values are fairly +> evenly distributed so that the index isn't very selective. You end up not +> using the index anyway because it's not selective and you pay the costs +> involved in keeping it up to date. + +Or you want an index on two or more fields that includes the FK as the +primary field. No sense in making two indexes. + +Greg + + +From pgsql-performance-owner@postgresql.org Tue Jan 28 19:12:19 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9574F477645 + for ; + Tue, 28 Jan 2003 18:47:01 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 68B054775C5 + for ; + Tue, 28 Jan 2003 17:40:58 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0SMf05u004510; + Tue, 28 Jan 2003 17:41:00 -0500 (EST) +To: Andreas Pflug +Cc: pgsql-performance@postgresql.org +Subject: Re: inefficient query plan with left joined view +In-reply-to: <3E36DAA2.4010003@web.de> +References: <3E36B4F2.1020506@web.de> <22633.1043778607@sss.pgh.pa.us> + <3E36DAA2.4010003@web.de> +Comments: In-reply-to Andreas Pflug + message dated "Tue, 28 Jan 2003 20:31:46 +0100" +Date: Tue, 28 Jan 2003 17:41:00 -0500 +Message-ID: <4509.1043793660@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/374 +X-Sequence-Number: 1021 + +Andreas Pflug writes: +> As the example shows even +> columns that are never used will be taken into account when checking +> has_nullable_targetlist. + +It's not really practical to do otherwise, as the code that needs to +check this doesn't have access to a list of the columns actually used. +Even if we kluged things up enough to make it possible to find that out, +that would merely mean that *some* of your queries wouldn't have a +problem. + +What about improving the intelligence of the nullability check --- or do +you have non-strict expressions in there? + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Jan 28 23:19:21 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A4E0E477389 + for ; + Tue, 28 Jan 2003 23:18:35 -0500 (EST) +Received: from johnlaptop.darkcore.net (h24-82-231-93.wp.shawcable.net + [24.82.231.93]) by postgresql.org (Postfix) with ESMTP id 9873B476F96 + for ; + Tue, 28 Jan 2003 22:21:40 -0500 (EST) +Received: by johnlaptop.darkcore.net (Postfix, from userid 501) + id 17751F2497; Tue, 28 Jan 2003 22:21:41 -0500 (EST) +Subject: Re: Query plan and Inheritance. Weird behavior +From: John Lange +To: Andras Kadinger +Cc: PostgreSQL +In-Reply-To: <3E3717A4.CAD034EC@surfnonstop.com> +References: <3E31A255.5250DCF1@surfnonstop.com> + <1043770598.2045.23.camel@johnlaptop.darkcore.net> + <3E3717A4.CAD034EC@surfnonstop.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +X-Mailer: Ximian Evolution 1.0.8-3mdk +Date: 28 Jan 2003 21:21:41 -0600 +Message-Id: <1043810501.3719.28.camel@johnlaptop.darkcore.net> +Mime-Version: 1.0 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/375 +X-Sequence-Number: 1022 + +> I don't see how performance would be significantly better if you stored +> the common columns of all rows (parent and children) in the parent +> table, in contrast with how it is done now, storing entire rows of child +> tables in the child table and omitting them from the parent table. + +Well there are a couple of points. + +Firstly, from the simple standpoint of database normalization you +shouldn't have tables that have the same columns. The way it is +implemented, child tables are copies of parent tables. + +But more importantly it is bad for performance because selecting from a +parent table causes the same select to be done on all the child tables. +In my case selecting from the parent causes six selects to be done (one +for every child table). + +I would have assumed that child tables only contained the new columns +unique to it, not duplicates of the columns already in the parent table. + +An insert to a child table would actually cause two inserts to be done +(assuming only one level of inheritance), one to the parent, and then +one to the child. + +Therefore, selects from the parent table would only require a single +select (because the common data is all stored in the parent table). + +Selects to a child would require two selects to get the entire row (one +to the parent, one to the child). Similar to a view. + +As I said previously, performance would depend on what operation you +were mostly doing. + +I think I have more or less covered this in my previous postings. + +John Lange + +On Tue, 2003-01-28 at 17:52, Andras Kadinger wrote: +> I see. +> +> I don't see how performance would be significantly better if you stored +> the common columns of all rows (parent and children) in the parent +> table, in contrast with how it is done now, storing entire rows of child +> tables in the child table and omitting them from the parent table. +> +> Hmm, reviewing your posts to pgsql-performance, I must admit I cannot +> really see what you feel you are losing performance-wise. +> +> As the discussion on pgsql-performance seems to have died off, would you +> be willing to explain to me? +> +> Regards, +> Andras +> +> John Lange wrote: +> > +> > No, the keyword ONLY will limit selects to that table ONLY. I need to +> > return the rows which are common to all tables. Postgres is doing the +> > work in the correct way, however, the issue is the underlaying design +> > which is terribly inefficient requiring a separate table scan for every +> > child table. +> > +> > Thanks for the suggestion. +> > +> > John Lange +> > +> > On Fri, 2003-01-24 at 14:30, Andras Kadinger wrote: +> > > Hi John, +> > > +> > > Isn't the keyword ONLY is what you are after? +> > > +> > > "EXPLAIN select * from tbl_objects where id = 1;" - this will select +> > > from table tbl_objects and all it's descendant tables. +> > > +> > > "EXPLAIN select * from tbl_objects ONLY where id = 1;" - this will +> > > select from table tbl_objects only. +> > > +> > > Regards, +> > > Andras Kadinger + + +From pgsql-performance-owner@postgresql.org Wed Jan 29 01:37:46 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 29D70479EA8 + for ; + Wed, 29 Jan 2003 00:54:44 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 33BB44776AE + for ; + Wed, 29 Jan 2003 00:05:12 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0T55G5u019548; + Wed, 29 Jan 2003 00:05:16 -0500 (EST) +To: John Lange +Cc: Andras Kadinger , + PostgreSQL +Subject: Re: Query plan and Inheritance. Weird behavior +In-reply-to: <1043810501.3719.28.camel@johnlaptop.darkcore.net> +References: <3E31A255.5250DCF1@surfnonstop.com> + <1043770598.2045.23.camel@johnlaptop.darkcore.net> + <3E3717A4.CAD034EC@surfnonstop.com> + <1043810501.3719.28.camel@johnlaptop.darkcore.net> +Comments: In-reply-to John Lange + message dated "28 Jan 2003 21:21:41 -0600" +Date: Wed, 29 Jan 2003 00:05:15 -0500 +Message-ID: <19547.1043816715@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/376 +X-Sequence-Number: 1023 + +John Lange writes: +> Firstly, from the simple standpoint of database normalization you +> shouldn't have tables that have the same columns. The way it is +> implemented, child tables are copies of parent tables. + +There is no copied data though. Or are you saying that if any table +in the database has, say, a timestamp column, then it's a failure of +normalization for any other one to have a timestamp column? Don't think +I buy that. + +> But more importantly it is bad for performance because selecting from a +> parent table causes the same select to be done on all the child tables. + +So? The same amount of data gets scanned either way. To the extent +that the planner fails to generate an optimal plan in such cases, we +have a performance problem --- but that's just an implementation +shortcoming, not a fundamental limitation AFAICS. + +The only real disadvantage I can see to the current storage scheme is +that we can't easily make an index that covers both a parent and all its +children; the index would have to include a table pointer as well as a +row pointer. This creates problems for foreign keys and unique constraints. +But there is more than one way to attack that. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Wed Jan 29 03:25:09 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5F6D2477109 + for ; + Wed, 29 Jan 2003 03:14:07 -0500 (EST) +Received: from ms-smtp-01.texas.rr.com (ms-smtp-01.texas.rr.com + [24.93.36.229]) + by postgresql.org (Postfix) with ESMTP id B8FA147A11A + for ; + Wed, 29 Jan 2003 01:22:53 -0500 (EST) +Received: from spaceship.com (cs24243214-140.austin.rr.com [24.243.214.140]) + by ms-smtp-01.texas.rr.com (8.12.5/8.12.2) with ESMTP id h0T6I0Hs016054 + for ; + Wed, 29 Jan 2003 01:18:00 -0500 (EST) +Message-ID: <3E37733D.90205@spaceship.com> +Date: Wed, 29 Jan 2003 00:22:53 -0600 +From: Matt Mello +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: pgsql-performance +Subject: 1 char in the world +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/377 +X-Sequence-Number: 1024 + +TEXT vs "char" ... vs BOOLEAN + +I am porting from Informix to PG. In doing so, I had to pick some data +types for fields, and began wondering about the performance of char/text +fields with one character. For example, I have a field which has one of +the following values/states: {'A', 'D', 'F', 'U'}. Since CHAR(n), +VARCHAR, and TEXT are all supposed to have the same performance +according to the docs, it seems that they will all perform the same. +For this reason, I did not squabble over which one of these to use. +However, since "char" is implemented differently, I thought I would +compare it to one of the others. I chose to pit TEXT against "char". + +Test query = explain analyze select count(*) from table where onechar='D'; +Table size = 512 wide [mostly TEXT] * 400000 rows +Performance averages: + "char" 44ms + TEXT 63ms + +This seems somewhat reasonable, and makes me want to use "char" for my +single-char field. Does everyone else find this to be reasonable? Is +this pretty much the behavior I can expect on extraordinarily large +tables, too? And, should I worry about things like the backend +developers removing "char" as a type later? + +-- + +This naturally led me to another question. How do TEXT, "char", and +BOOLEAN compare for storing t/f values. The test results I saw were +surprising. + +Test query= + "char"/TEXT: explain analyze select count(*) from table where bool='Y'; + boolean: explain analyze select count(*) from table where bool=true; +Table size (see above) +Performance averages: + TEXT 24ms + BOOLEAN 28ms +"char" 17ms + +Why does boolean rate closer to TEXT than "char"? I would think that +BOOLEANs would actually be stored like "char"s to prevent using the +extra 4 bytes with TEXT types. + +Based on these results, I will probably store my booleans as "char" +instead of boolean. I don't use stored procedures with my application +server, so I should never need my booleans to be the BOOLEAN type. I +can convert faster in my own code. + +-- + +NOTE: the above tests all had the same relative data in the different +fields (what was in TEXT could be found in "char", etc.) and were all +indexed equally. + + +Thanks! + +-- +Matt Mello + + + + + +From pgsql-performance-owner@postgresql.org Wed Jan 29 04:22:38 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 59C34477494 + for ; + Wed, 29 Jan 2003 04:03:32 -0500 (EST) +Received: from ogoun.tvnet.hu (ogoun.tvnet.hu [195.38.96.10]) + by postgresql.org (Postfix) with ESMTP id CEBAB479F0F + for ; + Wed, 29 Jan 2003 02:52:33 -0500 (EST) +Received: from surfnonstop.com (kadinger.telant.tvnet.hu [195.38.114.41]) + by ogoun.tvnet.hu (8.11.6/8.11.6) with ESMTP id h0T7qKW25887; + Wed, 29 Jan 2003 08:52:21 +0100 +Message-ID: <3E378828.91E23F3D@surfnonstop.com> +Date: Wed, 29 Jan 2003 08:52:08 +0100 +From: Andras Kadinger +X-Mailer: Mozilla 4.78 [en] (X11; U; Linux 2.4.19 i686) +X-Accept-Language: hu, en, de +MIME-Version: 1.0 +To: John Lange +Cc: PostgreSQL +Subject: Re: Query plan and Inheritance. Weird behavior +References: <3E31A255.5250DCF1@surfnonstop.com> + <1043770598.2045.23.camel@johnlaptop.darkcore.net> + <3E3717A4.CAD034EC@surfnonstop.com> + <1043810501.3719.28.camel@johnlaptop.darkcore.net> +Content-Type: text/plain; charset=iso-8859-2 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/378 +X-Sequence-Number: 1025 + +John Lange wrote: +> +> > I don't see how performance would be significantly better if you stored +> > the common columns of all rows (parent and children) in the parent +> > table, in contrast with how it is done now, storing entire rows of child +> > tables in the child table and omitting them from the parent table. +> +> Well there are a couple of points. +> +> Firstly, from the simple standpoint of database normalization you +> shouldn't have tables that have the same columns. The way it is +> implemented, child tables are copies of parent tables. + +As Tom pointed out, only the schema is copied, but not the data. + +This has the following advantages: +- if you select from child tables, PostgreSQL will only have to scan +rows that belong to that child (and further down), and not all rows in +all tables of the inheritance hierarchy; so if you have 100 million rows +in the whole hierarchy, but only have say 1 million in the child you are +currently interested in, you only have to scan those 1 million rows, and +not the whole 100 million. +- all columns of rows are stored together, so to read a row only one +disk access is needed (your way it would probably need roughly one +random disk access per each inheritance level upwards, both for +reads/selects and writes/inserts/updates; with a sizable inheritance +hierarchy this would be a considerable performance hit) +- it doesn't really cost much in terms of disk space, only some +bookkeeping information is needed + +I don't think inheritance really fits into 'database normalization' +itself, but still there are cases where it is more convenient/efficient +than with traditional database normalization, where you would have to +either go create completely separate tables for each type (and do UNIONs +of SELECTs if you are interested in more than one child only), or what's +even more cumbersome, create a table with common columns ('parent' here) +and then go create children and children of children that each link +upwards to their respective parents through some kind of key: in a +select, you would have to explicitly specify all tables upwards the +inheritance hierarchy, and specify the respective joins for them. + +So I think whether you should choose more traditional database +normalization or use inheritance depends on what you want to do. + +> But more importantly it is bad for performance because selecting from a +> parent table causes the same select to be done on all the child tables. +> In my case selecting from the parent causes six selects to be done (one +> for every child table). + +'causes the same select to be done on all the child tables' - I don't +agree with that, and I hope this is where the misunderstanding lies. + +Consider this: + +CREATE TABLE parent ( id integer NOT NULL, text text); +CREATE TABLE child1 ( child1field text) INHERITS (parent); +CREATE TABLE child2 ( child2field text) INHERITS (parent); +CREATE TABLE child3 ( child3field text) INHERITS (parent); +CREATE TABLE child4 ( child4field text) INHERITS (parent); + +CREATE TABLE othertable ( id integer NOT NULL, othertext text); + +ALTER TABLE ONLY parent ADD CONSTRAINT parent_pkey PRIMARY KEY (id); +ALTER TABLE ONLY child1 ADD CONSTRAINT child1_pkey PRIMARY KEY (id); +ALTER TABLE ONLY child2 ADD CONSTRAINT child2_pkey PRIMARY KEY (id); +ALTER TABLE ONLY child3 ADD CONSTRAINT child3_pkey PRIMARY KEY (id); +ALTER TABLE ONLY child4 ADD CONSTRAINT child4_pkey PRIMARY KEY (id); + +ALTER TABLE ONLY othertable ADD CONSTRAINT othertable_pkey PRIMARY KEY +(id); + +Then I filled all tables with 10000 rows of synthetic data and ANALYZEd +just to make sure the optimizer considers indexes to be valuable. + +First I tried this: + +johnlange=# explain select * from parent where id=13; + QUERY +PLAN +---------------------------------------------------------------------------------------------- + Result (cost=0.00..15.07 rows=5 width=36) + -> Append (cost=0.00..15.07 rows=5 width=36) + -> Index Scan using parent_pkey on parent (cost=0.00..3.01 +rows=1 width=36) + Index Cond: (id = 13) + -> Index Scan using child1_pkey on child1 parent +(cost=0.00..3.01 rows=1 width=36) + Index Cond: (id = 13) + -> Index Scan using child2_pkey on child2 parent +(cost=0.00..3.01 rows=1 width=36) + Index Cond: (id = 13) + -> Index Scan using child3_pkey on child3 parent +(cost=0.00..3.01 rows=1 width=36) + Index Cond: (id = 13) + -> Index Scan using child4_pkey on child4 parent +(cost=0.00..3.01 rows=1 width=36) + Index Cond: (id = 13) +(12 rows) + +The planner has rightly chosen to use indexes, and as a result the query +will be pretty fast. + +Also, at first sight this might look like the multiple selects you +mention, but actually it isn't; here's another example to show that: + +inh=# explain select * from parent natural join othertable where +parent.id=13; + QUERY +PLAN +---------------------------------------------------------------------------------------------- + Nested Loop (cost=0.00..30.20 rows=5 width=72) + -> Append (cost=0.00..15.07 rows=5 width=36) + -> Index Scan using parent_pkey on parent (cost=0.00..3.01 +rows=1 width=36) + Index Cond: (id = 13) + -> Index Scan using child1_pkey on child1 parent +(cost=0.00..3.01 rows=1 width=36) + Index Cond: (id = 13) + -> Index Scan using child2_pkey on child2 parent +(cost=0.00..3.01 rows=1 width=36) + Index Cond: (id = 13) + -> Index Scan using child3_pkey on child3 parent +(cost=0.00..3.01 rows=1 width=36) + Index Cond: (id = 13) + -> Index Scan using child4_pkey on child4 parent +(cost=0.00..3.01 rows=1 width=36) + Index Cond: (id = 13) + -> Index Scan using othertable_pkey on othertable (cost=0.00..3.01 +rows=1 width=36) + Index Cond: ("outer".id = othertable.id) +(14 rows) + +As you can see, the planner decided to use the indexes on parent and +children here too, retrieved and then collated the resulting rows first +and only then performed the join against othertable. + +In other words, it is not peforming 5 separate selects with their +respective joins; it collects all qualifying rows first from the +inheritance hierarchy, and only then performs the join; so the extra +cost compared to the non-inheriting case is pretty much only the added +cost of consulting five indexes instead of just one - unless you have +inheritance hierarchies consisting of several dozen tables or more (and +even then) I don't think this added cost would be significant. + +> This is entirely reasonable and efficient compared to the current model +> where a select on a parent table requires the same select to be executed +> on EVERY child table. If it's a large expensive JOIN of some kind then +> this is verging on un-workable. + +Please show us a join that you would like to use and let us see how well +the planner handles it. + +Regards, +Andras + +PS (John, don't look here :) ): I have found some queries with plans +that are less efficient than I think they could be. + +Changing the where clause in the above query to refer to othertable +gives: + +johnlange=# explain select * from parent natural join othertable where +othertable.id=13; + QUERY +PLAN +----------------------------------------------------------------------------------------------- + Hash Join (cost=3.02..978.08 rows=5 width=72) + Hash Cond: ("outer".id = "inner".id) + -> Append (cost=0.00..725.00 rows=50000 width=36) + -> Seq Scan on parent (cost=0.00..145.00 rows=10000 width=36) + -> Seq Scan on child1 parent (cost=0.00..145.00 rows=10000 +width=36) + -> Seq Scan on child2 parent (cost=0.00..145.00 rows=10000 +width=36) + -> Seq Scan on child3 parent (cost=0.00..145.00 rows=10000 +width=36) + -> Seq Scan on child4 parent (cost=0.00..145.00 rows=10000 +width=36) + -> Hash (cost=3.01..3.01 rows=1 width=36) + -> Index Scan using othertable_pkey on othertable +(cost=0.00..3.01 rows=1 width=36) + Index Cond: (id = 13) +(11 rows) + +While: + +johnlange=# explain select * from ONLY parent natural join othertable +where othertable.id=13; + QUERY +PLAN +----------------------------------------------------------------------------------------- + Nested Loop (cost=0.00..6.04 rows=1 width=72) + -> Index Scan using othertable_pkey on othertable (cost=0.00..3.01 +rows=1 width=36) + Index Cond: (id = 13) + -> Index Scan using parent_pkey on parent (cost=0.00..3.01 rows=1 +width=36) + Index Cond: (parent.id = "outer".id) +(5 rows) + +Similarly, as a somewhat more real-life example: + +johnlange=# explain select * from parent natural join othertable where +othertable.othertext='apple'; + QUERY +PLAN +-------------------------------------------------------------------------------------------------- + Hash Join (cost=131.37..1234.50 rows=250 width=72) + Hash Cond: ("outer".id = "inner".id) + -> Append (cost=0.00..725.00 rows=50000 width=36) + -> Seq Scan on parent (cost=0.00..145.00 rows=10000 width=36) + -> Seq Scan on child1 parent (cost=0.00..145.00 rows=10000 +width=36) + -> Seq Scan on child2 parent (cost=0.00..145.00 rows=10000 +width=36) + -> Seq Scan on child3 parent (cost=0.00..145.00 rows=10000 +width=36) + -> Seq Scan on child4 parent (cost=0.00..145.00 rows=10000 +width=36) + -> Hash (cost=131.25..131.25 rows=50 width=36) + -> Index Scan using othertable_text on othertable +(cost=0.00..131.25 rows=50 width=36) + Index Cond: (othertext = 'alma'::text) +(11 rows) + +What's more strange, that it still does it with enable_seqscan set to +off: + +johnlange=# explain select * from parent natural join othertable where +othertable.othertext='apple'; + QUERY +PLAN +-------------------------------------------------------------------------------------------------- + Hash Join (cost=100000131.37..500001234.50 rows=250 width=72) + Hash Cond: ("outer".id = "inner".id) + -> Append (cost=100000000.00..500000725.00 rows=50000 width=36) + -> Seq Scan on parent (cost=100000000.00..100000145.00 +rows=10000 width=36) + -> Seq Scan on child1 parent (cost=100000000.00..100000145.00 +rows=10000 width=36) + -> Seq Scan on child2 parent (cost=100000000.00..100000145.00 +rows=10000 width=36) + -> Seq Scan on child3 parent (cost=100000000.00..100000145.00 +rows=10000 width=36) + -> Seq Scan on child4 parent (cost=100000000.00..100000145.00 +rows=10000 width=36) + -> Hash (cost=131.25..131.25 rows=50 width=36) + -> Index Scan using othertable_text on othertable +(cost=0.00..131.25 rows=50 width=36) + Index Cond: (othertext = 'apple'::text) +(11 rows) + +While: + +johnlange=# explain select * from ONLY parent natural join othertable +where othertable.othertext='apple'; + QUERY +PLAN +-------------------------------------------------------------------------------------------- + Nested Loop (cost=0.00..282.55 rows=50 width=72) + -> Index Scan using othertable_text on othertable +(cost=0.00..131.25 rows=50 width=36) + Index Cond: (othertext = 'apple'::text) + -> Index Scan using parent_pkey on parent (cost=0.00..3.01 rows=1 +width=36) + Index Cond: (parent.id = "outer".id) +(5 rows) + +If I try to make it more efficient and get rid of the seq scans by +pushing the condition into a subselect, I get an even more interesting +plan: + +johnlange=# explain select * from parent where id in (select id from +othertable where othertext='alma'); + QUERY +PLAN +--------------------------------------------------------------------------------------------------------------- + Result (cost=0.00..6563171.43 rows=25000 width=36) + -> Append (cost=0.00..6563171.43 rows=25000 width=36) + -> Seq Scan on parent (cost=0.00..1312634.29 rows=5000 +width=36) + Filter: (subplan) + SubPlan + -> Materialize (cost=131.25..131.25 rows=50 width=4) + -> Index Scan using othertable_text on +othertable (cost=0.00..131.25 rows=50 width=4) + Index Cond: (othertext = 'alma'::text) + -> Seq Scan on child1 parent (cost=0.00..1312634.29 rows=5000 +width=36) + Filter: (subplan) + SubPlan + -> Materialize (cost=131.25..131.25 rows=50 width=4) + -> Index Scan using othertable_text on +othertable (cost=0.00..131.25 rows=50 width=4) + Index Cond: (othertext = 'alma'::text) + -> Seq Scan on child2 parent (cost=0.00..1312634.29 rows=5000 +width=36) + Filter: (subplan) + SubPlan + -> Materialize (cost=131.25..131.25 rows=50 width=4) + -> Index Scan using othertable_text on +othertable (cost=0.00..131.25 rows=50 width=4) + Index Cond: (othertext = 'alma'::text) + -> Seq Scan on child3 parent (cost=0.00..1312634.29 rows=5000 +width=36) + Filter: (subplan) + SubPlan + -> Materialize (cost=131.25..131.25 rows=50 width=4) + -> Index Scan using othertable_text on +othertable (cost=0.00..131.25 rows=50 width=4) + Index Cond: (othertext = 'alma'::text) + -> Seq Scan on child4 parent (cost=0.00..1312634.29 rows=5000 +width=36) + Filter: (subplan) + SubPlan + -> Materialize (cost=131.25..131.25 rows=50 width=4) + -> Index Scan using othertable_text on +othertable (cost=0.00..131.25 rows=50 width=4) + Index Cond: (othertext = 'alma'::text) +(32 rows) + +johnlange=# select version(); + +version +-------------------------------------------------------------------------------------------------------- + PostgreSQL 7.3.1 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.2.1 +(Mandrake Linux 9.1 3.2.1-2mdk) +(1 row) + +From pgsql-performance-owner@postgresql.org Wed Jan 29 05:50:40 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C2B93476414 + for ; + Wed, 29 Jan 2003 05:50:39 -0500 (EST) +Received: from mail005.syd.optusnet.com.au (mail005.syd.optusnet.com.au + [210.49.20.136]) + by postgresql.org (Postfix) with ESMTP id 6E313477415 + for ; + Wed, 29 Jan 2003 05:20:14 -0500 (EST) +Received: from postgresql.org (adlax2-107.dialup.optusnet.com.au + [198.142.52.107]) + by mail005.syd.optusnet.com.au (8.11.1/8.11.1) with ESMTP id + h0TAJsc02275; Wed, 29 Jan 2003 21:19:55 +1100 +Message-ID: <3E37AAD0.8010606@postgresql.org> +Date: Wed, 29 Jan 2003 20:50:00 +1030 +From: Justin Clift +User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; + rv:1.2.1) Gecko/20021130 +X-Accept-Language: en-us, en +MIME-Version: 1.0 +To: Matt Mello +Cc: pgsql-performance +Subject: Re: 1 char in the world +References: <3E37733D.90205@spaceship.com> +In-Reply-To: <3E37733D.90205@spaceship.com> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/379 +X-Sequence-Number: 1026 + +Matt Mello wrote: + +> This naturally led me to another question. How do TEXT, "char", and +> BOOLEAN compare for storing t/f values. The test results I saw were +> surprising. +> +> Test query= +> "char"/TEXT: explain analyze select count(*) from table where bool='Y'; +> boolean: explain analyze select count(*) from table where bool=true; +> Table size (see above) +> Performance averages: +> TEXT 24ms +> BOOLEAN 28ms +> "char" 17ms + +Hi Matt, + +This is interesting. As a thought, would you be ok to run the same test +using int4 and int8 as well? + +That would probably round out the test nicely. + +:) + +Regards and best wishes, + +Justin Clift + +-- +"My grandfather once told me that there are two kinds of people: those +who work and those who take the credit. He told me to try to be in the +first group; there was less competition there." +- Indira Gandhi + + +From pgsql-performance-owner@postgresql.org Wed Jan 29 05:53:59 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5EB08476B0C + for ; + Wed, 29 Jan 2003 05:53:58 -0500 (EST) +Received: from localhost.localdomain (sein.itera.ee [194.126.109.126]) + by postgresql.org (Postfix) with ESMTP id 87262476E95 + for ; + Wed, 29 Jan 2003 05:25:17 -0500 (EST) +Received: (from hannu@localhost) + by localhost.localdomain (8.11.6/8.11.6) id h0TCIKI05048; + Wed, 29 Jan 2003 12:18:20 GMT +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: 1 char in the world +From: Hannu Krosing +To: Matt Mello +Cc: pgsql-performance +In-Reply-To: <3E37733D.90205@spaceship.com> +References: <3E37733D.90205@spaceship.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1043842700.5008.11.camel@huli> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 29 Jan 2003 12:18:20 +0000 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/380 +X-Sequence-Number: 1027 + +On Wed, 2003-01-29 at 06:22, Matt Mello wrote: +> TEXT vs "char" ... vs BOOLEAN +> +> I am porting from Informix to PG. In doing so, I had to pick some data +> types for fields, and began wondering about the performance of char/text +> fields with one character. For example, I have a field which has one of +> the following values/states: {'A', 'D', 'F', 'U'}. Since CHAR(n), +> VARCHAR, and TEXT are all supposed to have the same performance +> according to the docs, it seems that they will all perform the same. +> For this reason, I did not squabble over which one of these to use. +> However, since "char" is implemented differently, I thought I would +> compare it to one of the others. I chose to pit TEXT against "char". +> +> Test query = explain analyze select count(*) from table where onechar='D'; +> Table size = 512 wide [mostly TEXT] * 400000 rows +> Performance averages: +> "char" 44ms +> TEXT 63ms +> +> This seems somewhat reasonable, and makes me want to use "char" for my +> single-char field. Does everyone else find this to be reasonable? Is +> this pretty much the behavior I can expect on extraordinarily large +> tables, too? + +The actual compares will likely stay faster for char than for text. + +OTOH the actual storage of one-char datatype should not play so +significant role for very large tables, even if this is the only field +in that table, as most of the overhead will be in other places - storage +overhead in page/tuple headers, performance in retrieving the +pages/tuples and cache lookups, etc. + +Also, for very big tables you will most likely want to restrict selects +on other criteria than a 4-valued field, so that indexes could be used +in retrieving data. + +> And, should I worry about things like the backend +> developers removing "char" as a type later? +> +> -- +> +> This naturally led me to another question. How do TEXT, "char", and +> BOOLEAN compare for storing t/f values. The test results I saw were +> surprising. +> +> Test query= +> "char"/TEXT: explain analyze select count(*) from table where bool='Y'; + +You could also try just + +select count(*) from table where bool; + +> boolean: explain analyze select count(*) from table where bool=true; +> Table size (see above) +> Performance averages: +> TEXT 24ms +> BOOLEAN 28ms +> "char" 17ms +> +> Why does boolean rate closer to TEXT than "char"? I would think that +> BOOLEANs would actually be stored like "char"s to prevent using the +> extra 4 bytes with TEXT types. +> +> Based on these results, I will probably store my booleans as "char" +> instead of boolean. I don't use stored procedures with my application +> server, so I should never need my booleans to be the BOOLEAN type. I +> can convert faster in my own code. +> +> -- +> +> NOTE: the above tests all had the same relative data in the different +> fields (what was in TEXT could be found in "char", etc.) and were all +> indexed equally. + +Did you repeat the texts enough times to be sure that you get reliable +results ? + +> +> Thanks! +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Wed Jan 29 10:58:26 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 063E847702C + for ; + Wed, 29 Jan 2003 10:58:26 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 40372476F54 + for ; + Wed, 29 Jan 2003 10:56:23 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0TFuR5u026668; + Wed, 29 Jan 2003 10:56:27 -0500 (EST) +To: Matt Mello +Cc: pgsql-performance +Subject: Re: 1 char in the world +In-reply-to: <3E37733D.90205@spaceship.com> +References: <3E37733D.90205@spaceship.com> +Comments: In-reply-to Matt Mello + message dated "Wed, 29 Jan 2003 00:22:53 -0600" +Date: Wed, 29 Jan 2003 10:56:27 -0500 +Message-ID: <26667.1043855787@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/381 +X-Sequence-Number: 1028 + +Matt Mello writes: +> Test query= +> "char"/TEXT: explain analyze select count(*) from table where bool='Y'; +> boolean: explain analyze select count(*) from table where bool=true; +> Table size (see above) +> Performance averages: +> TEXT 24ms +> BOOLEAN 28ms +> "char" 17ms + +I don't believe those numbers for a moment. All else being equal, +comparing a "char" field to a literal should be exactly the same speed +as comparing a bool field to a literal (and if you'd just said "where bool", +the bool field would be faster). Both ought to be markedly faster than +text. + +Look for errors in your test procedure. One thing I'd particularly +wonder about is whether the query plans are the same. In the absence of +any VACUUM ANALYZE data, I'd fully expect the planner to pick a +different plan for a bool field than text/char --- because even without +ANALYZE data, it knows that a bool column has only two possible values. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Wed Jan 29 13:30:36 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D0AED476860 + for ; + Wed, 29 Jan 2003 13:30:33 -0500 (EST) +Received: from johnlaptop.darkcore.net (link.clearoption.com [205.200.121.81]) + by postgresql.org (Postfix) with ESMTP id 9548E477206 + for ; + Wed, 29 Jan 2003 13:29:01 -0500 (EST) +Received: by johnlaptop.darkcore.net (Postfix, from userid 501) + id A7B3AF2497; Wed, 29 Jan 2003 13:29:00 -0500 (EST) +Subject: Re: Query plan and Inheritance. Weird behavior +From: John Lange +To: Andras Kadinger +Cc: PostgreSQL +In-Reply-To: <3E378828.91E23F3D@surfnonstop.com> +References: <3E31A255.5250DCF1@surfnonstop.com> + <1043770598.2045.23.camel@johnlaptop.darkcore.net> + <3E3717A4.CAD034EC@surfnonstop.com> + <1043810501.3719.28.camel@johnlaptop.darkcore.net> + <3E378828.91E23F3D@surfnonstop.