X-Original-To: pgsql-performance-postgresql.org@postgresql.org Received: from localhost (wm.hub.org [200.46.204.128]) by postgresql.org (Postfix) with ESMTP id 05D639FA236 for ; Mon, 18 Sep 2006 05:22:19 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.128]) (amavisd-new, port 10024) with ESMTP id 18599-04 for ; Mon, 18 Sep 2006 08:22:08 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey- Received: from mail.logix-tt.com (mail.logix-tt.com [212.211.145.186]) by postgresql.org (Postfix) with ESMTP id 6F7B59FA25B for ; Mon, 18 Sep 2006 05:22:08 -0300 (ADT) Received: from kingfisher.intern.logix-tt.com (84-72-188-217.dclient.hispeed.ch [84.72.188.217]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.logix-tt.com (Postfix) with ESMTP id F403B65985 for ; Mon, 18 Sep 2006 10:24:17 +0200 (CEST) Received: from [127.0.0.1] (localhost [127.0.0.1]) by kingfisher.intern.logix-tt.com (Postfix) with ESMTP id 20A38181C1C09 for ; Mon, 18 Sep 2006 10:22:01 +0200 (CEST) Message-ID: <450E5728.7000802@logix-tt.com> Date: Mon, 18 Sep 2006 10:22:00 +0200 From: Markus Schaber Organization: Logical Tracking and Tracing International AG, Switzerland User-Agent: Thunderbird 1.5.0.5 (X11/20060812) MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: Poor performance on seq scan References: <450684EC.4090304@designaproduct.biz> <4506902C.7090407@enterprisedb.com> <200609121410.02710.P.Kolaczkowski@elka.pw.edu.pl> In-Reply-To: <200609121410.02710.P.Kolaczkowski@elka.pw.edu.pl> X-Enigmail-Version: 0.94.0.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0.135 tagged_above=0 required=5 tests=FORGED_RCVD_HELO X-Spam-Level: X-Archive-Number: 200609/226 X-Sequence-Number: 20912 Hi, Piotr, Piotr Ko=C5=82aczkowski wrote: > Why match rows from the heap if ALL required data are in the index itse= lf? > Why look at the heap at all? Because the index does not contain any transaction informations, so it has to look to the heap to find out which of the rows are current. This is one of the more debated points in the PostgreSQL way of MVCC implementation. Markus --=20 Markus Schaber | Logical Tracking&Tracing International AG Dipl. Inf. | Software Development GIS Fight against software patents in Europe! www.ffii.org www.nosoftwarepatents.org