Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id 99D742E0070 for ; Thu, 27 Mar 2008 14:54:44 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 09149-10 for ; Thu, 27 Mar 2008 14:54:34 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from lists.commandprompt.com (host-159.commandprompt.net [207.173.203.159]) by postgresql.org (Postfix) with ESMTP id 289CF2E008C for ; Thu, 27 Mar 2008 14:54:33 -0300 (ADT) Received: from perhan.alvh.no-ip.org (200-126-66-43.bk5-dsl.surnet.cl [200.126.66.43]) (authenticated bits=0) by lists.commandprompt.com (8.13.8/8.13.8) with ESMTP id m2RHsgjT010809 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 27 Mar 2008 10:54:50 -0700 Received: by perhan.alvh.no-ip.org (Postfix, from userid 1000) id D772B47C45; Thu, 27 Mar 2008 14:54:09 -0300 (CLST) Date: Thu, 27 Mar 2008 14:54:09 -0300 From: Alvaro Herrera To: PFC Cc: Jesper Krogh , pgsql-performance@postgresql.org Subject: Re: "Slow" query or just "Bad hardware"? Message-ID: <20080327175409.GP8764@alvh.no-ip.org> References: <17799.195.41.66.226.1206632068.squirrel@mail.jabbernet.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.0 (lists.commandprompt.com [207.173.203.159]); Thu, 27 Mar 2008 10:54:51 -0700 (PDT) X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200803/508 X-Sequence-Number: 29462 PFC wrote: > Also, sometimes offine TOASTing is evil : > Say you have a forum, you want the posts table to be CLUSTER'ed on > (topic_id, post_id) so displaying 1 page with 30 posts on it uses 1 seek, > not 30 seeks. But CLUSTER doesn't touch the data that has been pushed > offline in the toast table. So, in that case, it can pay (big time > actually) to disable toasting, store the data inline, and benefit from > cluster. This claim is false -- CLUSTER does process the toast table along the main heap. -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support