Received: from makus.postgresql.org (makus.postgresql.org [98.129.198.125]) by mail.postgresql.org (Postfix) with ESMTP id 68CC2914537 for ; Thu, 1 Dec 2011 14:02:11 -0400 (AST) Received: from smtp.01.com ([216.115.88.169]) by makus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1RWAxX-0002RI-5w for pgsql-performance@postgresql.org; Thu, 01 Dec 2011 18:02:11 +0000 Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp-out-1.01.com (Postfix) with ESMTP id C6EE69D04A9 for ; Thu, 1 Dec 2011 12:01:58 -0600 (CST) X-Virus-Scanned: amavisd-new at smtp-out-1.01.com Received: from smtp.01.com ([127.0.0.1]) by localhost (smtp-out-1.01.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id CBm6QatTRxN2 for ; Thu, 1 Dec 2011 12:01:58 -0600 (CST) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp-out-1.01.com (Postfix) with ESMTP id 9F0A29D0542 for ; Thu, 1 Dec 2011 12:01:58 -0600 (CST) Received: from Sidney-Stratton.local (70-36-143-92.dsl.dynamic.sonic.net [70.36.143.92]) by smtp-out-1.01.com (Postfix) with ESMTPSA id 5CF479D06F7 for ; Thu, 1 Dec 2011 12:01:58 -0600 (CST) Message-ID: <4ED7C115.4010607@agliodbs.com> Date: Thu, 01 Dec 2011 10:01:57 -0800 From: Josh Berkus Organization: PostgreSQL Experts Inc. User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.2.24) Gecko/20111103 Lightning/1.0b2 Thunderbird/3.1.16 MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: vacuum internals and performance affect References: <1322586733308-5033043.post@n5.nabble.com> <4ED69DCD.5000806@agliodbs.com> <1322688860656-5036800.post@n5.nabble.com> In-Reply-To: <1322688860656-5036800.post@n5.nabble.com> X-Enigmail-Version: 1.1.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Pg-Spam-Score: -1.9 (-) X-Archive-Number: 201112/3 X-Sequence-Number: 45803 MirrorX, > so when a transaction is still open from a while back (according to the > transactionID), no 'new dead' tuples can be marked as re-usable space for > new rows, right? by 'new dead' i mean that for example there is a > transaction running from 10.00am(with a specific transactionID). when i > delete rows at 11.00am these are the ones i am referring to. With the understanding that what we're actually checking is snapshots (which are not completely linear) and not timestamps, yes, that's a good simplification for what happens. > but, for these rows, the 'deleted' ones. does vacuum do anything at all at > that time? and if so, what is it? thx in advance No, it does nothing. What would it do? -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com