Received: from localhost (maia-2.hub.org [200.46.204.187]) by postgresql.org (Postfix) with ESMTP id F04F99FB3A7 for ; Wed, 31 Jan 2007 01:55:37 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.187]) (amavisd-new, port 10024) with ESMTP id 63497-04 for ; Wed, 31 Jan 2007 01:55:22 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id 5B8789FB368 for ; Wed, 31 Jan 2007 01:55:35 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.6/8.13.6) with ESMTP id l0V5tJn7016279; Wed, 31 Jan 2007 00:55:19 -0500 (EST) To: Alvaro Herrera cc: Gregory Stark , Luke Lonergan , Chad Wagner , Simon Riggs , Igor Lobanov , Richard Huxton , pgsql-performance@postgresql.org Subject: Re: Querying distinct values from a large table In-reply-to: <20070130170443.GJ2303@alvh.no-ip.org> References: <87d54wmpvd.fsf@stark.xeocode.com> <20070130170443.GJ2303@alvh.no-ip.org> Comments: In-reply-to Alvaro Herrera message dated "Tue, 30 Jan 2007 14:04:43 -0300" Date: Wed, 31 Jan 2007 00:55:19 -0500 Message-ID: <16278.1170222919@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200701/442 X-Sequence-Number: 23043 Alvaro Herrera writes: > Gregory Stark wrote: >> (Incidentally I'm not sure where 2-5x comes from. It's entirely dependant on >> your data distribution. It's not hard to come up with distributions where it's >> 1000x as fast and others where there's no speed difference.) > So the figure is really "1-1000x"? I bet this one is more impressive in > PHB terms. Luke has a bad habit of quoting numbers that are obviously derived from narrow benchmarking scenarios as Universal Truths, rather than providing the context they were derived in. I wish he'd stop doing that... regards, tom lane