Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id A15671337999 for ; Fri, 18 Mar 2011 18:30:32 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 89005-10 for ; Fri, 18 Mar 2011 21:30:25 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from outmail148154.authsmtp.co.uk (outmail148154.authsmtp.co.uk [62.13.148.154]) by mail.postgresql.org (Postfix) with ESMTP id 0B530133655C for ; Fri, 18 Mar 2011 18:30:24 -0300 (ADT) Received: from mail-c193.authsmtp.com (mail-c193.authsmtp.com [62.13.128.118]) by punt6.authsmtp.com (8.14.2/8.14.2/Kp) with ESMTP id p2ILUCvT026218; Fri, 18 Mar 2011 21:30:12 GMT Received: from [192.168.0.3] ([81.5.146.37]) (authenticated bits=0) by mail.authsmtp.com (8.14.2/8.14.2) with ESMTP id p2ILU5Dc030239; Fri, 18 Mar 2011 21:30:05 GMT Subject: Re: Re: [COMMITTERS] pgsql: Efficient transaction-controlled synchronous replication. From: Simon Riggs To: Kevin Grittner Cc: Robert Haas , Markus Wanner , Alvaro Herrera , Andrew Dunstan , Heikki Linnakangas , MARK CALLAGHAN , Aidan Van Dyk , pgsql-hackers In-Reply-To: <4D838723020000250003BAFB@gw.wicourts.gov> References: <4D741441.2090704@dunslane.net> <1299454125.1696.6138.camel@ebony> <4D74896C.5030402@enterprisedb.com> <4D74DDFA.70800@dunslane.net> <4D74E584.7080409@enterprisedb.com> <4D74E9FA.7070202@dunslane.net> <4D74F3AE.9000802@dunslane.net> <4D74FDEC.5040406@enterprisedb.com> <4D74FF15.1070804@dunslane.net> <1299513979-sup-1987@alvh.no-ip.org> <4D832571.5030808@bluegap.ch> <1300457958.18619.13780.camel@ebony> <4D832B4D020000250003BA98@gw.wicourts.gov> <4D837EA2.2070205@enterprisedb.com> <1300465171.18619.15193.camel@ebony> <4D83B02A.5090105@bluegap.ch> <1300476590.18619.18115.camel@ebony> <4D838723020000250003BAFB@gw.wicourts.gov> Content-Type: text/plain; charset="UTF-8" Date: Fri, 18 Mar 2011 21:30:04 +0000 Message-ID: <1300483804.18619.19321.camel@ebony> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit X-Server-Quench: e4b06ffd-51a6-11e0-97bb-002264978518 X-AuthReport-Spam: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-AuthRoute: OCdxZQATClZOTQEd DAteCiN5VAwpPBRK HVkIKg5MJUcNSQVJ NksafxtFaQ1bYFhD HGQLWlVEUlx7WmN/ awwfZQRDZ1RPWwN0 U09WR1pVCwUmQR54 ensbJkpydAVEe3c+ Z0VnX3cVCUAodUAr FBpJEGxXY3phaTUf TUlfJVFJcANIfBlB Y1d3UXIFLwdSbGoL PyYYHB0LBgAXEikH CjImCnc3YHo3MwQH clgaEi42GR9Nais9 LhcnJ1gAfg4NKEw0 KlIqRVMfNVoZDQtC BUZJBCJVb0IQQSEr FwRcWlMFWCdQWSNd CRQ0IxhORFQA X-Authentic-SMTP: 61633235383639.1014:706 X-AuthFastPath: 0 (Was 255) X-AuthVirus-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=1.719 tagged_above=-5 required=5 tests=BAYES_00=-1.9, FS_REPLICA=3.599, RCVD_IN_DNSWL_LOW=-0.7, SARE_SPEC_REPLICA=0.72 X-Spam-Level: * X-Archive-Number: 201103/1174 X-Sequence-Number: 184424 On Fri, 2011-03-18 at 16:24 -0500, Kevin Grittner wrote: > Robert Haas wrote: > > > Since the current solution is intended to support data-loss-free > > failover, but NOT to guarantee a consistent view of the world from > > a SQL level, I doubt it's worth paying any price for this. > > Well, that brings us back to the question of why we would want to > suppress the view of the data on the master until the replica > acknowledges the commit. It *is* committed on the master, we're > just holding off on telling the committer about it until we can > honor the guarantee of replication. If it can be seen on the > replica before the committer get such acknowledgment, why not on the > master? I think the issue is explicit acknowledgement, not visibility. -- Simon Riggs http://www.2ndQuadrant.com/books/ PostgreSQL Development, 24x7 Support, Training and Services