Received: from localhost (maia-5.hub.org [200.46.204.182]) by postgresql.org (Postfix) with ESMTP id 350099FBDF0; Fri, 30 Mar 2007 07:19:09 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.182]) (amavisd-maia, port 10024) with ESMTP id 39067-01; Fri, 30 Mar 2007 07:19:01 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from mail01.enterprisedb.com (mail01.enterprisedb.com [63.246.7.168]) by postgresql.org (Postfix) with ESMTP id 438DA9FBDED; Fri, 30 Mar 2007 07:19:05 -0300 (ADT) thread-index: AcdytN+gfWN70+ZCQd2LCpBs/hOhig== Received: from [192.168.0.22] ([85.211.147.35]) by mail01.enterprisedb.com with Microsoft SMTPSVC(6.0.3790.1830); Fri, 30 Mar 2007 06:19:15 -0400 Content-Class: urn:content-classes:message Importance: normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.2826 Subject: Re: [PATCHES] Full page writes improvement, code update From: "Simon Riggs" To: "Zeugswetter Andreas ADI SD" Cc: "Koichi Suzuki" , , , In-Reply-To: References: <460886E8.6040907@oss.ntt.co.jp> <4609CAC3.7060008@oss.ntt.co.jp> <1175072848.4386.323.camel@silverbirch.site> <200703291145.28574.josh@agliodbs.com> <1175200117.4386.616.camel@silverbirch.site> <460C611E.6090800@oss.ntt.co.jp> Content-Type: text/plain; charset="iso-8859-1" Date: Fri, 30 Mar 2007 11:15:16 +0100 Message-ID: <1175249717.4386.716.camel@silverbirch.site> MIME-Version: 1.0 X-Mailer: Evolution 2.6.0 Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 30 Mar 2007 10:19:15.0671 (UTC) FILETIME=[DE8B7670:01C772B4] X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200703/1761 X-Sequence-Number: 101245 On Fri, 2007-03-30 at 10:22 +0200, Zeugswetter Andreas ADI SD wrote: > > Without a switch, because both full page writes and > > corresponding logical log is included in WAL, this will > > increase WAL size slightly > > (maybe about five percent or so). If everybody is happy > > with this, we > > don't need a switch. > > Sorry, I still don't understand that. What is the "corresponding logical > log" ? > It seems to me, that a full page WAL record has enough info to produce a > > dummy LSN WAL entry. So insead of just cutting the full page wal record > you > could replace it with a LSN WAL entry when archiving the log. > > Then all that is needed is the one flag, no extra space ? The full page write is required for crash recovery, but that isn't required during archive recovery because the base backup provides the safe base. Archive recovery needs the normal xlog record, which in some cases has been optimised away because the backup block is present, since the full block already contains the changes. If you want to remove the backup blocks, you need to put back the information that was optimised away, otherwise you won't be able to do the archive recovery correctly. Hence a slight increase in WAL volume to allow it to be compressed does make sense. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com