X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 9A8FFD790E for ; Sat, 27 Aug 2005 12:26:12 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 58452-02 for ; Sat, 27 Aug 2005 15:26:09 +0000 (GMT) Received: from cassarossa.samfundet.no (cassarossa.samfundet.no [129.241.93.19]) by svr1.postgresql.org (Postfix) with ESMTP id 67424D795F for ; Sat, 27 Aug 2005 12:26:06 -0300 (ADT) Received: from trofast.sesse.net ([129.241.93.32]) by cassarossa.samfundet.no with esmtp (Exim 4.50) id 1E92ZI-00065v-Hm for pgsql-performance@postgresql.org; Sat, 27 Aug 2005 17:26:04 +0200 Received: from sesse by trofast.sesse.net with local (Exim 3.36 #1 (Debian)) id 1E92ZH-0006Pr-00 for ; Sat, 27 Aug 2005 17:26:03 +0200 Date: Sat, 27 Aug 2005 17:26:03 +0200 From: "Steinar H. Gunderson" To: pgsql-performance@postgresql.org Subject: Re: Weird performance drop after VACUUM Message-ID: <20050827152603.GF17097@uio.no> Mail-Followup-To: pgsql-performance@postgresql.org References: <1125093859.9329.30.camel@localhost.localdomain> <26745.1125099111@sss.pgh.pa.us> <20050827101945.GA18155@uio.no> <1404.1125155101@sss.pgh.pa.us> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1404.1125155101@sss.pgh.pa.us> X-Operating-System: Linux 2.6.11.8 on a i686 X-Message-Flag: Outlook? --> http://www.mozilla.org/products/thunderbird/ User-Agent: Mutt/1.5.10i X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.015 required=5 tests=[AWL=0.015] X-Spam-Level: X-Archive-Number: 200508/479 X-Sequence-Number: 14226 On Sat, Aug 27, 2005 at 11:05:01AM -0400, Tom Lane wrote: > It could, but it doesn't really have enough information. We don't > currently have any model that some operators are more expensive than > others. IIRC the only sort of reordering the current code will do > in a filter condition list is to push clauses involving sub-SELECTs > to the end. I was more thinking along the lines of reordering "a AND/OR b" to "b AND/OR a" if b has lower selectivity than a. /* Steinar */ -- Homepage: http://www.sesse.net/