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +X-Mailer: Ximian Evolution 1.0.8-3mdk +Date: 29 Jan 2003 12:29:00 -0600 +Message-Id: <1043864940.2368.53.camel@johnlaptop.darkcore.net> +Mime-Version: 1.0 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/382 +X-Sequence-Number: 1029 + +On Wed, 2003-01-29 at 01:52, Andras Kadinger wrote: +> John Lange wrote: +> > +> > > I don't see how performance would be significantly better if you stored +> > > the common columns of all rows (parent and children) in the parent +> > > table, in contrast with how it is done now, storing entire rows of child +> > > tables in the child table and omitting them from the parent table. +> > +> > Well there are a couple of points. +> > +> > Firstly, from the simple standpoint of database normalization you +> > shouldn't have tables that have the same columns. The way it is +> > implemented, child tables are copies of parent tables. +> +> As Tom pointed out, only the schema is copied, but not the data. + +I guess you are right, strictly speaking this isn't a violation of +normalization since no data is duplicated. + +> This has the following advantages: +> - if you select from child tables, PostgreSQL will only have to scan +> rows that belong to that child (and further down), and not all rows in +> all tables of the inheritance hierarchy; so if you have 100 million rows +> in the whole hierarchy, but only have say 1 million in the child you are +> currently interested in, you only have to scan those 1 million rows, and +> not the whole 100 million. +> - all columns of rows are stored together, so to read a row only one +> disk access is needed (your way it would probably need roughly one +> random disk access per each inheritance level upwards, both for +> reads/selects and writes/inserts/updates; with a sizable inheritance +> hierarchy this would be a considerable performance hit) +> - it doesn't really cost much in terms of disk space, only some +> bookkeeping information is needed +> +> I don't think inheritance really fits into 'database normalization' +> itself, but still there are cases where it is more convenient/efficient +> than with traditional database normalization, where you would have to +> either go create completely separate tables for each type (and do UNIONs +> of SELECTs if you are interested in more than one child only), or what's +> even more cumbersome, create a table with common columns ('parent' here) +> and then go create children and children of children that each link +> upwards to their respective parents through some kind of key: in a +> select, you would have to explicitly specify all tables upwards the +> inheritance hierarchy, and specify the respective joins for them. +> +> So I think whether you should choose more traditional database +> normalization or use inheritance depends on what you want to do. +> +> > But more importantly it is bad for performance because selecting from a +> > parent table causes the same select to be done on all the child tables. +> > In my case selecting from the parent causes six selects to be done (one +> > for every child table). +> +> 'causes the same select to be done on all the child tables' - I don't +> agree with that, and I hope this is where the misunderstanding lies. +> +> Consider this: +> +> CREATE TABLE parent ( id integer NOT NULL, text text); +> CREATE TABLE child1 ( child1field text) INHERITS (parent); +> CREATE TABLE child2 ( child2field text) INHERITS (parent); +> CREATE TABLE child3 ( child3field text) INHERITS (parent); +> CREATE TABLE child4 ( child4field text) INHERITS (parent); +> +> CREATE TABLE othertable ( id integer NOT NULL, othertext text); +> +> ALTER TABLE ONLY parent ADD CONSTRAINT parent_pkey PRIMARY KEY (id); +> ALTER TABLE ONLY child1 ADD CONSTRAINT child1_pkey PRIMARY KEY (id); +> ALTER TABLE ONLY child2 ADD CONSTRAINT child2_pkey PRIMARY KEY (id); +> ALTER TABLE ONLY child3 ADD CONSTRAINT child3_pkey PRIMARY KEY (id); +> ALTER TABLE ONLY child4 ADD CONSTRAINT child4_pkey PRIMARY KEY (id); +> +> ALTER TABLE ONLY othertable ADD CONSTRAINT othertable_pkey PRIMARY KEY +> (id); +> +> Then I filled all tables with 10000 rows of synthetic data and ANALYZEd +> just to make sure the optimizer considers indexes to be valuable. +> +> First I tried this: +> +> johnlange=# explain select * from parent where id=13; +> QUERY +> PLAN +> ---------------------------------------------------------------------------------------------- +> Result (cost=0.00..15.07 rows=5 width=36) +> -> Append (cost=0.00..15.07 rows=5 width=36) +> -> Index Scan using parent_pkey on parent (cost=0.00..3.01 +> rows=1 width=36) +> Index Cond: (id = 13) +> -> Index Scan using child1_pkey on child1 parent +> (cost=0.00..3.01 rows=1 width=36) +> Index Cond: (id = 13) +> -> Index Scan using child2_pkey on child2 parent +> (cost=0.00..3.01 rows=1 width=36) +> Index Cond: (id = 13) +> -> Index Scan using child3_pkey on child3 parent +> (cost=0.00..3.01 rows=1 width=36) +> Index Cond: (id = 13) +> -> Index Scan using child4_pkey on child4 parent +> (cost=0.00..3.01 rows=1 width=36) +> Index Cond: (id = 13) +> (12 rows) +> +> The planner has rightly chosen to use indexes, and as a result the query +> will be pretty fast. +> +> Also, at first sight this might look like the multiple selects you +> mention, but actually it isn't; here's another example to show that: +> +> inh=# explain select * from parent natural join othertable where +> parent.id=13; +> QUERY +> PLAN +> ---------------------------------------------------------------------------------------------- +> Nested Loop (cost=0.00..30.20 rows=5 width=72) +> -> Append (cost=0.00..15.07 rows=5 width=36) +> -> Index Scan using parent_pkey on parent (cost=0.00..3.01 +> rows=1 width=36) +> Index Cond: (id = 13) +> -> Index Scan using child1_pkey on child1 parent +> (cost=0.00..3.01 rows=1 width=36) +> Index Cond: (id = 13) +> -> Index Scan using child2_pkey on child2 parent +> (cost=0.00..3.01 rows=1 width=36) +> Index Cond: (id = 13) +> -> Index Scan using child3_pkey on child3 parent +> (cost=0.00..3.01 rows=1 width=36) +> Index Cond: (id = 13) +> -> Index Scan using child4_pkey on child4 parent +> (cost=0.00..3.01 rows=1 width=36) +> Index Cond: (id = 13) +> -> Index Scan using othertable_pkey on othertable (cost=0.00..3.01 +> rows=1 width=36) +> Index Cond: ("outer".id = othertable.id) +> (14 rows) +> +> As you can see, the planner decided to use the indexes on parent and +> children here too, retrieved and then collated the resulting rows first +> and only then performed the join against othertable. +> +> In other words, it is not peforming 5 separate selects with their +> respective joins; it collects all qualifying rows first from the +> inheritance hierarchy, and only then performs the join; so the extra +> cost compared to the non-inheriting case is pretty much only the added +> cost of consulting five indexes instead of just one - unless you have +> inheritance hierarchies consisting of several dozen tables or more (and +> even then) I don't think this added cost would be significant. +> +> > This is entirely reasonable and efficient compared to the current model +> > where a select on a parent table requires the same select to be executed +> > on EVERY child table. If it's a large expensive JOIN of some kind then +> > this is verging on un-workable. +> +> Please show us a join that you would like to use and let us see how well +> the planner handles it. + +Ok, your reply here is very informative. Firstly, I can see from your +example that I likely don't have my keys and constraints implemented +properly. + +However, the issue of indexes is not necessarily that relevant since you +may not be selecting rows based on columns that have indexes. + +So the issue of indexes aside, I think some of the misunderstanding is +related to my assumption that the appended operations are relatively +more expensive than scanning the same number of rows in a single select. + +Here is the way it looks on my system when I select a single object. + +db_drs0001=> explain select * from tbl_objects where id = 1; +NOTICE: QUERY PLAN: + +Result (cost=0.00..153.70 rows=6 width=111) + -> Append (cost=0.00..153.70 rows=6 width=111) + -> Seq Scan on tbl_objects (cost=0.00..144.35 rows=1 width=107) + -> Seq Scan on tbl_viewers tbl_objects (cost=0.00..1.06 rows=1 +width=97) + -> Seq Scan on tbl_documents tbl_objects (cost=0.00..4.91 rows=1 +width=111) + -> Seq Scan on tbl_formats tbl_objects (cost=0.00..1.11 rows=1 +width=100) + -> Seq Scan on tbl_massemails tbl_objects (cost=0.00..1.01 rows=1 +width=90) + -> Seq Scan on tbl_icons tbl_objects (cost=0.00..1.25 rows=1 +width=110) + +db_drs0001=> select version(); + version +--------------------------------------------------------------- + PostgreSQL 7.2.1 on i686-pc-linux-gnu, compiled by GCC 2.95.3 +(1 row) + +The only question here is, if a select requires the scanning of all rows +to return a result set, is it dramatically less efficient to have it +scanning 100,000 rows spread over 6 tables or to scan 100,000 rows in a +single table? + +(At the moment I have no where near that amount of data. Side question, +what technique do you use to generate data to fill your tables for +testing?) + +I'm now starting to see that it likely isn't that much different either +way so the benefits of the way it's implemented probably out weigh the +negatives. Your end up scanning the same number of rows either way. + +On the topic of proper indexes, if you would indulge me, can you show me +where I have gone wrong in that regard? My biggest point of confusion +here is with regards to the sequences that are used in the parent table. + +Here is the schema as produced by pg_dump. The original create used the +keyword "serial" or "bigserial" as the case may be. I've edited some of +the columns out just to keep the example shorter: + +CREATE SEQUENCE "tbl_objects_id_seq" start 1 increment 1 maxvalue +9223372036854775807 minvalue 1 cache 1; + +CREATE TABLE "tbl_objects" ( + "id" bigint DEFAULT nextval('"tbl_objects_id_seq"'::text) NOT NULL, + "name" text DEFAULT '' NOT NULL, + "description" text DEFAULT '' NOT NULL, + "status" smallint DEFAULT '1' NOT NULL, + "class" text +); + +CREATE TABLE "tbl_viewers" ( + "exec" text DEFAULT '' NOT NULL ) +INHERITS ("tbl_objects"); + +CREATE TABLE "tbl_documents" ( + "filename" text DEFAULT '' NOT NULL ) +INHERITS ("tbl_objects"); + +CREATE TABLE "tbl_massemails" ( + "from" text DEFAULT '' NOT NULL, + "subject" text DEFAULT '' NOT NULL, + "message" text DEFAULT '' NOT NULL ) +INHERITS ("tbl_objects"); + +CREATE TABLE "tbl_icons" ( + "format_id" bigint DEFAULT '0' NOT NULL ) +INHERITS ("tbl_documents"); + +CREATE TABLE "tbl_formats" ( + "viewer_id" bigint DEFAULT '0' NOT NULL, + "extension" text DEFAULT '' NOT NULL, + "contenttype" text DEFAULT '' NOT NULL, + "upload_class" text ) +INHERITS ("tbl_objects"); + +CREATE UNIQUE INDEX tbl_objects_id_key ON tbl_objects USING btree (id); + +Thanks very much for taking the time to look into this with me. It has +been most informative. + +John Lange + +> +> Regards, +> Andras +> +> PS (John, don't look here :) ): I have found some queries with plans +> that are less efficient than I think they could be. +> +> Changing the where clause in the above query to refer to othertable +> gives: +> +> johnlange=# explain select * from parent natural join othertable where +> othertable.id=13; +> QUERY +> PLAN +> ----------------------------------------------------------------------------------------------- +> Hash Join (cost=3.02..978.08 rows=5 width=72) +> Hash Cond: ("outer".id = "inner".id) +> -> Append (cost=0.00..725.00 rows=50000 width=36) +> -> Seq Scan on parent (cost=0.00..145.00 rows=10000 width=36) +> -> Seq Scan on child1 parent (cost=0.00..145.00 rows=10000 +> width=36) +> -> Seq Scan on child2 parent (cost=0.00..145.00 rows=10000 +> width=36) +> -> Seq Scan on child3 parent (cost=0.00..145.00 rows=10000 +> width=36) +> -> Seq Scan on child4 parent (cost=0.00..145.00 rows=10000 +> width=36) +> -> Hash (cost=3.01..3.01 rows=1 width=36) +> -> Index Scan using othertable_pkey on othertable +> (cost=0.00..3.01 rows=1 width=36) +> Index Cond: (id = 13) +> (11 rows) +> +> While: +> +> johnlange=# explain select * from ONLY parent natural join othertable +> where othertable.id=13; +> QUERY +> PLAN +> ----------------------------------------------------------------------------------------- +> Nested Loop (cost=0.00..6.04 rows=1 width=72) +> -> Index Scan using othertable_pkey on othertable (cost=0.00..3.01 +> rows=1 width=36) +> Index Cond: (id = 13) +> -> Index Scan using parent_pkey on parent (cost=0.00..3.01 rows=1 +> width=36) +> Index Cond: (parent.id = "outer".id) +> (5 rows) +> +> Similarly, as a somewhat more real-life example: +> +> johnlange=# explain select * from parent natural join othertable where +> othertable.othertext='apple'; +> QUERY +> PLAN +> -------------------------------------------------------------------------------------------------- +> Hash Join (cost=131.37..1234.50 rows=250 width=72) +> Hash Cond: ("outer".id = "inner".id) +> -> Append (cost=0.00..725.00 rows=50000 width=36) +> -> Seq Scan on parent (cost=0.00..145.00 rows=10000 width=36) +> -> Seq Scan on child1 parent (cost=0.00..145.00 rows=10000 +> width=36) +> -> Seq Scan on child2 parent (cost=0.00..145.00 rows=10000 +> width=36) +> -> Seq Scan on child3 parent (cost=0.00..145.00 rows=10000 +> width=36) +> -> Seq Scan on child4 parent (cost=0.00..145.00 rows=10000 +> width=36) +> -> Hash (cost=131.25..131.25 rows=50 width=36) +> -> Index Scan using othertable_text on othertable +> (cost=0.00..131.25 rows=50 width=36) +> Index Cond: (othertext = 'alma'::text) +> (11 rows) +> +> What's more strange, that it still does it with enable_seqscan set to +> off: +> +> johnlange=# explain select * from parent natural join othertable where +> othertable.othertext='apple'; +> QUERY +> PLAN +> -------------------------------------------------------------------------------------------------- +> Hash Join (cost=100000131.37..500001234.50 rows=250 width=72) +> Hash Cond: ("outer".id = "inner".id) +> -> Append (cost=100000000.00..500000725.00 rows=50000 width=36) +> -> Seq Scan on parent (cost=100000000.00..100000145.00 +> rows=10000 width=36) +> -> Seq Scan on child1 parent (cost=100000000.00..100000145.00 +> rows=10000 width=36) +> -> Seq Scan on child2 parent (cost=100000000.00..100000145.00 +> rows=10000 width=36) +> -> Seq Scan on child3 parent (cost=100000000.00..100000145.00 +> rows=10000 width=36) +> -> Seq Scan on child4 parent (cost=100000000.00..100000145.00 +> rows=10000 width=36) +> -> Hash (cost=131.25..131.25 rows=50 width=36) +> -> Index Scan using othertable_text on othertable +> (cost=0.00..131.25 rows=50 width=36) +> Index Cond: (othertext = 'apple'::text) +> (11 rows) +> +> While: +> +> johnlange=# explain select * from ONLY parent natural join othertable +> where othertable.othertext='apple'; +> QUERY +> PLAN +> -------------------------------------------------------------------------------------------- +> Nested Loop (cost=0.00..282.55 rows=50 width=72) +> -> Index Scan using othertable_text on othertable +> (cost=0.00..131.25 rows=50 width=36) +> Index Cond: (othertext = 'apple'::text) +> -> Index Scan using parent_pkey on parent (cost=0.00..3.01 rows=1 +> width=36) +> Index Cond: (parent.id = "outer".id) +> (5 rows) +> +> If I try to make it more efficient and get rid of the seq scans by +> pushing the condition into a subselect, I get an even more interesting +> plan: +> +> johnlange=# explain select * from parent where id in (select id from +> othertable where othertext='alma'); +> QUERY +> PLAN +> --------------------------------------------------------------------------------------------------------------- +> Result (cost=0.00..6563171.43 rows=25000 width=36) +> -> Append (cost=0.00..6563171.43 rows=25000 width=36) +> -> Seq Scan on parent (cost=0.00..1312634.29 rows=5000 +> width=36) +> Filter: (subplan) +> SubPlan +> -> Materialize (cost=131.25..131.25 rows=50 width=4) +> -> Index Scan using othertable_text on +> othertable (cost=0.00..131.25 rows=50 width=4) +> Index Cond: (othertext = 'alma'::text) +> -> Seq Scan on child1 parent (cost=0.00..1312634.29 rows=5000 +> width=36) +> Filter: (subplan) +> SubPlan +> -> Materialize (cost=131.25..131.25 rows=50 width=4) +> -> Index Scan using othertable_text on +> othertable (cost=0.00..131.25 rows=50 width=4) +> Index Cond: (othertext = 'alma'::text) +> -> Seq Scan on child2 parent (cost=0.00..1312634.29 rows=5000 +> width=36) +> Filter: (subplan) +> SubPlan +> -> Materialize (cost=131.25..131.25 rows=50 width=4) +> -> Index Scan using othertable_text on +> othertable (cost=0.00..131.25 rows=50 width=4) +> Index Cond: (othertext = 'alma'::text) +> -> Seq Scan on child3 parent (cost=0.00..1312634.29 rows=5000 +> width=36) +> Filter: (subplan) +> SubPlan +> -> Materialize (cost=131.25..131.25 rows=50 width=4) +> -> Index Scan using othertable_text on +> othertable (cost=0.00..131.25 rows=50 width=4) +> Index Cond: (othertext = 'alma'::text) +> -> Seq Scan on child4 parent (cost=0.00..1312634.29 rows=5000 +> width=36) +> Filter: (subplan) +> SubPlan +> -> Materialize (cost=131.25..131.25 rows=50 width=4) +> -> Index Scan using othertable_text on +> othertable (cost=0.00..131.25 rows=50 width=4) +> Index Cond: (othertext = 'alma'::text) +> (32 rows) +> +> johnlange=# select version(); +> +> version +> -------------------------------------------------------------------------------------------------------- +> PostgreSQL 7.3.1 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.2.1 +> (Mandrake Linux 9.1 3.2.1-2mdk) +> (1 row) + + +From pgsql-performance-owner@postgresql.org Wed Jan 29 18:29:59 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9346F47600C + for ; + Wed, 29 Jan 2003 18:29:57 -0500 (EST) +Received: from mta4.rcsntx.swbell.net (mta4.rcsntx.swbell.net [151.164.30.28]) + by postgresql.org (Postfix) with ESMTP id C8955476003 + for ; + Wed, 29 Jan 2003 18:29:56 -0500 (EST) +Received: from spaceship.com ([65.65.110.10]) by mta4.rcsntx.swbell.net + (iPlanet Messaging Server 5.1 HotFix 1.6 (built Oct 18 2002)) + with ESMTP id <0H9I00DUE19YXM@mta4.rcsntx.swbell.net> for + pgsql-performance@postgresql.org; Wed, 29 Jan 2003 17:29:59 -0600 (CST) +Date: Wed, 29 Jan 2003 17:29:58 -0600 +From: Matt Mello +Subject: Re: 1 char