Received: from localhost (unknown [200.46.204.183]) by developer.postgresql.org (Postfix) with ESMTP id 2488F2E0153 for ; Sat, 31 May 2008 04:42:27 -0300 (ADT) Received: from developer.postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 42978-08 for ; Sat, 31 May 2008 04:42:17 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from outmail128157.authsmtp.net (outmail128157.authsmtp.net [62.13.128.157]) by developer.postgresql.org (Postfix) with ESMTP id 229C92E0152 for ; Sat, 31 May 2008 04:42:21 -0300 (ADT) Received: from mail-c188.authsmtp.com (mail-c188.authsmtp.com [62.13.128.25]) by punt3.authsmtp.com (8.14.2/8.14.2/Kp) with ESMTP id m4V7gFxU049275; Sat, 31 May 2008 08:42:15 +0100 (BST) Received: from [192.168.0.3] (85-211-65-92.dyn.gotadsl.co.uk [85.211.65.92]) (authenticated bits=0) by mail.authsmtp.com (8.14.2/8.14.2/Kp) with ESMTP id m4V7gEJN024213; Sat, 31 May 2008 08:42:14 +0100 (BST) Subject: Re: 2GB or not 2GB From: Simon Riggs To: josh@agliodbs.com Cc: pgsql-performance@postgresql.org In-Reply-To: <200805281659.26945.josh@agliodbs.com> References: <200805281659.26945.josh@agliodbs.com> Content-Type: text/plain Date: Sat, 31 May 2008 08:44:57 +0100 Message-Id: <1212219897.4120.195.camel@ebony.site> Mime-Version: 1.0 X-Mailer: Evolution 2.12.0 Content-Transfer-Encoding: 7bit X-Server-Quench: 16269ac0-2ee5-11dd-aecc-001871e930f4 X-AuthRoute: OCdxZQATClZOTQEd DAteCiNZVAwpPBRK HVkIKg5MJUcNSQVJ NksadBtFawRbYFhI HGQLW1xEUFV7XWF/ ag4fZQBDYEtPQQNv TkFLXVBXFgB3AVJc AngZBWwICQVEfHxx ZghjXndeEkV8d0B0 Ex1UCG9TMGJ9aWFL BF0JIlAHbQNKfxdC awV2V3NbZStlM3Bw LDceBR4WBxBqYH56 aEkKNxoURlpDRBEW L2Fs X-Authentic-SMTP: 61633235383639.cat.dmpriest.net.uk:1045/Kp X-Report-SPAM: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-Virus-Status: No virus detected - but ensure you scan with your own anti-virus system! X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200805/379 X-Sequence-Number: 30347 On Wed, 2008-05-28 at 16:59 -0700, Josh Berkus wrote: > sort_mem: My tests with 8.2 and DBT3 seemed to show that, due to > limitations of our tape sort algorithm, allocating over 2GB for a single > sort had no benefit. However, Magnus and others have claimed otherwise. > Has this improved in 8.3? There is an optimum for each specific sort. Your results cannot be used to make a global recommendation about the setting of work_mem. So not finding any benefit in your tests *and* Magnus seeing an improvement are not inconsistent events. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support