Received: from localhost (unknown [200.46.204.191]) by postgresql.org (Postfix) with ESMTP id 554389F99D3 for ; Thu, 13 Sep 2007 12:04:10 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.191]) (amavisd-maia, port 10024) with ESMTP id 71471-04 for ; Thu, 13 Sep 2007 12:04:04 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from floppy.pyrenet.fr (news.pyrenet.fr [194.116.145.2]) by postgresql.org (Postfix) with ESMTP id A71349F95F8 for ; Thu, 13 Sep 2007 12:04:03 -0300 (ADT) Received: by floppy.pyrenet.fr (Postfix, from userid 106) id EB54932451; Thu, 13 Sep 2007 17:04:02 +0200 (MET DST) From: Chris Browne X-Newsgroups: pgsql.performance Subject: Re: Clustered tables improves perfs ? Date: Thu, 13 Sep 2007 10:49:57 -0400 Organization: cbbrowne Computing Inc Lines: 20 Message-ID: <608x7azkkq.fsf@dba2.int.libertyrms.com> References: <46E9353A.9080602@agematis.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Complaints-To: usenet@news.hub.org User-Agent: Gnus/5.1008 (Gnus v5.10.8) XEmacs/21.4.20 (linux) Cancel-Lock: sha1:6Y0jagfOp1Ih0K49ptE6HEPG4fY= To: pgsql-performance@postgresql.org X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0.262 tagged_above=0 required=5 tests=AWL=0.261, BAYES_50=0.001 X-Spam-Level: X-Archive-Number: 200709/246 X-Sequence-Number: 26791 pcastet@agematis.com (Patrice Castet) writes: > I wonder if clustering a table improves perfs somehow ? > Any example/ideas about that ? > ref : http://www.postgresql.org/docs/8.2/interactive/sql-cluster.html Sometimes. 1. It compacts the table, which may be of value, particularly if the table is not seeing heavy UPDATE/DELETE traffic. VACUUM and VACUUM FULL do somewhat similar things; if you are using VACUUM frequently enough, this is not likely to have a material effect. 2. It transforms the contents of the table into some specified order, which will improve efficiency for any queries that use that specific ordering. -- output = reverse("moc.enworbbc" "@" "enworbbc") http://linuxdatabases.info/info/emacs.html "You can swear at the keyboard and it won't be offended. It was going to treat you badly anyway" -- Arthur Norman