X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by postgresql.org (Postfix) with ESMTP id 1EE469DC86A for ; Tue, 17 Jan 2006 10:56:55 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 46055-08 for ; Tue, 17 Jan 2006 10:56:58 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey- Received: from r1.mycybernet.net (r1.mycybernet.net [209.5.206.8]) by postgresql.org (Postfix) with ESMTP id 9C6FD9DC81E for ; Tue, 17 Jan 2006 10:56:49 -0400 (AST) Received: from 227-54-222-209.mycybernet.net ([209.222.54.227]:34715 helo=phlogiston.dydns.org) by r1.mycybernet.net with esmtp (Exim 4.50 (FreeBSD)) id 1EysGT-000BBI-FQ for pgsql-performance@postgresql.org; Tue, 17 Jan 2006 09:56:53 -0500 Received: by phlogiston.dydns.org (Postfix, from userid 1000) id 602AF4069; Tue, 17 Jan 2006 09:56:49 -0500 (EST) Date: Tue, 17 Jan 2006 09:56:49 -0500 From: Andrew Sullivan To: pgsql-performance@postgresql.org Subject: Re: Autovacuum / full vacuum Message-ID: <20060117145649.GE21092@phlogiston.dyndns.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.076 required=5 tests=[AWL=0.076] X-Spam-Score: 0.076 X-Spam-Level: X-Archive-Number: 200601/236 X-Sequence-Number: 16714 On Tue, Jan 17, 2006 at 11:18:59AM +0100, Michael Riess wrote: > hi, > > I'm curious as to why autovacuum is not designed to do full vacuum. I Because nothing that runs automatically should ever take an exclusive lock on the entire database, which is what VACUUM FULL does. > activity. Increasing the FSM so that even during these bursts most space > would be reused would mean to reduce the available memory for all > other database tasks. I don't believe the hit is enough that you should even notice it. You'd have to post some pretty incredible use cases to show that the tiny loss of memory to FSM is worth (a) an exclusive lock and (b) the loss of efficiency you get from having some preallocated pages in tables. A -- Andrew Sullivan | ajs@crankycanuck.ca The fact that technology doesn't work is no bar to success in the marketplace. --Philip Greenspun