Received: from localhost (unknown [200.46.204.184]) by postgresql.org (Postfix) with ESMTP id 237B12E0063 for ; Mon, 24 Mar 2008 07:03:42 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.184]) (amavisd-maia, port 10024) with ESMTP id 08012-06 for ; Mon, 24 Mar 2008 07:03:20 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from 137086.vserver.de (vs137086.vserver.de [62.75.137.86]) by postgresql.org (Postfix) with ESMTP id 2C4BB2E0062 for ; Mon, 24 Mar 2008 07:03:24 -0300 (ADT) Received: from a-kretschmer.de (p54B3C279.dip0.t-ipconnect.de [84.179.194.121]) (authenticated bits=0) by 137086.vserver.de (8.12.8/8.12.8) with ESMTP id m2OA3IUN014066 for ; Mon, 24 Mar 2008 11:03:19 +0100 Received: from kretschmer by a-kretschmer.de with local (Exim 4.61) (envelope-from ) id 1JdjaJ-0002Cp-E7 for pgsql-performance@postgresql.org; Mon, 24 Mar 2008 11:07:19 +0100 Date: Mon, 24 Mar 2008 11:07:19 +0100 From: Andreas Kretschmer To: pgsql-performance@postgresql.org Subject: Re: increasing shared buffer slow downs query performance. Message-ID: <20080324100718.GA7822@KanotixBox> References: Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-OS: Debian/GNU Linux - weil ich es mir Wert bin! X-GPG-Fingerprint: EE16 3C01 7B9C 10F7 2C8B 3B86 4DB3 D9EE 7F45 84DA X-Message-Flag: "Windows" is not the answer. "Windows" is the question and the answer is "no"! X-Lugdd: Gerd Kube X-Info: My name is root. Just root. And I am licensed to kill -9 User-Agent: mutt-ng 1.5.9i (Linux) X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200803/441 X-Sequence-Number: 29395 petchimuthu lingam schrieb: > Hi friends, > > I am using postgresql 8.1, I have shared_buffers = 50000, now i execute the > query, it takes 18 seconds to do sequential scan, when i reduced to 5000, it > takes one 10 seconds, Why. Wild guess: the second time the data are in the filesystem cache. > > Can anyone explain what is the reason, ( any other configuration is needed in > postgresql.conf) Show us the EXPLAIN ANALYSE - Output. Andreas -- Really, I'm not out to destroy Microsoft. That will just be a completely unintentional side effect. (Linus Torvalds) "If I was god, I would recompile penguin with --enable-fly." (unknow) Kaufbach, Saxony, Germany, Europe. N 51.05082°, E 13.56889°