Received: from localhost (unknown [200.46.204.191]) by postgresql.org (Postfix) with ESMTP id 546E12E352C for ; Thu, 13 Dec 2007 17:39:57 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.191]) (amavisd-maia, port 10024) with ESMTP id 74840-10 for ; Thu, 13 Dec 2007 17:39:51 -0400 (AST) Received: from outmail129173.authsmtp.com (outmail129173.authsmtp.com [62.13.129.173]) by postgresql.org (Postfix) with ESMTP id DD25F2E350A for ; Thu, 13 Dec 2007 17:39:49 -0400 (AST) Received: from outmail128183.authsmtp.com (outmail128183.authsmtp.com [62.13.128.183]) by punt3.authsmtp.com (8.13.8/8.13.8/Kp) with ESMTP id lBDLdm62058666; Thu, 13 Dec 2007 21:39:48 GMT Received: from [192.168.0.3] (85-211-24-246.dyn.gotadsl.co.uk [85.211.24.246]) (authenticated bits=0) by mail.authsmtp.com (8.13.8/8.13.8/Kp) with ESMTP id lBDLdkM3074246; Thu, 13 Dec 2007 21:39:46 GMT Subject: Re: Heavy write activity on first vacuum of fresh TOAST data From: Simon Riggs To: Kevin Grittner Cc: pgsql-performance@postgresql.org In-Reply-To: <47614D86.EE98.0025.0@wicourts.gov> References: <4760FF69.EE98.0025.0@wicourts.gov> <1197562283.4255.1829.camel@ebony.site> <47611B9D.EE98.0025.0@wicourts.gov> <1197569564.4255.1855.camel@ebony.site> <47614D86.EE98.0025.0@wicourts.gov> Content-Type: text/plain Date: Thu, 13 Dec 2007 21:40:10 +0000 Message-Id: <1197582010.4255.1912.camel@ebony.site> Mime-Version: 1.0 X-Mailer: Evolution 2.8.2 Content-Transfer-Encoding: 7bit X-Server-Quench: ece8cdf7-a9c3-11dc-814e-001185d377ca X-AuthRoute: OCdxZQATClZOTQEd DAteCiNZVAwpPBRK HVkIKg5MJUcNSQVJ NksadBtFaQZbaVxS HGQLW1NEUlx7Wmp/ bw0fZQBDYEtPQQdu TkpNRE1QERpoT0Bz cmJKCWRxdwJCenp2 K0dmXngVCRcvfRUp FElJRGRVZnphaTRM TUhZc1ZJcANLfxdA PlN4UyBcLwdSbGoL JyIJERcLGAAXCClc XBBFMkgTXUtDFzUg Rg4DASRnGktNSSQp NABuNFcXAVsUekI8 eVU7VEkYeyM1IzZi fSBBCTNQT2wg X-Authentic-SMTP: 61633235383639.squirrel.dmpriest.net.uk:787/Kp X-Report-SPAM: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200712/204 X-Sequence-Number: 28020 On Thu, 2007-12-13 at 15:19 -0600, Kevin Grittner wrote: > >>> On Thu, Dec 13, 2007 at 12:12 PM, in message > <1197569564.4255.1855.camel@ebony.site>, Simon Riggs > wrote: > > On Thu, 2007-12-13 at 11:46 -0600, Kevin Grittner wrote: > >> If the hint bit changes are written to the WAL ... > > > > They're not. > > So one would expect a write-intensive initial vacuum after a > PITR-style recovery? Very perceptive. I was just thinking about that myself. An interesting issue when running with full_page_writes off. > What impact would lack of the hint bits have until a vacuum? Vacuum isn't important here. Its the first idiot to read the data that gets hit. -- Simon Riggs 2ndQuadrant http://www.2ndQuadrant.com