Received: from localhost (maia-1.hub.org [200.46.204.191]) by postgresql.org (Postfix) with ESMTP id D2A249F9C35 for ; Wed, 6 Dec 2006 09:31:31 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.191]) (amavisd-new, port 10024) with ESMTP id 99360-08 for ; Wed, 6 Dec 2006 09:31:14 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from cassarossa.samfundet.no (cassarossa.samfundet.no [129.241.93.19]) by postgresql.org (Postfix) with ESMTP id 9F58B9F93E5 for ; Wed, 6 Dec 2006 09:31:12 -0400 (AST) Received: from trofast.sesse.net ([129.241.93.32]) by cassarossa.samfundet.no with esmtp (Exim 4.50) id 1Grwre-0001qQ-8p for pgsql-performance@postgresql.org; Wed, 06 Dec 2006 14:31:10 +0100 Received: from sesse by trofast.sesse.net with local (Exim 3.36 #1 (Debian)) id 1GrwrY-0002Uu-00 for ; Wed, 06 Dec 2006 14:31:04 +0100 Date: Wed, 6 Dec 2006 14:31:04 +0100 From: "Steinar H. Gunderson" To: pgsql-performance@postgresql.org Subject: Re: Locking in PostgreSQL? Message-ID: <20061206133104.GA9537@uio.no> Mail-Followup-To: pgsql-performance@postgresql.org References: <1165388652.6396.1.camel@panoramix> <30BD1C9A-1664-4290-B343-0FB1FEBA7B53@fastcrypt.com> <4ED560E4-3484-43BA-99BB-18888D968F74@fastcrypt.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4ED560E4-3484-43BA-99BB-18888D968F74@fastcrypt.com> X-Operating-System: Linux 2.6.19 on a x86_64 X-Message-Flag: Outlook? --> http://www.mozilla.org/products/thunderbird/ User-Agent: Mutt/1.5.13 (2006-08-11) X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200612/114 X-Sequence-Number: 22170 On Wed, Dec 06, 2006 at 08:26:45AM -0500, Dave Cramer wrote: > Apparently I've completely misunderstood MVCC then.... My > understanding is that unless you do a select ... for update then > update the rows will not be locked . The discussion was about updates, not selects. Selects do not in general lock (except for ... for update, as you say). To (partially) answer the original question: The number of columns updated does not matter for the locking situation. /* Steinar */ -- Homepage: http://www.sesse.net/