X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 0FA0552A13 for ; Wed, 29 Jun 2005 12:27:54 -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 03334-03 for ; Wed, 29 Jun 2005 15:27:49 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id 59ADA529F4 for ; Wed, 29 Jun 2005 12:27:48 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.1/8.13.1) with ESMTP id j5TFRl3t009799; Wed, 29 Jun 2005 11:27:47 -0400 (EDT) To: emil@baymountain.com Cc: pgsql-performance@postgresql.org Subject: Re: Exclusive lock question In-reply-to: <200506291108.28516.emil@baymountain.com> References: <200506291108.28516.emil@baymountain.com> Comments: In-reply-to Emil Briggs message dated "Wed, 29 Jun 2005 11:08:28 -0400" Date: Wed, 29 Jun 2005 11:27:47 -0400 Message-ID: <9798.1120058867@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.006 tagged_above=0 required=5 tests=AWL X-Spam-Level: X-Archive-Number: 200506/589 X-Sequence-Number: 13226 Emil Briggs writes: > When I see the slowdowns there are hundreds of these with no entry for > relation or database. Any ideas what is being locked in this case? Per the pg_locks documentation: Every transaction holds an exclusive lock on its transaction ID for its entire duration. If one transaction finds it necessary to wait specifically for another transaction, it does so by attempting to acquire share lock on the other transaction ID. That will succeed only when the other transaction terminates and releases its locks. regards, tom lane