Received: from localhost (unknown [200.46.204.183]) by developer.postgresql.org (Postfix) with ESMTP id AB55D2E0032 for ; Mon, 26 May 2008 12:37:21 -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 75479-01 for ; Mon, 26 May 2008 12:37:03 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by developer.postgresql.org (Postfix) with ESMTP id C4A042E0052 for ; Mon, 26 May 2008 12:37:03 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.2/8.14.2) with ESMTP id m4QFavuV021815; Mon, 26 May 2008 11:36:57 -0400 (EDT) To: "Heikki Linnakangas" cc: "Decibel!" , "Greg Smith" , pgsql-performance@postgresql.org Subject: Re: I/O on select count(*) In-reply-to: <483AB515.5050201@enterprisedb.com> 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> Comments: In-reply-to "Heikki Linnakangas" message dated "Mon, 26 May 2008 14:03:17 +0100" Date: Mon, 26 May 2008 11:36:57 -0400 Message-ID: <21814.1211816217@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200805/335 X-Sequence-Number: 30303 "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. regards, tom lane