Received: from localhost (unknown [200.46.204.183]) by developer.postgresql.org (Postfix) with ESMTP id D8B722E0050 for ; Tue, 27 May 2008 17:52:40 -0300 (ADT) Received: from developer.postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 12186-03 for ; Tue, 27 May 2008 17:52:04 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from outmail136170.authsmtp.com (outmail136170.authsmtp.com [62.13.136.170]) by developer.postgresql.org (Postfix) with ESMTP id 361472E004A for ; Tue, 27 May 2008 17:52:06 -0300 (ADT) Received: from mail-c188.authsmtp.com (mail-c188.authsmtp.com [62.13.128.25]) by punt6.authsmtp.com (8.14.2/8.14.2/Kp) with ESMTP id m4RKpw0K063186; Tue, 27 May 2008 21:51:58 +0100 (BST) Received: from [192.168.0.3] (85-211-226-243.dyn.gotadsl.co.uk [85.211.226.243]) (authenticated bits=0) by mail.authsmtp.com (8.14.2/8.14.2/Kp) with ESMTP id m4RKpv0J019312; Tue, 27 May 2008 21:51:57 +0100 (BST) Subject: Re: I/O on select count(*) From: Simon Riggs To: Tom Lane Cc: Heikki Linnakangas , Decibel! , Greg Smith , pgsql-performance@postgresql.org In-Reply-To: <21814.1211816217@sss.pgh.pa.us> References: <920841.71690.qm@web44808.mail.sp1.yahoo.com> <482B1D5F.EE98.0025.0@wicourts.gov> <20080515020553.GN9838@alvh.no-ip.org> <20080515155232.GC8221@alvh.no-ip.org> <20080516201528.GJ13061@alvh.no-ip.org> <18382.1210992302@sss.pgh.pa.us> <483AB515.5050201@enterprisedb.com> <21814.1211816217@sss.pgh.pa.us> Content-Type: text/plain Date: Tue, 27 May 2008 21:54:26 +0100 Message-Id: <1211921666.4489.261.camel@ebony.site> Mime-Version: 1.0 X-Mailer: Evolution 2.12.0 Content-Transfer-Encoding: 7bit X-Server-Quench: bf10485f-2c2e-11dd-aecc-001871e930f4 X-AuthRoute: OCdxZQATClZOTQEd DAteCiNZVAwpPBRK HVkIKg5MJUcNSQVJ NksacxtFagJbYFhI HGQLW1xEUlx7XGJ/ bg0fZQBDYEtPQQdo VlZLRlFNFgBqBAMB SEMaMGIyMQU8eH95 ZkdgEHFdXE00JxB8 QkpcEDsbZzRiPX0e URQMalIBI1BXfh9E Yld+AXoOYTMDKBg1 TUcABx0LExJlDREd Y0YqZVUUCV0GGjM3 W1gJGigpAQ1HBk0g X-Authentic-SMTP: 61633235383639.cat.dmpriest.net.uk:1045/Kp X-Report-SPAM: If SPAM / abuse - report it at: http://www.authsmtp.com/abuse 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-Archive-Number: 200805/349 X-Sequence-Number: 30317 On Mon, 2008-05-26 at 11:36 -0400, Tom Lane wrote: > "Heikki Linnakangas" writes: > > Decibel! wrote: > >> Also, Simon and Tom had an idea at PGCon: Don't set hint-bits in the > >> back-end if the page isn't already dirty. > > > Or even better: set the hint-bits, but don't dirty the page. > > Which in fact is what Simon suggested, not the other thing. Just raised this on -hackers, BTW. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support