Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id 29E741337990 for ; Sat, 13 Nov 2010 20:11:18 -0400 (AST) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 47679-01 for ; Sun, 14 Nov 2010 00:11:11 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from www.postnewspapers.com.au (www.postnewspapers.com.au [173.230.139.50]) by mail.postgresql.org (Postfix) with ESMTP id E8E361336971 for ; Sat, 13 Nov 2010 20:11:10 -0400 (AST) Received: from localhost (localhost [127.0.0.1]) by www.postnewspapers.com.au (Postfix) with ESMTP id D66A614A8; Sat, 13 Nov 2010 19:11:10 -0500 (EST) X-Virus-Scanned: amavisd-new at postnewspapers.com.au.com Received: from www.postnewspapers.com.au ([127.0.0.1]) by localhost (www.postnewspapers.com.au [127.0.0.1]) (amavisd-new, port 10024) with LMTP id DHCK2oohM5KB; Sat, 13 Nov 2010 19:11:07 -0500 (EST) Received: from mail.postnewspapers.com.au (ppp171-128.static.internode.on.net [150.101.171.128]) by www.postnewspapers.com.au (Postfix) with ESMTP id B06F919; Sat, 13 Nov 2010 19:11:06 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mail.postnewspapers.com.au (Postfix) with ESMTP id 26592AF21F; Sun, 14 Nov 2010 08:11:05 +0800 (WST) X-Virus-Scanned: Debian amavisd-new at postnewspapers.com.au Received: from mail.postnewspapers.com.au ([127.0.0.1]) by localhost (mail.postnewspapers.com.au [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 4jzdQBqG40Dt; Sun, 14 Nov 2010 08:10:59 +0800 (WST) Received: from [10.1.1.5] (124-169-62-54.dyn.iinet.net.au [124.169.62.54]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "Craig Ringer", Issuer "POST Certificate Authority" (verified OK)) by mail.postnewspapers.com.au (Postfix) with ESMTPSA id AD9E2AF21A; Sun, 14 Nov 2010 08:10:58 +0800 (WST) Message-ID: <4CDF2910.8010105@postnewspapers.com.au> Date: Sun, 14 Nov 2010 08:10:56 +0800 From: Craig Ringer User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc14 Thunderbird/3.1.4 MIME-Version: 1.0 To: mladen.gogala@vmsinfo.com CC: Kyriacos Kyriacou , "pgsql-performance@postgresql.org" Subject: Re: MVCC performance issue References: <8BCBF9DB739F034B87FE7C7D30EAE55C240D4BC8@hqex2k.francoudi.com> <4CDE27D7.7070706@postnewspapers.com.au> <4CDEDB3A.2070606@vmsinfo.com> In-Reply-To: <4CDEDB3A.2070606@vmsinfo.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.91 tagged_above=-10 required=5 tests=BAYES_00=-1.9, T_RP_MATCHES_RCVD=-0.01 X-Spam-Level: X-Archive-Number: 201011/231 X-Sequence-Number: 41255 On 11/14/2010 02:38 AM, Mladen Gogala wrote: > Craig Ringer wrote: >> It sounds like you're describing Oracle-style MVCC, using redo logs. >> >> http://blogs.sybase.com/database/2009/04/mvcc-dispelling-some-oracle-fudunderstanding-the-cost/ >> > Craig, this is an interesting blog page, making some valid points about > the multiversioning vs. locking. The ATM example, however, is > unrealistic and couldn't have happened the way the author describes. Yep, you're quite right. I was using it for its explanation of some of the costs of MVCC as Oracle implements it, because it's surprisingly hard to find explanations/analysis of that with some quick Google searching. I hadn't read beyond that part. I'd be really interested in some *good* writeups of the costs/benefits of the various common mvcc and locking based rdbms implementations. Thanks for posting a breakdown of the issues with that article, lest others be mislead. Appreciated. -- Craig Ringer