X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (mx1.hub.org [200.46.208.251]) by postgresql.org (Postfix) with ESMTP id 534809F9316 for ; Thu, 18 May 2006 13:46:52 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.208.251]) (amavisd-new, port 10024) with ESMTP id 41063-04 for ; Thu, 18 May 2006 13:46:45 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey- Received: from cassarossa.samfundet.no (cassarossa.samfundet.no [129.241.93.19]) by postgresql.org (Postfix) with ESMTP id ADFE49FA4E1 for ; Thu, 18 May 2006 13:46:44 -0300 (ADT) Received: from trofast.sesse.net ([129.241.93.32]) by cassarossa.samfundet.no with esmtp (Exim 4.50) id 1Fgle3-0005Ry-VY for pgsql-performance@postgresql.org; Thu, 18 May 2006 18:46:42 +0200 Received: from sesse by trofast.sesse.net with local (Exim 3.36 #1 (Debian)) id 1Fgle4-0001uE-00 for ; Thu, 18 May 2006 18:46:40 +0200 Date: Thu, 18 May 2006 18:46:40 +0200 From: "Steinar H. Gunderson" To: pgsql-performance@postgresql.org Subject: Re: why is bitmap index chosen for this query? Message-ID: <20060518164640.GA7291@uio.no> Mail-Followup-To: pgsql-performance@postgresql.org References: <20060518155906.GA6909@uio.no> <20060518164123.98856.qmail@web30710.mail.mud.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20060518164123.98856.qmail@web30710.mail.mud.yahoo.com> X-Operating-System: Linux 2.6.16.11 on a x86_64 X-Message-Flag: Outlook? --> http://www.mozilla.org/products/thunderbird/ User-Agent: Mutt/1.5.11+cvs20060403 X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200605/394 X-Sequence-Number: 19181 On Thu, May 18, 2006 at 09:41:23AM -0700, Stephen Byers wrote: > Does the table perchance fit completely into memory, without > effective_cache_size indicating that? > > Don't know the exact way to answer your question, but my initial instinct is "no way." What about the working set? Have you tried running the queries multiple times in a row to see if the results change? It might be that your initial bitmap scan puts all the relevant bits into cache, which will skew the results. /* Steinar */ -- Homepage: http://www.sesse.net/