in the world +In-reply-to: <1043842700.5008.11.camel@huli> +To: pgsql-performance +Message-id: <3E3863F6.2020004@spaceship.com> +MIME-version: 1.0 +Content-type: text/plain; charset=us-ascii; format=flowed +Content-transfer-encoding: 7BIT +X-Accept-Language: en-us, en +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021130 +References: <3E37733D.90205@spaceship.com> <1043842700.5008.11.camel@huli> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/383 +X-Sequence-Number: 1030 + +> OTOH the actual storage of one-char datatype should not play so +> significant role for very large tables, even if this is the only field +> in that table, as most of the overhead will be in other places - storage +> overhead in page/tuple headers, performance in retrieving the +> pages/tuples and cache lookups, etc. + +Is that true if I have a table that consists of lots of 1-char fields? +For example, if I have a table with 4 billion records, which consist of +(20) 1-char fields each, then the storage for the data will be something +like 5 times as large if I use TEXT than if I use "char". + +> Also, for very big tables you will most likely want to restrict selects +> on other criteria than a 4-valued field, so that indexes could be used +> in retrieving data. + +I do. I was just using that query for this test only. I have some very +complex queries that are constrained by many foriegn-key int4 fields, +but also a few of these 1-char fields. + +> You could also try just +> +> select count(*) from table where bool; +> + +I will do this in a while and report to the list. I am going to try +make a reproducable test that anyone can do, to be sure my results are +"real". + +> Did you repeat the texts enough times to be sure that you get reliable +> results ? + +I think so. Not so much as hundreds of times, though. + + +-- +Matt Mello +512-350-6900 + + +From pgsql-performance-owner@postgresql.org Wed Jan 29 18:59:26 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 600ED475E71 + for ; + Wed, 29 Jan 2003 18:59:25 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 8F33E475C22 + for ; + Wed, 29 Jan 2003 18:59:24 -0500 (EST) +Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) + by sss.pgh.pa.us (8.12.6/8.12.6) with ESMTP id h0TNxR5u005514; + Wed, 29 Jan 2003 18:59:27 -0500 (EST) +To: Matt Mello +Cc: pgsql-performance +Subject: Re: 1 char in the world +In-reply-to: <3E3863F6.2020004@spaceship.com> +References: <3E37733D.90205@spaceship.com> <1043842700.5008.11.camel@huli> + <3E3863F6.2020004@spaceship.com> +Comments: In-reply-to Matt Mello + message dated "Wed, 29 Jan 2003 17:29:58 -0600" +Date: Wed, 29 Jan 2003 18:59:26 -0500 +Message-ID: <5513.1043884766@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/384 +X-Sequence-Number: 1031 + +Matt Mello writes: +> Is that true if I have a table that consists of lots of 1-char fields? +> For example, if I have a table with 4 billion records, which consist of +> (20) 1-char fields each, then the storage for the data will be something +> like 5 times as large if I use TEXT than if I use "char". + +Probably more like 8 times as large, when you allow for alignment +padding --- on most machines, TEXT fields will be aligned on 4-byte +boundaries, so several TEXT fields in a row will take up 8 bytes apiece, +vs one byte apiece for consecutive "char" or bool fields. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Wed Jan 29 20:03:04 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8215647595A + for ; + Wed, 29 Jan 2003 20:03:03 -0500 (EST) +Received: from ogoun.tvnet.hu (ogoun.tvnet.hu [195.38.96.10]) + by postgresql.org (Postfix) with ESMTP id 47C424758BD + for ; + Wed, 29 Jan 2003 20:03:02 -0500 (EST) +Received: from surfnonstop.com (kadinger.telant.tvnet.hu [195.38.114.41]) + by ogoun.tvnet.hu (8.11.6/8.11.6) with ESMTP id h0U12sW29716; + Thu, 30 Jan 2003 02:02:55 +0100 +Message-ID: <3E3879B9.F9060B14@surfnonstop.com> +Date: Thu, 30 Jan 2003 02:02:49 +0100 +From: Andras Kadinger +X-Mailer: Mozilla 4.78 [en] (X11; U; Linux 2.4.19 i686) +X-Accept-Language: hu, en, de +MIME-Version: 1.0 +To: John Lange +Cc: PostgreSQL +Subject: Re: Query plan and Inheritance. Weird behavior +References: <3E31A255.5250DCF1@surfnonstop.com> + <1043770598.2045.23.camel@johnlaptop.darkcore.net> + <3E3717A4.CAD034EC@surfnonstop.com> + <1043810501.3719.28.camel@johnlaptop.darkcore.net> + <3E378828.91E23F3D@surfnonstop.com> + <1043864940.2368.53.camel@johnlaptop.darkcore.net> +Content-Type: text/plain; charset=iso-8859-2 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/385 +X-Sequence-Number: 1032 + +John Lange wrote: +> +> On Wed, 2003-01-29 at 01:52, Andras Kadinger wrote: +> > As Tom pointed out, only the schema is copied, but not the data. +> +> I guess you are right, strictly speaking this isn't a violation of +> normalization since no data is duplicated. + +[...] + +> Ok, your reply here is very informative. Firstly, I can see from your +> example that I likely don't have my keys and constraints implemented +> properly. +> +> However, the issue of indexes is not necessarily that relevant since you +> may not be selecting rows based on columns that have indexes. + +Granted, now I see that was not strictly related to your point, I just +wanted to avoid most avoidable objections against performance of +inheritance, and I wasn't 100% sure you seeing seq scans was not part of +you thinking performance of this method would be suboptimal so just to +be sure, I explicitly went for an example with indexes. + +> So the issue of indexes aside, I think some of the misunderstanding is +> related to my assumption that the appended operations are relatively +> more expensive than scanning the same number of rows in a single select. + +I see. Well, the Append step itself I suppose is not doing much else +than iterates over its subnodes and asks each of them to return their +rows, and forwards the rows upwards to the rest of the plan as it +receives them - it doesn't buffer them, or collect them all before +forwarding them upwards (I think the Materialize step that were to be +seen in an example in my last PS is the one that does that). + +So I don't think the Append incurs any significant costs much more than +a few CPU cycles for that iteration and row forwarding (pass of one +pointer to in-memory row I guess) steps - I think these are minuscule +compared to the cost of any disk I/O, and in most non-CPU-bound queries +are hidden by disk throughput/latency anyway. + +> Here is the way it looks on my system when I select a single object. +> +> db_drs0001=> explain select * from tbl_objects where id = 1; +> NOTICE: QUERY PLAN: +> +> Result (cost=0.00..153.70 rows=6 width=111) +> -> Append (cost=0.00..153.70 rows=6 width=111) +> -> Seq Scan on tbl_objects (cost=0.00..144.35 rows=1 width=107) +> -> Seq Scan on tbl_viewers tbl_objects (cost=0.00..1.06 rows=1 +> width=97) +> -> Seq Scan on tbl_documents tbl_objects (cost=0.00..4.91 rows=1 +> width=111) +> -> Seq Scan on tbl_formats tbl_objects (cost=0.00..1.11 rows=1 +> width=100) +> -> Seq Scan on tbl_massemails tbl_objects (cost=0.00..1.01 rows=1 +> width=90) +> -> Seq Scan on tbl_icons tbl_objects (cost=0.00..1.25 rows=1 +> width=110) +> +> db_drs0001=> select version(); +> version +> --------------------------------------------------------------- +> PostgreSQL 7.2.1 on i686-pc-linux-gnu, compiled by GCC 2.95.3 +> (1 row) +> +> The only question here is, if a select requires the scanning of all rows +> to return a result set, is it dramatically less efficient to have it +> scanning 100,000 rows spread over 6 tables or to scan 100,000 rows in a +> single table? + +I see. Well, the Append step itself I suppose isn't doing much more than +iterates over its subnodes (the seq scans in the case above) and asks +each of them to return rows, and forwards the rows upwards to the rest +of the plan as it receives them - it doesn't buffer them, or collect +them all before forwarding them upwards (I think the Materialize step +that were to be seen in an example in my last PS does that). So aside +for any costs of consulting indexes, I don't think the Append step - +which is the added step when scanning multiple tables versus scanning +one table - incurs any significant costs much more than a few CPU cycles +for those iteration and row forwarding (pass of one pointer to in-memory +row I guess) steps - I think these are minuscule compared to the cost of +any disk I/O, and in most non-CPU-bound queries are hidden by disk +throughput/latency anyway. + +> (At the moment I have no where near that amount of data. Side question, +> what technique do you use to generate data to fill your tables for +> testing?) + +For this occasion I just went and created a dozen-line PHP script that +simply inserted 10000 rows with consecutive ids into each table. + +I suggest you to try to populate your test database with test data on +the order of your expected working data set and use EXPLAIN ANALYZE to +make estimates of expected performance of the database. + +> I'm now starting to see that it likely isn't that much different either +> way so the benefits of the way it's implemented probably out weigh the +> negatives. Your end up scanning the same number of rows either way. + +Aside from extreme cases where child rows are considerably much more +wider than parent rows and thus result in considerably more data needed +to be read in case of a sequential scan, yes. + +> On the topic of proper indexes, if you would indulge me, can you show me +> where I have gone wrong in that regard? + +Hmm, I think you should only have gone and created indexes for child +tables by hand, as indexes are not inherited. + +Also, don't forget, PostgreSQL has an advanced query cost estimation +subsystem, which decides for or against using an index based on, among +others, statistics collected on distribution of values in the index to +determine its selectivity (so don't forget to ANALYZE/VACUUM ANALYZE +after inserting/changing a lot of rows that significantly change +distribution of values - this includes initial table fillup), and also +it accounts for costs of accessing index pages, so with less than say a +couple of thousand rows or with not very selective indexes it will +(rightly) decide not to use the index but do a seq scan instead - +probably the reason for why you don't see an index scan on tbl_objects +above despite there being an index on the primary key. + +> My biggest point of confusion +> here is with regards to the sequences that are used in the parent table. + +Child tables inherit the "nextval('...')" default value, so as a result +they will all draw from the same one sequence, which sequence exists +outside of the tables; as a result as long as you use that default +value, it is guaranteed that the column in question will have unique +values among all tables parent and children; they won't be consecutive - +but that's not a drawback of inheritance either, as a sequence is not +guaranteed to provide consecutive numbers with single tables either due +to transaction concurrency (rolled back transactions don't 'put back' +numbers into the sequence, so in the case of rolled back transactions +there will be numbers drawn from the sequence that never actually get +into any table - this is nicely documented with sequences and +transactions). + +> Here is the schema as produced by pg_dump. The original create used the +> keyword "serial" or "bigserial" as the case may be. I've edited some of +> the columns out just to keep the example shorter: +> +> CREATE SEQUENCE "tbl_objects_id_seq" start 1 increment 1 maxvalue +> 9223372036854775807 minvalue 1 cache 1; +> +> CREATE TABLE "tbl_objects" ( +> "id" bigint DEFAULT nextval('"tbl_objects_id_seq"'::text) NOT NULL, +> "name" text DEFAULT '' NOT NULL, +> "description" text DEFAULT '' NOT NULL, +> "status" smallint DEFAULT '1' NOT NULL, +> "class" text +> ); +> +> CREATE TABLE "tbl_viewers" ( +> "exec" text DEFAULT '' NOT NULL ) +> INHERITS ("tbl_objects"); +> +> CREATE TABLE "tbl_documents" ( +> "filename" text DEFAULT '' NOT NULL ) +> INHERITS ("tbl_objects"); +> +> CREATE TABLE "tbl_massemails" ( +> "from" text DEFAULT '' NOT NULL, +> "subject" text DEFAULT '' NOT NULL, +> "message" text DEFAULT '' NOT NULL ) +> INHERITS ("tbl_objects"); +> +> CREATE TABLE "tbl_icons" ( +> "format_id" bigint DEFAULT '0' NOT NULL ) +> INHERITS ("tbl_documents"); +> +> CREATE TABLE "tbl_formats" ( +> "viewer_id" bigint DEFAULT '0' NOT NULL, +> "extension" text DEFAULT '' NOT NULL, +> "contenttype" text DEFAULT '' NOT NULL, +> "upload_class" text ) +> INHERITS ("tbl_objects"); +> +> CREATE UNIQUE INDEX tbl_objects_id_key ON tbl_objects USING btree (id); + +Hmm, I wonder whether you have a specific goal with or reason for +explicitly specifying NOT NULL and empty string ('') as default value +for all these text fields? If it's just because your frontend makes it +inconvenient for you to treat a NULL as empty string, you might want to +consider allowing NULLs and using the coalesce() function in your select +- this would incur a few CPU cycles per returned result row, but will +spare you a few bytes in storage - I think 4 or 8 per column - for each +NULL value. Whether this is worth it or not depends on the percentage of +empty/NULL values in your data though. + +> Thanks very much for taking the time to look into this with me. It has +> been most informative. + +You're welcome! + +Regards, +Andras + +From pgsql-performance-owner@postgresql.org Thu Jan 30 03:25:20 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 59404475E2B + for ; + Thu, 30 Jan 2003 03:25:18 -0500 (EST) +Received: from web13902.mail.yahoo.com (web13902.mail.yahoo.com + [216.136.175.28]) + by postgresql.org (Postfix) with SMTP id A74FC475C85 + for ; + Thu, 30 Jan 2003 03:25:17 -0500 (EST) +Message-ID: <20030130082518.8953.qmail@web13902.mail.yahoo.com> +Received: from [202.88.238.180] by web13902.mail.yahoo.com via HTTP; + Thu, 30 Jan 2003 00:25:18 PST +Date: Thu, 30 Jan 2003 00:25:18 -0800 (PST) +From: Anil Kumar +Subject: Strangae Query Plans +To: pgsql-performance@postgresql.org +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/386 +X-Sequence-Number: 1033 + + +Greetings to all, + +I have found strange query execution plans with the +same version of +PostgreSQL but on different types of server machines. +Here are the details +of the servers: + +Server 1: +Pentium III, 800 MHz, 64 MB of RAM +RedHat Linux 7.2, Postgres ver 7.1 + +Server 2: +Dual Pentium III, 1.3 GHz, 512 MB of RAM +RedHat Linux 7.3 (SMP kernel), Postgres ver 7.1 + +Here is the query I tried: +--- query --- +explain +select bill.customer_no, bill.bill_no, bill.bill_date + from bill, ( select customer_no, max( +bill_date) as bill_date from + bill group by customer_no) as t_bill where + bill.customer_no = t_bill.customer_no and + bill.bill_date = t_bill.bill_date order by +bill.customer_no; +--- query--- + + +Result on Server 1: +---result--- +NOTICE: QUERY PLAN: + +Merge Join (cost=2436.88..2571.99 rows=671 width=44) + -> Sort (cost=1178.15..1178.15 rows=8189 width=28) + -> Seq Scan on bill (cost=0.00..645.89 +rows=8189 width=28) + -> Sort (cost=1258.72..1258.72 rows=819 width=16) + -> Subquery Scan t_bill +(cost=1178.15..1219.10 rows=819 width=16) + -> Aggregate (cost=1178.15..1219.10 +rows=819 width=16) + -> Group (cost=1178.15..1198.63 +rows=8189 width=16) + -> Sort +(cost=1178.15..1178.15 rows=8189 width=16) + -> Seq Scan on bill +(cost=0.00..645.89 rows=8189 width=16) + +EXPLAIN +---result--- + +Result on Server 2: +---result--- +NOTICE: QUERY PLAN: + +Sort (cost=0.04..0.04 rows=1 width=44) + -> Nested Loop (cost=0.01..0.03 rows=1 width=44) + -> Seq Scan on bill (cost=0.00..0.00 rows=1 +width=28) + -> Subquery Scan t_bill (cost=0.01..0.02 +rows=1 width=16) + -> Aggregate (cost=0.01..0.02 rows=1 +width=16) + -> Group (cost=0.01..0.01 rows=1 +width=16) + -> Sort (cost=0.01..0.01 +rows=1 width=16) + -> Seq Scan on bill +(cost=0.00..0.00 rows=1 width=16) + +EXPLAIN +---result--- + + +Can someone help me to figure out why the query plans +come out differently +despite the fact that almost everything but the number +of CPUs are same in +both the machines? + +Also the dual processor machine is awfully slow when I +execute this query +and the postmaster hogs the CPU (99.9%) for several +minutes literally +leaving that server unusable. + +thank you very much + Anil + + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Thu Jan 30 04:09:01 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id F2C43475B33 + for ; + Thu, 30 Jan 2003 04:08:58 -0500 (EST) +Received: from web13906.mail.yahoo.com (web13906.mail.yahoo.com + [216.136.175.69]) + by postgresql.org (Postfix) with SMTP id 3BF2D475AAC + for ; + Thu, 30 Jan 2003 04:08:58 -0500 (EST) +Message-ID: <20030130090859.68342.qmail@web13906.mail.yahoo.com> +Received: from [202.88.238.180] by web13906.mail.yahoo.com via HTTP; + Thu, 30 Jan 2003 01:08:59 PST +Date: Thu, 30 Jan 2003 01:08:59 -0800 (PST) +From: Anil Kumar +Subject: Re: Strangae Query Plans +To: pgsql-performance@postgresql.org +In-Reply-To: <20030130082518.8953.qmail@web13902.mail.yahoo.com> +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/387 +X-Sequence-Number: 1034 + +Hi, + +I got this solved. We ran "vacuum" with the --analyze flag on the +second server. And now the query plan is same as the first one and +it returns in a fraction of a second! + + Anil + +--- Anil Kumar wrote: +> +> Greetings to all, +> +> I have found strange query execution plans with the +> same version of +> PostgreSQL but on different types of server machines. +> Here are the details +> of the servers: +> +> Server 1: +> Pentium III, 800 MHz, 64 MB of RAM +> RedHat Linux 7.2, Postgres ver 7.1 +> +> Server 2: +> Dual Pentium III, 1.3 GHz, 512 MB of RAM +> RedHat Linux 7.3 (SMP kernel), Postgres ver 7.1 +> +> Here is the query I tried: +> --- query --- +> explain +> select bill.customer_no, bill.bill_no, bill.bill_date +> from bill, ( select customer_no, max( +> bill_date) as bill_date from +> bill group by customer_no) as t_bill where +> bill.customer_no = t_bill.customer_no and +> bill.bill_date = t_bill.bill_date order by +> bill.customer_no; +> --- query--- +> +> +> Result on Server 1: +> ---result--- +> NOTICE: QUERY PLAN: +> +> Merge Join (cost=2436.88..2571.99 rows=671 width=44) +> -> Sort (cost=1178.15..1178.15 rows=8189 width=28) +> -> Seq Scan on bill (cost=0.00..645.89 +> rows=8189 width=28) +> -> Sort (cost=1258.72..1258.72 rows=819 width=16) +> -> Subquery Scan t_bill +> (cost=1178.15..1219.10 rows=819 width=16) +> -> Aggregate (cost=1178.15..1219.10 +> rows=819 width=16) +> -> Group (cost=1178.15..1198.63 +> rows=8189 width=16) +> -> Sort +> (cost=1178.15..1178.15 rows=8189 width=16) +> -> Seq Scan on bill +> (cost=0.00..645.89 rows=8189 width=16) +> +> EXPLAIN +> ---result--- +> +> Result on Server 2: +> ---result--- +> NOTICE: QUERY PLAN: +> +> Sort (cost=0.04..0.04 rows=1 width=44) +> -> Nested Loop (cost=0.01..0.03 rows=1 width=44) +> -> Seq Scan on bill (cost=0.00..0.00 rows=1 +> width=28) +> -> Subquery Scan t_bill (cost=0.01..0.02 +> rows=1 width=16) +> -> Aggregate (cost=0.01..0.02 rows=1 +> width=16) +> -> Group (cost=0.01..0.01 rows=1 +> width=16) +> -> Sort (cost=0.01..0.01 +> rows=1 width=16) +> -> Seq Scan on bill +> (cost=0.00..0.00 rows=1 width=16) +> +> EXPLAIN +> ---result--- +> +> +> Can someone help me to figure out why the query plans +> come out differently +> despite the fact that almost everything but the number +> of CPUs are same in +> both the machines? +> +> Also the dual processor machine is awfully slow when I +> execute this query +> and the postmaster hogs the CPU (99.9%) for several +> minutes literally +> leaving that server unusable. +> +> thank you very much +> Anil +> +> +> __________________________________________________ +> Do you Yahoo!? +> Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +> http://mailplus.yahoo.com +> +> ---------------------------(end of +> broadcast)--------------------------- +> TIP 6: Have you searched our list archives? +> +> http://archives.postgresql.org + + +__________________________________________________ +Do you Yahoo!? +Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +http://mailplus.yahoo.com + +From pgsql-performance-owner@postgresql.org Thu Jan 30 05:43:08 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 585D4476361 + for ; + Thu, 30 Jan 2003 05:43:07 -0500 (EST) +Received: from rtlocal.trade-india.com (mail-relay.trade-india.com + [203.196.129.235]) + by postgresql.org (Postfix) with SMTP id 12EC44762C1 + for ; + Thu, 30 Jan 2003 05:43:02 -0500 (EST) +Received: (qmail 18046 invoked from network); 30 Jan 2003 10:39:15 -0000 +Received: from unknown (HELO system67.trade-india-local.com) (192.168.0.67) + by infocom-236-129-del.trade-india.com with SMTP; + 30 Jan 2003 10:39:15 -0000 +From: "Rajesh Kumar Mallah." +Organization: Infocom Network Limited. +To: Anil Kumar , + pgsql-performance@postgresql.org +Subject: Re: Strangae Query Plans +Date: Thu, 30 Jan 2003 16:18:11 +0530 +User-Agent: KMail/1.5 +References: <20030130090859.68342.qmail@web13906.mail.yahoo.com> +In-Reply-To: <20030130090859.68342.qmail@web13906.mail.yahoo.com> +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +Message-Id: <200301301618.11952.mallah@trade-india.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/388 +X-Sequence-Number: 1035 + + + +you could consider vacuuming thru a cron job daily.. +its good for db severs' health ;-) + + +On Thursday 30 January 2003 02:38 pm, Anil Kumar wrote: +> Hi, +> +> I got this solved. We ran "vacuum" with the --analyze flag on the +> second server. And now the query plan is same as the first one and +> it returns in a fraction of a second! +> +> Anil +> +> --- Anil Kumar wrote: +> > Greetings to all, +> > +> > I have found strange query execution plans with the +> > same version of +> > PostgreSQL but on different types of server machines. +> > Here are the details +> > of the servers: +> > +> > Server 1: +> > Pentium III, 800 MHz, 64 MB of RAM +> > RedHat Linux 7.2, Postgres ver 7.1 +> > +> > Server 2: +> > Dual Pentium III, 1.3 GHz, 512 MB of RAM +> > RedHat Linux 7.3 (SMP kernel), Postgres ver 7.1 +> > +> > Here is the query I tried: +> > --- query --- +> > explain +> > select bill.customer_no, bill.bill_no, bill.bill_date +> > from bill, ( select customer_no, max( +> > bill_date) as bill_date from +> > bill group by customer_no) as t_bill where +> > bill.customer_no = t_bill.customer_no and +> > bill.bill_date = t_bill.bill_date order by +> > bill.customer_no; +> > --- query--- +> > +> > +> > Result on Server 1: +> > ---result--- +> > NOTICE: QUERY PLAN: +> > +> > Merge Join (cost=2436.88..2571.99 rows=671 width=44) +> > -> Sort (cost=1178.15..1178.15 rows=8189 width=28) +> > -> Seq Scan on bill (cost=0.00..645.89 +> > rows=8189 width=28) +> > -> Sort (cost=1258.72..1258.72 rows=819 width=16) +> > -> Subquery Scan t_bill +> > (cost=1178.15..1219.10 rows=819 width=16) +> > -> Aggregate (cost=1178.15..1219.10 +> > rows=819 width=16) +> > -> Group (cost=1178.15..1198.63 +> > rows=8189 width=16) +> > -> Sort +> > (cost=1178.15..1178.15 rows=8189 width=16) +> > -> Seq Scan on bill +> > (cost=0.00..645.89 rows=8189 width=16) +> > +> > EXPLAIN +> > ---result--- +> > +> > Result on Server 2: +> > ---result--- +> > NOTICE: QUERY PLAN: +> > +> > Sort (cost=0.04..0.04 rows=1 width=44) +> > -> Nested Loop (cost=0.01..0.03 rows=1 width=44) +> > -> Seq Scan on bill (cost=0.00..0.00 rows=1 +> > width=28) +> > -> Subquery Scan t_bill (cost=0.01..0.02 +> > rows=1 width=16) +> > -> Aggregate (cost=0.01..0.02 rows=1 +> > width=16) +> > -> Group (cost=0.01..0.01 rows=1 +> > width=16) +> > -> Sort (cost=0.01..0.01 +> > rows=1 width=16) +> > -> Seq Scan on bill +> > (cost=0.00..0.00 rows=1 width=16) +> > +> > EXPLAIN +> > ---result--- +> > +> > +> > Can someone help me to figure out why the query plans +> > come out differently +> > despite the fact that almost everything but the number +> > of CPUs are same in +> > both the machines? +> > +> > Also the dual processor machine is awfully slow when I +> > execute this query +> > and the postmaster hogs the CPU (99.9%) for several +> > minutes literally +> > leaving that server unusable. +> > +> > thank you very much +> > Anil +> > +> > +> > __________________________________________________ +> > Do you Yahoo!? +> > Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +> > http://mailplus.yahoo.com +> > +> > ---------------------------(end of +> > broadcast)--------------------------- +> > TIP 6: Have you searched our list archives? +> > +> > http://archives.postgresql.org +> +> __________________________________________________ +> Do you Yahoo!? +> Yahoo! Mail Plus - Powerful. Affordable. Sign up now. +> http://mailplus.yahoo.com +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 4: Don't 'kill -9' the postmaster + +-- + + +-------------------------------------------- + Regds Mallah +Rajesh Kumar Mallah, +Project Manager (Development) +Infocom Network Limited, New Delhi +phone: +91(11)26152172 (221) (L) 9811255597 (M) +Visit http://www.trade-india.com , +India's Leading B2B eMarketplace. + + + +From pgsql-performance-owner@postgresql.org Thu Jan 30 12:34:50 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 411AC4775AE + for ; + Thu, 30 Jan 2003 12:34:50 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 619624773E7 + for ; + Thu, 30 Jan 2003 12:34:32 -0500 (EST) +Received: by allresearch.com (Postfix, from userid 8677) + id 75D383CD7A; Thu, 30 Jan 2003 12:34:37 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP id 4414C3CBE5 + for ; + Thu, 30 Jan 2003 12:34:36 -0500 (EST) +Date: Thu, 30 Jan 2003 12:34:36 -0500 +Subject: One large v. many small +From: Noah Silverman +To: pgsql-performance@postgresql.org +Message-Id: <1A107C56-3479-11D7-A3A3-000393AA8F3C@allresearch.com> +X-Mailer: Apple Mail (2.551) +X-Spam-Status: No, hits=-100.8 required=5.0 + tests=LINES_OF_YELLING,SPAM_PHRASE_00_01,USER_AGENT_APPLEMAIL, + USER_IN_WHITELIST version=2.43 +X-Spam-Level: +X-Sanitizer: Advosys mail filter +MIME-Version: 1.0 +Content-Type: text/plain; charset="US-ASCII"; format="flowed" +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/389 +X-Sequence-Number: 1036 + +As we continue our evaluation of Postgres, another interesting topic +has come up that I want to run by the group. + +In our current model, we have about 3,000 small tables that we use +track data for our clients. Each table is an identical structure, and +holds the data for one client. + +Another idea that we are considering is one big table instead of 3,000 +smaller ones. We could simply add a numeric field to indicate which +client a particular record was for. + +Each table has between 500 and 50,000 records, so the big table could +have up to 10 million rows if we combined everything. + + +A query on our current system is (for client #4) + +Select (*) from client_4 where foo=2; + +A query from the new, proposed system would be + +Select (*) from big_results where client=4 and foo=2. + +The big questions is, WHICH WILL BE FASTER with Postgres. Is there any +performance improvement or cost to switching to this new structure. + + +ANY AND ALL FEEDBACK/OPINIONS ARE WELCOME!! + +Thanks, + +Noah + + +From pgsql-performance-owner@postgresql.org Thu Jan 30 12:59:12 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D0444475FC8 + for ; + Thu, 30 Jan 2003 12:59:08 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 4A37F475EFD + for ; + Thu, 30 Jan 2003 12:59:07 -0500 (EST) +Received: from [63.195.55.98] (HELO spooky) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2753530; Thu, 30 Jan 2003 09:57:45 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Organization: Aglio Database Solutions +To: Noah Silverman , + pgsql-performance@postgresql.org +Subject: Re: One large v. many small +Date: Thu, 30 Jan 2003 09:56:56 -0800 +User-Agent: KMail/1.4.3 +References: <1A107C56-3479-11D7-A3A3-000393AA8F3C@allresearch.com> +In-Reply-To: <1A107C56-3479-11D7-A3A3-000393AA8F3C@allresearch.com> +MIME-Version: 1.0 +Content-Transfer-Encoding: 8bit +Message-Id: <200301300956.56041.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/390 +X-Sequence-Number: 1037 + +Noah, + +> As we continue our evaluation of Postgres, another interesting topic +> has come up that I want to run by the group. +> +> In our current model, we have about 3,000 small tables that we use +> track data for our clients. Each table is an identical structure, and +> holds the data for one client. + +I'd list what's wrong with this structure, but frankly it would take me long +enough that I'd need a consulting fee. Suffice it to say that the above is +a very, very bad (or at least antiquated) design idea and you need to +transition out of it as soon as possible. + +> Another idea that we are considering is one big table instead of 3,000 +> smaller ones. We could simply add a numeric field to indicate which +> client a particular record was for. + +Yes. Absolutely. Although I'd suggest an Integer field. + +> Each table has between 500 and 50,000 records, so the big table could +> have up to 10 million rows if we combined everything. + +Sure. + +> A query on our current system is (for client #4) +> +> Select (*) from client_4 where foo=2; +> +> A query from the new, proposed system would be +> +> Select (*) from big_results where client=4 and foo=2. +> +> The big questions is, WHICH WILL BE FASTER with Postgres. Is there any +> performance improvement or cost to switching to this new structure. + +Oh, no question query 1 will be faster ... FOR THAT QUERY. You are asking the +wrong question. + +However, explain to me how, under the current system, you can find the client +who ordered $3000 worth of widgets on January 12th if you don't already know +who it is? I'm not sure a 3000-table UNION query is even *possible*. + +Or how about giving me the average number of customer transactions in a month, +across all clients? + + + +You've enslaved your application design to performance considerations ... an +approach which was valid in 1990, because processing power was so limited +then. But now that dual-processor servers with RAID can be had for less than +$3000, there's simply no excuse for violating the principles of good +relational database design just to speed up a query. Buying more RAM is +much cheaper than having an engineer spend 3 weeks fixing data integrity +problems. + +The proper way to go about application design is to build your application on +paper or in a modelling program according to the best principles of software +design available, and *then* to discuss performance issues -- addressing them +*first* by buying hardware, and only compromising your applcation design when +no other alternative is available. + + + +I strongly suggest that you purchase Pascal's "Practical Issues in Database +Design" and give it a read. + +-- +Josh Berkus +Aglio Database Solutions +San Francisco + +From pgsql-performance-owner@postgresql.org Thu Jan 30 13:02:44 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 406654772FF + for ; + Thu, 30 Jan 2003 13:02:44 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 8D3254770B4 + for ; + Thu, 30 Jan 2003 13:02:40 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18eJ1M-0003CI-00 + for ; Thu, 30 Jan 2003 13:02:40 -0500 +Date: Thu, 30 Jan 2003 13:02:40 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: One large v. many small +Message-ID: <20030130130240.I983@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <1A107C56-3479-11D7-A3A3-000393AA8F3C@allresearch.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <1A107C56-3479-11D7-A3A3-000393AA8F3C@allresearch.com>; + from noah@allresearch.com on Thu, Jan 30, 2003 at 12:34:36PM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/391 +X-Sequence-Number: 1038 + +On Thu, Jan 30, 2003 at 12:34:36PM -0500, Noah Silverman wrote: +> Select (*) from client_4 where foo=2; +> +> A query from the new, proposed system would be +> +> Select (*) from big_results where client=4 and foo=2. +> +> The big questions is, WHICH WILL BE FASTER with Postgres. Is there any +> performance improvement or cost to switching to this new structure. + +Faster overall, or faster for that operation? I can't prove it, but +I suspect that the first one will return faster just because both the +index and the table itself is smaller. + +The possibility is thatit will cause you problems overall, however, +because of the large number of files you have to keep if you use 3000 +tables. This is dependent on your filesytem (and its +implementation). + +Note, too, that a lot of transactions frequently updating the table +might make a difference. A large number of dead tuples sitting on a +10 million row table will make anything crawl. + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Thu Jan 30 13:24:41 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 64190475CB4 + for ; + Thu, 30 Jan 2003 13:24:40 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id E4AE2475BD7 + for ; + Thu, 30 Jan 2003 13:24:39 -0500 (EST) +Received: by allresearch.com (Postfix, from userid 8677) + id A74E43CEF2; Thu, 30 Jan 2003 13:24:39 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP id 7071F3C258 + for ; + Thu, 30 Jan 2003 13:24:38 -0500 (EST) +Date: Thu, 30 Jan 2003 13:24:38 -0500 +Subject: Re: One large v. many small +Cc: pgsql-performance@postgresql.org +To: pgsql-performance@postgresql.org +From: Noah Silverman +In-Reply-To: <20030130130240.I983@mail.libertyrms.com> +Message-Id: <176C96F6-3480-11D7-A3A3-000393AA8F3C@allresearch.com> +X-Mailer: Apple Mail (2.551) +X-Spam-Status: No, hits=-102.1 required=5.0 + tests=IN_REP_TO,SPAM_PHRASE_01_02,USER_AGENT_APPLEMAIL, + USER_IN_WHITELIST version=2.43 +X-Spam-Level: +X-Sanitizer: Advosys mail filter +MIME-Version: 1.0 +Content-Type: text/plain; charset="US-ASCII"; format="flowed" +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/392 +X-Sequence-Number: 1039 + +OK, + +Thanks for the quick responses. + +A bit more information. + +We are in the business of gathering data for our clients. (We're a news +service). Subsequently, we do a lot of inserting and very rarely do +any deleting. (We periodically clear out results that are over 6 months +old.) + +On a give day, we will insert around 100,000 records in total. +(Currently split across all the client tables). + +A challenging part of the process is that we have to keep track of +previous content that may be similar. We CAN'T do this with a unique +index (don't ask, it would take too long to explain, but trust me, it +isn't possible). So, we have to query the table first and then compare +the results of that query to what we are inserting. SO, we probably do +close to 1 million queries, but then only make about 100,000 inserts. +The basic flow is 1) our system finds something it likes, 2) query the +table to see if something similar already exists, 3) if nothing similar +exists, insert. + +While all this is going on, our clients are accessing our online +reporting system. This system makes a variety of count and record +requests from the database. + +As I mentioned in our earlier post, we are attempting to decide if +Postgres will run faster/better/ with one big table, or a bunch of +smaller ones. It really doesn't make much difference to us, we just +want whatever structure will be faster. + +Thanks, + +-N + + +From pgsql-performance-owner@postgresql.org Thu Jan 30 14:13:40 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B203747752D + for ; + Thu, 30 Jan 2003 14:13:39 -0500 (EST) +Received: from jefftrout.com (h00a0cc4084e5.ne.client2.attbi.com + [24.128.215.169]) + by postgresql.org (Postfix) with SMTP id 6F1F54770CB + for ; + Thu, 30 Jan 2003 14:13:33 -0500 (EST) +Received: (qmail 40651 invoked from network); 30 Jan 2003 19:13:38 -0000 +Received: from unknown (HELO torgo) (threshar@10.10.10.10) + by 10.10.10.10 with SMTP; 30 Jan 2003 19:13:38 -0000 +Date: Thu, 30 Jan 2003 14:13:38 -0500 (EST) +From: Jeff +To: Josh Berkus +Cc: Noah Silverman , + "pgsql-performance@postgresql.org" +Subject: Re: One large v. many small +In-Reply-To: <200301300956.56041.josh@agliodbs.com> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/393 +X-Sequence-Number: 1040 + +On Thu, 30 Jan 2003, Josh Berkus wrote: + +> +> The proper way to go about application design is to build your application on +> paper or in a modelling program according to the best principles of software +> design available, and *then* to discuss performance issues -- addressing them +> *first* by buying hardware, and only compromising your applcation design when +> no other alternative is available. +> + +App design & performance go hand-in-hand. the trick is to balance them. +Who wants a _wonderful_ design that runs like a piece of poo? in this +case I agree with you - not the best design around. buying hardware to +fix speed problems is useful, but the software side should not be +neglected - imagine this scenario using your +methods (with a wonderful pg performance problem in hand (unless you are +running cvs)) + +User has a schema and writes a query along the lines of + +select somevalue from sometable where othervalue not in (select badvalues +from badvaluetable where id = 12345) + +we all know this runs horrifically on postgres. using your method I should +go out, spend thousands on multi-processor boxes, raid, ram + +If you do a little app tuning (maybe spend 10-30 minutes readig pgsql +archives) you'll learn to rewrite it as an exists query and make it faster +than it ever could have been on the fast hardware. I just saved the +company $10k too! (depends on if you consider that change a design +change).. some designs are fatally flawed from the start. but hey.. oh +well. + +'tis a fine line though.. balancing hardware vs software optimization. +(I'm also guessing they are not constrained by things such as an embedded +system too) + + +------------------------------------------------------------------------------ +Jeff Trout http://www.jefftrout.com/ + Ronald McDonald, with the help of cheese soup, + controls America from a secret volkswagon hidden in the past +------------------------------------------------------------------------------- + + + +From pgsql-performance-owner@postgresql.org Thu Jan 30 14:14:05 2003 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 14708475FD9 + for ; + Thu, 30 Jan 2003 14:14:05 -0500 (EST) +Received: from localhost.localdomain (unknown [65.217.53.66]) + by postgresql.org (Postfix) with ESMTP id 2D362475F1C + for ; + Thu, 30 Jan 2003 14:14:04 -0500 (EST) +Received: from thorn.mmrd.com (thorn.mmrd.com [172.25.10.100]) + by localhost.localdomain (8.12.5/8.12.5) with ESMTP id h0UJaH6P020140; + Thu, 30 Jan 2003 14:36:17 -0500 +Received: from gnvex001.mmrd.com (gnvex001.mmrd.com [192.168.3.55]) + by thorn.mmrd.com (8.11.6/8.11.6) with ESMTP id h0UJE1j28863; + Thu, 30 Jan 2003 14:14:02 -0500 +Received: from camel.mmrd.com ([172.25.5.213]) by gnvex001.mmrd.com with SMTP + (Microsoft Exchange Internet Mail Service Version 5.5.2653.13) + id CWVLCV3C; Thu, 30 Jan 2003 14:14:01 -0500 +Subject: Re: One large v. many small +From: Robert Treat +To: Noah Silverman +Cc: pgsql-performance@postgresql.org +In-Reply-To: <176C96F6-3480-11D7-A3A3-000393AA8F3C@allresearch.com> +References: <176C96F6-3480-11D7-A3A3-000393AA8F3C@allresearch.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +X-Mailer: Ximian Evolution 1.0.8 +Date: 30 Jan 2003 14:14:01 -0500 +Message-Id: <1043954041.2644.59.camel@camel> +Mime-Version: 1.0 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/394 +X-Sequence-Number: 1041 + +I'm going to go against the grain here and say that if you already have +all of the code and schema worked out, you probably should stick with +the many table design. While there are many reasons you'd be better off +with the one big table design, a speed increase really isn't one of +them. If you we're starting from scratch, or even had a slew of +development work you we're planning to do, I'd probably recommend the +one big table approach, but if you don't have any bottlenecks in your +current system and the type of query you've given is typical of the +majority of what your application is doing, there's no sense redesigning +your application in the middle of a database switch. + +Robert Treat + +PS. Josh, are you referring to Pascal's "Practical Issues In Database +Management" book or does he have a different book out that I'm not aware +of? + +On Thu, 2003-01-30 at 13:24, Noah Silverman wrote: +> OK, +> +> Thanks for the quick responses. +> +> A bit more information. +> +> We are in the business of gathering data for our clients. (We're a news +> service). Subsequently, we do a lot of inserting and very rarely do +> any deleting. (We periodically clear out results that are over 6 months +> old.) +> +> On a give day, we will insert around 100,000 records in total. +> (Currently split across all the client tables). +> +> A challenging part of the process is that we have to keep track of +> previous content that may be similar. We CAN'T do this with a unique +> index (don't ask, it would take too long to explain, but trust me, it +> isn't possible). So, we have to query the table first and then compare +> the results of that query to what we are inserting. SO, we probably do +> close to 1 million queries, but then only make about 100,000 inserts. +> The basic flow is 1) our system finds something it likes, 2) query the +> table to see if something similar already exists, 3) if nothing similar +> exists, insert. +> +> While all this is going on, our clients are accessing our online +> reporting system. This system makes a variety of count and record +> requests from the database. +> +> As I mentioned in our earlier post, we are attempting to decide if +> Postgres will run faster/better/ with one big table, or a bunch of +> smaller ones. It really doesn't make much difference to us, we just +> want whatever structure will be faster. +> +> Thanks, +> +> -N +> + + + +From pgsql-performance-owner@postgresql.org Thu Jan 30 17:27:49 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4D90E476102 + for ; + Thu, 30 Jan 2003 17:27:46 -0500 (EST) +Received: from utahisp.com (cyber-wire.com [66.239.12.3]) + by postgresql.org (Postfix) with ESMTP id 3DDF74775F9 + for ; + Thu, 30 Jan 2003 17:27:41 -0500 (EST) +Received: from chad [63.230.8.76] by utahisp.com + (SMTPD32-7.13) id A0BB8914024A; Thu, 30 Jan 2003 12:44:59 -0700 +Message-ID: <011301c2c897$d22719f0$32021aac@chad> +From: "Chad Thompson" +To: "Noah Silverman" , + "pgsql-performance" +References: <176C96F6-3480-11D7-A3A3-000393AA8F3C@allresearch.com> +Subject: Re: One large v. many small +Date: Thu, 30 Jan 2003 12:43:09 -0700 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 6.00.2720.3000 +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 +X-Declude-Sender: chad@weblinkservices.com [63.230.8.76] +X-Note: This E-mail was scanned by Declude JunkMail (www.declude.com) for + spam. +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/395 +X-Sequence-Number: 1042 + +I have a database running on PostgresSQL w/ close to 7 million records in +one table and ~ 3 million in another, along w/ various smaller supportive +tables. +Before I started here everything was run out of small tables, one for each +client, similar ( i think ) to what you are doing now. +We submit ~ 50 - 100K records each week. And before we moved to one table, +our company had no idea of how it was doing on a daily, weekly or monthly +basis. Now that we have moved to one large structure, new ideas about +reporting funtions and added services we can give to our clients are poping +up all the time. + +There are MANY benifts to following Josh's advice and putting all your +information in one table. Others than those given, what if you wanted to +give an added service to your clients where they are made aware of similar +postings by your other clients. Running this kind of report would be a +nightmare in your current situation. + +As far as performance goes, I am able to join these 2 tables along w/ others +and get the information, counts etc., that I need, using some rather +complicated queries, in about 2-3 seconds per query. While this may sound +awful realize that Im running on a standard workstation PIII 700, and for +the money, Its a dream! + +More importantly you need to realize, as my coworkers have now done, that +anything that you can do w/ a small table, you can do w/ one big table and +an extra line in the where clause (eg. Where client_id = 'blah' ). +PostgresSQL has wonderful support and many excellent DBA's that if you post +a SQL problem they are very supportive in helping solve the problem. + +I hope this helps make your decision. +Thanks +Chad + + +----- Original Message ----- +From: "Noah Silverman" +To: +Cc: +Sent: Thursday, January 30, 2003 11:24 AM +Subject: Re: [PERFORM] One large v. many small + + +> OK, +> +> Thanks for the quick responses. +> +> A bit more information. +> +> We are in the business of gathering data for our clients. (We're a news +> service). Subsequently, we do a lot of inserting and very rarely do +> any deleting. (We periodically clear out results that are over 6 months +> old.) +> +> On a give day, we will insert around 100,000 records in total. +> (Currently split across all the client tables). +> +> A challenging part of the process is that we have to keep track of +> previous content that may be similar. We CAN'T do this with a unique +> index (don't ask, it would take too long to explain, but trust me, it +> isn't possible). So, we have to query the table first and then compare +> the results of that query to what we are inserting. SO, we probably do +> close to 1 million queries, but then only make about 100,000 inserts. +> The basic flow is 1) our system finds something it likes, 2) query the +> table to see if something similar already exists, 3) if nothing similar +> exists, insert. +> +> While all this is going on, our clients are accessing our online +> reporting system. This system makes a variety of count and record +> requests from the database. +> +> As I mentioned in our earlier post, we are attempting to decide if +> Postgres will run faster/better/ with one big table, or a bunch of +> smaller ones. It really doesn't make much difference to us, we just +> want whatever structure will be faster. +> +> Thanks, +> +> -N +> +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org +> + + +From pgsql-general-owner@postgresql.org Thu Jan 30 17:24:57 2003 +X-Original-To: pgsql-general@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4A20F475A5C + for ; + Thu, 30 Jan 2003 17:24:56 -0500 (EST) +Received: from mail.com-stock.com (mail.com-stock.com [204.255.137.254]) + by postgresql.org (Postfix) with ESMTP id E98074762AF + for ; + Thu, 30 Jan 2003 14:42:01 -0500 (EST) +Received: by mail.com-stock.com (Postfix, from userid 1000) + id B896B110; Thu, 30 Jan 2003 14:42:01 -0500 (EST) +Received: from deimos (deimos.com-stock.com [204.255.137.120]) + by mail.com-stock.com (Postfix) with SMTP + id 7122ADA0B; Thu, 30 Jan 2003 14:41:59 -0500 (EST) +Message-ID: <016b01c2c898$891d05c0$7889ffcc@comstock.com> +From: "Gregory Wood" +To: "Jeff" +Cc: "PostgreSQL-General" +References: +Subject: Re: [PERFORM] One large v. many small +Date: Thu, 30 Jan 2003 14:48:16 -0500 +Organization: Comstock Net Services +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 6.00.2800.1106 +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/1535 +X-Sequence-Number: 36656 + +> imagine this scenario using your +> methods (with a wonderful pg performance problem in hand (unless you are +> running cvs)) + + + +> If you do a little app tuning (maybe spend 10-30 minutes readig pgsql +> archives) you'll learn to rewrite it as an exists query and make it faster +> than it ever could have been on the fast hardware. + +Your example is invalid... you're talking about an implementation detail, +not an architectural design issue. + +I have to agree with the original point... normalize the database into the +proper form, then denormalize as necessary to make things perform +acceptably. In other words, do things the right way and then muck it up if +you have to. + +While you make an excellent point (i.e. you can't always through hardware, +especially excessive hardware at the problem), I would err on the side of +doing things the right way. It usually ends up making the software easier to +maintain and add to. A poor design to save a few thousand dollars on +hardware now can cost many tens of thousands (or more) dollars on +programming time down the road. + +I've seen entirely too many cases where people started thinking about +performance before they considered overall design. It almost always ends in +disaster (especially since hardware only gets faster over time and software +only gets more complex). + +Greg + + +From pgsql-performance-owner@postgresql.org Thu Jan 30 18:18:57 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 730B847747C + for ; + Thu, 30 Jan 2003 18:18:56 -0500 (EST) +Received: from bob.samurai.com (bob.samurai.com [205.207.28.75]) + by postgresql.org (Postfix) with ESMTP id 02490475E45 + for ; + Thu, 30 Jan 2003 18:18:56 -0500 (EST) +Received: from DU150.N224.ResNet.QueensU.CA (DU150.N224.ResNet.QueensU.CA + [130.15.224.150]) by bob.samurai.com (Postfix) with ESMTP + id 66E1A1F68; Thu, 30 Jan 2003 18:18:57 -0500 (EST) +Subject: Re: Postgres 7.3.1 poor insert/update/search performance +From: Neil Conway +To: Andrew Sullivan +Cc: pgsql-performance@postgresql.org +In-Reply-To: <20030122070524.F27014@mail.libertyrms.com> +References: <13165.1043188295@sss.pgh.pa.us> + <1CE2D1AE-2DAB-11D7-BE6C-000393D9FD00@mobygames.com> + <20030122070524.F27014@mail.libertyrms.com> +Content-Type: text/plain +Organization: +Message-Id: <1043968734.3123.27.camel@tokyo> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 30 Jan 2003 18:18:54 -0500 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/396 +X-Sequence-Number: 1043 + +On Wed, 2003-01-22 at 07:05, Andrew Sullivan wrote: +> (As you point out, this caclulation is complicated by the potential to +> waste memory by caching the data twice + +If we had a good buffer replacement algorithm (which we currently do +not), ISTM that hot pages retained in PostgreSQL's buffer cache would +never get loaded from the OS's IO cache, thus causing those pages to +eventually be evicted from the OS's cache. So the "cache the data twice" +problem doesn't apply in all circumstances. + +> Some systems, like Solaris, allow you to turn off the +> disk cache, so the problem may not be one you face.) + +I think it would be interesting to investigate disabling the OS' cache +for all relation I/O (i.e. heap files, index files). That way we could +both improve performance (by moving all the caching into PostgreSQL's +domain, where there is more room for optimization), as well as make +configuration simpler: in an ideal world, it would remove the need to +consider the OS' caching when configuring the amount of shared memory to +allocate to PostgreSQL. + +Can this be done using O_DIRECT? If so, is it portable? + +BTW, if anyone has any information on actually *using* O_DIRECT, I'd be +interested in it. I tried to quickly hack PostgreSQL to use it, without +success... + +Cheers, + +Neil +-- +Neil Conway || PGP Key ID: DB3C29FC + + + + +From pgsql-performance-owner@postgresql.org Thu Jan 30 23:57:11 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 77A224765C6 + for ; + Thu, 30 Jan 2003 23:30:07 -0500 (EST) +Received: from platonic.cynic.net (platonic.cynic.net [204.80.150.245]) + by postgresql.org (Postfix) with ESMTP id A0FDB4765C2 + for ; + Thu, 30 Jan 2003 23:30:06 -0500 (EST) +Received: from angelic.cynic.net (angelic-platonic.cvpn.cynic.net + [198.73.220.226]) by platonic.cynic.net (Postfix) with ESMTP + id 0E628C006; Fri, 31 Jan 2003 03:54:27 +0000 (UTC) +Received: from localhost (localhost [127.0.0.1]) + by angelic.cynic.net (Postfix) with ESMTP + id 4F3DF8736; Fri, 31 Jan 2003 12:54:26 +0900 (JST) +Date: Fri, 31 Jan 2003 12:54:26 +0900 (JST) +From: Curt Sampson +To: Josh Berkus +Cc: Noah Silverman , + pgsql-performance@postgresql.org +Subject: Re: One large v. many small +In-Reply-To: <200301300956.56041.josh@agliodbs.com> +Message-ID: +References: <1A107C56-3479-11D7-A3A3-000393AA8F3C@allresearch.com> + <200301300956.56041.josh@agliodbs.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/398 +X-Sequence-Number: 1045 + +On Thu, 30 Jan 2003, Josh Berkus wrote: + +> > Another idea that we are considering is one big table instead of 3,000 +> > smaller ones. We could simply add a numeric field to indicate which +> > client a particular record was for. +> +> Yes. Absolutely. Although I'd suggest an Integer field. + + From the description given in Noah's message, and also the one given in +his later message, I have little doubt that 3000 small tables are going +to be significantly faster than one large table. If you don't believe +me, work out just where the disk blocks are going to end up, and how +many blocks are going to have to be fetched for his typical query in +a semi-clustered or non-clustered table. (If postgres had clustered +indexes a la MS SQL server, where the rows are physically stored in the +order of the clustered index, it would be a different matter.) + +> However, explain to me how, under the current system, you can find the client +> who ordered $3000 worth of widgets on January 12th if you don't already know +> who it is? + +Explain to me why he has to do this. + +It's all very nice to have a general system that can do well on all +sorts of queries, but if you lose time on the queries you do do, in +order to save time on queries you don't do, you're definitely not +getting the best performance out of the system. + +> I'm not sure a 3000-table UNION query is even *possible*. + +This is not the only solution, either. You could simply just do 3000 +queries. If this is something you execute only once a month, the making +that query three or four orders of magnitude more expensive might be a +small price to pay for making cheaper the queries you run several times +per second. + +> +> +> You've enslaved your application design to performance considerations ... an +> approach which was valid in 1990, because processing power was so limited +> then. But now that dual-processor servers with RAID can be had for less than +> $3000, there's simply no excuse for violating the principles of good +> relational database design just to speed up a query. Buying more RAM is +> much cheaper than having an engineer spend 3 weeks fixing data integrity +> problems. + +*Sigh.* Ok, my turn to rant. + +RAM is not cheap enough yet for me to buy several hundred gigabytes of +it for typical applications, even if I could find a server that I could +put it in. Disk performance is not growing the way CPU performance is. +And three weeks of engineering time plus a ten thousand dollar server +is, even at my top billing rate, still a heck of a lot cheaper than a +quarter-million dollar server. + +Applying your strategy to all situations is not always going to produce +the most cost-effective solution. And for most businesses, that's what it's +all about. They're not interested in the more "thoretically pure" way of +doing things except insofar as it makes them money. + +As for the data integrity problems, I don't know where that came from. I +think that was made up out of whole cloth, because it didn't seem to me +that the original question involved any. + +cjs +-- +Curt Sampson +81 90 7737 2974 http://www.netbsd.org + Don't you know, in this new Dark Age, we're all light. --XTC + +From pgsql-performance-owner@postgresql.org Thu Jan 30 23:04:10 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6599F476829 + for ; + Thu, 30 Jan 2003 23:04:04 -0500 (EST) +Received: from platonic.cynic.net (platonic.cynic.net [204.80.150.245]) + by postgresql.org (Postfix) with ESMTP id AE90B476759 + for ; + Thu, 30 Jan 2003 23:04:03 -0500 (EST) +Received: from angelic.cynic.net (angelic-platonic.cvpn.cynic.net + [198.73.220.226]) by platonic.cynic.net (Postfix) with ESMTP + id DB54BC009; Fri, 31 Jan 2003 04:02:54 +0000 (UTC) +Received: from localhost (localhost [127.0.0.1]) + by angelic.cynic.net (Postfix) with ESMTP + id 7C4698736; Fri, 31 Jan 2003 13:02:52 +0900 (JST) +Date: Fri, 31 Jan 2003 13:02:52 +0900 (JST) +From: Curt Sampson +To: Neil Conway +Cc: Andrew Sullivan , pgsql-performance@postgresql.org +Subject: Re: Postgres 7.3.1 poor insert/update/search performance +In-Reply-To: <1043968734.3123.27.camel@tokyo> +Message-ID: +References: <13165.1043188295@sss.pgh.pa.us> + <1CE2D1AE-2DAB-11D7-BE6C-000393D9FD00@mobygames.com> + <20030122070524.F27014@mail.libertyrms.com> + <1043968734.3123.27.camel@tokyo> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/397 +X-Sequence-Number: 1044 + +On Fri, 30 Jan 2003, Neil Conway wrote: + +> If we had a good buffer replacement algorithm (which we currently do +> not), ISTM that hot pages retained in PostgreSQL's buffer cache would +> never get loaded from the OS's IO cache, thus causing those pages to +> eventually be evicted from the OS's cache. So the "cache the data twice" +> problem doesn't apply in all circumstances. + +No, but it does apply to every block at some point, since during the +initial load it's present in both caches, and it has to be flushed from +the OS's cache at some point. + +> > Some systems, like Solaris, allow you to turn off the +> > disk cache, so the problem may not be one you face.) +> +> I think it would be interesting to investigate disabling the OS' cache +> for all relation I/O (i.e. heap files, index files). That way we could +> both improve performance (by moving all the caching into PostgreSQL's +> domain, where there is more room for optimization)... + +I'm not so sure that there is that all much more room for optimization. +But take a look at what Solaris and FFS do now, and consider how much +work it would be to rewrite it, and then see if you even want to do that +before adding stuff to improve performance. + +> , as well as make configuration simpler: in an ideal world, it would +> remove the need to consider the OS' caching when configuring the +> amount of shared memory to allocate to PostgreSQL. + +We could do that much more simply by using mmap. + +> Can this be done using O_DIRECT? + +It can, but you're doing to lose some of the advantages that you'd get +from using raw devices instead. In particular, you have no way to know +the physical location of blocks on the disk, because those locations are +often different from the location in the file. + +> If so, is it portable? + +O_DIRECT is not all that portable, I don't think. Certainly not as +portable as mmap. + +cjs +-- +Curt Sampson +81 90 7737 2974 http://www.netbsd.org + Don't you know, in this new Dark Age, we're all light. --XTC + +From pgsql-performance-owner@postgresql.org Fri Jan 31 01:03:28 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 24A88476599 + for ; + Fri, 31 Jan 2003 01:03:26 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP + id 6E3FA4761F6; Fri, 31 Jan 2003 01:03:24 -0500 (EST) +Received: by davinci.ethosmedia.com (CommuniGate Pro PIPE 4.0.2) + with PIPE id 2807722; Thu, 30 Jan 2003 21:57:49 -0800 +X-Spam-Status: Scanner Called +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2807562; Thu, 30 Jan 2003 21:55:40 -0800 +From: "Josh Berkus" +Subject: Re: One large v. many small +To: Josh Berkus +Cc: Noah Silverman , + pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Thu, 30 Jan 2003 21:55:40 -0800 +Message-ID: +In-Reply-To: +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +X-Spam-Status: No, hits=1.4 required=6.5 + tests=FROM_AND_TO_SAME_6,IN_REP_TO,SPAM_PHRASE_00_01 + version=2.43 +X-Spam-Level: . +Content-Transfer-Encoding: quoted-printable +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/399 +X-Sequence-Number: 1046 + +Noah, + +Well, there you have it: a unanimous consensus of opinion. You +should either combine all of your tables or not. But definitely one or +the other. + + + +Hope you feel informed now. + +-Josh + +From pgsql-performance-owner@postgresql.org Fri Jan 31 01:28:43 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 09E364761F6 + for ; + Fri, 31 Jan 2003 01:28:42 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 3E50D475C2B + for ; + Fri, 31 Jan 2003 01:28:37 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id h0V6RHK27150 + for ; Fri, 31 Jan 2003 11:57:17 +0530 +Received: from daithan.intranet.pspl.co.in (daithan.intranet.pspl.co.in + [192.168.7.161]) + by www.pspl.co.in (8.11.6/8.11.0) with ESMTP id h0V6RH527145 + for ; Fri, 31 Jan 2003 11:57:17 +0530 +Content-Type: text/plain; + charset="iso-8859-1" +From: "Shridhar Daithankar" + +To: pgsql-performance@postgresql.org +Subject: Re: One large v. many small +Date: Fri, 31 Jan 2003 11:57:40 +0530 +User-Agent: KMail/1.4.3 +References: <176C96F6-3480-11D7-A3A3-000393AA8F3C@allresearch.com> +In-Reply-To: <176C96F6-3480-11D7-A3A3-000393AA8F3C@allresearch.com> +MIME-Version: 1.0 +Message-Id: <200301311157.40351.shridhar_daithankar@persistent.co.in> +X-MIME-Autoconverted: from quoted-printable to 8bit by www.pspl.co.in id + h0V6RH527145 +Content-Transfer-Encoding: quoted-printable +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/400 +X-Sequence-Number: 1047 + +On Thursday 30 Jan 2003 11:54 pm, you wrote: +> As I mentioned in our earlier post, we are attempting to decide if +> Postgres will run faster/better/ with one big table, or a bunch of +> smaller ones. It really doesn't make much difference to us, we just +> want whatever structure will be faster. + +I would say create a big table with client id. Create a index on it and cre= +ate=20 +3000 views. Of course you need to figure out SQL voodoo to insert into=20 +postgresql views using rules. + +But that would save you from modifying your app. up and down. But there is= +=20 +going to be massive framgmentation. Consider clustering tables once in a=20 +while. + + HTH + + Shridhar + +From pgsql-general-owner@postgresql.org Sun Feb 2 00:27:36 2003 +X-Original-To: pgsql-general@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 550844760F0 + for ; + Fri, 31 Jan 2003 08:03:17 -0500 (EST) +Received: from jefftrout.com (h00a0cc4084e5.ne.client2.attbi.com + [24.128.215.169]) + by postgresql.org (Postfix) with SMTP id A4D4D475FB5 + for ; + Fri, 31 Jan 2003 08:03:16 -0500 (EST) +Received: (qmail 45821 invoked from network); 31 Jan 2003 13:01:24 -0000 +Received: from unknown (HELO torgo) (threshar@10.10.10.10) + by 10.10.10.10 with SMTP; 31 Jan 2003 13:01:24 -0000 +Date: Fri, 31 Jan 2003 08:01:24 -0500 (EST) +From: Jeff +To: Gregory Wood +Cc: PostgreSQL-General +Subject: Re: [PERFORM] One large v. many small +In-Reply-To: <016b01c2c898$891d05c0$7889ffcc@comstock.com> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200302/28 +X-Sequence-Number: 36782 + +On Thu, 30 Jan 2003, Gregory Wood wrote: + +> While you make an excellent point (i.e. you can't always through hardware, +> especially excessive hardware at the problem), I would err on the side of +> doing things the right way. It usually ends up making the software easier to +> maintain and add to. A poor design to save a few thousand dollars on +> hardware now can cost many tens of thousands (or more) dollars on +> programming time down the road. +> + + +fun story - I was part of a dot com and we had an informix database and +the schema was pretty "good" - ref integrity and "logical layout". What +happened +was our traffic started increasng dramatically. We ended up having to +disable all the ref integrity simply because it gave us a 50% boost. It +was unfortuate, but you have to do it. Sometimes you have to comprimise. +As for throwing hardware at it - it was already running on a $500k sun +box, an upgrade would have likely gone into the 7 digit range. +Not to mention you don't exactly get a quick turnaround on +hardware of that type.. a u10 perhaps, but not a big beefy box. +(Eventually we did upgrade the db machine when we got another round of +funding) + +so after a week of engineering and futzing we had things under control.. +(db changes, massive app changes (agressive caching)) + +Yes it was horrid to throw out RI (which caused some minor issues +later) but when the business is riding on it.. you make it work any way +you can. In a perfect world I would have done it another way, but when +the site is down (read: your business is not running, you are losing large +amounts of money) you need to put on your fire fighter suit, not your lab +coat. + +I remember one time we were featured on CNBC and our traffic jumped by +1000% (yes, 1000) - our poor machines were hosed. Now we did throw +hardware at this problem (more frontends) however aquiring hardware in +time of crisis is not terribly easy (took 3 days in this case). So you +have to look at your other routes. + +sometimes your design or some implementation details will be comprimised.. +its a fact of business. If the best design always won then why don't I +have an alpha for my machine machine? they are the fastest, best cpu +around. (I'll admit, alpha failed a lot because of marketing +issues and cost) Business drives everything. I'd rather continue getting +a paycheck than having a wonderfully designed db that doesn't perform +well and is causing us to lose money. + +If you have the ability (ie, you know your site is going to end up doing +22M page views, or some other statistic like that) to see what things will +be like later and are not fighting a fire, design is wonderful. (Lets not +forget time. I was just on a major project and they scheduled _3_ weeks +of design & coding.. we were quite upset about that one.. and they +arranged it so the launch date was set in stone. man.. worked some +long nights..) + +getting back to the original posters thing - why not just try a test to +see how things perform yourself? Try some tests with 3000 tables, and try +a test with 1 table with a client_id (int) field. Or as said, you could even make a boatload of views and +change your insertion logic.. + +anyway, sorry if I flamed anybody or if they took it personally. +just stating some experiences I've had. + +------------------------------------------------------------------------------ +Jeff Trout http://www.jefftrout.com/ + Ronald McDonald, with the help of cheese soup, + controls America from a secret volkswagon hidden in the past +------------------------------------------------------------------------------- + + + +From pgsql-performance-owner@postgresql.org Fri Jan 31 13:24:33 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5A36C4760F5 + for ; + Fri, 31 Jan 2003 10:08:52 -0500 (EST) +Received: from curtislaptop (unknown [63.164.0.44]) + by postgresql.org (Postfix) with SMTP id 85F8C475C26 + for ; + Fri, 31 Jan 2003 10:08:51 -0500 (EST) +Received: from [127.0.0.1] by curtislaptop + (ArGoSoft Mail Server Freeware, Version 1.8 (1.8.1.7)); + Fri, 31 Jan 2003 10:32:15 -0400 +From: "Curtis Faith" +To: "'Curt Sampson'" , "'Josh Berkus'" , + "'Noah Silverman'" +Cc: +Subject: Re: One large v. many small +Date: Fri, 31 Jan 2003 10:32:11 -0400 +Message-ID: <001401c2c935$8c759140$a200a8c0@curtislaptop> +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 10.0.2627 +In-Reply-To: +Importance: Normal +X-MIMEOLE: Produced By Microsoft MimeOLE V5.00.2919.6700 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/402 +X-Sequence-Number: 1049 + +Curt Sampson wrote: +> >From the description given in Noah's message, and also the +> one given in his later message, I have little doubt that 3000 +> small tables are going to be significantly faster than one +> large table. If you don't believe me, work out just where the +> disk blocks are going to end up, and how many blocks are going +> to have to be fetched for his typical query in a semi-clustered or +> non-clustered table. + +You may be right, Curt, but I've seen unintuitive results for this +kind of thing in the past. + +Depending on the way the records are accessed and the cache size, +the exact opposite could be true. The index pages will most likely +rarely be in memory when you have 3000 different tables. Meaning +that each search will require at least three or four index page +retrievals plus the tuple page. + +So what you might lose due to lack of clustering will be made up +by the more efficient caching of the upper levels of the index +btree pages. + +Combine a multi-part index (on both client and foo, which order +would depend on the access required) that is clustered once a week +or so using the admittedly non-optimal PostgreSQL CLUSTER command +and I'll bet you can get equivalent or better performance with the +single table with the concomitant advantages of much better +reporting options. + +I've also seen many examples of linear algorithms in database +data dictionaries which would cause a 3000+ table database +to perform poorly during the parsing/query optimization stage. +I don't have any idea whether or not PostgreSQL suffers from this +problem. + +I don't think there is any substitute for just trying it out. It +shouldn't be that hard to create a bunch of SQL statements that +concatenate the tables into one large one. + +Try the most common queries against both scenarios. You might be +surprised. + +- Curtis + + + +From pgsql-general-owner@postgresql.org Fri Jan 31 13:08:59 2003 +X-Original-To: pgsql-general@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9D4F4475F73 + for ; + Fri, 31 Jan 2003 12:07:33 -0500 (EST) +Received: from mail.com-stock.com (mail.com-stock.com [204.255.137.254]) + by postgresql.org (Postfix) with ESMTP id 0313C475EE4 + for ; + Fri, 31 Jan 2003 12:07:32 -0500 (EST) +Received: by mail.com-stock.com (Postfix, from userid 1000) + id 57AAFAA; Fri, 31 Jan 2003 12:05:57 -0500 (EST) +Received: from eng3 (eng3.com-stock.com [204.255.137.79]) + by mail.com-stock.com (Postfix) with SMTP + id CA7CADA33; Fri, 31 Jan 2003 12:05:55 -0500 (EST) +Message-ID: <00be01c2c94b$e92f8150$4f89ffcc@eng3> +From: "Gregory Wood" +To: "Jeff" +Cc: "PostgreSQL-General" +References: +Subject: Re: [PERFORM] One large v. many small +Date: Fri, 31 Jan 2003 12:12:18 -0500 +Organization: Comstock Net Services +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 6.00.2800.1106 +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/1572 +X-Sequence-Number: 36693 + +> > While you make an excellent point (i.e. you can't always through +hardware, +> > especially excessive hardware at the problem), I would err on the side +of +> > doing things the right way. It usually ends up making the software +easier to +> > maintain and add to. A poor design to save a few thousand dollars on +> > hardware now can cost many tens of thousands (or more) dollars on +> > programming time down the road. +> > +> +> +> fun story - I was part of a dot com and we had an informix database and +> the schema was pretty "good" - ref integrity and "logical layout". What +> happened +> was our traffic started increasng dramatically. We ended up having to +> disable all the ref integrity simply because it gave us a 50% boost. It +> was unfortuate, but you have to do it. Sometimes you have to comprimise. + +You did what I was suggesting then... start with a good design and work your +way backwards for the performance you needed and not the other way around. +I've had to compromise all too often at my business (which upsets me more +because it's often cost the business more in terms of customers and revenue +in the long run, but they aren't my decisions to make), so I understand that +not everything is a matter of "do it right"... all too often it's a matter +of "get it done". + +> As for throwing hardware at it - it was already running on a $500k sun +> box, an upgrade would have likely gone into the 7 digit range. + +I don't envy you on that... as nice as it is to have that kind of a budget, +that adds a lot of pressure to "make it work". + +> Yes it was horrid to throw out RI (which caused some minor issues +> later) but when the business is riding on it.. you make it work any way +> you can. In a perfect world I would have done it another way, but when +> the site is down (read: your business is not running, you are losing large +> amounts of money) you need to put on your fire fighter suit, not your lab +> coat. + +Well said. + +> anyway, sorry if I flamed anybody or if they took it personally. +> just stating some experiences I've had. + +The more experiences shared, the more well rounded the conclusions of the +person reading them. + +Greg + + +From pgsql-performance-owner@postgresql.org Fri Jan 31 12:50:39 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D755C4760F5 + for ; + Fri, 31 Jan 2003 12:39:53 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 0F1A3475DC0 + for ; + Fri, 31 Jan 2003 12:39:52 -0500 (EST) +Received: from [63.195.55.98] (HELO spooky) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2814877 for pgsql-performance@postgresql.org; + Fri, 31 Jan 2003 09:35:29 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Organization: Aglio Database Solutions +To: pgsql-performance@postgresql.org +Subject: Re: One large v. many small +Date: Fri, 31 Jan 2003 09:34:28 -0800 +User-Agent: KMail/1.4.3 +References: +In-Reply-To: +MIME-Version: 1.0 +Message-Id: <200301310934.28980.josh@agliodbs.com> +Content-Transfer-Encoding: quoted-printable +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/401 +X-Sequence-Number: 1048 + +Folks, + +Many, many replies on this topic: + +Jeff: +> App design & performance go hand-in-hand. the trick is to balance them. +> Who wants a _wonderful_ design that runs like a piece of poo? in this + +>Select somevalue from sometable where othervalue not in (select badvalues +> from badvaluetable where id =3D 12345) +> we all know this runs horrifically on postgres. using your method I should +> go out, spend thousands on multi-processor boxes, raid, ram + +Sorry, no, Jeff. The above is what one calls a "bad query" and is not,=20 +therefore, a performance vs. design issue: that query is bad design-wise, a= +nd=20 +bad performance-wise. Perhpas another example of your argument? + +Since you do not seem to have understood my argument, it is this:=20=20 +Design changes, made for the sake of performance or rapid app building, whi= +ch=20 +completely violate good RDBMS design and normalization principles, almost= +=20 +always cost you more over the life of the application than you gain in=20 +performance in the short term.=20=20=20 + +Curt: +> It's all very nice to have a general system that can do well on all +> sorts of queries, but if you lose time on the queries you do do, in +> order to save time on queries you don't do, you're definitely not +> getting the best performance out of the system. + +This is a good point; I tend to build for posterity because, so far, 90% of= + my=20 +clients who started out having me build a "single-purpose" database ended u= +p=20 +expanding the application to cover 2-10 additional needs, thus forcing me t= +o=20 +clean up any design shortcuts I took with the original app. However, Noa= +h=20 +may have more control over his company than that. + + +> RAM is not cheap enough yet for me to buy several hundred gigabytes of +> it for typical applications, even if I could find a server that I could +> put it in. Disk performance is not growing the way CPU performance is. +> And three weeks of engineering time plus a ten thousand dollar server +> is, even at my top billing rate, still a heck of a lot cheaper than a +> quarter-million dollar server. + +I was thinking more of the difference between a $3000 server and a $9000=20 +server myself; unless you're doing nuclear test modelling, I don't see any= +=20 +need for a $250,000 server for anything.=20=20=20 +To give an extreme example, I have a client who purchased a $150,000=20 +accounting system that turned out to be badly designed, normalization-wise,= +=20 +partly because the accounting system engineers were focusing on 8-year-old= +=20 +technology with performance restrictions which were no longer really=20 +applicable (for example, they talked the client into buying a quad-processo= +r=20 +server and then wrote all of their middleware code on a platform that does= +=20 +not do SMP). Over the last two years, they have paid my company $175,000 t= +o=20=20 +"fix" this accounting database ... more, in fact, than I would have charged= +=20 +them to write a better system from scratch. + + +> Applying your strategy to all situations is not always going to produce +> the most cost-effective solution. + +That's very true. In fact, that could be taken as a "general truism" ... = +no=20 +one strategy applies to *all* situations. + +> PS. Josh, are you referring to Pascal's "Practical Issues In Database +> Management" book or does he have a different book out that I'm not aware +> of? + +Yes, you're correct. Sorry! + +--=20 +Josh Berkus +Aglio Database Solutions +San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Jan 31 13:29:30 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0D1F64774F2 + for ; + Fri, 31 Jan 2003 13:20:48 -0500 (EST) +Received: from jefftrout.com (h00a0cc4084e5.ne.client2.attbi.com + [24.128.215.169]) + by postgresql.org (Postfix) with SMTP id 650EC47709F + for ; + Fri, 31 Jan 2003 13:20:47 -0500 (EST) +Received: (qmail 47481 invoked from network); 31 Jan 2003 18:19:36 -0000 +Received: from unknown (HELO torgo) (threshar@10.10.10.10) + by 10.10.10.10 with SMTP; 31 Jan 2003 18:19:36 -0000 +Date: Fri, 31 Jan 2003 13:19:36 -0500 (EST) +From: Jeff +To: pgsql-performance@postgresql.org +Subject: Re: One large v. many small (fwd) +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/403 +X-Sequence-Number: 1050 + +On Thu, 30 Jan 2003, Gregory Wood wrote: + +> While you make an excellent point (i.e. you can't always through hardware, +> especially excessive hardware at the problem), I would err on the side of +> doing things the right way. It usually ends up making the software easier to +> maintain and add to. A poor design to save a few thousand dollars on +> hardware now can cost many tens of thousands (or more) dollars on +> programming time down the road. +> + + +fun story - I was part of a dot com and we had an informix database and +the schema was pretty "good" - ref integrity and "logical layout". What +happened +was our traffic started increasng dramatically. We ended up having to +disable all the ref integrity simply because it gave us a 50% boost. It +was unfortuate, but you have to do it. Sometimes you have to comprimise. +As for throwing hardware at it - it was already running on a $500k sun +box, an upgrade would have likely gone into the 7 digit range. +Not to mention you don't exactly get a quick turnaround on +hardware of that type.. a u10 perhaps, but not a big beefy box. +(Eventually we did upgrade the db machine when we got another round of +funding) + +so after a week of engineering and futzing we had things under control.. +(db changes, massive app changes (agressive caching)) + +Yes it was horrid to throw out RI (which caused some minor issues +later) but when the business is riding on it.. you make it work any way +you can. In a perfect world I would have done it another way, but when +the site is down (read: your business is not running, you are losing large +amounts of money) you need to put on your fire fighter suit, not your lab +coat. + +I remember one time we were featured on CNBC and our traffic jumped by +1000% (yes, 1000) - our poor machines were hosed. Now we did throw +hardware at this problem (more frontends) however aquiring hardware in +time of crisis is not terribly easy (took 3 days in this case). So you +have to look at your other routes. + +sometimes your design or some implementation details will be comprimised.. +its a fact of business. If the best design always won then why don't I +have an alpha for my machine machine? they are the fastest, best cpu +around. (I'll admit, alpha failed a lot because of marketing +issues and cost) Business drives everything. I'd rather continue getting +a paycheck than having a wonderfully designed db that doesn't perform +well and is causing us to lose money. + +If you have the ability (ie, you know your site is going to end up doing +22M page views, or some other statistic like that) to see what things will +be like later and are not fighting a fire, design is wonderful. (Lets not +forget time. I was just on a major project and they scheduled _3_ weeks +of design & coding.. we were quite upset about that one.. and they +arranged it so the launch date was set in stone. man.. worked some +long nights..) + +getting back to the original posters thing - why not just try a test to +see how things perform yourself? Try some tests with 3000 tables, and try +a test with 1 table with a client_id (int) field. Or as said, you could even make a boatload of views and +change your insertion logic.. + +anyway, sorry if I flamed anybody or if they took it personally. +just stating some experiences I've had. + +------------------------------------------------------------------------------ +Jeff Trout http://www.jefftrout.com/ + Ronald McDonald, with the help of cheese soup, + controls America from a secret volkswagon hidden in the past +------------------------------------------------------------------------------- + + + + +From pgsql-performance-owner@postgresql.org Fri Jan 31 13:43:35 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 74E7C4762C8 + for ; + Fri, 31 Jan 2003 13:43:33 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id D4EDD475FD9 + for ; + Fri, 31 Jan 2003 13:43:32 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2815030; Fri, 31 Jan 2003 10:42:52 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Jeff , pgsql-performance@postgresql.org +Subject: Re: One large v. many small (fwd) +Date: Fri, 31 Jan 2003 10:44:00 -0800 +X-Mailer: KMail [version 1.4] +References: +In-Reply-To: +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301311044.00583.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/404 +X-Sequence-Number: 1051 + + +Jeff, + +> so after a week of engineering and futzing we had things under control.. +> (db changes, massive app changes (agressive caching)) +>=20 +> Yes it was horrid to throw out RI (which caused some minor issues +> later) but when the business is riding on it.. you make it work any way +> you can. In a perfect world I would have done it another way, but when +> the site is down (read: your business is not running, you are losing large +> amounts of money) you need to put on your fire fighter suit, not your lab +> coat. + +Actually, I'd say this is a great example of what I'm advocating. You=20 +started out with a "correct" design, from an RDBMS perspective, and=20 +compromised on it only when the performance issues became insurmountable.= +=20=20 +That sounds like a good approach to me. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Jan 31 18:16:27 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9F66747A271 + for ; + Fri, 31 Jan 2003 18:16:26 -0500 (EST) +Received: from mail.sandvine.com (sandvine.com [199.243.201.138]) + by postgresql.org (Postfix) with ESMTP id 017CE47F877 + for ; + Fri, 31 Jan 2003 16:12:47 -0500 (EST) +Received: by mail.sandvine.com with Internet Mail Service (5.5.2653.19) + id ; Fri, 31 Jan 2003 16:12:48 -0500 +Message-ID: +From: Don Bowman +To: "'pgsql-performance@postgresql.org'" +Subject: not using index for select min(...) +Date: Fri, 31 Jan 2003 16:12:38 -0500 +MIME-Version: 1.0 +X-Mailer: Internet Mail Service (5.5.2653.19) +Content-Type: text/plain; + charset="iso-8859-1" +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/405 +X-Sequence-Number: 1052 + +I have a table which is very large (~65K rows). I have +a column in it which is indexed, and I wish to use for +a join. I'm finding that I'm using a sequential scan +for this when selecting a MIN. + +I've boiled this down to something like this: + +=> create table X( value int primary key ); +=> explain select min(value) from x; + Aggregate (cost=22.50..22.50 rows=1 width=4) + -> Seq Scan on x (cost=0.00..20.00 rows=1000 width=4) +=> \d x + Table "public.x" + Column | Type | Modifiers +--------+---------+----------- + value | integer | not null +Indexes: x_pkey primary key btree (value) + +Why wouldn't I be doing an index scan on this table? + +--don + +From pgsql-performance-owner@postgresql.org Fri Jan 31 20:49:37 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 134D84797C1 + for ; + Fri, 31 Jan 2003 20:49:36 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 5F37747D77C + for ; + Fri, 31 Jan 2003 18:31:02 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18ekci-0007f3-00 + for ; Fri, 31 Jan 2003 18:31:04 -0500 +Date: Fri, 31 Jan 2003 18:31:04 -0500 +From: Andrew Sullivan +To: "'pgsql-performance@postgresql.org'" +Subject: Re: not using index for select min(...) +Message-ID: <20030131183104.L24535@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + "'pgsql-performance@postgresql.org'" +References: +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: ; + from don@sandvine.com on Fri, Jan 31, 2003 at 04:12:38PM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/407 +X-Sequence-Number: 1054 + +On Fri, Jan 31, 2003 at 04:12:38PM -0500, Don Bowman wrote: +> Why wouldn't I be doing an index scan on this table? + +Because you're using the aggregate function min(). See + + + +A + +-- +---- +Andrew Sullivan 204-4141 Yonge Street +Liberty RMS Toronto, Ontario Canada + M2P 2A8 + +1 416 646 3304 x110 + + +From pgsql-performance-owner@postgresql.org Fri Jan 31 20:49:04 2003 +X-Original-To: pgsql-performance@postgresql.org +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 74E2F479DBF + for ; + Fri, 31 Jan 2003 20:49:02 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id EC50D47DAFE + for ; + Fri, 31 Jan 2003 18:29:56 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2815469; Fri, 31 Jan 2003 15:30:04 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Don Bowman , + "'pgsql-performance@postgresql.org'" +Subject: Re: not using index for select min(...) +Date: Fri, 31 Jan 2003 15:31:12 -0800 +X-Mailer: KMail [version 1.4] +References: +In-Reply-To: +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200301311531.12605.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200301/406 +X-Sequence-Number: 1053 + +Don, + +> I have a table which is very large (~65K rows). I have +> a column in it which is indexed, and I wish to use for +> a join. I'm finding that I'm using a sequential scan +> for this when selecting a MIN. + +Due to Postgres' system of extensible aggregates (i.e. you can write your o= +wn=20 +aggregates), all aggregates will trigger a Seq Scan in a query. It's a=20 +known drawrback that nobody has yet found a good way around. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + +