Received: from localhost (maia-5.hub.org [200.46.204.182]) by postgresql.org (Postfix) with ESMTP id 9CABD9FB90C; Mon, 5 Mar 2007 12:02:48 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.182]) (amavisd-new, port 10024) with ESMTP id 04965-02-2; Mon, 5 Mar 2007 12:02:35 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id 08A569FB43A; Mon, 5 Mar 2007 12:02:34 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.6/8.13.6) with ESMTP id l25G2Vt8018983; Mon, 5 Mar 2007 11:02:31 -0500 (EST) To: ITAGAKI Takahiro cc: pgsql-hackers@postgresql.org, pgsql-patches@postgresql.org Subject: Re: Aggressive freezing in lazy-vacuum In-reply-to: <20070305182401.C4BC.ITAGAKI.TAKAHIRO@oss.ntt.co.jp> References: <20070227141958.638D.ITAGAKI.TAKAHIRO@oss.ntt.co.jp> <20070227170613.GK29041@nasby.net> <20070305182401.C4BC.ITAGAKI.TAKAHIRO@oss.ntt.co.jp> Comments: In-reply-to ITAGAKI Takahiro message dated "Mon, 05 Mar 2007 19:14:34 +0900" Date: Mon, 05 Mar 2007 11:02:31 -0500 Message-ID: <18982.1173110551@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0.061 tagged_above=0 required=5 tests=AWL, BAYES_50, SPF_HELO_PASS, SPF_PASS X-Spam-Level: X-Archive-Number: 200703/277 X-Sequence-Number: 99761 ITAGAKI Takahiro writes: > This is a stand-alone patch for aggressive freezing. I'll propose > to use OldestXmin instead of FreezeLimit as the freeze threshold > in the circumstances below: I think it's a really bad idea to freeze that aggressively under any circumstances except being told to (ie, VACUUM FREEZE). When you freeze, you lose history information that might be needed later --- for forensic purposes if nothing else. You need to show a fairly amazing performance gain to justify that, and I don't think you can. regards, tom lane