Received: from maia.hub.org (unknown [200.46.204.183]) by mail.postgresql.org (Postfix) with ESMTP id 0321B634B43 for ; Wed, 17 Mar 2010 11:27:21 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 24584-05 for ; Wed, 17 Mar 2010 14:27:09 +0000 (UTC) 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 mail.postgresql.org (Postfix) with ESMTP id 6642879786B for ; Wed, 17 Mar 2010 11:27:10 -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 o2HER4o5027895; Wed, 17 Mar 2010 10:27:05 -0400 (EDT) To: Greg Stark cc: Pierre C , Alvaro Herrera , Dave Crooke , pgsql-performance@postgresql.org Subject: Re: Block at a time ... In-reply-to: <407d949e1003170252y72d223c3kcc18266140a60997@mail.gmail.com> References: <20100317001405.GL3037@alvh.no-ip.org> <407d949e1003170252y72d223c3kcc18266140a60997@mail.gmail.com> Comments: In-reply-to Greg Stark message dated "Wed, 17 Mar 2010 09:52:13 -0000" Date: Wed, 17 Mar 2010 10:27:04 -0400 Message-ID: <27894.1268836024@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-2.599 tagged_above=-10 required=5 tests=BAYES_00=-2.599 X-Spam-Level: X-Archive-Number: 201003/196 X-Sequence-Number: 38021 Greg Stark writes: > I think we need posix_fallocate(). The problem with posix_fallocate (other than questionable portability) is that it doesn't appear to guarantee anything at all about what is in the space it allocates. Worst case, we might find valid-looking Postgres data there (eg, because a block was recycled from some recently dropped table). If we have to write something anyway to zero the space, what's the point? regards, tom lane