Received: from maia.hub.org (unknown [200.46.208.211]) by mail.postgresql.org (Postfix) with ESMTP id E7086633A60 for ; Wed, 20 Jan 2010 10:09:23 -0400 (AST) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.208.211]) (amavisd-maia, port 10024) with ESMTP id 17319-10 for ; Wed, 20 Jan 2010 14:09:05 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from outmail128066.authsmtp.co.uk (outmail128066.authsmtp.co.uk [62.13.128.66]) by mail.postgresql.org (Postfix) with ESMTP id 25E3F6326B5 for ; Wed, 20 Jan 2010 10:09:12 -0400 (AST) Received: from mail-c194.authsmtp.com (mail-c194.authsmtp.com [62.13.128.121]) by punt10.authsmtp.com (8.14.2/8.14.2/Kp) with ESMTP id o0KE99IH033782; Wed, 20 Jan 2010 14:09:09 GMT Received: from [192.168.0.3] (88-110-172-79.dynamic.dsl.as9105.com [88.110.172.79]) (authenticated bits=0) by mail.authsmtp.com (8.14.2/8.14.2/Kp) with ESMTP id o0KE96QS087629; Wed, 20 Jan 2010 14:09:06 GMT Subject: Re: Small locking bugs in hs From: Simon Riggs To: Andres Freund Cc: pgsql-hackers@postgresql.org, Robert Haas In-Reply-To: <201001201413.09953.andres@anarazel.de> References: <200912272012.32556.andres@anarazel.de> <201001200447.47382.andres@anarazel.de> <1263988780.4043.2046.camel@ebony> <201001201413.09953.andres@anarazel.de> Content-Type: text/plain Date: Wed, 20 Jan 2010 14:09:05 +0000 Message-Id: <1263996545.4043.2633.camel@ebony> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit X-Server-Quench: 5f3a334f-05cd-11df-80b9-0022640b883e X-Report-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCdxZQATClZOTQEd DAteCiN5VAwpPBRK HVkIKg5MJUcNSQVJ NksadRtFagVbZ1hf HGQLWlREUVl7WWp/ awwfZQ1DY0tOQQRt UlZOS01XHAJ3AVJe BmVrWx8TFAVOf3hy bAhhXXJaEkEsdhd+ QUoCCG0DNjN9aWFL Bl1Qd1FdbQNKfB1D blAtXHsONCtlM3Bw LC8aFBMcBw5qYB9Q SwUJZVYVSkUKGDF0 TQ0NBn0uGwUFXE0A X-Authentic-SMTP: 61633235383639.1015:706/Kp X-AuthFastPath: 255 X-Virus-Status: No virus detected - but ensure you scan with your own anti-virus system. X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.666 tagged_above=-10 required=5 tests=AWL=-0.556, BAYES_05=-1.11 X-Spam-Level: X-Archive-Number: 201001/1970 X-Sequence-Number: 155191 On Wed, 2010-01-20 at 14:13 +0100, Andres Freund wrote: > I do understand it correctly that in CancelVirtualTransaction > LW_SHARED is > taken only so that another transaction can finish during that time? We're canceling one specific vxid, so no need to block other snapshots from being taken. Read only queries don't take ProcArrayLock when they complete and the Startup process is the only process to record xact completion during recovery. -- Simon Riggs www.2ndQuadrant.com