Received: from localhost (unknown [200.46.204.183]) by mail.postgresql.org (Postfix) with ESMTP id 24A4664FCC4 for ; Mon, 10 Nov 2008 02:56:02 -0400 (AST) Received: from mail.postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 86728-05 for ; Mon, 10 Nov 2008 02:56:01 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from www.postnewspapers.com.au (www.postnewspapers.com.au [202.61.230.242]) by mail.postgresql.org (Postfix) with ESMTP id 5AF2364FC12 for ; Mon, 10 Nov 2008 02:56:01 -0400 (AST) Received: from mail.postnewspapers.com.au (202-89-185-120.static.dsl.amnet.net.au [202.89.185.120]) by www.postnewspapers.com.au (Postfix) with ESMTP id DCE695C0C5; Mon, 10 Nov 2008 15:55:55 +0900 (WST) Received: from [10.0.0.53] (wallace.localnet [10.0.0.53]) by mail.postnewspapers.com.au (Postfix) with ESMTP id C44D71E0434; Mon, 10 Nov 2008 15:55:55 +0900 (WST) Message-ID: <4917DAFB.8000003@postnewspapers.com.au> Date: Mon, 10 Nov 2008 15:55:55 +0900 From: Craig Ringer User-Agent: Thunderbird 2.0.0.17 (X11/20080925) MIME-Version: 1.0 To: =?ISO-8859-2?Q?Lutisch=E1n_Ferenc?= Cc: pgsql-performance@postgresql.org Subject: Re: Improve Seq scan performance References: <4917D9C3.9060001@gmail.com> In-Reply-To: <4917D9C3.9060001@gmail.com> Content-Type: text/plain; charset=ISO-8859-2; format=flowed Content-Transfer-Encoding: 8bit X-Archive-Number: 200811/51 X-Sequence-Number: 31782 Lutischán Ferenc wrote: > It is possible to make an index on the table, and make a seq index scan > on this values? My understanding is that this isn't possible in PostgreSQL, because indexes do not contain information about tuple visibility. Data read from the index might refer to tuples that've been deleted as far as your transaction is concerned, or to tuples that were created after your snapshot was taken. -- Craig Ringer