diff --git "a/pgsql-performance.200212" "b/pgsql-performance.200212" new file mode 100644--- /dev/null +++ "b/pgsql-performance.200212" @@ -0,0 +1,18310 @@ +From pgsql-performance-owner@postgresql.org Mon Dec 2 10:47:04 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 870D347668E + for ; + Mon, 2 Dec 2002 10:47:02 -0500 (EST) +Received: from gatefox.foxi.nl (a194-109-246-192.adsl.xs4all.nl + [194.109.246.192]) + by postgresql.org (Postfix) with ESMTP id 16E614765FE + for ; + Mon, 2 Dec 2002 10:44:13 -0500 (EST) +Received: from techfox (techfox.foxi [192.168.0.79]) + by gatefox.foxi.nl (8.10.2/8.10.2) with ESMTP id gB2FiGJ07432 + for ; Mon, 2 Dec 2002 16:44:16 +0100 +Content-Type: text/plain; + charset="iso-8859-15" +From: "ir. F.T.M. van Vugt bc." +Organization: Foxi Consultants in Technology +To: Postgresql performance +Subject: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with UNION +Date: Mon, 2 Dec 2002 16:45:55 +0100 +User-Agent: KMail/1.4.3 +References: <1037036692.29703.213.camel@CPE-144-132-182-167> + <1037074231.29703.234.camel@CPE-144-132-182-167> + <1037076680.66615.21.camel@jester> +In-Reply-To: <1037076680.66615.21.camel@jester> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212021645.55032.ftm.van.vugt@foxi.nl> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/1 +X-Sequence-Number: 417 + +L.S. + +The query below runs 10-20 times slower under v7.3 than it did under v7.2.3: + +- hardware is the same +- standard install of postgresql, both version had stats-collection enabled +- v7.2.3 had no multibyte and no locale, obviously v7.3 does +- *very* recent vacuum analyse + + +I expected some overhead due to the enabled mulitbyte, but not this much.. = +;( + +BTW, there are a few other queries that are performing *real* slow, but I'm= +=20 +hoping this one will give away a cause for the overall problem... + + +Could anybody offer an idea? + + + +trial=3D# explain analyse select foo.*, c.id from + (select *, 't' from lijst01_table union all=20 + select *, 't' from lijst02_table union all=20 + select *, 'f' from lijst03_table union all=20 + select *, 'f' from lijst04_table union all=20 + select *, 't' from lijst04b_table ) as foo + inner join creditor c=20 + on foo.dflt_creditor_id =3D c.old_creditor_id + order by old_id; + +* foo.dflt_creditor_id is of type varchar(20) +* c.old_creditor_id is of type text + + +The plan below shows something weird is happening during the join, but I ca= +n't=20 +explain it. + + +TIA, + + + + + +Frank. + + + + + QUERY PL= +AN +---------------------------------------------------------------------------= +--------------------------------------------------------------------- + Sort (cost=3D54103.74..54116.18 rows=3D4976 width=3D498) (actual=20 +time=3D234595.27..234607.58 rows=3D4976 loops=3D1) + Sort Key: foo.old_id + -> Nested Loop (cost=3D0.00..53798.19 rows=3D4976 width=3D498) (actual= +=20 +time=3D7559.20..234476.70 rows=3D4976 loops=3D1) + Join Filter: ("inner".dflt_creditor_id =3D=20 +("outer".old_creditor_id)::text) + -> Seq Scan on creditor c (cost=3D0.00..8.27 rows=3D227 width=3D= +14)=20 +(actual time=3D0.05..7.35 rows=3D227 loops=3D1) + -> Subquery Scan foo (cost=3D0.00..174.76 rows=3D4976 width=3D15= +0)=20 +(actual time=3D0.25..969.47 rows=3D4976 loops=3D227) + -> Append (cost=3D0.00..174.76 rows=3D4976 width=3D150) (a= +ctual=20 +time=3D0.20..658.14 rows=3D4976 loops=3D227) + -> Subquery Scan "*SELECT* 1" (cost=3D0.00..2.46 row= +s=3D46=20 +width=3D145) (actual time=3D0.19..6.26 rows=3D46 loops=3D227) + -> Seq Scan on lijst01_table (cost=3D0.00..2.4= +6=20 +rows=3D46 width=3D145) (actual time=3D0.10..3.40 rows=3D46 loops=3D227) + -> Subquery Scan "*SELECT* 2" (cost=3D0.00..30.62=20 +rows=3D862 width=3D150) (actual time=3D0.16..111.38 rows=3D862 loops=3D227) + -> Seq Scan on lijst02_table (cost=3D0.00..30.= +62=20 +rows=3D862 width=3D150) (actual time=3D0.09..59.79 rows=3D862 loops=3D227) + -> Subquery Scan "*SELECT* 3" (cost=3D0.00..48.63=20 +rows=3D1363 width=3D148) (actual time=3D0.16..166.98 rows=3D1363 loops=3D22= +7) + -> Seq Scan on lijst03_table (cost=3D0.00..48.= +63=20 +rows=3D1363 width=3D148) (actual time=3D0.09..87.45 rows=3D1363 loops=3D227) + -> Subquery Scan "*SELECT* 4" (cost=3D0.00..92.03=20 +rows=3D2703 width=3D134) (actual time=3D0.15..338.66 rows=3D2703 loops=3D22= +7) + -> Seq Scan on lijst04_table (cost=3D0.00..92.= +03=20 +rows=3D2703 width=3D134) (actual time=3D0.09..176.41 rows=3D2703 loops=3D22= +7) + -> Subquery Scan "*SELECT* 5" (cost=3D0.00..1.02 row= +s=3D2=20 +width=3D134) (actual time=3D0.16..0.28 rows=3D2 loops=3D227) + -> Seq Scan on lijst04b_table (cost=3D0.00..1.= +02=20 +rows=3D2 width=3D134) (actual time=3D0.09..0.16 rows=3D2 loops=3D227) + Total runtime: 234624.07 msec +(18 rows) + + + +From pgsql-performance-owner@postgresql.org Mon Dec 2 11:02:29 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4C528476469 + for ; + Mon, 2 Dec 2002 11:02:27 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 1F151475FDE + for ; + Mon, 2 Dec 2002 11:00:08 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18IszV-0004nG-00 + for ; Mon, 02 Dec 2002 11:00:13 -0500 +Date: Mon, 2 Dec 2002 11:00:12 -0500 +From: Andrew Sullivan +To: Postgresql performance +Subject: Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with + UNION +Message-ID: <20021202110012.G12906@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + Postgresql performance +References: <1037036692.29703.213.camel@CPE-144-132-182-167> + <1037074231.29703.234.camel@CPE-144-132-182-167> + <1037076680.66615.21.camel@jester> + <200212021645.55032.ftm.van.vugt@foxi.nl> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <200212021645.55032.ftm.van.vugt@foxi.nl>; + from ftm.van.vugt@foxi.nl on Mon, Dec 02, 2002 at 04:45:55PM +0100 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/2 +X-Sequence-Number: 418 + +On Mon, Dec 02, 2002 at 04:45:55PM +0100, ir. F.T.M. van Vugt bc. wrote: +> L.S. +> +> The query below runs 10-20 times slower under v7.3 than it did under v7.2.3: + +> - v7.2.3 had no multibyte and no locale, obviously v7.3 does + +Are you using the C locale? If it was not enabled in 7.2.3, I +believe it was using C anyway; if you have some other locale, it's +now getting picked up, and that might be the source of the slower +performance (?). + +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 Dec 2 11:14:32 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BE70847646B + for ; + Mon, 2 Dec 2002 11:14:31 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id D1F674760D5 + for ; + Mon, 2 Dec 2002 11:13:46 -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 gB2GDips018913; + Mon, 2 Dec 2002 11:13:45 -0500 (EST) +To: "ir. F.T.M. van Vugt bc." +Cc: Postgresql performance +Subject: Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with + UNION +In-reply-to: <200212021645.55032.ftm.van.vugt@foxi.nl> +References: <1037036692.29703.213.camel@CPE-144-132-182-167> + <1037074231.29703.234.camel@CPE-144-132-182-167> + <1037076680.66615.21.camel@jester> + <200212021645.55032.ftm.van.vugt@foxi.nl> +Comments: In-reply-to "ir. F.T.M. van Vugt bc." + message dated "Mon, 02 Dec 2002 16:45:55 +0100" +Date: Mon, 02 Dec 2002 11:13:44 -0500 +Message-ID: <18912.1038845624@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/3 +X-Sequence-Number: 419 + +"ir. F.T.M. van Vugt bc." writes: +> The query below runs 10-20 times slower under v7.3 than it did under v7.2.3: + +I don't suppose you have explain output for it from 7.2.3? + +It seems strange to me that the thing is picking a nestloop join here. +Either merge or hash would make more sense ... oh, but wait: + +> inner join creditor c +> on foo.dflt_creditor_id = c.old_creditor_id + +> * foo.dflt_creditor_id is of type varchar(20) +> * c.old_creditor_id is of type text + +IIRC, merge and hash only work on plain Vars --- the implicit type +coercion from varchar to text is what's putting the kibosh on a more +intelligent join plan. Can you fix your table declarations to agree +on the datatype? If you don't want to change the tables, another +possibility is something like + + select foo.*, c.id from + (select *, dflt_creditor_id::text as key, 't' from lijst01_table union all + select *, dflt_creditor_id::text as key, 't' from lijst02_table union all + select *, dflt_creditor_id::text as key, 'f' from lijst03_table union all + select *, dflt_creditor_id::text as key, 'f' from lijst04_table union all + select *, dflt_creditor_id::text as key, 't' from lijst04b_table ) as foo + inner join creditor c + on foo.key = c.old_creditor_id + order by old_id; + +ie, force the type coercion to occur down inside the union, not at the +join. + +This doesn't explain the slowdown from 7.2.3, though --- it had the same +deficiency. (I am hoping to get around to fixing it for 7.4.) + +It could easy be that --enable-locale explains the slowdown. Are you +running 7.4 in C locale, or something else? Comparisons in locales +like en_US can be *way* slower than in C locale. You can use +pg_controldata to check this for sure. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Mon Dec 2 12:18:53 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4651E475EDF + for ; + Mon, 2 Dec 2002 12:18:53 -0500 (EST) +Received: from gatefox.foxi.nl (a194-109-246-192.adsl.xs4all.nl + [194.109.246.192]) + by postgresql.org (Postfix) with ESMTP id 266464763B6 + for ; + Mon, 2 Dec 2002 12:18:29 -0500 (EST) +Received: from techfox (techfox.foxi [192.168.0.79]) + by gatefox.foxi.nl (8.10.2/8.10.2) with ESMTP id gB2HIRJ22951; + Mon, 2 Dec 2002 18:18:27 +0100 +Content-Type: text/plain; + charset="iso-8859-15" +From: "ir. F.T.M. van Vugt bc." +Organization: Foxi Consultants in Technology +To: Tom Lane , + Andrew Sullivan +Subject: Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with + UNION +Date: Mon, 2 Dec 2002 18:20:06 +0100 +User-Agent: KMail/1.4.3 +References: <1037036692.29703.213.camel@CPE-144-132-182-167> + <200212021645.55032.ftm.van.vugt@foxi.nl> + <18912.1038845624@sss.pgh.pa.us> +In-Reply-To: <18912.1038845624@sss.pgh.pa.us> +Cc: Postgresql performance +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212021820.06380.ftm.van.vugt@foxi.nl> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/4 +X-Sequence-Number: 420 + +Wow, the speed at which you guys are responding never ceases to amaze me ! + +TL> I don't suppose you have explain output for it from 7.2.3? + +Nope, sorry 'bout that. +BTW, the performance comparison was not a 'hard' (measured) number, but a= +=20 +watch-timed conclusion on a complete run of a conversiontool this query is= +=20 +part of. + +TL> It seems strange to me that the thing is picking a nestloop join here. +TL> oh, but wait: the implicit type coercion from varchar to text is what's +TL> putting the kibosh on a more intelligent join plan. + +You're abolutely right, I'm back in business when putting a type coercion= +=20 +inside the union: + +trial=3D# explain select foo.*, c.id from + + + QUERY PLAN +---------------------------------------------------------------------------= +---------------------- + Sort (cost=3D588.66..601.10 rows=3D4976 width=3D530) + Sort Key: foo.old_id + -> Hash Join (cost=3D8.84..283.12 rows=3D4976 width=3D530) + Hash Cond: ("outer"."key" =3D "inner".old_creditor_id) + -> Subquery Scan foo (cost=3D0.00..174.76 rows=3D4976 width=3D15= +0) + -> Append (cost=3D0.00..174.76 rows=3D4976 width=3D150) + + +(as opposed to: (cost=3D54103.74..54116.18 rows=3D4976 width=3D498)) + + + +> This doesn't explain the slowdown from 7.2.3, though --- it had the same +> deficiency. (I am hoping to get around to fixing it for 7.4.) + +Mmm, that's weird. Could be caused by somebody over here who has done 'work= +'=20 +on some queries... ;( =3D> I'll check on that, if I can be absolutely sure= + the=20 +7.2.3 version planned *this* query differently, I'll let you know. Sorry=20 +'bout that.... + + +AS> It could easy be that --enable-locale explains the slowdown. Are you +AS> running 7.4 in C locale, or something else? + +On v7.2.3. I wasn't doing anything with locale. +The v7.3 put 'POSIX' into the postgresql.conf file, changing that into 'C'= +=20 +didn't seem to make any difference. + +AS> Comparisons in locales like en_US can be *way* slower than in C locale. +AS> You can use pg_controldata to check this for sure. + +O.K. this seems to help a lot as well ! + +I'll have to take a look at both ISO C and POSIX locale, 'cause I wouldn't= +=20 +have expected it to make such a difference... + +On the original v7.3, pg_controldata returned 'posix', upon changing the=20 +postgresql.conf it confirmed the change to 'C'. This resulted in: + + +POSIX_trial=3D# explain analyse select foo.*, c.id from=20 + + QUERY PLAN +---------------------------------------------------------------------------= +-------------------------------------------------------------------- + Sort (cost=3D588.66..601.10 rows=3D4976 width=3D530) (actual time=3D2482.= +51..2530.54=20 +rows=3D4976 loops=3D1) + + Total runtime: 2636.15 msec + + +C_trial=3D# explain analyse select foo.*, c.id from=20 + + QUERY PLAN +---------------------------------------------------------------------------= +------------------------------------------------------------------- + Sort (cost=3D588.66..601.10 rows=3D4976 width=3D530) (actual time=3D1537.= +05..1549.34=20 +rows=3D4976 loops=3D1) + + Total runtime: 1567.76 msec + + + + +Hey, I'm happy ;-) + + + +Thanks a lot !!! + + + + + + +Frank. + +From pgsql-performance-owner@postgresql.org Mon Dec 2 13:54:05 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id F078347671C + for ; + Mon, 2 Dec 2002 13:54:03 -0500 (EST) +Received: from o2.hostbaby.com (o2.hostbaby.com [208.187.29.121]) + by postgresql.org (Postfix) with SMTP id 74214476CA4 + for ; + Mon, 2 Dec 2002 13:30:48 -0500 (EST) +Received: (qmail 11478 invoked from network); 2 Dec 2002 18:30:50 -0000 +Received: from unknown (HELO l-i-e.com) (127.0.0.1) + by localhost with SMTP; 2 Dec 2002 18:30:50 -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, 2 Dec 2002 10:30:50 -0800 (PST) +Message-ID: <49486.216.80.95.13.1038853850.squirrel@www.l-i-e.com> +Date: Mon, 2 Dec 2002 10:30:50 -0800 (PST) +Subject: +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: 200212/5 +X-Sequence-Number: 421 + +[I hope job postings are kosher...] + +I need help optimizing a PostgreSQL application: + +Full-text search +~17,000 records +Articles (text) are about 10K long on average, ranging from 0 to 278K. + +I don't know if we need to throw more RAM, more hard drive, more +comparison RAM in postmaster.conf or build a concordance or if this is +just not something that can be done within our budget. + +I can't even seem to get the PostgreSQL profiling output using "-s" in the +startup of postmaster and client to determine what the db engine is doing. + +I don't understand why PostgreSQL sometimes chooses not to use the +existing INDEXes to do an index scan instead of sequential scan -- Does it +really think sequential will be faster, or does it eliminate an index scan +because there won't be enough hard drive or swap space to do it? + +Currently, full text search queries take on the order of 2 minutes to +execute. +We need them to be happening in 5 seconds, if at all possible. + +Unfortunately, this needs to happen EARLY THIS WEEK, if at all possible. + +Contact me off-list with some idea of price/availability/references if you +are interested in taking on this task. + +THANKS! + + + + +From pgsql-performance-owner@postgresql.org Mon Dec 2 14:39:04 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 515B4475C8B + for ; + Mon, 2 Dec 2002 14:39:03 -0500 (EST) +Received: from jester.senspire.com (unknown [216.208.117.7]) + by postgresql.org (Postfix) with ESMTP id 0EAAE476CD9 + for ; + Mon, 2 Dec 2002 14:19:46 -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 gB2JKcWK060281; + Mon, 2 Dec 2002 14:20:39 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: +From: Rod Taylor +To: typea@l-i-e.com +Cc: Pgsql Performance +In-Reply-To: <49486.216.80.95.13.1038853850.squirrel@www.l-i-e.com> +References: <49486.216.80.95.13.1038853850.squirrel@www.l-i-e.com> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-TvAEIQlCUT7Ufwiyw113" +Organization: +Message-Id: <1038856838.46704.42.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 02 Dec 2002 14:20:38 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/6 +X-Sequence-Number: 422 + +--=-TvAEIQlCUT7Ufwiyw113 +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + + +> I don't understand why PostgreSQL sometimes chooses not to use the +> existing INDEXes to do an index scan instead of sequential scan -- Does it +> really think sequential will be faster, or does it eliminate an index scan + +Yes, and it's generally right. + +> because there won't be enough hard drive or swap space to do it? + +Nope. Simply because of time it takes to read from the disk. An index +scan makes ~ 1 read per tuple and sequential scans make one per page +(gross simplification). + +> Currently, full text search queries take on the order of 2 minutes to +> execute. +> We need them to be happening in 5 seconds, if at all possible. + +How about a couple of explains of the queries. What kind of tuning have +you done in postgresql.conf. Whats your hardware like? Have you +partitioned the data to separate disks in any way? + +Are you doing mostly (all?) reads? Some writes? Perhaps clustering? + +Is this on 7.2 or 7.3? What is the Locale? C or en_US or something +else? + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-TvAEIQlCUT7Ufwiyw113 +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) + +iD8DBQA967KG6DETLow6vwwRAjv4AJ9ac6S80DEiYF6iT2lHrgIPKvDEnACcC2fQ +YJX8qImLBzislTzj83ryUBM= +=Lf/b +-----END PGP SIGNATURE----- + +--=-TvAEIQlCUT7Ufwiyw113-- + + +From pgsql-performance-owner@postgresql.org Mon Dec 2 15:55:21 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 16D4747638D + for ; + Mon, 2 Dec 2002 15:55:21 -0500 (EST) +Received: from o2.hostbaby.com (o2.hostbaby.com [208.187.29.121]) + by postgresql.org (Postfix) with SMTP id 00EE2476676 + for ; + Mon, 2 Dec 2002 15:45:39 -0500 (EST) +Received: (qmail 60841 invoked from network); 2 Dec 2002 20:45:43 -0000 +Received: from unknown (HELO l-i-e.com) (127.0.0.1) + by localhost with SMTP; 2 Dec 2002 20:45:42 -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, 2 Dec 2002 12:45:43 -0800 (PST) +Message-ID: <50235.216.80.95.13.1038861943.squirrel@www.l-i-e.com> +Date: Mon, 2 Dec 2002 12:45:43 -0800 (PST) +Subject: Re: +From: +To: +In-Reply-To: <1038856838.46704.42.camel@jester> +References: <49486.216.80.95.13.1038853850.squirrel@www.l-i-e.com> + <1038856838.46704.42.camel@jester> +X-Priority: 3 +Importance: Normal +Cc: +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: 200212/7 +X-Sequence-Number: 423 + +>> I don't understand why PostgreSQL sometimes chooses not to use the +>> existing INDEXes to do an index scan instead of sequential scan -- +>> Does it really think sequential will be faster, or does it eliminate +>> an index scan +> +> Yes, and it's generally right. +> +>> because there won't be enough hard drive or swap space to do it? +> +> Nope. Simply because of time it takes to read from the disk. An index +> scan makes ~ 1 read per tuple and sequential scans make one per page +> (gross simplification). + +Hmmm. An "index" is apparently nothing like I expected it to be... + +Here I thought it would be some quick hash-table small data-set lookup +with a reference to the OID -- and that most of the hash tables could just +be loaded in one fell swoop. + +Oh well. + +>> Currently, full text search queries take on the order of 2 minutes to +>> execute. +>> We need them to be happening in 5 seconds, if at all possible. +> +> How about a couple of explains of the queries. + +Explains were posted previously, but I'll do a couple more. + +At its simplest, this takes 30 seconds: + +explain select article.* from article where lower(text) like '%einstein%'; +NOTICE: QUERY PLAN: + +Seq Scan on article (cost=0.00..1155.01 rows=1 width=216) + +Or, slightly more complex: + +explain SELECT DISTINCT *, 0 + (0 + 10 * (lower(title) like '%einstein%') +::int + 10 * (lower(author_flattened) like '%einstein%') ::int + 30 * +(lower(subject_flattened) like '%einstein%') ::int + 30 * (lower(text) +LIKE '%einstein%') ::int + 9 * (substring(lower(title), 1, 20) like +'%einstein%') ::int + 25 * (substring(lower(text), 1, 20) LIKE +'%einstein%') ::int ) AS points FROM article WHERE TRUE AND (FALSE OR +(lower(title) like '%einstein%') OR (lower(author_flattened) like +'%einstein%') OR (lower(subject_flattened) like '%einstein%') OR +(lower(text) LIKE '%einstein%') ) ORDER BY points desc, volume, number, +article.article LIMIT 10, 0; +NOTICE: QUERY PLAN: + +Limit (cost=1418.03..1418.08 rows=1 width=216) + -> Unique (cost=1418.03..1418.08 rows=1 width=216) + -> Sort (cost=1418.03..1418.03 rows=1 width=216) + -> Seq Scan on article (cost=0.00..1418.02 rows=1 width=216) + + +> What kind of tuning have +> you done in postgresql.conf. + +None. Never really understood what that one memory setting would affect... + +And the rest of the options seemed to be about logging output (which I +also can't seem to crank up to the level of getting query analysis out). + +I RTFM, but actually comprehending what was written ... :-^ + +> Whats your hardware like? + +processor : 0 +vendor_id : GenuineIntel +cpu family : 6 +model : 11 +model name : Intel(R) Pentium(R) III CPU family 1400MHz +stepping : 1 +cpu MHz : 1406.005 +cache size : 512 KB +fdiv_bug : no +hlt_bug : no +f00f_bug : no +coma_bug : no +fpu : yes +fpu_exception : yes +cpuid level : 2 +wp : yes +flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca +cmov pat pse36 mmx fxsr sse +bogomips : 2804.94 + + total: used: free: shared: buffers: cached: +Mem: 921235456 736669696 184565760 749568 75321344 592257024 +Swap: 2097143808 15368192 2081775616 +MemTotal: 899644 kB +MemFree: 180240 kB +MemShared: 732 kB +Buffers: 73556 kB +Cached: 573896 kB +SwapCached: 4480 kB +Active: 433776 kB +Inact_dirty: 182208 kB +Inact_clean: 36680 kB +Inact_target: 229376 kB +HighTotal: 0 kB +HighFree: 0 kB +LowTotal: 899644 kB +LowFree: 180240 kB +SwapTotal: 2047992 kB +SwapFree: 2032984 kB + + + +> Have you +> partitioned the data to separate disks in any way? + +No, except when attempting to do the PostgreSQL contrib/fulltextindex we +clustered the _fti table by loading it in word order. + +> Are you doing mostly (all?) reads? Some writes? Perhaps clustering? + +Mostly reads. +Some writes by: + Admin fixing typos, adding new articles + Nightly cron jobs to "flatten" large-scale JOINs into text contatenations + (We could get rid of that and go back to the JOINs, now that we've +figured out that it's really the full text search that's killing us, not +the JOINs) + +> Is this on 7.2 or 7.3? + +7.1.3 + +> What is the Locale? C or en_US or something +> else? + +AFAIK, we didn't do anything to alter the locale from whatever the default +would be... + + + + +From pgsql-performance-owner@postgresql.org Mon Dec 2 16:21:55 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1AB284763B2 + for ; + Mon, 2 Dec 2002 16:21:52 -0500 (EST) +Received: from rh72.home.ee (adsl1030.estpak.ee [213.168.29.11]) + by postgresql.org (Postfix) with ESMTP id 1522947637E + for ; + Mon, 2 Dec 2002 16:18:33 -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 gB2LIUA8002852; + Tue, 3 Dec 2002 02:18:31 +0500 +Received: (from hannu@localhost) + by rh72.home.ee (8.12.5/8.12.5/Submit) id gB2LIFBD002850; + Tue, 3 Dec 2002 02:18:15 +0500 +X-Authentication-Warning: rh72.home.ee: hannu set sender to hannu@tm.ee using + -f +Subject: Re: +From: Hannu Krosing +To: typea@l-i-e.com +Cc: pgsql-performance@postgresql.org, rbt@rbt.ca +In-Reply-To: <50235.216.80.95.13.1038861943.squirrel@www.l-i-e.com> +References: <49486.216.80.95.13.1038853850.squirrel@www.l-i-e.com> + <1038856838.46704.42.camel@jester> + <50235.216.80.95.13.1038861943.squirrel@www.l-i-e.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1038863893.1942.3.camel@rh72.home.ee> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 03 Dec 2002 02:18:14 +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/8 +X-Sequence-Number: 424 + +typea@l-i-e.com kirjutas T, 03.12.2002 kell 01:45: +> Explains were posted previously, but I'll do a couple more. +> +> At its simplest, this takes 30 seconds: +> +> explain select article.* from article where lower(text) like '%einstein%'; +> NOTICE: QUERY PLAN: +> +> Seq Scan on article (cost=0.00..1155.01 rows=1 width=216) + +searches with LIKE use indexes only when the like expression starts +with a string (like 'einstein%') and even then only if in C locale. + +You should check out some real full-text index add-ons, like contrib/tsearch or +construct your own using your imagination plus contrib/intarray and contrib/intagg :) + +--------------- +Hannu + + + + + + +From pgsql-performance-owner@postgresql.org Mon Dec 2 18:49:34 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 43EFB475D01 + for ; + Mon, 2 Dec 2002 18:49:32 -0500 (EST) +Received: from gatefox.foxi.nl (a194-109-246-192.adsl.xs4all.nl + [194.109.246.192]) + by postgresql.org (Postfix) with ESMTP id A4125475E60 + for ; + Mon, 2 Dec 2002 18:49:28 -0500 (EST) +Received: from techfox (techfox.foxi [192.168.0.79]) + by gatefox.foxi.nl (8.10.2/8.10.2) with ESMTP id gB2NnPJ26253; + Tue, 3 Dec 2002 00:49:25 +0100 +Content-Type: text/plain; + charset="us-ascii" +From: "ir. F.T.M. van Vugt bc." +Organization: Foxi Consultants in Technology +To: Tom Lane +Subject: Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with + UNION +Date: Tue, 3 Dec 2002 00:51:03 +0100 +User-Agent: KMail/1.4.3 +Cc: Postgresql performance +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212030051.03635.ftm.van.vugt@foxi.nl> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/9 +X-Sequence-Number: 425 + +(Should probably be in [SQL] by now....) + +I've changed my table declarations to agree on the datatypes and only one= +=20 +simular problem with an update-query doesn't seem to be solved. + +(see plan below) + +* the concatenation in the lbar select can't be avoided, it's just the way = +the=20 +data is =3D> this does result in a resulting type 'text', AFAIK + +* the aux_address.old_id is also of type 'text' + + +Still, the planner does a nested loop here against large costs... ;( + + +Any hints on this (last) one....? + + + +TIA, + + + + + +Frank. + + + +trial=3D# explain update address set region_id =3D lbar.region_id from + (select debtor_id || '-' || address_seqnr as id, region_id from + list_base_regions) as lbar, aux_address aa=20 + where lbar.id =3D aa.old_id and address.id =3D aa.id; + QUERY PLAN +---------------------------------------------------------------------------= +------------------------------------------- + Merge Join (cost=3D1.07..65.50 rows=3D3 width=3D253) + Merge Cond: ("outer".id =3D "inner".id) + -> Nested Loop (cost=3D0.00..643707.03 rows=3D3980 width=3D28) + Join Filter: (((("inner".debtor_id)::text || '-'::text) ||=20 +("inner".address_seqnr)::text) =3D "outer".old_id) + -> Index Scan using aux_address_idx2 on aux_address aa=20=20 +(cost=3D0.00..81.88 rows=3D3989 width=3D16) + -> Seq Scan on list_base_regions (cost=3D0.00..71.80 rows=3D3980= +=20 +width=3D12) + -> Sort (cost=3D1.07..1.08 rows=3D3 width=3D225) + Sort Key: address.id + -> Seq Scan on address (cost=3D0.00..1.05 rows=3D3 width=3D225) + Filter: ((id =3D 1) IS NOT TRUE) +(10 rows) + + +From pgsql-performance-owner@postgresql.org Mon Dec 2 22:56:05 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A2DD4475CC7 + for ; + Mon, 2 Dec 2002 22:56:03 -0500 (EST) +Received: from lakemtao04.cox.net (lakemtao04.cox.net [68.1.17.241]) + by postgresql.org (Postfix) with ESMTP id 079ED475CC4 + for ; + Mon, 2 Dec 2002 22:56:03 -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 <20021203035607.TWFK1248.lakemtao04.cox.net@[192.168.1.1]> + for ; + Mon, 2 Dec 2002 22:56:07 -0500 +Subject: Re: +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <49486.216.80.95.13.1038853850.squirrel@www.l-i-e.com> +References: <49486.216.80.95.13.1038853850.squirrel@www.l-i-e.com> +Content-Type: text/plain +Organization: +Message-Id: <1038887764.4660.49.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 02 Dec 2002 21:56:04 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/10 +X-Sequence-Number: 426 + +On Mon, 2002-12-02 at 12:30, typea@l-i-e.com wrote: +> [I hope job postings are kosher...] +> +> I need help optimizing a PostgreSQL application: +> +> Full-text search +> ~17,000 records +> Articles (text) are about 10K long on average, ranging from 0 to 278K. +> +> I don't know if we need to throw more RAM, more hard drive, more +> comparison RAM in postmaster.conf or build a concordance or if this is +> just not something that can be done within our budget. +> +> I can't even seem to get the PostgreSQL profiling output using "-s" in the +> startup of postmaster and client to determine what the db engine is doing. +> +> I don't understand why PostgreSQL sometimes chooses not to use the +> existing INDEXes to do an index scan instead of sequential scan -- Does it +> really think sequential will be faster, or does it eliminate an index scan +> because there won't be enough hard drive or swap space to do it? +> +> Currently, full text search queries take on the order of 2 minutes to +> execute. +> We need them to be happening in 5 seconds, if at all possible. +> +> Unfortunately, this needs to happen EARLY THIS WEEK, if at all possible. +> +> Contact me off-list with some idea of price/availability/references if you +> are interested in taking on this task. + +After reading the thread to see that your box has what looks like +1GB RAM, and firing up bc(1) to see that 17K articles each of +which is ~10KB == 166MB, it seems to this simple mind that given +enough buffers, you could suck all of the articles into the +buffers. Thus, no more disk IO, but boy would it burn up the CPU! + +Also, I think that I might write some sort of "book index pre-processor" +to run against each article, to create, for each article, a list of +words plus byte offsets. (Some tweaking would have to occur in order +to handle capitalization vagaries. Probably capitalize all "index +words".) (Yes, this method has the limitation of [sub-]word searches +instead of arbitrary string searches, + +Then, insert all that data into a 3rd table (T_LOOKUP) whose structure +is: + val TEXT (primary key) + article_name TEXT + byte_offset INTEGER + +Then, 'EINSTEIN%' queries would go against T_LOOKUP instead of the +articles table. + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "they love our milk and honey, but preach about another | +| way of living" | +| Merle Haggard, "The Fighting Side Of Me" | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Tue Dec 3 00:46:40 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D376D475E20 + for ; + Tue, 3 Dec 2002 00:46:39 -0500 (EST) +Received: from cs.uoregon.edu (vitalstatistix.cs.uoregon.edu [128.223.4.19]) + by postgresql.org (Postfix) with ESMTP id 292EC475CC7 + for ; + Tue, 3 Dec 2002 00:46:39 -0500 (EST) +Received: from ix.cs.uoregon.edu (ix.cs.uoregon.edu [128.223.4.21]) + by cs.uoregon.edu (8.11.0/8.11.0) with ESMTP id gB35kij03782 + for ; + Mon, 2 Dec 2002 21:46:44 -0800 (PST) +Date: Mon, 2 Dec 2002 21:46:43 -0800 (PST) +From: li li +To: +Subject: Is there any limitations +In-Reply-To: <1038887764.4660.49.camel@haggis> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/11 +X-Sequence-Number: 427 + + +for the maximum number of tables in a database. + +I'm thinking about separating a table with up to millions of rows into +several tables with the same set of columns to speed up some complex +queries. As the size of the original table is increasing fast, I want +to get it separated once the size grows up to a limit. So there +will be a large amount of tables (having same structure) in a database. Is +there any potential performance problem with this design? + +Thanks. + +Li Li + + + +From pgsql-performance-owner@postgresql.org Tue Dec 3 00:59:48 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8281F475CC7 + for ; + Tue, 3 Dec 2002 00:59:47 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id CD98E475A09 + for ; + Tue, 3 Dec 2002 00:59:46 -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 gB35xipd020528; + Tue, 3 Dec 2002 00:59:45 -0500 (EST) +To: "ir. F.T.M. van Vugt bc." +Cc: Postgresql performance +Subject: Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with + UNION +In-reply-to: <200212030051.03635.ftm.van.vugt@foxi.nl> +References: <200212030051.03635.ftm.van.vugt@foxi.nl> +Comments: In-reply-to "ir. F.T.M. van Vugt bc." + message dated "Tue, 03 Dec 2002 00:51:03 +0100" +Date: Tue, 03 Dec 2002 00:59:44 -0500 +Message-ID: <20527.1038895184@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/12 +X-Sequence-Number: 428 + +"ir. F.T.M. van Vugt bc." writes: +> Any hints on this (last) one....? + +> -> Nested Loop (cost=0.00..643707.03 rows=3980 width=28) +> Join Filter: (((("inner".debtor_id)::text || '-'::text) || +> ("inner".address_seqnr)::text) = "outer".old_id) + +Looks to me like debtor_id and address_seqnr are not text type, but are +being compared to things that are text. Hard to tell exactly what's +going on though --- I suppose this query is getting rewritten by a rule? + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Dec 3 04:38:25 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3EC794763E3 + for ; + Tue, 3 Dec 2002 04:38:24 -0500 (EST) +Received: from gatefox.foxi.nl (a194-109-246-192.adsl.xs4all.nl + [194.109.246.192]) + by postgresql.org (Postfix) with ESMTP id A1C8A475DD0 + for ; + Tue, 3 Dec 2002 04:36:33 -0500 (EST) +Received: from techfox (techfox.foxi [192.168.0.79]) + by gatefox.foxi.nl (8.10.2/8.10.2) with ESMTP id gB39aWJ09319; + Tue, 3 Dec 2002 10:36:32 +0100 +Content-Type: text/plain; + charset="iso-8859-15" +From: "Frank van Vugt" +Organization: Foxi Consultants in Technology +To: Tom Lane +Subject: Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with + UNION +Date: Tue, 3 Dec 2002 10:38:10 +0100 +User-Agent: KMail/1.4.3 +References: <200212030051.03635.ftm.van.vugt@foxi.nl> + <20527.1038895184@sss.pgh.pa.us> +In-Reply-To: <20527.1038895184@sss.pgh.pa.us> +Cc: Postgresql performance +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212031038.10860.ftm.van.vugt@foxi.nl> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/13 +X-Sequence-Number: 429 + +> > Any hints on this (last) one....? +> > -> Nested Loop (cost=3D0.00..643707.03 rows=3D3980 width=3D28) +> > Join Filter: (((("inner".debtor_id)::text || '-'::text) || +> > ("inner".address_seqnr)::text) =3D "outer".old_id) +> +> Looks to me like debtor_id and address_seqnr are not text type, but are +> being compared to things that are text.=20 + +They were coerced, yes, but changing those original types helps only so muc= +h: + +* lbar.debtor_id is of type text +* lbar.address_seqnr is of type text +* aa.old_id is of type text + +trial=3D# explain update address set region_id =3D lbar.region_id from=20 + (select debtor_id || '-' || address_seqnr as f_id, region_id from + list_base_regions) as lbar, aux_address aa + where lbar.f_id =3D aa.old_id and address.id =3D aa.id; + + +Since the left side of the join clause is composed out of three concatenate= +d=20 +text-parts resulting in one single piece of type text, I'd expect the plann= +er=20 +to avoid the nested loop. Still: + + QUERY PLAN +---------------------------------------------------------------------------= +----------------------------- + Merge Join (cost=3D1.07..16.07 rows=3D1 width=3D309) + Merge Cond: ("outer".id =3D "inner".id) + -> Nested Loop (cost=3D0.00..149669.38 rows=3D1000 width=3D84) + Join Filter: ((("inner".debitor_id || '-'::text) ||=20 +"inner".address_seqnr) =3D "outer".old_id) + -> Index Scan using aux_address_idx2 on aux_address aa=20=20 +(cost=3D0.00..81.88 rows=3D3989 width=3D16) + -> Seq Scan on list_base_regions (cost=3D0.00..20.00 rows=3D1000= +=20 +width=3D68) + -> Sort (cost=3D1.07..1.08 rows=3D3 width=3D225) + Sort Key: address.id + -> Seq Scan on address (cost=3D0.00..1.05 rows=3D3 width=3D225) + Filter: ((id =3D 1) IS NOT TRUE) +(10 rows) + + + +> Hard to tell exactly what's going on though + +Does this help? + + + + +NB: it seems the data types part of the manual doesn't enlighten me on this= +=20 +subject, any suggestions where to find more input? + + + + + +Regards, + + + + +Frank. + +From pgsql-performance-owner@postgresql.org Tue Dec 3 07:35:14 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E5802475E88 + for ; + Tue, 3 Dec 2002 07:35:12 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id B71AB475CC4 + for ; + Tue, 3 Dec 2002 07:34:01 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18JCFY-0001dO-00 + for ; Tue, 03 Dec 2002 07:34:04 -0500 +Date: Tue, 3 Dec 2002 07:34:04 -0500 +From: Andrew Sullivan +To: pgsql-performance@postgresql.org +Subject: Re: Is there any limitations +Message-ID: <20021203073404.A5868@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + pgsql-performance@postgresql.org +References: <1038887764.4660.49.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: ; + from lili@cs.uoregon.edu on Mon, Dec 02, 2002 at 09:46:43PM -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/14 +X-Sequence-Number: 430 + +On Mon, Dec 02, 2002 at 09:46:43PM -0800, li li wrote: +> +> for the maximum number of tables in a database. + + + +For practical purposes, probably not. + +> to get it separated once the size grows up to a limit. So there +> will be a large amount of tables (having same structure) in a database. Is +> there any potential performance problem with this design? + +It depends on what you're going to do. If the idea is to join across +the tables, it'll probably perform worse than just ahving a large +table. OTOH, if what you're doing is, say, archiving from time to +time, it doesn't seem unreasonable. + +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 Dec 3 08:41:18 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1BC1C475D3B + for ; + Tue, 3 Dec 2002 08:41:17 -0500 (EST) +Received: from nic-nts1.nic.parallel.ltd.uk (parallel1.demon.co.uk + [194.222.145.131]) + by postgresql.org (Postfix) with ESMTP id AEA67475D01 + for ; + Tue, 3 Dec 2002 08:41:15 -0500 (EST) +Received: by nic-nts1.nic.parallel.ltd.uk with Internet Mail Service + (5.5.2656.59) id ; Tue, 3 Dec 2002 13:41:18 -0000 +Message-ID: + +From: Nikk Anderson +To: pgsql-performance@postgresql.org +Subject: Re: Is there any limitations +Date: Tue, 3 Dec 2002 13:41:14 -0000 +MIME-Version: 1.0 +X-Mailer: Internet Mail Service (5.5.2656.59) +Content-Type: multipart/alternative; + boundary="----_=_NextPart_001_01C29AD1.A64901C0" +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/15 +X-Sequence-Number: 431 + +This message is in MIME format. Since your mail reader does not understand +this format, some or all of this message may not be legible. + +------_=_NextPart_001_01C29AD1.A64901C0 +Content-Type: text/plain; + charset="iso-8859-1" + +Hi Li Li, + +> +> I'm thinking about separating a table with up to millions of rows into +> several tables with the same set of columns to speed up some complex +> queries. + +I thought of doing this recently, as queries were taking so long. Instead +of breaking the table up, we clustered the data. This physically moves all +the data by key close to each other on disk (sounds kind of like defragging +a disk). This boosts query responses no end - for example our table has ~ +10 million rows, a query that was taking 45 seconds to return, now takes 7 +seconds. To keep the table tidy, we run the cluster regularly. + +> As the size of the original table is increasing fast, I want +> to get it separated once the size grows up to a limit. So there +> will be a large amount of tables (having same structure) in a +> database. Is +> there any potential performance problem with this design? +> + +I think the problems would mainly be in management, as you would have to +keep track of the new table names, key names, and index names. + +Nikk + +------_=_NextPart_001_01C29AD1.A64901C0 +Content-Type: text/html; + charset="iso-8859-1" +Content-Transfer-Encoding: quoted-printable + + + + + + +RE: [PERFORM] Is there any limitations + + + +

Hi Li Li, +

+ +

> +
> I'm thinking about separating a table with up to mi= +llions of rows into +
> several tables with the same set of columns to spee= +d up some complex +
> queries. +

+ +

I thought of doing this recently, as queries were taking = +so long.  Instead of breaking the table up, we clustered the data.&nbs= +p; This physically moves all the data by key close to each other on disk (s= +ounds kind of like defragging a disk).  This boosts query responses no= + end - for example our table has ~ 10 million rows, a query that was taking= + 45 seconds to return, now takes 7 seconds.  To keep the table tidy, w= +e run the cluster regularly.

+ +

> As the size of the original table is increasing fast= +, I want +
> to get it separated once the size grows up to a lim= +it. So there +
> will be a large amount of tables (having same struc= +ture) in a +
> database. Is +
> there any potential performance problem with this d= +esign? +
> +

+ +

I think the problems would mainly be in management, as yo= +u would have to keep track of the new table names, key names, and index nam= +es. 

+ +

Nikk +

+ + + +------_=_NextPart_001_01C29AD1.A64901C0-- + +From pgsql-performance-owner@postgresql.org Tue Dec 3 09:35:21 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0B4E5475E77 + for ; + Tue, 3 Dec 2002 09:35:20 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 5BC2C475D99 + for ; + Tue, 3 Dec 2002 09:35:19 -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 gB3EZGpd023157; + Tue, 3 Dec 2002 09:35:16 -0500 (EST) +To: "Frank van Vugt" +Cc: Postgresql performance +Subject: Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with + UNION +In-reply-to: <200212031038.10860.ftm.van.vugt@foxi.nl> +References: <200212030051.03635.ftm.van.vugt@foxi.nl> + <20527.1038895184@sss.pgh.pa.us> + <200212031038.10860.ftm.van.vugt@foxi.nl> +Comments: In-reply-to "Frank van Vugt" + message dated "Tue, 03 Dec 2002 10:38:10 +0100" +Date: Tue, 03 Dec 2002 09:35:16 -0500 +Message-ID: <23156.1038926116@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/16 +X-Sequence-Number: 432 + +"Frank van Vugt" writes: +> Since the left side of the join clause is composed out of three concatenated +> text-parts resulting in one single piece of type text, I'd expect the +> planner to avoid the nested loop. + +Probably not, since the first thing it does is to flatten the +sub-select, leaving it with a concatenation expression in the +WHERE-clause. (I was too sleepy last night to realize that you +were comparing a concatenation to old_id, rather than making two +separate comparisons :-() + +We really need to fix the planner to be able to do merge/hash on +"arbitrary expression = arbitrary expression", not only "Var = Var". +IIRC, this is doable in principle, but there are a few routines that +would need to be improved. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Dec 3 10:23:39 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2747847653B + for ; + Tue, 3 Dec 2002 10:23:35 -0500 (EST) +Received: from gatefox.foxi.nl (a194-109-246-192.adsl.xs4all.nl + [194.109.246.192]) + by postgresql.org (Postfix) with ESMTP id 14372475E77 + for ; + Tue, 3 Dec 2002 10:22:11 -0500 (EST) +Received: from techfox (techfox.foxi [192.168.0.79]) + by gatefox.foxi.nl (8.10.2/8.10.2) with ESMTP id gB3FMCJ14631; + Tue, 3 Dec 2002 16:22:12 +0100 +Content-Type: text/plain; + charset="iso-8859-15" +From: Frank van Vugt +Organization: Foxi Consultants in Technology +To: Tom Lane +Subject: Re: v7.2.3 versus v7.3 -> huge performance penalty for JOIN with + UNION +Date: Tue, 3 Dec 2002 16:23:51 +0100 +User-Agent: KMail/1.4.3 +References: <200212030051.03635.ftm.van.vugt@foxi.nl> + <200212031038.10860.ftm.van.vugt@foxi.nl> + <23156.1038926116@sss.pgh.pa.us> +In-Reply-To: <23156.1038926116@sss.pgh.pa.us> +Cc: Postgresql performance +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212031623.51513.ftm.van.vugt@foxi.nl> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/17 +X-Sequence-Number: 433 + +> Probably not, since the first thing it does is to flatten the +> sub-select, leaving it with a concatenation expression in the +> WHERE-clause.=20 + +Ah, I see. + +So, I'll just split this thingy into two seperate queries, starting with=20 +creating a temp table containing the straight subselect results. + +> We really need to fix the planner to be able to do merge/hash on +> "arbitrary expression =3D arbitrary expression", not only "Var =3D Var". + +I can get around it, so I'm not complaining ;-) + + +Tom, thanks a *lot* for the prompt responses !! + + + +Best, + + + + + +Frank. + + +From pgsql-performance-owner@postgresql.org Tue Dec 3 14:12:01 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BB36C475E45 + for ; + Tue, 3 Dec 2002 14:12:00 -0500 (EST) +Received: from alpha.cpons.com (unknown [209.235.53.98]) + by postgresql.org (Postfix) with ESMTP id 4B09F47669C + for ; + Tue, 3 Dec 2002 14:11:23 -0500 (EST) +Received: from bgunter2 (localhost.localdomain [127.0.0.1]) + by alpha.cpons.com (8.12.5/8.12.5) with SMTP id gB3JBXXr012485 + for ; Tue, 3 Dec 2002 14:11:33 -0500 +Message-ID: <006701c29aff$d10048f0$8c3c3d0a@bgunter2> +From: "Ben Gunter" +To: +Subject: v7.3 planner and user-defined functions +Date: Tue, 3 Dec 2002 14:11:43 -0500 +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: 200212/18 +X-Sequence-Number: 434 + +I am having some problems with user-defined functions in version 7.3. The +planner seems to refuse to use an index that I have created when I define an +SQL function that should take advantage of it. The thing that is driving me +nuts is that if I take the SQL from the function definition and run it +exactly as it is, replacing the parameters with real values, then it does +use the index and performs beautifully. I never saw this problem until I +upgraded from 7.2.3 to 7.3. + +At the bottom of this email, I have included a psql test input file and the +results. I have an index on zip_locs(dist1,dist2,dist3,dist4). I'm joining +a table of about 350,000 rows (mytable) against another table of about +42,000 rows (zip_locs) on a ZIP code. The ZIP fields in both tables are +indexed as well. The functions zip_dist[1234](varchar) return the +respective dist[1234] value for the given ZIP code. The zip_lat(varchar) +and zip_lng(varchar) functions return the latitude and longitude for the +given ZIP code, respectively. All these functions are immutable so they +have virtually no effect on the speed of the query. The point of the query +is to get a count of records in mytable that are within a certain distance +of a given ZIP code. + +When I do the explicit SELECT, it uses the aforementioned index and then +filters on the result of the earth_distance(real,real,real,real) function. +When I run the radiuscount(varchar,real) function, it apparently does a +sequential scan instead of using the index. + +I have tried rewriting this query every way I know how, but nothing seems to +work. Can anybody help me with this? + +Here is the psql input file I'm using to demonstrate: +******************* +CREATE OR REPLACE FUNCTION radiuscount(varchar, real) RETURNS bigint AS +' +SELECT COUNT(*) +FROM mytable JOIN zip_locs ON zip = zip_code +WHERE + dist1 BETWEEN zip_dist1($1) - $2::real AND zip_dist1($1) + +$2::real + AND dist2 BETWEEN zip_dist2($1) - $2::real AND zip_dist2($1) + +$2::real + AND dist3 BETWEEN zip_dist3($1) - $2::real AND zip_dist3($1) + +$2::real + AND dist4 BETWEEN zip_dist4($1) - $2::real AND zip_dist4($1) + +$2::real + AND earth_distance(zip_lat($1), zip_lng($1), lat, lng) < $2::real +' LANGUAGE 'SQL' +STABLE +RETURNS NULL ON NULL INPUT +; + +\timing +\a +\t + +\echo +\echo 'NOT using the function' +SELECT COUNT(*) AS radiuscount +FROM mytable JOIN zip_locs ON zip = zip_code +WHERE + dist1 BETWEEN zip_dist1('30096') - 20::real AND +zip_dist1('30096') + 20::real + AND dist2 BETWEEN zip_dist2('30096') - 20::real AND +zip_dist2('30096') + 20::real + AND dist3 BETWEEN zip_dist3('30096') - 20::real AND +zip_dist3('30096') + 20::real + AND dist4 BETWEEN zip_dist4('30096') - 20::real AND +zip_dist4('30096') + 20::real + AND earth_distance(zip_lat('30096'), zip_lng('30096'), lat, lng) < +20::real +; + +\echo +\echo 'Using the function' +select radiuscount('30096',20); +******************* + +And here is the output: +******************* +CREATE FUNCTION +Timing is on. +Output format is unaligned. +Showing only tuples. + +NOT using the function +2775 +Time: 584.02 ms + +Using the function +2775 +Time: 11693.56 ms +******************* + + + +From pgsql-performance-owner@postgresql.org Tue Dec 3 15:03:07 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B29D8476D08 + for ; + Tue, 3 Dec 2002 15:03:06 -0500 (EST) +Received: from cs.uoregon.edu (vitalstatistix.cs.uoregon.edu [128.223.4.19]) + by postgresql.org (Postfix) with ESMTP id 231D6476998 + for ; + Tue, 3 Dec 2002 14:49:05 -0500 (EST) +Received: from ix.cs.uoregon.edu (ix.cs.uoregon.edu [128.223.4.21]) + by cs.uoregon.edu (8.11.0/8.11.0) with ESMTP id gB3Jn3j01029; + Tue, 3 Dec 2002 11:49:04 -0800 (PST) +Date: Tue, 3 Dec 2002 11:49:03 -0800 (PST) +From: li li +To: Andrew Sullivan +Cc: +Subject: Re: Is there any limitations +In-Reply-To: <20021203073404.A5868@mail.libertyrms.com> +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/19 +X-Sequence-Number: 435 + + +> +> It depends on what you're going to do. If the idea is to join across +> the tables, it'll probably perform worse than just ahving a large +> table. OTOH, if what you're doing is, say, archiving from time to +> time, it doesn't seem unreasonable. +> +The purpose for this design is to avoid record lookup in a huge table. +I expect to see the query results in, say, one minute, by searching a much +smaller table (not join across multiple tables). + +Thanks and regards. + +Li Li + + +From pgsql-performance-owner@postgresql.org Tue Dec 3 15:26:23 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 139E7476959 + for ; + Tue, 3 Dec 2002 15:26:22 -0500 (EST) +Received: from cs.uoregon.edu (vitalstatistix.cs.uoregon.edu [128.223.4.19]) + by postgresql.org (Postfix) with ESMTP id 90034476F14 + for ; + Tue, 3 Dec 2002 15:06:14 -0500 (EST) +Received: from ix.cs.uoregon.edu (ix.cs.uoregon.edu [128.223.4.21]) + by cs.uoregon.edu (8.11.0/8.11.0) with ESMTP id gB3K69j03038; + Tue, 3 Dec 2002 12:06:10 -0800 (PST) +Date: Tue, 3 Dec 2002 12:06:09 -0800 (PST) +From: li li +To: Nikk Anderson +Cc: +Subject: Re: Is there any limitations +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: 200212/20 +X-Sequence-Number: 436 + +Hi Nikk, + +> I thought of doing this recently, as queries were taking so long. Instead +> of breaking the table up, we clustered the data. This physically moves all +> the data by key close to each other on disk (sounds kind of like defragging +> a disk). This boosts query responses no end - for example our table has ~ +> 10 million rows, a query that was taking 45 seconds to return, now takes 7 +> seconds. To keep the table tidy, we run the cluster regularly. +> +I've clustered the data with a non-key attribute. Now the query time is +about couple of minutes, but I expect less than one minute. Is there any trick +in using cluster? I found that the primary key disappeared after +clustering. Or it's better to cluster with primary key? My primary key is +a composite. I picked one attribute as cluster key. + +> > As the size of the original table is increasing fast, I want +> > to get it separated once the size grows up to a limit. So there +> > will be a large amount of tables (having same structure) in a +> > database. Is +> > there any potential performance problem with this design? +> > +> +> I think the problems would mainly be in management, as you would have to +> keep track of the new table names, key names, and index names. +> +You are right. I have to keep track of these table names. +However, I don't see any necessity for key names or index names. Because, +as I metioned above, all these tables have exactly same structure. + +Thanks for quick response. + +Li Li + + +From pgsql-performance-owner@postgresql.org Wed Dec 4 04:30:00 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 942C0475FB5 + for ; + Wed, 4 Dec 2002 04:29:56 -0500 (EST) +Received: from anchor-post-30.mail.demon.net (anchor-post-30.mail.demon.net + [194.217.242.88]) + by postgresql.org (Postfix) with ESMTP id D77DC475EEE + for ; + Wed, 4 Dec 2002 04:29:54 -0500 (EST) +Received: from mwynhau.demon.co.uk ([193.237.186.96] + helo=mainbox.archonet.com) + by anchor-post-30.mail.demon.net with esmtp (Exim 3.35 #1) + id 18JVqt-000A2o-0U; Wed, 04 Dec 2002 09:29:55 +0000 +Received: from localhost (localhost.localdomain [127.0.0.1]) + by mainbox.archonet.com (Postfix) with ESMTP + id A2E1F1685A; Wed, 4 Dec 2002 09:29:54 +0000 (GMT) +Received: from client.archonet.com (client.archonet.com [192.168.1.16]) + by mainbox.archonet.com (Postfix) with ESMTP + id F058A16858; Wed, 4 Dec 2002 09:29:53 +0000 (GMT) +Content-Type: text/plain; + charset="iso-8859-1" +From: Richard Huxton +To: li li +Subject: Re: Is there any limitations +Date: Wed, 4 Dec 2002 09:29:53 +0000 +User-Agent: KMail/1.4.3 +Cc: +References: +In-Reply-To: +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212040929.53514.richardh@archonet.com> +X-Virus-Scanned: by AMaViS snapshot-20020531 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/21 +X-Sequence-Number: 437 + +On Tuesday 03 Dec 2002 7:49 pm, li li wrote: +> > It depends on what you're going to do. If the idea is to join across +> > the tables, it'll probably perform worse than just ahving a large +> > table. OTOH, if what you're doing is, say, archiving from time to +> > time, it doesn't seem unreasonable. +> +> The purpose for this design is to avoid record lookup in a huge table. +> I expect to see the query results in, say, one minute, by searching a much +> smaller table (not join across multiple tables). +> +> Thanks and regards. + +If you only want *most* queries to finish in one minute - I've used two tab= +les=20 +in the past. One for recent info (which is what most of my users wanted) an= +d=20 +one for older info (which only got accessed rarely). You're only union-ing= +=20 +two tables then and you can cluster the older table as mentioned elsewhere. +--=20 + Richard Huxton + Archonet Ltd + +From pgsql-performance-owner@postgresql.org Wed Dec 4 05:29:24 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1A94C475D00 + for ; + Wed, 4 Dec 2002 05:29:23 -0500 (EST) +Received: from localhost.localdomain (sein.itera.ee [194.126.109.126]) + by postgresql.org (Postfix) with ESMTP id 0AAAD4759AF + for ; + Wed, 4 Dec 2002 05:29:22 -0500 (EST) +Received: (from hannu@localhost) + by localhost.localdomain (8.11.6/8.11.6) id gB4CNgx27746; + Wed, 4 Dec 2002 12:23:42 GMT +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: Is there any limitations +From: Hannu Krosing +To: Richard Huxton +Cc: li li , pgsql-performance@postgresql.org +In-Reply-To: <200212040929.53514.richardh@archonet.com> +References: + <200212040929.53514.richardh@archonet.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039004621.26887.20.camel@huli> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 04 Dec 2002 12:23:41 +0000 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/22 +X-Sequence-Number: 438 + +On Wed, 2002-12-04 at 09:29, Richard Huxton wrote: +> On Tuesday 03 Dec 2002 7:49 pm, li li wrote: +> > > It depends on what you're going to do. If the idea is to join across +> > > the tables, it'll probably perform worse than just ahving a large +> > > table. OTOH, if what you're doing is, say, archiving from time to +> > > time, it doesn't seem unreasonable. +> > +> > The purpose for this design is to avoid record lookup in a huge table. +> > I expect to see the query results in, say, one minute, by searching a much +> > smaller table (not join across multiple tables). +> > +> > Thanks and regards. +> +> If you only want *most* queries to finish in one minute - I've used two tables +> in the past. One for recent info (which is what most of my users wanted) and +> one for older info (which only got accessed rarely). You're only union-ing +> two tables then and you can cluster the older table as mentioned elsewhere. + +ANother approach could be to have index on timestamp field (which should +be naturally clustered) and search in recent data only. + +If the problem is simply too much data returned, you could use LIMIT. + +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Wed Dec 4 15:36:39 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E68F34769CE + for ; + Wed, 4 Dec 2002 15:36:37 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id 567AC475FB8 + for ; + Wed, 4 Dec 2002 15:31:10 -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 gB4KUKOm027969; + Wed, 4 Dec 2002 13:30:35 -0700 (MST) +Date: Wed, 4 Dec 2002 13:28:46 -0700 (MST) +From: "scott.marlowe" +To: eric soroos +Cc: +Subject: Re: Low Budget Performance, Part 2 +In-Reply-To: <30995191.1173642930@[4.42.179.151]> +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: 200212/23 +X-Sequence-Number: 439 + +On Thu, 28 Nov 2002, eric soroos wrote: + +> The rotational speed difference is 40% (10k/7.2k), and the TPS +> difference is about 60% (50/30 or 40/25) + +I would suggest that areal density / xfer rate off the platters is the +REAL issue, not rotational speed. Rotational speed really only has a +small effect on the wait time for the heads to get in position, whereas +xfer rate off the platters is much more important. + +My older 7200RPM 2Gig and 4Gig UW SCSI drives are no match for my more +modern 40 Gig 5400 RPM IDE drive, which has much higher areal density and +xfer rate off the platters. While it may not spin as fast, the bits / +cm2 are MUCH higher on that drive, and I can get around 15 megs a second +off of it with bonnie++. The older 4 gig UW drives can hardly break 5 +Megs a second xfer rate. + +Of course, on the drives you're testing, it is quite likely that the xfer +rate on the 10k rpm drives are noticeably higher than the xfer rate on +the 7200 rpm IDE drives, so that is likely the reason for the better +performance. + + +From pgsql-performance-owner@postgresql.org Wed Dec 4 19:30:32 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8304D475FD3 + for ; + Wed, 4 Dec 2002 19:30:28 -0500 (EST) +Received: from pd3mo1so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net + [24.71.223.10]) by postgresql.org (Postfix) with ESMTP id C3D5D4763C9 + for ; + Wed, 4 Dec 2002 19:30:24 -0500 (EST) +Received: from pd4mr2so.prod.shaw.ca + (pd4mr2so-qfe3.prod.shaw.ca [10.0.141.213]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H6M00BQZEJK0F@l-daemon> for + pgsql-performance@postgresql.org; + Wed, 04 Dec 2002 17:26:08 -0700 (MST) +Received: from pn2ml6so.prod.shaw.ca + (pn2ml6so-qfe0.prod.shaw.ca [10.0.121.150]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H6M00A7VEJKQE@l-daemon> for + pgsql-performance@postgresql.org; + Wed, 04 Dec 2002 17:26:08 -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 <0H6M000G0EJJNI@l-daemon> for + pgsql-performance@postgresql.org; + Wed, 04 Dec 2002 17:26:08 -0700 (MST) +Date: Wed, 04 Dec 2002 16:26:14 -0800 +From: Vernon Wu +Subject: Is a better way to have the same result of this query? +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: 200212/24 +X-Sequence-Number: 440 + + +I have the following query: + +SELECT p.userid, p.year, a.country, a.province, a.city +FROM profile p, account a +WHERE p.userid=a.userid AND + (p.year BETWEEN 1961 AND 1976) AND + a.country='CA' AND + a.province='BC' AND + p.gender='f' AND + p.userid NOT IN (SELECT b.userid FROM block b WHERE b.personid='Joe') AND + block.userid IS NOT NULL AND + p.userid IN + (SELECT f.userid FROM preference f, profile p1 WHERE p1.userid='Joe' AND 2002-p1.year BETWEEN + f.minage AND f.maxage) + +In plain English, it is that + +Joe finds females between the ages in the location who is not in the block table, while Joe's age is between what they +prefer. + +The query plan is the followings: + +Nested Loop (cost=0.00..127.12 rows=995 width=894) + -> Nested Loop (cost=0.00..97.17 rows=1 width=894) + -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) + -> Index Scan using pk_profile on profile p (cost=0.00..72.16 rows=1 width=605) + SubPlan + -> Materialize (cost=22.50..22.50 rows=5 width=55) + -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55 +) + -> Materialize (cost=44.82..44.82 rows=111 width=89) + -> Nested Loop (cost=0.00..44.82 rows=111 width=89) + -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) + -> Seq Scan on preference f (cost=0.00..20.00 rows=1000 width=77) + -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) + +It seems take quite long to run this query. How to optimise the query? + +Thanks for your input. + +Vernon + + + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 00:27:58 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C753B475EAE + for ; + Thu, 5 Dec 2002 00:27:56 -0500 (EST) +Received: from lakemtao04.cox.net (lakemtao04.cox.net [68.1.17.241]) + by postgresql.org (Postfix) with ESMTP id 7F179475C98 + for ; + Thu, 5 Dec 2002 00:26:46 -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 <20021205052651.QJQQ1248.lakemtao04.cox.net@[192.168.1.1]> + for ; + Thu, 5 Dec 2002 00:26:51 -0500 +Subject: Re: Is a better way to have the same result of this +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: +References: +Content-Type: text/plain +Organization: +Message-Id: <1039066008.11433.3.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 04 Dec 2002 23:26:48 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/25 +X-Sequence-Number: 441 + +On Wed, 2002-12-04 at 18:26, Vernon Wu wrote: +> I have the following query: +> +> SELECT p.userid, p.year, a.country, a.province, a.city +> FROM profile p, account a +> WHERE p.userid=a.userid AND +> (p.year BETWEEN 1961 AND 1976) AND +> a.country='CA' AND +> a.province='BC' AND +> p.gender='f' AND +> p.userid NOT IN (SELECT b.userid FROM block b WHERE b.personid='Joe') AND +> block.userid IS NOT NULL AND +> p.userid IN +> (SELECT f.userid FROM preference f, profile p1 WHERE p1.userid='Joe' AND 2002-p1.year BETWEEN +> f.minage AND f.maxage) +> +> In plain English, it is that +> +> Joe finds females between the ages in the location who is not in the block table, while Joe's age is between what they +> prefer. +> +> The query plan is the followings: +> +> Nested Loop (cost=0.00..127.12 rows=995 width=894) +> -> Nested Loop (cost=0.00..97.17 rows=1 width=894) +> -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) +> -> Index Scan using pk_profile on profile p (cost=0.00..72.16 rows=1 width=605) +> SubPlan +> -> Materialize (cost=22.50..22.50 rows=5 width=55) +> -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55 +> ) +> -> Materialize (cost=44.82..44.82 rows=111 width=89) +> -> Nested Loop (cost=0.00..44.82 rows=111 width=89) +> -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) +> -> Seq Scan on preference f (cost=0.00..20.00 rows=1000 width=77) +> -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) +> +> It seems take quite long to run this query. How to optimise the query? +> +> Thanks for your input. +> +> Vernon + +What kind of indexes, if any, do you have on, and what is the +cardinality of account, block and preference? + +What version of Postgres are you using? + +How much shared memory and buffers are you using? + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "they love our milk and honey, but preach about another | +| way of living" | +| Merle Haggard, "The Fighting Side Of Me" | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 04:51:10 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6CB1B475F28 + for ; + Thu, 5 Dec 2002 04:51:09 -0500 (EST) +Received: from mediaexch01.mediaburst.co.uk (unknown [213.130.128.235]) + by postgresql.org (Postfix) with ESMTP id 94974475EAE + for ; + Thu, 5 Dec 2002 04:51:08 -0500 (EST) +content-class: urn:content-classes:message +Subject: ORDER BY ... LIMIT.. performance +MIME-Version: 1.0 +Content-Type: text/plain; + charset="us-ascii" +Content-Transfer-Encoding: quoted-printable +Date: Thu, 5 Dec 2002 09:51:09 -0000 +X-MimeOLE: Produced By Microsoft Exchange V6.0.4712.0 +Message-ID: + <94B61ED0D8770A4A98A3DBD72DBBA1F821A80A@mediaexch01.mediaburst.co.uk> +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: ORDER BY ... LIMIT.. performance +Thread-Index: AcKcQ9WzyLHpZ4aeQwGhQ6hQL3I1Pg== +From: "john cartmell" +To: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/26 +X-Sequence-Number: 442 + +I am not sure whether this is a know problem but we discovered this the +other day. +We are using PostgreSQL 7.2.1 on Redhat 7.3. + +The table has about over a million rows (~1.4). + +The query concerned is of the form + +SELECT * +FROM tblCompany +WHERE lower(companyname) like 'company%' +ORDER BY companyname +LIMIT 20,0 + +There is a functional index lower(companyname) for the like clause. + +Without the LIMIT clause the query takes approximately 3-5 seconds to +return. +If total number of rows returned without the LIMIT clause is greater +than 20 records, then the above query also takes th same amount of time. +But if the the total number of rows is 20 or less then the time taken +for the above query to return goes up to 20-30 seconds. Has anyone else +come across this. We have managed to get round it by performing a count +first and only performing the LIMIT if there are enough rows but surely +the query should be able to do this itself! + +John Cartmell + +From pgsql-performance-owner@postgresql.org Thu Dec 5 05:01:20 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CA3B8475C98 + for ; + Thu, 5 Dec 2002 05:01:17 -0500 (EST) +Received: from ns1.tudelft.nl (ns1.tudelft.nl [130.161.180.1]) + by postgresql.org (Postfix) with ESMTP id 31E68475BC3 + for ; + Thu, 5 Dec 2002 05:01:17 -0500 (EST) +Received: from CONVERSION-DAEMON.mailhost2.tudelft.nl by mailhost2.tudelft.nl + (PMDF V6.1-1 #40925) id <0H6N00601564TK@mailhost2.tudelft.nl> for + pgsql-performance@postgresql.org; Thu, 05 Dec 2002 11:01:18 +0100 (MET) +Received: from listserv.tudelft.nl (listserv.tudelft.nl [130.161.180.33]) + by mailhost2.tudelft.nl (PMDF V6.1-1 #40925) + with ESMTP id <0H6N0027C564P8@mailhost2.tudelft.nl>; Thu, + 05 Dec 2002 11:01:16 +0100 (MET) +Received: from oli.tudelft.nl (oli244.rolahola.tudelft.nl [130.161.67.244]) + by listserv.tudelft.nl (8.12.5/8.12.5) with ESMTP id gB5A1FFx012879; + Thu, 05 Dec 2002 11:01:16 +0100 (MET) +Date: Thu, 05 Dec 2002 11:01:15 +0100 +From: Jochem van Dieten +Subject: Re: Is a better way to have the same result of this query? +In-reply-to: +To: vernonw@gatewaytech.com +Cc: pgsql-performance@postgresql.org +Message-id: <3DEF23EB.1060603@oli.tudelft.nl> +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 (Windows; U; WinNT4.0; en-US; rv:1.2) Gecko/20021126 +References: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/27 +X-Sequence-Number: 443 + +Vernon Wu wrote: +> +> SELECT p.userid, p.year, a.country, a.province, a.city +> FROM profile p, account a +> WHERE p.userid=a.userid AND +> (p.year BETWEEN 1961 AND 1976) AND +> a.country='CA' AND +> a.province='BC' AND +> p.gender='f' AND +> p.userid NOT IN (SELECT b.userid FROM block b WHERE b.personid='Joe') AND +> block.userid IS NOT NULL AND +> p.userid IN +> (SELECT f.userid FROM preference f, profile p1 WHERE p1.userid='Joe' AND 2002-p1.year BETWEEN +> f.minage AND f.maxage) + +You might want to flatten this into more joins and less subqueries, +especially since you are using IN which is not very optimized: + +SELECT p.userid, p.year, a.country, a.province, a.city +FROM profile p, account a, preference f, profile p1 +WHERE + f.userid = p.userid AND + p.userid=a.userid AND + (p.year BETWEEN 1961 AND 1976) AND + a.country='CA' AND + a.province='BC' AND + p.gender='f' AND + p.userid NOT IN (SELECT b.userid FROM block b WHERE b.personid='Joe') AND + block.userid IS NOT NULL AND + p1.userid='Joe' AND + 2002-p1.year BETWEEN f.minage AND f.maxage + +Also, I am not sure about the NOT IN. If you can rewrite it using EXISTS +try that, it might be faster. + + +> Nested Loop (cost=0.00..127.12 rows=995 width=894) +> -> Nested Loop (cost=0.00..97.17 rows=1 width=894) +> -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) +> -> Index Scan using pk_profile on profile p (cost=0.00..72.16 rows=1 width=605) +> SubPlan +> -> Materialize (cost=22.50..22.50 rows=5 width=55) +> -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55 +> ) +> -> Materialize (cost=44.82..44.82 rows=111 width=89) +> -> Nested Loop (cost=0.00..44.82 rows=111 width=89) +> -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) +> -> Seq Scan on preference f (cost=0.00..20.00 rows=1000 width=77) + +rows=1000 usually indicates you didn't vacuum analyze. Did you? + +> -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) + +And to add to Vernons questions: if you are using PostgreSQL 7.2 or +later, please send us the EXPLAIN ANALYZE output. + +Jochem + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 11:30:47 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 946FD476875 + for ; + Thu, 5 Dec 2002 11:30:45 -0500 (EST) +Received: from cpcolosmtp (unknown [208.252.194.251]) + by postgresql.org (Postfix) with SMTP id F1D92476861 + for ; + Thu, 5 Dec 2002 11:30:26 -0500 (EST) +Received: FROM mail-west.gensler.com BY cpcolosmtp ; + Thu Dec 05 08:21:51 2002 -0800 +Received: from cpg2wsb (192.168.100.30) + by mail-west.gensler.com (FirstClass Mail Server v6.1) with SMTP + (Sender: eric_theis@gensler.com) + transient id 675; Thu, 05 Dec 2002 08:33:13 -0800 +From: "Eric Theis" +To: +Subject: Index question with LIKE keyword +Date: Thu, 5 Dec 2002 08:34:14 -0800 +Message-ID: +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: 7bit +X-Priority: 3 (Normal) +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2911.0) +Importance: Normal +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/28 +X-Sequence-Number: 444 + +I have a question about some strange behavior on what should be a rather +easy issue. +I am not getting the query plan that I expect given the query and the +indexes. + +I have a table with the following structure: +CREATE TABLE tblCompany( + intCmpID serial NOT NULL, + vchCmpName varchar(60) NOT NULL, + vchCmpAltName varchar(100) NULL, + vchCmpPrevName varchar(60) NULL, + intCmpParentID int NULL, + intCmpOwnerEmpID int NOT NULL, + dateCmpMaintained datetime NOT NULL, + chrCmpStatus char(1) NOT NULL, + intModifiedBy int NOT NULL, + dateModifiedOn datetime NOT NULL, + CONSTRAINT pkCompany PRIMARY KEY (intCmpID) +) ; + +It has the following index: +CREATE INDEX idxCompany1 ON tblCompany(vchCmpName); + +When I run the following query in Postgres, I get the results I expect: +CRMDB=> explain select * from tblCompany where vchCmpName = 'Gensler'; +NOTICE: QUERY PLAN: + +Index Scan using idxcompany1 on tblcompany (cost=0.00..5.21 rows=1 +width=212) + +EXPLAIN + + +This work under both Windows and Linux. + +When I run the following query under Windows, I get what I expect: +CRMDB=> explain select * from tblCompany where vchcmpname like 'Gensler%'; +NOTICE: QUERY PLAN: + +Index Scan using idxcompany1 on tblcompany (cost=0.00..17.07 rows=1 +width=201) + +EXPLAIN + +However, when I run the same query under Linux, I get this: +CRMDB=> explain select * from tblCompany where vchCmpName like 'Gensler%'; +NOTICE: QUERY PLAN: + +Seq Scan on tblcompany (cost=100000000.00..100000002.01 rows=1 width=212) + +EXPLAIN + +I really don't understand why this is happening, but I am hoping that +someone on this list has an idea. The versions of Postgres that I am using +are Windows 7.2.2 and Linux 7.2.1 and 7.2.2. The Windows version is the +compiled version that comes with Cygwin and the Linux versions are the RPMs +that come with Redhat 7.3, Mandrake 9.0 and the Redhat 7.3 RPM from the +Postgres site. + +If anyone has an ideas suggestions I would really appreciate it. + +TIA +Eric + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 11:48:30 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BEA7E4761DB + for ; + Thu, 5 Dec 2002 11:48:28 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 8CE41476800 + for ; + Thu, 5 Dec 2002 11:47:24 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id B6332D600; Thu, 5 Dec 2002 08:47:29 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id ABDEE5C02; Thu, 5 Dec 2002 08:47:29 -0800 (PST) +Date: Thu, 5 Dec 2002 08:47:29 -0800 (PST) +From: Stephan Szabo +To: Eric Theis +Cc: +Subject: Re: Index question with LIKE keyword +In-Reply-To: +Message-ID: <20021205084537.A2049-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/29 +X-Sequence-Number: 445 + +On Thu, 5 Dec 2002, Eric Theis wrote: + +> This work under both Windows and Linux. +> +> When I run the following query under Windows, I get what I expect: +> CRMDB=> explain select * from tblCompany where vchcmpname like 'Gensler%'; +> NOTICE: QUERY PLAN: +> +> Index Scan using idxcompany1 on tblcompany (cost=0.00..17.07 rows=1 +> width=201) +> +> EXPLAIN +> +> However, when I run the same query under Linux, I get this: +> CRMDB=> explain select * from tblCompany where vchCmpName like 'Gensler%'; +> NOTICE: QUERY PLAN: +> +> Seq Scan on tblcompany (cost=100000000.00..100000002.01 rows=1 width=212) +> +> EXPLAIN +> +> I really don't understand why this is happening, but I am hoping that +> someone on this list has an idea. The versions of Postgres that I am using +> are Windows 7.2.2 and Linux 7.2.1 and 7.2.2. The Windows version is the +> compiled version that comes with Cygwin and the Linux versions are the RPMs +> that come with Redhat 7.3, Mandrake 9.0 and the Redhat 7.3 RPM from the +> Postgres site. +> +> If anyone has an ideas suggestions I would really appreciate it. + +The linux box is probably not running in "C" locale (or at least initdb +wasn't run in "C" locale). The optimization for using indexes on like +currently only works in that locale (because there are issues in some/many +other locales that makes the transformation invalid). There's been talk +about this issue on (I think) -general (or if not there then -hackers) +recently. + + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 13:45:24 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8CFE34762AB + for ; + Thu, 5 Dec 2002 13:45:22 -0500 (EST) +Received: from pd3mo2so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net + [24.71.223.10]) by postgresql.org (Postfix) with ESMTP id C28404761DD + for ; + Thu, 5 Dec 2002 13:45:19 -0500 (EST) +Received: from pd6mr4so.prod.shaw.ca + (pd6mr4so-qfe3.prod.shaw.ca [10.0.141.219]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H6N00DFXTFFNS@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 11:45:15 -0700 (MST) +Received: from pn2ml10so.prod.shaw.ca + (pn2ml10so-qfe0.prod.shaw.ca [10.0.121.80]) + by l-daemon (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 + 2002)) with ESMTP id <0H6N004DTTFGJ6@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 11:45:16 -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 <0H6N008OLTFE04@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 11:45:16 -0700 (MST) +Date: Thu, 05 Dec 2002 10:44:34 -0800 +From: Vernon Wu +Subject: Re: Is a better way to have the same result of this query? +In-reply-to: <3DEF23EB.1060603@oli.tudelft.nl> +To: Jochem van Dieten +Cc: 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=us-ascii +Content-transfer-encoding: 7BIT +X-Priority: 3 (Normal) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/30 +X-Sequence-Number: 446 + +Jochem, + +Thanks for your suggestion/information. + +The followings are the analyise outcomes after I did some modifications with the query. My finding is that the new query +does improve the performance according to the plan. The actual time is reversed might due to the fact the test data is +very small (the machine is a very old one by the way). The userid is the key for all tables and the gender is indexed. Do I +also index the country and province to improve the preformance? + +The modified query with the suggested flatting query. + +Nested Loop (cost=0.00..91.97 rows=995 width=445) (actual time=1.00..3.00 rows=2 loops=1) + -> Nested Loop (cost=0.00..62.02 rows=1 width=445) (actual time=1.00..3.00 rows=2 loops=1) + -> Nested Loop (cost=0.00..34.68 rows=1 width=378) (actual time=1.00..3.00 rows=3 loops=1) + -> Nested Loop (cost=0.00..29.84 rows=1 width=366) (actual time=1.00..3.00 rows=3 loops=1) + -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) (actual time=0.00..0.00 rows=3 loops=1) + -> Index Scan using pk_preference on preference f (cost=0.00..4.82 rows=1 width=77) (actual time= +0.67..1.00 rows=1 loops=3) + -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) (actual time=0.00..0.00 rows= +1 loops=3) + -> Index Scan using pk_profile on profile p (cost=0.00..27.33 rows=1 width=67) (actual time=0.00..0.00 rows=1 +loops=3) + SubPlan + -> Materialize (cost=22.50..22.50 rows=5 width=55) (actual time=0.00..0.00 rows=0 loops=2) + -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55) (actual time=0.00..0.00 rows=0 loops=1) + -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) (actual time=0.00..0.00 rows=1 loops=2) +Total runtime: 5.00 msec + +After replacing "p.userid NOT IN" with "NOT EXISTS": + +Result (cost=0.00..61.56 rows=995 width=445) (actual time=3.00..4.00 rows=2 loops=1) + InitPlan + -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55) (actual time=0.00..0.00 rows=0 loops=1) + -> Nested Loop (cost=0.00..61.56 rows=995 width=445) (actual time=3.00..4.00 rows=2 loops=1) + -> Nested Loop (cost=0.00..31.61 rows=1 width=445) (actual time=3.00..4.00 rows=2 loops=1) + -> Nested Loop (cost=0.00..26.77 rows=1 width=433) (actual time=2.00..3.00 rows=2 loops=1) + -> Nested Loop (cost=0.00..21.93 rows=1 width=356) (actual time=2.00..2.00 rows=2 loops=1) + -> Index Scan using profile_sex_idx on profile p (cost=0.00..17.09 rows=1 width=67) (actual time= +1.00..1.00 rows=2 loops=1) + -> Index Scan using pk_account on account a (cost=0.00..4.83 rows=1 width=289) (actual time= +0.50..0.50 rows=1 loops=2) + -> Index Scan using pk_preference on preference f (cost=0.00..4.82 rows=1 width=77) (actual time= +0.50..0.50 rows=1 loops=2) + -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) (actual time=0.50..0.50 rows= +1 loops=2) + -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) (actual time=0.00..0.00 rows=1 loops=2) +Total runtime: 7.00 msec + +After vacuum analyze: + +Result (cost=3.19..5.29 rows=1 width=91) (actual time=3.00..4.00 rows=2 loops=1) + InitPlan + -> Seq Scan on block b (cost=0.00..1.01 rows=1 width=7) (actual time=0.00..0.00 rows=0 loops=1) + -> Nested Loop (cost=3.19..5.29 rows=1 width=91) (actual time=3.00..4.00 rows=2 loops=1) + -> Hash Join (cost=3.19..4.27 rows=1 width=91) (actual time=3.00..3.00 rows=2 loops=1) + -> Hash Join (cost=2.13..3.20 rows=1 width=72) (actual time=2.00..2.00 rows=3 loops=1) + -> Seq Scan on account a (cost=0.00..1.04 rows=3 width=31) (actual time=1.00..1.00 rows=3 loops=1) + -> Hash (cost=2.13..2.13 rows=1 width=41) (actual time=0.00..0.00 rows=0 loops=1) + -> Nested Loop (cost=0.00..2.13 rows=1 width=41) (actual time=0.00..0.00 rows=3 loops=1) + -> Seq Scan on profile p1 (cost=0.00..1.04 rows=1 width=12) (actual time=0.00..0.00 rows=1 +loops=1) + -> Seq Scan on preference f (cost=0.00..1.03 rows=3 width=29) (actual time=0.00..0.00 rows=3 +loops=1) + -> Hash (cost=1.05..1.05 rows=2 width=19) (actual time=1.00..1.00 rows=0 loops=1) + -> Seq Scan on profile p (cost=0.00..1.05 rows=2 width=19) (actual time=1.00..1.00 rows=2 loops=1) + -> Seq Scan on block (cost=0.00..1.01 rows=1 width=0) (actual time=0.00..0.00 rows=1 loops=2) +Total runtime: 7.00 msec + +The original query + +Nested Loop (cost=0.00..127.12 rows=995 width=894) (actual time=1.00..2.00 rows=2 loops=1) + -> Nested Loop (cost=0.00..97.17 rows=1 width=894) (actual time=1.00..1.00 rows=2 loops=1) + -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) (actual time=0.00..0.00 rows=3 loops=1) + -> Index Scan using pk_profile on profile p (cost=0.00..72.16 rows=1 width=605) (actual time=0.33..0.33 rows=1 +loops=3) + SubPlan + -> Materialize (cost=22.50..22.50 rows=5 width=55) (actual time=0.00..0.00 rows=0 loops=2) + -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55) (actual time=0.00..0.00 rows=0 loops=1) + -> Materialize (cost=44.82..44.82 rows=111 width=89) (actual time=0.50..0.50 rows=1 loops=2) + -> Nested Loop (cost=0.00..44.82 rows=111 width=89) (actual time=0.00..0.00 rows=3 loops=1) + -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) (actual time= +0.00..0.00 rows=1 loops=1) + -> Seq Scan on preference f (cost=0.00..20.00 rows=1000 width=77) (actual time=0.00..0.00 rows= +3 loops=1) + -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) (actual time=0.00..0.00 rows=1 loops=2) +Total runtime: 4.00 msec + +After replacing "p.userid NOT IN" with "NOT EXISTS": + +Result (cost=0.00..104.62 rows=995 width=894) (actual time=1.00..2.00 rows=2 loops=1) + InitPlan + -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55) (actual time=0.00..0.00 rows=0 loops=1) + -> Nested Loop (cost=0.00..104.62 rows=995 width=894) (actual time=1.00..1.00 rows=2 loops=1) + -> Nested Loop (cost=0.00..74.67 rows=1 width=894) (actual time=1.00..1.00 rows=2 loops=1) + -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) (actual time=0.00..0.00 rows=3 loops=1) + -> Index Scan using pk_profile on profile p (cost=0.00..49.66 rows=1 width=605) (actual time=0.33..0.33 +rows=1 loops=3) + SubPlan + -> Materialize (cost=44.82..44.82 rows=111 width=89) (actual time=0.50..0.50 rows=1 loops=2) + -> Nested Loop (cost=0.00..44.82 rows=111 width=89) (actual time=0.00..1.00 rows=3 loops=1) + -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) (actual time= +0.00..0.00 rows=1 loops=1) + -> Seq Scan on preference f (cost=0.00..20.00 rows=1000 width=77) (actual time=0.00..1.00 +rows=3 loops=1) + -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) (actual time=0.00..0.00 rows=1 loops=2) +Total runtime: 4.00 msec + +After vacuum analyze: + +Result (cost=7.30..9.39 rows=1 width=63) (actual time=3.00..3.00 rows=2 loops=1) + InitPlan + -> Seq Scan on block b (cost=0.00..1.01 rows=1 width=7) (actual time=0.00..0.00 rows=0 loops=1) + -> Nested Loop (cost=7.30..9.39 rows=1 width=63) (actual time=3.00..3.00 rows=2 loops=1) + -> Seq Scan on block (cost=0.00..1.01 rows=1 width=0) (actual time=0.00..0.00 rows=1 loops=1) + -> Materialize (cost=8.37..8.37 rows=1 width=63) (actual time=3.00..3.00 rows=2 loops=1) + -> Hash Join (cost=7.30..8.37 rows=1 width=63) (actual time=2.00..3.00 rows=2 loops=1) + -> Seq Scan on account a (cost=0.00..1.04 rows=3 width=31) (actual time=0.00..0.00 rows=3 loops=1) + -> Hash (cost=7.30..7.30 rows=1 width=32) (actual time=2.00..2.00 rows=0 loops=1) + -> Index Scan using profile_sex_idx on profile p (cost=0.00..7.30 rows=1 width=32) (actual time= +2.00..2.00 rows=2 loops=1) + SubPlan + -> Materialize (cost=2.13..2.13 rows=1 width=41) (actual time=0.50..0.50 rows=1 loops=2) + -> Nested Loop (cost=0.00..2.13 rows=1 width=41) (actual time=1.00..1.00 rows=3 loops=1) + -> Seq Scan on profile p1 (cost=0.00..1.04 rows=1 width=12) (actual time=0.00..0.00 +rows=1 loops=1) + -> Seq Scan on preference f (cost=0.00..1.03 rows=3 width=29) (actual time=0.00..0.00 +rows=3 loops=1) +Total runtime: 4.00 msec + + +12/5/2002 2:01:15 AM, Jochem van Dieten wrote: + +>Vernon Wu wrote: +>> +>> SELECT p.userid, p.year, a.country, a.province, a.city +>> FROM profile p, account a +>> WHERE p.userid=a.userid AND +>> (p.year BETWEEN 1961 AND 1976) AND +>> a.country='CA' AND +>> a.province='BC' AND +>> p.gender='f' AND +>> p.userid NOT IN (SELECT b.userid FROM block b WHERE b.personid='Joe') AND +>> block.userid IS NOT NULL AND +>> p.userid IN +>> (SELECT f.userid FROM preference f, profile p1 WHERE p1.userid='Joe' AND 2002-p1.year BETWEEN +>> f.minage AND f.maxage) +> +>You might want to flatten this into more joins and less subqueries, +>especially since you are using IN which is not very optimized: +> +>SELECT p.userid, p.year, a.country, a.province, a.city +>FROM profile p, account a, preference f, profile p1 +>WHERE +> f.userid = p.userid AND +> p.userid=a.userid AND +> (p.year BETWEEN 1961 AND 1976) AND +> a.country='CA' AND +> a.province='BC' AND +> p.gender='f' AND +> p.userid NOT IN (SELECT b.userid FROM block b WHERE b.personid='Joe') AND +> block.userid IS NOT NULL AND +> p1.userid='Joe' AND +> 2002-p1.year BETWEEN f.minage AND f.maxage +> +>Also, I am not sure about the NOT IN. If you can rewrite it using EXISTS +>try that, it might be faster. +> +> +>> Nested Loop (cost=0.00..127.12 rows=995 width=894) +>> -> Nested Loop (cost=0.00..97.17 rows=1 width=894) +>> -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) +>> -> Index Scan using pk_profile on profile p (cost=0.00..72.16 rows=1 width=605) +>> SubPlan +>> -> Materialize (cost=22.50..22.50 rows=5 width=55) +>> -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55 +>> ) +>> -> Materialize (cost=44.82..44.82 rows=111 width=89) +>> -> Nested Loop (cost=0.00..44.82 rows=111 width=89) +>> -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) +>> -> Seq Scan on preference f (cost=0.00..20.00 rows=1000 width=77) +> +>rows=1000 usually indicates you didn't vacuum analyze. Did you? +> +>> -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) +> +>And to add to Vernons questions: if you are using PostgreSQL 7.2 or +>later, please send us the EXPLAIN ANALYZE output. +> +>Jochem +> +> + + + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 14:18:43 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4D2F9476992 + for ; + Thu, 5 Dec 2002 14:18:39 -0500 (EST) +Received: from pd3mo2so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net + [24.71.223.10]) by postgresql.org (Postfix) with ESMTP id 0D5344766EF + for ; + Thu, 5 Dec 2002 14:12:37 -0500 (EST) +Received: from pd2mr3so.prod.shaw.ca (pd2mr3so-ser.prod.shaw.ca + [10.0.141.108]) + by l-daemon (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 + 2002)) with ESMTP id <0H6N00MN8UIXGW@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 12:08:57 -0700 (MST) +Received: from pn2ml8so.prod.shaw.ca + (pn2ml8so-qfe0.prod.shaw.ca [10.0.121.152]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H6N00LB1UIYYU@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 12:08:58 -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 <0H6N00GKNUIXJM@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 12:08:58 -0700 (MST) +Date: Thu, 05 Dec 2002 11:08:17 -0800 +From: Vernon Wu +Subject: Re: Is a better way to have the same result of this +In-reply-to: <1039066008.11433.3.camel@haggis> +To: PgSQL Performance ML , + Ron Johnson +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: 200212/31 +X-Sequence-Number: 447 + +Ron, + +The gender is indexed. Each user has account and preference, but not necessary block. + +I am currently seeking for query optimisation, not system configuration optimisation + +12/4/2002 9:26:48 PM, Ron Johnson wrote: + +>On Wed, 2002-12-04 at 18:26, Vernon Wu wrote: +>> I have the following query: +>> +>> SELECT p.userid, p.year, a.country, a.province, a.city +>> FROM profile p, account a +>> WHERE p.userid=a.userid AND +>> (p.year BETWEEN 1961 AND 1976) AND +>> a.country='CA' AND +>> a.province='BC' AND +>> p.gender='f' AND +>> p.userid NOT IN (SELECT b.userid FROM block b WHERE b.personid='Joe') AND +>> block.userid IS NOT NULL AND +>> p.userid IN +>> (SELECT f.userid FROM preference f, profile p1 WHERE p1.userid='Joe' AND 2002-p1.year BETWEEN +>> f.minage AND f.maxage) +>> +>> In plain English, it is that +>> +>> Joe finds females between the ages in the location who is not in the block table, while Joe's age is between what +they +>> prefer. +>> +>> The query plan is the followings: +>> +>> Nested Loop (cost=0.00..127.12 rows=995 width=894) +>> -> Nested Loop (cost=0.00..97.17 rows=1 width=894) +>> -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) +>> -> Index Scan using pk_profile on profile p (cost=0.00..72.16 rows=1 width=605) +>> SubPlan +>> -> Materialize (cost=22.50..22.50 rows=5 width=55) +>> -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55 +>> ) +>> -> Materialize (cost=44.82..44.82 rows=111 width=89) +>> -> Nested Loop (cost=0.00..44.82 rows=111 width=89) +>> -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) +>> -> Seq Scan on preference f (cost=0.00..20.00 rows=1000 width=77) +>> -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) +>> +>> It seems take quite long to run this query. How to optimise the query? +>> +>> Thanks for your input. +>> +>> Vernon +> +>What kind of indexes, if any, do you have on, and what is the +>cardinality of account, block and preference? +> +>What version of Postgres are you using? +> +>How much shared memory and buffers are you using? +> +>-- +>+------------------------------------------------------------+ +>| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +>| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +>| | +>| "they love our milk and honey, but preach about another | +>| way of living" | +>| Merle Haggard, "The Fighting Side Of Me" | +>+------------------------------------------------------------+ +> +> +>---------------------------(end of broadcast)--------------------------- +>TIP 4: Don't 'kill -9' the postmaster +> + + + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 14:59:54 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BF334476CD7 + for ; + Thu, 5 Dec 2002 14:59:53 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 2535F47688E + for ; + Thu, 5 Dec 2002 14:35:36 -0500 (EST) +Received: from klaster.net (ph239.krakow.cvx.ppp.tpnet.pl [217.99.208.239]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP + id DD06D2B25F; Thu, 5 Dec 2002 20:21:23 +0100 (CET) +Message-ID: <3DEFAAF7.6040000@klaster.net> +Date: Thu, 05 Dec 2002 20:37:27 +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: vernonw@gatewaytech.com +Cc: PgSQL Performance ML , + Ron Johnson +Subject: Re: Is a better way to have the same result of this +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: 200212/32 +X-Sequence-Number: 448 + +Vernon Wu wrote: + + > Ron, + > + > The gender is indexed. Each user has account and preference, but not +necessary block. + + +Indexing on gender won't speed up your query - it can even slow it down. +You have probably 50% of "f" and 50% of "m". Using index on gender will +divide your potential answers by 2. Make index on columns, which +excludes much more useless rows. +I think you can create index on: +- block/personid +- profile/userid + +I read in Postgres documentation(but didn't try) that you can also +change "id NOT IN (select id" to "not exists select * where id=". It may +help also. + +Do user have more than one account or preference? +If no, you can change "not in" into "inner/outer join" which are the +best ones. + +Regards, +Tomasz Myrta + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 15:13:16 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A165E476AB2 + for ; + Thu, 5 Dec 2002 15:13:15 -0500 (EST) +Received: from beamish.nsd.ca (unknown [205.150.156.194]) + by postgresql.org (Postfix) with ESMTP id 973194760A2 + for ; + Thu, 5 Dec 2002 14:45:21 -0500 (EST) +Received: (from smap@localhost) by beamish.nsd.ca (8.9.3/8.9.3) id OAA28735; + Thu, 5 Dec 2002 14:45:21 -0500 +X-Authentication-Warning: beamish.nsd.ca: smap set sender to + using -f +Received: from reddog.nsd.ca(192.168.101.30) by beamish.nsd.ca via smap + (V2.1/2.1+anti-relay+anti-spam) + id xma028733; Thu, 5 Dec 02 14:44:51 -0500 +Received: from nsd.ca (jllachan-linux.nsd.ca [192.168.101.148]) + by reddog.nsd.ca (8.8.7/8.8.7) with ESMTP id OAA04710; + Thu, 5 Dec 2002 14:43:30 -0500 +Message-ID: <3DEFACD6.A9573026@nsd.ca> +Date: Thu, 05 Dec 2002 14:45:26 -0500 +From: Jean-Luc Lachance +X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.9-31 i686) +X-Accept-Language: en +MIME-Version: 1.0 +To: vernonw@gatewaytech.com +Cc: PgSQL Performance ML , + Ron Johnson +Subject: Re: Is a better way to have the same result of this +References: +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/33 +X-Sequence-Number: 449 + +It is now common knowledge that the IN clause should be rewriten as an +EXISTS. + +SELECT p.userid, p.year, a.country, a.province, a.city +FROM profile p, account a +WHERE p.userid=a.userid AND + (p.year BETWEEN 1961 AND 1976) AND + a.country='CA' AND + a.province='BC' AND + p.gender='f' AND + NOT EXISTS ( SELECT 1 FROM block b WHERE b.personid='Joe' AND p.userid += b.userid) AND + block.userid IS NOT NULL AND + EXISTS ( SELECT 1 FROM preference f, profile p1 + WHERE p1.userid='Joe' AND p.userid = f.userif AND + 2002-p1.year BETWEEN f.minage AND f.maxage); + + + +Vernon Wu wrote: +> +> Ron, +> +> The gender is indexed. Each user has account and preference, but not necessary block. +> +> I am currently seeking for query optimisation, not system configuration optimisation +> +> 12/4/2002 9:26:48 PM, Ron Johnson wrote: +> +> >On Wed, 2002-12-04 at 18:26, Vernon Wu wrote: +> >> I have the following query: +> >> +> >> SELECT p.userid, p.year, a.country, a.province, a.city +> >> FROM profile p, account a +> >> WHERE p.userid=a.userid AND +> >> (p.year BETWEEN 1961 AND 1976) AND +> >> a.country='CA' AND +> >> a.province='BC' AND +> >> p.gender='f' AND +> >> p.userid NOT IN (SELECT b.userid FROM block b WHERE b.personid='Joe') AND +> >> block.userid IS NOT NULL AND +> >> p.userid IN +> >> (SELECT f.userid FROM preference f, profile p1 WHERE p1.userid='Joe' AND 2002-p1.year BETWEEN +> >> f.minage AND f.maxage) +> >> +> >> In plain English, it is that +> >> +> >> Joe finds females between the ages in the location who is not in the block table, while Joe's age is between what +> they +> >> prefer. +> >> +> >> The query plan is the followings: +> >> +> >> Nested Loop (cost=0.00..127.12 rows=995 width=894) +> >> -> Nested Loop (cost=0.00..97.17 rows=1 width=894) +> >> -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) +> >> -> Index Scan using pk_profile on profile p (cost=0.00..72.16 rows=1 width=605) +> >> SubPlan +> >> -> Materialize (cost=22.50..22.50 rows=5 width=55) +> >> -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55 +> >> ) +> >> -> Materialize (cost=44.82..44.82 rows=111 width=89) +> >> -> Nested Loop (cost=0.00..44.82 rows=111 width=89) +> >> -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) +> >> -> Seq Scan on preference f (cost=0.00..20.00 rows=1000 width=77) +> >> -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) +> >> + +From pgsql-performance-owner@postgresql.org Thu Dec 5 15:23:47 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A27D1476B8E + for ; + Thu, 5 Dec 2002 15:23:45 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 9CF87476BF3 + for ; + Thu, 5 Dec 2002 14:57:49 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18K286-0002HK-00 + for ; Thu, 05 Dec 2002 14:57:50 -0500 +Date: Thu, 5 Dec 2002 14:57:50 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: Is a better way to have the same result of this +Message-ID: <20021205145750.V4800@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <1039066008.11433.3.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: ; + from vernonw@gatewaytech.com on Thu, Dec 05, 2002 at 11:08:17AM + -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/34 +X-Sequence-Number: 450 + +On Thu, Dec 05, 2002 at 11:08:17AM -0800, Vernon Wu wrote: +> Ron, +> +> The gender is indexed. + +Given that gender only has two (? Very few, anyway) values, I can't +believe an index will be much use: it's not very selective. Maybe +combining several columns in one index will help you. + +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 Dec 5 16:16:26 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 72C0F476CDF + for ; + Thu, 5 Dec 2002 16:16:21 -0500 (EST) +Received: from pd4mo2so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net + [24.71.223.10]) by postgresql.org (Postfix) with ESMTP id 9F018476DCE + for ; + Thu, 5 Dec 2002 15:35:47 -0500 (EST) +Received: from pd3mr3so.prod.shaw.ca (pd3mr3so-ser.prod.shaw.ca + [10.0.141.179]) + by l-daemon (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 + 2002)) with ESMTP id <0H6N007OGYJOZD@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 13:35:48 -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 <0H6N00FRIYJO0U@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 13:35:48 -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 <0H6N00CKIYJMJ6@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 13:35:48 -0700 (MST) +Date: Thu, 05 Dec 2002 12:35:08 -0800 +From: Vernon Wu +Subject: Re: Is a better way to have the same result of this +In-reply-to: <3DEFACD6.A9573026@nsd.ca> +To: Jean-Luc Lachance +Cc: PgSQL Performance ML +Reply-To: vernonw@gatewaytech.com +Message-id: +MIME-version: 1.0 +X-Mailer: Opera 6.05 build 1140 +Content-type: text/plain; charset=us-ascii +Content-transfer-encoding: 7BIT +X-Priority: 3 (Normal) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/35 +X-Sequence-Number: 451 + + +I just learnt the "common knowledge" about four hourse ago. That does help to improve the performance indeed +according to the explain command. + +12/5/2002 11:45:26 AM, Jean-Luc Lachance wrote: + +>It is now common knowledge that the IN clause should be rewriten as an +>EXISTS. +> +>SELECT p.userid, p.year, a.country, a.province, a.city +>FROM profile p, account a +>WHERE p.userid=a.userid AND +> (p.year BETWEEN 1961 AND 1976) AND +> a.country='CA' AND +> a.province='BC' AND +> p.gender='f' AND +> NOT EXISTS ( SELECT 1 FROM block b WHERE b.personid='Joe' AND p.userid +>= b.userid) AND +> block.userid IS NOT NULL AND +> EXISTS ( SELECT 1 FROM preference f, profile p1 +> WHERE p1.userid='Joe' AND p.userid = f.userif AND +> 2002-p1.year BETWEEN f.minage AND f.maxage); +> +> +> +>Vernon Wu wrote: +>> +>> Ron, +>> +>> The gender is indexed. Each user has account and preference, but not necessary block. +>> +>> I am currently seeking for query optimisation, not system configuration optimisation +>> +>> 12/4/2002 9:26:48 PM, Ron Johnson wrote: +>> +>> >On Wed, 2002-12-04 at 18:26, Vernon Wu wrote: +>> >> I have the following query: +>> >> +>> >> SELECT p.userid, p.year, a.country, a.province, a.city +>> >> FROM profile p, account a +>> >> WHERE p.userid=a.userid AND +>> >> (p.year BETWEEN 1961 AND 1976) AND +>> >> a.country='CA' AND +>> >> a.province='BC' AND +>> >> p.gender='f' AND +>> >> p.userid NOT IN (SELECT b.userid FROM block b WHERE b.personid='Joe') AND +>> >> block.userid IS NOT NULL AND +>> >> p.userid IN +>> >> (SELECT f.userid FROM preference f, profile p1 WHERE p1.userid='Joe' AND 2002-p1.year BETWEEN +>> >> f.minage AND f.maxage) +>> >> +>> >> In plain English, it is that +>> >> +>> >> Joe finds females between the ages in the location who is not in the block table, while Joe's age is between what +>> they +>> >> prefer. +>> >> +>> >> The query plan is the followings: +>> >> +>> >> Nested Loop (cost=0.00..127.12 rows=995 width=894) +>> >> -> Nested Loop (cost=0.00..97.17 rows=1 width=894) +>> >> -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) +>> >> -> Index Scan using pk_profile on profile p (cost=0.00..72.16 rows=1 width=605) +>> >> SubPlan +>> >> -> Materialize (cost=22.50..22.50 rows=5 width=55) +>> >> -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55 +>> >> ) +>> >> -> Materialize (cost=44.82..44.82 rows=111 width=89) +>> >> -> Nested Loop (cost=0.00..44.82 rows=111 width=89) +>> >> -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) +>> >> -> Seq Scan on preference f (cost=0.00..20.00 rows=1000 width=77) +>> >> -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) +>> >> +> +>---------------------------(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 Dec 5 16:21:02 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3C588476D28 + for ; + Thu, 5 Dec 2002 16:21:01 -0500 (EST) +Received: from rtlocal.trade-india.com (mail-relay.trade-india.com + [203.196.129.235]) + by postgresql.org (Postfix) with SMTP id A7F94476F42 + for ; + Thu, 5 Dec 2002 15:37:09 -0500 (EST) +Received: (qmail 28530 invoked from network); 5 Dec 2002 20:28:00 -0000 +Received: from unknown (HELO system67.trade-india-local.com) (192.168.0.67) + by infocom-236-129-del.trade-india.com with SMTP; + 5 Dec 2002 20:28:00 -0000 +From: "Rajesh Kumar Mallah." +Organization: Infocom Network Limited. +To: pgsql-performance@postgresql.org +Subject: Filesystem optimisation for postgresql tables and WAL logs on linux. +Date: Fri, 6 Dec 2002 02:11:27 +0530 +User-Agent: KMail/1.5 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="us-ascii" +Content-Transfer-Encoding: 7bit +Content-Disposition: inline +Message-Id: <200212060211.27728.mallah@trade-india.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/36 +X-Sequence-Number: 452 + + +Hi, + + +I have got there SCSIs HDDs for the postgresql Box +i plan to install OS on 1st , 2nd for tables and indexes and third +for pg_xlog. + +Bruce Momjian's "H/W Perf tuning" on +http://www.ca.postgresql.org/docs/momjian/hw_performance/node11.html +recommends 8k blocksize for the filesystem which is same as the page size. + +On linux ext2 fs (on my server) 4096 is the default blocak size and 8192 bytes +is not supported. + +but man mkfs.ext2 on linux mentions an option -T which is: +-T fs-type + Specify how the filesystem is going to be used, so that mke2fs can chose optimal filesystem parameters for that + use. The supported filesystem types are: + news one inode per 4kb block + largefile one inode per megabyte + largefile4 one inode per 4 megabytes + +is the above relevent as far as optimisation for filesystem for tables is concerned? + +Also for the pg_xlog drive is a particular block size more favourable then others? + + +regds +mallah. + + + + + + +-- +Rajesh Kumar Mallah, +Project Manager (Development) +Infocom Network Limited, New Delhi +phone: +91(11)6152172 (221) (L) ,9811255597 (M) + +Visit http://www.trade-india.com , +India's Leading B2B eMarketplace. + + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 16:53:03 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0D8F6476AA4 + for ; + Thu, 5 Dec 2002 16:53:01 -0500 (EST) +Received: from pd6mo2so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net + [24.71.223.10]) by postgresql.org (Postfix) with ESMTP id DFEE5476AE1 + for ; + Thu, 5 Dec 2002 15:58:53 -0500 (EST) +Received: from pd5mr3so.prod.shaw.ca + (pd5mr3so-qfe3.prod.shaw.ca [10.0.141.144]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H6N00IE0ZM7X7@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 13:58:55 -0700 (MST) +Received: from pn2ml9so.prod.shaw.ca (pn2ml9so-qfe0.prod.shaw.ca [10.0.121.7]) + by l-daemon (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 + 2002)) with ESMTP id <0H6N00DKKZM74K@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 13:58:55 -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 <0H6N00IVAZM68E@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 13:58:54 -0700 (MST) +Date: Thu, 05 Dec 2002 12:58:13 -0800 +From: Vernon Wu +Subject: Re: Is a better way to have the same result of this +In-reply-to: <3DEFB898.3050602@klaster.net> +To: Tomasz Myrta +Cc: pgsql-performance@postgresql.org +Reply-To: vernonw@gatewaytech.com +Message-id: <5A6KF0NHNMGEJG7XRYWL1X8X8.3defbde5@kimiko> +MIME-version: 1.0 +X-Mailer: Opera 6.05 build 1140 +Content-type: text/plain; charset=us-ascii +Content-transfer-encoding: 7BIT +X-Priority: 3 (Normal) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/37 +X-Sequence-Number: 453 + +Tomasz, + +I am under the impression that a primary key field is automically as a unique index. It seems to be correct after I verify it +with the page http://www.commandprompt.com/ppbook/index.lxp?lxpwrap=c13329%2ehtm#CREATINGANINDEX + +Thanks for bringing up the question. + +Vernon + +12/5/2002 12:35:36 PM, Tomasz Myrta wrote: + +>Vernon Wu wrote: +> +>> The personid is a foreign key in the block table, and the the userid +>> is the key of the profile table. So, both are indexed +>> by nature (if I don't make a mistake). +> +>What kind of nature? Did you create indexes for these fields? Postgres +>doesn't create indexes by itself - even if field is a primary key. You +>have to do it on your own. I think also, that Postgres doesn't use index +>for tables having less then 200 rows - sequence scan is faster. +>Regards, +>Tomasz Myrta +> +> +> + + + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 16:56:54 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1D491476857 + for ; + Thu, 5 Dec 2002 16:56:53 -0500 (EST) +Received: from beamish.nsd.ca (unknown [205.150.156.194]) + by postgresql.org (Postfix) with ESMTP id 64013476DCD + for ; + Thu, 5 Dec 2002 16:04:22 -0500 (EST) +Received: (from smap@localhost) by beamish.nsd.ca (8.9.3/8.9.3) id QAA29559; + Thu, 5 Dec 2002 16:04:22 -0500 +X-Authentication-Warning: beamish.nsd.ca: smap set sender to + using -f +Received: from reddog.nsd.ca(192.168.101.30) by beamish.nsd.ca via smap + (V2.1/2.1+anti-relay+anti-spam) + id xma029557; Thu, 5 Dec 02 16:03:52 -0500 +Received: from nsd.ca (jllachan-linux.nsd.ca [192.168.101.148]) + by reddog.nsd.ca (8.8.7/8.8.7) with ESMTP id QAA05392; + Thu, 5 Dec 2002 16:02:31 -0500 +Message-ID: <3DEFBF5C.656EADA2@nsd.ca> +Date: Thu, 05 Dec 2002 16:04:28 -0500 +From: Jean-Luc Lachance +X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.9-31 i686) +X-Accept-Language: en +MIME-Version: 1.0 +To: vernonw@gatewaytech.com +Cc: PgSQL Performance ML +Subject: Re: Is a better way to have the same result of this +References: +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/38 +X-Sequence-Number: 454 + +Good for you! Too bad the parser does not know about it... + + + +Vernon Wu wrote: +> +> I just learnt the "common knowledge" about four hourse ago. That does help to improve the performance indeed +> according to the explain command. +> +> 12/5/2002 11:45:26 AM, Jean-Luc Lachance wrote: +> +> >It is now common knowledge that the IN clause should be rewriten as an +> >EXISTS. +> > +> >SELECT p.userid, p.year, a.country, a.province, a.city +> >FROM profile p, account a +> >WHERE p.userid=a.userid AND +> > (p.year BETWEEN 1961 AND 1976) AND +> > a.country='CA' AND +> > a.province='BC' AND +> > p.gender='f' AND +> > NOT EXISTS ( SELECT 1 FROM block b WHERE b.personid='Joe' AND p.userid +> >= b.userid) AND +> > block.userid IS NOT NULL AND +> > EXISTS ( SELECT 1 FROM preference f, profile p1 +> > WHERE p1.userid='Joe' AND p.userid = f.userif AND +> > 2002-p1.year BETWEEN f.minage AND f.maxage); +> > +> > +> > +> >Vernon Wu wrote: +> >> +> >> Ron, +> >> +> >> The gender is indexed. Each user has account and preference, but not necessary block. +> >> +> >> I am currently seeking for query optimisation, not system configuration optimisation +> >> +> >> 12/4/2002 9:26:48 PM, Ron Johnson wrote: +> >> +> >> >On Wed, 2002-12-04 at 18:26, Vernon Wu wrote: +> >> >> I have the following query: +> >> >> +> >> >> SELECT p.userid, p.year, a.country, a.province, a.city +> >> >> FROM profile p, account a +> >> >> WHERE p.userid=a.userid AND +> >> >> (p.year BETWEEN 1961 AND 1976) AND +> >> >> a.country='CA' AND +> >> >> a.province='BC' AND +> >> >> p.gender='f' AND +> >> >> p.userid NOT IN (SELECT b.userid FROM block b WHERE b.personid='Joe') AND +> >> >> block.userid IS NOT NULL AND +> >> >> p.userid IN +> >> >> (SELECT f.userid FROM preference f, profile p1 WHERE p1.userid='Joe' AND 2002-p1.year BETWEEN +> >> >> f.minage AND f.maxage) +> >> >> +> >> >> In plain English, it is that +> >> >> +> >> >> Joe finds females between the ages in the location who is not in the block table, while Joe's age is between what +> >> they +> >> >> prefer. +> >> >> +> >> >> The query plan is the followings: +> >> >> +> >> >> Nested Loop (cost=0.00..127.12 rows=995 width=894) +> >> >> -> Nested Loop (cost=0.00..97.17 rows=1 width=894) +> >> >> -> Seq Scan on account a (cost=0.00..25.00 rows=1 width=289) +> >> >> -> Index Scan using pk_profile on profile p (cost=0.00..72.16 rows=1 width=605) +> >> >> SubPlan +> >> >> -> Materialize (cost=22.50..22.50 rows=5 width=55) +> >> >> -> Seq Scan on block b (cost=0.00..22.50 rows=5 width=55 +> >> >> ) +> >> >> -> Materialize (cost=44.82..44.82 rows=111 width=89) +> >> >> -> Nested Loop (cost=0.00..44.82 rows=111 width=89) +> >> >> -> Index Scan using pk_profile on profile p1 (cost=0.00..4.82 rows=1 width=12) +> >> >> -> Seq Scan on preference f (cost=0.00..20.00 rows=1000 width=77) +> >> >> -> Seq Scan on block (cost=0.00..20.00 rows=995 width=0) +> >> >> +> > +> >---------------------------(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 Dec 5 17:00:47 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4C6ED476C0C + for ; + Thu, 5 Dec 2002 17:00:45 -0500 (EST) +Received: from ns1.tudelft.nl (ns1.tudelft.nl [130.161.180.1]) + by postgresql.org (Postfix) with ESMTP id 34441476E67 + for ; + Thu, 5 Dec 2002 16:06:06 -0500 (EST) +Received: from CONVERSION-DAEMON.mailhost2.tudelft.nl by mailhost2.tudelft.nl + (PMDF V6.1-1 #40925) id <0H6N00201ZY4RS@mailhost2.tudelft.nl> for + pgsql-performance@postgresql.org; Thu, 05 Dec 2002 22:06:07 +0100 (MET) +Received: from listserv.tudelft.nl (listserv.tudelft.nl [130.161.180.33]) + by mailhost2.tudelft.nl (PMDF V6.1-1 #40925) + with ESMTP id <0H6N0007PZY4ND@mailhost2.tudelft.nl>; Thu, + 05 Dec 2002 22:06:04 +0100 (MET) +Received: from oli.tudelft.nl (oli244.rolahola.tudelft.nl [130.161.67.244]) + by listserv.tudelft.nl (8.12.5/8.12.5) with ESMTP id gB5L63Fx029706; + Thu, 05 Dec 2002 22:06:04 +0100 (MET) +Date: Thu, 05 Dec 2002 22:06:03 +0100 +From: Jochem van Dieten +Subject: Re: Is a better way to have the same result of this query? +In-reply-to: +To: vernonw@gatewaytech.com +Cc: pgsql-performance@postgresql.org +Message-id: <3DEFBFBB.1060601@oli.tudelft.nl> +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 (Windows; U; WinNT4.0; en-US; rv:1.2) Gecko/20021126 +References: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/39 +X-Sequence-Number: 455 + +Vernon Wu wrote: +> +> The followings are the analyise outcomes after I did some modifications with the query. My finding is that the new query +> does improve the performance according to the plan. The actual time is reversed might due to the fact the test data is +> very small (the machine is a very old one by the way). The userid is the key for all tables and the gender is indexed. Do I +> also index the country and province to improve the preformance? + +You start by using a dataset of realistic size. Sorry, but if the actual +time is < 10.00 ms it is rather pointless to optimize further since +chance is going to be the biggest factor. And the IN/EXISTS difference +is dependent on dataset size. + +Jochem + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 17:21:14 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 009AD47628D + for ; + Thu, 5 Dec 2002 17:21:13 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id EB066477077 + for ; + Thu, 5 Dec 2002 16:18:07 -0500 (EST) +Received: from klaster.net (pj160.krakow.cvx.ppp.tpnet.pl [217.99.210.160]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP + id 2CFAB2B25F; Thu, 5 Dec 2002 22:03:57 +0100 (CET) +Message-ID: <3DEFC2FE.2070702@klaster.net> +Date: Thu, 05 Dec 2002 22:19:58 +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: vernonw@gatewaytech.com +Cc: pgsql-performance@postgresql.org +Subject: Re: Is a better way to have the same result of this +References: <5A6KF0NHNMGEJG7XRYWL1X8X8.3defbde5@kimiko> +In-Reply-To: <5A6KF0NHNMGEJG7XRYWL1X8X8.3defbde5@kimiko> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/40 +X-Sequence-Number: 456 + +Vernon Wu wrote: + +> Tomasz, +> +> I am under the impression that a primary key field is automically as a +> unique index. It seems to be correct after I verify it +> with the page +> http://www.commandprompt.com/ppbook/index.lxp?lxpwrap=c13329%2ehtm#CREATINGANINDEX + +You are right. Primary key creates unique index. I use sometimes Pgadmin +and it doesn't show these indexes :-( +Tomasz Myrta + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 17:27:02 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C5104476D32 + for ; + Thu, 5 Dec 2002 17:27:00 -0500 (EST) +Received: from pd3mo1so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net + [24.71.223.10]) by postgresql.org (Postfix) with ESMTP id 4FD48476CF0 + for ; + Thu, 5 Dec 2002 16:23:55 -0500 (EST) +Received: from pd4mr2so.prod.shaw.ca + (pd4mr2so-qfe3.prod.shaw.ca [10.0.141.213]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H6O009MY0RW7Z@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 14:23:56 -0700 (MST) +Received: from pn2ml8so.prod.shaw.ca + (pn2ml8so-qfe0.prod.shaw.ca [10.0.121.152]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H6O00ALK0RWLO@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 14:23:56 -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 <0H6O00ICJ0RVZF@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 14:23:56 -0700 (MST) +Date: Thu, 05 Dec 2002 13:23:16 -0800 +From: Vernon Wu +Subject: Re: Is a better way to have the same result of this query? +In-reply-to: <3DEFBFBB.1060601@oli.tudelft.nl> +To: Jochem van Dieten +Cc: 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=us-ascii +Content-transfer-encoding: 7BIT +X-Priority: 3 (Normal) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/41 +X-Sequence-Number: 457 + + + +12/5/2002 1:06:03 PM, Jochem van Dieten wrote: + +>You start by using a dataset of realistic size. Sorry, but if the actual +>time is < 10.00 ms it is rather pointless to optimize further since +>chance is going to be the biggest factor. And the IN/EXISTS difference +>is dependent on dataset size. +> + +Do you mean that using "EXIST" is not necessary out-perform using 'IN" even the "explain" say so? What is the right +size for those two key words? + +Thanks for your very hepful information. + +Vernon + + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 17:51:52 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 37526476116 + for ; + Thu, 5 Dec 2002 17:51:51 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 401D747653C + for ; + Thu, 5 Dec 2002 17:00:11 -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 gB5M0Apd002708; + Thu, 5 Dec 2002 17:00:10 -0500 (EST) +To: "john cartmell" +Cc: pgsql-performance@postgresql.org +Subject: Re: ORDER BY ... LIMIT.. performance +In-reply-to: + <94B61ED0D8770A4A98A3DBD72DBBA1F821A80A@mediaexch01.mediaburst.co.uk> +References: + <94B61ED0D8770A4A98A3DBD72DBBA1F821A80A@mediaexch01.mediaburst.co.uk> +Comments: In-reply-to "john cartmell" + message dated "Thu, 05 Dec 2002 09:51:09 +0000" +Date: Thu, 05 Dec 2002 17:00:09 -0500 +Message-ID: <2707.1039125609@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/42 +X-Sequence-Number: 458 + +"john cartmell" writes: +> Without the LIMIT clause the query takes approximately 3-5 seconds to +> return. +> If total number of rows returned without the LIMIT clause is greater +> than 20 records, then the above query also takes th same amount of time. +> But if the the total number of rows is 20 or less then the time taken +> for the above query to return goes up to 20-30 seconds. + +What does EXPLAIN (or better EXPLAIN ANALYZE) show for these various +cases? Evidently the planner is shifting to a different plan because +of the small LIMIT, but with no details it's hard to say anything +useful. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Dec 5 18:00:01 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2DBA5476515 + for ; + Thu, 5 Dec 2002 17:59:59 -0500 (EST) +Received: from ns1.tudelft.nl (ns1.tudelft.nl [130.161.180.1]) + by postgresql.org (Postfix) with ESMTP id E3437476861 + for ; + Thu, 5 Dec 2002 17:05:58 -0500 (EST) +Received: from CONVERSION-DAEMON.mailhost2.tudelft.nl by mailhost2.tudelft.nl + (PMDF V6.1-1 #40925) id <0H6O006012PYWF@mailhost2.tudelft.nl> for + pgsql-performance@postgresql.org; Thu, 05 Dec 2002 23:06:00 +0100 (MET) +Received: from listserv.tudelft.nl (listserv.tudelft.nl [130.161.180.33]) + by mailhost2.tudelft.nl (PMDF V6.1-1 #40925) + with ESMTP id <0H6O000GG2PYND@mailhost2.tudelft.nl>; Thu, + 05 Dec 2002 23:05:58 +0100 (MET) +Received: from oli.tudelft.nl (oli244.rolahola.tudelft.nl [130.161.67.244]) + by listserv.tudelft.nl (8.12.5/8.12.5) with ESMTP id gB5M5vFx003374; + Thu, 05 Dec 2002 23:05:58 +0100 (MET) +Date: Thu, 05 Dec 2002 23:05:57 +0100 +From: Jochem van Dieten +Subject: Re: Is a better way to have the same result of this query? +In-reply-to: +To: vernonw@gatewaytech.com +Cc: pgsql-performance@postgresql.org +Message-id: <3DEFCDC5.9050906@oli.tudelft.nl> +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 (Windows; U; WinNT4.0; en-US; rv:1.2) Gecko/20021126 +References: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/43 +X-Sequence-Number: 459 + +Vernon Wu wrote: +> 12/5/2002 1:06:03 PM, Jochem van Dieten wrote: +> +>>You start by using a dataset of realistic size. Sorry, but if the actual +>>time is < 10.00 ms it is rather pointless to optimize further since +>>chance is going to be the biggest factor. And the IN/EXISTS difference +>>is dependent on dataset size. +> +> Do you mean that using "EXIST" is not necessary out-perform using 'IN" even the "explain" say so? What is the right +> size for those two key words? + +IIRC, IN might be faster on small datasets, but EXISTS is faster on big +ones. So you have to optimize with a dataset that resembles the actual +dataset you will be using in production as close as possible. I don't +know what the size is at which one gets faster as the other. + +Jochem + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 18:10:08 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4D01A476284 + for ; + Thu, 5 Dec 2002 18:10:02 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 15AD3476EED + for ; + Thu, 5 Dec 2002 17:21:39 -0500 (EST) +Received: from [216.135.165.74] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.1) + with HTTP id 2023168; Thu, 05 Dec 2002 14:21:18 -0800 +From: "Josh Berkus" +Subject: Re: ORDER BY ... LIMIT.. performance +To: "john cartmell" , + +X-Mailer: CommuniGate Pro Web Mailer v.4.0.1 +Date: Thu, 05 Dec 2002 14:21:18 -0800 +Message-ID: +In-Reply-To: + <94B61ED0D8770A4A98A3DBD72DBBA1F821A80A@mediaexch01.mediaburst.co.uk> +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: 200212/44 +X-Sequence-Number: 460 + +John, + +> I am not sure whether this is a know problem but we discovered this +> the +> other day. +> We are using PostgreSQL 7.2.1 on Redhat 7.3. + +First of all, there are a few bug-fixes between 7.2.1 and 7.2.3. One +relates to backups, and another to security. So you should upgrade to +7.2.3 immediately -- no init or restore from backup required (not +version 7.3, which has some significant changes). + +> The table has about over a million rows (~1.4). +> +> The query concerned is of the form +> +> SELECT * +> FROM tblCompany +> WHERE lower(companyname) like 'company%' +> ORDER BY companyname +> LIMIT 20,0 +> +> There is a functional index lower(companyname) for the like clause. +> +> Without the LIMIT clause the query takes approximately 3-5 seconds to +> return. +> If total number of rows returned without the LIMIT clause is greater +> than 20 records, then the above query also takes th same amount of +> time. +> But if the the total number of rows is 20 or less then the time taken +> for the above query to return goes up to 20-30 seconds. Has anyone +> else +> come across this. We have managed to get round it by performing a +> count +> first and only performing the LIMIT if there are enough rows but +> surely +> the query should be able to do this itself! + +This seems very odd. Please do the following: + +1) Post an EXPLAIN ANALYZE statement for the above query, with limit, +that returns in 3-5 seconds. +2) Post an EXPLAIN ANALYZE for a query that returns slowly (20-30 +seconds). + +Thanks! + +-Josh + + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 18:23:29 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2DDB5476F37 + for ; + Thu, 5 Dec 2002 18:23:26 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP id 18A12476B25 + for ; + Thu, 5 Dec 2002 17:42:58 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id gB5MgnF18632; + Thu, 5 Dec 2002 17:42:49 -0500 (EST) +From: Bruce Momjian +Message-Id: <200212052242.gB5MgnF18632@candle.pha.pa.us> +Subject: Re: Filesystem optimisation for postgresql tables and WAL +In-Reply-To: <200212060211.27728.mallah@trade-india.com> +To: "Rajesh Kumar Mallah." +Date: Thu, 5 Dec 2002 17:42:49 -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: 200212/45 +X-Sequence-Number: 461 + + +I don't remember saying they should match, it is just that it is nice if +it does, but I don't think it would make any major difference in +performance. In fact, some use 32k pages sizes, and get a performance +boost, and clearly don't have 32k file system blocks. + +--------------------------------------------------------------------------- + +Rajesh Kumar Mallah. wrote: +> +> Hi, +> +> +> I have got there SCSIs HDDs for the postgresql Box +> i plan to install OS on 1st , 2nd for tables and indexes and third +> for pg_xlog. +> +> Bruce Momjian's "H/W Perf tuning" on +> http://www.ca.postgresql.org/docs/momjian/hw_performance/node11.html +> recommends 8k blocksize for the filesystem which is same as the page size. +> +> On linux ext2 fs (on my server) 4096 is the default blocak size and 8192 bytes +> is not supported. +> +> but man mkfs.ext2 on linux mentions an option -T which is: +> -T fs-type +> Specify how the filesystem is going to be used, so that mke2fs can chose optimal filesystem parameters for that +> use. The supported filesystem types are: +> news one inode per 4kb block +> largefile one inode per megabyte +> largefile4 one inode per 4 megabytes +> +> is the above relevent as far as optimisation for filesystem for tables is concerned? +> +> Also for the pg_xlog drive is a particular block size more favourable then others? +> +> +> regds +> mallah. +> +> +> +> +> +> +> -- +> Rajesh Kumar Mallah, +> Project Manager (Development) +> Infocom Network Limited, New Delhi +> phone: +91(11)6152172 (221) (L) ,9811255597 (M) +> +> Visit http://www.trade-india.com , +> India's Leading B2B eMarketplace. +> +> +> +> ---------------------------(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-performance-owner@postgresql.org Thu Dec 5 18:58:55 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 39873476176 + for ; + Thu, 5 Dec 2002 18:58:53 -0500 (EST) +Received: from pd6mo2so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net + [24.71.223.10]) by postgresql.org (Postfix) with ESMTP id E5E5C476978 + for ; + Thu, 5 Dec 2002 18:20:26 -0500 (EST) +Received: from pd3mr3so.prod.shaw.ca (pd3mr3so-ser.prod.shaw.ca + [10.0.141.179]) + by l-daemon (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 + 2002)) with ESMTP id <0H6O00EIJ65LHV@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 16:20:09 -0700 (MST) +Received: from pn2ml2so.prod.shaw.ca + (pn2ml2so-qfe0.prod.shaw.ca [10.0.121.146]) by l-daemon + (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 2002)) + with ESMTP id <0H6O00GBW65LLJ@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 16:20:09 -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 <0H6O00MCE65KHJ@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 16:20:09 -0700 (MST) +Date: Thu, 05 Dec 2002 15:19:29 -0800 +From: Vernon Wu +Subject: Re: Is a better way to have the same result of this +In-reply-to: <20021205145750.V4800@mail.libertyrms.com> +To: PgSQL Performance ML , + Andrew Sullivan +Reply-To: vernonw@gatewaytech.com +Message-id: +MIME-version: 1.0 +X-Mailer: Opera 6.05 build 1140 +Content-type: text/plain; charset=us-ascii +Content-transfer-encoding: 7BIT +X-Priority: 3 (Normal) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/46 +X-Sequence-Number: 462 + +Andrew, + +Following your suggestion, I have combined the year field with the gender to create a multicolumn index. That shall be +better than indexing gender alone. I also create a multicolumn index (country, province, city) for the account table. + +Would you suggest indexing all possible fields such as ethnicity, religion , education, employment in the profile table; or +based on what queries I run, to have some multicolumn indexes? + +BTW, do you get a lot of snow in Toronto these few days? + +Veronon + +12/5/2002 11:57:50 AM, Andrew Sullivan wrote: + +>On Thu, Dec 05, 2002 at 11:08:17AM -0800, Vernon Wu wrote: +>> Ron, +>> +>> The gender is indexed. +> +>Given that gender only has two (? Very few, anyway) values, I can't +>believe an index will be much use: it's not very selective. Maybe +>combining several columns in one index will help you. +> +>A +> +>-- +>---- +>Andrew Sullivan 204-4141 Yonge Street +>Liberty RMS Toronto, Ontario Canada +> M2P 2A8 +> +1 416 646 3304 x110 +> +> +>---------------------------(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 Dec 5 20:10:58 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id F09EE4767B8 + for ; + Thu, 5 Dec 2002 20:10:54 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 871514771F5 + for ; + Thu, 5 Dec 2002 18:56:19 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18K5qw-0007nq-00 + for ; Thu, 05 Dec 2002 18:56:22 -0500 +Date: Thu, 5 Dec 2002 18:56:22 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: Is a better way to have the same result of this +Message-ID: <20021205185622.B29425@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: + <3DEFBF5C.656EADA2@nsd.ca> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <3DEFBF5C.656EADA2@nsd.ca>; + from jllachan@nsd.ca on Thu, Dec 05, 2002 at 04:04:28PM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/47 +X-Sequence-Number: 463 + +On Thu, Dec 05, 2002 at 04:04:28PM -0500, Jean-Luc Lachance wrote: +> Good for you! Too bad the parser does not know about it... + +LAst I heard, there was a problem about providing a rigourous +mathematical proof that NOT EXISTS and NOT IN are really the same. +If you can prove it, I'm sure people would be pleased. + +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 Dec 5 20:11:38 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0C96B476E8E + for ; + Thu, 5 Dec 2002 20:11:37 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 64BB0476E93 + for ; + Thu, 5 Dec 2002 18:58:32 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18K5t5-0007qf-00 + for ; Thu, 05 Dec 2002 18:58:35 -0500 +Date: Thu, 5 Dec 2002 18:58:35 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: Is a better way to have the same result of this +Message-ID: <20021205185835.C29425@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <20021205145750.V4800@mail.libertyrms.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 vernonw@gatewaytech.com on Thu, Dec 05, 2002 at 03:19:29PM + -0800 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/48 +X-Sequence-Number: 464 + +On Thu, Dec 05, 2002 at 03:19:29PM -0800, Vernon Wu wrote: +> Andrew, +> +> Would you suggest indexing all possible fields such as ethnicity, +> religion , education, employment in the profile table; or based on +> what queries I run, to have some multicolumn indexes? + +Never index anything more than you need. There is a fairly serious +penalty at insertion time for indexes, so you can reduce some +overhead that way. Note, too, that index space is not recaptured by +Postgres's VACUUM, which imposes a small performance cost, but can be +a real disk-gobbler if you're not careful. + +> BTW, do you get a lot of snow in Toronto these few days? + +We had some a few weeks ago. It's pretty clear right now. + +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 Dec 5 20:26:13 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 86824476082 + for ; + Thu, 5 Dec 2002 20:26:12 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id C4EA7476699 + for ; + Thu, 5 Dec 2002 19:21:18 -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 gB60KeHB018897; + Thu, 5 Dec 2002 17:20:40 -0700 (MST) +Date: Thu, 5 Dec 2002 17:18:10 -0700 (MST) +From: "scott.marlowe" +To: Vernon Wu +Cc: PgSQL Performance ML , + Andrew Sullivan +Subject: Re: Is a better way to have the same result of this +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: 200212/49 +X-Sequence-Number: 465 + +On Thu, 5 Dec 2002, Vernon Wu wrote: + +> Andrew, +> +> Following your suggestion, I have combined the year field with the gender to create a multicolumn index. That shall be +> better than indexing gender alone. I also create a multicolumn index (country, province, city) for the account table. +> +> Would you suggest indexing all possible fields such as ethnicity, religion , education, employment in the profile table; or +> based on what queries I run, to have some multicolumn indexes? +> +> BTW, do you get a lot of snow in Toronto these few days? + +Vernon, just so you know, for multi-column indexes to be useful in +Postgresql, the columns need to be used in the same order they are +declared in the index if you are using them for an order by. + +select * from table order by sex, age; + +could use the index + +create column table_sex_age on table (sex,age); + +but would not use the index + +create column table_age_sex on table (age,sex); + +However, the order in a where clause portion doesn't really seem to +matter, so + +select * from table where sex='m' and age>=38 + +and + +select * from table where age>=38 and sex='m' + +should both be able to use the index. + +also, you can use functional indexes, but the arguments in the where +clause need the same basic form to be useful. So, if you commonly make a +select like this: + +select * from table where age>50 and age<=59; + +then you could make a functional index like : + +create index table_age_50_59 on table (age) where age>50 and age<=59; + +However, the query + +select * from table where age>50 and age<=58; + +Wouldn't use that index, since the age <= part doesn't match up. It could +possible use a generic index on age though, i.e. one like + +create index table_age on table (age); + +But that index will be larger than the partial one, and so the planner may +skip using it and use a seq scan instead. Hard to say until your database +is populated with some representational test data. + +Since these indexes will be only a small fraction of the total data, it +will often be advantageous to use them with a query. + +After you have a set of test data, then you can start looking at tuning +random page cost and such to make your hardware perform properly for +individual queries. Well, hope that helps. + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 20:41:53 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EFF12476D59 + for ; + Thu, 5 Dec 2002 20:41:50 -0500 (EST) +Received: from pd6mo1so.prod.shaw.ca (shawidc-mo1.cg.shawcable.net + [24.71.223.10]) by postgresql.org (Postfix) with ESMTP id 4D6FA476F4D + for ; + Thu, 5 Dec 2002 19:44:35 -0500 (EST) +Received: from pd2mr2so.prod.shaw.ca (pd2mr2so-ser.prod.shaw.ca + [10.0.141.109]) + by l-daemon (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 + 2002)) with ESMTP id <0H6O00EMPA2EQO@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 17:44:38 -0700 (MST) +Received: from pn2ml10so.prod.shaw.ca + (pn2ml10so-qfe0.prod.shaw.ca [10.0.121.80]) + by l-daemon (iPlanet Messaging Server 5.1 HotFix 0.8 (built May 12 + 2002)) with ESMTP id <0H6O00J6PA2ETH@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 17:44:38 -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 <0H6O00BQ0A2CUI@l-daemon> for + pgsql-performance@postgresql.org; + Thu, 05 Dec 2002 17:44:38 -0700 (MST) +Date: Thu, 05 Dec 2002 16:43:58 -0800 +From: Vernon Wu +Subject: Re: Is a better way to have the same result of this +In-reply-to: +To: "scott.marlowe" +Cc: PgSQL Performance ML +Reply-To: vernonw@gatewaytech.com +Message-id: +MIME-version: 1.0 +X-Mailer: Opera 6.05 build 1140 +Content-type: text/plain; charset=US-ASCII +Content-transfer-encoding: 7BIT +X-Priority: 3 (Normal) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/50 +X-Sequence-Number: 466 + +12/5/2002 4:18:10 PM, "scott.marlowe" wrote: + +>Vernon, just so you know, for multi-column indexes to be useful in +>Postgresql, the columns need to be used in the same order they are +>declared in the index if you are using them for an order by. +> +>select * from table order by sex, age; +> +>could use the index +> +>create column table_sex_age on table (sex,age); +> +>but would not use the index +> +>create column table_age_sex on table (age,sex); +> + +I haven't have this case yet, might apply for some queries soon. + +>However, the order in a where clause portion doesn't really seem to +>matter, so +> +>select * from table where sex='m' and age>=38 +> +>and +> +>select * from table where age>=38 and sex='m' +> +>should both be able to use the index. +> +>also, you can use functional indexes, but the arguments in the where +>clause need the same basic form to be useful. So, if you commonly make a +>select like this: +> +>select * from table where age>50 and age<=59; +> +>then you could make a functional index like : +> +>create index table_age_50_59 on table (age) where age>50 and age<=59; +> +>However, the query +> +>select * from table where age>50 and age<=58; +> +>Wouldn't use that index, since the age <= part doesn't match up. It could +>possible use a generic index on age though, i.e. one like +> +>create index table_age on table (age); +> + +I didn't know the functional index. Thanks for the eductional information. + +>But that index will be larger than the partial one, and so the planner may +>skip using it and use a seq scan instead. Hard to say until your database +>is populated with some representational test data. +> +>Since these indexes will be only a small fraction of the total data, it +>will often be advantageous to use them with a query. +> +>After you have a set of test data, then you can start looking at tuning +>random page cost and such to make your hardware perform properly for +>individual queries. Well, hope that helps. +> +> + +I will do some fine query tuning in the final test phase. Right now, I want to make sure the table design and queries are +on the right track. + +That indeed helps. + +Thanks, + +Vernon + + + + +From pgsql-performance-owner@postgresql.org Thu Dec 5 23:14:30 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2AF6D4760D4 + for ; + Thu, 5 Dec 2002 23:14:29 -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 11821476161 + for ; + Thu, 5 Dec 2002 23:10:41 -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 gB64BjbQ084749 + for ; + Thu, 5 Dec 2002 23:11:45 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: ALTER TABLE .. < ADD | DROP > OIDS +From: Rod Taylor +To: Pgsql Performance +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-U5J8yk+fuKbWRg+PXlC7" +Organization: +Message-Id: <1039147904.72042.71.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 05 Dec 2002 23:11:45 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/51 +X-Sequence-Number: 467 + +--=-U5J8yk+fuKbWRg+PXlC7 +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +I wish to create an alter command which will allow a table to have OIDs +added or removed. + + +The tricky part appears to be changing the tuples themselves. I believe +if I pull the same trick that cluster does (create new file, copy +tuples, etc) it can be done fairly easily. + +First, set up pg_class appropriately (oid flag). + +Second, copy out tuples from oldfile to newfile, running a +heap_deformtuple() -> heap_formtuple() process on each. Since +heap_deformtuple only deals with positive numbered attributes +(non-system attributes) this should be safe to do on a mis-configured +relation. heap_formtuple completes the dirty work of setting up the OID +column appropriately. + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-U5J8yk+fuKbWRg+PXlC7 +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) + +iD8DBQA98COA6DETLow6vwwRApekAJoCuYNtAm1bfUmqNUF66ndyx4j4rQCghd6Z +YLF8oi8kpxFaIUWZeVmXdhY= +=6Hsp +-----END PGP SIGNATURE----- + +--=-U5J8yk+fuKbWRg+PXlC7-- + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 00:00:26 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 115DB4763E5 + for ; + Fri, 6 Dec 2002 00:00:26 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP id 344904763AF + for ; + Fri, 6 Dec 2002 00:00:19 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id gB650El12702; + Fri, 6 Dec 2002 00:00:14 -0500 (EST) +From: Bruce Momjian +Message-Id: <200212060500.gB650El12702@candle.pha.pa.us> +Subject: Re: ALTER TABLE .. < ADD | DROP > OIDS +In-Reply-To: <1039147904.72042.71.camel@jester> +To: Rod Taylor +Date: Fri, 6 Dec 2002 00:00:14 -0500 (EST) +Cc: Pgsql Performance +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: 200212/52 +X-Sequence-Number: 468 + + +OK, patch applied and tested. + +--------------------------------------------------------------------------- + +Rod Taylor wrote: +-- Start of PGP signed section. +> I wish to create an alter command which will allow a table to have OIDs +> added or removed. +> +> +> The tricky part appears to be changing the tuples themselves. I believe +> if I pull the same trick that cluster does (create new file, copy +> tuples, etc) it can be done fairly easily. +> +> First, set up pg_class appropriately (oid flag). +> +> Second, copy out tuples from oldfile to newfile, running a +> heap_deformtuple() -> heap_formtuple() process on each. Since +> heap_deformtuple only deals with positive numbered attributes +> (non-system attributes) this should be safe to do on a mis-configured +> relation. heap_formtuple completes the dirty work of setting up the OID +> column appropriately. +> +> -- +> Rod Taylor +> +> PGP Key: http://www.rbt.ca/rbtpub.asc +-- End of PGP section, PGP failed! + +-- + 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 Dec 6 00:10:12 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B22CF476980 + for ; + Fri, 6 Dec 2002 00:10:11 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP id 78DA34764BF + for ; + Fri, 6 Dec 2002 00:08:02 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id gB6582a13580; + Fri, 6 Dec 2002 00:08:02 -0500 (EST) +From: Bruce Momjian +Message-Id: <200212060508.gB6582a13580@candle.pha.pa.us> +Subject: Re: ALTER TABLE .. < ADD | DROP > OIDS +In-Reply-To: <200212060500.gB650El12702@candle.pha.pa.us> +To: Bruce Momjian +Date: Fri, 6 Dec 2002 00:08:02 -0500 (EST) +Cc: Rod Taylor , + Pgsql Performance +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: 200212/53 +X-Sequence-Number: 469 + +Bruce Momjian wrote: +> +> OK, patch applied and tested. + +Sorry, wrong email. I meant to say that his previous ALTER DOMAIN patch +had been applied with the new file now supplied. + + +> +> --------------------------------------------------------------------------- +> +> Rod Taylor wrote: +> -- Start of PGP signed section. +> > I wish to create an alter command which will allow a table to have OIDs +> > added or removed. +> > +> > +> > The tricky part appears to be changing the tuples themselves. I believe +> > if I pull the same trick that cluster does (create new file, copy +> > tuples, etc) it can be done fairly easily. +> > +> > First, set up pg_class appropriately (oid flag). +> > +> > Second, copy out tuples from oldfile to newfile, running a +> > heap_deformtuple() -> heap_formtuple() process on each. Since +> > heap_deformtuple only deals with positive numbered attributes +> > (non-system attributes) this should be safe to do on a mis-configured +> > relation. heap_formtuple completes the dirty work of setting up the OID +> > column appropriately. +> > +> > -- +> > Rod Taylor +> > +> > PGP Key: http://www.rbt.ca/rbtpub.asc +> -- End of PGP section, PGP failed! +> +> -- +> Bruce Momjian | http://candle.pha.pa.us +> pgman@candle.pha.pa.us | (610) 359-1001 +> + If your life is a hard drive, | 13 Roberts Road +> + Christ can be your backup. | Newtown Square, Pennsylvania 19073 +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 6: Have you searched our list archives? +> +> http://archives.postgresql.org +> + +-- + Bruce Momjian | http://candle.pha.pa.us + pgman@candle.pha.pa.us | (610) 359-1001 + + If your life is a hard drive, | 13 Roberts Road + + Christ can be your backup. | Newtown Square, Pennsylvania 19073 + +From pgsql-performance-owner@postgresql.org Fri Dec 6 06:33:23 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0C4E84763EA + for ; + Fri, 6 Dec 2002 06:33:23 -0500 (EST) +Received: from mediaexch01.mediaburst.co.uk (unknown [213.130.128.235]) + by postgresql.org (Postfix) with ESMTP id 4676C4763B0 + for ; + Fri, 6 Dec 2002 06:32:02 -0500 (EST) +content-class: urn:content-classes:message +Subject: Re: ORDER BY ... LIMIT.. performance +MIME-Version: 1.0 +Content-Type: text/plain; + charset="us-ascii" +Content-Transfer-Encoding: quoted-printable +Date: Fri, 6 Dec 2002 11:32:04 -0000 +X-MimeOLE: Produced By Microsoft Exchange V6.0.4712.0 +Message-ID: + <94B61ED0D8770A4A98A3DBD72DBBA1F82132F4@mediaexch01.mediaburst.co.uk> +X-MS-Has-Attach: +X-MS-TNEF-Correlator: +Thread-Topic: RE: [PERFORM] ORDER BY ... LIMIT.. performance +Thread-Index: AcKdGxlBaiJtI3FbQMW+89o+BxBKQw== +From: "john cartmell" +To: "Josh Berkus" , "Tom Lane" +Cc: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/54 +X-Sequence-Number: 470 + + + + +> 1) Post an EXPLAIN ANALYZE statement for the above query, with limit, +> that returns in 3-5 seconds. +> 2) Post an EXPLAIN ANALYZE for a query that returns slowly (20-30 +> seconds). + +The query: +SELECT * FROM tblcompany WHERE lower(companyname) like 'a g m%' ORDER BY +companyname; +returns 20 rows. +Its EXPLAIN ANALYZE is as follows: + NOTICE: QUERY PLAN: + + Sort (cost=3D64196.18..64196.18 rows=3D6339 width=3D224) (actual +time=3D2274.64..2274.66 rows=3D20 loops=3D1) + -> Seq Scan on tblcompany (cost=3D0.00..63795.86 rows=3D6339 +width=3D224) (actual time=3D1023.37..2274.41 rows=3D20 loops=3D1) + Total runtime: 2274.78 msec + +When limit is 19: + EXPLAIN ANALYZE SELECT * FROM tblcompany WHERE +lower(companyname) like 'a g m%' ORDER BY companyname LIMIT 19,0; + NOTICE: QUERY PLAN: + + Limit (cost=3D0.00..4621.68 rows=3D19 width=3D223) (actual +time=3D561.20..563.11 rows=3D19 loops=3D1) + -> Index Scan using idx_tblcompany_companyname on tblcompany +(cost=3D0.00..1542006.83 rows=3D6339 width=3D223) (actual time=3D561.19..56= +3.07 +rows=3D20 loops=3D1) + Total runtime: 563.22 msec + + +But when it is 20: + EXPLAIN ANALYZE SELECT * FROM tblcompany WHERE +lower(companyname) like 'a g m%' ORDER BY companyname LIMIT 20,0; + NOTICE: QUERY PLAN: + + Limit (cost=3D0.00..4864.92 rows=3D20 width=3D223) (actual +time=3D559.58..21895.02 rows=3D20 loops=3D1) + -> Index Scan using idx_tblcompany_companyname on tblcompany +(cost=3D0.00..1542006.83 rows=3D6339 width=3D223) (actual +time=3D559.57..21894.97 rows=3D20 loops=3D1) + Total runtime: 21895.13 msec + + + Admitedly the query without the limit has a different query plan +but the last two don't and yet vary wildly. + John Cartmell + + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 12:31:43 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8B13647616F + for ; + Fri, 6 Dec 2002 12:31:42 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 1B76D475EE2 + for ; + Fri, 6 Dec 2002 12:30:58 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.1) + with HTTP id 2024223 for ; + Fri, 06 Dec 2002 09:30:46 -0800 +From: "Josh Berkus" +Subject: Speeding up aggregates +To: pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.1 +Date: Fri, 06 Dec 2002 09:30:46 -0800 +Message-ID: +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: 200212/55 +X-Sequence-Number: 471 + +Folks, + +One of Postgres' poorest performing areas is aggregates. This is the +unfortunate side effect of our fully extensible aggregate and type +system. However, I thought that the folks on this list might have a +few tips on making aggregates perform faster. + +Here's mine: Aggregate Caching Table + +This is a brute-force approach. However, if you have a table with a +million records for which users *frequently* ask for grand totals or +counts, it can work fine. + +A simple example: + +Table client_case_counts ( + client_id INT NOT NULL REFERENCES clients(client_id) ON DELETE +CASCADE; + no_cases INT NOT NULL DEFAULT 0 +); + +Then create triggers: + +Function tf_maintain_client_counts () +returns opaque as ' +BEGIN +UPDATE client_case_counts SET no_cases = no_cases + 1 +WHERE client_id = NEW.client_id; +INSERT INTO client_case_counts ( client_id, no_cases ) +VALUES ( NEW.client_id, 1 ) +WHERE NOT EXISTS (SELECT client_id FROM client_case_counts ccc2 + WHERE ccc2.client_id = NEW.client_id); +RETURN NEW; +END;' LANGUAGE 'plpgsql'; + +Trigger tg_maintain_client_counts ON INSERT INTO cases +FOR EACH ROW EXECUTE tf_maintain_client_counts(); +etc. + +While effective, this approach is costly in terms of update/insert +processing. It is also limited to whatever aggregate requests you have +anticipated ... it does no good for aggregates over a user-defined +range. + +What have other Postgres users done to speed up aggregates on large +tables? + +-Josh Berkus + + + + + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 13:13:06 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 363F8476994 + for ; + Fri, 6 Dec 2002 13:13:03 -0500 (EST) +Received: from joeconway.com (unknown [63.210.180.150]) + by postgresql.org (Postfix) with ESMTP id 39E464762CF + for ; + Fri, 6 Dec 2002 13:12:25 -0500 (EST) +Received: from [206.19.64.3] (account jconway HELO joeconway.com) + by joeconway.com (CommuniGate Pro SMTP 3.5.9) + with ESMTP-TLS id 1470717; Fri, 06 Dec 2002 10:52:11 -0800 +Message-ID: <3DF0E825.7020400@joeconway.com> +Date: Fri, 06 Dec 2002 10:10:45 -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: Josh Berkus +Cc: pgsql-performance@postgresql.org +Subject: Re: Speeding up aggregates +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: 200212/56 +X-Sequence-Number: 472 + +Josh Berkus wrote: +> While effective, this approach is costly in terms of update/insert +> processing. It is also limited to whatever aggregate requests you have +> anticipated ... it does no good for aggregates over a user-defined +> range. + +I think this is where Oracle's materialized views come into play. + +> +> What have other Postgres users done to speed up aggregates on large +> tables? + +I've found that in most real life applications, expensive aggregate queries +tend to be needed for management reporting, which does not need to be based on +up-to-the-second fresh data. Normally for these types of reports a summary +through say last night at midnight is perfectly adequate. + +The simplest solution in these cases is to build a table to hold your +partially or completely summarized data, then report off of that. Use cron to +refresh these summary tables at convenient times (daily, every 2 hours, or +whatever). + +Joe + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 13:16:23 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 66A534762E3 + for ; + Fri, 6 Dec 2002 13:16:18 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP + id 26978476A47; Fri, 6 Dec 2002 13:14:05 -0500 (EST) +Received: by davinci.ethosmedia.com (CommuniGate Pro PIPE 4.0.1) + with PIPE id 2024311; Fri, 06 Dec 2002 10:13:48 -0800 +X-Spam-Status: Scanner Called +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.1) + with HTTP id 2024310; Fri, 06 Dec 2002 10:13:40 -0800 +From: "Josh Berkus" +Subject: Re: ORDER BY ... LIMIT.. performance +To: "john cartmell" , + "Josh Berkus" , "Tom Lane" +Cc: +X-Mailer: CommuniGate Pro Web Mailer v.4.0.1 +Date: Fri, 06 Dec 2002 10:13:40 -0800 +Message-ID: +In-Reply-To: + <94B61ED0D8770A4A98A3DBD72DBBA1F82132F4@mediaexch01.mediaburst.co.uk> +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +Content-Transfer-Encoding: 8bit +X-Spam-Status: No, hits=-3.1 required=6.0 tests=IN_REP_TO, ORDER_STATUS, + AWL version=2.20 +X-Spam-Level: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/57 +X-Sequence-Number: 473 + +John, + +> But when it is 20: +> EXPLAIN ANALYZE SELECT * FROM tblcompany WHERE +> lower(companyname) like 'a g m%' ORDER BY companyname LIMIT 20,0; +> NOTICE: QUERY PLAN: +> +> Limit (cost=0.00..4864.92 rows=20 width=223) (actual +> time=559.58..21895.02 rows=20 loops=1) +> -> Index Scan using idx_tblcompany_companyname on tblcompany +> (cost=0.00..1542006.83 rows=6339 width=223) (actual +> time=559.57..21894.97 rows=20 loops=1) +> Total runtime: 21895.13 msec + +That's extremely odd. From the look of it, Postgres is taking an +extra 18 seconds just to find that 20th row. + +Does this table expereince very frequent deletions and updates, or +perhaps mass record replacement from a file? Try running VACUUM FULL +ANALYZE, and possibly even REINDEX on idx_tblcompany_companyname. + Massive numbers of dead tuples could account for this performance +irregularity. + +-Josh + +From pgsql-performance-owner@postgresql.org Fri Dec 6 15:21:08 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1D117476614 + for ; + Fri, 6 Dec 2002 15:21:06 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id ED849476899 + for ; + Fri, 6 Dec 2002 15:19:03 -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 gB6KJ4pd012610; + Fri, 6 Dec 2002 15:19:04 -0500 (EST) +To: Rod Taylor +Cc: Pgsql Performance +Subject: Re: ALTER TABLE .. < ADD | DROP > OIDS +In-reply-to: <1039147904.72042.71.camel@jester> +References: <1039147904.72042.71.camel@jester> +Comments: In-reply-to Rod Taylor + message dated "05 Dec 2002 23:11:45 -0500" +Date: Fri, 06 Dec 2002 15:19:04 -0500 +Message-ID: <12609.1039205944@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/58 +X-Sequence-Number: 474 + +Rod Taylor writes: +> I wish to create an alter command which will allow a table to have OIDs +> added or removed. + +> The tricky part appears to be changing the tuples themselves. + +Are you sure you need to? Methinks the lazy approach of letting them +auto-adjust on next UPDATE should work as well for OIDs as for user +columns. + +There might be a few places that look at the pg_class.relhasoids +field where they should be examining the tuple header has-oid bit, +but I don't think there are many. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 6 15:35:48 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6F338476A38 + for ; + Fri, 6 Dec 2002 15:35:47 -0500 (EST) +Received: from jester.senspire.com (unknown [216.208.117.7]) + by postgresql.org (Postfix) with ESMTP id 4912C47616F + for ; + Fri, 6 Dec 2002 15:34:35 -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 gB6KZWeN079623; + Fri, 6 Dec 2002 15:35:32 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: ALTER TABLE .. < ADD | DROP > OIDS +From: Rod Taylor +To: Tom Lane +Cc: Pgsql Performance +In-Reply-To: <12609.1039205944@sss.pgh.pa.us> +References: <1039147904.72042.71.camel@jester> + <12609.1039205944@sss.pgh.pa.us> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-WrBgibmCewsZK2AFACUq" +Organization: +Message-Id: <1039206932.2742.85.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 06 Dec 2002 15:35:32 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/59 +X-Sequence-Number: 475 + +--=-WrBgibmCewsZK2AFACUq +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +On Fri, 2002-12-06 at 15:19, Tom Lane wrote: +> Rod Taylor writes: +> > I wish to create an alter command which will allow a table to have OIDs +> > added or removed. +>=20 +> > The tricky part appears to be changing the tuples themselves. + +> There might be a few places that look at the pg_class.relhasoids +> field where they should be examining the tuple header has-oid bit, +> but I don't think there are many. + +Ok.. If you think thats safe, I'll give it a try. I was afraid that the +system would confuse itself if the table had mix and matched tuples in +it. New tuples without oids, old tuples with. + +That helps DROP OID. How about ADD OID? + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-WrBgibmCewsZK2AFACUq +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) + +iD8DBQA98QoT6DETLow6vwwRAq2uAJ989FUZKLZ4u+w28HtBVGA5GnvuqgCfff2N +px0ogNUS6fGgm8nifO2tdzE= +=PiyK +-----END PGP SIGNATURE----- + +--=-WrBgibmCewsZK2AFACUq-- + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 15:50:17 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A43944769B1 + for ; + Fri, 6 Dec 2002 15:50:16 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 97B8C475CBC + for ; + Fri, 6 Dec 2002 15:46:19 -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 gB6Kk5pd012846; + Fri, 6 Dec 2002 15:46:05 -0500 (EST) +To: "Josh Berkus" +Cc: pgsql-performance@postgresql.org +Subject: Re: Speeding up aggregates +In-reply-to: +References: +Comments: In-reply-to "Josh Berkus" + message dated "Fri, 06 Dec 2002 09:30:46 -0800" +Date: Fri, 06 Dec 2002 15:46:05 -0500 +Message-ID: <12845.1039207565@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/60 +X-Sequence-Number: 476 + +"Josh Berkus" writes: +> What have other Postgres users done to speed up aggregates on large +> tables? + +FWIW, I've implemented hashed aggregation in CVS tip. I have not had +the time to try to benchmark it, but I'd be interested if anyone can +run some tests on 7.4devel. Eliminating the need for a SORT step +should help aggregations over large datasets. + +Note that even though there's no SORT, the sort_mem setting is used +to determine the allowable hashtable size, so a too-small sort_mem +might discourage the planner from selecting hashed aggregation. +Use EXPLAIN to see which query plan gets chosen. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 6 16:06:30 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 819DA4764CB + for ; + Fri, 6 Dec 2002 16:06:29 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id A2FC8475CE5 + for ; + Fri, 6 Dec 2002 16:04:59 -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 gB6L50pd013036; + Fri, 6 Dec 2002 16:05:00 -0500 (EST) +To: Rod Taylor +Cc: Pgsql Performance +Subject: Re: ALTER TABLE .. < ADD | DROP > OIDS +In-reply-to: <1039206932.2742.85.camel@jester> +References: <1039147904.72042.71.camel@jester> + <12609.1039205944@sss.pgh.pa.us> + <1039206932.2742.85.camel@jester> +Comments: In-reply-to Rod Taylor + message dated "06 Dec 2002 15:35:32 -0500" +Date: Fri, 06 Dec 2002 16:05:00 -0500 +Message-ID: <13034.1039208700@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/61 +X-Sequence-Number: 477 + +Rod Taylor writes: +> Ok.. If you think thats safe, I'll give it a try. I was afraid that the +> system would confuse itself if the table had mix and matched tuples in +> it. New tuples without oids, old tuples with. + +Manfred's original implementation would have failed (since it didn't +have a tuple-header hasoid bit). I think I got all the places that +should consult the header bit, but there may be some left; you'll need +to test. + +> That helps DROP OID. How about ADD OID? + +What about it? I think it'll work just like adding a column, except +that OID will probably read as 0 not NULL if the row hasn't been updated +yet. (You could probably make it read as NULL if you wanted though.) + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 6 16:24:17 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CC5B6476358 + for ; + Fri, 6 Dec 2002 16:24:16 -0500 (EST) +Received: from jester.senspire.com (unknown [216.208.117.7]) + by postgresql.org (Postfix) with ESMTP id ACB714764CF + for ; + Fri, 6 Dec 2002 16:23:03 -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 gB6LO0eN079726; + Fri, 6 Dec 2002 16:24:00 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: ALTER TABLE .. < ADD | DROP > OIDS +From: Rod Taylor +To: Tom Lane +Cc: Pgsql Performance +In-Reply-To: <13034.1039208700@sss.pgh.pa.us> +References: <1039147904.72042.71.camel@jester> + <12609.1039205944@sss.pgh.pa.us> <1039206932.2742.85.camel@jester> + <13034.1039208700@sss.pgh.pa.us> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-H82xUzXuVssYXVTNwJdE" +Organization: +Message-Id: <1039209840.2742.142.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 06 Dec 2002 16:24:00 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/62 +X-Sequence-Number: 478 + +--=-H82xUzXuVssYXVTNwJdE +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +> > That helps DROP OID. How about ADD OID? +>=20 +> What about it? I think it'll work just like adding a column, except +> that OID will probably read as 0 not NULL if the row hasn't been updated +> yet. (You could probably make it read as NULL if you wanted though.) + +Good point. I forgot new columns were empty by default. + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-H82xUzXuVssYXVTNwJdE +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) + +iD8DBQA98RVv6DETLow6vwwRAg/XAJ9MMd4a8HfeV6Za8FlDCAtbTTS58QCZAQTb +eHGSTCaOwx8OFWomrnpd6RM= +=OALq +-----END PGP SIGNATURE----- + +--=-H82xUzXuVssYXVTNwJdE-- + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 16:29:46 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A683F47620C + for ; + Fri, 6 Dec 2002 16:29:45 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 715784760A9 + for ; + Fri, 6 Dec 2002 16:28:20 -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 gB6LSIpd013211; + Fri, 6 Dec 2002 16:28:18 -0500 (EST) +To: "john cartmell" +Cc: "Josh Berkus" , + pgsql-performance@postgresql.org +Subject: Re: ORDER BY ... LIMIT.. performance +In-reply-to: + <94B61ED0D8770A4A98A3DBD72DBBA1F82132F4@mediaexch01.mediaburst.co.uk> +References: + <94B61ED0D8770A4A98A3DBD72DBBA1F82132F4@mediaexch01.mediaburst.co.uk> +Comments: In-reply-to "john cartmell" + message dated "Fri, 06 Dec 2002 11:32:04 +0000" +Date: Fri, 06 Dec 2002 16:28:18 -0500 +Message-ID: <13210.1039210098@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/63 +X-Sequence-Number: 479 + +"john cartmell" writes: +> The query: +> SELECT * FROM tblcompany WHERE lower(companyname) like 'a g m%' ORDER BY +> companyname; +> returns 20 rows. + ^^^^^^^^^^^^^^^ + +Ahh, light dawns. + +> When limit is 19: +> EXPLAIN ANALYZE SELECT * FROM tblcompany WHERE +> lower(companyname) like 'a g m%' ORDER BY companyname LIMIT 19,0; +> NOTICE: QUERY PLAN: + +> Limit (cost=0.00..4621.68 rows=19 width=223) (actual +> time=561.20..563.11 rows=19 loops=1) +> -> Index Scan using idx_tblcompany_companyname on tblcompany +> (cost=0.00..1542006.83 rows=6339 width=223) (actual time=561.19..563.07 +> rows=20 loops=1) +> Total runtime: 563.22 msec + +> But when it is 20: +> EXPLAIN ANALYZE SELECT * FROM tblcompany WHERE +> lower(companyname) like 'a g m%' ORDER BY companyname LIMIT 20,0; +> NOTICE: QUERY PLAN: + +> Limit (cost=0.00..4864.92 rows=20 width=223) (actual +> time=559.58..21895.02 rows=20 loops=1) +> -> Index Scan using idx_tblcompany_companyname on tblcompany +> (cost=0.00..1542006.83 rows=6339 width=223) (actual +> time=559.57..21894.97 rows=20 loops=1) +> Total runtime: 21895.13 msec + +The problem here is that in current releases, the Limit plan node tries +to fetch one more row than requested (you can see this in the actual +rowcounts for the first example). So in your second example, the base +indexscan is actually being run to completion before the Limit gives up. +And since that scan is being used for ordering, not for implementing the +WHERE clause, it visits all the rows. (When you leave off LIMIT, the +planner chooses a plan that's more amenable to fetching all the data...) + +I recently revised the Limit logic so that it doesn't fetch the extra +row. This takes more code, but you're not the first to complain of +the old behavior. It'll be in 7.4, or if you're brave you could +probably apply the diff to 7.3. + +In the meantime, a more appropriate query would be + +SELECT * FROM tblcompany +WHERE lower(companyname) like 'a g m%' +ORDER BY lower(companyname) +LIMIT whatever + +so that an index on lower(companyname) could be used both for the WHERE +clause and for the ordering. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 6 16:34:26 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 346134760CE + for ; + Fri, 6 Dec 2002 16:34:25 -0500 (EST) +Received: from rh72.home.ee (adsl1030.estpak.ee [213.168.29.11]) + by postgresql.org (Postfix) with ESMTP id 7CBA3476603 + for ; + Fri, 6 Dec 2002 16:32:32 -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 gB6LWCum002101; + Sat, 7 Dec 2002 02:32:12 +0500 +Received: (from hannu@localhost) + by rh72.home.ee (8.12.5/8.12.5/Submit) id gB6LW6A5002099; + Sat, 7 Dec 2002 02:32:06 +0500 +X-Authentication-Warning: rh72.home.ee: hannu set sender to hannu@tm.ee using + -f +Subject: Re: Speeding up aggregates +From: Hannu Krosing +To: Tom Lane +Cc: Josh Berkus , pgsql-performance@postgresql.org +In-Reply-To: <12845.1039207565@sss.pgh.pa.us> +References: + <12845.1039207565@sss.pgh.pa.us> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039210325.2069.9.camel@rh72.home.ee> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 07 Dec 2002 02:32:06 +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/64 +X-Sequence-Number: 480 + +Tom Lane kirjutas L, 07.12.2002 kell 01:46: +> "Josh Berkus" writes: +> > What have other Postgres users done to speed up aggregates on large +> > tables? +> +> FWIW, I've implemented hashed aggregation in CVS tip. + +Great! + +This should also make it easier to implement all kinds of GROUP BY +ROLLUP|CUBE|GROUPING SETS|() queries. + +Do you have any near-term plans for doing them ? + +> I have not had +> the time to try to benchmark it, but I'd be interested if anyone can +> run some tests on 7.4devel. Eliminating the need for a SORT step +> should help aggregations over large datasets. + +Is there a variable to set that would disable one or another, like we +currently have for disabling various join strategies ? + +> Note that even though there's no SORT, the sort_mem setting is used +> to determine the allowable hashtable size, so a too-small sort_mem +> might discourage the planner from selecting hashed aggregation. + +Do you mean that hashed aggregation can't overflow to disk, or would it +just be too slow ? + +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Fri Dec 6 16:43:03 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B7921476614 + for ; + Fri, 6 Dec 2002 16:43:01 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 93377476296 + for ; + Fri, 6 Dec 2002 16:42:46 -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 gB6Lgkpd013360; + Fri, 6 Dec 2002 16:42:46 -0500 (EST) +To: Hannu Krosing +Cc: Josh Berkus , pgsql-performance@postgresql.org +Subject: Re: Speeding up aggregates +In-reply-to: <1039210325.2069.9.camel@rh72.home.ee> +References: + <12845.1039207565@sss.pgh.pa.us> + <1039210325.2069.9.camel@rh72.home.ee> +Comments: In-reply-to Hannu Krosing + message dated "07 Dec 2002 02:32:06 +0500" +Date: Fri, 06 Dec 2002 16:42:46 -0500 +Message-ID: <13359.1039210966@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/65 +X-Sequence-Number: 481 + +Hannu Krosing writes: +> This should also make it easier to implement all kinds of GROUP BY +> ROLLUP|CUBE|GROUPING SETS|() queries. + +> Do you have any near-term plans for doing them ? + +Not me. + +> Is there a variable to set that would disable one or another, like we +> currently have for disabling various join strategies ? + +enable_hashagg. I didn't think about one to prevent the old style. + +>> Note that even though there's no SORT, the sort_mem setting is used +>> to determine the allowable hashtable size, so a too-small sort_mem +>> might discourage the planner from selecting hashed aggregation. + +> Do you mean that hashed aggregation can't overflow to disk, or would it +> just be too slow ? + +I didn't write any code to let it overflow to disk --- didn't seem +likely to be useful. (You're probably better off with a sort-based +aggregation if there are too many distinct grouping keys.) + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 6 16:50:45 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1AEF847607D + for ; + Fri, 6 Dec 2002 16:50:45 -0500 (EST) +Received: from rh72.home.ee (adsl1030.estpak.ee [213.168.29.11]) + by postgresql.org (Postfix) with ESMTP id 401E0476603 + for ; + Fri, 6 Dec 2002 16:50:01 -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 gB6Lnwum002271; + Sat, 7 Dec 2002 02:49:59 +0500 +Received: (from hannu@localhost) + by rh72.home.ee (8.12.5/8.12.5/Submit) id gB6LnwCI002269; + Sat, 7 Dec 2002 02:49:58 +0500 +X-Authentication-Warning: rh72.home.ee: hannu set sender to hannu@tm.ee using + -f +Subject: Re: Speeding up aggregates +From: Hannu Krosing +To: Tom Lane +Cc: Josh Berkus , pgsql-performance@postgresql.org +In-Reply-To: <1039210325.2069.9.camel@rh72.home.ee> +References: + <12845.1039207565@sss.pgh.pa.us> <1039210325.2069.9.camel@rh72.home.ee> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039211397.2067.18.camel@rh72.home.ee> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 07 Dec 2002 02:49:58 +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/66 +X-Sequence-Number: 482 + +Hannu Krosing kirjutas L, 07.12.2002 kell 02:32: +> Tom Lane kirjutas L, 07.12.2002 kell 01:46: +> > "Josh Berkus" writes: +> > > What have other Postgres users done to speed up aggregates on large +> > > tables? +> > +> > FWIW, I've implemented hashed aggregation in CVS tip. +> +> Great! +> +> This should also make it easier to implement all kinds of GROUP BY +> ROLLUP|CUBE|GROUPING SETS|() queries. + +Of these only ROLLUP can be done in one scan after sort, all others +would generally require several scans without hashing. + + +I just noticed that we don't even have a TODO for this. I think this +would be a good TODO item. + +Bruce, could you add: + +* Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY + + +They are all defined in SQL99 p.79 + + +Some more background info (from a quick Google search) + +a very short overview: + http://www.neddo.com/dm3e/sql3&olap.html + + +more thorough guide for DB2: +http://www.student.math.uwaterloo.ca/~cs448/db2_doc/html/db2s0/frame3.htm#db2s0279 + + +----------------- +Hannu + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 16:55:55 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B4C014760A9 + for ; + Fri, 6 Dec 2002 16:55:53 -0500 (EST) +Received: from rh72.home.ee (adsl1030.estpak.ee [213.168.29.11]) + by postgresql.org (Postfix) with ESMTP id 045234768EF + for ; + Fri, 6 Dec 2002 16:55:47 -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 gB6Ltium002290; + Sat, 7 Dec 2002 02:55:44 +0500 +Received: (from hannu@localhost) + by rh72.home.ee (8.12.5/8.12.5/Submit) id gB6LtiNK002288; + Sat, 7 Dec 2002 02:55:44 +0500 +X-Authentication-Warning: rh72.home.ee: hannu set sender to hannu@tm.ee using + -f +Subject: Re: Speeding up aggregates +From: Hannu Krosing +To: Tom Lane +Cc: Josh Berkus , pgsql-performance@postgresql.org +In-Reply-To: <13359.1039210966@sss.pgh.pa.us> +References: + <12845.1039207565@sss.pgh.pa.us> <1039210325.2069.9.camel@rh72.home.ee> + <13359.1039210966@sss.pgh.pa.us> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039211743.2069.25.camel@rh72.home.ee> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 07 Dec 2002 02:55:44 +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/68 +X-Sequence-Number: 484 + +Tom Lane kirjutas L, 07.12.2002 kell 02:42: +> Hannu Krosing writes: +> > This should also make it easier to implement all kinds of GROUP BY +> > ROLLUP|CUBE|GROUPING SETS|() queries. +> +> > Do you have any near-term plans for doing them ? +> +> Not me. + +I'll try to look into it then. + +No promises about when it will be ready ;) + +> > Is there a variable to set that would disable one or another, like we +> > currently have for disabling various join strategies ? +> +> enable_hashagg. I didn't think about one to prevent the old style. +> +> >> Note that even though there's no SORT, the sort_mem setting is used +> >> to determine the allowable hashtable size, so a too-small sort_mem +> >> might discourage the planner from selecting hashed aggregation. +> +> > Do you mean that hashed aggregation can't overflow to disk, or would it +> > just be too slow ? +> +> I didn't write any code to let it overflow to disk --- didn't seem +> likely to be useful. (You're probably better off with a sort-based +> aggregation if there are too many distinct grouping keys.) + +For simple GROUP BY this is most likely so, but for CUBE or GROUPING SETS +it may still be faster to overflow to disk than to do N passes over data +different ordering. + +Of course we could use a combined approach here - do it the old way (sort) for +main body + run a parallel hashed aggregation for other, out of order groups. + +------------ +Hannu + + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 16:58:55 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2F6C04760A9 + for ; + Fri, 6 Dec 2002 16:58:54 -0500 (EST) +Received: from rh72.home.ee (adsl1030.estpak.ee [213.168.29.11]) + by postgresql.org (Postfix) with ESMTP id 10311476B04 + for ; + Fri, 6 Dec 2002 16:57:34 -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 gB6LvWum002305; + Sat, 7 Dec 2002 02:57:32 +0500 +Received: (from hannu@localhost) + by rh72.home.ee (8.12.5/8.12.5/Submit) id gB6LvVVt002303; + Sat, 7 Dec 2002 02:57:31 +0500 +X-Authentication-Warning: rh72.home.ee: hannu set sender to hannu@tm.ee using + -f +Subject: Re: Speeding up aggregates +From: Hannu Krosing +To: Tom Lane +Cc: Josh Berkus , pgsql-performance@postgresql.org +In-Reply-To: <13359.1039210966@sss.pgh.pa.us> +References: + <12845.1039207565@sss.pgh.pa.us> <1039210325.2069.9.camel@rh72.home.ee> + <13359.1039210966@sss.pgh.pa.us> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039211851.2069.27.camel@rh72.home.ee> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 07 Dec 2002 02:57:31 +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/69 +X-Sequence-Number: 485 + +Tom Lane kirjutas L, 07.12.2002 kell 02:42: +> Hannu Krosing writes: +> > Is there a variable to set that would disable one or another, like we +> > currently have for disabling various join strategies ? +> +> enable_hashagg. I didn't think about one to prevent the old style. + +could be handy for testing. + +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Fri Dec 6 16:55:24 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 283414760CE + for ; + Fri, 6 Dec 2002 16:55:23 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id F0184476735 + for ; + Fri, 6 Dec 2002 16:54:46 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2270105; Fri, 06 Dec 2002 13:54:32 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Tom Lane +Subject: Re: Speeding up aggregates +Date: Fri, 6 Dec 2002 13:58:02 -0800 +X-Mailer: KMail [version 1.4] +Cc: pgsql-performance@postgresql.org +References: + <12845.1039207565@sss.pgh.pa.us> +In-Reply-To: <12845.1039207565@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212061358.03002.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/67 +X-Sequence-Number: 483 + + +Tom, + +> FWIW, I've implemented hashed aggregation in CVS tip. I have not had +> the time to try to benchmark it, but I'd be interested if anyone can +> run some tests on 7.4devel. Eliminating the need for a SORT step +> should help aggregations over large datasets. + +I'd love to, but I am still too much of a tyro to build Postgres from CVS.= +=20=20=20 +As soon as there's a tarball of 7.4devel, I'll build it and run comparisons. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 18:07:09 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 655DF4760A9 + for ; + Fri, 6 Dec 2002 18:07:08 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 9FA8C47607D + for ; + Fri, 6 Dec 2002 18:07:07 -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 gB6N78pd013970; + Fri, 6 Dec 2002 18:07:08 -0500 (EST) +To: josh@agliodbs.com +Cc: pgsql-performance@postgresql.org +Subject: Re: Speeding up aggregates +In-reply-to: <200212061358.03002.josh@agliodbs.com> +References: + <12845.1039207565@sss.pgh.pa.us> + <200212061358.03002.josh@agliodbs.com> +Comments: In-reply-to Josh Berkus + message dated "Fri, 06 Dec 2002 13:58:02 -0800" +Date: Fri, 06 Dec 2002 18:07:08 -0500 +Message-ID: <13969.1039216028@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/70 +X-Sequence-Number: 486 + +Josh Berkus writes: +> I'd love to, but I am still too much of a tyro to build Postgres from CVS. +> As soon as there's a tarball of 7.4devel, I'll build it and run comparisons. + +There should be a nightly snapshot tarball on the FTP server. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 6 18:33:10 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A2DA1476967 + for ; + Fri, 6 Dec 2002 18:33:09 -0500 (EST) +Received: from office.nextbus.com (ns.nextbus.com [64.164.28.194]) + by postgresql.org (Postfix) with ESMTP id 0C8F8476ABD + for ; + Fri, 6 Dec 2002 18:32:00 -0500 (EST) +Received: from visor.corp.nextbus.com (visor.corp.nextbus.com [192.168.1.109]) + by office.nextbus.com (Postfix) with ESMTP id 7DD4D4F87B + for ; + Fri, 6 Dec 2002 15:32:00 -0800 (PST) +Received: from localhost (laurette@localhost) + by visor.corp.nextbus.com (8.11.2/8.8.7) with ESMTP id gB6NW1h07899 + for ; Fri, 6 Dec 2002 15:32:01 -0800 +X-Authentication-Warning: visor.corp.nextbus.com: laurette owned process doing + -bs +Date: Fri, 6 Dec 2002 15:32:01 -0800 (PST) +From: Laurette Cisneros +X-X-Sender: laurette@visor.corp.nextbus.com +To: pgsql-performance@postgresql.org +Subject: query question +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/71 +X-Sequence-Number: 487 + + +Silly question (and just because I would like to know exactly why): + +This query: +select distinct x, y + from table1 t + join table2 t2 + using (col1) +order by x; + +is *slower* than this query: + +select disting x, y + from table1 + where col1 = (select col1 from table2) +ORDER BY x; + +Is this because in the latter case the select col1 is cached? + +Ooo, I would love to have a web page full of these tidbits (along with how +to get around the max and min aggregates and why as an example..., etc.)! + +Thanks, + +-- +Laurette Cisneros +The Database Group +(510) 420-3137 +NextBus Information Systems, Inc. +www.nextbus.com +---------------------------------- +There is more to life than just SQL. + + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 19:35:39 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 858E24760F8 + for ; + Fri, 6 Dec 2002 19:35:37 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 1A9EE47649B + for ; + Fri, 6 Dec 2002 19:35:01 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2270420; Fri, 06 Dec 2002 16:34:47 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Laurette Cisneros , pgsql-performance@postgresql.org +Subject: Re: query question +Date: Fri, 6 Dec 2002 16:38:18 -0800 +X-Mailer: KMail [version 1.4] +References: +In-Reply-To: +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212061638.18529.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/72 +X-Sequence-Number: 488 + + +Laurette, + +> This query: +> select distinct x, y=20 +> from table1 t=20 +> join table2 t2 +> using (col1)=20 +> order by x; +>=20 +> is *slower* than this query: +>=20 +> select disting x, y=20 +> from table1=20 +> where col1 =3D (select col1 from table2)=20 +> ORDER BY x; +>=20 +> Is this because in the latter case the select col1 is cached? + +Yes. For all of the following structures: + +where x =3D (select col from table) +where x IN (select col from table) +where x NOT IN (select col from table) +where x !=3D ANY(select col from table) +etc., + +... Postgres must process the full subquery, return the results, and compar= +e=20 +all of the results as individual values against the reference column.=20=20 + +However, if you re-wrote the query as: + + select distint x, y=20 + from table1=20 + where EXISTS (select col1 from table2 + where table2.col1 =3D table1.col1) + ORDER BY x; + +... then Postgres would be able to use JOIN optimizations to evaluate the= +=20 +subquery and pull a subset of relevant records or even use an index, making= +=20 +the query *much* faster. + +> Ooo, I would love to have a web page full of these tidbits (along with ho= +w=20 +> to get around the max and min aggregates and why as an example..., etc.)! + +Um: + +http://techdocs.postgresql.org/guides/ + +Add your own Wiki page! + + +--=20 +-Josh Berkus + +______AGLIO DATABASE SOLUTIONS___________________________ + Josh Berkus + Complete information technology josh@agliodbs.com + and data management solutions (415) 565-7293 + for law firms, small businesses fax 621-2533 + and non-profit organizations. San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 20:51:27 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 66ED0475D0D + for ; + Fri, 6 Dec 2002 20:51:25 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id C809E475B84 + for ; + Fri, 6 Dec 2002 20:51:24 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2270581; Fri, 06 Dec 2002 17:51:13 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: Tom Lane +Subject: Re: Speeding up aggregates +Date: Fri, 6 Dec 2002 17:54:43 -0800 +X-Mailer: KMail [version 1.4] +Cc: pgsql-performance@postgresql.org +References: + <200212061358.03002.josh@agliodbs.com> + <13969.1039216028@sss.pgh.pa.us> +In-Reply-To: <13969.1039216028@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212061754.43566.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/73 +X-Sequence-Number: 489 + + +Tom, + +We have a winner on simple aggregates: + +Version 7.2.3: + explain analyze select client_id, count(*) from case_clients group by=20 +client_id; +NOTICE: QUERY PLAN: + +Aggregate (cost=3D11892.51..12435.75 rows=3D10865 width=3D4) (actual=20 +time=3D1162.27..1569.40 rows=3D436 loops=3D1) + -> Group (cost=3D11892.51..12164.13 rows=3D108648 width=3D4) (actual=20 +time=3D1162.24..1477.70 rows=3D108648 loops=3D1) + -> Sort (cost=3D11892.51..11892.51 rows=3D108648 width=3D4) (actu= +al=20 +time=3D1162.22..1280.64 rows=3D108648 loops=3D1) + -> Seq Scan on case_clients (cost=3D0.00..2804.48 rows=3D10= +8648=20 +width=3D4) (actual time=3D0.07..283.14 rows=3D108648 loops=3D1) +Total runtime: 2387.87 msec + +Versus Version 7.4devel: +explain analyze select client_id, count(*) from case_clients group by=20 +client_id; + QUERY PLAN +---------------------------------------------------------------------------= +---------------------------------------------- + HashAggregate (cost=3D3289.72..3289.84 rows=3D46 width=3D4) (actual=20 +time=3D447.80..448.71 rows=3D436 loops=3D1) + -> Seq Scan on case_clients (cost=3D0.00..2746.48 rows=3D108648 width= +=3D4)=20 +(actual time=3D0.08..267.45 rows=3D108648 loops=3D1) + Total runtime: 473.77 msec +(3 rows) + +However, more complex queries involving aggregates seem to be unable to mak= +e=20 +use of the hashaggregate. I'll get back to you when I know what the=20 +breakpoint is. + +--=20 +-Josh Berkus + +______AGLIO DATABASE SOLUTIONS___________________________ + Josh Berkus + Complete information technology josh@agliodbs.com + and data management solutions (415) 565-7293 + for law firms, small businesses fax 621-2533 + and non-profit organizations. San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Dec 6 21:22:19 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9E2E547603C + for ; + Fri, 6 Dec 2002 21:22:18 -0500 (EST) +Received: from mail.digicamp.com (ns1.digicamp.com [216.38.142.76]) + by postgresql.org (Postfix) with SMTP id D7F38476027 + for ; + Fri, 6 Dec 2002 21:22:17 -0500 (EST) +Received: (qmail 15722 invoked from network); 7 Dec 2002 02:16:43 -0000 +Received: from localhost (HELO digicamp.com) (127.0.0.1) + by localhost with SMTP; 7 Dec 2002 02:16:43 -0000 +Received: from 168.103.211.137 + (SquirrelMail authenticated user fred@digicamp.com) + by mail.digicamp.com with HTTP; Fri, 6 Dec 2002 18:16:43 -0800 (PST) +Message-ID: <64850.168.103.211.137.1039227403.squirrel@mail.digicamp.com> +Date: Fri, 6 Dec 2002 18:16:43 -0800 (PST) +Subject: Query optimization +From: "Fred Moyer" +To: +X-XheaderVersion: 1.1 +X-UserAgent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X; en-US; + rv:1.0.1) Gecko/20021104 Chimera/0.6 +X-Priority: 3 +Importance: Normal +Cc: +Reply-To: fred@digicamp.com +X-Mailer: SquirrelMail (version 1.2.8) +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: 200212/74 +X-Sequence-Number: 490 + +Greetings! + +I am trying to find a way to optimize this query and have hit a wall. The +database size is 2.9 GB and contains 1 million records. The system is a +dual xeon 1 ghz P3 with 4 GB ram, 2 of it shared memory. Redhat linux +kernel 2.4.18-5 ext3fs. + +I'm hoping I haven't hit the limit of the hardware or os but here's all +the relevant info. Questions, comments, solutions would be greatly +appreciated. + +11696 postgres 25 0 1084M 1.1G 562M R 99.9 28.6 2:36 postmaster + +Postgresql.conf settings +shared_buffers = 250000 +sort_mem = 1048576 # min 32 +vacuum_mem = 128000 # min 1024 +wal_files = 64 # range 0-64 +enable_seqscan = false +enable_indexscan = true +enable_tidscan = true +enable_sort = true +enable_nestloop = true +enable_mergejoin = true +enable_hashjoin = true + +[postgres@db1 base]$ cat /proc/sys/kernel/shmmax +2192000000 + +database=# explain analyze SELECT active,registrant,name FROM person WHERE +object.active = 1 AND object.registrant = 't' ORDER BY UPPER(object.name) +DESC LIMIT 10 OFFSET 0; +NOTICE: QUERY PLAN: + +Limit (cost=nan..nan rows=10 width=2017) (actual +time=204790.82..204790.84 rows=10 loops=1) + -> Sort (cost=nan..nan rows=1032953 width=2017) (actual +time=204790.81..204790.82 rows=11 loops=1) + -> Index Scan using registrant__object__idx on object +(cost=0.00..81733.63 rows=1032953 width=2017) (actual +time=0.14..94509.14 rows=1032946 loops=1) +Total runtime: 205125.75 msec + +NOTICE: QUERY PLAN: + +Limit (cost=nan..nan rows=10 width=2017) (actual +time=204790.82..204790.84 rows=10 loops=1) + -> Sort (cost=nan..nan rows=1032953 width=2017) (actual +time=204790.81..204790.82 rows=11 loops=1) + -> Index Scan using registrant__object__idx on object +(cost=0.00..81733.63 rows=1032953 width=2017) (actual +time=0.14..94509.14 rows=1032946 loops=1) +Total runtime: 205125.75 msec + + + +From pgsql-performance-owner@postgresql.org Sat Dec 7 10:48:34 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C1217475BF9 + for ; + Sat, 7 Dec 2002 10:48:32 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id 1D8A8475AD7 + for ; + Sat, 7 Dec 2002 10:48:32 -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 <20021207154837.NTAC2204.lakemtao03.cox.net@[192.168.1.1]> + for ; + Sat, 7 Dec 2002 10:48:37 -0500 +Subject: Re: Speeding up aggregates +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <12845.1039207565@sss.pgh.pa.us> +References: + <12845.1039207565@sss.pgh.pa.us> +Content-Type: text/plain +Organization: +Message-Id: <1039276116.17192.4.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 07 Dec 2002 09:48:36 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/75 +X-Sequence-Number: 491 + +On Fri, 2002-12-06 at 14:46, Tom Lane wrote: +> "Josh Berkus" writes: +> > What have other Postgres users done to speed up aggregates on large +> > tables? +> +> FWIW, I've implemented hashed aggregation in CVS tip. I have not had +> the time to try to benchmark it, but I'd be interested if anyone can +> run some tests on 7.4devel. Eliminating the need for a SORT step +> should help aggregations over large datasets. +> +> Note that even though there's no SORT, the sort_mem setting is used +> to determine the allowable hashtable size, so a too-small sort_mem +> might discourage the planner from selecting hashed aggregation. +> Use EXPLAIN to see which query plan gets chosen. + +Hi. + +What exactly is "hashed aggregation"? + +>From Josh Berkus' email with the EXPLAIN data, it still looks like +supporting indexes aren't used, so are you still scanning the table? + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "they love our milk and honey, but preach about another | +| way of living" | +| Merle Haggard, "The Fighting Side Of Me" | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Sat Dec 7 12:15:25 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B54B4475A71 + for ; + Sat, 7 Dec 2002 12:15:24 -0500 (EST) +Received: from anchor-post-39.mail.demon.net (anchor-post-39.mail.demon.net + [194.217.242.80]) + by postgresql.org (Postfix) with ESMTP id C3907476094 + for ; + Sat, 7 Dec 2002 12:15:02 -0500 (EST) +Received: from mwynhau.demon.co.uk ([193.237.186.96] + helo=mainbox.archonet.com) + by anchor-post-39.mail.demon.net with esmtp (Exim 3.36 #2) + id 18KiXj-0005qp-0U; Sat, 07 Dec 2002 17:15:07 +0000 +Received: from localhost (localhost.localdomain [127.0.0.1]) + by mainbox.archonet.com (Postfix) with ESMTP + id A559517A86; Sat, 7 Dec 2002 17:13:09 +0000 (GMT) +Received: from client.archonet.com (client.archonet.com [192.168.1.16]) + by mainbox.archonet.com (Postfix) with ESMTP + id 10B33179C1; Sat, 7 Dec 2002 17:13:09 +0000 (GMT) +Content-Type: text/plain; + charset="iso-8859-1" +From: Richard Huxton +Organization: Archonet Ltd +To: fred@digicamp.com, +Subject: Re: Query optimization +Date: Sat, 7 Dec 2002 17:13:08 +0000 +User-Agent: KMail/1.4.3 +Cc: +References: <64850.168.103.211.137.1039227403.squirrel@mail.digicamp.com> +In-Reply-To: <64850.168.103.211.137.1039227403.squirrel@mail.digicamp.com> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212071713.09092.dev@archonet.com> +X-Virus-Scanned: by AMaViS snapshot-20020531 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/76 +X-Sequence-Number: 492 + +On Saturday 07 Dec 2002 2:16 am, Fred Moyer wrote: +> +> database=3D# explain analyze SELECT active,registrant,name FROM person WH= +ERE +> object.active =3D 1 AND object.registrant =3D 't' ORDER BY UPPER(object.n= +ame) +> DESC LIMIT 10 OFFSET 0; +> NOTICE: QUERY PLAN: + +What's the connection between "person" and "object"? Looks like an=20 +unconstrained join from here. Schema and count(*) for both and details of= +=20 +indexes would be useful. + +> Limit (cost=3Dnan..nan rows=3D10 width=3D2017) (actual + ^^^^^^^^ +Never seen this "nan" before - presumably Not A Number, but I don't know wh= +y=20 +the planner generates it + +> time=3D204790.82..204790.84 rows=3D10 loops=3D1) +> -> Sort (cost=3Dnan..nan rows=3D1032953 width=3D2017) (actual +> time=3D204790.81..204790.82 rows=3D11 loops=3D1) +> -> Index Scan using registrant__object__idx on object +> (cost=3D0.00..81733.63 rows=3D1032953 width=3D2017) (actual +> time=3D0.14..94509.14 rows=3D1032946 loops=3D1) +> Total runtime: 205125.75 msec + +Without seeing schema details difficult to suggest much. If it's this=20 +particular query that's the problem you might try a partial index + +CREATE INDEX foo_object_idx ON object (upper(object.name)) WHERE active=3D1= + AND=20 +registrant=3D't'; + +See CREATE INDEX in the manuals for details. + +--=20 + Richard Huxton + +From pgsql-performance-owner@postgresql.org Sat Dec 7 15:16:39 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9CB6D47592C + for ; + Sat, 7 Dec 2002 15:16:36 -0500 (EST) +Received: from mail.digicamp.com (ns1.digicamp.com [216.38.142.76]) + by postgresql.org (Postfix) with SMTP id 7E36E4758F1 + for ; + Sat, 7 Dec 2002 15:16:35 -0500 (EST) +Received: (qmail 13615 invoked from network); 7 Dec 2002 20:10:41 -0000 +Received: from localhost (HELO digicamp.com) (127.0.0.1) + by localhost with SMTP; 7 Dec 2002 20:10:41 -0000 +Received: from 168.103.211.137 + (SquirrelMail authenticated user fred@digicamp.com) + by mail.digicamp.com with HTTP; Sat, 7 Dec 2002 12:10:41 -0800 (PST) +Message-ID: <55900.168.103.211.137.1039291841.squirrel@mail.digicamp.com> +Date: Sat, 7 Dec 2002 12:10:41 -0800 (PST) +Subject: Re: Query optimization +From: "Fred Moyer" +To: +X-XheaderVersion: 1.1 +X-UserAgent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X; en-US; + rv:1.0.1) Gecko/20021104 Chimera/0.6 +In-Reply-To: <200212071713.09092.dev@archonet.com> +References: <64850.168.103.211.137.1039227403.squirrel@mail.digicamp.com> + <200212071713.09092.dev@archonet.com> +X-Priority: 3 +Importance: Normal +Cc: , +Reply-To: fred@digicamp.com +X-Mailer: SquirrelMail (version 1.2.8) +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: 200212/77 +X-Sequence-Number: 493 + +Ikes, they are the same, a cut and paste error. Sorry about that. No +joins involved, one table with 1 million records, about 255 rows, only +about 10% of the rows contain data in this particular instance. + +object is indexed on active, registrant, and name as well as UPPER(name). +Postgres version is 7.2.3 + +Here is the relevant table info (some schema details omitted for brevity) + +id | numeric(10,0) | not null default +nextval('seq_object' +::text) +name | character varying(64) | +registrant | boolean | +active | numeric(1,0) | not null default 1 + +registrant__object__idx +active__object__idx, +name__object__idx, +upper_name__object__idx, +id__object__idx, +Primary key: pk_object__id + +db=# select count(*) from count; + count +--------- + 1032953 +(1 row) + +db=# explain analyze select count(*) from object; +NOTICE: QUERY PLAN: + +Aggregate (cost=100073270.91..100073270.91 rows=1 width=0) (actual +time=3085.51..3085.51 rows=1 loops=1) + -> Seq Scan on object (cost=100000000.00..100070688.53 rows=1032953 +width=0) (actual time=0.01..2008.51 rows=1032953 loops=1) +Total runtime: 3085.62 msec + +EXPLAIN + +> On Saturday 07 Dec 2002 2:16 am, Fred Moyer wrote: +>> +>> database=# explain analyze SELECT active,registrant,name FROM object +>> WHERE object.active = 1 AND object.registrant = 't' ORDER BY +>> UPPER(object.name) DESC LIMIT 10 OFFSET 0; +>> NOTICE: QUERY PLAN: +> +> What's the connection between "person" and "object"? Looks like an +> unconstrained join from here. Schema and count(*) for both and details +> of indexes would be useful. +> +>> Limit (cost=nan..nan rows=10 width=2017) (actual +> ^^^^^^^^ +> Never seen this "nan" before - presumably Not A Number, but I don't know +> why the planner generates it +> +>> time=204790.82..204790.84 rows=10 loops=1) +>> -> Sort (cost=nan..nan rows=1032953 width=2017) (actual +>> time=204790.81..204790.82 rows=11 loops=1) +>> -> Index Scan using registrant__object__idx on object +>> (cost=0.00..81733.63 rows=1032953 width=2017) (actual +>> time=0.14..94509.14 rows=1032946 loops=1) +>> Total runtime: 205125.75 msec +> +> Without seeing schema details difficult to suggest much. If it's this +> particular query that's the problem you might try a partial index +> +> CREATE INDEX foo_object_idx ON object (upper(object.name)) WHERE +> active=1 AND registrant='t'; +> +> See CREATE INDEX in the manuals for details. +> +> -- +> Richard Huxton +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 6: Have you searched our list archives? +> +> http://archives.postgresql.org + + +Fred Moyer +Digital Campaigns, Inc. + + + +From pgsql-performance-owner@postgresql.org Sat Dec 7 15:43:02 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0842A47611C + for ; + Sat, 7 Dec 2002 15:42:58 -0500 (EST) +Received: from ns1.tudelft.nl (ns1.tudelft.nl [130.161.180.1]) + by postgresql.org (Postfix) with ESMTP id E24F5475AAC + for ; + Sat, 7 Dec 2002 15:41:59 -0500 (EST) +Received: from CONVERSION-DAEMON.mailhost2.tudelft.nl by mailhost2.tudelft.nl + (PMDF V6.1-1 #40925) id <0H6R00A01O5YBN@mailhost2.tudelft.nl> for + pgsql-performance@postgresql.org; Sat, 07 Dec 2002 21:42:00 +0100 (MET) +Received: from listserv.tudelft.nl (listserv.tudelft.nl [130.161.180.33]) + by mailhost2.tudelft.nl (PMDF V6.1-1 #40925) + with ESMTP id <0H6R007AWO5Y35@mailhost2.tudelft.nl>; Sat, + 07 Dec 2002 21:41:58 +0100 (MET) +Received: from oli.tudelft.nl (oli244.rolahola.tudelft.nl [130.161.67.244]) + by listserv.tudelft.nl (8.12.5/8.12.5) with ESMTP id gB7KfvFx009400; + Sat, 07 Dec 2002 21:41:58 +0100 (MET) +Date: Sat, 07 Dec 2002 21:41:57 +0100 +From: Jochem van Dieten +Subject: Re: Query optimization +In-reply-to: <64850.168.103.211.137.1039227403.squirrel@mail.digicamp.com> +To: fred@digicamp.com +Cc: pgsql-performance@postgresql.org +Message-id: <3DF25D15.6060006@oli.tudelft.nl> +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 (Windows; U; WinNT4.0; en-US; rv:1.2) Gecko/20021126 +References: <64850.168.103.211.137.1039227403.squirrel@mail.digicamp.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/78 +X-Sequence-Number: 494 + +Fred Moyer wrote: +> +> I am trying to find a way to optimize this query and have hit a wall. The +> database size is 2.9 GB and contains 1 million records. + +> Postgresql.conf settings +> shared_buffers = 250000 + +This looks awfull high to me. 25000 might be better to give more room to +the OS disk-caching. Bit of a waste if PostgreSQL and the OS start +caching exactly the same blocks. +Trying is the only way to find a good setting. + + +> sort_mem = 1048576 # min 32 +> vacuum_mem = 128000 # min 1024 +> wal_files = 64 # range 0-64 +> enable_seqscan = false + +Why disable seqscan? For any query that is not particularly selective +this will mean a performance hit. + + +> enable_indexscan = true +> enable_tidscan = true +> enable_sort = true +> enable_nestloop = true +> enable_mergejoin = true +> enable_hashjoin = true + +> database=# explain analyze SELECT active,registrant,name FROM person WHERE +> object.active = 1 AND object.registrant = 't' ORDER BY UPPER(object.name) +> DESC LIMIT 10 OFFSET 0; +> NOTICE: QUERY PLAN: +> +> Limit (cost=nan..nan rows=10 width=2017) (actual +> time=204790.82..204790.84 rows=10 loops=1) +> -> Sort (cost=nan..nan rows=1032953 width=2017) (actual +> time=204790.81..204790.82 rows=11 loops=1) +> -> Index Scan using registrant__object__idx on object +> (cost=0.00..81733.63 rows=1032953 width=2017) (actual +> time=0.14..94509.14 rows=1032946 loops=1) +> Total runtime: 205125.75 msec + +I think this is an example of a not particularly selective query. If I +read it correctly, pretty much every row satisfies the predicates +object.active = 1 AND object.registrant = 't' (how much do not satisfy +these predicates?). + +Jochem + + +From pgsql-performance-owner@postgresql.org Sun Dec 8 08:49:30 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D06CB4760E5 + for ; + Sun, 8 Dec 2002 08:49:27 -0500 (EST) +Received: from anchor-post-30.mail.demon.net (anchor-post-30.mail.demon.net + [194.217.242.88]) + by postgresql.org (Postfix) with ESMTP id 12603474E61 + for ; + Sun, 8 Dec 2002 08:48:54 -0500 (EST) +Received: from mwynhau.demon.co.uk ([193.237.186.96] + helo=mainbox.archonet.com) + by anchor-post-30.mail.demon.net with esmtp (Exim 3.35 #1) + id 18L1ni-0001Xd-0U; Sun, 08 Dec 2002 13:48:57 +0000 +Received: from localhost (localhost.localdomain [127.0.0.1]) + by mainbox.archonet.com (Postfix) with ESMTP + id 3D71B16ADE; Sun, 8 Dec 2002 13:48:41 +0000 (GMT) +Received: from client.archonet.com (client.archonet.com [192.168.1.16]) + by mainbox.archonet.com (Postfix) with ESMTP + id 73C9115D69; Sun, 8 Dec 2002 13:48:40 +0000 (GMT) +Content-Type: text/plain; + charset="iso-8859-1" +From: Richard Huxton +Organization: Archonet Ltd +To: fred@digicamp.com +Subject: Re: Query optimization +Date: Sun, 8 Dec 2002 13:48:44 +0000 +User-Agent: KMail/1.4.3 +Cc: , +References: <64850.168.103.211.137.1039227403.squirrel@mail.digicamp.com> + <200212071713.09092.dev@archonet.com> + <55900.168.103.211.137.1039291841.squirrel@mail.digicamp.com> +In-Reply-To: <55900.168.103.211.137.1039291841.squirrel@mail.digicamp.com> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212081348.44370.dev@archonet.com> +X-Virus-Scanned: by AMaViS snapshot-20020531 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/79 +X-Sequence-Number: 495 + +On Saturday 07 Dec 2002 8:10 pm, Fred Moyer wrote: +> Ikes, they are the same, a cut and paste error. Sorry about that. No +> joins involved, one table with 1 million records, about 255 rows, only +> about 10% of the rows contain data in this particular instance. +> +> object is indexed on active, registrant, and name as well as UPPER(name). +> Postgres version is 7.2.3 + +I think Jochem's got it with "enable_seqscan" - you've disabled scans so th= +e=20 +planner is checking one million index entries - bad idea. Try Jochem's=20 +suggestion of re-enabling seqscan and see if that helps things along. + +> db=3D# select count(*) from count; +> count +> --------- +> 1032953 + +> >> time=3D204790.82..204790.84 rows=3D10 loops=3D1) +> >> -> Sort (cost=3Dnan..nan rows=3D1032953 width=3D2017) (actual +> >> time=3D204790.81..204790.82 rows=3D11 loops=3D1) +> >> -> Index Scan using registrant__object__idx on object +> >> (cost=3D0.00..81733.63 rows=3D1032953 width=3D2017) (actual +> >> time=3D0.14..94509.14 rows=3D1032946 loops=3D1) +> >> Total runtime: 205125.75 msec + +--=20 + Richard Huxton + +From pgsql-performance-owner@postgresql.org Sun Dec 8 14:33:38 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 37968475E75 + for ; + Sun, 8 Dec 2002 14:33:32 -0500 (EST) +Received: from joeconway.com (unknown [63.210.180.150]) + by postgresql.org (Postfix) with ESMTP id 6B0B9475E45 + for ; + Sun, 8 Dec 2002 14:33:31 -0500 (EST) +Received: from [192.168.5.3] (account jconway HELO joeconway.com) + by joeconway.com (CommuniGate Pro SMTP 3.5.9) + with ESMTP-TLS id 1473081; Sun, 08 Dec 2002 12:13:22 -0800 +Message-ID: <3DF39E2A.4010802@joeconway.com> +Date: Sun, 08 Dec 2002 11:31:54 -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: Tom Lane +Cc: Josh Berkus , pgsql-performance@postgresql.org +Subject: Re: Speeding up aggregates +References: + <12845.1039207565@sss.pgh.pa.us> +In-Reply-To: <12845.1039207565@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: 200212/80 +X-Sequence-Number: 496 + +Tom Lane wrote: +> FWIW, I've implemented hashed aggregation in CVS tip. I have not had +> the time to try to benchmark it, but I'd be interested if anyone can +> run some tests on 7.4devel. Eliminating the need for a SORT step +> should help aggregations over large datasets. +> +> Note that even though there's no SORT, the sort_mem setting is used +> to determine the allowable hashtable size, so a too-small sort_mem +> might discourage the planner from selecting hashed aggregation. +> Use EXPLAIN to see which query plan gets chosen. +> + +Here's some tests on a reasonable sized (and real life as opposed to +contrived) dataset: + +parts=# set enable_hashagg to off; +SET +parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +i, iwhs w where i.part_id = w.part_id group by i.part_id; + QUERY PLAN + +---------------------------------------------------------------------------------------------------------------------------------- + GroupAggregate (cost=11111.93..11744.90 rows=35528 width=36) (actual +time=2799.40..3140.17 rows=34575 loops=1) + -> Sort (cost=11111.93..11293.31 rows=72553 width=36) (actual +time=2799.35..2896.43 rows=72548 loops=1) + Sort Key: i.part_id + -> Hash Join (cost=1319.10..5254.45 rows=72553 width=36) (actual +time=157.72..1231.01 rows=72548 loops=1) + Hash Cond: ("outer".part_id = "inner".part_id) + -> Seq Scan on iwhs w (cost=0.00..2121.53 rows=72553 +width=22) (actual time=0.01..286.80 rows=72553 loops=1) + -> Hash (cost=1230.28..1230.28 rows=35528 width=14) (actual +time=157.50..157.50 rows=0 loops=1) + -> Seq Scan on inv i (cost=0.00..1230.28 rows=35528 +width=14) (actual time=0.02..88.00 rows=35528 loops=1) + Total runtime: 3168.73 msec +(9 rows) + +parts=# set enable_hashagg to on; +SET +parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +i, iwhs w where i.part_id = w.part_id group by i.part_id; + QUERY PLAN +---------------------------------------------------------------------------------------------------------------------------- + HashAggregate (cost=5617.22..5706.04 rows=35528 width=36) (actual +time=1507.89..1608.32 rows=34575 loops=1) + -> Hash Join (cost=1319.10..5254.45 rows=72553 width=36) (actual +time=153.46..1231.34 rows=72548 loops=1) + Hash Cond: ("outer".part_id = "inner".part_id) + -> Seq Scan on iwhs w (cost=0.00..2121.53 rows=72553 width=22) +(actual time=0.01..274.74 rows=72553 loops=1) + -> Hash (cost=1230.28..1230.28 rows=35528 width=14) (actual +time=153.21..153.21 rows=0 loops=1) + -> Seq Scan on inv i (cost=0.00..1230.28 rows=35528 +width=14) (actual time=0.03..84.67 rows=35528 loops=1) + Total runtime: 1661.53 msec +(7 rows) + +parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +i, iwhs w where i.part_id = w.part_id group by i.part_id having sum(w.qty_oh) > 0; + QUERY PLAN + +---------------------------------------------------------------------------------------------------------------------------------- + GroupAggregate (cost=11111.93..12015.10 rows=35528 width=36) (actual +time=2823.65..3263.16 rows=4189 loops=1) + Filter: (sum(qty_oh) > 0::double precision) + -> Sort (cost=11111.93..11293.31 rows=72553 width=36) (actual +time=2823.40..2926.07 rows=72548 loops=1) + Sort Key: i.part_id + -> Hash Join (cost=1319.10..5254.45 rows=72553 width=36) (actual +time=156.39..1240.61 rows=72548 loops=1) + Hash Cond: ("outer".part_id = "inner".part_id) + -> Seq Scan on iwhs w (cost=0.00..2121.53 rows=72553 +width=22) (actual time=0.01..290.47 rows=72553 loops=1) + -> Hash (cost=1230.28..1230.28 rows=35528 width=14) (actual +time=156.16..156.16 rows=0 loops=1) + -> Seq Scan on inv i (cost=0.00..1230.28 rows=35528 +width=14) (actual time=0.02..86.95 rows=35528 loops=1) + Total runtime: 3282.27 msec +(10 rows) + + +Note that similar to Josh, I saw a nice improvement when using the +HashAggregate on the simpler case, but as soon as I added a HAVING clause the +optimizer switched back to GroupAggregate. + +I'll try to play around with this a bit more later today. + +Joe + + +From pgsql-performance-owner@postgresql.org Sun Dec 8 14:39:26 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3DA90475B47 + for ; + Sun, 8 Dec 2002 14:39:25 -0500 (EST) +Received: from joeconway.com (unknown [63.210.180.150]) + by postgresql.org (Postfix) with ESMTP id 3008D47580B + for ; + Sun, 8 Dec 2002 14:39:24 -0500 (EST) +Received: from [192.168.5.3] (account jconway HELO joeconway.com) + by joeconway.com (CommuniGate Pro SMTP 3.5.9) + with ESMTP-TLS id 1473082; Sun, 08 Dec 2002 12:19:15 -0800 +Message-ID: <3DF39F8B.4050801@joeconway.com> +Date: Sun, 08 Dec 2002 11:37:47 -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: Tom Lane +Cc: Josh Berkus , pgsql-performance@postgresql.org +Subject: Re: Speeding up aggregates +References: + <12845.1039207565@sss.pgh.pa.us> +In-Reply-To: <12845.1039207565@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: 200212/81 +X-Sequence-Number: 497 + +Tom Lane wrote: +> Note that even though there's no SORT, the sort_mem setting is used +> to determine the allowable hashtable size, so a too-small sort_mem +> might discourage the planner from selecting hashed aggregation. +> Use EXPLAIN to see which query plan gets chosen. +> + +Just to follow up on my last post, I did indeed find that bumping up sort_mem +caused a switch back to HashAggregate, and a big improvement: + +parts=# show sort_mem ; + sort_mem +---------- + 8192 +(1 row) + +parts=# set sort_mem to 32000; +SET +parts=# show sort_mem ; + sort_mem +---------- + 32000 +(1 row) + +parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +i, iwhs w where i.part_id = w.part_id group by i.part_id having sum(w.qty_oh) > 0; + QUERY PLAN +---------------------------------------------------------------------------------------------------------------------------- + HashAggregate (cost=5254.46..5432.10 rows=35528 width=36) (actual +time=1286.89..1399.36 rows=4189 loops=1) + Filter: (sum(qty_oh) > 0::double precision) + -> Hash Join (cost=1319.10..4710.31 rows=72553 width=36) (actual +time=163.36..947.54 rows=72548 loops=1) + Hash Cond: ("outer".part_id = "inner".part_id) + -> Seq Scan on iwhs w (cost=0.00..2121.53 rows=72553 width=22) +(actual time=0.01..266.20 rows=72553 loops=1) + -> Hash (cost=1230.28..1230.28 rows=35528 width=14) (actual +time=162.70..162.70 rows=0 loops=1) + -> Seq Scan on inv i (cost=0.00..1230.28 rows=35528 +width=14) (actual time=0.04..88.98 rows=35528 loops=1) + Total runtime: 1443.93 msec +(8 rows) + +parts=# set sort_mem to 8192; +SET +parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +i, iwhs w where i.part_id = w.part_id group by i.part_id having sum(w.qty_oh) > 0; + QUERY PLAN + +---------------------------------------------------------------------------------------------------------------------------------- + GroupAggregate (cost=11111.93..12015.10 rows=35528 width=36) (actual +time=2836.98..3261.66 rows=4189 loops=1) + Filter: (sum(qty_oh) > 0::double precision) + -> Sort (cost=11111.93..11293.31 rows=72553 width=36) (actual +time=2836.73..2937.78 rows=72548 loops=1) + Sort Key: i.part_id + -> Hash Join (cost=1319.10..5254.45 rows=72553 width=36) (actual +time=155.42..1258.40 rows=72548 loops=1) + Hash Cond: ("outer".part_id = "inner".part_id) + -> Seq Scan on iwhs w (cost=0.00..2121.53 rows=72553 +width=22) (actual time=0.01..308.57 rows=72553 loops=1) + -> Hash (cost=1230.28..1230.28 rows=35528 width=14) (actual +time=155.19..155.19 rows=0 loops=1) + -> Seq Scan on inv i (cost=0.00..1230.28 rows=35528 +width=14) (actual time=0.02..86.82 rows=35528 loops=1) + Total runtime: 3281.75 msec +(10 rows) + + +So when it gets used, HashAggregate has provided a factor of two improvement +on this test case at least. Nice work, Tom! + +Joe + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 01:39:06 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EA375476422 + for ; + Mon, 9 Dec 2002 01:39:05 -0500 (EST) +Received: from geulph.frogspace.net (geulph.frogspace.net [64.6.226.2]) + by postgresql.org (Postfix) with ESMTP id 6498A4763B7 + for ; + Mon, 9 Dec 2002 01:38:22 -0500 (EST) +Received: from [150.203.127.65] (helo=leda) + by geulph.frogspace.net with smtp (Exim 3.36 #5) id 18LHYG-0003uN-00 + for pgsql-performance@postgresql.org; Sun, 08 Dec 2002 22:38:00 -0800 +Message-ID: <007501c29f4c$8e30f820$417fcb96@anu.edu.au> +From: "Kalle Barck-Holst" +To: +Subject: is insertion and movement times are correlated to the size of the + database? +Date: Mon, 9 Dec 2002 07:30:48 +0100 +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-1" +Content-Transfer-Encoding: quoted-printable +X-Priority: 3 +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook Express 5.50.4522.1200 +X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/82 +X-Sequence-Number: 498 + +Hi + +I am doing a research project on real time robotics and wanted to have the = +postgres as a database to save measurements we aggregate when running our r= +obots. + +A common operation we do is insertion and movements of measurements within = +tables. But it seams as if insertion and movement times are correlated to t= +he size of the database. Can this be possible? IE inserting into a large da= +tabase takes longer time than into a small database. + +I'd be grateful for comments on the reason for this. + +Carl Barck-Holst + + +Carl och Josefine Barck-Holst +=D6stermalms g 84 +11450 Stockholm +08 6679904 +Carl 070-2642506 +Josefine 073-9648103 + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 03:22:25 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 822D84758DC + for ; + Mon, 9 Dec 2002 03:22:23 -0500 (EST) +Received: from localhost.localdomain (sein.itera.ee [194.126.109.126]) + by postgresql.org (Postfix) with ESMTP id 4D8B547580B + for ; + Mon, 9 Dec 2002 03:22:22 -0500 (EST) +Received: (from hannu@localhost) + by localhost.localdomain (8.11.6/8.11.6) id gB9AG2407554; + Mon, 9 Dec 2002 10:16:02 GMT +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: Speeding up aggregates +From: Hannu Krosing +To: Joe Conway +Cc: Tom Lane , Josh Berkus , + pgsql-performance@postgresql.org +In-Reply-To: <3DF39E2A.4010802@joeconway.com> +References: + <12845.1039207565@sss.pgh.pa.us> <3DF39E2A.4010802@joeconway.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039428960.7415.3.camel@huli> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 09 Dec 2002 10:16:01 +0000 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/83 +X-Sequence-Number: 499 + +On Sun, 2002-12-08 at 19:31, Joe Conway wrote: + +> parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +> i, iwhs w where i.part_id = w.part_id group by i.part_id having sum(w.qty_oh) > 0; +> QUERY PLAN +... +> Total runtime: 3282.27 msec +> (10 rows) +> +> +> Note that similar to Josh, I saw a nice improvement when using the +> HashAggregate on the simpler case, but as soon as I added a HAVING clause the +> optimizer switched back to GroupAggregate. +> +> I'll try to play around with this a bit more later today. + +Try turning the having into subquery + where: + +explain analyze +select * from ( + select i.part_id, sum(w.qty_oh) as total_oh + from inv i, iwhs w + where i.part_id = w.part_id + group by i.part_id) sub +where total_oh > 0; + +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Mon Dec 9 06:36:10 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6DF794758DC + for ; + Mon, 9 Dec 2002 06:36:06 -0500 (EST) +Received: from spike.esolution.pl (spike.esolution.pl [217.11.134.154]) + by postgresql.org (Postfix) with ESMTP id 0393D47580B + for ; + Mon, 9 Dec 2002 06:35:53 -0500 (EST) +Received: from pd171.warszawa.cvx.ppp.tpnet.pl ([213.76.99.171] + helo=depesz.pl) + by spike.esolution.pl with esmtp (Exim 4.10) id 18LMBj-0001rK-00 + for pgsql-performance@postgresql.org; Mon, 09 Dec 2002 12:35:07 +0100 +Received: from depesz by depesz.pl with local (Exim 3.36 #1) + id 18LM9H-0000IT-00 + for pgsql-performance@postgresql.org; Mon, 09 Dec 2002 12:32:31 +0100 +Date: Mon, 9 Dec 2002 12:32:31 +0100 +From: Hubert depesz Lubaczewski +To: pgsql-performance@postgresql.org +Subject: questions about disk configurations +Message-ID: <20021209113231.GA1113@depesz.pl> +Reply-To: depesz@depesz.pl +Mime-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-2 +Content-Disposition: inline +Content-Transfer-Encoding: 8bit +User-Agent: Mutt/1.4i +X-info-en-1: this message *may* reflect my personal opinion. it is *not* +X-info-en-2: intended to reflect those of my employer, or anyone else. +X-info-pl-1: wszelkie opinie =?iso-8859-2?Q?wyra=BFone_?= + =?iso-8859-2?Q?w_tym_li=B6cie_prezentuj=B1_wy=B3=B1cznie_pogl=B1dy?= +X-info-pl-2: autora listu. opinie =?iso-8859-2?Q?te_?= + =?iso-8859-2?Q?w_=BFadnym__razie_nie__wyra=BFaj=B1__pogl=B1d=F3w?= +X-info-pl-3: pracodawcy autora =?iso-8859-2?Q?listu_?= + =?iso-8859-2?Q?_ani__innych__zwi=B1zanych__z__nim__os=F3b=2E?= +X-Operating-System: Linux 2.4.18 i686 Pentium_III_(Coppermine) +X-Spam-Score: 0.8 (/) +X-Scanner: exiscan for exim4 (http://duncanthrax.net/exiscan/) + *18LMBj-0001rK-00*3Okpi7YYmwI* +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/84 +X-Sequence-Number: 500 + +hi +i have a question about best harddisk configuration for postgresql +performance. +of course i know that: +- scsi is better than ide +- 2 disks are better than 1 +- 3 disks are better than 2 + +i know that with 3 disks one should move xlog to one drive, index files +to second and tables to third. +that's clear. + +but: +will making software raid on this discs provide performance increase or +decrease? +which raid (0,1,5,10?) is best for postgresql? maybe it differs when it +comes to different datatypes (i.e. raid "X" is best for indices, but "Y" +best for tables). + +i'd like to know what are the options to store all this information +(xlog, indices and tables). what configurations are best, what medium +and what should be avoided at all cost. + +hope you can help me, and sorry for my english. + +depesz + +-- +hubert depesz lubaczewski http://www.depesz.pl/ +------------------------------------------------------------------------ +M�j Bo�e, spraw abym milcza�, dop�ki si� nie upewni�, �e naprawd� mam +co� do powiedzenia. (c) 1998 depesz + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 07:02:15 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EE2964758DC + for ; + Mon, 9 Dec 2002 07:02:13 -0500 (EST) +Received: from gluggsi.fortytwo.ch (zux006-044-193.adsl.green.ch + [81.6.44.193]) + by postgresql.org (Postfix) with ESMTP id A8AF647580B + for ; + Mon, 9 Dec 2002 07:02:12 -0500 (EST) +Received: from altfrangg.fortytwo.ch (altfrangg.fortytwo.ch [192.168.1.17]) + by gluggsi.fortytwo.ch (Postfix) with ESMTP id C4FDC1808 + for ; + Mon, 9 Dec 2002 13:01:58 +0100 (CET) +Received: by altfrangg.fortytwo.ch (Postfix, from userid 1000) + id 27EE814350; Mon, 9 Dec 2002 13:01:58 +0100 (CET) +Subject: Re: questions about disk configurations +From: Adrian 'Dagurashibanipal' von Bidder +To: pgsql-performance@postgresql.org +In-Reply-To: <20021209113231.GA1113@depesz.pl> +References: <20021209113231.GA1113@depesz.pl> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-s1FNMu7G/AyOtw8D/8u6" +Organization: +Message-Id: <1039435317.819.36.camel@altfrangg.fortytwo.ch> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 09 Dec 2002 13:01:58 +0100 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/85 +X-Sequence-Number: 501 + +--=-s1FNMu7G/AyOtw8D/8u6 +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +On Mon, 2002-12-09 at 12:32, Hubert depesz Lubaczewski wrote: +> hi +> i have a question about best harddisk configuration for postgresql +> performance. +[...] + +Yo! + +A bit more data is needed before anybody can give you more help: + - what is your budget? + - how big will your databases be? + - what's the read/write ratio? + +Even then you'll not get any good recipes, because there aren't any. +You'll have to do benchmarks yourself. A few fundamental things that are +probably true for most: + + - more RAM is always good. Independent from the disc architecture - if +an access isn't going to the disc at all, it's always good. (if you're +mostly writing this may be lessened). + - always carefully tune the postgres installation (random page cost, +sort mem, shared buffers, ... - all depend on your system and you +application) + - as you correctly said: distribute the load on many spindles. On a +busy database, 4*20G is probably faster than 1*80G + +beyound this, experiences vary. RAID1 and RAID5 are rated differently by +different people - and especially with RAID5 there are (I think) really +performance differencies between the various products. RAID0 is fastest, +of course, but you probably care for your data. + +For equally good implementations, RAID1 and RAID5 may have similar +speed, especially if the RAID controller for RAID5 has enough RAM. If +the active dataset on a RAID5 is bigger than the available caching RAM, +write performance sucks as a single block write requires 2 reads and 2 +writes. If the RAID5 controller has enough RAM (and a decent +implementation), write performance can be almost equal to RAID1 (2 +writes for a single block write). + +So far +-- vbi + + +--=20 +this email is protected by a digital signature: http://fortytwo.ch/gpg + +NOTE: keyserver bugs! get my key here: https://fortytwo.ch/gpg/92082481 + +--=-s1FNMu7G/AyOtw8D/8u6 +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 (GNU/Linux) + +iHMEABECADMFAj30hjUsGmh0dHA6Ly9mb3J0eXR3by5jaC9sZWdhbC9ncGcvZW1h +aWwuMjAwMjA4MjIACgkQi6Qxi+Wn99bIxwCgvZA99TfBmTA/b0urlakcM3ZUuiwA +njrqjNNJuChuqyF8dv/C7J1eytgt +=OL0k +-----END PGP SIGNATURE----- +Signature policy: http://fortytwo.ch/legal/gpg/email.20020822 + +--=-s1FNMu7G/AyOtw8D/8u6-- + +From pgsql-performance-owner@postgresql.org Mon Dec 9 08:05:01 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7C59047580B + for ; + Mon, 9 Dec 2002 08:04:59 -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 0508E474E5C + for ; + Mon, 9 Dec 2002 08:04:58 -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 gB9D4wTZ078244; + Mon, 9 Dec 2002 08:04:58 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: is insertion and movement times are correlated to +From: Rod Taylor +To: Kalle Barck-Holst +Cc: Pgsql Performance +In-Reply-To: <007501c29f4c$8e30f820$417fcb96@anu.edu.au> +References: <007501c29f4c$8e30f820$417fcb96@anu.edu.au> +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-D/VAFAfQxXqwzZXhofAj" +Organization: +Message-Id: <1039439098.79804.219.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 09 Dec 2002 08:04:58 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/86 +X-Sequence-Number: 502 + +--=-D/VAFAfQxXqwzZXhofAj +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +On Mon, 2002-12-09 at 01:30, Kalle Barck-Holst wrote: +> Hi +>=20 +> I am doing a research project on real time robotics and wanted to have th= +e postgres as a database to save measurements we aggregate when running our= + robots. +>=20 +> A common operation we do is insertion and movements of measurements withi= +n tables. But it seams as if insertion and movement times are correlated to= + the size of the database. Can this be possible? IE inserting into a large = +database takes longer time than into a small database. + +If there are any indexes or constraints, then definitely. The insert +really doesn't have additional overhead for the size of the DB, but the +work involved for most constraints and indexes do. + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-D/VAFAfQxXqwzZXhofAj +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) + +iD8DBQA99JT56DETLow6vwwRAsjFAJ9Cod1dGZsw5TIDzidGl0lBHkCT6QCfdN3q +EEnoBvd8CNP/uvaxqMTTHSM= +=iLez +-----END PGP SIGNATURE----- + +--=-D/VAFAfQxXqwzZXhofAj-- + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 14:49:32 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 9F29F47636B + for ; + Mon, 9 Dec 2002 14:49:30 -0500 (EST) +Received: from spike.esolution.pl (spike.esolution.pl [217.11.134.154]) + by postgresql.org (Postfix) with ESMTP id 705764762FD + for ; + Mon, 9 Dec 2002 14:45:44 -0500 (EST) +Received: from ql77.neoplus.adsl.tpnet.pl ([80.50.72.77] helo=depesz.pl) + by spike.esolution.pl with esmtp (Exim 4.10) + id 18LTqJ-0004LE-00; Mon, 09 Dec 2002 20:45:27 +0100 +Received: from depesz by depesz.pl with local (Exim 3.36 #1) + id 18LNb7-000195-00; Mon, 09 Dec 2002 14:05:21 +0100 +Date: Mon, 9 Dec 2002 14:05:21 +0100 +From: Hubert depesz Lubaczewski +To: Adrian 'Dagurashibanipal' von Bidder , + pgsql-performance@postgresql.org +Subject: Re: questions about disk configurations +Message-ID: <20021209130521.GA4372@depesz.pl> +Reply-To: depesz@depesz.pl +References: <20021209113231.GA1113@depesz.pl> + <1039435317.819.36.camel@altfrangg.fortytwo.ch> +Mime-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-2 +Content-Disposition: inline +Content-Transfer-Encoding: 8bit +In-Reply-To: <1039435317.819.36.camel@altfrangg.fortytwo.ch> +User-Agent: Mutt/1.4i +X-info-en-1: this message *may* reflect my personal opinion. it is *not* +X-info-en-2: intended to reflect those of my employer, or anyone else. +X-info-pl-1: wszelkie opinie =?iso-8859-2?Q?wyra=BFone_?= + =?iso-8859-2?Q?w_tym_li=B6cie_prezentuj=B1_wy=B3=B1cznie_pogl=B1dy?= +X-info-pl-2: autora listu. opinie =?iso-8859-2?Q?te_?= + =?iso-8859-2?Q?w_=BFadnym__razie_nie__wyra=BFaj=B1__pogl=B1d=F3w?= +X-info-pl-3: pracodawcy autora =?iso-8859-2?Q?listu_?= + =?iso-8859-2?Q?_ani__innych__zwi=B1zanych__z__nim__os=F3b=2E?= +X-Operating-System: Linux 2.4.18 i686 Pentium_III_(Coppermine) +X-Spam-Score: -2.6 (--) +X-Scanner: exiscan for exim4 (http://duncanthrax.net/exiscan/) + *18LTqJ-0004LE-00*dKbfjFIReaA* +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/88 +X-Sequence-Number: 504 + +On Mon, Dec 09, 2002 at 01:01:58PM +0100, Adrian 'Dagurashibanipal' von Bidder wrote: +> A bit more data is needed before anybody can give you more help: +> - what is your budget? +> - how big will your databases be? +> - what's the read/write ratio? + +my question as for now is purely theoretical. i'm not asking about any +specific situation, but me may talk about medium sized web size. budget +is irrelevant (i'd like to talk *only* about harddrives, not memory, +architescure and so on). + +> - as you correctly said: distribute the load on many spindles. On a +> busy database, 4*20G is probably faster than 1*80G + +as i said: i know that 3 disks are bettar than 1 (as for postgres +installation, because system data and swap should be on 4th disc - but +this is obvious). + +> beyound this, experiences vary. RAID1 and RAID5 are rated differently by +> different people - and especially with RAID5 there are (I think) really +> performance differencies between the various products. RAID0 is fastest, +> of course, but you probably care for your data. + +that's exactly what i'm asking about: which raid is best suited for +which data amongst out 3 sets (xlog, tables, indices). or maybe for some +types of data single disc is better than raid for some strange reason? +is it better to (when having 2 discs) setup raid 0/1 or to use tham +separatelly as xlog/tables? + +depesz + +-- +hubert depesz lubaczewski http://www.depesz.pl/ +------------------------------------------------------------------------ +M�j Bo�e, spraw abym milcza�, dop�ki si� nie upewni�, �e naprawd� mam +co� do powiedzenia. (c) 1998 depesz + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 13:14:03 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CD49A4763ED + for ; + Mon, 9 Dec 2002 13:13:59 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP id 19EEC4761C4 + for ; + Mon, 9 Dec 2002 13:10:04 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id gB9I9VK05778; + Mon, 9 Dec 2002 13:09:31 -0500 (EST) +From: Bruce Momjian +Message-Id: <200212091809.gB9I9VK05778@candle.pha.pa.us> +Subject: Re: Speeding up aggregates +In-Reply-To: <1039211397.2067.18.camel@rh72.home.ee> +To: Hannu Krosing +Date: Mon, 9 Dec 2002 13:09:31 -0500 (EST) +Cc: Tom Lane , Josh Berkus , + 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: 200212/87 +X-Sequence-Number: 503 + + +Added. + +--------------------------------------------------------------------------- + +Hannu Krosing wrote: +> Hannu Krosing kirjutas L, 07.12.2002 kell 02:32: +> > Tom Lane kirjutas L, 07.12.2002 kell 01:46: +> > > "Josh Berkus" writes: +> > > > What have other Postgres users done to speed up aggregates on large +> > > > tables? +> > > +> > > FWIW, I've implemented hashed aggregation in CVS tip. +> > +> > Great! +> > +> > This should also make it easier to implement all kinds of GROUP BY +> > ROLLUP|CUBE|GROUPING SETS|() queries. +> +> Of these only ROLLUP can be done in one scan after sort, all others +> would generally require several scans without hashing. +> +> +> I just noticed that we don't even have a TODO for this. I think this +> would be a good TODO item. +> +> Bruce, could you add: +> +> * Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY +> +> +> They are all defined in SQL99 p.79 +> +> +> Some more background info (from a quick Google search) +> +> a very short overview: +> http://www.neddo.com/dm3e/sql3&olap.html +> +> +> more thorough guide for DB2: +> http://www.student.math.uwaterloo.ca/~cs448/db2_doc/html/db2s0/frame3.htm#db2s0279 +> +> +> ----------------- +> Hannu +> +> +> ---------------------------(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 Mon Dec 9 14:51:23 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8E0A347603A + for ; + Mon, 9 Dec 2002 14:51:22 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 31D904763B7 + for ; + Mon, 9 Dec 2002 14:49:35 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2273504; Mon, 09 Dec 2002 11:49:37 -0800 +Content-Type: text/plain; + charset="iso-8859-2" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: depesz@depesz.pl, pgsql-performance@postgresql.org +Subject: Re: questions about disk configurations +Date: Mon, 9 Dec 2002 11:53:03 -0800 +X-Mailer: KMail [version 1.4] +References: <20021209113231.GA1113@depesz.pl> +In-Reply-To: <20021209113231.GA1113@depesz.pl> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212091153.03762.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/89 +X-Sequence-Number: 505 + + +Depesz, + +> i have a question about best harddisk configuration for postgresql +> performance. +> of course i know that: +> - scsi is better than ide +> - 2 disks are better than 1 +> - 3 disks are better than 2 +>=20 +> i know that with 3 disks one should move xlog to one drive, index files +> to second and tables to third. +> that's clear. + +Er, no, it's not. In fact, for a 3-disk config, I reccommend: + +Disk 1: OS, swap, system logs +Disk 2: Data + Indexes +Disk 3: Transaction Log + +> but: +> will making software raid on this discs provide performance increase or +> decrease? + +Hardware RAID can improve *read* performance, particilarly RAIDs 1, 01, and= +=20 +10. For writing, the best you can do is having it not inhibit performance.= +=20=20=20 +The general testament is that *software* RAID does not improve things at al= +l;=20 +actually, the best that can be said for Linux Software RAID 1 is that it do= +es=20 +not harm performance much. + +> i'd like to know what are the options to store all this information +> (xlog, indices and tables). what configurations are best, what medium +> and what should be avoided at all cost. + +Ask specific questions. If you want the full performance tutorial, you'd h= +ave=20 +to pay a steep fee for 1-3 days of training. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 15:00:34 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A9063475E13 + for ; + Mon, 9 Dec 2002 15:00:32 -0500 (EST) +Received: from hal.istation.com (unknown [65.120.151.132]) + by postgresql.org (Postfix) with ESMTP id F1147475C22 + for ; + Mon, 9 Dec 2002 15:00:31 -0500 (EST) +Received: from sauron (sauron.istation.com [65.120.151.174]) (authenticated) + by hal.istation.com (8.11.6/8.11.6) with ESMTP id gB9K0Uv13447 + for ; Mon, 9 Dec 2002 14:00:30 -0600 +Reply-To: +From: "Keith Bottner" +To: +Subject: Re: questions about disk configurations +Date: Mon, 9 Dec 2002 14:00:32 -0600 +Organization: istation.com +Message-ID: <001c01c29fbd$a14e6520$ae977841@istation.com> +MIME-Version: 1.0 +Content-Type: text/plain; + charset="iso-8859-2" +Content-Transfer-Encoding: quoted-printable +X-Priority: 3 (Normal) +X-MSMail-Priority: Normal +X-Mailer: Microsoft Outlook, Build 10.0.3416 +X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 +In-Reply-To: <20021209130521.GA4372@depesz.pl> +Importance: Normal +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/90 +X-Sequence-Number: 506 + +I don't know whether you have read this link but it was helpful to me. + +http://www.ca.postgresql.org/docs/momjian/hw_performance/0.html + +It discusses PostgreSQL Hardware Performance Tuning. + +Hope it helps! + +Keith Bottner + +-----Original Message----- +From: pgsql-performance-owner@postgresql.org +[mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Hubert +depesz Lubaczewski +Sent: Monday, December 09, 2002 7:05 AM +To: Adrian 'Dagurashibanipal' von Bidder; +pgsql-performance@postgresql.org +Subject: Re: [PERFORM] questions about disk configurations + + +On Mon, Dec 09, 2002 at 01:01:58PM +0100, Adrian 'Dagurashibanipal' von +Bidder wrote: +> A bit more data is needed before anybody can give you more help: +> - what is your budget? +> - how big will your databases be? +> - what's the read/write ratio? + +my question as for now is purely theoretical. i'm not asking about any +specific situation, but me may talk about medium sized web size. budget +is irrelevant (i'd like to talk *only* about harddrives, not memory, +architescure and so on). + +> - as you correctly said: distribute the load on many spindles. On a=20 +> busy database, 4*20G is probably faster than 1*80G + +as i said: i know that 3 disks are bettar than 1 (as for postgres +installation, because system data and swap should be on 4th disc - but +this is obvious). + +> beyound this, experiences vary. RAID1 and RAID5 are rated differently=20 +> by different people - and especially with RAID5 there are (I think)=20 +> really performance differencies between the various products. RAID0 is + +> fastest, of course, but you probably care for your data. + +that's exactly what i'm asking about: which raid is best suited for +which data amongst out 3 sets (xlog, tables, indices). or maybe for some +types of data single disc is better than raid for some strange reason? +is it better to (when having 2 discs) setup raid 0/1 or to use tham +separatelly as xlog/tables? + +depesz + +--=20 +hubert depesz lubaczewski http://www.depesz.pl/ +------------------------------------------------------------------------ +M=F3j Bo=BFe, spraw abym milcza=B3, dop=F3ki si=EA nie upewni=EA, =BFe na= +prawd=EA mam +co=B6 do powiedzenia. (c) 1998 depesz + + +---------------------------(end of broadcast)--------------------------- +TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 15:47:30 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D82E3476414 + for ; + Mon, 9 Dec 2002 15:47:28 -0500 (EST) +Received: from lakemtao02.cox.net (lakemtao02.cox.net [68.1.17.243]) + by postgresql.org (Postfix) with ESMTP id 89AB747640E + for ; + Mon, 9 Dec 2002 15:46:41 -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 <20021209204640.UQAY2203.lakemtao02.cox.net@[192.168.1.1]> + for ; + Mon, 9 Dec 2002 15:46:40 -0500 +Subject: Re: questions about disk configurations +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <20021209130521.GA4372@depesz.pl> +References: <20021209113231.GA1113@depesz.pl> + <1039435317.819.36.camel@altfrangg.fortytwo.ch> + <20021209130521.GA4372@depesz.pl> +Content-Type: text/plain +Organization: +Message-Id: <1039466800.27242.51.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 09 Dec 2002 14:46:40 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/91 +X-Sequence-Number: 507 + +On Mon, 2002-12-09 at 07:05, Hubert depesz Lubaczewski wrote: +> On Mon, Dec 09, 2002 at 01:01:58PM +0100, Adrian 'Dagurashibanipal' von Bidder wrote: +> > A bit more data is needed before anybody can give you more help: +> > - what is your budget? +> > - how big will your databases be? +> > - what's the read/write ratio? +> +> my question as for now is purely theoretical. i'm not asking about any +> specific situation, but me may talk about medium sized web size. budget +> is irrelevant (i'd like to talk *only* about harddrives, not memory, +> architescure and so on). + +What is "medium sized web"? The *system* *is* important!! Stuffing +your box with RAM may, in fact, override your disks, if the RAM caches +enough. + +> > - as you correctly said: distribute the load on many spindles. On a +> > busy database, 4*20G is probably faster than 1*80G +> +> as i said: i know that 3 disks are bettar than 1 (as for postgres +> installation, because system data and swap should be on 4th disc - but +> this is obvious). +> +> > beyound this, experiences vary. RAID1 and RAID5 are rated differently by +> > different people - and especially with RAID5 there are (I think) really +> > performance differencies between the various products. RAID0 is fastest, +> > of course, but you probably care for your data. +> +> that's exactly what i'm asking about: which raid is best suited for +> which data amongst out 3 sets (xlog, tables, indices). or maybe for some +> types of data single disc is better than raid for some strange reason? +> is it better to (when having 2 discs) setup raid 0/1 or to use tham +> separatelly as xlog/tables? + +These are *GENERALITIES*!!!! _All_ is dependent on which SCSI +controller you choose, and how much cache it has!!!!!!!! + +- RAID0 does *great* at both reading and writing, but everyone knows +that it is insecure. +- RAID1 does better than JBOD at reading and writing, but not as +good as RAID0. +- RAID01 and RAID10 do just about as good as RAID0. +- RAID5 does great with reads, but bad with writes, *unless* the +controller has *lots* of cache. Then, write speeds are great. + +Slightly off topic: if I have Important Data, then I would not trust +a caching controlller unless it has a battery backup. Unfortunately, +the only "caching controlllers with battery backup" that I've seen +are pretty expensive... + +-- ++------------------------------------------------------------+ +| Ron Johnson, Jr. mailto:ron.l.johnson@cox.net | +| Jefferson, LA USA http://members.cox.net/ron.l.johnson | +| | +| "they love our milk and honey, but preach about another | +| way of living" | +| Merle Haggard, "The Fighting Side Of Me" | ++------------------------------------------------------------+ + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 16:12:40 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 31E9347650E + for ; + Mon, 9 Dec 2002 16:12:36 -0500 (EST) +Received: from joeconway.com (unknown [63.210.180.150]) + by postgresql.org (Postfix) with ESMTP id 5B9104764CA + for ; + Mon, 9 Dec 2002 16:05:54 -0500 (EST) +Received: from [206.19.64.3] (account jconway HELO joeconway.com) + by joeconway.com (CommuniGate Pro SMTP 3.5.9) + with ESMTP-TLS id 1474243; Mon, 09 Dec 2002 13:45:03 -0800 +Message-ID: <3DF50552.8030603@joeconway.com> +Date: Mon, 09 Dec 2002 13:04:18 -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: Hannu Krosing +Cc: Tom Lane , Josh Berkus , + pgsql-performance@postgresql.org +Subject: Re: Speeding up aggregates +References: + <12845.1039207565@sss.pgh.pa.us> + <3DF39E2A.4010802@joeconway.com> <1039428960.7415.3.camel@huli> +In-Reply-To: <1039428960.7415.3.camel@huli> +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/92 +X-Sequence-Number: 508 + +Hannu Krosing wrote: +> On Sun, 2002-12-08 at 19:31, Joe Conway wrote: +> +> +>>parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +>>i, iwhs w where i.part_id = w.part_id group by i.part_id having sum(w.qty_oh) > 0; +>> QUERY PLAN +> +> ... +> +>> Total runtime: 3282.27 msec +>>(10 rows) +>> +>> +>>Note that similar to Josh, I saw a nice improvement when using the +>>HashAggregate on the simpler case, but as soon as I added a HAVING clause the +>>optimizer switched back to GroupAggregate. +>> +>>I'll try to play around with this a bit more later today. +> +> +> Try turning the having into subquery + where: +> +> explain analyze +> select * from ( +> select i.part_id, sum(w.qty_oh) as total_oh +> from inv i, iwhs w +> where i.part_id = w.part_id +> group by i.part_id) sub +> where total_oh > 0; +> + +Pretty much the same result. See below. + +Joe + +====================================== +parts=# set sort_mem to 8000; +SET +parts=# explain analyze select * from (select i.part_id, sum(w.qty_oh) as +total_oh from inv i, iwhs w where i.part_id = w.part_id group by i.part_id) +sub where total_oh > 0; + QUERY PLAN + +---------------------------------------------------------------------------------------------------------------------------------------- + Subquery Scan sub (cost=11111.93..12015.10 rows=35528 width=36) (actual +time=2779.16..3212.46 rows=4189 loops=1) + -> GroupAggregate (cost=11111.93..12015.10 rows=35528 width=36) (actual +time=2779.15..3202.97 rows=4189 loops=1) + Filter: (sum(qty_oh) > 0::double precision) + -> Sort (cost=11111.93..11293.31 rows=72553 width=36) (actual +time=2778.90..2878.33 rows=72548 loops=1) + Sort Key: i.part_id + -> Hash Join (cost=1319.10..5254.45 rows=72553 width=36) +(actual time=155.80..1235.32 rows=72548 loops=1) + Hash Cond: ("outer".part_id = "inner".part_id) + -> Seq Scan on iwhs w (cost=0.00..2121.53 rows=72553 +width=22) (actual time=0.01..282.38 rows=72553 loops=1) + -> Hash (cost=1230.28..1230.28 rows=35528 width=14) +(actual time=155.56..155.56 rows=0 loops=1) + -> Seq Scan on inv i (cost=0.00..1230.28 +rows=35528 width=14) (actual time=0.02..86.69 rows=35528 loops=1) + Total runtime: 3232.84 msec +(11 rows) + +parts=# set sort_mem to 12000; +SET +parts=# explain analyze select * from (select i.part_id, sum(w.qty_oh) as +total_oh from inv i, iwhs w where i.part_id = w.part_id group by i.part_id) +sub where total_oh > 0; + QUERY PLAN + +---------------------------------------------------------------------------------------------------------------------------------- + Subquery Scan sub (cost=5617.22..5794.86 rows=35528 width=36) (actual +time=1439.24..1565.47 rows=4189 loops=1) + -> HashAggregate (cost=5617.22..5794.86 rows=35528 width=36) (actual +time=1439.23..1555.65 rows=4189 loops=1) + Filter: (sum(qty_oh) > 0::double precision) + -> Hash Join (cost=1319.10..5073.07 rows=72553 width=36) (actual +time=159.39..1098.30 rows=72548 loops=1) + Hash Cond: ("outer".part_id = "inner".part_id) + -> Seq Scan on iwhs w (cost=0.00..2121.53 rows=72553 +width=22) (actual time=0.01..259.48 rows=72553 loops=1) + -> Hash (cost=1230.28..1230.28 rows=35528 width=14) (actual +time=159.11..159.11 rows=0 loops=1) + -> Seq Scan on inv i (cost=0.00..1230.28 rows=35528 +width=14) (actual time=0.03..87.74 rows=35528 loops=1) + Total runtime: 1609.91 msec +(9 rows) + + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 16:31:10 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 588A24765EE + for ; + Mon, 9 Dec 2002 16:31:06 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 19CE7476409 + for ; + Mon, 9 Dec 2002 16:26:34 -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 gB9LQWpd019750; + Mon, 9 Dec 2002 16:26:33 -0500 (EST) +To: Joe Conway +Cc: Josh Berkus , pgsql-performance@postgresql.org +Subject: Re: Speeding up aggregates +In-reply-to: <3DF39F8B.4050801@joeconway.com> +References: + <12845.1039207565@sss.pgh.pa.us> <3DF39F8B.4050801@joeconway.com> +Comments: In-reply-to Joe Conway + message dated "Sun, 08 Dec 2002 11:37:47 -0800" +Date: Mon, 09 Dec 2002 16:26:32 -0500 +Message-ID: <19749.1039469192@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/93 +X-Sequence-Number: 509 + +Joe Conway writes: +> Just to follow up on my last post, I did indeed find that bumping up sort_mem +> caused a switch back to HashAggregate, and a big improvement: + +> parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +> i, iwhs w where i.part_id = w.part_id group by i.part_id having sum(w.qty_oh) > 0; +> QUERY PLAN +> ---------------------------------------------------------------------------------------------------------------------------- +> HashAggregate (cost=5254.46..5432.10 rows=35528 width=36) (actual +> time=1286.89..1399.36 rows=4189 loops=1) +> Filter: (sum(qty_oh) > 0::double precision) +> -> Hash Join (cost=1319.10..4710.31 rows=72553 width=36) (actual +> time=163.36..947.54 rows=72548 loops=1) + +How many rows out if you drop the HAVING clause? + +The planner's choice of which to use is dependent on its estimate of the +required hashtable size, which is proportional to its guess about how +many distinct groups there will be. The above output doesn't tell us +that however, only how many groups passed the HAVING clause. I'm +curious about the quality of this estimate, since the code to try to +generate not-completely-bogus group count estimates is all new ... + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Mon Dec 9 16:51:54 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1B8E04763B7 + for ; + Mon, 9 Dec 2002 16:51:52 -0500 (EST) +Received: from l2.socialecology.com (unknown [4.42.179.131]) + by postgresql.org (Postfix) with ESMTP id 3E3AD476058 + for ; + Mon, 9 Dec 2002 16:42:13 -0500 (EST) +Received: from 4.42.179.151 (broccoli.socialecology.com [4.42.179.151]) + by l2.socialecology.com (Postfix) with SMTP id 264C028E944 + for ; + Mon, 9 Dec 2002 13:42:08 -0800 (PST) +X-Mailer: UserLand Frontier 8.0.5 (Macintosh OS) (mailServer v1.1..142) +Mime-Version: 1.0 +Message-Id: <88699896.1172681174@[4.42.179.151]> +X-authenticated-sender: erics +In-reply-to: <200212091153.03762.josh@agliodbs.com> +Date: Mon, 09 Dec 2002 13:42:02 -0800 +To: pgsql-performance@postgresql.org +From: eric soroos +Subject: Re: questions about disk configurations +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/94 +X-Sequence-Number: 510 + +> +> Er, no, it's not. In fact, for a 3-disk config, I reccommend: +> +> Disk 1: OS, swap, system logs +> Disk 2: Data + Indexes +> Disk 3: Transaction Log + +What is the accepted way of splitting the data from pg_xlog? + +I've been testing some configurations for low budget performance, and I haven't been able to make this help vs. one disk. (under osx, ymmv) + +I rsync'd the pg_xlog directory to another disk, then set up a symlink pointing from the data/pg_xlog to /other/disk/pg_xlog. + +I then got tps numbers that were 2/3 of the single ide drive speed. The only explanation I can come up with is that something is seeking to the symlink, then doing the actual write on the other drive. + +I'm going to try this under linux using mount points, but I need to shuffle hardware first. + + +any ideas? + +eric + + + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 16:59:18 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 72395476454 + for ; + Mon, 9 Dec 2002 16:59:16 -0500 (EST) +Received: from joeconway.com (unknown [63.210.180.150]) + by postgresql.org (Postfix) with ESMTP id B822A476576 + for ; + Mon, 9 Dec 2002 16:49:57 -0500 (EST) +Received: from [206.19.64.3] (account jconway HELO joeconway.com) + by joeconway.com (CommuniGate Pro SMTP 3.5.9) + with ESMTP-TLS id 1474303; Mon, 09 Dec 2002 14:29:06 -0800 +Message-ID: <3DF50FA5.3090000@joeconway.com> +Date: Mon, 09 Dec 2002 13:48:21 -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: Tom Lane +Cc: Josh Berkus , pgsql-performance@postgresql.org +Subject: Re: Speeding up aggregates +References: + <12845.1039207565@sss.pgh.pa.us> <3DF39F8B.4050801@joeconway.com> + <19749.1039469192@sss.pgh.pa.us> +In-Reply-To: <19749.1039469192@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: 200212/95 +X-Sequence-Number: 511 + +Tom Lane wrote: +> Joe Conway writes: +> +>>Just to follow up on my last post, I did indeed find that bumping up sort_mem +>>caused a switch back to HashAggregate, and a big improvement: +> +> +>>parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +>>i, iwhs w where i.part_id = w.part_id group by i.part_id having sum(w.qty_oh) > 0; +>> QUERY PLAN +>>---------------------------------------------------------------------------------------------------------------------------- +>> HashAggregate (cost=5254.46..5432.10 rows=35528 width=36) (actual +>>time=1286.89..1399.36 rows=4189 loops=1) +>> Filter: (sum(qty_oh) > 0::double precision) +>> -> Hash Join (cost=1319.10..4710.31 rows=72553 width=36) (actual +>>time=163.36..947.54 rows=72548 loops=1) +> +> +> How many rows out if you drop the HAVING clause? + +parts=# set sort_mem to 8000; +SET +parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +i, iwhs w where i.part_id = w.part_id group by i.part_id; + QUERY PLAN +---------------------------------------------------------------------------------------------------------------------------- + HashAggregate (cost=5617.22..5706.04 rows=35528 width=36) (actual +time=1525.93..1627.41 rows=34575 loops=1) + -> Hash Join (cost=1319.10..5254.45 rows=72553 width=36) (actual +time=156.86..1248.73 rows=72548 loops=1) + Hash Cond: ("outer".part_id = "inner".part_id) + -> Seq Scan on iwhs w (cost=0.00..2121.53 rows=72553 width=22) +(actual time=0.01..274.00 rows=72553 loops=1) + -> Hash (cost=1230.28..1230.28 rows=35528 width=14) (actual +time=156.65..156.65 rows=0 loops=1) + -> Seq Scan on inv i (cost=0.00..1230.28 rows=35528 +width=14) (actual time=0.03..86.86 rows=35528 loops=1) + Total runtime: 1680.86 msec +(7 rows) + + +> The planner's choice of which to use is dependent on its estimate of the +> required hashtable size, which is proportional to its guess about how +> many distinct groups there will be. The above output doesn't tell us +> that however, only how many groups passed the HAVING clause. I'm +> curious about the quality of this estimate, since the code to try to +> generate not-completely-bogus group count estimates is all new ... + +If I'm reading it correctly, it looks like the estimate in this case is pretty +good. + +Joe + + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 17:11:25 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4FF2347610D + for ; + Mon, 9 Dec 2002 17:11:23 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id EA249475A1E + for ; + Mon, 9 Dec 2002 17:06:54 -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 gB9M6opd020089; + Mon, 9 Dec 2002 17:06:50 -0500 (EST) +To: Joe Conway +Cc: Josh Berkus , pgsql-performance@postgresql.org +Subject: Re: Speeding up aggregates +In-reply-to: <3DF50FA5.3090000@joeconway.com> +References: + <12845.1039207565@sss.pgh.pa.us> <3DF39F8B.4050801@joeconway.com> + <19749.1039469192@sss.pgh.pa.us> <3DF50FA5.3090000@joeconway.com> +Comments: In-reply-to Joe Conway + message dated "Mon, 09 Dec 2002 13:48:21 -0800" +Date: Mon, 09 Dec 2002 17:06:50 -0500 +Message-ID: <20088.1039471610@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/96 +X-Sequence-Number: 512 + +Joe Conway writes: +>> How many rows out if you drop the HAVING clause? + +> parts=# set sort_mem to 8000; +> SET +> parts=# explain analyze select i.part_id, sum(w.qty_oh) as total_oh from inv +> i, iwhs w where i.part_id = w.part_id group by i.part_id; +> QUERY PLAN +> ---------------------------------------------------------------------------------------------------------------------------- +> HashAggregate (cost=5617.22..5706.04 rows=35528 width=36) (actual +> time=1525.93..1627.41 rows=34575 loops=1) +> -> Hash Join (cost=1319.10..5254.45 rows=72553 width=36) (actual +> time=156.86..1248.73 rows=72548 loops=1) + + +>> The planner's choice of which to use is dependent on its estimate of the +>> required hashtable size, which is proportional to its guess about how +>> many distinct groups there will be. The above output doesn't tell us +>> that however, only how many groups passed the HAVING clause. I'm +>> curious about the quality of this estimate, since the code to try to +>> generate not-completely-bogus group count estimates is all new ... + +> If I'm reading it correctly, it looks like the estimate in this case is pretty +> good. + +Better than I had any right to expect ;-). Thanks. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Mon Dec 9 17:15:28 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B48BC476452 + for ; + Mon, 9 Dec 2002 17:15:26 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id E5BC54764ED + for ; + Mon, 9 Dec 2002 17:10:59 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2273841; Mon, 09 Dec 2002 14:11:03 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: eric soroos , + pgsql-performance@postgresql.org +Subject: Re: questions about disk configurations +Date: Mon, 9 Dec 2002 14:14:30 -0800 +X-Mailer: KMail [version 1.4] +References: <88699896.1172681174@[4.42.179.151]> +In-Reply-To: <88699896.1172681174@[4.42.179.151]> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212091414.30418.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/97 +X-Sequence-Number: 513 + + +Eric, + +> I'm going to try this under linux using mount points, but I need to shuff= +le=20 +hardware first.=20 + +This is the only way I've done it. I'm not sure what the Mac problem is. + + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 17:36:43 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B7CB847666D + for ; + Mon, 9 Dec 2002 17:36:41 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id 26D404762F9 + for ; + Mon, 9 Dec 2002 17:27:30 -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 gB9MQ6vp005553; + Mon, 9 Dec 2002 15:26:07 -0700 (MST) +Date: Mon, 9 Dec 2002 15:22:11 -0700 (MST) +From: "scott.marlowe" +To: eric soroos +Cc: +Subject: Re: questions about disk configurations +In-Reply-To: <88699896.1172681174@[4.42.179.151]> +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: 200212/98 +X-Sequence-Number: 514 + +On Mon, 9 Dec 2002, eric soroos wrote: + +> > +> > Er, no, it's not. In fact, for a 3-disk config, I reccommend: +> > +> > Disk 1: OS, swap, system logs +> > Disk 2: Data + Indexes +> > Disk 3: Transaction Log +> +> What is the accepted way of splitting the data from pg_xlog? + +You really can't split it so to speak. It all needs to be in one place. +Or do you mean splitting the load? Maybe putting it onto a RAID0 +partition, but that's chancy. + +> I've been testing some configurations for low budget performance, and I +> haven't been able to make this help vs. one disk. (under osx, ymmv) + +I haven't found anything that helps much either, except for fast drives. + +You can, however, turn on the noatime mounting option under Linux (BSD has +something similar) and it should help speed things up on any file system. +You can also try turning on the async option, but I'm not sure this is a +problem or not for data integrity on a transaction log file system. +Comments? + +> I rsync'd the pg_xlog directory to another disk, then set up a symlink +> pointing from the data/pg_xlog to /other/disk/pg_xlog. +> +> I then got tps numbers that were 2/3 of the single ide drive speed. The +> only explanation I can come up with is that something is seeking to the +> symlink, then doing the actual write on the other drive. + +rsync isn't still running is it? you can just use the cp command while +the database is shut down to move the pg_xlog dir. like so: + +pg_ctl stop +mkdir /mnt/bigdog/pg_xlog +chown postgres.postgres /mnt/bigdog/pg_xlog +chmod 700 /mnt/bigdog/pg_xlog +cd $PGDATA +cp -Rfp pg_xlog/* /mnt/bigdog/pg_xlog/ +mv pg_xlog pg_xlog.old (I always keep stuff till I'm sure I really don't +need it.) +ln -s /mnt/bigdog/pg_xlog pg_xlog +pg_ctl start + + + +Don't forget, noatime in the mount options, makes a big difference. + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 17:59:37 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2A73D475E2B + for ; + Mon, 9 Dec 2002 17:59:36 -0500 (EST) +Received: from l2.socialecology.com (unknown [4.42.179.131]) + by postgresql.org (Postfix) with ESMTP id 00A1347661B + for ; + Mon, 9 Dec 2002 17:44:35 -0500 (EST) +Received: from 4.42.179.151 (broccoli.socialecology.com [4.42.179.151]) + by l2.socialecology.com (Postfix) with SMTP + id 47CFE29068B; Mon, 9 Dec 2002 14:44:36 -0800 (PST) +X-Mailer: UserLand Frontier 8.0.5 (Macintosh OS) (mailServer v1.1..142) +Mime-Version: 1.0 +Message-Id: <88924842.1172677425@[4.42.179.151]> +X-authenticated-sender: erics +In-reply-to: +Date: Mon, 09 Dec 2002 14:44:31 -0800 +To: scott.marlowe , eric soroos +Cc: pgsql-performance@postgresql.org +From: eric soroos +Subject: Re: questions about disk configurations +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/99 +X-Sequence-Number: 515 + + + +> > I've been testing some configurations for low budget performance, and I +> > haven't been able to make this help vs. one disk. (under osx, ymmv) +> +> I haven't found anything that helps much either, except for fast drives. + + +> +> You can, however, turn on the noatime mounting option under Linux (BSD has +> something similar) and it should help speed things up on any file system. + +I don't think that's an option for osx/hfs mounts, at least mount doesn't list it. (not that mount really works on 10.1.x, but whatever) + +> You can also try turning on the async option, but I'm not sure this is a +> problem or not for data integrity on a transaction log file system. +> Comments? + +from man mount: + + async All I/O to the file system should be done asynchronously. + This is a dangerous flag to set, and should not be used + unless you are prepared to recreate the file system + should your system crash. + + +I'd guess that this is about the same as fsync = off, except that it's your os lying to you instead of your database. + +> +> > I rsync'd the pg_xlog directory to another disk, then set up a symlink +> > pointing from the data/pg_xlog to /other/disk/pg_xlog. +> > +> > I then got tps numbers that were 2/3 of the single ide drive speed. The +> > only explanation I can come up with is that something is seeking to the +> > symlink, then doing the actual write on the other drive. +> +> rsync isn't still running is it? you can just use the cp command while +> the database is shut down to move the pg_xlog dir. like so: + +rsync == copy, it's just that I remember the command line switches for it. + +> pg_ctl stop +> mkdir /mnt/bigdog/pg_xlog +> chown postgres.postgres /mnt/bigdog/pg_xlog +> chmod 700 /mnt/bigdog/pg_xlog +> cd $PGDATA +> cp -Rfp pg_xlog/* /mnt/bigdog/pg_xlog/ +> mv pg_xlog pg_xlog.old (I always keep stuff till I'm sure I really don't +> need it.) +> ln -s /mnt/bigdog/pg_xlog pg_xlog +> pg_ctl start +> + +This is about what I did, except that /mnt/bigdog/pg_xlog == /Volumes/scsi1. + +Where you can do something different is mount bigdog at data/pg_xlog, instead of using the symlinks. Given the interesting state of filesystem tools under osx, I can't really do that. (at least under 10.1.5, looks like the laptop running 10.2 has a little more info. not that the laptop has room for a 3.5" 10k rpm scsi drive & pci scsi card for testing...) + +eric + + + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 18:06:44 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 52ECC475FD9 + for ; + Mon, 9 Dec 2002 18:06:41 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id 35114476058 + for ; + Mon, 9 Dec 2002 18:06:18 -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 gB9N4Rvp029771; + Mon, 9 Dec 2002 16:04:28 -0700 (MST) +Date: Mon, 9 Dec 2002 16:00:32 -0700 (MST) +From: "scott.marlowe" +To: Josh Berkus +Cc: , +Subject: Re: questions about disk configurations +In-Reply-To: <200212091153.03762.josh@agliodbs.com> +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: 200212/100 +X-Sequence-Number: 516 + +On Mon, 9 Dec 2002, Josh Berkus wrote: + +> +> Depesz, +> +> > i have a question about best harddisk configuration for postgresql +> > performance. +> > of course i know that: +> > - scsi is better than ide +> > - 2 disks are better than 1 +> > - 3 disks are better than 2 +> > +> > i know that with 3 disks one should move xlog to one drive, index files +> > to second and tables to third. +> > that's clear. +> +> Er, no, it's not. In fact, for a 3-disk config, I reccommend: +> +> Disk 1: OS, swap, system logs +> Disk 2: Data + Indexes +> Disk 3: Transaction Log + +Actually, first I'd try one big RAID 5 and see how it runs. THEN I'd +spend time mucking around with different configs if that wasn't fast +enough. If you need x performance and get 10x with a RAID 5 then move on +to more interesting problems. + +> > but: +> > will making software raid on this discs provide performance increase or +> > decrease? +> +> Hardware RAID can improve *read* performance, particilarly RAIDs 1, 01, and +> 10. For writing, the best you can do is having it not inhibit performance. +> The general testament is that *software* RAID does not improve things at all; +> actually, the best that can be said for Linux Software RAID 1 is that it does +> not harm performance much. + +Not in my experience. I'd estimate my test box with dual 18 Gig UW scsis +runs about 1.5 to 1.8 times faster with the two drives in a RAID1 as if +a single one is used. Bonnie confirms this. single drive can read about +25 Megs a second, a pair in a RAID1 reads at about 48 Megs a second. + +But as you pointed out in your reply, it's more important to look at how +he's gonna drive the database. If it has to input hundreds of short +queries a second, that's a whole different problem than a data warehouse +with 500 people throwing 8 way joins at the data all day. + + + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 18:28:12 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 87CC647662D + for ; + Mon, 9 Dec 2002 18:28:11 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 776D84763B8 + for ; + Mon, 9 Dec 2002 18:23:05 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2274028; Mon, 09 Dec 2002 15:23:09 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: "scott.marlowe" +Subject: Re: questions about disk configurations +Date: Mon, 9 Dec 2002 15:26:36 -0800 +X-Mailer: KMail [version 1.4] +Cc: , +References: +In-Reply-To: +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212091526.36232.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/101 +X-Sequence-Number: 517 + + +Scott, + +> Actually, first I'd try one big RAID 5 and see how it runs. THEN I'd=20 +> spend time mucking around with different configs if that wasn't fast=20 +> enough. If you need x performance and get 10x with a RAID 5 then move on= +=20 +> to more interesting problems. + +Depends on how much time you have to spend re-installing. IMHO, RAID 5 is= +=20 +slower that straight disks for Postgres, especially with large numbers of= +=20 +writes. This may not be true for $1000 RAID controllers, but I have yet to= +=20 +use one. + +I have a box with a low-end RAID 5 controller, and it drives like a single = +IDE=20 +drive on large UPDATE queries. Slower, somethimes. + +> Not in my experience. I'd estimate my test box with dual 18 Gig UW scsis= +=20 +> runs about 1.5 to 1.8 times faster with the two drives in a RAID1 as if= +=20 +> a single one is used. Bonnie confirms this. single drive can read about= +=20 +> 25 Megs a second, a pair in a RAID1 reads at about 48 Megs a second. + +This is Linux software RAID? + +> But as you pointed out in your reply, it's more important to look at how= +=20 +> he's gonna drive the database. If it has to input hundreds of short=20 +> queries a second, that's a whole different problem than a data warehouse= +=20 +> with 500 people throwing 8 way joins at the data all day. + +Definitely. + +--=20 +-Josh Berkus + +______AGLIO DATABASE SOLUTIONS___________________________ + Josh Berkus + Complete information technology josh@agliodbs.com + and data management solutions (415) 565-7293 + for law firms, small businesses fax 621-2533 + and non-profit organizations. San Francisco + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 19:19:47 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3BDF1476515 + for ; + Mon, 9 Dec 2002 19:19:45 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id 2002C47673E + for ; + Mon, 9 Dec 2002 19:11:09 -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 gBA0AGvp004250; + Mon, 9 Dec 2002 17:10:16 -0700 (MST) +Date: Mon, 9 Dec 2002 17:06:20 -0700 (MST) +From: "scott.marlowe" +To: Josh Berkus +Cc: , +Subject: Re: questions about disk configurations +In-Reply-To: <200212091526.36232.josh@agliodbs.com> +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: 200212/103 +X-Sequence-Number: 519 + +On Mon, 9 Dec 2002, Josh Berkus wrote: + +> +> Scott, +> +> > Actually, first I'd try one big RAID 5 and see how it runs. THEN I'd +> > spend time mucking around with different configs if that wasn't fast +> > enough. If you need x performance and get 10x with a RAID 5 then move on +> > to more interesting problems. +> +> Depends on how much time you have to spend re-installing. IMHO, RAID 5 is +> slower that straight disks for Postgres, especially with large numbers of +> writes. This may not be true for $1000 RAID controllers, but I have yet to +> use one. + +Even the fastest RAID 5 boxes aren't superfast, but a RAID5 of 15k drives +with a lot of drive in it does OK, since it can 1: spread small writes +around on many different drives (i.e. if you have 12 drives, and a lot of +small writes, a lot of them will be on different drives.) as well as +spreading out random reads, while providing good large reads, i.e. +sequential scans. + +The key to good RAID 5 is to throw as many drives as you possibly can at a +problem, preferably across several SCSI interfaces. Or FC-AL. + +> I have a box with a low-end RAID 5 controller, and it drives like a single IDE +> drive on large UPDATE queries. Slower, somethimes. + +Many low end RAID 5 controllers are pretty slow. The adaptec AIC133 +series (I think that's the right number) are total dogs. The older AMI +Mega raids were fast for their day, but any decent 350 MHz machine with a +dual channed SymBIOS card will outrun it at RAID 5. + +> > Not in my experience. I'd estimate my test box with dual 18 Gig UW scsis +> > runs about 1.5 to 1.8 times faster with the two drives in a RAID1 as if +> > a single one is used. Bonnie confirms this. single drive can read about +> > 25 Megs a second, a pair in a RAID1 reads at about 48 Megs a second. +> +> This is Linux software RAID? + +Yep. The kernel level drivers are quite fast in my experience, but they +don't seem to give any improvement when layered (i.e. 1+0 or 0+1) over +whatever is the slowest of the two layers. I.e. setting up a RAID5 of +RAID0s results in almost the exact same performance as if you'd just setup +the same number of drives under RAID 5 as you had mirror sets in RAID0. +Since this is the case, you get better performance just going to RAID 5 +with twice the disks and twice (-1n) the space. + + + +From pgsql-performance-owner@postgresql.org Mon Dec 9 19:13:40 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 04E8D4762E9 + for ; + Mon, 9 Dec 2002 19:13:39 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id C7A25476489 + for ; + Mon, 9 Dec 2002 19:08:02 -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 gBA083pd020996; + Mon, 9 Dec 2002 19:08:04 -0500 (EST) +To: josh@agliodbs.com +Cc: eric soroos , + pgsql-performance@postgresql.org +Subject: Re: questions about disk configurations +In-reply-to: <200212091414.30418.josh@agliodbs.com> +References: <88699896.1172681174@[4.42.179.151]> + <200212091414.30418.josh@agliodbs.com> +Comments: In-reply-to Josh Berkus + message dated "Mon, 09 Dec 2002 14:14:30 -0800" +Date: Mon, 09 Dec 2002 19:08:03 -0500 +Message-ID: <20995.1039478883@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/102 +X-Sequence-Number: 518 + +Josh Berkus writes: +>> I'm going to try this under linux using mount points, but I need to shuffle +> hardware first. + +> This is the only way I've done it. I'm not sure what the Mac problem is. + +It sounds like OS X fails to optimize repeated lookups of the same +symlink. I haven't tried to do any performance measurement of this +myself, but if true a gripe to Apple would be in order. Most of the +designs I've seen for clean tablespace handling will depend on symlinks +much more than we do today, so a performance penalty for symlinks will +*really* hurt further down the road. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Dec 10 11:55:29 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0D78E4764D8 + for ; + Tue, 10 Dec 2002 11:55:27 -0500 (EST) +Received: from web80305.mail.yahoo.com (web80305.mail.yahoo.com + [66.218.79.21]) + by postgresql.org (Postfix) with SMTP id 49F46476485 + for ; + Tue, 10 Dec 2002 11:55:26 -0500 (EST) +Message-ID: <20021210165531.67062.qmail@web80305.mail.yahoo.com> +Received: from [203.87.150.116] by web80305.mail.yahoo.com via HTTP; + Tue, 10 Dec 2002 08:55:31 PST +Date: Tue, 10 Dec 2002 08:55:31 -0800 (PST) +From: Ludwig Lim +Subject: Performance of multi-column index on INSERT +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: 200212/104 +X-Sequence-Number: 520 + +Hi: + + Is the performance overhead of creating a +multi-column index greater than creating an individual +index for each column? (i.e. Is the INSERT slower for +a table with a three column index than a similar table +with three single column indices?). + + I was wondering this because according to +PostgreSQL Manual in the section on multi-columned +indexes "Multicolumn indexes should be used sparingly. +Most of the time, an index on a single column is +sufficient and saves space and time". + + +Thank you very much, + +ludwig + + +__________________________________________________ +Do you Yahoo!? +New DSL Internet Access from SBC & Yahoo! +http://sbc.yahoo.com + +From pgsql-performance-owner@postgresql.org Tue Dec 10 15:50:24 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 67121476448 + for ; + Tue, 10 Dec 2002 15:50:23 -0500 (EST) +Received: from rh72.home.ee (adsl1030.estpak.ee [213.168.29.11]) + by postgresql.org (Postfix) with ESMTP id 6E7D3476371 + for ; + Tue, 10 Dec 2002 15:50:22 -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 gBAKoN3c002086; + Wed, 11 Dec 2002 01:50:23 +0500 +Received: (from hannu@localhost) + by rh72.home.ee (8.12.5/8.12.5/Submit) id gBAKoMZS002084; + Wed, 11 Dec 2002 01:50:22 +0500 +X-Authentication-Warning: rh72.home.ee: hannu set sender to hannu@tm.ee using + -f +Subject: Re: Performance of multi-column index on INSERT +From: Hannu Krosing +To: Ludwig Lim +Cc: PostgreSQL Mailing List +In-Reply-To: <20021210165531.67062.qmail@web80305.mail.yahoo.com> +References: <20021210165531.67062.qmail@web80305.mail.yahoo.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039553422.1945.10.camel@rh72.home.ee> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 11 Dec 2002 01:50:22 +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/105 +X-Sequence-Number: 521 + +Ludwig Lim kirjutas T, 10.12.2002 kell 21:55: +> Hi: +> +> Is the performance overhead of creating a +> multi-column index greater than creating an individual +> index for each column? (i.e. Is the INSERT slower for +> a table with a three column index than a similar table +> with three single column indices?). +> +> I was wondering this because according to +> PostgreSQL Manual in the section on multi-columned +> indexes "Multicolumn indexes should be used sparingly. +> Most of the time, an index on a single column is +> sufficient and saves space and time". + +You should create only as much indexes as you really need. + +A multi-column index can not usually replace multiple single column +indexes and vice versa. + +For example, while an index on a,b,c can be used for search on both a +and b it will not be used for search on b and c and will be used like +index on a for search on a and c. + +While a multi-column index is slower than a single-column one, it is +definitely faster than multiple single column indexes - one 3-column +index should always be faster than 3 single-column indexes. + +Also, currently even with multiple single-column indexes on a,b and c +the search on a and c will use only one index, either on a or c. + +> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Tue Dec 10 16:17:00 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 68863476921 + for ; + Tue, 10 Dec 2002 16:16:59 -0500 (EST) +Received: from spike.esolution.pl (spike.esolution.pl [217.11.134.154]) + by postgresql.org (Postfix) with ESMTP id E91634769DA + for ; + Tue, 10 Dec 2002 16:16:37 -0500 (EST) +Received: from [80.50.72.15] (helo=depesz.pl ident=exim) + by spike.esolution.pl with esmtp (Exim 4.10) id 18Lrk1-0006Pi-00 + for pgsql-performance@postgresql.org; Tue, 10 Dec 2002 22:16:33 +0100 +Received: from depesz by depesz.pl with local (Exim 3.36 #1) + id 18LrjX-0005q7-00 + for pgsql-performance@postgresql.org; Tue, 10 Dec 2002 22:16:03 +0100 +Date: Tue, 10 Dec 2002 22:16:03 +0100 +From: Hubert depesz Lubaczewski +To: pgsql-performance@postgresql.org +Subject: Re: questions about disk configurations +Message-ID: <20021210211603.GA22257@depesz.pl> +Reply-To: depesz@depesz.pl +References: <20021209113231.GA1113@depesz.pl> +Mime-Version: 1.0 +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; boundary="x+6KMIRAuhnl3hBn" +Content-Disposition: inline +In-Reply-To: <20021209113231.GA1113@depesz.pl> +User-Agent: Mutt/1.4i +X-info-en-1: this message *may* reflect my personal opinion. it is *not* +X-info-en-2: intended to reflect those of my employer, or anyone else. +X-info-pl-1: wszelkie opinie =?iso-8859-2?Q?wyra=BFone_?= + =?iso-8859-2?Q?w_tym_li=B6cie_prezentuj=B1_wy=B3=B1cznie_pogl=B1dy?= +X-info-pl-2: autora listu. opinie =?iso-8859-2?Q?te_?= + =?iso-8859-2?Q?w_=BFadnym__razie_nie__wyra=BFaj=B1__pogl=B1d=F3w?= +X-info-pl-3: pracodawcy autora =?iso-8859-2?Q?listu_?= + =?iso-8859-2?Q?_ani__innych__zwi=B1zanych__z__nim__os=F3b=2E?= +X-Operating-System: Linux 2.4.18 i686 Pentium_III_(Coppermine) +X-Spam-Score: -2.9 (--) +X-Scanner: exiscan for exim4 (http://duncanthrax.net/exiscan/) + *18Lrk1-0006Pi-00*D8dz6WEgjiw* +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/106 +X-Sequence-Number: 522 + +--x+6KMIRAuhnl3hBn +Content-Type: text/plain; charset=iso-8859-2 +Content-Disposition: inline +Content-Transfer-Encoding: quoted-printable + +i'm replying to my own letter to gather all replies in one mail. + +i got some replies. some of them are useful. some aren't really. i'm not +really sure how the usage can modify "what is best for some part of +database files". +can you explain me how comes that for some uses it's best +(performance-wise) to keep xlog's on straight disc, and tables on raid5 +with lots' of disks, and for some other uses it's better to keep xlog on +raid0 and tables on raid 10? + +anyway: what i understood is that usually the best (performance-wise), +would be to put: +xlog - separate - unraid'ed disk, or raid0 +tables - any raid, but not raid 1 +indices - any raid, but not raid 1 + +thanks for all replies. + +depesz + +--=20 +hubert depesz lubaczewski http://www.depesz.pl/ +------------------------------------------------------------------------ +M=F3j Bo=BFe, spraw abym milcza=B3, dop=F3ki si=EA nie upewni=EA, =BFe na= +prawd=EA mam +co=B6 do powiedzenia. (c) 1998 depesz + + +--x+6KMIRAuhnl3hBn +Content-Type: application/pgp-signature +Content-Disposition: inline + +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1.2.1 (GNU/Linux) + +iD8DBQE99lmTKBwKA0prOAkRAtIOAJ98YH1xgmVRaSMI6l/SurCjUGxXSwCfRjEj +DxkNuu7oBFr7XinRz+XPxFY= +=uf1p +-----END PGP SIGNATURE----- + +--x+6KMIRAuhnl3hBn-- + +From pgsql-performance-owner@postgresql.org Tue Dec 10 18:13:37 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 83D83476592 + for ; + Tue, 10 Dec 2002 18:13:35 -0500 (EST) +Received: from lakemtao02.cox.net (lakemtao02.cox.net [68.1.17.243]) + by postgresql.org (Postfix) with ESMTP id DBD15476196 + for ; + Tue, 10 Dec 2002 18:13:34 -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 <20021210231337.HOFM2203.lakemtao02.cox.net@[192.168.1.1]> + for ; + Tue, 10 Dec 2002 18:13:37 -0500 +Subject: Re: questions about disk configurations +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <20021210211603.GA22257@depesz.pl> +References: <20021209113231.GA1113@depesz.pl> + <20021210211603.GA22257@depesz.pl> +Content-Type: text/plain +Organization: +Message-Id: <1039562015.27243.304.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 10 Dec 2002 17:13:35 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/107 +X-Sequence-Number: 523 + +On Tue, 2002-12-10 at 15:16, Hubert depesz Lubaczewski wrote: +[snip] +> anyway: what i understood is that usually the best (performance-wise), +> would be to put: +> xlog - separate - unraid'ed disk, or raid0 + +Unless your data is *easily* recreatable, NEVER RAID0!! + +> tables - any raid, but not raid 1 +> indices - any raid, but not raid 1 + +Why not RAID1 (mirroring)? It speeds up both reads and writes. + +Things are also dependent on the RAID controller, since they +all have different strengths and weaknesses. + +-- ++---------------------------------------------------------------+ +| 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 Dec 11 00:20:28 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5D0D9476B96 + for ; + Wed, 11 Dec 2002 00:20:25 -0500 (EST) +Received: from mail1.acecape.com (mail1.acecape.com [66.114.74.12]) + by postgresql.org (Postfix) with ESMTP id 4703E4761E2 + for ; + Wed, 11 Dec 2002 00:19:39 -0500 (EST) +Received: from PASCAL.kencast.com (p67-47.acedsl.com [66.114.67.47]) + by mail1.acecape.com (8.12.2/8.12.2) with ESMTP id gBB5JitB025501 + for ; Wed, 11 Dec 2002 00:19:44 -0500 +Message-Id: <5.1.1.6.0.20021210234537.00bae260@mail.futuris.net> +X-Sender: wweng@mail.futuris.net (Unverified) +X-Mailer: QUALCOMM Windows Eudora Version 5.1.1 +Date: Wed, 11 Dec 2002 00:20:57 -0500 +To: PgSQL Performance ML +From: Wei Weng +Subject: Which of the solution is better? +In-Reply-To: <1039562015.27243.304.camel@haggis> +References: <20021210211603.GA22257@depesz.pl> + <20021209113231.GA1113@depesz.pl> + <20021210211603.GA22257@depesz.pl> +Mime-Version: 1.0 +Content-Type: text/plain; charset="us-ascii"; format=flowed +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/108 +X-Sequence-Number: 524 + +I have two tables A and B where A is a huge table with thousands of rows, B +is a small table with only a couple of entries. + +I want to do something like + +SELECT + A.ID + A.Name +FROM + A JOIN B ON (A.ID = B.ID) + +And on the other hand I can have something like this + +SELECT + A.ID + A.Name +FROM + A +WHERE + A.ID IN (B_Id_List) + +B_Id_List is a string concatenation of B.ID. (ie, 1,2,3,4,5 ...) + +Which one is faster, more efficient? + +And if you could, which one is faster/more efficient under MS SQL Server 7? +I am trying to develop a cross platform query, that is why I need to +concern with performance under different databases. + +Thanks a lot! + +Wei + + +From pgsql-performance-owner@postgresql.org Wed Dec 11 00:46:04 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 01434475CED + for ; + Wed, 11 Dec 2002 00:46:03 -0500 (EST) +Received: from lakemtao04.cox.net (lakemtao04.cox.net [68.1.17.241]) + by postgresql.org (Postfix) with ESMTP id 6AE1E4758DC + for ; + Wed, 11 Dec 2002 00:46:02 -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 <20021211054607.ZLN1248.lakemtao04.cox.net@[192.168.1.1]> + for ; + Wed, 11 Dec 2002 00:46:07 -0500 +Subject: Re: Which of the solution is better? +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <5.1.1.6.0.20021210234537.00bae260@mail.futuris.net> +References: <20021210211603.GA22257@depesz.pl> + <20021209113231.GA1113@depesz.pl> <20021210211603.GA22257@depesz.pl> + <5.1.1.6.0.20021210234537.00bae260@mail.futuris.net> +Content-Type: text/plain +Organization: +Message-Id: <1039585564.1265.38.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 10 Dec 2002 23:46:04 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/109 +X-Sequence-Number: 525 + +On Tue, 2002-12-10 at 23:20, Wei Weng wrote: +> I have two tables A and B where A is a huge table with thousands of rows, B +> is a small table with only a couple of entries. +> +> I want to do something like +> +> SELECT +> A.ID +> A.Name +> FROM +> A JOIN B ON (A.ID = B.ID) + +How is this query any different from: +SELECT + A.ID, + A.Name +FROM + A, + B +WHERE + A.ID = B.ID + +> And on the other hand I can have something like this +> +> SELECT +> A.ID +> A.Name +> FROM +> A +> WHERE +> A.ID IN (B_Id_List) +> +> B_Id_List is a string concatenation of B.ID. (ie, 1,2,3,4,5 ...) +> +> Which one is faster, more efficient? +> +> And if you could, which one is faster/more efficient under MS SQL Server 7? +> I am trying to develop a cross platform query, that is why I need to +> concern with performance under different databases. + +-- ++---------------------------------------------------------------+ +| 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 Dec 11 10:48:25 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3BB0A4761E9 + for ; + Wed, 11 Dec 2002 10:48:24 -0500 (EST) +Received: from mail.libertyrms.com (unknown [209.167.124.227]) + by postgresql.org (Postfix) with ESMTP id 997C9476117 + for ; + Wed, 11 Dec 2002 10:48:23 -0500 (EST) +Received: from andrew by mail.libertyrms.com with local (Exim 3.22 #3 + (Debian)) + id 18M964-0001av-00 + for ; Wed, 11 Dec 2002 10:48:28 -0500 +Date: Wed, 11 Dec 2002 10:48:28 -0500 +From: Andrew Sullivan +To: PgSQL Performance ML +Subject: Re: Which of the solution is better? +Message-ID: <20021211104828.F31768@mail.libertyrms.com> +Mail-Followup-To: Andrew Sullivan , + PgSQL Performance ML +References: <20021210211603.GA22257@depesz.pl> + <20021209113231.GA1113@depesz.pl> + <20021210211603.GA22257@depesz.pl> + <5.1.1.6.0.20021210234537.00bae260@mail.futuris.net> + <1039585564.1265.38.camel@haggis> <1039623980.17037.3.camel@Monet> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.2.5i +In-Reply-To: <1039623980.17037.3.camel@Monet>; + from wweng@kencast.com on Wed, Dec 11, 2002 at 11:26:20AM -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/111 +X-Sequence-Number: 527 + +On Wed, Dec 11, 2002 at 11:26:20AM -0500, Wei Weng wrote: +> I don't think there is any. It is just another way to write an outer +> join. + +That's not exactly true. Doing A JOIN B ON (A.ID=B.ID) constrains +the planner. See the section on explicit join order in the +PostgreSQL manual. + +The IN locution, by the way, is almost always bad in Postgres. Avoid +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 Wed Dec 11 10:28:40 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B4F9B47690C + for ; + Wed, 11 Dec 2002 10:28:38 -0500 (EST) +Received: from mta5.snet.net (mta5.snet.net [204.60.203.77]) + by postgresql.org (Postfix) with ESMTP id 10E46476AEF + for ; + Wed, 11 Dec 2002 10:26:27 -0500 (EST) +Received: from pop.snet.net (pop.snet.net [204.60.203.72]) + by mta5.snet.net (8.12.3/8.12.3/SNET-mx-1.2/D-1.1.1.1/O-1.1.1.1) with + ESMTP id gBBFN1lh007129 for ; + Wed, 11 Dec 2002 10:23:07 -0500 (EST) +X-Originating-IP: [64.252.95.167] +X-SBCIS-MTA: [pop.snet.net] +Received: from [192.168.1.83] (167.95.252.64.snet.net [64.252.95.167]) + by pop.snet.net (8.12.3/8.12.3/SNET-pop-1.2/D-1.1.1.1/O-1.1.1.1) with + ESMTP id gBBFQHoq021756 for ; + Wed, 11 Dec 2002 10:26:18 -0500 (EST) +Subject: Re: Which of the solution is better? +From: Wei Weng +To: PgSQL Performance ML +In-Reply-To: <1039585564.1265.38.camel@haggis> +References: <20021210211603.GA22257@depesz.pl> + <20021209113231.GA1113@depesz.pl> <20021210211603.GA22257@depesz.pl> + <5.1.1.6.0.20021210234537.00bae260@mail.futuris.net> + <1039585564.1265.38.camel@haggis> +Content-Type: text/plain +Organization: +Message-Id: <1039623980.17037.3.camel@Monet> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 11 Dec 2002 11:26:20 -0500 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/110 +X-Sequence-Number: 526 + +I don't think there is any. It is just another way to write an outer +join. + +On Wed, 2002-12-11 at 00:46, Ron Johnson wrote: +> On Tue, 2002-12-10 at 23:20, Wei Weng wrote: +> > I have two tables A and B where A is a huge table with thousands of rows, B +> > is a small table with only a couple of entries. +> > +> > I want to do something like +> > +> > SELECT +> > A.ID +> > A.Name +> > FROM +> > A JOIN B ON (A.ID = B.ID) +> +> How is this query any different from: +> SELECT +> A.ID, +> A.Name +> FROM +> A, +> B +> WHERE +> A.ID = B.ID +> +> > And on the other hand I can have something like this +> > +> > SELECT +> > A.ID +> > A.Name +> > FROM +> > A +> > WHERE +> > A.ID IN (B_Id_List) +> > +> > B_Id_List is a string concatenation of B.ID. (ie, 1,2,3,4,5 ...) +> > +> > Which one is faster, more efficient? +> > +> > And if you could, which one is faster/more efficient under MS SQL Server 7? +> > I am trying to develop a cross platform query, that is why I need to +> > concern with performance under different databases. +-- +Wei Weng +Network Software Engineer +KenCast Inc. + + + +From pgsql-general-owner@postgresql.org Wed Dec 11 12:50:20 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 37521476295 + for ; + Wed, 11 Dec 2002 12:50:18 -0500 (EST) +Received: from smtp5.jaring.my (smtp5.jaring.my [61.6.32.55]) + by postgresql.org (Postfix) with ESMTP id 01BB547618C + for ; + Wed, 11 Dec 2002 12:50:17 -0500 (EST) +Received: from pc.localhost. (j153.crc25.jaring.my [61.6.98.167]) + by smtp5.jaring.my (8.12.6/8.12.6) with ESMTP id gBBHoJKd077125 + for ; + Thu, 12 Dec 2002 01:50:20 +0800 (MYT) + (envelope-from lyeoh@pop.jaring.my) +Message-Id: <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> +X-Sender: lyeoh@mbox.jaring.my +X-Mailer: QUALCOMM Windows Eudora Version 5.1 +Date: Thu, 12 Dec 2002 02:07:09 +0800 +To: pgsql-general@postgresql.org +From: Lincoln Yeoh +Subject: Docs: GIST +Mime-Version: 1.0 +Content-Type: text/plain; charset="us-ascii"; format=flowed +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/570 +X-Sequence-Number: 34485 + +I'm a bit confused. + +In 7.3 is it possible to use GIST without using any of the stuff in +contrib/? If it is, how can it be done and in which cases should it be done? + +The pgsql docs about indexes keep talking about GIST here and there, but I +can't seem to use them on anything. And there's no gist in the "ops" and +access method listing. + +Having the docs say Postgresql provides GIST as one of the four access +methods, GIST supports multicolumn indexes, GIST etc, is just confusing if +the docs pertaining to indexes don't also say that in a default postgresql +installation you cannot create an index using GIST (if you can actually +create a GIST index "out of box", how??). + +Another thing: is Eugene Selkov's 1998 message on GIST indexes in the 7.3 +docs (see GIST Indexes) still valid? There's mention of Postgresql 6.3 and +postgres95 there too. + +BTW, 7.3 is GREAT! Multiple col/row returns, prepare queries, schemas etc. +Also set enable_seq_scan=off can get rolled back to whatever it was before +now right? Cool, coz I have to force index use for a particular select. + +Thanks to the postgresql dev team and everyone involved! + +Cheerio, +Link. + + +From pgsql-performance-owner@postgresql.org Wed Dec 11 13:12:10 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5DAF5475BA1 + for ; + Wed, 11 Dec 2002 13:12:09 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id BBE66475461 + for ; + Wed, 11 Dec 2002 13:12:08 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2276930 for ; + Wed, 11 Dec 2002 10:12:21 -0800 +From: "Josh Berkus" +Subject: Capping CPU usage? +To: pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Wed, 11 Dec 2002 10:12:21 -0800 +Message-ID: +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: 200212/112 +X-Sequence-Number: 528 + +Folks: + +I had a new question from a client: is it possible to "cap" CPU usage + for PostgreSQL running on Linux? They don't care if the procedure + degrades Postgres performance, but they can't afford to have Postgres + take up more than 30% of processor for more than 400 milliseconds +(they + are running some real-time operations). + +I can't imagine that postmaster could do this, but I thought it there + might be some kind of Linux Kernel CPU quota option I haven't heard +of. + �Can anybody point me in the right direction? + +-Josh Berkus + +From pgsql-performance-owner@postgresql.org Wed Dec 11 13:25:59 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 48032476606 + for ; + Wed, 11 Dec 2002 13:25:58 -0500 (EST) +Received: from jester.senspire.com (unknown [216.208.117.7]) + by postgresql.org (Postfix) with ESMTP id A195C476B8C + for ; + Wed, 11 Dec 2002 13:25:10 -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 gBBIOlNs017881; + Wed, 11 Dec 2002 13:24:52 -0500 (EST) (envelope-from rbt@rbt.ca) +Subject: Re: Capping CPU usage? +From: Rod Taylor +To: Josh Berkus +Cc: Pgsql Performance +In-Reply-To: +References: +Content-Type: multipart/signed; micalg=pgp-sha1; + protocol="application/pgp-signature"; + boundary="=-S/TwCGtYsfeK0pboE8GV" +Organization: +Message-Id: <1039631086.17316.194.camel@jester> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 11 Dec 2002 13:24:47 -0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/114 +X-Sequence-Number: 530 + +--=-S/TwCGtYsfeK0pboE8GV +Content-Type: text/plain +Content-Transfer-Encoding: quoted-printable + +On Wed, 2002-12-11 at 13:12, Josh Berkus wrote: +> Folks: +>=20=20 +> I had a new question from a client: is it possible to "cap" CPU usage +> for PostgreSQL running on Linux? They don't care if the procedure +> degrades Postgres performance, but they can't afford to have Postgres +> take up more than 30% of processor for more than 400 milliseconds +> (they +> are running some real-time operations). +>=20=20 +> I can't imagine that postmaster could do this, but I thought it there +> might be some kind of Linux Kernel CPU quota option I haven't heard +> of. +> Can anybody point me in the right direction? + +Don't know about Linux, but BSD cannot do that. CPU limits are hard -- +once you hit it it'll dump the process. + +Anyway, would it be sufficient to simply reduce the priority of the +process? + +--=20 +Rod Taylor + +PGP Key: http://www.rbt.ca/rbtpub.asc + +--=-S/TwCGtYsfeK0pboE8GV +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) + +iD8DBQA994Lt6DETLow6vwwRAjCNAJ0XUgddPe0aDHQ3kEGd2xZM+v7ChACeJ6R5 +JOalZ5ujdYTOEKaApPJX1j0= +=HWEx +-----END PGP SIGNATURE----- + +--=-S/TwCGtYsfeK0pboE8GV-- + + +From pgsql-performance-owner@postgresql.org Wed Dec 11 13:24:07 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 72DA7476A6A + for ; + Wed, 11 Dec 2002 13:24:06 -0500 (EST) +Received: from smtp.inphact.com (smtp.inphact.com [67.105.52.11]) + by postgresql.org (Postfix) with ESMTP id 1EF0247618C + for ; + Wed, 11 Dec 2002 13:23:51 -0500 (EST) +Received: from cafes.net (unknown [192.168.109.38]) + by smtp.inphact.com (Postfix) with ESMTP + id 90017134002; Wed, 11 Dec 2002 12:10:29 -0600 (CST) +Date: Wed, 11 Dec 2002 12:27:45 -0600 +Subject: Re: Capping CPU usage? +Content-Type: text/plain; charset=ISO-8859-1; format=flowed +Mime-Version: 1.0 (Apple Message framework v548) +Cc: pgsql-performance@postgresql.org +To: "Josh Berkus" +From: Cory 'G' Watson +In-Reply-To: +Message-Id: <3DFF224C-0D36-11D7-8019-0003939CCA58@cafes.net> +Content-Transfer-Encoding: quoted-printable +X-Mailer: Apple Mail (2.548) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/113 +X-Sequence-Number: 529 + + +On Wednesday, December 11, 2002, at 12:12 PM, Josh Berkus wrote: +> I can't imagine that postmaster could do this, but I thought it there +> might be some kind of Linux Kernel CPU quota option I haven't heard +> of. +> =A0Can anybody point me in the right direction? +> + +You can always use nice(1) to lower it's priority. This would allow=20 +other processes to get the CPU more often, effectively limiting it in=20 +the face of more demanding processes. + +ulimit has a CPU time option, but it's probably not what you want. I=20 +don't believe there is a kernel option for such a thing. I don't=20 +recall seeing this type of accounting anywhere, but there are likely=20 +some patches. + +Cory 'G' Watson + + +From pgsql-performance-owner@postgresql.org Wed Dec 11 13:44:44 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id F1D2B476287 + for ; + Wed, 11 Dec 2002 13:44:42 -0500 (EST) +Received: from l2.socialecology.com (unknown [4.42.179.131]) + by postgresql.org (Postfix) with ESMTP id 74D23476243 + for ; + Wed, 11 Dec 2002 13:44:42 -0500 (EST) +Received: from 4.42.179.151 (broccoli.socialecology.com [4.42.179.151]) + by l2.socialecology.com (Postfix) with SMTP id 935E62A1D50 + for ; + Wed, 11 Dec 2002 10:44:41 -0800 (PST) +X-Mailer: UserLand Frontier 9.1b1 (Macintosh OS) (mailServer v1.1..142) +Mime-Version: 1.0 +Message-Id: <98429170.1172519017@[4.42.179.151]> +X-authenticated-sender: erics +In-reply-to: <1039631086.17316.194.camel@jester> +Date: Wed, 11 Dec 2002 10:44:39 -0800 +To: Pgsql Performance +From: eric soroos +Subject: Re: Capping CPU usage? +Content-Type: text/plain; charset=us-ascii +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/115 +X-Sequence-Number: 531 + + +> > I can't imagine that postmaster could do this, but I thought it there +> > might be some kind of Linux Kernel CPU quota option I haven't heard +> > of. +> > Can anybody point me in the right direction? + + +I was reading an interview last night (found from /.) on the O(1) scheduler. One thing that was mentioned was batch tasks which get only cpu that's not being used for other things, in blocks of 3 seconds. It has some harder enforcement of nice levels (i.e. batch @ 10 can completely prevent a batch @ 15 from running untill it completes, but is completely interruptable by ordinary processes). Since all the parameters are tweakable, many while running, this may be a place to look. + +eric + + + + +From pgsql-performance-owner@postgresql.org Wed Dec 11 16:49:06 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 812FD47694E + for ; + Wed, 11 Dec 2002 16:49:05 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id D329447694C + for ; + Wed, 11 Dec 2002 16:49:04 -0500 (EST) +Received: from [216.135.165.74] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2277363 for ; + Wed, 11 Dec 2002 13:49:20 -0800 +From: "Josh Berkus" +Subject: Good/Bad RAID and SCSI controllers? +To: pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Wed, 11 Dec 2002 13:49:20 -0800 +Message-ID: +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: 200212/116 +X-Sequence-Number: 532 + +Folks, + +I am hoping to start a thread where users post their experiences with +various RAID and SCSI controllers running Postgres. When completed, +I'll post it somewhere on Techdocs with a big disclaimer. I'll start it +off: + +MYLEX AcceleRAID 170: Not supported under Linux 2.4 kernels. + Performance under RAID 5 with 3 Maxtor UW SCSI disks good on read +operations (slightly better than a single SCSI disk) but on large write +operations poor, similar to low-end IDE disks in having disk-acccess +bottlenecks. Suspected in our installation of locking up on very large +simultaneous read/write operations, such as data tranformations on +tables over 1 million records. (cause of lockup not firmly determined +yet). (Josh Berkus 11/2002) + +-Josh Berkus + +From pgsql-performance-owner@postgresql.org Wed Dec 11 16:53:24 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3F4E8475F5E + for ; + Wed, 11 Dec 2002 16:53:23 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 8DFEC475A9E + for ; + Wed, 11 Dec 2002 16:53:22 -0500 (EST) +Received: from [216.135.165.74] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2277358 for ; + Wed, 11 Dec 2002 13:53:38 -0800 +From: "Josh Berkus" +Subject: Re: Which of the solution is better? +To: pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Wed, 11 Dec 2002 13:53:38 -0800 +Message-ID: +In-Reply-To: +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: 200212/117 +X-Sequence-Number: 533 + +Wei, + +> I have two tables A and B where A is a huge table with thousands of +> rows, B is a small table with only a couple of entries. +> +> I want to do something like +> +> SELECT +> A.ID +> A.Name +> FROM +> A JOIN B ON (A.ID = B.ID) + +You might consider: +SELECT A.ID + A.Name +FROM A +WHERE EXISTS (SELECT ID FROM B WHERE B.ID = A.ID) + +This lets the parser know that you are not interested in retrieving +entire records from B, just those rows from A which correspond to B. + Run that, and compare the EXPLAIN ANALYZE plan against one which lets +the that parser have free reign: + +SELECT A.ID, A.Name +FROM A, B +WHERE A.ID = B.ID + +Chances are, the parser will do a better job on the query than you can +do by making stuff explicit. + +Give it a try. + +-Josh Berkus + +From pgsql-performance-owner@postgresql.org Wed Dec 11 17:06:08 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 737CE475FB7 + for ; + Wed, 11 Dec 2002 17:06:06 -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 C70C9475F5E + for ; + Wed, 11 Dec 2002 17:06:05 -0500 (EST) +Received: from p463-tnt2.mel.ihug.com.au (postgresql.org) [203.173.165.209] + by new-smtp2.ihug.com.au with esmtp (Exim 3.22 #1 (Debian)) + id 18MEzR-0001Gd-00; Thu, 12 Dec 2002 09:06:02 +1100 +Message-ID: <3DF7B6C8.9010008@postgresql.org> +Date: Thu, 12 Dec 2002 09:06:00 +1100 +From: Justin Clift +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020826 +X-Accept-Language: en-au, en-gb, en-us, en +MIME-Version: 1.0 +To: Josh Berkus +Cc: pgsql-performance@postgresql.org +Subject: Re: Good/Bad RAID and SCSI controllers? +References: +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/118 +X-Sequence-Number: 534 + +Josh Berkus wrote: +> Folks, +> +> I am hoping to start a thread where users post their experiences with +> various RAID and SCSI controllers running Postgres. When completed, +> I'll post it somewhere on Techdocs with a big disclaimer. I'll start it +> off: + +Sounds like a really good idea. There's already the beginnings of a page on Techdocs for this too. ;-) + +Here's two thoughts that might be helpful, although they're not RAID. + +Advansys UW SCSI controller: Brain damaged. Won't let standard Seagate Cheetah 10k RPM drives operating at all without +having SCSI Disconnection turned off, and speed is forced to a maximum throughput of 6MB/s. 100% not recommended. + +Adaptec 29160 Ultra160 controller, BIOS version 3.10.0: Seems nice. Everything works well, most stuff is automatically +configured, supported by just about everything. Haven't done throughput benchmarks though. + +Regards and best wishes, + +Justin Clift + + +> MYLEX AcceleRAID 170: Not supported under Linux 2.4 kernels. +> Performance under RAID 5 with 3 Maxtor UW SCSI disks good on read +> operations (slightly better than a single SCSI disk) but on large write +> operations poor, similar to low-end IDE disks in having disk-acccess +> bottlenecks. Suspected in our installation of locking up on very large +> simultaneous read/write operations, such as data tranformations on +> tables over 1 million records. (cause of lockup not firmly determined +> yet). (Josh Berkus 11/2002) +> +> -Josh Berkus + + +-- +"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 Dec 11 17:26:18 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id D99954765F1; Wed, 11 Dec 2002 17:26:15 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP + id D3D6C476442; Wed, 11 Dec 2002 17:26:13 -0500 (EST) +Received: from [216.135.165.74] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2277433; Wed, 11 Dec 2002 14:26:29 -0800 +From: "Josh Berkus" +Subject: Re: Good/Bad RAID and SCSI controllers? +To: Justin Clift +Cc: pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Wed, 11 Dec 2002 14:26:29 -0800 +Message-ID: +In-Reply-To: <3DF7B6C8.9010008@postgresql.org> +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: 200212/119 +X-Sequence-Number: 535 + +Justin, + +> Sounds like a really good idea. There's already the beginnings of a +> page on Techdocs for this too. ;-) + +Where? I don't see it. + +-Josh + + +From pgsql-performance-owner@postgresql.org Wed Dec 11 17:40:01 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id AFAB94762AA; Wed, 11 Dec 2002 17:39:59 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP + id 7559A475FB7; Wed, 11 Dec 2002 17:39:56 -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 gBBMccnd017531; + Wed, 11 Dec 2002 15:38:38 -0700 (MST) +Date: Wed, 11 Dec 2002 15:34:27 -0700 (MST) +From: "scott.marlowe" +To: Justin Clift +Cc: Josh Berkus , + +Subject: Re: Good/Bad RAID and SCSI controllers? +In-Reply-To: <3DF7B6C8.9010008@postgresql.org> +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: 200212/120 +X-Sequence-Number: 536 + +On Thu, 12 Dec 2002, Justin Clift wrote: + +> Josh Berkus wrote: +> > Folks, +> > +> > I am hoping to start a thread where users post their experiences with +> > various RAID and SCSI controllers running Postgres. When completed, +> > I'll post it somewhere on Techdocs with a big disclaimer. I'll start it +> > off: +> +> Sounds like a really good idea. There's already the beginnings of a page on Techdocs for this too. ;-) +> +> Here's two thoughts that might be helpful, although they're not RAID. +> +> Advansys UW SCSI controller: Brain damaged. Won't let standard Seagate Cheetah 10k RPM drives operating at all without +> having SCSI Disconnection turned off, and speed is forced to a maximum throughput of 6MB/s. 100% not recommended. +> +> Adaptec 29160 Ultra160 controller, BIOS version 3.10.0: Seems nice. Everything works well, most stuff is automatically +> configured, supported by just about everything. Haven't done throughput benchmarks though. + +I'll throw a vote in behind the SymBIOS / LSI logic cards. They are quite +stable and reliable, and generally faster than most other cards. I've got +an UW symbios card at home I'll have to truck into work to play with so I +can compare it to my Adaptecs here. + +I picked it up on Ebay (the symbios card) for $30, and it had a network +interface on it too, but the guy didn't know what kind it was. Turned out +to be gig ethernet interface with the yellowfin chipset. not a bad deal, +when you think about it. poor thing gets to run my scanner, a tape drive, +and an old Plextor 12 Plex CDROM drive. I'd like to hook up something +with the gigabit nic someday while it's still considered somewhat fast. +:-) + +For insight into the SCSI cards that Linux supports and what the +maintainers think, I highly recommend a tour of the driver source code +files. It's amazing how often the words "brain damaged" and "piece of +crap" show up there. + + +From pgsql-performance-owner@postgresql.org Wed Dec 11 17:50:41 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 348B34762C7 + for ; + Wed, 11 Dec 2002 17:50:40 -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 92C904762AA + for ; + Wed, 11 Dec 2002 17:50:39 -0500 (EST) +Received: from p463-tnt2.mel.ihug.com.au (postgresql.org) [203.173.165.209] + by new-smtp2.ihug.com.au with esmtp (Exim 3.22 #1 (Debian)) + id 18MFge-0003Vi-00; Thu, 12 Dec 2002 09:50:41 +1100 +Message-ID: <3DF7C13F.1020809@postgresql.org> +Date: Thu, 12 Dec 2002 09:50:39 +1100 +From: Justin Clift +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020826 +X-Accept-Language: en-au, en-gb, en-us, en +MIME-Version: 1.0 +To: Josh Berkus +Cc: pgsql-performance@postgresql.org +Subject: Re: Good/Bad RAID and SCSI controllers? +References: +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/121 +X-Sequence-Number: 537 + +Josh Berkus wrote: +> Justin, +> +> +>>Sounds like a really good idea. There's already the beginnings of a +>>page on Techdocs for this too. ;-) +> +> +> Where? I don't see it. + +Was thinking about this: + +http://techdocs.postgresql.org/guides/DiskTuningGuide + +:-) + +Regards and best wishes, + +Justin Clift + + + +> -Josh +> + + +-- +"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-general-owner@postgresql.org Thu Dec 12 00:41:41 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A3A00475E8C + for ; + Thu, 12 Dec 2002 00:41:40 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id E44EE475AE6 + for ; + Thu, 12 Dec 2002 00:41:39 -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 gBC5fXpd003456; + Thu, 12 Dec 2002 00:41:34 -0500 (EST) +To: Lincoln Yeoh +Cc: pgsql-general@postgresql.org +Subject: Re: Docs: GIST +In-reply-to: <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> +References: <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> +Comments: In-reply-to Lincoln Yeoh + message dated "Thu, 12 Dec 2002 02:07:09 +0800" +Date: Thu, 12 Dec 2002 00:41:33 -0500 +Message-ID: <3455.1039671693@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/603 +X-Sequence-Number: 34518 + +Lincoln Yeoh writes: +> I'm a bit confused. +> In 7.3 is it possible to use GIST without using any of the stuff in +> contrib/? + +No, because there are no GIST opclasses in the standard installation. +They are only in contrib. + +Yes, that's a bit silly. As GIST improves out of the "academic toy" +category into the "production tool" category, I expect we will migrate +GIST opclasses into the standard installation. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Dec 12 00:52:15 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 132FD475DC0 + for ; + Thu, 12 Dec 2002 00:52:14 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 78CAB475AE6 + for ; + Thu, 12 Dec 2002 00:52:13 -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 gBC5qBpd003548; + Thu, 12 Dec 2002 00:52:11 -0500 (EST) +To: Rod Taylor +Cc: Josh Berkus , + Pgsql Performance +Subject: Re: Capping CPU usage? +In-reply-to: <1039631086.17316.194.camel@jester> +References: + <1039631086.17316.194.camel@jester> +Comments: In-reply-to Rod Taylor + message dated "11 Dec 2002 13:24:47 -0500" +Date: Thu, 12 Dec 2002 00:52:10 -0500 +Message-ID: <3547.1039672330@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/122 +X-Sequence-Number: 538 + +Rod Taylor writes: +>> I had a new question from a client: is it possible to "cap" CPU usage +>> for PostgreSQL running on Linux? + +> Anyway, would it be sufficient to simply reduce the priority of the +> process? + +If the issue is to prevent Postgres *as a whole* from hogging CPU usage, +I would think that nice-ing the postmaster at launch would work +beautifully. Requests like "I want Postgres to use no more than 30% +of CPU" make no sense to me: if the CPU is otherwise idle, why should +you insist on reserving 70% of it for the idle loop? + +But what we commonly see is "I want to cap the resource usage of this +particular query", and that is a whole lot harder. You cannot win by +nice-ing one single backend, because of priority-inversion concerns. +(The queries you would like to be high-priority might be blocked waiting +for locks held by low-priority backends.) + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Dec 12 02:12:32 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1A6E6476A00 + for ; + Thu, 12 Dec 2002 02:12:31 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 81C67476941 + for ; + Thu, 12 Dec 2002 02:12:28 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id gBC7CRm12312 + for ; Thu, 12 Dec 2002 12:42:27 +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 gBC7CR012307 + for ; Thu, 12 Dec 2002 12:42:27 +0530 +From: "Shridhar Daithankar" +To: +Date: Thu, 12 Dec 2002 12:43:02 +0530 +MIME-Version: 1.0 +Subject: Re: Good/Bad RAID and SCSI controllers? +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3DF88456.4666.8C76734@localhost> +References: <3DF7B6C8.9010008@postgresql.org> +In-reply-to: +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: 200212/123 +X-Sequence-Number: 539 + +On 11 Dec 2002 at 15:34, scott.marlowe wrote: + +> On Thu, 12 Dec 2002, Justin Clift wrote: +> > Advansys UW SCSI controller: Brain damaged. Won't let standard Seagate Cheetah 10k RPM drives operating at all without +> > having SCSI Disconnection turned off, and speed is forced to a maximum throughput of 6MB/s. 100% not recommended. +> > +> > Adaptec 29160 Ultra160 controller, BIOS version 3.10.0: Seems nice. Everything works well, most stuff is automatically +> > configured, supported by just about everything. Haven't done throughput benchmarks though. +> +> I'll throw a vote in behind the SymBIOS / LSI logic cards. They are quite +> stable and reliable, and generally faster than most other cards. I've got +> an UW symbios card at home I'll have to truck into work to play with so I +> can compare it to my Adaptecs here. +> +> I picked it up on Ebay (the symbios card) for $30, and it had a network +> interface on it too, but the guy didn't know what kind it was. Turned out +> to be gig ethernet interface with the yellowfin chipset. not a bad deal, +> when you think about it. poor thing gets to run my scanner, a tape drive, +> and an old Plextor 12 Plex CDROM drive. I'd like to hook up something +> with the gigabit nic someday while it's still considered somewhat fast. +> :-) + +Right now page on techdocs is pretty thin on such details. I suggest these +authors to put this information(barring humour etc. Just experiences) on that +document. + +Secondly I see my name there as contributor but I do not recall any +contribution. Anyway since I would like to have my name there, I will put some +info there as well. + +Bye + Shridhar + +-- +Rules for driving in New York: (1) Anything done while honking your horn is +legal. (2) You may park anywhere if you turn your four-way flashers on. (3) A +red light means the next six cars may go through the intersection. + + +From pgsql-performance-owner@postgresql.org Thu Dec 12 02:35:32 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A3C1E476138 + for ; + Thu, 12 Dec 2002 02:35:30 -0500 (EST) +Received: from web80307.mail.yahoo.com (web80307.mail.yahoo.com + [66.218.79.23]) + by postgresql.org (Postfix) with SMTP id 0F441475DC0 + for ; + Thu, 12 Dec 2002 02:35:30 -0500 (EST) +Message-ID: <20021212073529.50065.qmail@web80307.mail.yahoo.com> +Received: from [203.87.150.116] by web80307.mail.yahoo.com via HTTP; + Wed, 11 Dec 2002 23:35:29 PST +Date: Wed, 11 Dec 2002 23:35:29 -0800 (PST) +From: Ludwig Lim +Subject: Time to commit a change +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: 200212/124 +X-Sequence-Number: 540 + + +Hi: + + How long does it take to commit a change to change +to the database? + + I'm currently developing a application where +response time should be fast. Today I notice the +following in my application log: + + [12/10/2002 16:49:52] SQL statement created + [12/10/2002 16:49:58] Updating OK. + +The SQL statement is a just a stored procedure that +insert a single row to a table. 6 seconds is quite a +long time to execute an insert statement even if the +table has referential integrity constrants and some +triggers (the database is small, no tables having more +than 100 rows). I tried to recreate the scenario by +doing the following at a psql prompt: + +begin; + +explain analyze +select +f_credit_insert('0810030358689',3,121002,402,1096,1654,62550/100 +,'ADXLXDDN',0); -- call the stored procedure + +rollback; + +The following is the result of the explain analyze: +pilot=# explain analyze +pilot-# select +f_credit_insert('0810030358689',3,121002,402,1096,1654,62550/ +,'ADXLXDDN',0); +NOTICE: QUERY PLAN: + +Result (cost=0.00..0.01 rows=1 width=0) (actual +time=195.95..195.95 rows=1 +s=1) +Total runtime: 195.97 msec + +NOTICE: UPDATING fsphdr from f_ti_fspdetl +NOTICE: Current points = 625 +NOTICE: INSERTING into sc_add_points from +f_ti_fspdetl +NOTICE: date = 20021210 at f_ti_sc_add_points +NOTICE: time = 1654 at f_ti_sc_add_points +NOTICE: transtime = 1654 at f_auto_redeem +NOTICE: transdate = 20021210 at f_auto_redeem +NOTICE: balance = 1250 +NOTICE: points needed to redeem = 5000 +NOTICE: Lack the points to merit an auto-redemption +in f_auto_redeem + + + Since the database is not yet in "full production" +mode. I put NOTOICEs to help me debug. + + I can only think of the following reasons why it +took 5 seconds to execute the sql statements in a C++ +application using libpq while it took 195.67 ms. : + a) NOTICEs are also written to /var/log/messages so +it can take some time. Does size of the +/var/log/messages affect the time to execute stored +procedures having NOTICE statements? + b) Connection time overhead. + c) RAID 5. + + There not much concurrent connection at that time (5 +users at most concurrently connected during that time) + + One of the factor that I can't tell is the time it +takes to commit that particular transaction. Are there +ways to approximate the time to commit the changes +given the time it take execute that particular sql +statement (I'm assuming that there is only 1 SQL +statement in that particular transaction). + + Anybody has a idea why it took that long to commit? +My setup is a Pentium 4 with RAID 5. My version of +postgresql is 7.2.2 + + +Thank you very much, + +ludwig. + +__________________________________________________ +Do you Yahoo!? +New DSL Internet Access from SBC & Yahoo! +http://sbc.yahoo.com + +From pgsql-performance-owner@postgresql.org Thu Dec 12 03:07:06 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3BEB14762B6 + for ; + Thu, 12 Dec 2002 03:07:05 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 44FEB476061 + for ; + Thu, 12 Dec 2002 03:07:03 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id gBC870j16161 + for ; Thu, 12 Dec 2002 13:37:00 +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 gBC870016156 + for ; Thu, 12 Dec 2002 13:37:00 +0530 +From: "Shridhar Daithankar" +To: PostgreSQL Mailing list +Date: Thu, 12 Dec 2002 13:37:34 +0530 +MIME-Version: 1.0 +Subject: Re: Time to commit a change +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3DF8911E.6439.8F9553F@localhost> +In-reply-to: <20021212073529.50065.qmail@web80307.mail.yahoo.com> +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: 200212/125 +X-Sequence-Number: 541 + +On 11 Dec 2002 at 23:35, Ludwig Lim wrote: +> How long does it take to commit a change to change +> to the database? + +Shoudln't be long actually.. + +> [12/10/2002 16:49:52] SQL statement created +> [12/10/2002 16:49:58] Updating OK. +> +> The SQL statement is a just a stored procedure that +> insert a single row to a table. 6 seconds is quite a +> long time to execute an insert statement even if the +> table has referential integrity constrants and some +> triggers (the database is small, no tables having more +> than 100 rows). I tried to recreate the scenario by +> doing the following at a psql prompt: + +I don't believe it would take so long. Last time I benchmarked postgresql on +mandrake 8.2, I was able to insert/update/delete in 210-240ms on average. I was +benhmarking a server application on a lowly P-III-450 with 256MB RAM and IDE +disk. + +I put 30 clients on that and still excecution time was 240ms. But since there +were 20 clients I was getting 240/30=8ms on an average thorughput. + +All the inserts/updates/deletes were in single transaction as well and tables +were small 100-1000 rows. + +> a) NOTICEs are also written to /var/log/messages so +> it can take some time. Does size of the +> /var/log/messages affect the time to execute stored +> procedures having NOTICE statements? +> b) Connection time overhead. +> c) RAID 5. + +I don't think any of these matters. What explain throws out is an estimate and +it might be wrong as well. + +> One of the factor that I can't tell is the time it +> takes to commit that particular transaction. Are there +> ways to approximate the time to commit the changes +> given the time it take execute that particular sql +> statement (I'm assuming that there is only 1 SQL +> statement in that particular transaction). + +Yes. Try something like this in C/C++ + +gettimeofday +begin +transact +gettimeofday +commit +gettimeofday. + +I am certain it will be in range of 200-250ms. Couldn't get it below that on a +network despite of pooled connections.. + +I am not sure second gettimeofday will be of any help but first and third will +definitely give you an idea. + + +> Anybody has a idea why it took that long to commit? +> My setup is a Pentium 4 with RAID 5. My version of +> postgresql is 7.2.2 + +I would put that to 200ms if client and server on same machine. Let us know +what it turns out.. + +HTH + +Bye + Shridhar + +-- +Jim Nasium's Law: In a large locker room with hundreds of lockers, the few +people using the facility at any one time will all have lockers next to each +other so that everybody is cramped. + + +From pgsql-performance-owner@postgresql.org Thu Dec 12 12:15:41 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 816D6476063 + for ; + Thu, 12 Dec 2002 12:15:39 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 68940475EB9 + for ; + Thu, 12 Dec 2002 12:15:38 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id C9220D609; Thu, 12 Dec 2002 09:15:43 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id AAA535C02; Thu, 12 Dec 2002 09:15:43 -0800 (PST) +Date: Thu, 12 Dec 2002 09:15:43 -0800 (PST) +From: Stephan Szabo +To: Ludwig Lim +Cc: PostgreSQL Mailing list +Subject: Re: Time to commit a change +In-Reply-To: <20021212073529.50065.qmail@web80307.mail.yahoo.com> +Message-ID: <20021212091233.H8927-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/126 +X-Sequence-Number: 542 + +On Wed, 11 Dec 2002, Ludwig Lim wrote: + +> +> Hi: +> +> How long does it take to commit a change to change +> to the database? +> +> I'm currently developing a application where +> response time should be fast. Today I notice the +> following in my application log: +> +> [12/10/2002 16:49:52] SQL statement created +> [12/10/2002 16:49:58] Updating OK. +> +> The SQL statement is a just a stored procedure that +> insert a single row to a table. 6 seconds is quite a +> long time to execute an insert statement even if the +> table has referential integrity constrants and some +> triggers (the database is small, no tables having more +> than 100 rows). I tried to recreate the scenario by +> doing the following at a psql prompt: + +Was this run while anything else was hitting the database +or just by itself? I'd wonder if there were any lock +contentions (for example on foreign keys) or anything +like that which might have had some effect. + + +From pgsql-performance-owner@postgresql.org Thu Dec 12 12:44:50 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D5B54475EF0 + for ; + Thu, 12 Dec 2002 12:44:48 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP + id A51CA4760A7; Thu, 12 Dec 2002 12:43:07 -0500 (EST) +Received: by davinci.ethosmedia.com (CommuniGate Pro PIPE 4.0.2) + with PIPE id 2278801; Thu, 12 Dec 2002 09:43:32 -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 2278796; Thu, 12 Dec 2002 09:43:25 -0800 +From: "Josh Berkus" +Subject: Re: Capping CPU usage? +To: Tom Lane , Rod Taylor +Cc: Josh Berkus , + Pgsql Performance +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Thu, 12 Dec 2002 09:43:25 -0800 +Message-ID: +In-Reply-To: <3547.1039672330@sss.pgh.pa.us> +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +Content-Transfer-Encoding: 8bit +X-Spam-Status: No, hits=-4.1 required=6.0 tests=IN_REP_TO, + SUBJ_ENDS_IN_Q_MARK, + AWL version=2.20 +X-Spam-Level: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/127 +X-Sequence-Number: 543 + +Tom, + +> If the issue is to prevent Postgres *as a whole* from hogging CPU +> usage, +> I would think that nice-ing the postmaster at launch would work +> beautifully. Requests like "I want Postgres to use no more than 30% +> of CPU" make no sense to me: if the CPU is otherwise idle, why should +> you insist on reserving 70% of it for the idle loop? + + That's what I asked the person who asked me. Apparently, they +want to do real-time operations without forking out for a real-time OS. + My response was "you can nice the postmaster, and simplify your +queries, but that's about it". + +Thank you, everybody, for confirming this. + +-Josh Berkus + +From pgsql-performance-owner@postgresql.org Thu Dec 12 12:54:38 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8347E476879 + for ; + Thu, 12 Dec 2002 12:54:36 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 3E409476E29 + for ; + Thu, 12 Dec 2002 12:48:44 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2278813; Thu, 12 Dec 2002 09:49:08 -0800 +From: "Josh Berkus" +Subject: Re: Time to commit a change +To: Ludwig Lim , + PostgreSQL Mailing list +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Thu, 12 Dec 2002 09:49:08 -0800 +Message-ID: +In-Reply-To: <20021212073529.50065.qmail@web80307.mail.yahoo.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: 200212/128 +X-Sequence-Number: 544 + +Ludwig, + +> Anybody has a idea why it took that long to commit? +> My setup is a Pentium 4 with RAID 5. My version of +> postgresql is 7.2.2 + +Disk contention is also a very possible issue. I'd suggest trying the +same test when you are certain that no other disk activity is +happening. I've seen appalling wait times for random writes on some +RAID5 controllers. + +Also, how about publishing the text of the function? + +What controller are you using? How many dirves, of what type? + +-Josh Berkus + +From pgsql-performance-owner@postgresql.org Thu Dec 12 13:04:56 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 8B3914767ED + for ; + Thu, 12 Dec 2002 13:04:54 -0500 (EST) +Received: from lakemtao04.cox.net (lakemtao04.cox.net [68.1.17.241]) + by postgresql.org (Postfix) with ESMTP id 367AE4764C5 + for ; + Thu, 12 Dec 2002 12:57:53 -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 <20021212175759.MKAM22825.lakemtao04.cox.net@[192.168.1.1]> + for ; + Thu, 12 Dec 2002 12:57:59 -0500 +Subject: Re: Capping CPU usage? +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: +References: +Content-Type: text/plain +Organization: +Message-Id: <1039715877.1261.101.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 12 Dec 2002 11:57:57 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/129 +X-Sequence-Number: 545 + +On Thu, 2002-12-12 at 11:43, Josh Berkus wrote: +> Tom, +> +> > If the issue is to prevent Postgres *as a whole* from hogging CPU +> > usage, +> > I would think that nice-ing the postmaster at launch would work +> > beautifully. Requests like "I want Postgres to use no more than 30% +> > of CPU" make no sense to me: if the CPU is otherwise idle, why should +> > you insist on reserving 70% of it for the idle loop? +> +> That's what I asked the person who asked me. Apparently, they +> want to do real-time operations without forking out for a real-time OS. +> My response was "you can nice the postmaster, and simplify your +> queries, but that's about it". + +Maybe, even with processes niced down low, the current Linux scheduler +"drop down" a currently schueduled/executing process. + +Maybe that would change with the low-latency patches, or with the +O(1) scheduler in kernel 2.6. + +-- ++---------------------------------------------------------------+ +| 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-general-owner@postgresql.org Thu Dec 12 15:46:11 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 3B8E5476677 + for ; + Thu, 12 Dec 2002 15:46:09 -0500 (EST) +Received: from smtp4.jaring.my (smtp4.jaring.my [61.6.32.54]) + by postgresql.org (Postfix) with ESMTP id 425C1476307 + for ; + Thu, 12 Dec 2002 15:46:07 -0500 (EST) +Received: from pc.localhost. (j198.crc25.jaring.my [61.6.98.212]) + by smtp4.jaring.my (8.11.4/8.11.4) with ESMTP id gBCKjp814151; + Fri, 13 Dec 2002 04:46:00 +0800 (MYT) +Message-Id: <5.1.0.14.1.20021213043655.027360b0@mbox.jaring.my> +X-Sender: lyeoh@mbox.jaring.my +X-Mailer: QUALCOMM Windows Eudora Version 5.1 +Date: Fri, 13 Dec 2002 05:02:28 +0800 +To: Tom Lane +From: Lincoln Yeoh +Subject: Re: Docs: GIST +Cc: pgsql-general@postgresql.org +In-Reply-To: <3455.1039671693@sss.pgh.pa.us> +References: <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> + <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> +Mime-Version: 1.0 +Content-Type: text/plain; charset="us-ascii"; format=flowed +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/656 +X-Sequence-Number: 34571 + +I did figure it out eventually but it'll be clearer to mention that in the +docs - e.g. the only way to use GIST is to use the stuff in contrib. Coz I +had a bit of wishful thinking - thought that maybe some bits of GIST might +have at least become useable by default in 7.3 e.g. the simpler stuff (the +docs didn't quite contradict that). + +Definitely not asking for it to be rushed in tho. Software is more reliable +when the developers know what they are doing, and they get to release stuff +when they think it's ready, not when others say it is. + +Cheerio, +Link. + +At 12:41 AM 12/12/02 -0500, Tom Lane wrote: + +>Lincoln Yeoh writes: +> > I'm a bit confused. +> > In 7.3 is it possible to use GIST without using any of the stuff in +> > contrib/? +> +>No, because there are no GIST opclasses in the standard installation. +>They are only in contrib. + + + +From pgsql-general-owner@postgresql.org Thu Dec 12 16:31:41 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id E6E86476D17; Thu, 12 Dec 2002 16:31:38 -0500 (EST) +Received: from beamish.nsd.ca (unknown [205.150.156.194]) + by postgresql.org (Postfix) with ESMTP + id ECF7B475E24; Thu, 12 Dec 2002 16:31:37 -0500 (EST) +Received: (from smap@localhost) by beamish.nsd.ca (8.9.3/8.9.3) id QAA10221; + Thu, 12 Dec 2002 16:31:38 -0500 +X-Authentication-Warning: beamish.nsd.ca: smap set sender to + using -f +Received: from reddog.nsd.ca(192.168.101.30) by beamish.nsd.ca via smap + (V2.1/2.1+anti-relay+anti-spam) + id xma010219; Thu, 12 Dec 02 16:31:10 -0500 +Received: from nsd.ca (jllachan-linux.nsd.ca [192.168.101.148]) + by reddog.nsd.ca (8.8.7/8.8.7) with ESMTP id QAA05029; + Thu, 12 Dec 2002 16:29:39 -0500 +Message-ID: <3DF90042.E5290B7F@nsd.ca> +Date: Thu, 12 Dec 2002 16:31:46 -0500 +From: Jean-Luc Lachance +X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.9-31 i686) +X-Accept-Language: en +MIME-Version: 1.0 +To: pgsql-general@postgresql.org +Cc: pgsql-performance@postgresql.org +Subject: CLUSTER command +References: <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> + <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> + <5.1.0.14.1.20021213043655.027360b0@mbox.jaring.my> +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/659 +X-Sequence-Number: 34574 + +Hi all, + +I just read about the cluster command and was a little (very) +disapointed. +Clustered tables do not remain clustered after inserts. +Clustered tables are usefull when the table is very large and there are +few different keys. + + +Because the table file is already extended (2G limit) using different +files extension (.N) +how complicated (modifying the code) would it be to have the table files +split according to the cluster key? + +This would: + +Greatly improve performance when the cluster key in included in search +criteria. +Allow for a much larger table before a file has to be split (.N). +Simplify the management of symblinks (that's something else we need to +look at). +The index file for that field would no longer be required. + +Of course, there should be only one cluster key per table. +The length the "key" should be short and the number of unique key should +be low as well. + +SO... ? + +JLL + +From pgsql-general-owner@postgresql.org Thu Dec 12 16:41:14 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 6B3AF476DC6; Thu, 12 Dec 2002 16:41:13 -0500 (EST) +Received: from beamish.nsd.ca (unknown [205.150.156.194]) + by postgresql.org (Postfix) with ESMTP + id 273ED476D57; Thu, 12 Dec 2002 16:40:08 -0500 (EST) +Received: (from smap@localhost) by beamish.nsd.ca (8.9.3/8.9.3) id QAA10276; + Thu, 12 Dec 2002 16:40:09 -0500 +X-Authentication-Warning: beamish.nsd.ca: smap set sender to + using -f +Received: from reddog.nsd.ca(192.168.101.30) by beamish.nsd.ca via smap + (V2.1/2.1+anti-relay+anti-spam) + id xma010272; Thu, 12 Dec 02 16:39:48 -0500 +Received: from nsd.ca (jllachan-linux.nsd.ca [192.168.101.148]) + by reddog.nsd.ca (8.8.7/8.8.7) with ESMTP id QAA05053; + Thu, 12 Dec 2002 16:38:18 -0500 +Message-ID: <3DF90248.9BAF931C@nsd.ca> +Date: Thu, 12 Dec 2002 16:40:24 -0500 +From: Jean-Luc Lachance +X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.9-31 i686) +X-Accept-Language: en +MIME-Version: 1.0 +To: pgsql-general@postgresql.org, pgsql-performance@postgresql.org +Subject: Re: [PERFORM] CLUSTER command +References: <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> + <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> + <5.1.0.14.1.20021213043655.027360b0@mbox.jaring.my> + <3DF90042.E5290B7F@nsd.ca> +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/661 +X-Sequence-Number: 34576 + +Oh, and something else, + +I think the syntax should be: + +Cluster on + + +Maybe inheritance can be use here. +The problem is creating the new "table" when a new key is detected. +I know, I can use rules, but the optimiser is not aware of the +clustering. + +Enough from me for now. + +What do you think? + +JLL + + +Jean-Luc Lachance wrote: +> +> Hi all, +> +> I just read about the cluster command and was a little (very) +> disapointed. +> Clustered tables do not remain clustered after inserts. +> Clustered tables are usefull when the table is very large and there are +> few different keys. +> +> Because the table file is already extended (2G limit) using different +> files extension (.N) +> how complicated (modifying the code) would it be to have the table files +> split according to the cluster key? +> +> This would: +> +> Greatly improve performance when the cluster key in included in search +> criteria. +> Allow for a much larger table before a file has to be split (.N). +> Simplify the management of symblinks (that's something else we need to +> look at). +> The index file for that field would no longer be required. +> +> Of course, there should be only one cluster key per table. +> The length the "key" should be short and the number of unique key should +> be low as well. +> +> SO... ? +> +> JLL +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org + +From pgsql-general-owner@postgresql.org Thu Dec 12 17:08:58 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 1DD20476EB0; Thu, 12 Dec 2002 17:08:55 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP + id E91D7476F50; Thu, 12 Dec 2002 17:03:55 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 5FD05D60A; Thu, 12 Dec 2002 14:03:56 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 4D6F15C02; Thu, 12 Dec 2002 14:03:56 -0800 (PST) +Date: Thu, 12 Dec 2002 14:03:56 -0800 (PST) +From: Stephan Szabo +To: Jean-Luc Lachance +Cc: , + +Subject: Re: CLUSTER command +In-Reply-To: <3DF90042.E5290B7F@nsd.ca> +Message-ID: <20021212135913.Q11714-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/669 +X-Sequence-Number: 34584 + + +On Thu, 12 Dec 2002, Jean-Luc Lachance wrote: + +> Hi all, +> +> I just read about the cluster command and was a little (very) +> disapointed. +> Clustered tables do not remain clustered after inserts. +> Clustered tables are usefull when the table is very large and there are +> few different keys. +> +> +> Because the table file is already extended (2G limit) using different +> files extension (.N) +> how complicated (modifying the code) would it be to have the table files +> split according to the cluster key? + +I'd vote against changing the existing CLUSTER since the existing CLUSTER +while not great does handle many different key values fairly well as well +and this solution wouldn't. Many different key values are still +useful to cluster if you're doing searches over ranges since it lowers the +number of heap file reads necessary. If done this should probably be +separate from the existing cluster or at least both versions should be +possible. + + + +From pgsql-general-owner@postgresql.org Thu Dec 12 17:20:35 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 160FC476E79; Thu, 12 Dec 2002 17:20:35 -0500 (EST) +Received: from beamish.nsd.ca (unknown [205.150.156.194]) + by postgresql.org (Postfix) with ESMTP + id EF728476F48; Thu, 12 Dec 2002 17:15:14 -0500 (EST) +Received: (from smap@localhost) by beamish.nsd.ca (8.9.3/8.9.3) id RAA10695; + Thu, 12 Dec 2002 17:15:09 -0500 +X-Authentication-Warning: beamish.nsd.ca: smap set sender to + using -f +Received: from reddog.nsd.ca(192.168.101.30) by beamish.nsd.ca via smap + (V2.1/2.1+anti-relay+anti-spam) + id xma010693; Thu, 12 Dec 02 17:15:01 -0500 +Received: from nsd.ca (jllachan-linux.nsd.ca [192.168.101.148]) + by reddog.nsd.ca (8.8.7/8.8.7) with ESMTP id RAA05215; + Thu, 12 Dec 2002 17:13:30 -0500 +Message-ID: <3DF90A89.61040846@nsd.ca> +Date: Thu, 12 Dec 2002 17:15:37 -0500 +From: Jean-Luc Lachance +X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.9-31 i686) +X-Accept-Language: en +MIME-Version: 1.0 +To: Stephan Szabo +Cc: pgsql-general@postgresql.org, pgsql-performance@postgresql.org +Subject: Re: CLUSTER command +References: <20021212135913.Q11714-100000@megazone23.bigpanda.com> +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/671 +X-Sequence-Number: 34586 + +The current cluster command is equivalant to: + +create b as select * from a order by i; + +So you would not be loosing anything. + + + +Stephan Szabo wrote: +> +> On Thu, 12 Dec 2002, Jean-Luc Lachance wrote: +> +> > Hi all, +> > +> > I just read about the cluster command and was a little (very) +> > disapointed. +> > Clustered tables do not remain clustered after inserts. +> > Clustered tables are usefull when the table is very large and there are +> > few different keys. +> > +> > +> > Because the table file is already extended (2G limit) using different +> > files extension (.N) +> > how complicated (modifying the code) would it be to have the table files +> > split according to the cluster key? +> +> I'd vote against changing the existing CLUSTER since the existing CLUSTER +> while not great does handle many different key values fairly well as well +> and this solution wouldn't. Many different key values are still +> useful to cluster if you're doing searches over ranges since it lowers the +> number of heap file reads necessary. If done this should probably be +> separate from the existing cluster or at least both versions should be +> possible. + +From pgsql-performance-owner@postgresql.org Thu Dec 12 17:24:40 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 89FDC476E3E + for ; + Thu, 12 Dec 2002 17:24:39 -0500 (EST) +Received: from phaedrusdeinus.org (dsl092-130-239.chi1.dsl.speakeasy.net + [66.92.130.239]) by postgresql.org (Postfix) with SMTP id 20C01476EF4 + for ; + Thu, 12 Dec 2002 17:22:12 -0500 (EST) +Received: (qmail 8464 invoked by uid 1001); 12 Dec 2002 22:26:41 -0000 +Date: Thu, 12 Dec 2002 16:26:41 -0600 +From: johnnnnnn +To: Stephan Szabo +Cc: pgsql-performance@postgresql.org, pgsql-general@postgresql.org +Subject: Re: [GENERAL] CLUSTER command +Message-ID: <20021212222641.GA8278@performics.com> +References: <3DF90042.E5290B7F@nsd.ca> + <20021212135913.Q11714-100000@megazone23.bigpanda.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <20021212135913.Q11714-100000@megazone23.bigpanda.com> +User-Agent: Mutt/1.5.1i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/134 +X-Sequence-Number: 550 + +On Thu, Dec 12, 2002 at 02:03:56PM -0800, Stephan Szabo wrote: +> I'd vote against changing the existing CLUSTER since the existing +> CLUSTER while not great does handle many different key values fairly +> well as well and this solution wouldn't. + +I would agree. What's being proposed sounds much more like table +partitioning than clustering. + +That's not to say that the existing CLUSTER couldn't be improved, at +the very least to the point where it allows inserts to respect the +clustered structure. That's a post for another thread, though. + +-johnnnnnnnnnnn + +From pgsql-general-owner@postgresql.org Thu Dec 12 17:27:28 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 6388C476F14; Thu, 12 Dec 2002 17:27:27 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP + id 9A1254758F1; Thu, 12 Dec 2002 17:27:00 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 505EAD618; Thu, 12 Dec 2002 14:27:02 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 4610D5C02; Thu, 12 Dec 2002 14:27:02 -0800 (PST) +Date: Thu, 12 Dec 2002 14:27:02 -0800 (PST) +From: Stephan Szabo +To: Jean-Luc Lachance +Cc: , + +Subject: Re: CLUSTER command +In-Reply-To: <3DF90A89.61040846@nsd.ca> +Message-ID: <20021212142547.J12742-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/672 +X-Sequence-Number: 34587 + +On Thu, 12 Dec 2002, Jean-Luc Lachance wrote: + +> The current cluster command is equivalant to: +> +> create b as select * from a order by i; +> +> So you would not be loosing anything. + +Except for the fact that the CLUSTER is intended (although +I don't know if it does yet) to retain things like constraints +and other indexes which the above doesn't. + + +From pgsql-general-owner@postgresql.org Thu Dec 12 17:39:31 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 6C2DA476E9F; Thu, 12 Dec 2002 17:39:30 -0500 (EST) +Received: from beamish.nsd.ca (unknown [205.150.156.194]) + by postgresql.org (Postfix) with ESMTP + id 79895476E9C; Thu, 12 Dec 2002 17:39:28 -0500 (EST) +Received: (from smap@localhost) by beamish.nsd.ca (8.9.3/8.9.3) id RAA11018; + Thu, 12 Dec 2002 17:39:10 -0500 +X-Authentication-Warning: beamish.nsd.ca: smap set sender to + using -f +Received: from reddog.nsd.ca(192.168.101.30) by beamish.nsd.ca via smap + (V2.1/2.1+anti-relay+anti-spam) + id xma011016; Thu, 12 Dec 02 17:39:07 -0500 +Received: from nsd.ca (jllachan-linux.nsd.ca [192.168.101.148]) + by reddog.nsd.ca (8.8.7/8.8.7) with ESMTP id RAA05326; + Thu, 12 Dec 2002 17:37:37 -0500 +Message-ID: <3DF91030.A372DF7C@nsd.ca> +Date: Thu, 12 Dec 2002 17:39:44 -0500 +From: Jean-Luc Lachance +X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.9-31 i686) +X-Accept-Language: en +MIME-Version: 1.0 +To: johnnnnnn +Cc: Stephan Szabo , + pgsql-performance@postgresql.org, pgsql-general@postgresql.org +Subject: Re: [PERFORM] CLUSTER command +References: <3DF90042.E5290B7F@nsd.ca> + <20021212135913.Q11714-100000@megazone23.bigpanda.com> + <20021212222641.GA8278@performics.com> +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/674 +X-Sequence-Number: 34589 + +OK fine, + +Let's create a new command: + +PARTITION
ON + +I did not want to start a fight. You can keep the CLUSTER command as it +is. + +I still think clustering/partitioning would be a great idea. +This is what I want to talk about. Look at the original post for the +reasons. + + +JLL + + + +johnnnnnn wrote: +> +> On Thu, Dec 12, 2002 at 02:03:56PM -0800, Stephan Szabo wrote: +> > I'd vote against changing the existing CLUSTER since the existing +> > CLUSTER while not great does handle many different key values fairly +> > well as well and this solution wouldn't. +> +> I would agree. What's being proposed sounds much more like table +> partitioning than clustering. +> +> That's not to say that the existing CLUSTER couldn't be improved, at +> the very least to the point where it allows inserts to respect the +> clustered structure. That's a post for another thread, though. +> +> -johnnnnnnnnnnn +> +> ---------------------------(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 Thu Dec 12 17:33:10 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 6D938476E65; Thu, 12 Dec 2002 17:33:09 -0500 (EST) +Received: from smtp9.jaring.my (smtp9.jaring.my [61.6.32.59]) + by postgresql.org (Postfix) with ESMTP + id B27F4476D17; Thu, 12 Dec 2002 17:33:06 -0500 (EST) +Received: from pc.localhost. (j230.crc30.jaring.my [61.6.109.244]) + by smtp9.jaring.my (8.12.6/8.12.6) with ESMTP id gBCMX0M1087923; + Fri, 13 Dec 2002 06:33:01 +0800 (MYT) + (envelope-from lyeoh@pop.jaring.my) +Message-Id: <5.1.0.14.1.20021213063727.0278b270@mbox.jaring.my> +X-Sender: lyeoh@mbox.jaring.my +X-Mailer: QUALCOMM Windows Eudora Version 5.1 +Date: Fri, 13 Dec 2002 06:49:12 +0800 +To: Jean-Luc Lachance , pgsql-general@postgresql.org +From: Lincoln Yeoh +Subject: Re: CLUSTER command +Cc: pgsql-performance@postgresql.org +In-Reply-To: <3DF90042.E5290B7F@nsd.ca> +References: <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> + <5.1.0.14.1.20021212010621.0273d040@mbox.jaring.my> + <5.1.0.14.1.20021213043655.027360b0@mbox.jaring.my> +Mime-Version: 1.0 +Content-Type: text/plain; charset="us-ascii"; format=flowed +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/673 +X-Sequence-Number: 34588 + +Splitting table files by indexed value may not help if the operating system +doesn't manage to keep the tables unfragmented on disk. I suppose the O/S +should know how to do it though. + +Cheerio, +Link. + +At 04:31 PM 12/12/02 -0500, Jean-Luc Lachance wrote: + +>Hi all, +> +>I just read about the cluster command and was a little (very) +>disapointed. +>Clustered tables do not remain clustered after inserts. +>Clustered tables are usefull when the table is very large and there are +>few different keys. +> +> +>Because the table file is already extended (2G limit) using different +>files extension (.N) +>how complicated (modifying the code) would it be to have the table files +>split according to the cluster key? + + + +From pgsql-general-owner@postgresql.org Thu Dec 12 17:52:33 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 558A5476E3E + for ; + Thu, 12 Dec 2002 17:52:32 -0500 (EST) +Received: from smtpout.mac.com (smtpout.mac.com [17.250.248.85]) + by postgresql.org (Postfix) with ESMTP id 38996476F73 + for ; + Thu, 12 Dec 2002 17:51:45 -0500 (EST) +Received: from asmtp02.mac.com (asmtp02-qfe3 [10.13.10.66]) + by smtpout.mac.com (Xserve/MantshX 2.0) with ESMTP id gBCMplZT018066 + for ; + Thu, 12 Dec 2002 14:51:47 -0800 (PST) +Received: from mac.com ([165.121.130.207]) by asmtp02.mac.com + (Netscape Messaging Server 4.15) with ESMTP id H713I900.S49 for + ; Thu, 12 Dec 2002 14:51:45 -0800 +Date: Thu, 12 Dec 2002 17:50:55 -0500 +Subject: PerformPortalClose warning in 7.3 +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v548) +From: Michael Engelhart +To: pgsql-general@postgresql.org +Content-Transfer-Encoding: 7bit +In-Reply-To: <3DF91030.A372DF7C@nsd.ca> +Message-Id: <2C6CDB6A-0E24-11D7-8E88-000393A48A3C@mac.com> +X-Mailer: Apple Mail (2.548) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/677 +X-Sequence-Number: 34592 + +Hi - +I've been running PostgreSQL 7.3 on Mac OS X 10.2 since it was released +and it's been running fine. I'm using pyPgSQL 2.3 for client side +programming which also was working great until tonight. Now whenever +I do any query of any type, I get warnings like this: + +WARNING: PerformPortalClose: portal "pgsql_00179f10" not found + +It "appears" that everything is still working the way it was but it's a +bit discomforting to have these show up on my screen while running my +applications. + +Anyone that can explain this? + +Here's a tiny bit of Python sample code that I used to make sure it +wasn't my other code causing the problems + +from pyPgSQL import PgSQL + +dbname = "template1" +conn = PgSQL.connect(database=dbname) +cursor = conn.cursor() +sql = "SELECT now()"; +cursor.execute(sql) +res = cursor.fetchall() +for i in res: + print i +cursor.close() +conn.commit() + +strangely if I remove the last 2 lines (cursor.close() and +conn.commit()) I don't get the errors. + +Also I don't notice that I don't have this problem with psql command +line either. Is this the Python API causing this? + +Thanks for any help + +Mike + + +From pgsql-performance-owner@postgresql.org Thu Dec 12 17:55:54 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CFBCD476F33 + for ; + Thu, 12 Dec 2002 17:55:52 -0500 (EST) +Received: from phaedrusdeinus.org (dsl092-130-239.chi1.dsl.speakeasy.net + [66.92.130.239]) by postgresql.org (Postfix) with SMTP id 9F3DB476F43 + for ; + Thu, 12 Dec 2002 17:55:31 -0500 (EST) +Received: (qmail 8571 invoked by uid 1001); 12 Dec 2002 23:00:02 -0000 +Date: Thu, 12 Dec 2002 17:00:02 -0600 +From: johnnnnnn +To: pgsql-performance@postgresql.org, pgsql-general@postgresql.org +Subject: Re: [GENERAL] CLUSTER command +Message-ID: <20021212230002.GC8278@performics.com> +References: <3DF90042.E5290B7F@nsd.ca> + <20021212135913.Q11714-100000@megazone23.bigpanda.com> + <20021212222641.GA8278@performics.com> <3DF91030.A372DF7C@nsd.ca> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <3DF91030.A372DF7C@nsd.ca> +User-Agent: Mutt/1.5.1i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/138 +X-Sequence-Number: 554 + +On Thu, Dec 12, 2002 at 05:39:44PM -0500, Jean-Luc Lachance wrote: +> Let's create a new command: +> +> PARTITION
ON + +> Because the table file is already extended (2G limit) using +> different files extension (.N) +> how complicated (modifying the code) would it be to have the table +> files split according to the cluster key? + +I think the code changes would be complicated. Just at a 30-second +consideration, this would need to touch: +- all sql (selects, inserts, updates, deletes) +- vacuuming +- indexing +- statistics gathering +- existing clustering + +That's not to say it's not worthwhile to look into, but it's big. + +All of that aside, a view over unions is possible now: + +create table u1 (...); +create table u2 (...); +create table u3 (...); + +create view uv as (select "A" as partition_key, ... from u1 + union all + select "B" as partition_key, ... from u2 + union all + select "C" as partition_key, ... from u3); + +That keeps the tables in different files on-disk while still allowing +you to query against all of them. You need to index them separately +and logic is necessary when changing data. + +Hope that helps. + +-johnnnnnnnnnn + +From pgsql-general-owner@postgresql.org Thu Dec 12 19:03:46 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 3F46D475ED1; Thu, 12 Dec 2002 19:03:45 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP + id ADCA2475C8B; Thu, 12 Dec 2002 19:03:44 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 2F9A1D600; Thu, 12 Dec 2002 16:03:47 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 254E45C02; Thu, 12 Dec 2002 16:03:47 -0800 (PST) +Date: Thu, 12 Dec 2002 16:03:47 -0800 (PST) +From: Stephan Szabo +To: johnnnnnn +Cc: , + +Subject: Re: [PERFORM] CLUSTER command +In-Reply-To: <20021212230002.GC8278@performics.com> +Message-ID: <20021212154146.T13718-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/681 +X-Sequence-Number: 34596 + +On Thu, 12 Dec 2002, johnnnnnn wrote: + +> On Thu, Dec 12, 2002 at 05:39:44PM -0500, Jean-Luc Lachance wrote: +> > Let's create a new command: +> > +> > PARTITION
ON +> +> > Because the table file is already extended (2G limit) using +> > different files extension (.N) +> > how complicated (modifying the code) would it be to have the table +> > files split according to the cluster key? +> + +> I think the code changes would be complicated. Just at a 30-second +> consideration, this would need to touch: +> - all sql (selects, inserts, updates, deletes) +> - vacuuming +> - indexing +> - statistics gathering +> - existing clustering + +I think his idea was to treat it similarly to the way that the +system treats tables >2G with .N files. The only thing is that +I believe the code that deals with that wouldn't be particularly +easy to change to do it though, but I've only taken a cursory look at +what I think is the place that does that(storage/smgr/md.c). Some sort of +good partitioning system would be nice though. + + +> create table u1 (...); +> create table u2 (...); +> create table u3 (...); +> +> create view uv as (select "A" as partition_key, ... from u1 +> union all +> select "B" as partition_key, ... from u2 +> union all +> select "C" as partition_key, ... from u3); +> +> That keeps the tables in different files on-disk while still allowing +> you to query against all of them. You need to index them separately +> and logic is necessary when changing data. + +Unfortunately, I think that the optimizer isn't going to do what you'd +hope here and scan only the appropriate table if you were to say +partition_key='A' and foo='bar'. I'd love to be shown that I'm wrong, but +the best I could see hoping for would be that if partition_key was part of +u1-u3 and there was an index on partition_key,foo that it could use that +and do minimal work on the other tables. + +In addition, doing something like the above is a nightmare if you don't +know beforehand what the partitions should be (for example if you know +there aren't alot of distinct values, but you don't know what they are) or +for that matter even with 10-15 partitions, writing the rules and such +would probably be really error prone. + + +From pgsql-general-owner@postgresql.org Thu Dec 12 19:47:24 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id D1B87475DB3; Thu, 12 Dec 2002 19:47:22 -0500 (EST) +Received: from alvh.no-ip.org (CM-lcon6-148-43.cm.vtr.net [200.83.148.43]) + by postgresql.org (Postfix) with ESMTP + id 24081475C8B; Thu, 12 Dec 2002 19:47:22 -0500 (EST) +Received: by alvh.no-ip.org (Postfix, from userid 500) + id 4D37A80241; Thu, 12 Dec 2002 21:47:19 -0300 (CLST) +Date: Thu, 12 Dec 2002 21:47:19 -0300 +From: Alvaro Herrera +To: Stephan Szabo +Cc: johnnnnnn , + pgsql-performance@postgresql.org, pgsql-general@postgresql.org +Subject: Re: [PERFORM] CLUSTER command +Message-ID: <20021213004719.GA19217@dcc.uchile.cl> +References: <20021212230002.GC8278@performics.com> + <20021212154146.T13718-100000@megazone23.bigpanda.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Disposition: inline +Content-Transfer-Encoding: 8bit +In-Reply-To: <20021212154146.T13718-100000@megazone23.bigpanda.com> +User-Agent: Mutt/1.4i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/682 +X-Sequence-Number: 34597 + +On Thu, Dec 12, 2002 at 04:03:47PM -0800, Stephan Szabo wrote: +> On Thu, 12 Dec 2002, johnnnnnn wrote: +> +> > I think the code changes would be complicated. Just at a 30-second +> > consideration, this would need to touch: +> > - all sql (selects, inserts, updates, deletes) +> > - vacuuming +> > - indexing +> > - statistics gathering +> > - existing clustering +> +> I think his idea was to treat it similarly to the way that the +> system treats tables >2G with .N files. The only thing is that +> I believe the code that deals with that wouldn't be particularly +> easy to change to do it though, but I've only taken a cursory look at +> what I think is the place that does that(storage/smgr/md.c). Some sort of +> good partitioning system would be nice though. + +I don't think this is doable without a huge amount of work. The storage +manager doesn't know anything about what is in a page, let alone a +tuple. And it shouldn't, IMHO. Upper levels don't know how are pages +organized in disk; they don't know about .1 segments and so on, and they +shouldn't. + +I think this kind of partition doesn't buy too much. I would really +like to have some kind of auto-clustering, but it should be implemented +in some upper level; e.g., by leaving some empty space in pages for +future tuples, and arranging the whole heap again when it runs out of +free space somewhere. Note that this is very far from the storage +manager. + +-- +Alvaro Herrera () +"La realidad se compone de muchos sue�os, todos ellos diferentes, +pero en cierto aspecto, parecidos..." (Yo, hablando de sue�os er�ticos) + +From pgsql-general-owner@postgresql.org Thu Dec 12 20:06:40 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id DBE77475ED1; Thu, 12 Dec 2002 20:06:38 -0500 (EST) +Received: from clearmetrix.com (unknown [209.92.142.67]) + by postgresql.org (Postfix) with ESMTP + id 1961C475DB3; Thu, 12 Dec 2002 20:06:38 -0500 (EST) +Received: from clearmetrix.com (chw.muvpn.clearmetrix.com [172.16.1.3]) + by clearmetrix.com (8.11.6/linuxconf) with ESMTP id gBD16cx24508; + Thu, 12 Dec 2002 20:06:38 -0500 +Message-ID: <3DF9329B.1020908@clearmetrix.com> +Date: Thu, 12 Dec 2002 20:06:35 -0500 +From: "Charles H. Woloszynski" +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: Alvaro Herrera +Cc: pgsql-performance@postgresql.org, pgsql-general@postgresql.org +Subject: Re: [PERFORM] CLUSTER command +References: <20021212230002.GC8278@performics.com> + <20021212154146.T13718-100000@megazone23.bigpanda.com> + <20021213004719.GA19217@dcc.uchile.cl> +Content-Type: text/plain; charset=ISO-8859-1; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/683 +X-Sequence-Number: 34598 + +I think Oracle does something like this with its clustering. You set a +%fill and Oracle uses this when doing inserts into a segment and when to +add a new one. There is also some control over the grouping of data +within a page. I don't have an Oracle manual present, but I think the +clustering works on a specific index. + +I agree that adding auto-clustering would be a very good thing and that +we can learn about functionality by studying what other applications +have already done and if/how those strategies were successful. + +Charlie + + +Alvaro Herrera wrote: + +>On Thu, Dec 12, 2002 at 04:03:47PM -0800, Stephan Szabo wrote: +> +> +>>On Thu, 12 Dec 2002, johnnnnnn wrote: +>> +>> +>> +>>>I think the code changes would be complicated. Just at a 30-second +>>>consideration, this would need to touch: +>>>- all sql (selects, inserts, updates, deletes) +>>>- vacuuming +>>>- indexing +>>>- statistics gathering +>>>- existing clustering +>>> +>>> +>>I think his idea was to treat it similarly to the way that the +>>system treats tables >2G with .N files. The only thing is that +>>I believe the code that deals with that wouldn't be particularly +>>easy to change to do it though, but I've only taken a cursory look at +>>what I think is the place that does that(storage/smgr/md.c). Some sort of +>>good partitioning system would be nice though. +>> +>> +> +>I don't think this is doable without a huge amount of work. The storage +>manager doesn't know anything about what is in a page, let alone a +>tuple. And it shouldn't, IMHO. Upper levels don't know how are pages +>organized in disk; they don't know about .1 segments and so on, and they +>shouldn't. +> +>I think this kind of partition doesn't buy too much. I would really +>like to have some kind of auto-clustering, but it should be implemented +>in some upper level; e.g., by leaving some empty space in pages for +>future tuples, and arranging the whole heap again when it runs out of +>free space somewhere. Note that this is very far from the storage +>manager. +> +> +> + +-- + + +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-general-owner@postgresql.org Thu Dec 12 21:11:48 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 84829475EA9; Thu, 12 Dec 2002 21:11:47 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP + id 02806475E14; Thu, 12 Dec 2002 21:11:47 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 68C47D618; Thu, 12 Dec 2002 18:11:50 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 5E6935C02; Thu, 12 Dec 2002 18:11:50 -0800 (PST) +Date: Thu, 12 Dec 2002 18:11:50 -0800 (PST) +From: Stephan Szabo +To: Alvaro Herrera +Cc: johnnnnnn , + , +Subject: Re: [PERFORM] CLUSTER command +In-Reply-To: <20021213004719.GA19217@dcc.uchile.cl> +Message-ID: <20021212175208.B15052-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/686 +X-Sequence-Number: 34601 + + +On Thu, 12 Dec 2002, Alvaro Herrera wrote: + +> On Thu, Dec 12, 2002 at 04:03:47PM -0800, Stephan Szabo wrote: +> > On Thu, 12 Dec 2002, johnnnnnn wrote: +> > +> > > I think the code changes would be complicated. Just at a 30-second +> > > consideration, this would need to touch: +> > > - all sql (selects, inserts, updates, deletes) +> > > - vacuuming +> > > - indexing +> > > - statistics gathering +> > > - existing clustering +> > +> > I think his idea was to treat it similarly to the way that the +> > system treats tables >2G with .N files. The only thing is that +> > I believe the code that deals with that wouldn't be particularly +> > easy to change to do it though, but I've only taken a cursory look at +> > what I think is the place that does that(storage/smgr/md.c). Some sort of +> > good partitioning system would be nice though. +> +> I don't think this is doable without a huge amount of work. The storage +> manager doesn't know anything about what is in a page, let alone a +> tuple. And it shouldn't, IMHO. Upper levels don't know how are pages +> organized in disk; they don't know about .1 segments and so on, and they +> shouldn't. + +Which is part of why I said it wouldn't be easy to change to do that, +there's no good way to communicate that information. Like I said, I +didn't look deeply, but I had to look though, because you can never tell +with bits of old university code to do mostly what you want that haven't +been exercised in years floating around. + +> I think this kind of partition doesn't buy too much. I would really +> like to have some kind of auto-clustering, but it should be implemented +> in some upper level; e.g., by leaving some empty space in pages for +> future tuples, and arranging the whole heap again when it runs out of +> free space somewhere. Note that this is very far from the storage +> manager. + +Auto clustering would be nice. + +I think Jean-Luc's suggested partitioning mechanism has certain usage +patterns that it's a win for and most others that it's not. Since the +usage pattern I can think of (very large table with a small number of +breakdowns where your conditions are primarily on those breakdowns) aren't +even remotely in the domain of things I've worked with, I can't say +whether it'd end up really being a win to avoid the index reads for the +table. + + +From pgsql-performance-owner@postgresql.org Thu Dec 12 22:18:04 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 916C6475C8B + for ; + Thu, 12 Dec 2002 22:18:03 -0500 (EST) +Received: from phaedrusdeinus.org (dsl092-130-239.chi1.dsl.speakeasy.net + [66.92.130.239]) by postgresql.org (Postfix) with SMTP id BB589475B85 + for ; + Thu, 12 Dec 2002 22:18:02 -0500 (EST) +Received: (qmail 9028 invoked by uid 1001); 13 Dec 2002 03:22:38 -0000 +Date: Thu, 12 Dec 2002 21:22:38 -0600 +From: johnnnnnn +To: pgsql-performance@postgresql.org +Subject: automated index suggestor -- request for comment +Message-ID: <20021213032238.GC8912@performics.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.5.1i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/143 +X-Sequence-Number: 559 + +The manual is pretty sparse on advice regarding indices. Plenty of +good feature documentation, but not much about when and where an index +is appropriate (except a suggestion that multi-column indices should +be avoided). + +Of course, the ultimate arbiter of which indices are used is the +planner/optimizer. If i could somehow convince the optimizer to +consider indices that don't yet exist, it could tell me which would +give the greatest benefit should i add them. + +So, i'm writing for two reasons. First, i want to gauge interest in +this tool. Is this something that people would find useful? + +Second, i am looking to solicit some advice. Is this project even +feasible? If so, where would be the best place to start? My assumption +has been that i would need to hack into the current code for +determining index paths, and spoof it somehow, but is that possible +without actually creating the indices? + +Any and all feedback welcome. + +-johnnnnnnnnnn + +From pgsql-performance-owner@postgresql.org Fri Dec 13 05:11:48 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 363DE475C8B + for ; + Fri, 13 Dec 2002 05:11:47 -0500 (EST) +Received: from localhost.localdomain (sein.itera.ee [194.126.109.126]) + by postgresql.org (Postfix) with ESMTP id 2D6BD475925 + for ; + Fri, 13 Dec 2002 05:11:46 -0500 (EST) +Received: (from hannu@localhost) + by localhost.localdomain (8.11.6/8.11.6) id gBDC5aG20639; + Fri, 13 Dec 2002 12:05:36 GMT +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: automated index suggestor -- request for comment +From: Hannu Krosing +To: johnnnnnn +Cc: pgsql-performance@postgresql.org +In-Reply-To: <20021213032238.GC8912@performics.com> +References: <20021213032238.GC8912@performics.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039781136.19813.16.camel@huli> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 13 Dec 2002 12:05:36 +0000 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/144 +X-Sequence-Number: 560 + +On Fri, 2002-12-13 at 03:22, johnnnnnn wrote: +> The manual is pretty sparse on advice regarding indices. Plenty of +> good feature documentation, but not much about when and where an index +> is appropriate (except a suggestion that multi-column indices should +> be avoided). +> +> Of course, the ultimate arbiter of which indices are used is the +> planner/optimizer. If i could somehow convince the optimizer to +> consider indices that don't yet exist, it could tell me which would +> give the greatest benefit should i add them. + +the generated index names should be self-explaining or else we would +have to change EXPLAIN output code as well, just to tell what the actual +index definition was. + +That could become the EXPLAIN SPECULATE command ? + +> So, i'm writing for two reasons. First, i want to gauge interest in +> this tool. Is this something that people would find useful? + +Sure it would be helpful. + +> Second, i am looking to solicit some advice. Is this project even +> feasible? + +As tom recently wrote on this list, no statistics is _gathered_ base on +existence of indexes, so pretending that they are there should be +limited just to planner changes plus a way to tell the planner to do it. + +> If so, where would be the best place to start? My assumption +> has been that i would need to hack into the current code for +> determining index paths, and spoof it somehow, but is that possible +> without actually creating the indices? + +Either with or without real indexes, it's all just code ;) + +In worst case you could generate the entries in pg_class table without +building the actual index and then drop or rollback when the explain is +ready. + +Of course you could just determine all possibly useful indexes and +generate then anyhow an then drop them if they were not used ;) + +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Fri Dec 13 08:27:18 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 65276475C8B + for ; + Fri, 13 Dec 2002 08:27:17 -0500 (EST) +Received: from themode.com (themode.com [161.58.169.198]) + by postgresql.org (Postfix) with ESMTP id 892F4475956 + for ; + Fri, 13 Dec 2002 08:27:16 -0500 (EST) +Received: from localhost (mode@localhost) by themode.com (8.11.6) id + gBDDRJG84362; Fri, 13 Dec 2002 08:27:19 -0500 (EST) +Date: Fri, 13 Dec 2002 08:27:19 -0500 (EST) +From: brew@theMode.com +X-X-Sender: mode@themode.com +To: pgsql-performance@postgresql.org +Subject: Capping CPU usage? +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/145 +X-Sequence-Number: 561 + + +Josh..... + +> I had a new question from a client: is it possible to "cap" CPU usage +> for PostgreSQL running on Linux? + +I remember reading a few months ago about a virtual freebsd OS that +divides the memory and cpu up between different users. Although this is +not Linux proper (or improper) it is one way of doing it. I searched for +a few minutes and was unable to find the url, it was something like +virtualFreeBSD.org. + +I've been running on a virtual FreeBSD server for years from iserver, now +verio. Each user has their own apache conf, sendmail, etc. and they claim +to divide up memory and cpu usage. I am not sure if virtualFreeBSD is the +same or different product and whether it would be useful for you, but it's +something to consider. + +brew + + + +From pgsql-performance-owner@postgresql.org Fri Dec 13 09:50:37 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C160D475956 + for ; + Fri, 13 Dec 2002 09:50:33 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 98015476EA2 + for ; + Fri, 13 Dec 2002 09:49:50 -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 gBDEnrpd009275; + Fri, 13 Dec 2002 09:49:53 -0500 (EST) +To: Hannu Krosing +Cc: johnnnnnn , + pgsql-performance@postgresql.org +Subject: Re: automated index suggestor -- request for comment +In-reply-to: <1039781136.19813.16.camel@huli> +References: <20021213032238.GC8912@performics.com> + <1039781136.19813.16.camel@huli> +Comments: In-reply-to Hannu Krosing + message dated "13 Dec 2002 12:05:36 +0000" +Date: Fri, 13 Dec 2002 09:49:53 -0500 +Message-ID: <9274.1039790993@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/146 +X-Sequence-Number: 562 + +Hannu Krosing writes: +> That could become the EXPLAIN SPECULATE command ? + +[ snicker... ] Seriously, it wouldn't be hard to inject a slew of phony +index definitions into the planner to see what it comes up with. You +just have to cons up an IndexOptInfo record, the planner will be none +the wiser. The tricky part is deciding which indexes are even worth +expending planner cycles on. ("Make 'em all" doesn't seem very +practical when you consider multi-column or functional indexes.) + +Also, I don't see any reasonable way to automatically suggest partial +indexes; certainly not on the basis of individual queries. + +The big boys approach this sort of problem with "workload analysis" +tools, which start from a whole collection of sample queries not just +one. I don't think EXPLAIN applied to individual queries can hope to +produce similarly useful results. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 13 10:17:01 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 336E2476E83 + for ; + Fri, 13 Dec 2002 10:17:01 -0500 (EST) +Received: from phaedrusdeinus.org (dsl092-130-239.chi1.dsl.speakeasy.net + [66.92.130.239]) by postgresql.org (Postfix) with SMTP id F0EAF476D6E + for ; + Fri, 13 Dec 2002 10:16:11 -0500 (EST) +Received: (qmail 10508 invoked by uid 1001); 13 Dec 2002 15:20:54 -0000 +Date: Fri, 13 Dec 2002 09:20:54 -0600 +From: johnnnnnn +To: Tom Lane +Cc: pgsql-performance@postgresql.org +Subject: Re: automated index suggestor -- request for comment +Message-ID: <20021213152054.GD8278@performics.com> +References: <20021213032238.GC8912@performics.com> + <1039781136.19813.16.camel@huli> <9274.1039790993@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <9274.1039790993@sss.pgh.pa.us> +User-Agent: Mutt/1.5.1i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/148 +X-Sequence-Number: 564 + +On Fri, Dec 13, 2002 at 09:49:53AM -0500, Tom Lane wrote: +> Hannu Krosing writes: +> > That could become the EXPLAIN SPECULATE command ? +> +> [ snicker... ] Seriously, it wouldn't be hard to inject a slew of +> phony index definitions into the planner to see what it comes up +> with. You just have to cons up an IndexOptInfo record, the planner +> will be none the wiser. + +That's good news. The easier it is, the more likely i am to actually +get it working and available to people. + +> The tricky part is deciding which indexes are even worth expending +> planner cycles on. ("Make 'em all" doesn't seem very practical when +> you consider multi-column or functional indexes.) + +Agreed. But for a first development iteration, "Make 'em all" could +certainly include the combinatorial explosion of all single- and +multi-column indices. It might be slow as a dog, but it would exist. + +> The big boys approach this sort of problem with "workload analysis" +> tools, which start from a whole collection of sample queries not +> just one. I don't think EXPLAIN applied to individual queries can +> hope to produce similarly useful results. + +Again, agreed. My intent was to start with something simple which +could only deal with one query at a time, and then build a more robust +tool from that point. + +That said, i wasn't planning on grafting onto the EXPLAIN syntax, but +rather creating a new SUGGEST command, which could take a query or +eventually a workload file. The other option was to decouple it from +pg proper and have an independent application to live in contrib/ or +gborg. + +-johnnnnnnnnnnn + +From pgsql-performance-owner@postgresql.org Fri Dec 13 10:34:12 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2B659476FE9 + for ; + Fri, 13 Dec 2002 10:34:11 -0500 (EST) +Received: from phaedrusdeinus.org (dsl092-130-239.chi1.dsl.speakeasy.net + [66.92.130.239]) by postgresql.org (Postfix) with SMTP id 13883476E5D + for ; + Fri, 13 Dec 2002 10:32:36 -0500 (EST) +Received: (qmail 10542 invoked by uid 1001); 13 Dec 2002 15:37:19 -0000 +Date: Fri, 13 Dec 2002 09:37:19 -0600 +From: johnnnnnn +To: Hannu Krosing +Cc: pgsql-performance@postgresql.org +Subject: Re: automated index suggestor -- request for comment +Message-ID: <20021213153719.GE8278@performics.com> +References: <20021213032238.GC8912@performics.com> + <1039781136.19813.16.camel@huli> + <20021213095637.4a2b9db4.gry@ll.mit.edu> + <1039798832.19813.28.camel@huli> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <1039798832.19813.28.camel@huli> +User-Agent: Mutt/1.5.1i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/149 +X-Sequence-Number: 565 + +On Fri, Dec 13, 2002 at 05:00:32PM +0000, Hannu Krosing wrote: +> On Fri, 2002-12-13 at 14:56, george young wrote: +> > > Of course you could just determine all possibly useful indexes +> > > and generate then anyhow an then drop them if they were not used +> > > ;) +> > +> > Why not! At least for selects, this seems like the ideal. For +> > insert and update, you have to deal with updating the superfluous +> > indexes -- does the planner include index updating in its work +> > estimates? + +Well, i had a few reasons i didn't want to *actually* create the +indices: + +1- Disk space. If it's evaluating all indices, including multi-column +indices, that ends up being a significant space drain. + +2- Time. Creating indices can take a while for big tables (again, +moreso for multi-column indices). + +3- Usability on running systems. If i can eliminate actual index +creation, it won't tie up disk access on systems that are already +dealing with high load. + +> At least I think we don't optimize the plan for different index +> access patterns for updating indexes. + +I don't think that's the case either, which makes it more difficult to +estimate negative cost of index creation. Not sure how i'll deal with +that except by (for now) ignoring it. + +-johnnnnnnnnnnn + +From pgsql-general-owner@postgresql.org Fri Dec 13 11:42:49 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id A5A3947703A; Fri, 13 Dec 2002 11:42:48 -0500 (EST) +Received: from beamish.nsd.ca (unknown [205.150.156.194]) + by postgresql.org (Postfix) with ESMTP + id F342B476FFB; Fri, 13 Dec 2002 11:42:22 -0500 (EST) +Received: (from smap@localhost) by beamish.nsd.ca (8.9.3/8.9.3) id LAA15816; + Fri, 13 Dec 2002 11:42:08 -0500 +X-Authentication-Warning: beamish.nsd.ca: smap set sender to + using -f +Received: from reddog.nsd.ca(192.168.101.30) by beamish.nsd.ca via smap + (V2.1/2.1+anti-relay+anti-spam) + id xma015812; Fri, 13 Dec 02 11:41:41 -0500 +Received: from nsd.ca (jllachan-linux.nsd.ca [192.168.101.148]) + by reddog.nsd.ca (8.8.7/8.8.7) with ESMTP id LAA08179; + Fri, 13 Dec 2002 11:40:09 -0500 +Message-ID: <3DFA0DF1.DE3B5462@nsd.ca> +Date: Fri, 13 Dec 2002 11:42:25 -0500 +From: Jean-Luc Lachance +X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.9-31 i686) +X-Accept-Language: en +MIME-Version: 1.0 +To: Stephan Szabo +Cc: johnnnnnn , + pgsql-performance@postgresql.org, pgsql-general@postgresql.org +Subject: Re: [PERFORM] CLUSTER command +References: <20021212154146.T13718-100000@megazone23.bigpanda.com> +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/703 +X-Sequence-Number: 34618 + +Stephan, + +Someone commented earlier about the separation/abstraction of the +storage manager. +I agree that it should not be done at the storage level. + +Maybe a better idea, would be to create a new pg_partition table that +would have the functionality of an index on the key field and also be +used to point to a file/table ID. + +That would be alot more work to code on thet planner though. + +If a newly inherited table could also inherite the constraints and +indecies of its parent maybe things would be easier. + +JLL + + +Stephan Szabo wrote: +> +> On Thu, 12 Dec 2002, johnnnnnn wrote: +> +> > On Thu, Dec 12, 2002 at 05:39:44PM -0500, Jean-Luc Lachance wrote: +> > > Let's create a new command: +> > > +> > > PARTITION
ON +> > +> > > Because the table file is already extended (2G limit) using +> > > different files extension (.N) +> > > how complicated (modifying the code) would it be to have the table +> > > files split according to the cluster key? +> > +> +> > I think the code changes would be complicated. Just at a 30-second +> > consideration, this would need to touch: +> > - all sql (selects, inserts, updates, deletes) +> > - vacuuming +> > - indexing +> > - statistics gathering +> > - existing clustering +> +> I think his idea was to treat it similarly to the way that the +> system treats tables >2G with .N files. The only thing is that +> I believe the code that deals with that wouldn't be particularly +> easy to change to do it though, but I've only taken a cursory look at +> what I think is the place that does that(storage/smgr/md.c). Some sort of +> good partitioning system would be nice though. +> +> > create table u1 (...); +> > create table u2 (...); +> > create table u3 (...); +> > +> > create view uv as (select "A" as partition_key, ... from u1 +> > union all +> > select "B" as partition_key, ... from u2 +> > union all +> > select "C" as partition_key, ... from u3); +> > +> > That keeps the tables in different files on-disk while still allowing +> > you to query against all of them. You need to index them separately +> > and logic is necessary when changing data. +> +> Unfortunately, I think that the optimizer isn't going to do what you'd +> hope here and scan only the appropriate table if you were to say +> partition_key='A' and foo='bar'. I'd love to be shown that I'm wrong, but +> the best I could see hoping for would be that if partition_key was part of +> u1-u3 and there was an index on partition_key,foo that it could use that +> and do minimal work on the other tables. +> +> In addition, doing something like the above is a nightmare if you don't +> know beforehand what the partitions should be (for example if you know +> there aren't alot of distinct values, but you don't know what they are) or +> for that matter even with 10-15 partitions, writing the rules and such +> would probably be really error prone. +> +> ---------------------------(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-performance-owner@postgresql.org Fri Dec 13 10:07:18 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4A768476FC2 + for ; + Fri, 13 Dec 2002 10:07:17 -0500 (EST) +Received: from localhost.localdomain (sein.itera.ee [194.126.109.126]) + by postgresql.org (Postfix) with ESMTP id 60282476F23 + for ; + Fri, 13 Dec 2002 10:06:42 -0500 (EST) +Received: (from hannu@localhost) + by localhost.localdomain (8.11.6/8.11.6) id gBDH0Xi21297; + Fri, 13 Dec 2002 17:00:33 GMT +X-Authentication-Warning: localhost.localdomain: hannu set sender to + hannu@tm.ee using -f +Subject: Re: automated index suggestor -- request for comment +From: Hannu Krosing +To: gry@ll.mit.edu +Cc: "pgsql-performance@postgresql.org" +In-Reply-To: <20021213095637.4a2b9db4.gry@ll.mit.edu> +References: <20021213032238.GC8912@performics.com> + <1039781136.19813.16.camel@huli> + <20021213095637.4a2b9db4.gry@ll.mit.edu> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039798832.19813.28.camel@huli> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 13 Dec 2002 17:00:32 +0000 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/147 +X-Sequence-Number: 563 + +I cc'b back to list, hope this is ok? + +On Fri, 2002-12-13 at 14:56, george young wrote: +> On 13 Dec 2002 12:05:36 +0000 +> Hannu Krosing wrote: +> +> > On Fri, 2002-12-13 at 03:22, johnnnnnn wrote: +> > +> > In worst case you could generate the entries in pg_class table without +> > building the actual index and then drop or rollback when the explain is +> > ready. +> > +> --> Of course you could just determine all possibly useful indexes and <-- +> --> generate then anyhow an then drop them if they were not used ;) <-- +> +> Why not! At least for selects, this seems like the ideal. For insert +> and update, you have to deal with updating the superfluous indexes -- +> does the planner include index updating in its work estimates? + +Probably not - the work should be almost the same (modulo cached status +of index pages) for any plan. + +At least I think we don't optimize the plan for different index access +patterns for updating indexes. + +> > For queries +> that use functions in the where clause, you'd have to parse enough to know +> to include indexes on the functions (I know-- the last time I said "all I +> have to do is parse ..." I was really sorry later...). +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Fri Dec 13 13:19:08 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D5547476FB2 + for ; + Fri, 13 Dec 2002 13:19:06 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 723C347708D + for ; + Fri, 13 Dec 2002 13:18:15 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2280254; Fri, 13 Dec 2002 10:18:40 -0800 +From: "Josh Berkus" +Subject: Re: Capping CPU usage? +To: brew@theMode.com, pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Fri, 13 Dec 2002 10:18:40 -0800 +Message-ID: +In-Reply-To: +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: 200212/151 +X-Sequence-Number: 567 + +Brew, + +> I've been running on a virtual FreeBSD server for years from iserver, +> now +> verio. Each user has their own apache conf, sendmail, etc. and they +> claim +> to divide up memory and cpu usage. I am not sure if virtualFreeBSD +> is the +> same or different product and whether it would be useful for you, but +> it's +> something to consider. + +Interesting idea. Sadly for this client, they are trying to cap CPU +usage because they are short on system resources, so virtualization is +not an option. + +However, it would be a possiblilty to keep in mind for other projects. + +-Josh + + + +From pgsql-performance-owner@postgresql.org Fri Dec 13 14:53:04 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5F2464770B3 + for ; + Fri, 13 Dec 2002 14:53:02 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id CBFAC477122 + for ; + Fri, 13 Dec 2002 14:52:04 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2280431 for pgsql-performance@postgresql.org; + Fri, 13 Dec 2002 11:52:31 -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: Odd Sort/Limit/Max Problem +Date: Fri, 13 Dec 2002 11:55:51 -0800 +X-Mailer: KMail [version 1.4] +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212131155.51985.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/152 +X-Sequence-Number: 568 + +Folks,=20 + +Consider this performance quandry brought to me by Elein, which I can replc= +ate=20 +in 7.2.3 and in 7.4 devel: + +case_clients is a medium-large table with about 110,000 rows. The field=20 +date_resolved is a timestamp field which is indexed and allows nulls (in=20 +fact, is null for 40% of entries). + +First, as expected, a regular aggregate is slow: + +jwnet=3D> explain analyze select max(date_resolved) from case_clients; +NOTICE: QUERY PLAN: + +Aggregate (cost=3D3076.10..3076.10 rows=3D1 width=3D4) (actual time=3D484.= +24..484.24=20 +rows=3D1 loops=3D1) + -> Seq Scan on case_clients (cost=3D0.00..2804.48 rows=3D108648 width= +=3D4)=20 +(actual time=3D0.08..379.81 rows=3D108648 loops=3D1) +Total runtime: 484.44 msec + + +So we use the workaround standard for PostgreSQL: + +jwnet=3D> explain analyze select date_resolved from case_clients order by= +=20 +date_resolved desc limit 1; +NOTICE: QUERY PLAN: + +Limit (cost=3D0.00..1.50 rows=3D1 width=3D4) (actual time=3D0.22..0.23 row= +s=3D1=20 +loops=3D1) + -> Index Scan Backward using idx_caseclients_resolved on case_clients=20= +=20 +(cost=3D0.00..163420.59 rows=3D108648 width=3D4) (actual time=3D0.21..0.22 = +rows=3D2=20 +loops=3D1) +Total runtime: 0.33 msec + +... which is fast, but returns NULL, since nulls sort to the bottom! So we= +=20 +add IS NOT NULL: + +jwnet=3D> explain analyze select date_resolved from case_clients where=20 +date_resolved is not null order by date_resolved desc limit 1; +NOTICE: QUERY PLAN: + +Limit (cost=3D0.00..4.06 rows=3D1 width=3D4) (actual time=3D219.63..219.64= + rows=3D1=20 +loops=3D1) + -> Index Scan Backward using idx_caseclients_resolved on case_clients=20= +=20 +(cost=3D0.00..163420.59 rows=3D40272 width=3D4) (actual time=3D219.62..219.= +62 rows=3D2=20 +loops=3D1) +Total runtime: 219.76 msec + +Aieee! Almost as slow as the aggregate! + +Now, none of those times is huge on this test database, but on a larger=20 +database (> 1million rows) the performance problem is much worse. For some= +=20 +reason, the backward index scan seems to have to transverse all of the NULL= +s=20 +before selecting a value. I find this peculiar, as I was under the=20 +impression that NULLs were not indexed. + +What's going on here? + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Dec 13 15:10:55 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 2CEA44770AA + for ; + Fri, 13 Dec 2002 15:10:55 -0500 (EST) +Received: from megazone.bigpanda.com (megazone.bigpanda.com [63.150.15.178]) + by postgresql.org (Postfix) with ESMTP id 4740A477113 + for ; + Fri, 13 Dec 2002 15:10:23 -0500 (EST) +Received: by megazone.bigpanda.com (Postfix, from userid 1001) + id 25AAAD619; Fri, 13 Dec 2002 12:10:20 -0800 (PST) +Received: from localhost (localhost [127.0.0.1]) + by megazone.bigpanda.com (Postfix) with ESMTP + id 1B5D75C02; Fri, 13 Dec 2002 12:10:20 -0800 (PST) +Date: Fri, 13 Dec 2002 12:10:20 -0800 (PST) +From: Stephan Szabo +To: Josh Berkus +Cc: +Subject: Re: Odd Sort/Limit/Max Problem +In-Reply-To: <200212131155.51985.josh@agliodbs.com> +Message-ID: <20021213120738.D25935-100000@megazone23.bigpanda.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/153 +X-Sequence-Number: 569 + + +On Fri, 13 Dec 2002, Josh Berkus wrote: + +> First, as expected, a regular aggregate is slow: + +> So we use the workaround standard for PostgreSQL: +> +> ... which is fast, but returns NULL, since nulls sort to the bottom! So we +> add IS NOT NULL: +> +> jwnet=> explain analyze select date_resolved from case_clients where +> date_resolved is not null order by date_resolved desc limit 1; +> NOTICE: QUERY PLAN: +> +> Limit (cost=0.00..4.06 rows=1 width=4) (actual time=219.63..219.64 rows=1 +> loops=1) +> -> Index Scan Backward using idx_caseclients_resolved on case_clients +> (cost=0.00..163420.59 rows=40272 width=4) (actual time=219.62..219.62 rows=2 +> loops=1) +> Total runtime: 219.76 msec +> +> Aieee! Almost as slow as the aggregate! + +I'd suggest trying a partial index on date_resolved where date_resolve is +not null. In my simple tests on about 200,000 rows of ints where 50% are +null that sort of index cut the runtime on my machine from 407.66 msec to +0.15 msec. + + + +From pgsql-performance-owner@postgresql.org Fri Dec 13 15:24:26 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 23E0047704E + for ; + Fri, 13 Dec 2002 15:24:25 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 5815F477045 + for ; + Fri, 13 Dec 2002 15:24:24 -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 gBDKONpd023243; + Fri, 13 Dec 2002 15:24:23 -0500 (EST) +To: josh@agliodbs.com +Cc: pgsql-performance@postgresql.org +Subject: Re: Odd Sort/Limit/Max Problem +In-reply-to: <200212131155.51985.josh@agliodbs.com> +References: <200212131155.51985.josh@agliodbs.com> +Comments: In-reply-to Josh Berkus + message dated "Fri, 13 Dec 2002 11:55:51 -0800" +Date: Fri, 13 Dec 2002 15:24:23 -0500 +Message-ID: <23242.1039811063@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/154 +X-Sequence-Number: 570 + +Josh Berkus writes: +> Now, none of those times is huge on this test database, but on a larger +> database (> 1million rows) the performance problem is much worse. For some +> reason, the backward index scan seems to have to transverse all of the NULLs +> before selecting a value. + +Correct. You lose, if there are a lot of nulls. Unfortunately, the +"IS NOT NULL" clause isn't considered an indexable operator and so the +indexscan has no idea that it shouldn't return the null rows. If it +could just traverse past them in the index, this example wouldn't be so +bad, but it goes out and fetches the heap rows before discarding 'em :-( + +> I find this peculiar, as I was under the +> impression that NULLs were not indexed. + +Not correct. btrees index NULLs, as they must do in order to have +correct behavior for multicolumn indexes. + + +I think it would work to instead do something like + +select date_resolved from case_clients +where date_resolved < 'infinity' +order by date_resolved desc +limit 1; + +since then the indexscan will get a qualifier condition that will allow +it to discard the nulls. In fact, I think this will even prevent +having to traverse past the nulls in the index --- the original form +starts the indexscan at the index end, but this should do a btree +descent search to exactly the place you want. Note that the +where-clause has to match the scan direction (> or >= for ASC, < or <= +for DESC) so that it looks like a "start here" condition to btree. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 13 17:22:25 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5B951475EE4 + for ; + Fri, 13 Dec 2002 17:22:25 -0500 (EST) +Received: from rh72.home.ee (adsl1030.estpak.ee [213.168.29.11]) + by postgresql.org (Postfix) with ESMTP id 6A6E5475B47 + for ; + Fri, 13 Dec 2002 17:22:24 -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 gBDMMD2N002427; + Sat, 14 Dec 2002 03:22:13 +0500 +Received: (from hannu@localhost) + by rh72.home.ee (8.12.5/8.12.5/Submit) id gBDMM9A4002425; + Sat, 14 Dec 2002 03:22:09 +0500 +X-Authentication-Warning: rh72.home.ee: hannu set sender to hannu@tm.ee using + -f +Subject: Re: Odd Sort/Limit/Max Problem +From: Hannu Krosing +To: Tom Lane +Cc: josh@agliodbs.com, pgsql-performance@postgresql.org +In-Reply-To: <23242.1039811063@sss.pgh.pa.us> +References: <200212131155.51985.josh@agliodbs.com> + <23242.1039811063@sss.pgh.pa.us> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039818128.2391.7.camel@rh72.home.ee> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 14 Dec 2002 03:22:08 +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/155 +X-Sequence-Number: 571 + +Tom Lane kirjutas L, 14.12.2002 kell 01:24: +> Josh Berkus writes: +> > Now, none of those times is huge on this test database, but on a larger +> > database (> 1million rows) the performance problem is much worse. For some +> > reason, the backward index scan seems to have to transverse all of the NULLs +> > before selecting a value. +> +> Correct. You lose, if there are a lot of nulls. Unfortunately, the +> "IS NOT NULL" clause isn't considered an indexable operator and so the +> indexscan has no idea that it shouldn't return the null rows. If it +> could just traverse past them in the index, this example wouldn't be so +> bad, but it goes out and fetches the heap rows before discarding 'em :-( +> +> > I find this peculiar, as I was under the +> > impression that NULLs were not indexed. +> +> Not correct. btrees index NULLs, as they must do in order to have +> correct behavior for multicolumn indexes. + +I've heard this befoe, but this is something I've never understood - why +do you have to index _single_ null's in order to behave correctly for +multi-column index. + +Is it that postgres thinks that tuple of several nulls is the same as +null ? + +Is it just that nulls need to have an ordering and that this fact has +somehow leaked down to actually being stored in the index ? + +I don't have anything against nulls being indexed - in a table where +nulls have about the same frequency as other values it may actually be +useful (if indexes were used to find IS NULL tuples) + + +-- +Hannu Krosing + +From pgsql-hackers-owner@postgresql.org Fri Dec 13 19:00:45 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP + id 0269C475921; Fri, 13 Dec 2002 19:00:44 -0500 (EST) +Received: from office.nextbus.com (ns.nextbus.com [64.164.28.194]) + by postgresql.org (Postfix) with ESMTP + id 714F84758E1; Fri, 13 Dec 2002 19:00:43 -0500 (EST) +Received: from visor.corp.nextbus.com (visor.corp.nextbus.com [192.168.1.109]) + by office.nextbus.com (Postfix) with ESMTP + id 6A09B4F883; Fri, 13 Dec 2002 16:00:44 -0800 (PST) +Received: from localhost (laurette@localhost) + by visor.corp.nextbus.com (8.11.2/8.8.7) with ESMTP id gBE00jd19867; + Fri, 13 Dec 2002 16:00:45 -0800 +X-Authentication-Warning: visor.corp.nextbus.com: laurette owned process doing + -bs +Date: Fri, 13 Dec 2002 16:00:45 -0800 (PST) +From: Laurette Cisneros +X-X-Sender: laurette@visor.corp.nextbus.com +To: Josh Berkus +Cc: sszabo@megazone23.bigpanda.com, + , +Subject: Re: Fwd: Re: [PERFORM] Odd Sort/Limit/Max Problem +In-Reply-To: <200212131445.37863.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: 200212/759 +X-Sequence-Number: 33214 + +Thank you for a good workaround. + +Even BETTER would be to fix the aggregates so workarounds wouldn't have to +be found. + +Thanks again, + +L. +On Fri, 13 Dec 2002, Josh Berkus wrote: + +> +> +> ---------- Forwarded Message ---------- +> +> Subject: Re: [PERFORM] Odd Sort/Limit/Max Problem +> Date: Fri, 13 Dec 2002 12:10:20 -0800 (PST) +> From: Stephan Szabo +> To: Josh Berkus +> Cc: +> +> On Fri, 13 Dec 2002, Josh Berkus wrote: +> +> > First, as expected, a regular aggregate is slow: +> +> > So we use the workaround standard for PostgreSQL: +> > +> > ... which is fast, but returns NULL, since nulls sort to the bottom! So we +> > add IS NOT NULL: +> > +> > jwnet=> explain analyze select date_resolved from case_clients where +> > date_resolved is not null order by date_resolved desc limit 1; +> > NOTICE: QUERY PLAN: +> > +> > Limit (cost=0.00..4.06 rows=1 width=4) (actual time=219.63..219.64 rows=1 +> > loops=1) +> > -> Index Scan Backward using idx_caseclients_resolved on case_clients +> > (cost=0.00..163420.59 rows=40272 width=4) (actual time=219.62..219.62 rows=2 +> > loops=1) +> > Total runtime: 219.76 msec +> > +> > Aieee! Almost as slow as the aggregate! +> +> I'd suggest trying a partial index on date_resolved where date_resolve is +> not null. In my simple tests on about 200,000 rows of ints where 50% are +> null that sort of index cut the runtime on my machine from 407.66 msec to +> 0.15 msec. +> +> +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org +> +> +> ------------------------------------------------------- +> +> + +-- +Laurette Cisneros +The Database Group +(510) 420-3137 +NextBus Information Systems, Inc. +www.nextbus.com +---------------------------------- +There's more to life than just SQL. + + +From pgsql-performance-owner@postgresql.org Fri Dec 13 19:03:58 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1F0B9475F81 + for ; + Fri, 13 Dec 2002 19:03:58 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id A85514758E1 + for ; + Fri, 13 Dec 2002 19:03:56 -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 gBE03tpd006353; + Fri, 13 Dec 2002 19:03:55 -0500 (EST) +To: Hannu Krosing +Cc: josh@agliodbs.com, pgsql-performance@postgresql.org +Subject: Re: Odd Sort/Limit/Max Problem +In-reply-to: <1039818128.2391.7.camel@rh72.home.ee> +References: <200212131155.51985.josh@agliodbs.com> + <23242.1039811063@sss.pgh.pa.us> + <1039818128.2391.7.camel@rh72.home.ee> +Comments: In-reply-to Hannu Krosing + message dated "14 Dec 2002 03:22:08 +0500" +Date: Fri, 13 Dec 2002 19:03:55 -0500 +Message-ID: <6352.1039824235@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/157 +X-Sequence-Number: 573 + +Hannu Krosing writes: +> Tom Lane kirjutas L, 14.12.2002 kell 01:24: +>> Not correct. btrees index NULLs, as they must do in order to have +>> correct behavior for multicolumn indexes. + +> I've heard this befoe, but this is something I've never understood - why +> do you have to index _single_ null's in order to behave correctly for +> multi-column index. + +Well, you don't absolutely *have to* index individual nulls, but you do +have to support nulls in index entries. + +The example that motivates this is + + create table foo (f1 int, f2 int); + create index fooi on foo(f1,f2); + ... fill table ... + select * from foo where f1 = 42; + +The planner is entitled to implement this as an indexscan using fooi's +first column (and ignoring its lower-order column(s)). Now if fooi does +not index rows in which f2 is null, you lose, because it may omit rows +with f1 = 42 that should have been found by the indexscan. So it *has +to* be able to store index entries like (42, NULL). + +For btree's purposes, the easiest implementation is to say that NULL is +an ordinary index entry with a definable sort position (which we chose +to define as "after all non-NULL values"). There's no particular value +in having a special case for all-NULL index entries, so we don't. + +GiST is not able to handle all-NULL index entries, so it uses the rule +"index all rows in which the first index column is not NULL". This +still meets the planner's constraint because we never do an indexscan +that uses only lower-order index columns. + +hash and rtree don't support NULL index entries, but they don't support +multicolumn indexes either, so the constraint doesn't apply. + +> I don't have anything against nulls being indexed - in a table where +> nulls have about the same frequency as other values it may actually be +> useful (if indexes were used to find IS NULL tuples) + +At least for btree, it would be nice to someday allow IS NULL as an +indexable operator. I haven't thought very hard about how to do that; +shoehorning it into the operator class structure looks like it'd be a +horrid mess, so it'd probably require some creative klugery :-( + +> Is it just that nulls need to have an ordering and that this fact has +> somehow leaked down to actually being stored in the index ? + +No, more the other way around: btree assigns an ordering to NULLs +because it must do so in order to know where to put them in the index. +This is an artifact of btree that happens to "leak upward" ... + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 13 21:15:59 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 46DC3475EE4 + for ; + Fri, 13 Dec 2002 21:15:58 -0500 (EST) +Received: from o2.hostbaby.com (o2.hostbaby.com [208.187.29.121]) + by postgresql.org (Postfix) with SMTP id 7A3F2475E82 + for ; + Fri, 13 Dec 2002 21:15:57 -0500 (EST) +Received: (qmail 23241 invoked from network); 14 Dec 2002 02:16:06 -0000 +Received: from unknown (HELO l-i-e.com) (127.0.0.1) + by localhost with SMTP; 14 Dec 2002 02:16:06 -0000 +Received: from 216.80.95.13 + (Hostbaby Webmail authenticated user typea@l-i-e.com) + by www.l-i-e.com with HTTP; Fri, 13 Dec 2002 18:16:06 -0800 (PST) +Message-ID: <49719.216.80.95.13.1039832166.squirrel@www.l-i-e.com> +Date: Fri, 13 Dec 2002 18:16:06 -0800 (PST) +Subject: ~* + LIMIT => infinite time? +From: +To: +In-Reply-To: <1038346393.1958.34.camel@rh72.home.ee> +References: + <61777.12.249.229.112.1038341633.squirrel@www.l-i-e.com> + <1038346393.1958.34.camel@rh72.home.ee> +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: 200212/158 +X-Sequence-Number: 574 + +I looked for a "known bugs" sort of database to search before bugging you +guys, but failed to find it... But I am at least asking before I submit a +new bug report :-) + +In version 7.1.3 on a Linux box: + +A particularly long, nasty query works "just fine" (returning seemingly +correct results in about 15 seconds) until I tack on "LIMIT 1" + +Adding LIMIT 1, however, seems to make the query take an infinite amount +of time. Well, more than 5 minutes, anyway, and I'm not that patient when +I know it worked okay without it the LIMIT, if you know what I mean. + +Here is the query: + +SELECT DISTINCT *, 0 + 10 * (lower(title) like '%albert einstein%') ::int ++ 10 * (lower(author_flattened) like '%albert einstein%') ::int + 30 * +(lower(subject_flattened) like '%albert einstein%') ::int + 9 * +(substring(lower(title), 1, 20) like '%albert%') ::int + 25 * +(substring(lower(text), 1, 20) LIKE '%albert%') ::int + (8 * (lower(title) +LIKE '%albert%' AND lower(title) LIKE '%einstein%' AND ((title ~* +'albert.{0,20}einstein') OR (title ~* 'einstein.{0,20}albert'))) ::int) + +(1 * ( (lower(title) LIKE '%albert%') )::int) + (1 * ( +(lower(author_flattened) LIKE '%albert%') )::int) + (1 * ( +(lower(subject_flattened) LIKE '%albert%') )::int) + 9 * +(substring(lower(title), 1, 20) like '%einstein%') ::int + 25 * +(substring(lower(text), 1, 20) LIKE '%einstein%') ::int + (8 * +(lower(title) LIKE '%einstein%' AND lower(title) LIKE '%albert%' AND +((title ~* 'einstein.{0,20}albert') OR (title ~* +'albert.{0,20}einstein'))) ::int) + (1 * ( (lower(title) LIKE +'%einstein%') )::int) + (1 * ( (lower(author_flattened) LIKE '%einstein%') +)::int) + (1 * ( (lower(subject_flattened) LIKE '%einstein%') )::int) AS +points FROM article WHERE FALSE OR (lower(title) LIKE '%albert%') OR +(lower(author_flattened) LIKE '%albert%') OR (lower(subject_flattened) +LIKE '%albert%') OR (lower(title) LIKE '%einstein%') OR +(lower(author_flattened) LIKE '%einstein%') OR (lower(subject_flattened) +LIKE '%einstein%') ORDER BY points desc, volume, number, article.article +LIMIT 1 , 1; + + +explain with or without the LIMIT part is about what you'd expect. + +Limit (cost=1596.50..1596.50 rows=1 width=216) + -> Unique (cost=1596.45..1596.50 rows=1 width=216) + -> Sort (cost=1596.45..1596.45 rows=1 width=216) + -> Seq Scan on article (cost=0.00..1596.44 rows=1 width=216) + +Obviously the "Limit" line is gone from the explain output when there is +no LIMIT, but the other lines are all the same. + +Is this a known bug, is there a fix or work-around? +If not, should I report it, or will the first answer be "Upgrade." ? + +The table in question has 17,000 reords, and the various fields mentioned +here are all rather short -- Just author names, subject lines, and titles +of text articles. [The articles themselves are super long, but are not +involved in this query.] + +I can take out the ~* parts, and life is good again, so almost for sure +that's a critical component in the failure. + +ps auxwwww | grep postgrs seems to report an "idle" postgres process for +each failed query -- attempting to ^C the query and/or killing the idle +process (I know, "Don't") is unfruitful. + +kill -9 does nuke the idle processes, IIRC, but I'm not 100% sure... + +I restarted the server soon after that, since (A) PHP command-line (aka +"CGI") was refusing to start, complaining about "mm" not being loadable, +and there was not much free RAM and the web-server was not particularly +happy about that state of affairs... + +The schema is probably not particularly interesting -- Pretty much every +field involved is a 'text' field, but here you go: + + Table "article" + Attribute | Type | Modifier +-------------------+---------+---------------------------------------------- + id | integer | not null default nextval('article_ID'::text) + volume | text | + number | text | + article | text | + date | text | + cover_date | text | + title | text | + author | text | + author_last | text | + author_first | text | + subject | text | + pages | text | + artwork | text | + text | text | + type | integer | + type_hardcoded | text | + type_detailed | integer | + abstract | text | + subject_flattened | text | + author_flattened | text | +Indices: article_id_index, + article_oid_index, + article_type_index + +Just FYI, the _flattened fields are de-normalizing (or is it +re-normalizing?) some relation tables so that we're not making a zillion +tuples here, and it's just a simple (we though) short and sweet text +search. + + +PS Thanks for all your help on the full text index! I'm still evaluating +some options, but a home-brew concordance is showing the most promise. +I'll post source/details if it works out. + + + + +From pgsql-performance-owner@postgresql.org Fri Dec 13 21:19:42 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0086D475E82 + for ; + Fri, 13 Dec 2002 21:19:41 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 650754758E1 + for ; + Fri, 13 Dec 2002 21:19:40 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2281061; Fri, 13 Dec 2002 18:20:11 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: , +Subject: Re: ~* + LIMIT => infinite time? +Date: Fri, 13 Dec 2002 18:23:32 -0800 +X-Mailer: KMail [version 1.4] +References: + <1038346393.1958.34.camel@rh72.home.ee> + <49719.216.80.95.13.1039832166.squirrel@www.l-i-e.com> +In-Reply-To: <49719.216.80.95.13.1039832166.squirrel@www.l-i-e.com> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212131823.32326.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/159 +X-Sequence-Number: 575 + +typea, + +> I looked for a "known bugs" sort of database to search before bugging you +> guys, but failed to find it... But I am at least asking before I submit a +> new bug report :-) +>=20 +> In version 7.1.3 on a Linux box: + +You'll get a snarky response, and then be told to upgrade, if you try to=20 +submit a bug in 7.1.3.=20=20 + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Dec 13 23:48:38 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D0F0A475D64 + for ; + Fri, 13 Dec 2002 23:48:36 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 218E94758E1 + for ; + Fri, 13 Dec 2002 23:48:36 -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 gBE4mcpd019878; + Fri, 13 Dec 2002 23:48:38 -0500 (EST) +To: josh@agliodbs.com +Cc: typea@l-i-e.com, pgsql-performance@postgresql.org +Subject: Re: ~* + LIMIT => infinite time? +In-reply-to: <200212131823.32326.josh@agliodbs.com> +References: + <1038346393.1958.34.camel@rh72.home.ee> + <49719.216.80.95.13.1039832166.squirrel@www.l-i-e.com> + <200212131823.32326.josh@agliodbs.com> +Comments: In-reply-to Josh Berkus + message dated "Fri, 13 Dec 2002 18:23:32 -0800" +Date: Fri, 13 Dec 2002 23:48:38 -0500 +Message-ID: <19877.1039841318@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/160 +X-Sequence-Number: 576 + +Josh Berkus writes: +> You'll get a snarky response, and then be told to upgrade, if you try to +> submit a bug in 7.1.3. + +7.1 is a tad long in the tooth, but still I'm curious about this. I +don't see how can possibly take longer than + . + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Sat Dec 14 14:47:27 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 5B9D2476386 + for ; + Sat, 14 Dec 2002 14:47:26 -0500 (EST) +Received: from lakemtao03.cox.net (lakemtao03.cox.net [68.1.17.242]) + by postgresql.org (Postfix) with ESMTP id C9E70475AD7 + for ; + Sat, 14 Dec 2002 14:46:17 -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 <20021214194618.FBNH26808.lakemtao03.cox.net@[192.168.1.1]> + for ; + Sat, 14 Dec 2002 14:46:18 -0500 +Subject: Re: automated index suggestor -- request for comment +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <20021213032238.GC8912@performics.com> +References: <20021213032238.GC8912@performics.com> +Content-Type: text/plain +Organization: +Message-Id: <1039895176.16976.26.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 14 Dec 2002 13:46:16 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/161 +X-Sequence-Number: 577 + +On Thu, 2002-12-12 at 21:22, johnnnnnn wrote: +> The manual is pretty sparse on advice regarding indices. Plenty of +> good feature documentation, but not much about when and where an index +> is appropriate (except a suggestion that multi-column indices should +> be avoided). +> +> Of course, the ultimate arbiter of which indices are used is the +> planner/optimizer. If i could somehow convince the optimizer to +> consider indices that don't yet exist, it could tell me which would +> give the greatest benefit should i add them. +> +> So, i'm writing for two reasons. First, i want to gauge interest in +> this tool. Is this something that people would find useful? +> +> Second, i am looking to solicit some advice. Is this project even +> feasible? If so, where would be the best place to start? My assumption +> has been that i would need to hack into the current code for +> determining index paths, and spoof it somehow, but is that possible +> without actually creating the indices? + +Isn't this what a DBA (or, heck, even a modestly bright developer) +does during transactional analysis? + +You know what the INSERTs and statements-that-have-WHERE-clauses +are, and, hopefully, approximately how often per day (or week) +each should execute. + +Then, *you* make the decision about which single-key and multi-key +indexes should be created, based upon +a) the cardinality of each table +b) the frequency each query (includes UPDATE & DELETE) is run +c) how often INSERT statements occur + +Thus, for example, an OLTP database will have a significantly +different mix of indexes than, say, a "reporting" database... +-- ++---------------------------------------------------------------+ +| 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-interfaces-owner@postgresql.org Sat Dec 14 17:58:38 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 302E14758BD + for ; + Sat, 14 Dec 2002 17:58:37 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP id E819C474E5C + for ; + Sat, 14 Dec 2002 17:58:35 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id gBEMwUH26494; + Sat, 14 Dec 2002 17:58:30 -0500 (EST) +From: Bruce Momjian +Message-Id: <200212142258.gBEMwUH26494@candle.pha.pa.us> +Subject: Re: [GENERAL] PerformPortalClose warning in 7.3 +In-Reply-To: <2C6CDB6A-0E24-11D7-8E88-000393A48A3C@mac.com> +To: Michael Engelhart +Date: Sat, 14 Dec 2002 17:58:30 -0500 (EST) +Cc: PostgreSQL-interfaces +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: 200212/42 +X-Sequence-Number: 3455 + + +I tried to reproduce the problem here but it seems my python is too old. +I am CC'ing this to the interfaces list in case someone there knows or +can test it. + +--------------------------------------------------------------------------- + +Michael Engelhart wrote: +> Hi - +> I've been running PostgreSQL 7.3 on Mac OS X 10.2 since it was released +> and it's been running fine. I'm using pyPgSQL 2.3 for client side +> programming which also was working great until tonight. Now whenever +> I do any query of any type, I get warnings like this: +> +> WARNING: PerformPortalClose: portal "pgsql_00179f10" not found +> +> It "appears" that everything is still working the way it was but it's a +> bit discomforting to have these show up on my screen while running my +> applications. +> +> Anyone that can explain this? +> +> Here's a tiny bit of Python sample code that I used to make sure it +> wasn't my other code causing the problems +> +> from pyPgSQL import PgSQL +> +> dbname = "template1" +> conn = PgSQL.connect(database=dbname) +> cursor = conn.cursor() +> sql = "SELECT now()"; +> cursor.execute(sql) +> res = cursor.fetchall() +> for i in res: +> print i +> cursor.close() +> conn.commit() +> +> strangely if I remove the last 2 lines (cursor.close() and +> conn.commit()) I don't get the errors. +> +> Also I don't notice that I don't have this problem with psql command +> line either. Is this the Python API causing this? +> +> Thanks for any help +> +> Mike +> +> +> ---------------------------(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 Sat Dec 14 19:42:27 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 451724758E6 + for ; + Sat, 14 Dec 2002 19:42:25 -0500 (EST) +Received: from o2.hostbaby.com (o2.hostbaby.com [208.187.29.121]) + by postgresql.org (Postfix) with SMTP id C8A6D47628F + for ; + Sat, 14 Dec 2002 19:41:52 -0500 (EST) +Received: (qmail 73236 invoked from network); 15 Dec 2002 00:41:54 -0000 +Received: from unknown (HELO l-i-e.com) (127.0.0.1) + by localhost with SMTP; 15 Dec 2002 00:41:54 -0000 +Received: from 12.249.229.112 + (Hostbaby Webmail authenticated user typea@l-i-e.com) + by www.l-i-e.com with HTTP; Sat, 14 Dec 2002 16:41:54 -0800 (PST) +Message-ID: <63165.12.249.229.112.1039912914.squirrel@www.l-i-e.com> +Date: Sat, 14 Dec 2002 16:41:54 -0800 (PST) +Subject: Re: ~* + LIMIT => infinite time? +From: +To: +In-Reply-To: <19877.1039841318@sss.pgh.pa.us> +References: + <1038346393.1958.34.camel@rh72.home.ee> + <49719.216.80.95.13.1039832166.squirrel@www.l-i-e.com> + <200212131823.32326.josh@agliodbs.com> + <19877.1039841318@sss.pgh.pa.us> +X-Priority: 3 +Importance: Normal +Cc: +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: 200212/162 +X-Sequence-Number: 578 + +> Josh Berkus writes: +>> You'll get a snarky response, and then be told to upgrade, if you try +>> to submit a bug in 7.1.3. +> +> 7.1 is a tad long in the tooth, but still I'm curious about this. I +> don't see how can possibly take longer than + node on top>. + +Hey Tom. I think we met very briefly at the International PHP Conference +in Frankfurt in 2001... Anyway. + +It's actually the other way around. takes like 4 seconds. + takes literally FOREVER and leaves a postgres +process hanging 'round that I have to kill -9 to get rid of. + +I'd understand the LIMIT clause taking a bit longer, or being faster for +startup (if there were no ORDER BY, which there is) but I never even +considered it would hang the whole thing. Actually, PostgreSQL has been +so reliable over the years, the idea that I'd run across a bug was just +foreign to me... So I've been trying to tune performance on this query +for weeks now, not realizing that the speed wasn't the issue at all. I +could almost rip out the LIMIT completely if the application logic let me, +and if the performance were a bit better. + +It occurred to me last night that the actual data *MIGHT* be involved -- +It's some OCR text, and there are a few scattered non-ASCII characters +involved... So *MAYBE* the actual text getting scanned could also be +important. + +It seems unlikely, since the non-LIMIT query returns all the data just +fine, but just in case... + +Here's a schema and a full dump for anybody that wants to dig in: +http://bulletinarchive.org/pg_dump/ + +I could provide PHP source as well, or the query posted in this thread can +serve as the test case. + +At the moment, I've altered the application to not use LIMIT when I have +~* in the query, and it "works" -- only the paging of results is broken, +and the whole page takes twice as long to load as it should in those +cases, since it's doing the same query twice and snarfing all the monster +data and then throwing away the majority of rows in both cases. I need +the first row to get the highest score, and the rows for paging in the +real application... + +Anyway, my point is that the queries seem fine without the LIMIT clause, +and "hang" with both "~*" and LIMIT, and I've even gone so far as to +incorporate that into the application logic for now, just to have a page +that loads at all instead of one that hangs. + +Meanwhile, I guess I should flail at it and try 7.3 in the hopes the bug +disappeared. I was hoping to know for sure that it was a fixed bug in +that upgrade path. + +Boss actually said we should go ahead and upgrade just on principle +anyway. It's nice to have a smart boss. :-) + + + + +From pgsql-performance-owner@postgresql.org Sun Dec 15 15:21:53 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 19244475C22 + for ; + Sun, 15 Dec 2002 15:21:52 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 57463475B99 + for ; + Sun, 15 Dec 2002 15:21:51 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2282278; Sun, 15 Dec 2002 12:22:25 -0800 +From: "Josh Berkus" +Subject: Re: ~* + LIMIT => infinite time? +To: , +Cc: +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Sun, 15 Dec 2002 12:22:25 -0800 +Message-ID: +In-Reply-To: <63165.12.249.229.112.1039912914.squirrel@www.l-i-e.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: 200212/163 +X-Sequence-Number: 579 + +Typea, + +> At the moment, I've altered the application to not use LIMIT when I +> have +> ~* in the query, and it "works" -- only the paging of results is +> broken, + +Would your application allow you to use " ILIKE '%%'" in the +query instead of "~*" ? If so, does the query still hang with ILIKE +... LIMIT? + +-Josh + +From pgsql-performance-owner@postgresql.org Sun Dec 15 19:04:07 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 10B6E475EF7 + for ; + Sun, 15 Dec 2002 19:04:06 -0500 (EST) +Received: from rh72.home.ee (adsl1030.estpak.ee [213.168.29.11]) + by postgresql.org (Postfix) with ESMTP id 16E56475D87 + for ; + Sun, 15 Dec 2002 19:04:05 -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 gBG044ph014158; + Mon, 16 Dec 2002 05:04:04 +0500 +Received: (from hannu@localhost) + by rh72.home.ee (8.12.5/8.12.5/Submit) id gBG03tmd014156; + Mon, 16 Dec 2002 05:03:55 +0500 +X-Authentication-Warning: rh72.home.ee: hannu set sender to hannu@tm.ee using + -f +Subject: Re: ~* + LIMIT => infinite time? +From: Hannu Krosing +To: typea@l-i-e.com +Cc: tgl@sss.pgh.pa.us, pgsql-performance@postgresql.org +In-Reply-To: <63165.12.249.229.112.1039912914.squirrel@www.l-i-e.com> +References: + <1038346393.1958.34.camel@rh72.home.ee> + <49719.216.80.95.13.1039832166.squirrel@www.l-i-e.com> + <200212131823.32326.josh@agliodbs.com> <19877.1039841318@sss.pgh.pa.us> + <63165.12.249.229.112.1039912914.squirrel@www.l-i-e.com> +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +Organization: +Message-Id: <1039997033.12952.6.camel@rh72.home.ee> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.1 +Date: 16 Dec 2002 05:03:54 +0500 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/164 +X-Sequence-Number: 580 + +typea@l-i-e.com kirjutas P, 15.12.2002 kell 05:41: +> It occurred to me last night that the actual data *MIGHT* be involved -- +> It's some OCR text, and there are a few scattered non-ASCII characters +> involved... So *MAYBE* the actual text getting scanned could also be +> important. +> +> It seems unlikely, since the non-LIMIT query returns all the data just +> fine, but just in case... + +Have you tried using DECLARE CURSOR...; FETCH 1; CLOSE CURSOR; instead +of LIMIT ? + +> Here's a schema and a full dump for anybody that wants to dig in: +> http://bulletinarchive.org/pg_dump/ + +gzipping the data could make sense - data.sql goes from 200M to 60M ;) + +> I could provide PHP source as well, or the query posted in this thread can +> serve as the test case. +> +> At the moment, I've altered the application to not use LIMIT when I have +> ~* in the query, and it "works" -- only the paging of results is broken, +> and the whole page takes twice as long to load as it should in those +> cases, since it's doing the same query twice and snarfing all the monster +> data and then throwing away the majority of rows in both cases. I need +> the first row to get the highest score, and the rows for paging in the +> real application... +> +> Anyway, my point is that the queries seem fine without the LIMIT clause, +> and "hang" with both "~*" and LIMIT, and I've even gone so far as to +> incorporate that into the application logic for now, just to have a page +> that loads at all instead of one that hangs. +> +> Meanwhile, I guess I should flail at it and try 7.3 in the hopes the bug +> disappeared. + +I tested (part of) it on 7.3 , had to manually change ::int to +case-when-then-else-end as there is no cast from bool to int in7.3 + +This ran fine: + +SELECT DISTINCT + *, + 0 + case when (title ilike '%albert einstein%') then 10 else 0 end + + case when ( title iLIKE '%einstein%' + AND title iLIKE '%albert%' + AND ( (title ~* 'einstein.{0,20}albert') + OR (title ~* 'albert.{0,20}einstein'))) then 8 else 0 +end + as points + FROM article +WHERE FALSE + OR (title iLIKE '%albert%') + OR (author_flattened iLIKE '%albert%') + OR (subject_flattened iLIKE '%albert%') + OR (title iLIKE '%einstein%') + OR (author_flattened iLIKE '%einstein%') + OR (subject_flattened iLIKE '%einstein%') +ORDER BY points desc, volume, number, article.article +LIMIT 1 OFFSET 1; + +I also changed + "lower(field) like '%albert%'" + to + "field ilike '%albert%'" + +and got about 20% speed boost - EXPLAIN ANALYZE reported 0.189 insead of +0.263 sec as actual time. + +> I was hoping to know for sure that it was a fixed bug in +> that upgrade path. +> +> Boss actually said we should go ahead and upgrade just on principle +> anyway. It's nice to have a smart boss. :-) +> +> +> +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 2: you can get off all lists at once with the unregister command +> (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) +-- +Hannu Krosing + +From pgsql-performance-owner@postgresql.org Mon Dec 16 03:21:08 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6EFB7475ADD + for ; + Mon, 16 Dec 2002 03:21:07 -0500 (EST) +Received: from o2.hostbaby.com (o2.hostbaby.com [208.187.29.121]) + by postgresql.org (Postfix) with SMTP id AAF884759BD + for ; + Mon, 16 Dec 2002 03:21:06 -0500 (EST) +Received: (qmail 24743 invoked from network); 16 Dec 2002 08:21:14 -0000 +Received: from unknown (HELO l-i-e.com) (127.0.0.1) + by localhost with SMTP; 16 Dec 2002 08:21:14 -0000 +Received: from 12.249.229.112 + (Hostbaby Webmail authenticated user typea@l-i-e.com) + by www.l-i-e.com with HTTP; Mon, 16 Dec 2002 00:21:14 -0800 (PST) +Message-ID: <61988.12.249.229.112.1040026874.squirrel@www.l-i-e.com> +Date: Mon, 16 Dec 2002 00:21:14 -0800 (PST) +Subject: Re: ~* + LIMIT => infinite time? +From: +To: +In-Reply-To: <1039997033.12952.6.camel@rh72.home.ee> +References: + <1038346393.1958.34.camel@rh72.home.ee> + <49719.216.80.95.13.1039832166.squirrel@www.l-i-e.com> + <200212131823.32326.josh@agliodbs.com> + <19877.1039841318@sss.pgh.pa.us> + <63165.12.249.229.112.1039912914.squirrel@www.l-i-e.com> + <1039997033.12952.6.camel@rh72.home.ee> +X-Priority: 3 +Importance: Normal +Cc: , , +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: 200212/165 +X-Sequence-Number: 581 + +> Have you tried using DECLARE CURSOR...; FETCH 1; CLOSE CURSOR; instead +> of LIMIT ? + +I think I did, in the monitory, and it worked fine. + +> I tested (part of) it on 7.3 , had to manually change ::int to +> case-when-then-else-end as there is no cast from bool to int in7.3 + +An upgrade to 7.3 has, in fact, gotten rid of that bug... + +Though now I'm forced to use localhost for connecting, since: +A) Upon boot, I'm told I can't use password or crypt, but +B) When trying to connect, I can't use md5 +C) the passwords get turned into md5 whether I like it or not +What's up with all that? + +I also don't understand why the incredibly useful function I had to +auto-typecast from bool to int won't work using ::int syntax, but will if +I use int4(...) syntax. Grrr. + +And breaking the LIMIT x, y thing was annoying. + +Oh well. I can move forward with some changes in the way we do things. + +Now that the query runs, I can start in on the optimization again :-) + +THANKS ALL!!! + +Oh, and the lower(field) LIKE is MySQL compatible, but I don't think MySQL +has an ILIKE... We're abandoning the MySQL support now anyway, since we +NEED performance way more than we need MySQL compatibility. + +Thanks again! + + + + +From pgsql-performance-owner@postgresql.org Mon Dec 16 05:20:21 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CAE9A475BC3 + for ; + Mon, 16 Dec 2002 05:20:19 -0500 (EST) +Received: from o2.hostbaby.com (o2.hostbaby.com [208.187.29.121]) + by postgresql.org (Postfix) with SMTP id ECB034759BD + for ; + Mon, 16 Dec 2002 05:20:18 -0500 (EST) +Received: (qmail 58018 invoked from network); 16 Dec 2002 10:20:27 -0000 +Received: from unknown (HELO l-i-e.com) (127.0.0.1) + by localhost with SMTP; 16 Dec 2002 10:20:27 -0000 +Received: from 12.249.229.112 + (Hostbaby Webmail authenticated user typea@l-i-e.com) + by www.l-i-e.com with HTTP; Mon, 16 Dec 2002 02:20:27 -0800 (PST) +Message-ID: <64288.12.249.229.112.1040034027.squirrel@www.l-i-e.com> +Date: Mon, 16 Dec 2002 02:20:27 -0800 (PST) +Subject: Re: ~* + LIMIT => infinite time? +From: +To: +In-Reply-To: <61988.12.249.229.112.1040026874.squirrel@www.l-i-e.com> +References: + <1038346393.1958.34.camel@rh72.home.ee> + <49719.216.80.95.13.1039832166.squirrel@www.l-i-e.com> + <200212131823.32326.josh@agliodbs.com> + <19877.1039841318@sss.pgh.pa.us> + <63165.12.249.229.112.1039912914.squirrel@www.l-i-e.com> + <1039997033.12952.6.camel@rh72.home.ee> + <61988.12.249.229.112.1040026874.squirrel@www.l-i-e.com> +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: 200212/166 +X-Sequence-Number: 582 + +>> I tested (part of) it on 7.3 , had to manually change ::int to +>> case-when-then-else-end as there is no cast from bool to int in7.3 +> +> An upgrade to 7.3 has, in fact, gotten rid of that bug... + +Damn. I spoke to soon. It *SEEMS* like it's back again. Very, very +strange. + +If explain claims the "cost" will be ~1000, and then a query takes SO long +to return I give up and hit ^C, that's just not right, right? I mean, +that "cost" near 1000 may not be in seconds or anything, but 1000 is +pretty low, isn't it? + +I give up for now. Need sleep. + + + + + +From pgsql-performance-owner@postgresql.org Mon Dec 16 13:29:02 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 197EC476607 + for ; + Mon, 16 Dec 2002 13:29:02 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 9EFAE47634E + for ; + Mon, 16 Dec 2002 13:25:41 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2283495; Mon, 16 Dec 2002 10:26:24 -0800 +From: "Josh Berkus" +Subject: Re: ~* + LIMIT => infinite time? +To: , +Cc: , , +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Mon, 16 Dec 2002 10:26:24 -0800 +Message-ID: +In-Reply-To: <61988.12.249.229.112.1040026874.squirrel@www.l-i-e.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: 200212/167 +X-Sequence-Number: 583 + +Typea, + +> Oh, and the lower(field) LIKE is MySQL compatible, but I don't think +> MySQL +> has an ILIKE... We're abandoning the MySQL support now anyway, since +> we +> NEED performance way more than we need MySQL compatibility. + +ILIKE is SQL-spec. There's reasons to use any: + +ILIKE is slightly faster on un-anchored text searches ("name ILIKE +'%john%'") + +lower(column) can be indexed for anchored text searches ("lower(name) +LIKE 'john%'") + +"~*" cannot be indexed, but will accept regexp operators for +sophisticated text searches ("name ~* 'jo[han]n?'") + +-Josh Berkus + +From pgsql-performance-owner@postgresql.org Mon Dec 16 13:35:42 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 790784762D1 + for ; + Mon, 16 Dec 2002 13:35:40 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 7C9CF476584 + for ; + Mon, 16 Dec 2002 13:35:00 -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 gBGIYnpd022969; + Mon, 16 Dec 2002 13:34:49 -0500 (EST) +To: "Josh Berkus" +Cc: typea@l-i-e.com, hannu@tm.ee, pgsql-performance@postgresql.org +Subject: Re: ~* + LIMIT => infinite time? +In-reply-to: +References: +Comments: In-reply-to "Josh Berkus" + message dated "Mon, 16 Dec 2002 10:26:24 -0800" +Date: Mon, 16 Dec 2002 13:34:49 -0500 +Message-ID: <22968.1040063689@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/168 +X-Sequence-Number: 584 + +"Josh Berkus" writes: +> ILIKE is SQL-spec. + +It is? I don't see it in there ... + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Mon Dec 16 13:55:27 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A60994764B4 + for ; + Mon, 16 Dec 2002 13:55:25 -0500 (EST) +Received: from mailhost1.mistral.co.uk (mailhost1.mistral.co.uk + [195.184.229.180]) + by postgresql.org (Postfix) with ESMTP id C3E734764A6 + for ; + Mon, 16 Dec 2002 13:55:23 -0500 (EST) +Received: from test.xorch.net.netcomuk.co.uk (adsl-217-154-8-180.mistral.co.uk + [217.154.8.180]) + by mailhost1.mistral.co.uk (Postfix) with ESMTP id 02B2F78332 + for ; + Mon, 16 Dec 2002 18:55:22 +0000 (GMT) +From: Jeff Davis +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Message-ID: <15870.8609.145600.122190@test.xorch.net> +Date: Mon, 16 Dec 2002 13:55:29 -0500 +To: pgsql-performance@postgresql.org +Subject: Problem with GEQO when using views and nested selects +X-Mailer: VM 7.07 under 21.4 (patch 6) "Common Lisp" XEmacs Lucid +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/169 +X-Sequence-Number: 585 + +I have been trying tune joins against a view we use a lot for which +the optimizer generates very poor query plans when it uses the GEQO. +The long involved version (and more readable version) of the problem +is here: http://xarg.net/writing/misc/GEQO + +I have tried doing a variety of explicit joins but generally end up +with something a lot poorer than the result from the exhaustive +search. I am hoping someone has some advice on how to tackle this (my +inclination is to turn of GEQO since we use this and similiarly +complex views quite a lot and with a poor plan these queries are very +slow, I would trade predictably slow query planning against +unpredictably slow queries I guess). + + +Anyway, Here is the view: + +create view cc_users as +SELECT o.*, pa.*, pe.*, u.*, mr.member_state, mr.rel_id + FROM acs_objects o, parties pa, persons pe, users u, group_member_map m, membership_rels mr + WHERE o.object_id = pa.party_id + and pa.party_id = pe.person_id + and pe.person_id = u.user_id + and u.user_id = m.member_id + and m.group_id = acs__magic_object_id('registered_users') + and m.rel_id = mr.rel_id + and m.container_id = m.group_id; + + +and here are the two query plans: + +oatest=# set geqo_threshold to 11; explain analyze select * from cc_users u, forums_messages m where u.user_id = m.user_id and m.message_id = 55001; +SET VARIABLE +NOTICE: QUERY PLAN: + +Nested Loop (cost=15202.01..19099.49 rows=1 width=1483) (actual time=6012.96..6054.26 rows=1 loops=1) + -> Index Scan using forums_messages_pk on forums_messages m (cost=0.00..3.38 rows=1 width=983) (actual time=0.06..0.08 rows=1 loops=1) + -> Materialize (cost=18571.15..18571.15 rows=41997 width=500) (actual time=5996.36..6009.62 rows=42002 loops=1) + -> Hash Join (cost=15202.01..18571.15 rows=41997 width=500) (actual time=4558.36..5920.36 rows=42002 loops=1) + -> Merge Join (cost=0.00..3089.82 rows=42002 width=354) (actual time=0.13..651.67 rows=42002 loops=1) + -> Index Scan using parties_pk on parties pa (cost=0.00..992.58 rows=42018 width=146) (actual time=0.05..122.78 rows=42018 loops=1) + -> Index Scan using users_pk on users u (cost=0.00..1362.17 rows=42002 width=208) (actual time=0.03..223.07 rows=42002 loops=1) + -> Hash (cost=15097.01..15097.01 rows=41997 width=146) (actual time=4558.05..4558.05 rows=0 loops=1) + -> Hash Join (cost=4639.30..15097.01 rows=41997 width=146) (actual time=1512.75..4445.08 rows=42002 loops=1) + -> Seq Scan on acs_objects o (cost=0.00..8342.17 rows=318117 width=90) (actual time=0.03..1567.37 rows=318117 loops=1) + -> Hash (cost=4534.30..4534.30 rows=41997 width=56) (actual time=1511.87..1511.87 rows=0 loops=1) + -> Hash Join (cost=2951.31..4534.30 rows=41997 width=56) (actual time=857.33..1291.41 rows=42002 loops=1) + -> Seq Scan on persons pe (cost=0.00..848.02 rows=42002 width=32) (actual time=0.01..73.65 rows=42002 loops=1) + -> Hash (cost=2846.30..2846.30 rows=42004 width=24) (actual time=856.92..856.92 rows=0 loops=1) + -> Hash Join (cost=1318.18..2846.30 rows=42004 width=24) (actual time=584.26..806.18 rows=42002 loops=1) + -> Seq Scan on membership_rels mr (cost=0.00..688.04 rows=42004 width=16) (actual time=0.01..60.95 rows=42004 loops=1) + -> Hash (cost=1213.16..1213.16 rows=42009 width=8) (actual time=583.69..583.69 rows=0 loops=1) + -> Seq Scan on group_element_index (cost=0.00..1213.16 rows=42009 width=8) (actual time=0.05..430.06 rows=42002 loops=1) +Total runtime: 6064.47 msec + +------------------------------------------------------------ + +oatest=# set geqo_threshold to 15; explain analyze select * from cc_users u, forums_messages m where u.user_id = m.user_id and m.message_id = 55001; +SET VARIABLE +NOTICE: QUERY PLAN: + +Nested Loop (cost=0.00..21.65 rows=1 width=1483) (actual time=0.42..0.44 rows=1 loops=1) + -> Nested Loop (cost=0.00..18.62 rows=1 width=1451) (actual time=0.36..0.37 rows=1 loops=1) + -> Nested Loop (cost=0.00..15.59 rows=1 width=1435) (actual time=0.30..0.32 rows=1 loops=1) + -> Nested Loop (cost=0.00..12.54 rows=1 width=1289) (actual time=0.22..0.23 rows=1 loops=1) + -> Nested Loop (cost=0.00..9.44 rows=1 width=1199) (actual time=0.17..0.18 rows=1 loops=1) + -> Nested Loop (cost=0.00..6.41 rows=1 width=991) (actual time=0.12..0.13 rows=1 loops=1) + -> Index Scan using forums_messages_pk on forums_messages m (cost=0.00..3.38 rows=1 width=983) (actual time=0.06..0.06 rows=1 loops=1) + -> Index Scan using group_elem_idx_element_idx on group_element_index (cost=0.00..3.02 rows=1 width=8) (actual time=0.05..0.05 rows=1 loops=1) + -> Index Scan using users_pk on users u (cost=0.00..3.02 rows=1 width=208) (actual time=0.03..0.03 rows=1 loops=1) + -> Index Scan using acs_objects_pk on acs_objects o (cost=0.00..3.08 rows=1 width=90) (actual time=0.03..0.03 rows=1 loops=1) + -> Index Scan using parties_pk on parties pa (cost=0.00..3.04 rows=1 width=146) (actual time=0.05..0.05 rows=1 loops=1) + -> Index Scan using membership_rel_rel_id_pk on membership_rels mr (cost=0.00..3.01 rows=1 width=16) (actual time=0.02..0.02 rows=1 loops=1) + -> Index Scan using persons_pk on persons pe (cost=0.00..3.01 rows=1 width=32) (actual time=0.03..0.03 rows=1 loops=1) +Total runtime: 1.01 msec + + +From pgsql-performance-owner@postgresql.org Mon Dec 16 14:30:33 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id ADC1A476450 + for ; + Mon, 16 Dec 2002 14:30:29 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 0BE1347634E + for ; + Mon, 16 Dec 2002 14:30:28 -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 gBGJUGpd023508; + Mon, 16 Dec 2002 14:30:16 -0500 (EST) +To: Jeff Davis +Cc: pgsql-performance@postgresql.org +Subject: Re: Problem with GEQO when using views and nested selects +In-reply-to: <15870.8609.145600.122190@test.xorch.net> +References: <15870.8609.145600.122190@test.xorch.net> +Comments: In-reply-to Jeff Davis + message dated "Mon, 16 Dec 2002 13:55:29 -0500" +Date: Mon, 16 Dec 2002 14:30:16 -0500 +Message-ID: <23507.1040067016@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/170 +X-Sequence-Number: 586 + +Jeff Davis writes: +> I have been trying tune joins against a view we use a lot for which +> the optimizer generates very poor query plans when it uses the GEQO. +> The long involved version (and more readable version) of the problem +> is here: http://xarg.net/writing/misc/GEQO + +This is not actually using GEQO. The reason you are seeing an effect +from raising geqo_threshold is that geqo_threshold determines whether +or not the view will be flattened into the upper query. For this +particular query situation, flattening the view is essential (since you +don't want the thing to compute the whole view). The relevant source +code tidbit is + + /* + * Yes, so do we want to merge it into parent? Always do + * so if child has just one element (since that doesn't + * make the parent's list any longer). Otherwise we have + * to be careful about the increase in planning time + * caused by combining the two join search spaces into + * one. Our heuristic is to merge if the merge will + * produce a join list no longer than GEQO_RELS/2. + * (Perhaps need an additional user parameter?) + */ + +AFAICS, your only good solution is to make geqo_threshold at least 14, +since you want a 7-way join after flattening. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Mon Dec 16 16:52:20 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B734C476711 + for ; + Mon, 16 Dec 2002 16:52:18 -0500 (EST) +Received: from mailhost1.mistral.co.uk (mailhost1.mistral.co.uk + [195.184.229.180]) + by postgresql.org (Postfix) with ESMTP id 3DF7F4766AB + for ; + Mon, 16 Dec 2002 16:47:08 -0500 (EST) +Received: from test.xorch.net.netcomuk.co.uk (adsl-217-154-8-180.mistral.co.uk + [217.154.8.180]) by mailhost1.mistral.co.uk (Postfix) with ESMTP + id 3C94178DBE; Mon, 16 Dec 2002 21:47:09 +0000 (GMT) +From: Jeff Davis +MIME-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Transfer-Encoding: 7bit +Message-ID: <15870.18917.306678.855332@test.xorch.net> +Date: Mon, 16 Dec 2002 16:47:17 -0500 +To: Tom Lane +Cc: pgsql-performance@postgresql.org +Subject: Re: Problem with GEQO when using views and nested selects +In-Reply-To: <23507.1040067016@sss.pgh.pa.us> +References: <15870.8609.145600.122190@test.xorch.net> + <23507.1040067016@sss.pgh.pa.us> +X-Mailer: VM 7.07 under 21.4 (patch 6) "Common Lisp" XEmacs Lucid +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/171 +X-Sequence-Number: 587 + + Tom> Jeff Davis writes: + >> I have been trying tune joins against a view we use a lot for which + >> the optimizer generates very poor query plans when it uses the GEQO. + >> The long involved version (and more readable version) of the problem + >> is here: http://xarg.net/writing/misc/GEQO + + Tom> This is not actually using GEQO. The reason you are seeing an effect + Tom> from raising geqo_threshold is that geqo_threshold determines whether + Tom> or not the view will be flattened into the upper query. For this + Tom> particular query situation, flattening the view is essential (since you + Tom> don't want the thing to compute the whole view). The relevant source + Tom> code tidbit is + + Tom> /* + Tom> * Yes, so do we want to merge it into parent? Always do + Tom> * so if child has just one element (since that doesn't + Tom> * make the parent's list any longer). Otherwise we have + Tom> * to be careful about the increase in planning time + Tom> * caused by combining the two join search spaces into + Tom> * one. Our heuristic is to merge if the merge will + Tom> * produce a join list no longer than GEQO_RELS/2. + Tom> * (Perhaps need an additional user parameter?) + Tom> */ + + Tom> AFAICS, your only good solution is to make geqo_threshold at least 14, + Tom> since you want a 7-way join after flattening. + +Thanks very much. I have to admit it was all very mysterious to me +and the only knobs I had seemed to indicate that the GEQO was the +issue. + +I think having another user parameter as mentioned in the comment is a +good idea (although I see it's been discussed before), that or maybe +some better guidance on the actual interpretation of GEQO_THRESHOLD +(the comment is hugely more illuminating than the documentation on +this point). + +Now that I understand what is going on, I know in our case this crops +up a fair bit and no one had really figured ever figured out what was +causing views to work ok some of the time and then fall over in other +queries. + + + + + +From pgsql-performance-owner@postgresql.org Mon Dec 16 23:03:02 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1337B4761BD + for ; + Mon, 16 Dec 2002 23:03:01 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP id 710174761A3 + for ; + Mon, 16 Dec 2002 23:03:00 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2284485 for ; + Mon, 16 Dec 2002 20:03:51 -0800 +From: "Josh Berkus" +Subject: Profiling +To: pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Mon, 16 Dec 2002 20:03:51 -0800 +Message-ID: +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: 200212/172 +X-Sequence-Number: 588 + +Folks, + +I had a request from one of the SF-PUG members that I found +interesting. She suggested that we post the specs of some of the +PostgreSQL servers that we administrate, their statistics, and some +comments on how they perform. I'll start it off with an example: + +Small Cheap Workgroup Server +AMD Athalon 700mhz +256mb SDRAM +Dual 20gb 7200rpm IDE Drives (1 IBM, 1 Quantum) + with OS, Apache, XLog on 1st drive, + Postgres Database, Swap on 2nd drive +Running SuSE Linux 7.3 + Apache 1.3.x + PHP 4.0.x + PostgreSQL 7.1.3 +3-8 concurrent users on intranet application +with large transactions but low transaction frequency +(est. 20-300 reads and 5-80 writes per hour) +on small database (< 20,000 records combined in main tables) + +Performance assessment: Adequate, reasonably fast +on selects except aggregates, commits taking 5-20 seconds +during medium activity. Same system with a Celeron 500 +previously demonstrated horrible performance (often > 45 seconds +on selects) on complex queries, such as one view with +custom aggregates. + + +-Josh Berkus + + +______AGLIO DATABASE SOLUTIONS___________________________ + Josh Berkus + Complete information technology josh@agliodbs.com + and data management solutions (415) 565-7293 + for law firms, small businesses fax 621-2533 + and non-profit organizations. San Francisco + +From pgsql-performance-owner@postgresql.org Mon Dec 16 23:12:03 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C6952475ED4 + for ; + Mon, 16 Dec 2002 23:12:01 -0500 (EST) +Received: from davinci.ethosmedia.com (davinci.ethosmedia.com [209.10.40.250]) + by postgresql.org (Postfix) with ESMTP + id 23B6F475D1C; Mon, 16 Dec 2002 23:12:01 -0500 (EST) +Received: by davinci.ethosmedia.com (CommuniGate Pro PIPE 4.0.2) + with PIPE id 2284498; Mon, 16 Dec 2002 20:12:52 -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 2284500; Mon, 16 Dec 2002 20:12:47 -0800 +From: "Josh Berkus" +Subject: Re: Profiling +To: "Josh Berkus" , + pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Mon, 16 Dec 2002 20:12:47 -0800 +Message-ID: +In-Reply-To: +MIME-Version: 1.0 +Content-Type: text/plain; charset="ISO-8859-1" +Content-Transfer-Encoding: 8bit +X-Spam-Status: No, hits=-4.1 required=6.0 tests=IN_REP_TO,AWL version=2.20 +X-Spam-Level: +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/173 +X-Sequence-Number: 589 + +Folks, + +> I had a request from one of the SF-PUG members that I found +> interesting. She suggested that we post the specs of some of the +> PostgreSQL servers that we administrate, their statistics, and some +> comments on how they perform. I'll start it off with an example: +> +> Small Cheap Workgroup Server +> AMD Athalon 700mhz +> 256mb SDRAM +> Dual 20gb 7200rpm IDE Drives (1 IBM, 1 Quantum) +> with OS, Apache, XLog on 1st drive, +> Postgres Database, Swap on 2nd drive +> Running SuSE Linux 7.3 +> Apache 1.3.x +> PHP 4.0.x +> PostgreSQL 7.1.3 +> 3-8 concurrent users on intranet application +> with large transactions but low transaction frequency +> (est. 20-300 reads and 5-80 writes per hour) +> on small database (< 20,000 records combined in main tables) +> +> Performance assessment: Adequate, reasonably fast +> on selects except aggregates, commits taking 5-20 seconds +> during medium activity. Same system with a Celeron 500 +> previously demonstrated horrible performance (often > 45 seconds +> on selects) on complex queries, such as one view with +> custom aggregates. + +Oh, and I forgot: + +shared_buffers 4096 +sort_mem 2048 +wal_files 8 +wal_sync_method = fdatasync + +-Josh + +______AGLIO DATABASE SOLUTIONS___________________________ + Josh Berkus + Complete information technology josh@agliodbs.com + and data management solutions (415) 565-7293 + for law firms, small businesses fax 621-2533 + and non-profit organizations. San Francisco + +From pgsql-performance-owner@postgresql.org Mon Dec 16 23:30:56 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id F1463475D1C + for ; + Mon, 16 Dec 2002 23:30:54 -0500 (EST) +Received: from smtp3.ihug.com.au (smtp3.ihug.com.au [203.109.250.76]) + by postgresql.org (Postfix) with ESMTP id 23EAB475CBC + for ; + Mon, 16 Dec 2002 23:30:54 -0500 (EST) +Received: from p108-tnt1.mel.ihug.com.au (postgresql.org) [203.173.160.108] + by smtp3.ihug.com.au with esmtp (Exim 3.22 #1 (Debian)) + id 18O9Nh-0003HS-00; Tue, 17 Dec 2002 15:30:57 +1100 +Message-ID: <3DFEA87F.9040304@postgresql.org> +Date: Tue, 17 Dec 2002 15:30:55 +1100 +From: Justin Clift +User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.1) Gecko/20020826 +X-Accept-Language: en-au, en-gb, en-us, en +MIME-Version: 1.0 +To: Josh Berkus +Cc: pgsql-performance@postgresql.org +Subject: Re: Profiling +References: +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/174 +X-Sequence-Number: 590 + +Josh Berkus wrote: +> Folks, +> +> +>>I had a request from one of the SF-PUG members that I found +>>interesting. She suggested that we post the specs of some of the +>>PostgreSQL servers that we administrate, their statistics, and some +>>comments on how they perform. I'll start it off with an example: +>> +>>Small Cheap Workgroup Server +>>AMD Athalon 700mhz +>>256mb SDRAM +>>Dual 20gb 7200rpm IDE Drives (1 IBM, 1 Quantum) +>> with OS, Apache, XLog on 1st drive, +>> Postgres Database, Swap on 2nd drive +>>Running SuSE Linux 7.3 +>> Apache 1.3.x +>> PHP 4.0.x +>> PostgreSQL 7.1.3 +>>3-8 concurrent users on intranet application +>>with large transactions but low transaction frequency +>>(est. 20-300 reads and 5-80 writes per hour) +>>on small database (< 20,000 records combined in main tables) +>> +>>Performance assessment: Adequate, reasonably fast +>>on selects except aggregates, commits taking 5-20 seconds +>>during medium activity. Same system with a Celeron 500 +>>previously demonstrated horrible performance (often > 45 seconds +>>on selects) on complex queries, such as one view with +>>custom aggregates. +> +> +> Oh, and I forgot: +> +> shared_buffers 4096 +> sort_mem 2048 +> wal_files 8 +> wal_sync_method = fdatasync + +Hi Josh, + +Want to CVS checkout the latest OSDB source code (http://www.sf.net/projects/osdb), generate say a 100MB database and do +a multiuser test of 20 or so users on it? + +:-) + +Regards and best wishes, + +Justin Clift + + +> -Josh +> +> ______AGLIO DATABASE SOLUTIONS___________________________ +> Josh Berkus +> Complete information technology josh@agliodbs.com +> and data management solutions (415) 565-7293 +> for law firms, small businesses fax 621-2533 +> and non-profit organizations. San Francisco +> +> ---------------------------(end of broadcast)--------------------------- +> TIP 5: Have you checked our extensive FAQ? +> +> http://www.postgresql.org/users-lounge/docs/faq.html + + +-- +"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 Dec 17 01:56:48 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B3F73475D4B + for ; + Tue, 17 Dec 2002 01:56:46 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 91535475D1C + for ; + Tue, 17 Dec 2002 01:56:42 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id gBH6uf313575 + for ; Tue, 17 Dec 2002 12:26:41 +0530 +Received: from daithan.itnranet.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 gBH6uf013570 + for ; Tue, 17 Dec 2002 12:26:41 +0530 +Content-Type: text/plain; + charset="iso-8859-1" +From: Shridhar Daithankar +To: pgsql-performance@postgresql.org +Subject: Re: Profiling +Date: Tue, 17 Dec 2002 12:27:07 +0530 +User-Agent: KMail/1.4.3 +References: +In-Reply-To: +MIME-Version: 1.0 +Message-Id: <200212171227.07258.shridhar_daithankar@persistent.co.in> +Content-Transfer-Encoding: 8bit +X-MIME-Autoconverted: from quoted-printable to 8bit by www.pspl.co.in id + gBH6uf013570 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/175 +X-Sequence-Number: 591 + +On Tuesday 17 December 2002 09:33 am, you wrote: +> Folks, +> +> I had a request from one of the SF-PUG members that I found +> interesting. She suggested that we post the specs of some of the +> PostgreSQL servers that we administrate, their statistics, and some +> comments on how they perform. I'll start it off with an example: + +OK my take. + +P-II-450MHz/256MB/20GB IDE. Mandrake8.2, postgresql 7.2.x + +PGBench, with 10M records/10,000 transactions/10 users. + +Throughput 25tps. + +Rest of the things were default. I am not too sure of details as this was more +than 4 months back and that machine is windows now. + +Same machine/Another benchmark + +Banking application simulation. + +Shared buffers 14000 +Number of records: 100 in one table, continously updated+log table continously +inserted +Throughput 200tps. + + HTH + + Shridhar + + +From pgsql-performance-owner@postgresql.org Tue Dec 17 08:25:54 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 20EAD475AE4 + for ; + Tue, 17 Dec 2002 08:25:52 -0500 (EST) +Received: from smtp.inphact.com (smtp.inphact.com [67.105.52.11]) + by postgresql.org (Postfix) with ESMTP id 52040475AAC + for ; + Tue, 17 Dec 2002 08:25:50 -0500 (EST) +Received: from cafes.net (unknown [192.168.109.38]) + by smtp.inphact.com (Postfix) with ESMTP id 763E5134002 + for ; + Tue, 17 Dec 2002 07:12:15 -0600 (CST) +Date: Tue, 17 Dec 2002 07:29:48 -0600 +Subject: Re: Profiling +Content-Type: multipart/mixed; boundary=Apple-Mail-6--452436910 +Mime-Version: 1.0 (Apple Message framework v548) +From: Cory 'G' Watson +To: pgsql-performance@postgresql.org +In-Reply-To: <200212171227.07258.shridhar_daithankar@persistent.co.in> +Message-Id: <9D71C94A-11C3-11D7-8929-0003939CCA58@cafes.net> +X-Mailer: Apple Mail (2.548) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/176 +X-Sequence-Number: 592 + +--Apple-Mail-6--452436910 +Content-Transfer-Encoding: 7bit +Content-Type: text/plain; + charset=US-ASCII; + format=flowed + + +On Tuesday, December 17, 2002, at 12:57 AM, Shridhar Daithankar wrote: + +> On Tuesday 17 December 2002 09:33 am, you wrote: +>> Folks, +>> +>> I had a request from one of the SF-PUG members that I found +>> interesting. She suggested that we post the specs of some of the +>> PostgreSQL servers that we administrate, their statistics, and some +>> comments on how they perform. I'll start it off with an example: +> + +My take: + +Dual PIII-1.12Ghz, 3Gb, 5 x 36 RAID 5'ed with a spare, RedHat 7.2, Pg +7.3 + +pgbench, default settings, 252tps inc. connex, 409tps excluding connex + +Day to day, runs a monitoring/historical analysis tool of my design +with gathers metrics from around 30 hosts (they report every 10 +minutes, by their clock). Has 3,689,652 rows as of right now in the +'metrics' table, which is indexed by timestamp. + +My 'main' query is in the form of: + +SELECT timestamp, data FROM metrics WHERE resgroupid=? and hostid=? AND +timestamp BETWEEN ? AND ? ORDER BY timestamp + +Index is on timestamp. + +This query generally takes about half a second for 24 hours worth of +data. I just ran a 240 hour query on a test database with about 20,000 +rows and the result too 2998ms. + +Things slowed to a crawl about 2 weeks ago, so I upgraded to 7.3 and +saw a huge improvement. I believe part of this might have been due to +the recreation of the database, similar to a CLUSTER. My performance +is not degrading from a time perspective, but CPU usage is steadily +degrading. User time is steadily increasing over the last 240 hours, +from 5% to 15%. Attached is output of my monitoring program (well, the +new improved Java version) showing the CPU performance over the last +240 hours. + +shared_buffers = 98304 +sort_mem = 1600 +fsync = false + +Everything else is default, recommendations welcome. ;) + + +--Apple-Mail-6--452436910 +Content-Disposition: inline; + filename=cpu.png +Content-Transfer-Encoding: base64 +Content-Type: image/png; + x-unix-mode=0644; + name="cpu.png" + +iVBORw0KGgoAAAANSUhEUgAABBMAAAILCAIAAAA18UPGAABwTklEQVR42uy9 +DXRUVZrvHWLlarc6ijpGEJAvbeW2grYaVDQZ8SMMjkkn8qHihTHo4nrhYmNY +MRNsbJzmY1DEJUgTBEOTGARCiimVFjokeaGbdzWX8UXpoX31ruDIXU1f1vsy +6+XeYa3ba93z7sNT7Np1zqnPVFXq47fXs/baOTl16tQvdU6e/3meZ++i3x78 +LYZhGIZhGIZhWHQrAgGGYRiGYRiGYSgHDMMwDMMwDMNQDhiGYRiGYRiGoRww +DMMwDMMwDEM5YBiGYRiGYRiGcsAwDMMwDMMwDOWAYRiGYRiGYRjKAcMwDMMw +DMMwDOWAYRiGxfz3cLGBAsMwDEM5YBiGpd4O9R5qWNxQ/lD597//fZ/Pd+ml +l44dO3b6tOlb3t/i8MilqR3GjB4zZ/acnq6e6C57TD8+6Rd6vjaeLYgWDMMw +lAOGYRiWjHV2dI68aaQpDEpKSpR+MP3goght6pSpmVEOD056cMSIEd+77HvZ 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+SA4A+iA5SEIw9OeP+pSLiwuPx6POCjMzMzJFBYPBQqGgrORyOfmxUqnob2aQ +50Sj0aOjI32ouL6+ljPZ2NhQv8D91jtHZZ8+n082lJWzs7NYLCYno94nql/R +H9RwopIT1t/S3ZPkcHJi3O/fv/96momey0skp9ntdjlz9YZd2UMgEFC+dv/q +5Vu+/8VG0fDX/VfjVzfNV/5o4Pf71ZuY6/X66Ojow8OD4btgyT6THACSA4A+ +SA4f9f8XaboymUxTFNGvfLr64D23dv9NNF9Cxfr6el/1meQAkBwAkBwMSrll +8wOWw+GQc/P7/eon7vqVT1oftuf90H8TzV9eXi6Xy33VZ5IDQHIAQHKgKIoi +OQAgOQB9nBwoiqJ6W/zTCpAcAAAAAIDkAAAAAOAt/gO7wyTxouBoqgAAAABJ +RU5ErkJggg== + +--Apple-Mail-6--452436910 +Content-Transfer-Encoding: 7bit +Content-Type: text/plain; + charset=US-ASCII; + format=flowed + + + +Cory 'G' Watson + +--Apple-Mail-6--452436910-- + + +From pgsql-performance-owner@postgresql.org Tue Dec 17 08:26:29 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 7D122475AAC + for ; + Tue, 17 Dec 2002 08:26:25 -0500 (EST) +Received: from smtp.inphact.com (smtp.inphact.com [67.105.52.11]) + by postgresql.org (Postfix) with ESMTP id D20F54766E3 + for ; + Tue, 17 Dec 2002 08:26:13 -0500 (EST) +Received: from cafes.net (unknown [192.168.109.38]) + by smtp.inphact.com (Postfix) with ESMTP id ECE93134002 + for ; + Tue, 17 Dec 2002 07:12:39 -0600 (CST) +Date: Tue, 17 Dec 2002 07:30:13 -0600 +Subject: Re: Profiling +Content-Type: multipart/mixed; boundary=Apple-Mail-8--452412343 +Mime-Version: 1.0 (Apple Message framework v548) +From: Cory 'G' Watson +To: pgsql-performance@postgresql.org +In-Reply-To: <200212171227.07258.shridhar_daithankar@persistent.co.in> +Message-Id: +X-Mailer: Apple Mail (2.548) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/177 +X-Sequence-Number: 593 + +--Apple-Mail-8--452412343 +Content-Transfer-Encoding: 7bit +Content-Type: text/plain; + charset=US-ASCII; + format=flowed + + +On Tuesday, December 17, 2002, at 12:57 AM, Shridhar Daithankar wrote: + +> On Tuesday 17 December 2002 09:33 am, you wrote: +>> Folks, +>> +>> I had a request from one of the SF-PUG members that I found +>> interesting. She suggested that we post the specs of some of the +>> PostgreSQL servers that we administrate, their statistics, and some +>> comments on how they perform. I'll start it off with an example: +> + +My take: + +Dual PIII-1.12Ghz, 3Gb, 5 x 36 RAID 5'ed with a spare, RedHat 7.2, Pg +7.3 + +pgbench, default settings, 252tps inc. connex, 409tps excluding connex + +Day to day, runs a monitoring/historical analysis tool of my design +with gathers metrics from around 30 hosts (they report every 10 +minutes, by their clock). Has 3,689,652 rows as of right now in the +'metrics' table, which is indexed by timestamp. + +My 'main' query is in the form of: + +SELECT timestamp, data FROM metrics WHERE resgroupid=? and hostid=? AND +timestamp BETWEEN ? AND ? ORDER BY timestamp + +Index is on timestamp. + +This query generally takes about half a second for 24 hours worth of +data. I just ran a 240 hour query on a test database with about 20,000 +rows and the result too 2998ms. + +Things slowed to a crawl about 2 weeks ago, so I upgraded to 7.3 and +saw a huge improvement. I believe part of this might have been due to +the recreation of the database, similar to a CLUSTER. My performance +is not degrading from a time perspective, but CPU usage is steadily +degrading. User time is steadily increasing over the last 240 hours, +from 5% to 15%. Attached is output of my monitoring program (well, the +new improved Java version) showing the CPU performance over the last +240 hours. + +shared_buffers = 98304 +sort_mem = 1600 +fsync = false + +Everything else is default, recommendations welcome. ;) + + +--Apple-Mail-8--452412343 +Content-Disposition: inline; + filename=cpu.png +Content-Transfer-Encoding: base64 +Content-Type: image/png; + x-unix-mode=0644; + name="cpu.png" + +iVBORw0KGgoAAAANSUhEUgAABBMAAAILCAIAAAA18UPGAABwTklEQVR42uy9 +DXRUVZrvHWLlarc6ijpGEJAvbeW2grYaVDQZ8SMMjkkn8qHihTHo4nrhYmNY +MRNsbJzmY1DEJUgTBEOTGARCiimVFjokeaGbdzWX8UXpoX31ruDIXU1f1vsy +6+XeYa3ba93z7sNT7Np1zqnPVFXq47fXs/baOTl16tQvdU6e/3meZ++i3x78 +LYZhGIZhGIZhWHQrAgGGYRiGYRiGYSgHDMMwDMMwDMNQDhiGYRiGYRiGoRww +DMMwDMMwDEM5YBiGYRiGYRiGcsAwDMMwDMMwDOWAYRiGYRiGYRjKAcMwDMMw +DMMwDOWAYRiGxfz3cLGBAsMwDEM5YBiGpd4O9R5qWNxQ/lD597//fZ/Pd+ml +l44dO3b6tOlb3t/i8MilqR3GjB4zZ/acnq6e6C57TD8+6Rd6vjaeLYgWDMMw +lAOGYRiWjHV2dI68aaQpDEpKSpR+MP3goght6pSpmVEOD056cMSIEd+77HvZ 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+SA4A+iA5SEIw9OeP+pSLiwuPx6POCjMzMzJFBYPBQqGgrORyOfmxUqnob2aQ +50Sj0aOjI32ouL6+ljPZ2NhQv8D91jtHZZ8+n082lJWzs7NYLCYno94nql/R +H9RwopIT1t/S3ZPkcHJi3O/fv/96momey0skp9ntdjlz9YZd2UMgEFC+dv/q +5Vu+/8VG0fDX/VfjVzfNV/5o4Pf71ZuY6/X66Ojow8OD4btgyT6THACSA4A+ +SA4f9f8XaboymUxTFNGvfLr64D23dv9NNF9Cxfr6el/1meQAkBwAkBwMSrll +8wOWw+GQc/P7/eon7vqVT1oftuf90H8TzV9eXi6Xy33VZ5IDQHIAQHKgKIoi +OQAgOQB9nBwoiqJ6W/zTCpAcAAAAAIDkAAAAAOAt/gO7wyTxouBoqgAAAABJ +RU5ErkJggg== + +--Apple-Mail-8--452412343 +Content-Transfer-Encoding: 7bit +Content-Type: text/plain; + charset=US-ASCII; + format=flowed + + + +Cory 'G' Watson + +--Apple-Mail-8--452412343-- + + +From pgsql-performance-owner@postgresql.org Tue Dec 17 08:36:29 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EBCA14768AB + for ; + Tue, 17 Dec 2002 08:36:26 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id DBDEA476866 + for ; + Tue, 17 Dec 2002 08:35:16 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id gBHDZGK09636 + for ; Tue, 17 Dec 2002 19:05:16 +0530 +Received: from daithan.itnranet.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 gBHDZG009631 + for ; Tue, 17 Dec 2002 19:05:16 +0530 +Content-Type: text/plain; + charset="iso-8859-1" +From: Shridhar Daithankar +To: pgsql-performance@postgresql.org +Subject: Re: Profiling +Date: Tue, 17 Dec 2002 19:05:41 +0530 +User-Agent: KMail/1.4.3 +References: <9D71C94A-11C3-11D7-8929-0003939CCA58@cafes.net> +In-Reply-To: <9D71C94A-11C3-11D7-8929-0003939CCA58@cafes.net> +MIME-Version: 1.0 +Message-Id: <200212171905.41759.shridhar_daithankar@persistent.co.in> +Content-Transfer-Encoding: 8bit +X-MIME-Autoconverted: from quoted-printable to 8bit by www.pspl.co.in id + gBHDZG009631 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/178 +X-Sequence-Number: 594 + +On Tuesday 17 December 2002 06:59 pm, you wrote: +> shared_buffers = 98304 +> sort_mem = 1600 +> fsync = false +> +> Everything else is default, recommendations welcome. ;) + +What is the vacuum frequency? + + Shridhar + + +From pgsql-performance-owner@postgresql.org Tue Dec 17 08:39:31 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D5DDC475AE4 + for ; + Tue, 17 Dec 2002 08:39:29 -0500 (EST) +Received: from smtp.inphact.com (smtp.inphact.com [67.105.52.11]) + by postgresql.org (Postfix) with ESMTP id 5D1FE475AAC + for ; + Tue, 17 Dec 2002 08:39:29 -0500 (EST) +Received: from cafes.net (unknown [192.168.109.38]) + by smtp.inphact.com (Postfix) with ESMTP + id E0C57134002; Tue, 17 Dec 2002 07:25:55 -0600 (CST) +Date: Tue, 17 Dec 2002 07:43:28 -0600 +Subject: Re: Profiling +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v548) +Cc: pgsql-performance@postgresql.org +To: Shridhar Daithankar +From: Cory 'G' Watson +In-Reply-To: <200212171905.41759.shridhar_daithankar@persistent.co.in> +Message-Id: <861F40A0-11C5-11D7-8929-0003939CCA58@cafes.net> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.548) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/179 +X-Sequence-Number: 595 + + +On Tuesday, December 17, 2002, at 07:35 AM, Shridhar Daithankar wrote: + +> On Tuesday 17 December 2002 06:59 pm, you wrote: +>> shared_buffers = 98304 +>> sort_mem = 1600 +>> fsync = false +>> +>> Everything else is default, recommendations welcome. ;) +> +> What is the vacuum frequency? + +Every morning. This db is almost exclusively INSERT and SELECT. Well, +I take that back, a single table gets UPDATEs rather frequently. +Otherwise, INSERT only. + +Cory 'G' Watson + + +From pgsql-performance-owner@postgresql.org Tue Dec 17 08:49:08 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 57E0F475DD0 + for ; + Tue, 17 Dec 2002 08:49:07 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 40FFF475AE4 + for ; + Tue, 17 Dec 2002 08:49:05 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id gBHDn8q10992 + for ; Tue, 17 Dec 2002 19:19:08 +0530 +Received: from daithan.itnranet.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 gBHDn7010987 + for ; Tue, 17 Dec 2002 19:19:07 +0530 +Content-Type: text/plain; + charset="iso-8859-1" +From: Shridhar Daithankar +To: pgsql-performance@postgresql.org +Subject: Re: Profiling +Date: Tue, 17 Dec 2002 19:19:33 +0530 +User-Agent: KMail/1.4.3 +References: <861F40A0-11C5-11D7-8929-0003939CCA58@cafes.net> +In-Reply-To: <861F40A0-11C5-11D7-8929-0003939CCA58@cafes.net> +MIME-Version: 1.0 +Message-Id: <200212171919.33174.shridhar_daithankar@persistent.co.in> +Content-Transfer-Encoding: 8bit +X-MIME-Autoconverted: from quoted-printable to 8bit by www.pspl.co.in id + gBHDn7010987 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/180 +X-Sequence-Number: 596 + +On Tuesday 17 December 2002 07:13 pm, you wrote: +> On Tuesday, December 17, 2002, at 07:35 AM, Shridhar Daithankar wrote: +> > What is the vacuum frequency? +> +> Every morning. This db is almost exclusively INSERT and SELECT. Well, +> I take that back, a single table gets UPDATEs rather frequently. +> Otherwise, INSERT only. + +i recommend a vacuum analyze per 1000/2000 records for the table that gets +updated. It should boost the performance like anything.. + + Shridhar + +From pgsql-performance-owner@postgresql.org Tue Dec 17 09:17:19 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0075947629D + for ; + Tue, 17 Dec 2002 09:17:19 -0500 (EST) +Received: from smtp.inphact.com (smtp.inphact.com [67.105.52.11]) + by postgresql.org (Postfix) with ESMTP id 1DB84476243 + for ; + Tue, 17 Dec 2002 09:16:21 -0500 (EST) +Received: from cafes.net (unknown [192.168.109.38]) + by smtp.inphact.com (Postfix) with ESMTP + id E00E0134002; Tue, 17 Dec 2002 08:02:47 -0600 (CST) +Date: Tue, 17 Dec 2002 08:20:21 -0600 +Subject: Re: Profiling +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v548) +Cc: pgsql-performance@postgresql.org +To: Shridhar Daithankar +From: Cory 'G' Watson +In-Reply-To: <200212171919.33174.shridhar_daithankar@persistent.co.in> +Message-Id: +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.548) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/181 +X-Sequence-Number: 597 + + +On Tuesday, December 17, 2002, at 07:49 AM, Shridhar Daithankar wrote: + +> On Tuesday 17 December 2002 07:13 pm, you wrote: +>> On Tuesday, December 17, 2002, at 07:35 AM, Shridhar Daithankar wrote: +>>> What is the vacuum frequency? +>> +>> Every morning. This db is almost exclusively INSERT and SELECT. +>> Well, +>> I take that back, a single table gets UPDATEs rather frequently. +>> Otherwise, INSERT only. +> +> i recommend a vacuum analyze per 1000/2000 records for the table that +> gets +> updated. It should boost the performance like anything.. + +By my math, I'll need to vacuum once every hour or so. Cron, here I +come. + +vacuumdb --table cached_metrics loggerithim + +I assume I do not need a --analyze, since that table has no indexes. +Should I vacuum the entire DB? + +Any other settings I should look at? Note that I'm not necessarily +having any problems at present, but one can always tune. This DB is +used with a web app (mod_perl/DBI) at the moment, but is moving to a +Java Swing client, which will give me much more data about performance. + +Cory 'G' Watson + + +From pgsql-performance-owner@postgresql.org Tue Dec 17 09:29:16 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 01F2D476855 + for ; + Tue, 17 Dec 2002 09:29:16 -0500 (EST) +Received: from www.pspl.co.in (www.pspl.co.in [202.54.11.65]) + by postgresql.org (Postfix) with ESMTP id 4F46047684A + for ; + Tue, 17 Dec 2002 09:29:14 -0500 (EST) +Received: (from root@localhost) + by www.pspl.co.in (8.11.6/8.11.6) id gBHETHe14332 + for ; Tue, 17 Dec 2002 19:59:17 +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 gBHETH014327 + for ; Tue, 17 Dec 2002 19:59:17 +0530 +From: "Shridhar Daithankar" +To: pgsql-performance@postgresql.org +Date: Tue, 17 Dec 2002 19:59:42 +0530 +MIME-Version: 1.0 +Subject: Re: Profiling +Reply-To: shridhar_daithankar@persistent.co.in +Message-ID: <3DFF822E.3862.23CE04@localhost> +References: <200212171919.33174.shridhar_daithankar@persistent.co.in> +In-reply-to: +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: 200212/182 +X-Sequence-Number: 598 + +On 17 Dec 2002 at 8:20, Cory 'G' Watson wrote: +> By my math, I'll need to vacuum once every hour or so. Cron, here I +> come. +> +> vacuumdb --table cached_metrics loggerithim + +http://gborg.postgresql.org/project/pgavd/projdisplay.php + +Yeah, yeah.. I wrote that..and use CVS as usual. No release as yet.. + + +> I assume I do not need a --analyze, since that table has no indexes. +> Should I vacuum the entire DB? + +You need analyse to keep vacuum non-locking I assume. And there is no need to +vacuum entire DB. + +HTH + +Bye + Shridhar + +-- +paycheck: The weekly $5.27 that remains after deductions for federal +withholding, state withholding, city withholding, FICA, medical/dental, long- +term disability, unemployment insurance, Christmas Club, and payroll savings +plan contributions. + + +From pgsql-performance-owner@postgresql.org Tue Dec 17 09:49:26 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id E2F3C475AE6 + for ; + Tue, 17 Dec 2002 09:49:24 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 450ED475AAC + for ; + Tue, 17 Dec 2002 09:49:24 -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 gBHEnHpd006742; + Tue, 17 Dec 2002 09:49:17 -0500 (EST) +To: "Cory 'G' Watson" +Cc: Shridhar Daithankar , + pgsql-performance@postgresql.org +Subject: Re: Profiling +In-reply-to: +References: +Comments: In-reply-to "Cory 'G' Watson" + message dated "Tue, 17 Dec 2002 08:20:21 -0600" +Date: Tue, 17 Dec 2002 09:49:16 -0500 +Message-ID: <6741.1040136556@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/183 +X-Sequence-Number: 599 + +"Cory 'G' Watson" writes: +> I assume I do not need a --analyze, since that table has no indexes. + +Whether you need analyze or not has nothing to do with whether there +are indexes. You probably don't need it once an hour, but maybe once +a day would be good. + +> Should I vacuum the entire DB? + +Overkill; just get the heavily-updated table(s). A DB-wide vacuum must +be done occasionally, but again once-a-day would be plenty. + +> Any other settings I should look at? + +Free space map (fsm) settings must be adequate to keep track of the free +space in your tables. + +However, all of this relates only to keeping performance good on the +table with lots of updates. If you are seeing progressive degradation +on a table that only gets INSERTs, then there's something else going on. +AFAIR you didn't show us an EXPLAIN ANALYZE for the principal query? + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Tue Dec 17 11:23:38 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1EA1D47626B + for ; + Tue, 17 Dec 2002 11:23:37 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id 33528476247 + for ; + Tue, 17 Dec 2002 11:23:36 -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 gBHGMuI4008911 + for ; + Tue, 17 Dec 2002 09:22:56 -0700 (MST) +Date: Tue, 17 Dec 2002 09:18:02 -0700 (MST) +From: "scott.marlowe" +To: +Subject: Re: Profiling +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: 200212/184 +X-Sequence-Number: 600 + +OK, my turn. + +We have two main servers that are identical, one is the online server, the +other is the hot spare. Their specs: + +Dual PIII-750 1.5 Gig ram and dual 18 Gig 10krpm UW SCSI drives. +OS on one drive, postgresql on the other. + +Interesting postgresql.conf entries: + +max_connections = 128 +shared_buffers = 32768 +max_fsm_relations = 10000 +sort_mem = 2048 +vacuum_mem = 8192 +cpu_tuple_cost = 0.01 +cpu_index_tuple_cost = 0.0001 +cpu_operator_cost = 0.05 + +pgbench -c 4 -t 200 delivers about 240 tps. + +Performance is outstanding. This machine runs apache, OpenLDAP, Real +Server 1, as well as Postgresql. All non-database data is stored on a +NAS, so the local drives are only used for swap and postgresql. Average +load is about 40 to 200 reads per minute, with only a handful of writes +per minute (1 to 5 max). Most data is loaded from nightly runs out of +the mainframe and a few other systems for things like company phonebook +and ldap. + +My test servers: + +Server A: Dual PPro 200 with 256 Meg RAM and 6x4Gig 10kRPM UW SCSI drives +(3 quantum, 3 seagate) and 2x80Gig 7200 RPM IDE drives. + +Data is generally stored on the pair of 80 gig drives, because the 4 gig +scsis just aren't big enough. The 80 gig ides are setup as two 40 gig +mirrors (i.e. they're split in half) with the other half used to store +backups and such. + +shared_buffers = 5000 + +pgbench -c 4 -t 200 yields about 80 tps. + +Performance is actually quite good, and this is a box we bought in 1997. + +Server B: (My workstation) Celeron 1.1GHz, with 512 MEg RAM and a 40 gig +IDE @7200 RPM, and a 17 Gig IDE @5400 RPM. + +shared_buffers = 4096 + +pgbench -c 4 -t 200 yields about 75 tps. Yes, my dual PPro 200 outruns +this box. But then again, my workstation has KDE up and running with +Mozilla, xmms mp3 player going, and a couple other programs running as +well. + +All of these boxes are / were heavily tested before deployment, and we +have never had a problem with postgresql on any of them. + + +From pgsql-performance-owner@postgresql.org Thu Dec 19 05:09:33 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B0666476D7B + for ; + Thu, 19 Dec 2002 05:09:32 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 55F9847629D + for ; + Thu, 19 Dec 2002 05:09:19 -0500 (EST) +Received: from klaster.net (ph56.krakow.cvx.ppp.tpnet.pl [217.99.208.56]) + by serwer.skawsoft.com.pl (Postfix) with ESMTP id 218932B854 + for ; + Thu, 19 Dec 2002 10:52:50 +0100 (CET) +Message-ID: <3E019B71.5050901@klaster.net> +Date: Thu, 19 Dec 2002 11:12:01 +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: EXISTS vs IN vs OUTER JOINS +Content-Type: text/plain; charset=us-ascii; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/185 +X-Sequence-Number: 601 + +Hi +Few days ago I read, that EXISTS is better than IN, but only if there +are many records (how many?). I was wondering which one is better and +when. Did anyone try to compare these queries doing the same work: + +- select * from some_table t + where t.id [not] in (select id from filter); +- select * from some_table t + where [not] exists (select * from filter where id=t.id); +- select * from some_table t + left join filter f using (id) + where f.id is [not] null; + +Regards, +Tomasz Myrta + + +From pgsql-performance-owner@postgresql.org Thu Dec 19 12:16:36 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A415B476FBE + for ; + Thu, 19 Dec 2002 12:16:33 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 262DD476FEB + for ; + Thu, 19 Dec 2002 12:15:38 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2291801; Thu, 19 Dec 2002 09:15:36 -0800 +From: "Josh Berkus" +Subject: Re: EXISTS vs IN vs OUTER JOINS +To: Tomasz Myrta , + PgSQL Performance ML +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Thu, 19 Dec 2002 09:15:36 -0800 +Message-ID: +In-Reply-To: <3E019B71.5050901@klaster.net> +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: 200212/186 +X-Sequence-Number: 602 + +Tomasz, + +> Few days ago I read, that EXISTS is better than IN, but only if there +> are many records (how many?). I was wondering which one is better and +> when. Did anyone try to compare these queries doing the same work: +> +> - select * from some_table t +> where t.id [not] in (select id from filter); +> -select * from some_table t +> where [not] exists (select * from filter where id=t.id); + +The rule I use is: if I expect the sub-select to return more than 12 +records 20% or more of the time, use EXISTS. The speed gain for IN on +small lists is not as dramatic as the speed loss for EXISTS on large +lists. + +More importantly, the difference between NOT IN and NOT EXISTS can be +as much as 20:1 on large sub-selects, as opposed to IN and EXISTS, +where I have rarely seen a difference of more than 3:1. As I +understand it, this is because NOT EXISTS can use optimized join +algorithms to locate matching rows, whereas NOT IN must compare each +row against every possible matching value in the subselect. + +It also makes a difference whether or not the referenced field(s) in +the subselect is indexed. EXISTS will often use an index to compare +the values in the master query to the sub-query. As far as I know, IN +can use an index to retrieve the subquery values, but not to sort or +compare them after they have been retreived into memory. + +> -select * from some_table t +> left join filter f using (id) +> where f.id is [not] null; + +This will not get you the same result as the above. It will get you +all rows from t+f where a record is present in f and has (or does not +have) a NULL value for f.id. While this type of query works in MS +Access, it will not work in SQL92/99-commpliant databases. + +Incidentally, the dramatic differences between IN and EXISTS are not +only a "PostgreSQL Thing". The same rules apply to MS SQL Server and +SQL Anywhere, for the same reasons. + +-Josh Berkus + + +From pgsql-performance-owner@postgresql.org Thu Dec 19 12:47:46 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 096464770CD + for ; + Thu, 19 Dec 2002 12:47:44 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id E177A476FC4 + for ; + Thu, 19 Dec 2002 12:44:03 -0500 (EST) +Received: by serwer.skawsoft.com.pl (Postfix, from userid 1000) + id CDC2F2B85D; Thu, 19 Dec 2002 18:27:33 +0100 (CET) +Date: Thu, 19 Dec 2002 18:27:33 +0100 +To: Josh Berkus +Cc: Tomasz Myrta , + PgSQL Performance ML +Subject: Re: EXISTS vs IN vs OUTER JOINS +Message-ID: <20021219172733.GA1001@serwer> +References: <3E019B71.5050901@klaster.net> + +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: +User-Agent: Mutt/1.3.28i +From: jasiek@klaster.net +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/187 +X-Sequence-Number: 603 + +On Thu, Dec 19, 2002 at 09:15:36AM -0800, Josh Berkus wrote: +> > -select * from some_table t +> > left join filter f using (id) +> > where f.id is [not] null; +> +> This will not get you the same result as the above. It will get you +> all rows from t+f where a record is present in f and has (or does not +> have) a NULL value for f.id. While this type of query works in MS +> Access, it will not work in SQL92/99-commpliant databases. + +filter_table does not contain null fields. It has only two states: it +has row +or it hasn't row coresponding to row in some_table. + +And now, which one is better? + +Tomasz Myrta + +From pgsql-performance-owner@postgresql.org Thu Dec 19 12:48:28 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CF5DC4770C8 + for ; + Thu, 19 Dec 2002 12:48:27 -0500 (EST) +Received: from joeconway.com (unknown [63.210.180.150]) + by postgresql.org (Postfix) with ESMTP id C29BA4762C1 + for ; + Thu, 19 Dec 2002 12:44:56 -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 1489143; Thu, 19 Dec 2002 10:24:30 -0800 +Message-ID: <3E02053C.7070305@joeconway.com> +Date: Thu, 19 Dec 2002 09:43:24 -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: Josh Berkus +Cc: Tomasz Myrta , + PgSQL Performance ML +Subject: Re: EXISTS vs IN vs OUTER JOINS +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: 200212/188 +X-Sequence-Number: 604 + +Josh Berkus wrote: +> where I have rarely seen a difference of more than 3:1. As I +> understand it, this is because NOT EXISTS can use optimized join +> algorithms to locate matching rows, whereas NOT IN must compare each +> row against every possible matching value in the subselect. +> +> It also makes a difference whether or not the referenced field(s) in +> the subselect is indexed. EXISTS will often use an index to compare +> the values in the master query to the sub-query. As far as I know, IN +> can use an index to retrieve the subquery values, but not to sort or +> compare them after they have been retreived into memory. + +I wonder if "[NOT] IN (subselect)" could be improved with a hash table in +similar fashion to the hash aggregate solution Tom recently implemented? + +Joe + + + +From pgsql-performance-owner@postgresql.org Thu Dec 19 13:58:40 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 74A41475DB3 + for ; + Thu, 19 Dec 2002 13:58:39 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 60D11475C2B + for ; + Thu, 19 Dec 2002 13:58:38 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2291948; Thu, 19 Dec 2002 10:58:30 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: jasiek@klaster.net +Subject: Re: EXISTS vs IN vs OUTER JOINS +Date: Thu, 19 Dec 2002 11:02:39 -0800 +X-Mailer: KMail [version 1.4] +Cc: Tomasz Myrta , + PgSQL Performance ML +References: <3E019B71.5050901@klaster.net> + + <20021219172733.GA1001@serwer> +In-Reply-To: <20021219172733.GA1001@serwer> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212191102.39785.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/190 +X-Sequence-Number: 606 + + +Tomasz, + +> > This will not get you the same result as the above. It will get you +> > all rows from t+f where a record is present in f and has (or does not +> > have) a NULL value for f.id. While this type of query works in MS +> > Access, it will not work in SQL92/99-commpliant databases. +>=20 +> filter_table does not contain null fields. It has only two states: it +> has row +> or it hasn't row coresponding to row in some_table. +>=20 +> And now, which one is better? + +You're not listening. I said that LEFT JOIN won't work. At all. + +Please re-read the paragraph above, which explains why. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Thu Dec 19 14:08:09 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C232E4770A3 + for ; + Thu, 19 Dec 2002 14:08:08 -0500 (EST) +Received: from email04.aon.at (WARSL402PIP5.highway.telekom.at [195.3.96.79]) + by postgresql.org (Postfix) with SMTP id E55BB47705E + for ; + Thu, 19 Dec 2002 14:07:37 -0500 (EST) +Received: (qmail 335746 invoked from network); 19 Dec 2002 19:07:37 -0000 +Received: from m150p028.dipool.highway.telekom.at (HELO cantor) + ([62.46.8.188]) (envelope-sender ) + by qmail5rs.highway.telekom.at (qmail-ldap-1.03) with SMTP + for ; 19 Dec 2002 19:07:37 -0000 +From: Manfred Koizar +To: gry@ll.mit.edu +Cc: pgsql-performance@postgresql.org +Subject: Re: 4G row table? +Date: Thu, 19 Dec 2002 20:07:53 +0100 +Message-ID: +References: <20021219141058.11d4b693.gry@ll.mit.edu> +In-Reply-To: <20021219141058.11d4b693.gry@ll.mit.edu> +X-Mailer: Forte Agent 1.8/32.548 +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: 200212/191 +X-Sequence-Number: 607 + +On Thu, 19 Dec 2002 14:10:58 -0500, george young +wrote: +>with 4 billion(4e9) rows. I would guess to make wafer, die_row, etc. be of +>type "char", probably testtype a char too with a separate testtype lookup table. +>Even so, this will be a huge table. + +Don't know if you can store 0-127 in a "char" column ... Anyway, it +doesn't matter, if it does not cause the tuple size to cross a 4 byte +boundary, because the tuple size will be rounded up to a multiple of +4. + +>Questions: How much overhead will there be in the table in addition to the +>9 bytes of data I see? + +There is a page header (ca. 20 bytes) per page (8K by default). Then +you have a tuple header and 4 bytes ItemIdData per tuple. + +PG 7.2: Without NULLs a tuple header is 32 bytes, add 4 bytes for each +tuple containing at least one NULL column. + +PG 7.3: 24 bytes tuple header (with and without NULLs, because you +have only 8 columns). + +>How big will the primary index on the first seven columns be? + +Don't know offhand. No time now to dig it out. Will answer tomorrow, +if nobody else jumps in ... + +Servus + Manfred + +From pgsql-performance-owner@postgresql.org Thu Dec 19 13:16:47 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C65A2476CA2 + for ; + Thu, 19 Dec 2002 13:16:45 -0500 (EST) +Received: from ll.mit.edu (LLMAIL.LL.MIT.EDU [129.55.12.40]) + by postgresql.org (Postfix) with ESMTP id C315D476FE2 + for ; + Thu, 19 Dec 2002 13:11:30 -0500 (EST) +Received: (from smtp@localhost) by ll.mit.edu (8.11.3/8.8.8) id gBJIBTZ22588 + for ; + Thu, 19 Dec 2002 13:11:29 -0500 (EST) +Received: from sty.llan.ll.mit.edu( ), claiming to be "sty.llan" + via SMTP by llpost, id smtpdAAAfTaWgJ; Thu Dec 19 13:10:56 2002 +Date: Thu, 19 Dec 2002 14:10:58 -0500 +From: george young +To: pgsql-performance@postgresql.org +Subject: 4G row table? +Message-Id: <20021219141058.11d4b693.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: 200212/189 +X-Sequence-Number: 605 + +[linux, 700MHz athlon, 512MB RAM, 700GB 10kRPM SCSI HW RAID, postgresql 7.2] +We're setting up a DB of IC test data, which is very simple and regular, but large. +One project (we get three or four per year) has ~4 giga bits, each specified by +a few small integer values, e.g.: + Name Type Values + ---------------------- + wafer int 1-50 + die_row int 2-7 + die_col int 2-7 + testtype string (~10 different short strings) + vdd int 0-25 + bit_col int 0-127 + bit_row int 0-511 + value bit 0 or 1 + +with 4 billion(4e9) rows. I would guess to make wafer, die_row, etc. be of +type "char", probably testtype a char too with a separate testtype lookup table. +Even so, this will be a huge table. + +Questions: How much overhead will there be in the table in addition to the +9 bytes of data I see? How big will the primary index on the first seven columns +be? Will this schema work at all? + +Of course, we could pack 128 bits into an 8 byte "text" field (or should we use bit(128)?), +but lose some ease of use, especially for naive (but important) users. + +Comments, suggestions? + +-- George + +-- + 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 Dec 19 14:11:19 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id F3ACE47590C + for ; + Thu, 19 Dec 2002 14:11:18 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 44913475C45 + for ; + Thu, 19 Dec 2002 14:11:18 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2291962; Thu, 19 Dec 2002 11:11:11 -0800 +Content-Type: text/plain; + charset="iso-8859-1" +From: Josh Berkus +Reply-To: josh@agliodbs.com +Organization: Aglio Database Solutions +To: gry@ll.mit.edu, pgsql-performance@postgresql.org +Subject: Re: 4G row table? +Date: Thu, 19 Dec 2002 11:15:20 -0800 +X-Mailer: KMail [version 1.4] +References: <20021219141058.11d4b693.gry@ll.mit.edu> +In-Reply-To: <20021219141058.11d4b693.gry@ll.mit.edu> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212191115.20391.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/192 +X-Sequence-Number: 608 + +George, + +> [linux, 700MHz athlon, 512MB RAM, 700GB 10kRPM SCSI HW RAID, postgresql 7= +.2] + +What kind of RAID? How many drives? Will you be updating the data=20 +frequently, or mostly just running reports on it? + +With 4G rows, you will have *heavy* disk access, so the configuration and= +=20 +quality of your disk array is a big concern. You also might think about= +=20 +upping th ememory if you can. + +> We're setting up a DB of IC test data, which is very simple and regular, = +but=20 +large. +> One project (we get three or four per year) has ~4 giga bits, each specif= +ied=20 +by +> a few small integer values, e.g.: +> Name Type Values +> ---------------------- +> wafer int 1-50 +> die_row int 2-7 +> die_col int 2-7 +> testtype string (~10 different short strings) +> vdd int 0-25 +> bit_col int 0-127 +> bit_row int 0-511 +> value bit 0 or 1 +>=20 +> with 4 billion(4e9) rows. I would guess to make wafer, die_row, etc. be = +of +> type "char", probably testtype a char too with a separate testtype lookup= +=20 +table. +> Even so, this will be a huge table.=20=20 + +1. Use INT2 and not INT for the INT values above. If you can hire a=20 +PostgreSQL hacker, have them design a new data type for you, an unsigned IN= +T1=20 +which will cut your storage space even further. + +2. Do not use CHAR for wafer & die-row. CHAR requries min 3bytes storage;= +=20 +INT2 is only 2 bytes. + +3. If you can use a lookup table for testtype, make it another INT2 and cre= +ate=20 +a numeric key for the lookup table. + +> Questions: How much overhead will there be in the table in addition to the +> 9 bytes of data I see?=20=20 + +There's more than 9 bytes in the above. Count again. + +> How big will the primary index on the first seven columns +> be? Will this schema work at all?=20 + +As large as the 7 columns themselves, plus a little more. I suggest creat= +ing=20 +a surrogate key as an int8 sequence to refer to most rows.=20=20 + +> Of course, we could pack 128 bits into an 8 byte "text" field (or should = +we=20 +use bit(128)?), +> but lose some ease of use, especially for naive (but important) users. + +This is also unlikely to be more efficient due to the translation<->convers= +ion=20 +process requried to access the data when you query. + +> Comments, suggestions? + +Unless you have a *really* good RAID array, expect slow performance on this= +=20 +hardware platform. + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Thu Dec 19 14:28:28 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 29428476CD4 + for ; + Thu, 19 Dec 2002 14:28:26 -0500 (EST) +Received: from clearmetrix.com (unknown [209.92.142.67]) + by postgresql.org (Postfix) with ESMTP id 078EA476067 + for ; + Thu, 19 Dec 2002 14:28:23 -0500 (EST) +Received: from clearmetrix.com (chw.muvpn.clearmetrix.com [172.16.1.3]) + by clearmetrix.com (8.11.6/linuxconf) with ESMTP id gBJJRi721356; + Thu, 19 Dec 2002 14:27:44 -0500 +Message-ID: <3E021D9D.1040608@clearmetrix.com> +Date: Thu, 19 Dec 2002 14:27:25 -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: josh@agliodbs.com +Cc: gry@ll.mit.edu, pgsql-performance@postgresql.org +Subject: Re: 4G row table? +References: <20021219141058.11d4b693.gry@ll.mit.edu> + <200212191115.20391.josh@agliodbs.com> +In-Reply-To: <200212191115.20391.josh@agliodbs.com> +Content-Type: text/plain; charset=ISO-8859-1; format=flowed +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/193 +X-Sequence-Number: 609 + +Josh: + +Why do you say to expect slow performance on this hardware? Is there +something specific about the configuration that worries you? Or, just +lots of data in the database, so the data will be on disk and not in the +cache (system or postgresql)? + +What do you classify as *slow*? Obviously, he is dependent on the I/O +channel given the size of the tables. So, good indexing will be +required to help on the queries. No comments on the commit rate for +this data (I am guessing that it is slow, given the description of the +database), so that may or may not be an issue. + +Depending on the type of queries, perhaps clustering will help, along +with some good partitioning indexes. + +I just don't see the slow in the hardware. Of course, if he is +targeting lots of concurrent queries, better add some additional +processors, or better yet, use ERSERVER and replicate the data to a farm +of machines. [To avoid the I/O bottleneck of lots of concurrent queries +against these large tables]. + +I guess there are a lot of assumptions on the data's use to decide if +the hardware is adequate or not :-) + +Charlie + + + +Josh Berkus wrote: + +>George, +> +> +>>[linux, 700MHz athlon, 512MB RAM, 700GB 10kRPM SCSI HW RAID, postgresql 7.2] +>> +>> +> +>What kind of RAID? How many drives? Will you be updating the data +>frequently, or mostly just running reports on it? +> +> +>Unless you have a *really* good RAID array, expect slow performance on this +>hardware platform. +> +> +> + +-- + + +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 Dec 19 14:45:07 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C7E4E475E7B + for ; + Thu, 19 Dec 2002 14:45:05 -0500 (EST) +Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66]) + by postgresql.org (Postfix) with ESMTP id 22533475DB3 + for ; + Thu, 19 Dec 2002 14:45:03 -0500 (EST) +Received: by serwer.skawsoft.com.pl (Postfix, from userid 1000) + id 64D882B85D; Thu, 19 Dec 2002 20:28:30 +0100 (CET) +Date: Thu, 19 Dec 2002 20:28:30 +0100 +To: Josh Berkus +Cc: jasiek@klaster.net, + PgSQL Performance ML +Subject: Re: EXISTS vs IN vs OUTER JOINS +Message-ID: <20021219192830.GA8336@serwer> +References: <3E019B71.5050901@klaster.net> + + <20021219172733.GA1001@serwer> + <200212191102.39785.josh@agliodbs.com> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <200212191102.39785.josh@agliodbs.com> +User-Agent: Mutt/1.3.28i +From: jasiek@klaster.net +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/195 +X-Sequence-Number: 611 + +On Thu, Dec 19, 2002 at 11:02:39AM -0800, Josh Berkus wrote: +> +> Tomasz, +> You're not listening. I said that LEFT JOIN won't work. At all. +> +> Please re-read the paragraph above, which explains why. +I read your mail once again, but I still don't understand what are you +talking about. +I'll write example - maybe it will help us to understand each other. + + +I have three tables: users, things and access_list +create table users( +user_id integer primary key, +username varchar +); +insert into users(1,'Tomasz'); + +create table things( +thing_id int4 primary key, +thingname varchar +); +insert into things(1,'thing1'); +insert into things(2,'thing2'); +insert into things(3,'thing3'); +insert into things(4,'thing4'); +insert into things(5,'thing5'); + +create table access_list( +user_id int4 not null references users, +thing_id int4 not null references things +); +insert into access_list(1,1); +insert into access_list(1,4); + +SELECT u.username,t.thingname,al.thing_id +from users u cross join things t +left join access_list al on (s.user_id=al.user_id and +t.thing_id=al.thing_id) + +Result: +username thingname thing_id +Tomasz thing1 1 +Tomasz thing2 +Tomasz thing3 +Tomasz thing4 4 +Tomasz thing5 5 + +Now if we add "where al.user_id is null" we get: +Tomasz thing2 +Tomasz thing3 + +Or if we add "where al.user_id is not null" we get: +(the same result we have when using inner join) +Tomasz thing1 1 +Tomasz thing4 4 +Tomasz thing5 5 + +I know this method will fail if we have not unique pairs in table +access_list, but in other case it looks ok. +Tomasz Myrta + +From pgsql-performance-owner@postgresql.org Thu Dec 19 14:36:39 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0DF5D475F26 + for ; + Thu, 19 Dec 2002 14:36:38 -0500 (EST) +Received: from lakemtao01.cox.net (lakemtao01.cox.net [68.1.17.244]) + by postgresql.org (Postfix) with ESMTP id 6C674475E7B + for ; + Thu, 19 Dec 2002 14:36:37 -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 <20021219193638.WOP4411.lakemtao01.cox.net@[192.168.1.1]> + for ; + Thu, 19 Dec 2002 14:36:38 -0500 +Subject: Re: 4G row table? +From: Ron Johnson +To: PgSQL Performance ML +In-Reply-To: <20021219141058.11d4b693.gry@ll.mit.edu> +References: <20021219141058.11d4b693.gry@ll.mit.edu> +Content-Type: text/plain +Organization: +Message-Id: <1040326596.28772.186.camel@haggis> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 19 Dec 2002 13:36:36 -0600 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/194 +X-Sequence-Number: 610 + +On Thu, 2002-12-19 at 13:10, george young wrote: +> [linux, 700MHz athlon, 512MB RAM, 700GB 10kRPM SCSI HW RAID, postgresql 7.2] +> We're setting up a DB of IC test data, which is very simple and regular, but large. +> One project (we get three or four per year) has ~4 giga bits, each specified by +> a few small integer values, e.g.: +> Name Type Values +> ---------------------- +> wafer int 1-50 +> die_row int 2-7 +> die_col int 2-7 +> testtype string (~10 different short strings) +> vdd int 0-25 +> bit_col int 0-127 +> bit_row int 0-511 +> value bit 0 or 1 +> +> with 4 billion(4e9) rows. I would guess to make wafer, die_row, etc. be of +> type "char", probably testtype a char too with a separate testtype lookup table. +> Even so, this will be a huge table. + +How many records per day will be inserted? + +Will they ever be updated? + +Do you have to have *ALL* 4 billion records in the same table at the +same time? As Josh Berkus mentioned, wafer thru bit_col can be +converted to INT2, if you make testtype use a lookup table; thus, each +tuple could be shrunk to 20 bytes, plus 24 bytes per tuple (in v7.3) +that would make the table a minimum of 189 billion bytes, not +including index!!! + +Rethink your solution... + +One possibility would to have a set of tables, with names like: +TEST_DATA_200301 +TEST_DATA_200302 +TEST_DATA_200303 +TEST_DATA_200304 +TEST_DATA_200305 +TEST_DATA_200306 +TEST_DATA_200307 +TEST_DATA_ + +Then, each month do "CREATE VIEW TEST_DATA AS TEST_DATA_yyyymm" for the +current month. + + +> Questions: How much overhead will there be in the table in addition to the +> 9 bytes of data I see? How big will the primary index on the first seven columns +> be? Will this schema work at all? +> +> Of course, we could pack 128 bits into an 8 byte "text" field (or should we use bit(128)?), +> but lose some ease of use, especially for naive (but important) users. +> +> Comments, suggestions? +> +> -- George +> +-- ++---------------------------------------------------------------+ +| 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 Thu Dec 19 17:47:09 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BED48475D00 + for ; + Thu, 19 Dec 2002 17:47:07 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 1A5C6475CBC + for ; + Thu, 19 Dec 2002 17:47:07 -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 gBJMkKpd006982; + Thu, 19 Dec 2002 17:46:20 -0500 (EST) +To: Joe Conway +Cc: Josh Berkus , Tomasz Myrta , + PgSQL Performance ML +Subject: Re: EXISTS vs IN vs OUTER JOINS +In-reply-to: <3E02053C.7070305@joeconway.com> +References: + <3E02053C.7070305@joeconway.com> +Comments: In-reply-to Joe Conway + message dated "Thu, 19 Dec 2002 09:43:24 -0800" +Date: Thu, 19 Dec 2002 17:46:20 -0500 +Message-ID: <6981.1040337980@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/196 +X-Sequence-Number: 612 + +Joe Conway writes: +> I wonder if "[NOT] IN (subselect)" could be improved with a hash table in +> similar fashion to the hash aggregate solution Tom recently implemented? + +It's being worked on ;-) + +http://archives.postgresql.org/pgsql-hackers/2002-11/msg01055.php + +Assuming I get this done, the conventional wisdom that "EXISTS +outperforms IN" will be stood on its head --- unless we add planner code +to try to reverse-engineer an IN from an EXISTS, which is something I'm +not really eager to expend code and cycles on. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Dec 19 17:53:22 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CCAD3475F00 + for ; + Thu, 19 Dec 2002 17:53:20 -0500 (EST) +Received: from candle.pha.pa.us (momjian.navpoint.com [207.106.42.251]) + by postgresql.org (Postfix) with ESMTP id 006DD475D00 + for ; + Thu, 19 Dec 2002 17:53:01 -0500 (EST) +Received: (from pgman@localhost) + by candle.pha.pa.us (8.11.6/8.10.1) id gBJMqON27748; + Thu, 19 Dec 2002 17:52:24 -0500 (EST) +From: Bruce Momjian +Message-Id: <200212192252.gBJMqON27748@candle.pha.pa.us> +Subject: Re: EXISTS vs IN vs OUTER JOINS +In-Reply-To: <6981.1040337980@sss.pgh.pa.us> +To: Tom Lane +Date: Thu, 19 Dec 2002 17:52:24 -0500 (EST) +Cc: Joe Conway , Josh Berkus , + Tomasz Myrta , + 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: 200212/197 +X-Sequence-Number: 613 + +Tom Lane wrote: +> Joe Conway writes: +> > I wonder if "[NOT] IN (subselect)" could be improved with a hash table in +> > similar fashion to the hash aggregate solution Tom recently implemented? +> +> It's being worked on ;-) +> +> http://archives.postgresql.org/pgsql-hackers/2002-11/msg01055.php +> +> Assuming I get this done, the conventional wisdom that "EXISTS +> outperforms IN" will be stood on its head --- unless we add planner code +> to try to reverse-engineer an IN from an EXISTS, which is something I'm +> not really eager to expend code and cycles on. + +I am looking forward to removing _that_ FAQ item. :-) + +-- + 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 Dec 19 18:20:38 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 14879476082 + for ; + Thu, 19 Dec 2002 18:20:34 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id C1A9B4769EF + for ; + Thu, 19 Dec 2002 18:19:19 -0500 (EST) +Received: from [216.135.165.74] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2292427; Thu, 19 Dec 2002 15:19:21 -0800 +From: "Josh Berkus" +Subject: Re: EXISTS vs IN vs OUTER JOINS +To: jasiek@klaster.net, Josh Berkus +Cc: jasiek@klaster.net, + PgSQL Performance ML +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Thu, 19 Dec 2002 15:19:21 -0800 +Message-ID: +In-Reply-To: <20021219192830.GA8336@serwer> +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: 200212/198 +X-Sequence-Number: 614 + +Tomasz, + +> I read your mail once again, but I still don't understand what are +> you +> talking about. +> I'll write example - maybe it will help us to understand each other. + +Hmmm ... you're right. Sorry for being dense. It shouldn't work, but +it does. + +Tom, Bruce: + +If I run the query: + +SELECT t1.* +FROM table1 t1 + LEFT JOIN table2 t2 ON t1.xid = t2.xid +WHERE t2.label IS NULL + +I will get rows in t1 for which there is no row in t2. This does not +seem SQL-spec to me; shouldn't I get only rows from t1 where a row +exists in t2 and t2.label IS NULL? + +-Josh + +From pgsql-performance-owner@postgresql.org Thu Dec 19 19:03:31 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 53890475F5F + for ; + Thu, 19 Dec 2002 19:03:29 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id C90CD4768AA + for ; + Thu, 19 Dec 2002 19:02:14 -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 gBK02Dpd010091; + Thu, 19 Dec 2002 19:02:14 -0500 (EST) +To: "Josh Berkus" +Cc: jasiek@klaster.net, + PgSQL Performance ML +Subject: Re: EXISTS vs IN vs OUTER JOINS +In-reply-to: +References: +Comments: In-reply-to "Josh Berkus" + message dated "Thu, 19 Dec 2002 15:19:21 -0800" +Date: Thu, 19 Dec 2002 19:02:13 -0500 +Message-ID: <10090.1040342533@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/199 +X-Sequence-Number: 615 + +"Josh Berkus" writes: +> If I run the query: + +> SELECT t1.* +> FROM table1 t1 +> LEFT JOIN table2 t2 ON t1.xid = t2.xid +> WHERE t2.label IS NULL + +> I will get rows in t1 for which there is no row in t2. This does not +> seem SQL-spec to me; shouldn't I get only rows from t1 where a row +> exists in t2 and t2.label IS NULL? + +No; that would be the behavior of an inner join, but you did a left +join. The above will give you t1 rows for which there is no match in t2 +(plus rows for which there is a match containing null in t2.label). + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 20 03:54:16 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 46EB64758C9 + for ; + Fri, 20 Dec 2002 03:54:15 -0500 (EST) +Received: from email04.aon.at (WARSL402PIP5.highway.telekom.at [195.3.96.79]) + by postgresql.org (Postfix) with SMTP id 6B8AD4758BD + for ; + Fri, 20 Dec 2002 03:54:14 -0500 (EST) +Received: (qmail 298194 invoked from network); 20 Dec 2002 08:54:14 -0000 +Received: from m169p025.dipool.highway.telekom.at (HELO cantor) + ([62.46.11.25]) (envelope-sender ) + by qmail5rs.highway.telekom.at (qmail-ldap-1.03) with SMTP + for ; 20 Dec 2002 08:54:14 -0000 +From: Manfred Koizar +To: "Josh Berkus" +Cc: jasiek@klaster.net, + PgSQL Performance ML +Subject: Re: EXISTS vs IN vs OUTER JOINS +Date: Fri, 20 Dec 2002 09:53:56 +0100 +Message-ID: <53m50vohh8v0asvmb425e9lplphvb1m6b1@4ax.com> +References: <20021219192830.GA8336@serwer> + +In-Reply-To: +X-Mailer: Forte Agent 1.8/32.548 +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: 200212/200 +X-Sequence-Number: 616 + +On Thu, 19 Dec 2002 15:19:21 -0800, "Josh Berkus" +wrote: +>SELECT t1.* +>FROM table1 t1 +> LEFT JOIN table2 t2 ON t1.xid = t2.xid +>WHERE t2.label IS NULL + +Josh, also note that Tomasz did something like + +SELECT t1.* +FROM table1 t1 + LEFT JOIN table2 t2 ON t1.xid = t2.xid +WHERE t2.xid IS NULL + ^^^ +This special trick guarantees that you get exactly the rows from t1 +not having a matching row in t2, because a NULL xid in t2 would not +satisfy the condition t1.xid = t2.xid. + +Servus + Manfred + +From pgsql-performance-owner@postgresql.org Fri Dec 20 05:28:20 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 855914767E6 + for ; + Fri, 20 Dec 2002 05:28:18 -0500 (EST) +Received: from email05.aon.at (WARSL401PIP2.highway.telekom.at [195.3.96.74]) + by postgresql.org (Postfix) with SMTP id B415D47600E + for ; + Fri, 20 Dec 2002 05:28:05 -0500 (EST) +Received: (qmail 391048 invoked from network); 20 Dec 2002 10:27:36 -0000 +Received: from m169p025.dipool.highway.telekom.at (HELO cantor) + ([62.46.11.25]) (envelope-sender ) + by qmail7rs.highway.telekom.at (qmail-ldap-1.03) with SMTP + for ; 20 Dec 2002 10:27:36 -0000 +From: Manfred Koizar +To: gry@ll.mit.edu +Cc: pgsql-performance@postgresql.org +Subject: Re: 4G row table? +Date: Fri, 20 Dec 2002 11:27:18 +0100 +Message-ID: +References: <20021219141058.11d4b693.gry@ll.mit.edu> +In-Reply-To: <20021219141058.11d4b693.gry@ll.mit.edu> +X-Mailer: Forte Agent 1.8/32.548 +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: 200212/201 +X-Sequence-Number: 617 + +On Thu, 19 Dec 2002 14:10:58 -0500, george young +wrote: +>with 4 billion(4e9) rows. +>How big will the primary index on the first seven columns be? + +If you manage to pack the key into 8 bytes (by using a custom 1 byte +integer datatype) and if there are no NULLs: + + 75 GB with a 100% fill factor, + 114 GB with a 66% fill factor, +realistically something in between. Note that frequent updates can +cause index growth. + +>Will this schema work at all? + +You have a somewhat unusual identifier : payload ratio (8B : 1b). It +depends on the planned use, but I'm not sure if *any* database is the +right solution. You have "only" 30670848000 (30G) possible different +key combinations, more than 1/8 of them (4G) are actually used. A +7-dimensional array of double-bits (1 bit to indicate a valid value +and 1 bit payload) would require not more than 8 GB. + +If you plan to use a database because you have to answer ad-hoc +queries, you will almost certainly need additonal indices. + +Servus + Manfred + +From pgsql-performance-owner@postgresql.org Fri Dec 20 12:01:26 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 32BEB475B33 + for ; + Fri, 20 Dec 2002 12:01:24 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id 89229475AEC + for ; + Fri, 20 Dec 2002 12:01:23 -0500 (EST) +Received: from [63.195.55.98] (account ) + by davinci.ethosmedia.com (CommuniGate Pro WebUser 4.0.2) + with HTTP id 2293056; Fri, 20 Dec 2002 09:01:28 -0800 +From: "Josh Berkus" +Subject: Re: 4G row table? +To: "Charles H. Woloszynski" , josh@agliodbs.com +Cc: gry@ll.mit.edu, pgsql-performance@postgresql.org +X-Mailer: CommuniGate Pro Web Mailer v.4.0.2 +Date: Fri, 20 Dec 2002 09:01:28 -0800 +Message-ID: +In-Reply-To: <3E021D9D.1040608@clearmetrix.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: 200212/202 +X-Sequence-Number: 618 + +Charlie, + +> Why do you say to expect slow performance on this hardware? Is +> there something specific about the configuration that worries you? +> Or, just lots of data in the database, so the data will be on disk +> and not in the cache (system or postgresql)? +> What do you classify as *slow*? Obviously, he is dependent on the +> I/O channel given the size of the tables. So, good indexing will be +> required to help on the queries. No comments on the commit rate for +> this data (I am guessing that it is slow, given the description of +> the database), so that may or may not be an issue. +> Depending on the type of queries, perhaps clustering will help, along +> with some good partitioning indexes. +> I just don't see the slow in the hardware. Of course, if he is +> targeting lots of concurrent queries, better add some additional +> processors, or better yet, use ERSERVER and replicate the data to a +> farm of machines. [To avoid the I/O bottleneck of lots of concurrent +> queries against these large tables]. +> +> I guess there are a lot of assumptions on the data's use to decide if +> the hardware is adequate or not :-) + +Well, slow is relative. It may be fast enough for him. Me, I'd be +screaming in frustration. + +Take, for example, an index scan on the primary key. Assuming that he +can get the primary key down to 12 bytes per node using custom data +types, that's still: + +12bytes * 4,000,000,000 rows = 48 GB for the index + +As you can see, it's utterly impossible for him to load even the +primary key index into his 512 MB of RAM (of which no more than 200mb +can go to Postgres anyway without risking conflicts over RAM). A +Sort-and-Limit on the primary key, for example, would require swapping +the index from RAM to swap space as much as 480 times! (though probably +more like 100 times on average) + +With a slow RAID array and the hardware he described to us, this would +mean, most likely, that a simple sort-and-limit on primary key query +could take hours to execute. Even with really fast disk access, we're +talking tens of minutes at least. + +-Josh Berkus + + + + +From pgsql-performance-owner@postgresql.org Fri Dec 20 17:58:18 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 1C376476D8D + for ; + Fri, 20 Dec 2002 17:58:17 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 0314947709C + for ; + Fri, 20 Dec 2002 17:57:26 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP id 03F5B34B53 + for ; + Fri, 20 Dec 2002 17:57:28 -0500 (EST) +Date: Fri, 20 Dec 2002 17:57:28 -0500 +Mime-Version: 1.0 (Apple Message framework v548) +Content-Type: text/plain; charset=US-ASCII; format=flowed +Subject: Speed Question +From: Noah Silverman +To: pgsql-performance@postgresql.org +Content-Transfer-Encoding: 7bit +Message-Id: <69932226-146E-11D7-8943-000393AA8F3C@allresearch.com> +X-Mailer: Apple Mail (2.548) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/203 +X-Sequence-Number: 619 + +Hello, + +We are considering switching our systems over from MySQL to Postgresql. + +Speed is one of our major concerns, so before switching we've decided +to perform some speed tests. + From what I understand, Postgresql is NOT as fast as Mysql, but should +be close enough. + +We've installed the software and have run some basic insert, index and +query tests that +seem ridiculously slow. I can't help thinking that we are doing +something wrong, or +don't have things configured for optimal performance. + +We've performed these same tests on Mysql and then run dramatically +faster. + +Here's the initial performance test results and issues... + +Table configuration: +speedtest( prop1 integer, prop2 integer, prop3 integer, prop4 integer); +indexes on each of the four individual property fields + +Each record consists of four random integers, uniformly distributed, +between 0 and 1000. The integers are computed in the perl script +used to populate the table, not using an SQL random() function. + +Hardware configuration: P3-500, 384MB ram, *unloaded* system. +Software configuration: Linux 2.4.20, reiserfs, standard slackware +install. + +Issue #1: Speed of inserts is relatively slow. 100000 inserts is +taking +roughly 10 minutes. This isn't EVIL, but mysql appears to be about +ten times faster here. Is there something we could do to the indexes +differently? Disable transactions? Is there a more "raw" insert, which +may not set off triggers? + +Issue #2: It doesn't appear as though multiple indexes are being used. +ie: select count(*) from speedtest where (prop1 between 100 and 200) +and( prop2 between 100 and 200) and (prop3 between 100 and 200) +and (prop4 between 100 and 200) formulates a query plan that only +uses one index. The following is pasted from the 'explain select' --- + + Aggregate (cost=17.16..17.16 rows=1 width=0) + -> Index Scan using p4 on speedtest (cost=0.00..17.16 rows=1 +width=0) + Index Cond: ((prop4 >= 100) AND (prop4 <= 200)) + Filter: ((prop1 >= 100) AND (prop1 <= 200) AND (prop2 >= 100) +AND +(prop2 <= 200) AND (prop3 >= 100) AND (prop3 <= 200)) +(4 rows) + +It appears as though the index on prop4 is being used to determine a +subset +of records to fetch -- subsequently filtering them with the other +conditions. +Unfortunately, since the index condition matches 10% of the table (due +to +the random uniform integers from 0-1000), this results in a large +number of +record fetches and examinations the db engine must make. This query +takes +at least a second to execute, whereas we would like to be able to drop +this +into the sub-0.1 second range, and preferably into the millisecond +range. +While this would run faster on the production machines than on my +workstation, +it is still a fundamental flaw that multiple indexes aren't being +combined to +restrict the record set to fetch. + +OTOH, if we could do index combining, we could fetch 10% of 10% of 10% +of the initial 10% of records... Resulting in a microscopic number of +items +to retrieve and examine. + +Can anybody give me some ideas as to what I am doing wrong??? + +Thanks, + +-Noah + + +From pgsql-performance-owner@postgresql.org Fri Dec 20 18:24:36 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id C27E34762A4 + for ; + Fri, 20 Dec 2002 18:24:34 -0500 (EST) +Received: from mail1.ihs.com (mail1.ihs.com [170.207.70.222]) + by postgresql.org (Postfix) with ESMTP id 7B2C9476212 + for ; + Fri, 20 Dec 2002 18:24:33 -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 gBKNNgnX024317; + Fri, 20 Dec 2002 16:23:42 -0700 (MST) +Date: Fri, 20 Dec 2002 16:23:59 -0700 (MST) +From: "scott.marlowe" +To: Noah Silverman +Cc: +Subject: Re: Speed Question +In-Reply-To: <69932226-146E-11D7-8943-000393AA8F3C@allresearch.com> +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: 200212/204 +X-Sequence-Number: 620 + +On Fri, 20 Dec 2002, Noah Silverman wrote: + +> Issue #1: Speed of inserts is relatively slow. 100000 inserts is +> taking +> roughly 10 minutes. This isn't EVIL, but mysql appears to be about +> ten times faster here. Is there something we could do to the indexes +> differently? Disable transactions? Is there a more "raw" insert, which +> may not set off triggers? + +Are you doing these in a transaction? If not, then try adding a +begin;end; pair around your inserts. i.e. + +begin; +insert 100000 rows +end; + +that should help. + + +Reading the rest of your message, it appears there are two issues here. +One is you might get some help from a multi-column index. + +Further, have you run analyze on your database? + +Have you read the administrative docs yet? There's lots more good stuff +in there too. These are the basics. + +The other issue is the assumption that indexes are ALWAYS faster, which +they aren't. If the query planner thinks it's gonna grab some significant +portion of a table, it will just grab the whole thing instead of using an +index, which makes a certain amount of sense. To reduce the likelihood of +the planner picking a sequential scan, change random_page_cost from the +default 4 to something lower. A 1 means that the cost of grabbing a page +randomly is the same as grabbing it sequentially, which shouldn't be +possible, but is, if the data is all in memory. + +Next, use EXPLAIN ANALYZE to get an output of both what the query planner +THOUGHT it was going to do, and what the query actually did, in terms of +time to execute. + +Let us know how it all turns out. + + +From pgsql-performance-owner@postgresql.org Fri Dec 20 18:50:27 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 0803C475C98 + for ; + Fri, 20 Dec 2002 18:50:26 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 50AE7475C22 + for ; + Fri, 20 Dec 2002 18:50:25 -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 gBKNoPpd025959; + Fri, 20 Dec 2002 18:50:25 -0500 (EST) +To: "scott.marlowe" +Cc: Noah Silverman , + pgsql-performance@postgresql.org +Subject: Re: Speed Question +In-reply-to: +References: +Comments: In-reply-to "scott.marlowe" + message dated "Fri, 20 Dec 2002 16:23:59 -0700" +Date: Fri, 20 Dec 2002 18:50:25 -0500 +Message-ID: <25958.1040428225@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/205 +X-Sequence-Number: 621 + +"scott.marlowe" writes: +> On Fri, 20 Dec 2002, Noah Silverman wrote: +>> Issue #1: Speed of inserts is relatively slow. 100000 inserts is + +> Are you doing these in a transaction? If not, then try adding a +> begin;end; pair around your inserts. i.e. + +> begin; +> insert 100000 rows +> end; + +Or use a COPY command instead of retail inserts. See also the tips at +http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/populate.html + +> One is you might get some help from a multi-column index. + +Yes, I'd recommend a multi-column index when no single column is +particularly selective. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Fri Dec 20 18:58:02 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id AE35C475C98 + for ; + Fri, 20 Dec 2002 18:58:00 -0500 (EST) +Received: from davinci.ethosmedia.com (unknown [209.10.40.251]) + by postgresql.org (Postfix) with ESMTP id DDFE6475C22 + for ; + Fri, 20 Dec 2002 18:57:59 -0500 (EST) +Received: from [66.219.92.2] (HELO chocolate-mousse) + by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.0.2) + with ESMTP id 2293611; Fri, 20 Dec 2002 15:58:02 -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: Speed Question +Date: Fri, 20 Dec 2002 15:59:23 -0800 +X-Mailer: KMail [version 1.4] +References: <69932226-146E-11D7-8943-000393AA8F3C@allresearch.com> +In-Reply-To: <69932226-146E-11D7-8943-000393AA8F3C@allresearch.com> +MIME-Version: 1.0 +Content-Transfer-Encoding: quoted-printable +Message-Id: <200212201559.23341.josh@agliodbs.com> +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/206 +X-Sequence-Number: 622 + +Noah, + +> Speed is one of our major concerns, so before switching we've decided=20 +> to perform some speed tests. +> From what I understand, Postgresql is NOT as fast as Mysql, + +This is a PR myth spread by MySQL AB. The truth is: + +1) PostgreSQL, unconfigured and not optimized, is indeed slower than MySQL= +=20 +out-of-the-box. MySQL is meant to be idiot-proof; PostgreSQL is not,=20 +intentionally. + +2) Nobody has yet come up with a database benchmark that both MySQL AB and = +the=20 +PostgreSQL team are willing to accept; depending on whose benchmark you use= +,=20 +either could be faster -- and neither benchmark may approximate your setup. + +> We've installed the software and have run some basic insert, index and=20 +> query tests that +> seem ridiculously slow. I can't help thinking that we are doing=20 +> something wrong, or +> don't have things configured for optimal performance. + +Almost undoubtedly. Have you modified the postgresql.conf file at all?=20= +=20 +Where are your database files located on disk? How are you construting you= +r=20 +queries? + +> We've performed these same tests on Mysql and then run dramatically=20 +> faster. + +Without transations? Sure. Turn off transaction logging, and PostgreSQL= +=20 +runs faster, too. + +>=20 +> Here's the initial performance test results and issues... +>=20 +> Table configuration: +> speedtest( prop1 integer, prop2 integer, prop3 integer, prop4 integer); +> indexes on each of the four individual property fields +>=20 +> Each record consists of four random integers, uniformly distributed, +> between 0 and 1000. The integers are computed in the perl script +> used to populate the table, not using an SQL random() function. +>=20 +> Hardware configuration: P3-500, 384MB ram, *unloaded* system. +> Software configuration: Linux 2.4.20, reiserfs, standard slackware=20 +> install. + +You haven't mentioned your PostgreSQL memory settings, by which I assume th= +at=20 +you haven't configured them. This is very important. + +> Issue #1: Speed of inserts is relatively slow. 100000 inserts is=20 +> taking +> roughly 10 minutes. This isn't EVIL, but mysql appears to be about +> ten times faster here. Is there something we could do to the indexes +> differently? Disable transactions? Is there a more "raw" insert, which +> may not set off triggers? + +Bundle them in a single transaction. Move pg_xlog to a seperate drive from= +=20 +the database. + +> Issue #2: It doesn't appear as though multiple indexes are being used. +> ie: select count(*) from speedtest where (prop1 between 100 and 200) +> and( prop2 between 100 and 200) and (prop3 between 100 and 200) +> and (prop4 between 100 and 200) formulates a query plan that only +> uses one index. The following is pasted from the 'explain select' --- + +That's correct; Postgres will only use a single index on this query. If yo= +u=20 +want to reference all columns, create a multi-column index. Note that,=20 +however, Postgres is likely to reject the index as it is just as large as t= +he=20 +table. In this way, your test is insufficiently like real data. + +Good luck. Why not use the Open Database Benchmark for testing, instead of= +=20 +inventing your own? + + http://www.sf.net/projects/osdb + +--=20 +-Josh Berkus + Aglio Database Solutions + San Francisco + + +From pgsql-performance-owner@postgresql.org Fri Dec 20 19:10:48 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B8D3A476188 + for ; + Fri, 20 Dec 2002 19:10:47 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id CB36E476164 + for ; + Fri, 20 Dec 2002 19:10:46 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP id 590EB36480 + for ; + Fri, 20 Dec 2002 19:10:49 -0500 (EST) +Date: Fri, 20 Dec 2002 19:10:49 -0500 +Mime-Version: 1.0 (Apple Message framework v548) +Content-Type: text/plain; charset=US-ASCII; format=flowed +Subject: Re: Speed Question +From: Noah Silverman +To: pgsql-performance@postgresql.org +Content-Transfer-Encoding: 7bit +Message-Id: +X-Mailer: Apple Mail (2.548) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/207 +X-Sequence-Number: 623 + +First: THANK YOU everyone for all your suggestions. + +I've discovered the "copy from" command and it helps a lot. +Right now, we just ran a test on 1MM rows with 4 columns and it is very +fast with a 4 column index. Works well. + +Now we are creating more of a real world example: 10MM rows with 32 +columns of integers. I'm loading up the data now, and will create a +multi-column index(on all 32) after the data is loaded. + + From everyone's responses I understand that we really need to tune the +system to get optimal performance. I would love to do this, but don't +really know where to start. Below are our system stats if anyone wants +to suggest some settings: + +2x AMD 2100MP CPU +2 GB RAM +Data - 350GB on a raid5 card +Note: We will probably NEVER use transactions, so turning off that +feature would be fine if it would help, and we knew how. + +Our data is probably only going to take up 20% MAXIMUM of our RAID. +Subsequently, we have no problem trading a little extra space for +better performance. + +BTW - is there any kind of "describe table" and/or "show index" +function if pgsql. I've gotten very used to them in Mysql, but they +don't work here. There must be some way. I've RTFM, but can't find +anything. help. + +THANKS AGAIN, + +-Noah + + + +From pgsql-performance-owner@postgresql.org Fri Dec 20 20:01:15 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D16AC475CB4 + for ; + Fri, 20 Dec 2002 20:01:14 -0500 (EST) +Received: from cypress.adhesivemedia.com (cypress.adhesivemedia.com + [207.202.159.72]) + by postgresql.org (Postfix) with ESMTP id 18952475C22 + for ; + Fri, 20 Dec 2002 20:01:14 -0500 (EST) +Received: from cypress.adhesivemedia.com (localhost [127.0.0.1]) + by cypress.adhesivemedia.com (8.12.3/8.12.3) with ESMTP id + gBL11DFk003932; Fri, 20 Dec 2002 17:01:13 -0800 (PST) + (envelope-from philip@adhesivemedia.com) +Received: from localhost (philip@localhost) + by cypress.adhesivemedia.com (8.12.3/8.12.3/Submit) with ESMTP id + gBL11DHX003929; Fri, 20 Dec 2002 17:01:13 -0800 (PST) +X-Authentication-Warning: cypress.adhesivemedia.com: philip owned process + doing -bs +Date: Fri, 20 Dec 2002 17:01:13 -0800 (PST) +From: Philip Hallstrom +To: Noah Silverman +Cc: pgsql-performance@postgresql.org +Subject: Re: Speed Question +In-Reply-To: +Message-ID: <20021220170025.N3706-100000@cypress.adhesivemedia.com> +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/208 +X-Sequence-Number: 624 + +> BTW - is there any kind of "describe table" and/or "show index" +> function if pgsql. I've gotten very used to them in Mysql, but they +> don't work here. There must be some way. I've RTFM, but can't find +> anything. help. + +In psql use "\d tablename". do a "\?" for a quick overview and "man psql" +for lots of stuff. + +-philip + + +From pgsql-performance-owner@postgresql.org Sat Dec 21 07:21:46 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id F34E5475AFF + for ; + Sat, 21 Dec 2002 07:21:44 -0500 (EST) +Received: from email06.aon.at (WARSL401PIP3.highway.telekom.at [195.3.96.75]) + by postgresql.org (Postfix) with SMTP id 0ECE34753A1 + for ; + Sat, 21 Dec 2002 07:21:44 -0500 (EST) +Received: (qmail 198134 invoked from network); 21 Dec 2002 12:21:46 -0000 +Received: from m169p031.dipool.highway.telekom.at (HELO cantor) + ([62.46.11.31]) (envelope-sender ) + by qmail6rs.highway.telekom.at (qmail-ldap-1.03) with SMTP + for ; 21 Dec 2002 12:21:46 -0000 +From: Manfred Koizar +To: Noah Silverman +Cc: pgsql-performance@postgresql.org +Subject: Re: Speed Question +Date: Sat, 21 Dec 2002 13:21:31 +0100 +Message-ID: <04k80vsfcspvni82kmqkj8qodrh3qbmthq@4ax.com> +References: +In-Reply-To: +X-Mailer: Forte Agent 1.8/32.548 +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: 200212/209 +X-Sequence-Number: 625 + +On Fri, 20 Dec 2002 19:10:49 -0500, Noah Silverman + wrote: +>Now we are creating more of a real world example: 10MM rows with 32 +>columns of integers. I'm loading up the data now, and will create a +>multi-column index(on all 32) after the data is loaded. + +If a table with a 32 column key and no dependent attributes is a real +world example, I'd like to see your use case ;-) + +An index on c1, c2, ..., cn will only help, if your search criteria +contain (strict) conditions on the leading index columns, e.g. + WHERE c1 = ... AND c2 = ... AND c3 BETWEEN ... AND ... + +It won't help for + WHERE c22 = ... + +> From everyone's responses I understand that we really need to tune [...] +>2x AMD 2100MP CPU +>2 GB RAM +>Data - 350GB on a raid5 card + +It all depends on your application, but looking at SHARED_BUFFERS, +EFFECTIVE_CACHE_SIZE, SORT_MEM, MAX_FSM_RELATIONS, and MAX_FSM_PAGES +might be a good start. Later you might want to use CPU_*_COST, +RANDOM_PAGE_COST, and various WAL settings to fine tune your system. + +>Note: We will probably NEVER use transactions, + +Oh yes, you will. You have no other choice. If you don't enclose +(several) statements between BEGIN and COMMIT, every statement is +automatically wrapped into its own transaction. + +It helps performance and consistency, if *you* control transactions. + +Servus + Manfred + +From pgsql-performance-owner@postgresql.org Sat Dec 21 13:45:31 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 42654474E44 + for ; + Sat, 21 Dec 2002 13:45:30 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id AEC10474E53 + for ; + Sat, 21 Dec 2002 13:45:29 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP + id 9B55E36577; Sat, 21 Dec 2002 13:45:29 -0500 (EST) +Date: Sat, 21 Dec 2002 13:46:05 -0500 +Subject: Re: Speed Question +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: pgsql-performance@postgresql.org +To: Manfred Koizar +From: Noah Silverman +In-Reply-To: <04k80vsfcspvni82kmqkj8qodrh3qbmthq@4ax.com> +Message-Id: <76295AB6-1514-11D7-B570-003065BAA92A@allresearch.com> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/210 +X-Sequence-Number: 626 + +Thanks for the help. We've been using MySQL for the last 4 years, so +PgSQL is a whole new world for me. Lots to learn + +Actually the "real world" test we are performing is an exact +duplication of our intended use. Without divulging too many company +secrets, we create a 32 key profile of an object. We then have to be +able to search the database to find "similar" objects. In reality, we +will probably have 20MM to 30MM rows in our table. I need to very +quickly find the matching records on a "test" object. + +If you're really curious as to more details, let me know (I don't want +to bore the group with our specifics) + +Since this machine is solely a database server, I want to utilize a ton +of RAM to help things along. Probably at lease 1.5 Gigs worth. I +guess my next step is to try and figure out what all the various memory +settings are and where to set them. + +Thanks, + +-N + + +On Saturday, December 21, 2002, at 07:21 AM, Manfred Koizar wrote: + +> On Fri, 20 Dec 2002 19:10:49 -0500, Noah Silverman +> wrote: +>> Now we are creating more of a real world example: 10MM rows with 32 +>> columns of integers. I'm loading up the data now, and will create a +>> multi-column index(on all 32) after the data is loaded. +> +> If a table with a 32 column key and no dependent attributes is a real +> world example, I'd like to see your use case ;-) +> +> An index on c1, c2, ..., cn will only help, if your search criteria +> contain (strict) conditions on the leading index columns, e.g. +> WHERE c1 = ... AND c2 = ... AND c3 BETWEEN ... AND ... +> +> It won't help for +> WHERE c22 = ... +> +>> From everyone's responses I understand that we really need to tune +>> [...] +>> 2x AMD 2100MP CPU +>> 2 GB RAM +>> Data - 350GB on a raid5 card +> +> It all depends on your application, but looking at SHARED_BUFFERS, +> EFFECTIVE_CACHE_SIZE, SORT_MEM, MAX_FSM_RELATIONS, and MAX_FSM_PAGES +> might be a good start. Later you might want to use CPU_*_COST, +> RANDOM_PAGE_COST, and various WAL settings to fine tune your system. +> +>> Note: We will probably NEVER use transactions, +> +> Oh yes, you will. You have no other choice. If you don't enclose +> (several) statements between BEGIN and COMMIT, every statement is +> automatically wrapped into its own transaction. +> +> It helps performance and consistency, if *you* control transactions. +> +> Servus +> Manfred +> +> + + +From pgsql-performance-owner@postgresql.org Sat Dec 21 15:04:32 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B602C475DDB + for ; + Sat, 21 Dec 2002 15:04:30 -0500 (EST) +Received: from email05.aon.at (WARSL401PIP2.highway.telekom.at [195.3.96.74]) + by postgresql.org (Postfix) with SMTP id 5BCA9476176 + for ; + Sat, 21 Dec 2002 15:02:53 -0500 (EST) +Received: (qmail 427602 invoked from network); 21 Dec 2002 20:02:53 -0000 +Received: from m150p026.dipool.highway.telekom.at (HELO cantor) + ([62.46.8.186]) (envelope-sender ) + by qmail7rs.highway.telekom.at (qmail-ldap-1.03) with SMTP + for ; 21 Dec 2002 20:02:53 -0000 +From: Manfred Koizar +To: Noah Silverman +Cc: pgsql-performance@postgresql.org +Subject: Re: Speed Question +Date: Sat, 21 Dec 2002 21:02:39 +0100 +Message-ID: +References: <04k80vsfcspvni82kmqkj8qodrh3qbmthq@4ax.com> + <76295AB6-1514-11D7-B570-003065BAA92A@allresearch.com> +In-Reply-To: <76295AB6-1514-11D7-B570-003065BAA92A@allresearch.com> +X-Mailer: Forte Agent 1.8/32.548 +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: 200212/211 +X-Sequence-Number: 627 + +On Sat, 21 Dec 2002 13:46:05 -0500, Noah Silverman + wrote: +>Without divulging too many company +>secrets, we create a 32 key profile of an object. We then have to be +>able to search the database to find "similar" objects. + +... where "similar" means that the value of each attribute lies within +a small range around the value of the corresponding attribute of the +reference object? + +I fear a multicolumn b-tree index is not the optimal solution to this +problem, unless you have some extremely selective attributes you can +put at the start of the index. But then again I doubt that it makes +sense to include even the last attribute (or the last few attributes) +into the index. + +>In reality, we +>will probably have 20MM to 30MM rows in our table. I need to very +>quickly find the matching records on a "test" object. + +This seems to be a nice case for utilizing bitmaps for index scans. +Thus you would scan several single column indices and combine the +bitmaps before accessing the heap tuples. This has been discussed on +-hackers and I believe it is a todo item. + +I don't know, whether GiST or R-Tree could help. Is anybody listening +who knows? + +>If you're really curious as to more details, let me know (I don't want +>to bore the group with our specifics) + +The group is patient :-) + +Servus + Manfred + +From pgsql-performance-owner@postgresql.org Sat Dec 21 15:17:18 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 63E034759BD + for ; + Sat, 21 Dec 2002 15:17:17 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id D3BA84759AF + for ; + Sat, 21 Dec 2002 15:17:16 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP + id 8A6B536710; Sat, 21 Dec 2002 15:17:17 -0500 (EST) +Date: Sat, 21 Dec 2002 15:17:53 -0500 +Subject: Re: Speed Question +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v551) +Cc: pgsql-performance@postgresql.org +To: Manfred Koizar +From: Noah Silverman +In-Reply-To: +Message-Id: <491F60CE-1521-11D7-B570-003065BAA92A@allresearch.com> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.551) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/212 +X-Sequence-Number: 628 + +You are correct. "similar" means within a small range. + +Below is a sample query: + +select count(*) from speedtest where (p1 between 209 and 309) and (p2 +between 241 and 341) and (p3 between 172 and 272) and (p4 between 150 +and 250) and (p5 between 242 and 342) and (p6 between 222 and 322) and +(p7 between 158 and 258) and (p8 between 249 and 349) and (p9 between +162 and 262) and (p10 between 189 and 289) and (p11 between 201 and +301) and (p12 between 167 and 267) and (p13 between 167 and 267) and +(p14 between 229 and 329) and (p15 between 235 and 335) and (p16 +between 190 and 290) and (p17 between 240 and 340) and (p18 between 156 +and 256) and (p19 between 150 and 250) and (p20 between 171 and 271) +and (p21 between 241 and 341) and (p22 between 244 and 344) and (p23 +between 219 and 319) and (p24 between 198 and 298) and (p25 between 196 +and 296) and (p26 between 243 and 343) and (p27 between 160 and 260) +and (p28 betw een 151 and 251) and (p29 between 226 and 326) and (p30 +between 168 and 268) and (p31 between 153 and 253) and (p32 between +218 and 318) + +Currently, on an un-tuned installation, this query takes about 1 +second. Much too slow for our needs. We need to be able to execute +about 30-50 per second. + + +I'm not a database expert. There is probably a better way to do this, +but I have no idea how. + +The general use of this table is as an index for document storage. +When we come across a new document, we have to know if we already have +something close to it. Exact checksums don't work because two +documents with only a few different words are still "the same" for our +intended use. We calculate 32 separate checksums on parts of each +document. By storing all 32, we have a good representation of each +document. A new document can then very quickly be checked against the +table to see if we already have something close to it. + +If anybody has any better ideas, I would love to hear it... + +-N + + +On Saturday, December 21, 2002, at 03:02 PM, Manfred Koizar wrote: + +> On Sat, 21 Dec 2002 13:46:05 -0500, Noah Silverman +> wrote: +>> Without divulging too many company +>> secrets, we create a 32 key profile of an object. We then have to be +>> able to search the database to find "similar" objects. +> +> ... where "similar" means that the value of each attribute lies within +> a small range around the value of the corresponding attribute of the +> reference object? +> +> I fear a multicolumn b-tree index is not the optimal solution to this +> problem, unless you have some extremely selective attributes you can +> put at the start of the index. But then again I doubt that it makes +> sense to include even the last attribute (or the last few attributes) +> into the index. +> +>> In reality, we +>> will probably have 20MM to 30MM rows in our table. I need to very +>> quickly find the matching records on a "test" object. +> +> This seems to be a nice case for utilizing bitmaps for index scans. +> Thus you would scan several single column indices and combine the +> bitmaps before accessing the heap tuples. This has been discussed on +> -hackers and I believe it is a todo item. +> +> I don't know, whether GiST or R-Tree could help. Is anybody listening +> who knows? +> +>> If you're really curious as to more details, let me know (I don't want +>> to bore the group with our specifics) +> +> The group is patient :-) +> +> Servus +> Manfred +> +> + + +From pgsql-performance-owner@postgresql.org Sat Dec 21 15:28:34 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D2B15475D99 + for ; + Sat, 21 Dec 2002 15:28:31 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id D32E3475D64 + for ; + Sat, 21 Dec 2002 15:28:30 -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 gBLKSMd0001961; + Sat, 21 Dec 2002 15:28:22 -0500 (EST) +To: Manfred Koizar +Cc: Noah Silverman , + pgsql-performance@postgresql.org +Subject: Re: Speed Question +In-reply-to: +References: <04k80vsfcspvni82kmqkj8qodrh3qbmthq@4ax.com> + <76295AB6-1514-11D7-B570-003065BAA92A@allresearch.com> + +Comments: In-reply-to Manfred Koizar + message dated "Sat, 21 Dec 2002 21:02:39 +0100" +Date: Sat, 21 Dec 2002 15:28:22 -0500 +Message-ID: <1960.1040502502@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/213 +X-Sequence-Number: 629 + +Manfred Koizar writes: +> ... where "similar" means that the value of each attribute lies within +> a small range around the value of the corresponding attribute of the +> reference object? + +> I don't know, whether GiST or R-Tree could help. + +If the problem is multidimensional range search then GIST might be just +the ticket. I am not sure if you'd need to do any coding though. It +looks like contrib/btree_gist provides the necessary operator class, but +only for int4 and timestamp datatypes. + +I think that our r-tree code is restricted to two-dimensional indexing, +so it wouldn't help. + + regards, tom lane + +From pgsql-general-owner@postgresql.org Sun Dec 22 20:19:23 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id CC4F64758DC + for ; + Sun, 22 Dec 2002 20:19:20 -0500 (EST) +Received: from main.gmane.org (main.gmane.org [80.91.224.249]) + by postgresql.org (Postfix) with ESMTP id 0CABE474E5C + for ; + Sun, 22 Dec 2002 20:19:20 -0500 (EST) +Received: from list by main.gmane.org with local (Exim 3.35 #1 (Debian)) + id 18QHF2-0001L8-00 + for ; Mon, 23 Dec 2002 02:18:48 +0100 +X-Injected-Via-Gmane: http://gmane.org/ +To: pgsql-general@postgresql.org +Received: from news by main.gmane.org with local (Exim 3.35 #1 (Debian)) + id 18QHF1-0001Kz-00 + for ; + Mon, 23 Dec 2002 02:18:47 +0100 +Path: not-for-mail +From: Gerhard Haering +Subject: Re: PerformPortalClose warning in 7.3 +Date: Mon, 23 Dec 2002 01:18:46 +0000 (UTC) +Organization: People's Front of Judea +Lines: 88 +Message-ID: +References: <3DF91030.A372DF7C@nsd.ca> + <2C6CDB6A-0E24-11D7-8E88-000393A48A3C@mac.com> +X-Complaints-To: usenet@main.gmane.org +User-Agent: slrn/0.9.7.4 (FreeBSD) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/1062 +X-Sequence-Number: 34977 + +Michael Engelhart wrote in gmane.comp.db.postgresql.general: +> Hi - +> I've been running PostgreSQL 7.3 on Mac OS X 10.2 since it was released +> and it's been running fine. I'm using pyPgSQL 2.3 for client side +> programming which also was working great until tonight. Now whenever +> I do any query of any type, I get warnings like this: +> +> WARNING: PerformPortalClose: portal "pgsql_00179f10" not found +> +> It "appears" that everything is still working the way it was but it's a +> bit discomforting to have these show up on my screen while running my +> applications. +> +> Anyone that can explain this? +> +> Here's a tiny bit of Python sample code that I used to make sure it +> wasn't my other code causing the problems +> +> from pyPgSQL import PgSQL +> +> dbname = "template1" +> conn = PgSQL.connect(database=dbname) +> cursor = conn.cursor() +> sql = "SELECT now()"; +> cursor.execute(sql) +> res = cursor.fetchall() +> for i in res: +> print i +> cursor.close() +> conn.commit() + +Actually, pyPgSQL is using PostgreSQL portals behind your back. This +is a feature! + +To show this, we use the undocumented, but very handy toggleShowQuery +flag. The effect is that we can see what SQL pyPgSQL sends to the +backend using libpq (the lines staring with QUERY: below): + +#v+ +gerhard@gargamel:~$ python +Python 2.2.2 (#1, Nov 30 2002, 23:19:58) +[GCC 2.95.4 20020320 [FreeBSD]] on freebsd4 +Type "help", "copyright", "credits" or "license" for more information. +>>> from pyPgSQL import PgSQL +>>> con = PgSQL.connect() +>>> con.conn.toggleShowQuery +'On' +>>> cursor = con.cursor() +QUERY: BEGIN WORK +>>> cursor.execute("select * from test") +QUERY: DECLARE "PgSQL_0811F1EC" CURSOR FOR select * from test +QUERY: FETCH 1 FROM "PgSQL_0811F1EC" +QUERY: SELECT typname, -1 , typelem FROM pg_type WHERE oid = 23 +QUERY: SELECT typname, -1 , typelem FROM pg_type WHERE oid = 1043 +>>> result = cursor.fetchmany(5) +QUERY: FETCH 4 FROM "PgSQL_0811F1EC" +>>> result +[[None, 'A'], [None, 'B'], [None, 'C'], [None, 'F'], [None, 'F']] +>>> con.commit() +QUERY: CLOSE PgSQL_0811F1EC +QUERY: COMMIT WORK +>>> +#v- + +This gives me a warning like this: + +#v+ +WARNING: PerformPortalClose: portal "pgsql_0811f1ec" not found +#v- + +As far as I can see, the SQL pyPgSQL emits is perfectly ok. But I'd be +glad to hear a clarification. + +> strangely if I remove the last 2 lines (cursor.close() and +> conn.commit()) I don't get the errors. +> +> Also I don't notice that I don't have this problem with psql command +> line either. Is this the Python API causing this? + +If you use the same SQL statements using portals in psql, you get the +same warning (obviously). I just tried. + +Gerhard (pyPgSQL developer) +-- +Favourite database: http://www.postgresql.org/ +Favourite programming language: http://www.python.org/ +Combine the two: http://pypgsql.sf.net/ +Embedded database for Python: http://pysqlite.sf.net/ + + + +From pgsql-general-owner@postgresql.org Sun Dec 22 21:36:32 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D93D8475AE4 + for ; + Sun, 22 Dec 2002 21:36:30 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 1EF1F4758FE + for ; + Sun, 22 Dec 2002 21:36:30 -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 gBN2aRd0028407; + Sun, 22 Dec 2002 21:36:27 -0500 (EST) +To: Gerhard Haering +Cc: pgsql-general@postgresql.org +Subject: Re: PerformPortalClose warning in 7.3 +In-reply-to: +References: <3DF91030.A372DF7C@nsd.ca> + <2C6CDB6A-0E24-11D7-8E88-000393A48A3C@mac.com> + +Comments: In-reply-to Gerhard Haering + message dated "Mon, 23 Dec 2002 01:18:46 +0000" +Date: Sun, 22 Dec 2002 21:36:27 -0500 +Message-ID: <28406.1040610987@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/1064 +X-Sequence-Number: 34979 + +Gerhard Haering writes: +> To show this, we use the undocumented, but very handy toggleShowQuery +> flag. The effect is that we can see what SQL pyPgSQL sends to the +> backend using libpq (the lines staring with QUERY: below): + + +> QUERY: DECLARE "PgSQL_0811F1EC" CURSOR FOR select * from test +> ... +> QUERY: CLOSE PgSQL_0811F1EC + +This looks like a pyPgSQL bug to me. If it's going to use a mixed-case +name for the cursor then it must either always double-quote the name or +never do so. Failing to double-quote in the CLOSE command is wrong. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Mon Dec 23 16:55:05 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id D7A0D47603C + for ; + Mon, 23 Dec 2002 16:55:02 -0500 (EST) +Received: from allresearch.com (allresearch.com [209.73.229.162]) + by postgresql.org (Postfix) with ESMTP id 4DB5C475E52 + for ; + Mon, 23 Dec 2002 16:55:01 -0500 (EST) +Received: from allresearch.com (office.allresearch.com [209.73.255.249]) + by allresearch.com (Postfix) with ESMTP + id F35F3371F5; Mon, 23 Dec 2002 16:55:01 -0500 (EST) +Date: Mon, 23 Dec 2002 16:55:01 -0500 +Subject: Re: Speed Question +Content-Type: text/plain; charset=US-ASCII; format=flowed +Mime-Version: 1.0 (Apple Message framework v548) +Cc: Manfred Koizar , pgsql-performance@postgresql.org +To: Tom Lane +From: Noah Silverman +In-Reply-To: <1960.1040502502@sss.pgh.pa.us> +Message-Id: <2FB53415-16C1-11D7-A512-000393AA8F3C@allresearch.com> +Content-Transfer-Encoding: 7bit +X-Mailer: Apple Mail (2.548) +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/214 +X-Sequence-Number: 630 + +Does anyone know how/where I can find the contrib/btree_gist stuff and +how I use it, and are there docs for it. + +Thanks, + +-N + + +On Saturday, December 21, 2002, at 03:28 PM, Tom Lane wrote: + +> Manfred Koizar writes: +>> ... where "similar" means that the value of each attribute lies within +>> a small range around the value of the corresponding attribute of the +>> reference object? +> +>> I don't know, whether GiST or R-Tree could help. +> +> If the problem is multidimensional range search then GIST might be just +> the ticket. I am not sure if you'd need to do any coding though. It +> looks like contrib/btree_gist provides the necessary operator class, +> but +> only for int4 and timestamp datatypes. +> +> I think that our r-tree code is restricted to two-dimensional indexing, +> so it wouldn't help. +> +> regards, tom lane +> + + +From pgsql-performance-owner@postgresql.org Tue Dec 24 15:05:20 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 6F5F247647B + for ; + Tue, 24 Dec 2002 15:05:19 -0500 (EST) +Received: from wolff.to (wolff.to [66.93.197.35]) + by postgresql.org (Postfix) with SMTP id 8BCB847645A + for ; + Tue, 24 Dec 2002 15:05:16 -0500 (EST) +Received: (qmail 15924 invoked by uid 500); 24 Dec 2002 20:16:38 -0000 +Date: Tue, 24 Dec 2002 14:16:38 -0600 +From: Bruno Wolff III +To: pgsql-performance@postgresql.org +Subject: View performance +Message-ID: <20021224201638.GA15882@wolff.to> +Mail-Followup-To: pgsql-performance@postgresql.org +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +User-Agent: Mutt/1.3.25i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/215 +X-Sequence-Number: 631 + +I was looking at some queries that appeared to be slower than I remembered +them being under 7.2 (which may be a wrong perception) and noticed +that a view wasn't being handled very efficiently. + +The view is security view that is used to hide some fields in some records +when displaying information on the web. The primary key is left alone +though. When this view is joined a plan is generated that applies +the field suppression for each row of the underlying table even though +only a few rows out of this view are going to be selected. It would see +that first looking for rows that will be used and only applying the +changes to rows that are going to be used would result in a significant +speed up. + +The other thing that seemed odd is that the constant +(select pord from priv where pname = 'web') subqueries weren't pulled +out of the loop. + +I was able to get a 20% speed up by adding an index on gameid to crate +and by disabling merge joins so that a has join was used instead. +The merge join estimate was about 20% low and the hash join estimate +was about 100% high resulting in the merge join getting picked. + +View: +create view cname_web as select + areaid, + case when (select pord from priv where pname = 'web') >= + (select pord from priv where pname = privacy) then + lname else null end as lname, + case when (select pord from priv where pname = 'web') >= + (select pord from priv where pname = privacy) then + fmname else null end as fmname, + case when (select pord from priv where pname = 'web') >= + (select pord from priv where pname = privacy) then + aname else null end as aname, + case when (select pord from priv where pname = 'web') >= + (select pord from priv where pname = privacy) then + gen else null end as gen, + case when (select pord from priv where pname = 'web') >= + (select pord from priv where pname = privacy) then + genlab else null end as genlab, + case when (select pord from priv where pname = 'web') >= + (select pord from priv where pname = privacy) then + touched else null end as touched + from cname; + +Query: + +explain analyze select cname_web.areaid, lname, fmname, aname, coalesce(genlab, to_char(gen, 'FMRN')), rate, frq, opp, rmp, trn, to_char(crate.touched,'YYYY-MM-DD') from cname_web, crate where cname_web.areaid = crate.areaid and gameid = '776' and frq > 0 and crate.touched >= ((timestamp 'epoch' + '1040733601 second') + '2 year ago') order by rate desc, lower(lname), lower(coalesce((aname || ' ') || fmname, fmname, aname)), gen, genlab, cname_web.areaid; + QUERY PLAN +---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- + Sort (cost=1308.35..1308.44 rows=39 width=203) (actual time=1152.67..1152.68 rows=25 loops=1) + Sort Key: crate.rate, lower(cname_web.lname), lower(CASE WHEN (((cname_web.aname || ' '::text) || cname_web.fmname) IS NOT NULL) THEN ((cname_web.aname || ' '::text) || cname_web.fmname) WHEN (cname_web.fmname IS NOT NULL) THEN cname_web.fmname WHEN (cname_web.aname IS NOT NULL) THEN cname_web.aname ELSE NULL::text END), cname_web.gen, cname_web.genlab, cname_web.areaid + -> Merge Join (cost=1270.71..1307.31 rows=39 width=203) (actual time=1120.23..1152.25 rows=25 loops=1) + Merge Cond: ("outer".areaid = "inner".areaid) + -> Sort (cost=681.95..699.97 rows=7208 width=63) (actual time=1079.55..1083.66 rows=7147 loops=1) + Sort Key: cname_web.areaid + -> Subquery Scan cname_web (cost=0.00..220.08 rows=7208 width=63) (actual time=0.40..843.48 rows=7208 loops=1) + -> Seq Scan on cname (cost=0.00..220.08 rows=7208 width=63) (actual time=0.40..818.24 rows=7208 loops=1) + InitPlan + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.04..0.05 rows=1 loops=1) + Filter: (pname = 'web'::text) + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.02 rows=1 loops=1) + Filter: (pname = 'web'::text) + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.02 rows=1 loops=1) + Filter: (pname = 'web'::text) + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.02 rows=1 loops=1) + Filter: (pname = 'web'::text) + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.02 rows=1 loops=1) + Filter: (pname = 'web'::text) + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.02 rows=1 loops=1) + Filter: (pname = 'web'::text) + SubPlan + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.01 rows=1 loops=7208) + Filter: (pname = $1) + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.01 rows=1 loops=7208) + Filter: (pname = $1) + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.01 rows=1 loops=7208) + Filter: (pname = $1) + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.01 rows=1 loops=7208) + Filter: (pname = $1) + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.01 rows=1 loops=7208) + Filter: (pname = $1) + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.01..0.01 rows=1 loops=7208) + Filter: (pname = $1) + -> Sort (cost=588.76..588.80 rows=16 width=39) (actual time=39.95..39.96 rows=25 loops=1) + Sort Key: crate.areaid + -> Seq Scan on crate (cost=0.00..588.45 rows=16 width=39) (actual time=3.14..39.58 rows=25 loops=1) + Filter: ((gameid = '776'::text) AND (frq > 0) AND (touched >= '2000-12-24 12:40:01'::timestamp without time zone)) + Total runtime: 1155.29 msec +(39 rows) + + +From pgsql-performance-owner@postgresql.org Tue Dec 24 15:55:18 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 153AC4758E1 + for ; + Tue, 24 Dec 2002 15:55:16 -0500 (EST) +Received: from wolff.to (wolff.to [66.93.197.35]) + by postgresql.org (Postfix) with SMTP id 3C92A475843 + for ; + Tue, 24 Dec 2002 15:55:15 -0500 (EST) +Received: (qmail 16100 invoked by uid 500); 24 Dec 2002 21:06:37 -0000 +Date: Tue, 24 Dec 2002 15:06:37 -0600 +From: Bruno Wolff III +To: pgsql-performance@postgresql.org +Subject: Re: View performance +Message-ID: <20021224210637.GA16085@wolff.to> +Mail-Followup-To: pgsql-performance@postgresql.org +References: <20021224201638.GA15882@wolff.to> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <20021224201638.GA15882@wolff.to> +User-Agent: Mutt/1.3.25i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/216 +X-Sequence-Number: 632 + +As a followup to this I rewrote the view as: +create view cname_web as select + a.areaid, b.lname, b.fmname, b.aname, b.gen, b.genlab, b.touched + from cname a left join + (select areaid, lname, fmname, aname, gen, genlab, touched, privacy + from cname, priv + where pname = privacy and + pord <= (select pord from priv where pname = 'web') + ) b + using (areaid); + +And got the query down to about half the original time as shown here: + QUERY PLAN +------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ + Sort (cost=970.71..970.74 rows=15 width=113) (actual time=550.82..550.83 rows=25 loops=1) + Sort Key: crate.rate, lower(cname.lname), lower(CASE WHEN (((cname.aname || ' '::text) || cname.fmname) IS NOT NULL) THEN ((cname.aname || ' '::text) || cname.fmname) WHEN (cname.fmname IS NOT NULL) THEN cname.fmname WHEN (cname.aname IS NOT NULL) THEN cname.aname ELSE NULL::text END), cname.gen, cname.genlab, a.areaid + InitPlan + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.02..0.03 rows=1 loops=1) + Filter: (pname = 'web'::text) + -> Merge Join (cost=484.88..970.41 rows=15 width=113) (actual time=361.92..550.53 rows=25 loops=1) + Merge Cond: ("outer".areaid = "inner".areaid) + -> Merge Join (cost=348.16..815.45 rows=7208 width=74) (actual time=358.29..520.50 rows=7147 loops=1) + Merge Cond: ("outer".areaid = "inner".areaid) + -> Index Scan using cname_pkey on cname a (cost=0.00..407.27 rows=7208 width=11) (actual time=0.03..26.59 rows=7147 loops=1) + -> Sort (cost=348.16..354.17 rows=2403 width=63) (actual time=358.20..362.38 rows=7141 loops=1) + Sort Key: cname.areaid + -> Hash Join (cost=1.09..213.25 rows=2403 width=63) (actual time=0.35..94.32 rows=7202 loops=1) + Hash Cond: ("outer".privacy = "inner".pname) + -> Seq Scan on cname (cost=0.00..146.08 rows=7208 width=55) (actual time=0.01..33.41 rows=7208 loops=1) + -> Hash (cost=1.09..1.09 rows=2 width=8) (actual time=0.07..0.07 rows=0 loops=1) + -> Seq Scan on priv (cost=0.00..1.09 rows=2 width=8) (actual time=0.06..0.07 rows=2 loops=1) + Filter: (pord <= $0) + -> Sort (cost=136.72..136.76 rows=15 width=39) (actual time=0.95..0.96 rows=25 loops=1) + Sort Key: crate.areaid + -> Index Scan using crate_game on crate (cost=0.00..136.42 rows=15 width=39) (actual time=0.10..0.67 rows=25 loops=1) + Index Cond: (gameid = '776'::text) + Filter: ((frq > 0) AND (touched >= '2000-12-24 12:40:01'::timestamp without time zone)) + Total runtime: 553.17 msec +(24 rows) + +On Tue, Dec 24, 2002 at 14:16:38 -0600, + Bruno Wolff III wrote: +> +> View: +> create view cname_web as select +> areaid, +> case when (select pord from priv where pname = 'web') >= +> (select pord from priv where pname = privacy) then +> lname else null end as lname, +> case when (select pord from priv where pname = 'web') >= +> (select pord from priv where pname = privacy) then +> fmname else null end as fmname, +> case when (select pord from priv where pname = 'web') >= +> (select pord from priv where pname = privacy) then +> aname else null end as aname, +> case when (select pord from priv where pname = 'web') >= +> (select pord from priv where pname = privacy) then +> gen else null end as gen, +> case when (select pord from priv where pname = 'web') >= +> (select pord from priv where pname = privacy) then +> genlab else null end as genlab, +> case when (select pord from priv where pname = 'web') >= +> (select pord from priv where pname = privacy) then +> touched else null end as touched +> from cname; +> +> Query: +> +> explain analyze select cname_web.areaid, lname, fmname, aname, coalesce(genlab, to_char(gen, 'FMRN')), rate, frq, opp, rmp, trn, to_char(crate.touched,'YYYY-MM-DD') from cname_web, crate where cname_web.areaid = crate.areaid and gameid = '776' and frq > 0 and crate.touched >= ((timestamp 'epoch' + '1040733601 second') + '2 year ago') order by rate desc, lower(lname), lower(coalesce((aname || ' ') || fmname, fmname, aname)), gen, genlab, cname_web.areaid; + +From pgsql-performance-owner@postgresql.org Tue Dec 24 16:14:36 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id EDF944758E1 + for ; + Tue, 24 Dec 2002 16:14:34 -0500 (EST) +Received: from wolff.to (wolff.to [66.93.197.35]) + by postgresql.org (Postfix) with SMTP id 2C634475843 + for ; + Tue, 24 Dec 2002 16:14:34 -0500 (EST) +Received: (qmail 16182 invoked by uid 500); 24 Dec 2002 21:25:56 -0000 +Date: Tue, 24 Dec 2002 15:25:56 -0600 +From: Bruno Wolff III +To: pgsql-performance@postgresql.org +Subject: Re: View performance +Message-ID: <20021224212556.GA16170@wolff.to> +Mail-Followup-To: pgsql-performance@postgresql.org +References: <20021224201638.GA15882@wolff.to> + <20021224210637.GA16085@wolff.to> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <20021224210637.GA16085@wolff.to> +User-Agent: Mutt/1.3.25i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/217 +X-Sequence-Number: 633 + +By disabling merge joins and using the updated view, I got the query down +to about 25% of its original runtime. +Note the query estimate is off by a factor of more than 10. + QUERY PLAN +------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ + Sort (cost=3271.35..3271.39 rows=15 width=113) (actual time=232.25..232.27 rows=25 loops=1) + Sort Key: crate.rate, lower(cname.lname), lower(CASE WHEN (((cname.aname || ' '::text) || cname.fmname) IS NOT NULL) THEN ((cname.aname || ' '::text) || cname.fmname) WHEN (cname.fmname IS NOT NULL) THEN cname.fmname WHEN (cname.aname IS NOT NULL) THEN cname.aname ELSE NULL::text END), cname.gen, cname.genlab, a.areaid + InitPlan + -> Seq Scan on priv (cost=0.00..1.09 rows=1 width=4) (actual time=0.02..0.03 rows=1 loops=1) + Filter: (pname = 'web'::text) + -> Hash Join (cost=355.71..3271.05 rows=15 width=113) (actual time=106.82..231.97 rows=25 loops=1) + Hash Cond: ("outer".areaid = "inner".areaid) + -> Hash Join (cost=219.25..431.41 rows=7208 width=74) (actual time=103.86..222.00 rows=7208 loops=1) + Hash Cond: ("outer".areaid = "inner".areaid) + -> Seq Scan on cname a (cost=0.00..146.08 rows=7208 width=11) (actual time=0.01..16.23 rows=7208 loops=1) + -> Hash (cost=213.25..213.25 rows=2403 width=63) (actual time=103.70..103.70 rows=0 loops=1) + -> Hash Join (cost=1.09..213.25 rows=2403 width=63) (actual time=0.35..88.82 rows=7202 loops=1) + Hash Cond: ("outer".privacy = "inner".pname) + -> Seq Scan on cname (cost=0.00..146.08 rows=7208 width=55) (actual time=0.01..29.73 rows=7208 loops=1) + -> Hash (cost=1.09..1.09 rows=2 width=8) (actual time=0.07..0.07 rows=0 loops=1) + -> Seq Scan on priv (cost=0.00..1.09 rows=2 width=8) (actual time=0.06..0.07 rows=2 loops=1) + Filter: (pord <= $0) + -> Hash (cost=136.42..136.42 rows=15 width=39) (actual time=0.72..0.72 rows=0 loops=1) + -> Index Scan using crate_game on crate (cost=0.00..136.42 rows=15 width=39) (actual time=0.10..0.66 rows=25 loops=1) + Index Cond: (gameid = '776'::text) + Filter: ((frq > 0) AND (touched >= '2000-12-24 12:40:01'::timestamp without time zone)) + Total runtime: 232.83 msec +(22 rows) + + +From pgsql-performance-owner@postgresql.org Thu Dec 26 14:42:42 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 98E1F475DC5 + for ; + Thu, 26 Dec 2002 14:42:40 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 0640E475D87 + for ; + Thu, 26 Dec 2002 14:42:40 -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 gBQJgdd0002667; + Thu, 26 Dec 2002 14:42:40 -0500 (EST) +To: Bruno Wolff III +Cc: pgsql-performance@postgresql.org +Subject: Re: View performance +In-reply-to: <20021224201638.GA15882@wolff.to> +References: <20021224201638.GA15882@wolff.to> +Comments: In-reply-to Bruno Wolff III + message dated "Tue, 24 Dec 2002 14:16:38 -0600" +Date: Thu, 26 Dec 2002 14:42:39 -0500 +Message-ID: <2666.1040931759@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/218 +X-Sequence-Number: 634 + +Bruno Wolff III writes: +> I was looking at some queries that appeared to be slower than I remembered +> them being under 7.2 (which may be a wrong perception) and noticed +> that a view wasn't being handled very efficiently. + +The change in behavior from 7.2 is probably due to this patch: + +2002-12-05 16:46 tgl + + * src/backend/optimizer/plan/planner.c (REL7_3_STABLE): Avoid + pulling up sublinks from a subselect's targetlist. Works around + problems that occur if sublink is referenced via a join alias + variable. Perhaps this can be improved later, but a simple and + safe fix is needed for 7.3.1. + +which means that views using subselects in their targetlists will not be +flattened into the calling query in 7.3.1. This is not real desirable, +but I see no other short-term fix. + +In the particular case, your view definition seemed mighty inefficient +anyway (it must recompute the subselects for each column retrieved from +the view) so I think your rewrite is a good change. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Dec 26 14:50:16 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A3386475B47 + for ; + Thu, 26 Dec 2002 14:50:14 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id EFBE14753A1 + for ; + Thu, 26 Dec 2002 14:50:13 -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 gBQJoEd0002714; + Thu, 26 Dec 2002 14:50:14 -0500 (EST) +To: Bruno Wolff III +Cc: pgsql-performance@postgresql.org +Subject: Re: View performance +In-reply-to: <20021224212556.GA16170@wolff.to> +References: <20021224201638.GA15882@wolff.to> + <20021224210637.GA16085@wolff.to> + <20021224212556.GA16170@wolff.to> +Comments: In-reply-to Bruno Wolff III + message dated "Tue, 24 Dec 2002 15:25:56 -0600" +Date: Thu, 26 Dec 2002 14:50:14 -0500 +Message-ID: <2713.1040932214@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/219 +X-Sequence-Number: 635 + +Bruno Wolff III writes: +> By disabling merge joins and using the updated view, I got the query down +> to about 25% of its original runtime. +> Note the query estimate is off by a factor of more than 10. + +This seems to indicate some estimation problems in cost_hashjoin; the +estimated cost for the hashjoin is evidently a lot higher than it should +be. + +Are you interested in digging into this; or could you send me a dump of +the tables used in the view and query, so I could look into it? + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Dec 26 15:25:31 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4E070475B47 + for ; + Thu, 26 Dec 2002 15:25:30 -0500 (EST) +Received: from wolff.to (wolff.to [66.93.197.35]) + by postgresql.org (Postfix) with SMTP id 94C724753A1 + for ; + Thu, 26 Dec 2002 15:25:29 -0500 (EST) +Received: (qmail 23060 invoked by uid 500); 26 Dec 2002 20:36:56 -0000 +Date: Thu, 26 Dec 2002 14:36:56 -0600 +From: Bruno Wolff III +To: Tom Lane +Cc: pgsql-performance@postgresql.org +Subject: Re: View performance +Message-ID: <20021226203656.GB22984@wolff.to> +Mail-Followup-To: Tom Lane , + pgsql-performance@postgresql.org +References: <20021224201638.GA15882@wolff.to> <2666.1040931759@sss.pgh.pa.us> +Mime-Version: 1.0 +Content-Type: text/plain; charset=us-ascii +Content-Disposition: inline +In-Reply-To: <2666.1040931759@sss.pgh.pa.us> +User-Agent: Mutt/1.3.25i +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/220 +X-Sequence-Number: 636 + +On Thu, Dec 26, 2002 at 14:42:39 -0500, + Tom Lane wrote: +> +> which means that views using subselects in their targetlists will not be +> flattened into the calling query in 7.3.1. This is not real desirable, +> but I see no other short-term fix. + +Thanks for the explaination. + +> In the particular case, your view definition seemed mighty inefficient +> anyway (it must recompute the subselects for each column retrieved from +> the view) so I think your rewrite is a good change. + +I was naively expecting that the planner would notice the common subexpressions +and only compute them once. + +From pgsql-performance-owner@postgresql.org Thu Dec 26 15:45:56 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 74979474E53 + for ; + Thu, 26 Dec 2002 15:45:55 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id D1979474E44 + for ; + Thu, 26 Dec 2002 15:45:54 -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 gBQKjtd0004245; + Thu, 26 Dec 2002 15:45:55 -0500 (EST) +To: Bruno Wolff III +Cc: pgsql-performance@postgresql.org +Subject: Re: View performance +In-reply-to: <20021226203656.GB22984@wolff.to> +References: <20021224201638.GA15882@wolff.to> <2666.1040931759@sss.pgh.pa.us> + <20021226203656.GB22984@wolff.to> +Comments: In-reply-to Bruno Wolff III + message dated "Thu, 26 Dec 2002 14:36:56 -0600" +Date: Thu, 26 Dec 2002 15:45:55 -0500 +Message-ID: <4244.1040935555@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/221 +X-Sequence-Number: 637 + +Bruno Wolff III writes: +> I was naively expecting that the planner would notice the common +> subexpressions and only compute them once. + +There isn't currently any code for detection of common subexpressions of +any kind. + +My gut feeling is that searching for common subexpressions would be a +net waste of cycles in the vast majority of queries. It'd be fairly +expensive (a naive implementation would be roughly O(N^2) in the number +of expression nodes), with zero payback in very many cases. + +It might be worth doing for very constrained classes of subexpressions. +For instance, I was just thinking about putting in some code to +recognize duplicate aggregates (eg, "sum(foo)" appearing twice in the +same query). nodeAgg.c could do this relatively cheaply, since it has +to make a list of the aggregate expressions to be computed, anyway. +I'm not sure about recognizing duplicated sub-SELECT expressions; it +could possibly be done but some thought would have to be given to +preserving semantics. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Thu Dec 26 18:43:39 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 60C934753A1 + for ; + Thu, 26 Dec 2002 18:43:38 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 0C44C474E53 + for ; + Thu, 26 Dec 2002 18:43:37 -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 gBQNhdd0020651; + Thu, 26 Dec 2002 18:43:39 -0500 (EST) +To: Bruno Wolff III +Cc: pgsql-performance@postgresql.org +Subject: Re: View performance +In-reply-to: <20021226203212.GA22984@wolff.to> +References: <20021224201638.GA15882@wolff.to> + <20021224210637.GA16085@wolff.to> + <20021224212556.GA16170@wolff.to> <2713.1040932214@sss.pgh.pa.us> + <20021226203212.GA22984@wolff.to> +Comments: In-reply-to Bruno Wolff III + message dated "Thu, 26 Dec 2002 14:32:12 -0600" +Date: Thu, 26 Dec 2002 18:43:39 -0500 +Message-ID: <20650.1040946219@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/222 +X-Sequence-Number: 638 + +I wrote: +>> This seems to indicate some estimation problems in cost_hashjoin; the +>> estimated cost for the hashjoin is evidently a lot higher than it should +>> be. + +The answer is that estimate_hash_bucketsize() is producing a rather +silly result in this situation, viz. a bucketsize "fraction" that's well +above 1.0. I've applied the following band-aid patch to CVS tip, which +perhaps you might like to use locally. But probably the long-range +answer is to rethink what that routine is doing --- its adjustment for +skewed data distributions is perhaps not such a great idea. + + regards, tom lane + + +*** src/backend/optimizer/path/costsize.c.orig Fri Dec 13 19:17:55 2002 +--- src/backend/optimizer/path/costsize.c Thu Dec 26 18:34:02 2002 +*************** +*** 1164,1169 **** +--- 1164,1179 ---- + if (avgfreq > 0.0 && mcvfreq > avgfreq) + estfract *= mcvfreq / avgfreq; + ++ /* ++ * Clamp bucketsize to sane range (the above adjustment could easily ++ * produce an out-of-range result). We set the lower bound a little ++ * above zero, since zero isn't a very sane result. ++ */ ++ if (estfract < 1.0e-6) ++ estfract = 1.0e-6; ++ else if (estfract > 1.0) ++ estfract = 1.0; ++ + ReleaseSysCache(tuple); + + return (Selectivity) estfract; + +From pgsql-performance-owner@postgresql.org Fri Dec 27 02:01:32 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4E35D4758C9 + for ; + Fri, 27 Dec 2002 02:01:31 -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 83216474E53 + for ; + Fri, 27 Dec 2002 02:01:30 -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 18RoVD-0005tP-00 + for pgsql-performance@postgresql.org; Fri, 27 Dec 2002 16:01:51 +0900 +Received: from justsystem.co.jp ([10.4.1.38]) + by vrs01.b1.justsystem.co.jp (NAVGW 2.5.1.19) with SMTP id + M2002122716013412584 + for ; Fri, 27 Dec 2002 16:01:34 +0900 +Received: (qmail 8607 invoked from network); 27 Dec 2002 16:01:29 +0900 +Received: from bat.b1.justsystem.co.jp (10.4.1.37) + by owl.b1.justsystem.co.jp with SMTP; 27 Dec 2002 16:01:29 +0900 +Received: from yutaka_inada by bat.b1.justsystem.co.jp (8.8.8/3.6W) id + PAA05960; Fri, 27 Dec 2002 15:58:16 +0900 (JST) +From: yutaka_inada@justsystem.co.jp +MIME-Version: 1.0 +Date: Fri, 27 Dec 2002 16:03:48 +0900 +Subject: executing pgsql on Xeon-dual machine +To: pgsql-performance@postgresql.org +Message-ID: +Content-Type: text/plain +Content-Transfer-Encoding: 7bit +X-Mailer: JsvMail 4.0 (Shuriken Pro2) +X-Priority: 3 +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/223 +X-Sequence-Number: 639 + +Hello, + +I'm facing to a performance problem, when I run PostgreSQL 7. +2.1 + RedHat Linux 7.3 on a Xeon Dual CPU machine. + +Compared with a P4 2.4GHz machine, pgbench shows 1/10 on the +Xeon machine (detail is describled below), while hdparm +shows 2 times faster. + +Disabling HTT had no effects. PostgreSQL 7.2.3 is also slow +on the machine. + +I'm grateful if any of you can give me an advice. + +thank you. + + +data --------------- + +[Hardware Profile] +DELL PowerEdge 2600 + CPU Xeon 2GHz Dual + Memory 2GB PC2100 ECC DDR266 SDRAM + HDD 73GB 10,000rpm U320 SCSI + +DELL PowerEdge 600SC (for comparison) + CPU Pentium 4 2.4GHz Single + Memory 1GB 400MHz ECC DDR SDRAM + HDD 80GB 7,200rpm EIDE + +[pgbench result] + +multiplicity | 1 | 128 +--------------+-----+------ +PE 600 |259.2|178.2 [tps] +PE 2600 | 22.9| 34.8 [tps] + +- wal_sync_method(wal_method.sh) fsync +- 200,000 data items + +--- +Yutaka Inada [Justsystem Corporation] + +From pgsql-performance-owner@postgresql.org Fri Dec 27 13:36:05 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id A5B0F476280 + for ; + Fri, 27 Dec 2002 13:36:04 -0500 (EST) +Received: from sss.pgh.pa.us (unknown [192.204.191.242]) + by postgresql.org (Postfix) with ESMTP id 3F50C4762A2 + for ; + Fri, 27 Dec 2002 13:36:03 -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 gBRIZwd0025731; + Fri, 27 Dec 2002 13:35:59 -0500 (EST) +To: yutaka_inada@justsystem.co.jp +Cc: pgsql-performance@postgresql.org +Subject: Re: executing pgsql on Xeon-dual machine +In-reply-to: +References: +Comments: In-reply-to yutaka_inada@justsystem.co.jp + message dated "Fri, 27 Dec 2002 16:03:48 +0900" +Date: Fri, 27 Dec 2002 13:35:58 -0500 +Message-ID: <25730.1041014158@sss.pgh.pa.us> +From: Tom Lane +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/224 +X-Sequence-Number: 640 + +yutaka_inada@justsystem.co.jp writes: +> Compared with a P4 2.4GHz machine, pgbench shows 1/10 on the +> Xeon machine (detail is describled below), while hdparm +> shows 2 times faster. + +If you set fsync off, how do the pgbench results change? + +> [Hardware Profile] +> DELL PowerEdge 2600 +> CPU Xeon 2GHz Dual +> Memory 2GB PC2100 ECC DDR266 SDRAM +> HDD 73GB 10,000rpm U320 SCSI + +> DELL PowerEdge 600SC (for comparison) +> CPU Pentium 4 2.4GHz Single +> Memory 1GB 400MHz ECC DDR SDRAM +> HDD 80GB 7,200rpm EIDE + +I'm suspicious that the IDE drive may be configured to lie about write +completion. If it reports write complete when it's really only buffered +the data in controller RAM, then you're effectively running with fsync +off on the PE600. + + regards, tom lane + +From pgsql-performance-owner@postgresql.org Sun Dec 29 17:09:11 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id 4691D475CE5 + for ; + Sun, 29 Dec 2002 17:09:10 -0500 (EST) +Received: from cs.uoregon.edu (vitalstatistix.cs.uoregon.edu [128.223.4.19]) + by postgresql.org (Postfix) with ESMTP id 832AC475925 + for ; + Sun, 29 Dec 2002 17:09:09 -0500 (EST) +Received: from ix.cs.uoregon.edu (lili@ix.cs.uoregon.edu [128.223.4.21]) + by cs.uoregon.edu (8.11.0/8.11.0) with ESMTP id gBTM9Aj21751 + for ; + Sun, 29 Dec 2002 14:09:10 -0800 (PST) +Date: Sun, 29 Dec 2002 14:09:10 -0800 (PST) +From: li li +To: +Subject: A question about inheritance +Message-ID: +MIME-Version: 1.0 +Content-Type: TEXT/PLAIN; charset=US-ASCII +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/225 +X-Sequence-Number: 641 + + +Hi, + As we can see all tuples of a child table when scanning parent table, +I'm confused about if that means there are two copies that are stored on +disk, one is for child table, and the other for parent table? If so, +I have to reconsider the size of my database. + Thanks. + +Li Li + + +From pgsql-performance-owner@postgresql.org Mon Dec 30 20:42:50 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id B3C22475FBE + for ; + Mon, 30 Dec 2002 20:42:48 -0500 (EST) +Received: from anchor-post-35.mail.demon.net (anchor-post-35.mail.demon.net + [194.217.242.85]) + by postgresql.org (Postfix) with ESMTP id 126F447592C + for ; + Mon, 30 Dec 2002 20:42:48 -0500 (EST) +Received: from lfix.demon.co.uk ([158.152.59.127] helo=linda.lfix.co.uk) + by anchor-post-35.mail.demon.net with esmtp (Exim 3.36 #2) + id 18TBQg-0006Hc-0Z; Tue, 31 Dec 2002 01:42:50 +0000 +Received: from localhost ([127.0.0.1] ident=olly) + by linda.lfix.co.uk with esmtp (Exim 3.36 #1 (Debian)) + id 18TBQf-0004iS-00; Tue, 31 Dec 2002 01:42:49 +0000 +Subject: Re: A question about inheritance +From: Oliver Elphick +To: li li +Cc: pgsql-performance@postgresql.org +In-Reply-To: +References: +Content-Type: text/plain +Organization: LFIX Limited +Message-Id: <1041298969.22899.27.camel@linda.lfix.co.uk> +Mime-Version: 1.0 +X-Mailer: Ximian Evolution 1.2.0 +Date: 31 Dec 2002 01:42:49 +0000 +Content-Transfer-Encoding: 7bit +X-Virus-Scanned: by AMaViS new-20020517 +X-Archive-Number: 200212/226 +X-Sequence-Number: 642 + +On Sun, 2002-12-29 at 22:09, li li wrote: +> Hi, +> As we can see all tuples of a child table when scanning parent table, +> I'm confused about if that means there are two copies that are stored on +> disk, one is for child table, and the other for parent table? If so, +> I have to reconsider the size of my database. + +When you select from the parent table, all rows in its children are also +selected unless you use the keyword ONLY. + +So + + SELECT * FROM parent; + +will show all rows of parent and children. But + + SELECT * FROM ONLY parent; + +will show just the rows in the parent table. + +-- +Oliver Elphick Oliver.Elphick@lfix.co.uk +Isle of Wight, UK http://www.lfix.co.uk/oliver +GPG: 1024D/3E1D0C1C: CA12 09E0 E8D5 8870 5839 932A 614D 4C34 3E1D 0C1C + ======================================== + "Ye have heard that it hath been said, Thou shalt love + thy neighbour, and hate thine enemy. But I say unto + you, Love your enemies, bless them that curse you, do + good to them that hate you, and pray for them which + despitefully use you, and persecute you;" + Matthew 5:43,44 + + +From pgsql-performance-owner@postgresql.org Tue Dec 31 17:14:35 2002 +Received: from localhost (postgresql.org [64.49.215.8]) + by postgresql.org (Postfix) with ESMTP id BFF46475E1F + for ; + Tue, 31 Dec 2002 17:14:33 -0500 (EST) +Received: from web14810.mail.yahoo.com (web14810.mail.yahoo.com + [216.136.224.231]) + by postgresql.org (Postfix) with SMTP id 284D6475CE5 + for ; + Tue, 31 Dec 2002 17:14:33 -0500 (EST) +Message-ID: <20021231221435.26755.qmail@web14810.mail.yahoo.com> +Received: from [204.155.157.33] by web14810.mail.yahoo.com via HTTP; + Tue, 31 Dec 2002 14:14:34 PST +Date: Tue, 31 Dec 2002 14:14:34 -0800 (PST) +From: Michael Teter +Subject: preliminary testing, two very slow situations... +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: 200212/227 +X-Sequence-Number: 643 + +Howdy. + +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. + +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 +; + Tue, 31 Dec 2002 18:05:26 -0500 (EST) +Received: from bob.samurai.com (bob.samurai.com [205.207.28.75]) + by postgresql.org (Postfix) with ESMTP id 5F8DD475CE5 + for ; + Tue, 31 Dec 2002 18:05:25 -0500 (EST) +Received: from samurai.com (localhost [127.0.0.1]) + by bob.samurai.com (Postfix) with SMTP + id 559091DBA; Tue, 31 Dec 2002 18:05:27 -0500 (EST) +Received: from cpe00d0096a6cd5.cpe.net.cable.rogers.com ([24.112.166.30]) + (SquirrelMail authenticated user neilc) + by mailbox.samurai.com with HTTP; + Tue, 31 Dec 2002 18:05:27 -0500 (EST) +Message-ID: <2973.24.112.166.30.1041375927.squirrel@mailbox.samurai.com> +Date: Tue, 31 Dec 2002 18:05:27 -0500 (EST) +Subject: Re: preliminary testing, two very slow situations... +From: "Neil Conway" +To: +In-Reply-To: <20021231221435.26755.qmail@web14810.mail.yahoo.com> +References: <20021231221435.26755.qmail@web14810.mail.yahoo.com> +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: 200212/228 +X-Sequence-Number: 644 + +Michael Teter said: +> 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. + +[ ... ] + +What version of PostgreSQL are you using? + +Have you made any changes to the default configuration parameters? If not, +that's probably the first thing to look at. Several settings (e.g. +shared_buffers) are set to very conservative values by default. You can +also consider trading some reliability for better performance by disabling +fsync. + +For more info on configuration, see: + +http://www.ca.postgresql.org/users-lounge/docs/7.3/postgres/runtime-config.html + +Another low-hanging fruit is kernel configuration. For example, what OS +and kernel are you using? Have you enabled DMA? What filesystem are you +using? + +Cheers, + +Neil + + +