X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [64.117.224.130]) by svr1.postgresql.org (Postfix) with ESMTP id 48833D1DA62 for ; Fri, 29 Aug 2003 08:11:44 +0000 (GMT) Received: from svr1.postgresql.org ([64.117.224.193]) by localhost (neptune.hub.org [64.117.224.130]) (amavisd-new, port 10024) with ESMTP id 98856-08 for ; Fri, 29 Aug 2003 05:11:35 -0300 (ADT) Received: from houston.familyhealth.com.au (unknown [203.59.48.253]) by svr1.postgresql.org (Postfix) with ESMTP id 50D47D1DA4F for ; Fri, 29 Aug 2003 05:11:32 -0300 (ADT) Received: from mars (work-40.internal [192.168.0.40]) by houston.familyhealth.com.au (8.12.9/8.12.9) with SMTP id h7T8BWLt041736; Fri, 29 Aug 2003 16:11:32 +0800 (WST) (envelope-from chriskl@familyhealth.com.au) Message-ID: <0bf301c36e05$a72f90b0$2800a8c0@mars> From: "Christopher Kings-Lynne" To: "Ken Geis" , "Bruno Wolff III" Cc: References: <3F4E99F7.7080604@speakeasy.org> <20030829025109.GD4373@wolff.to> <3F4EBF7E.8020602@speakeasy.org> <20030829030156.GF4373@wolff.to> <3F4EC1D0.5010503@speakeasy.org> <20030829033818.GA5577@wolff.to> <3F4ECC78.7090502@speakeasy.org> <20030829040519.GA5746@wolff.to> <3F4ED1DC.50808@speakeasy.org> <20030829042453.GA5931@wolff.to> <3F4F0777.8090503@speakeasy.org> <3F4F0A5E.8030207@speakeasy.org> Subject: Re: bad estimates Date: Fri, 29 Aug 2003 16:15:05 +0800 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 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 X-Virus-Scanned: by amavisd-new at postgresql.org X-Archive-Number: 200308/480 X-Sequence-Number: 3296 > > I went through the code (7.4 beta2) that estimates the cost of an index > > scan path. What I need to be sure of is that when running a query in > > pgsql that uses only the columns that are in an index, the underlying > > table need not be accessed. I know that Oracle does this. PostgreSQL absolutely does not do this. It is also not possible to do this due to MVCC. Chris