Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TsKpG-0004QD-Bw for pgsql-performance@arkaria.postgresql.org; Mon, 07 Jan 2013 22:05:46 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.72) (envelope-from ) id 1TsKpF-00013q-AQ for pgsql-performance@arkaria.postgresql.org; Mon, 07 Jan 2013 22:05:45 +0000 Received: from makus.postgresql.org ([98.129.198.125]) by malur.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TsKpE-00013k-7v for pgsql-performance@postgresql.org; Mon, 07 Jan 2013 22:05:44 +0000 Received: from avasout04.plus.net ([212.159.14.19]) by makus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1TsKpC-0002MX-V4 for pgsql-performance@postgresql.org; Mon, 07 Jan 2013 22:05:43 +0000 Received: from server.barnhouse ([87.112.181.154]) by avasout04 with smtp id lA5g1k0073LGb0f01A5hmP; Mon, 07 Jan 2013 22:05:42 +0000 X-CM-Score: 0.00 X-CNFS-Analysis: v=2.0 cv=XeZXOvF5 c=1 sm=1 a=6uqJNDenEZdphDPviEdeEQ==:17 a=URPhxF5dMbEA:10 a=Hkl_S5PBCtAA:10 a=ihvODaAuJD4A:10 a=8nJEP1OIZ-IA:10 a=EBOSESyhAAAA:8 a=ju9omfPR_8MA:10 a=epTmVMiNAAAA:8 a=K5xTncmcqkWo1GUXS3MA:9 a=wPNLvfGTeEIA:10 a=JE_5qyUpwvkA:10 a=x5lHwUfI_3EA:10 a=Kfi-4MrnAIuQhg7y:21 a=MA8C_xHev1gVgxuH:21 a=6uqJNDenEZdphDPviEdeEQ==:117 Received: from [192.168.0.96] (workstation.barnhouse [192.168.0.96]) by server.barnhouse (Postfix) with ESMTP id 976CF6804D3; Mon, 7 Jan 2013 22:08:52 +0000 (GMT) Message-ID: <50EB46B2.2080503@mansionfamily.plus.com> Date: Mon, 07 Jan 2013 22:05:38 +0000 From: james Reply-To: james@mansionfamily.plus.com User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: =?ISO-8859-1?Q?Fran=E7ois_Beausoleil?= CC: pgsql-performance@postgresql.org Subject: Re: Forcing WAL flush References: <50EB42F6.6080108@mansionfamily.plus.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Pg-Spam-Score: -2.6 (--) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-performance Precedence: bulk Sender: pgsql-performance-owner@postgresql.org > Le 2013-01-07 à 16:49, james a écrit : > >> Is there a way to force a WAL flush so that async commits (from other connections) are flushed, short of actually updating a sacrificial row? >> >> Would be nice to do it without generating anything extra, even if it is something that causes IO in the checkpoint. >> >> Am I right to think that an empty transaction won't do it, and nor will a transaction that is just a NOTIFY? > > Does pg_start_backup() trigger a full WAL flush? > > http://www.postgresql.org/docs/9.2/static/continuous-archiving.html#BACKUP-LOWLEVEL-BASE-BACKUP > http://www.postgresql.org/docs/9.2/static/functions-admin.html#FUNCTIONS-ADMIN-BACKUP-TABLE > > Bye, > François That sounds rather heavyweight! I'm looking for something lightweight - I might call this rather often, as a sort of application-level group commit where I commit async but defer the ack to the requester (or other externally visible side effects) slightly until some other thread forces a flush. -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance