X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by postgresql.org (Postfix) with ESMTP id 9DFAB9DCA2E for ; Wed, 11 Jan 2006 23:23:56 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 65049-04 for ; Wed, 11 Jan 2006 23:23:58 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey- Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id 81E419DCA50 for ; Wed, 11 Jan 2006 23:23:51 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.1/8.13.1) with ESMTP id k0C3NtXw000482; Wed, 11 Jan 2006 22:23:56 -0500 (EST) To: =?iso-8859-1?Q?Jean-Philippe_C=F4t=E9?= cc: pgsql-performance@postgresql.org Subject: Re: Extremely irregular query performance In-reply-to: <20060111234149.05DEA384099@crt0.crt.umontreal.ca> References: <20060111234149.05DEA384099@crt0.crt.umontreal.ca> Comments: In-reply-to =?iso-8859-1?Q?Jean-Philippe_C=F4t=E9?= message dated "Wed, 11 Jan 2006 18:50:12 -0500" Date: Wed, 11 Jan 2006 22:23:55 -0500 Message-ID: <480.1137036235@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.085 required=5 tests=[AWL=0.085] X-Spam-Score: 0.085 X-Spam-Level: X-Archive-Number: 200601/145 X-Sequence-Number: 16623 =?iso-8859-1?Q?Jean-Philippe_C=F4t=E9?= writes: > Thanks a lot for this info, I was indeed exceeding the genetic > optimizer's threshold. Now that it is turned off, I get > a very stable response time of 435ms (more or less 5ms) for > the same query. It is about three times slower than the best > I got with the genetic optimizer on, but the overall average > is much lower. Hmm. It would be interesting to use EXPLAIN ANALYZE to confirm that the plan found this way is the same as the best plan found by GEQO, and the extra couple hundred msec is the price you pay for the exhaustive plan search. If GEQO is managing to find a plan better than the regular planner then we need to look into why ... regards, tom lane