Received: from localhost (maia-1.hub.org [200.46.204.191]) by postgresql.org (Postfix) with ESMTP id 6187E9F93A2 for ; Mon, 1 Jan 2007 19:30:36 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.191]) (amavisd-new, port 10024) with ESMTP id 29636-07 for ; Mon, 1 Jan 2007 19:30:28 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id A78699F9F47 for ; Mon, 1 Jan 2007 19:30:28 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.6/8.13.6) with ESMTP id l01NURXc021167; Mon, 1 Jan 2007 18:30:27 -0500 (EST) To: =?iso-8859-1?q?Rolf=20=D8stvik?= cc: pgsql-performance@postgresql.org, Dennis Bjorklund Subject: Re: Worse perfomance on 8.2.0 than on 7.4.14 In-reply-to: <20070101150410.51809.qmail@web26309.mail.ukl.yahoo.com> References: <20070101150410.51809.qmail@web26309.mail.ukl.yahoo.com> Comments: In-reply-to =?iso-8859-1?q?Rolf=20=D8stvik?= message dated "Mon, 01 Jan 2007 16:04:10 +0100" Date: Mon, 01 Jan 2007 18:30:27 -0500 Message-ID: <21166.1167694227@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200701/4 X-Sequence-Number: 22605 =?iso-8859-1?q?Rolf=20=D8stvik?= writes: > First i have some queries to give you a feel of size > of datasets and plans and times. You said earlier that essentially all the rows of step_result_subset have step_parent = 0 ... is that really true? I can hardly believe that either 7.4 or 8.2 would use an indexscan for Q-A if so. I'd be interested to see the results of prepare foo(int) as select id from step_result_subset sr where uut_result = $1 and step_parent = 0; explain analyze execute foo(42); (use some representative uut_result value instead of 42). If it doesn't want to use an indexscan for this, disable plan types until it does. This would perhaps shed some light on why 8.2 doesn't want to use a scan like that as the inside of a nestloop. regards, tom lane