Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1X1iMp-0005Ly-SK for pgsql-performance@arkaria.postgresql.org; Mon, 30 Jun 2014 20:39:59 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.80) (envelope-from ) id 1X1iMp-0006tT-2O for pgsql-performance@arkaria.postgresql.org; Mon, 30 Jun 2014 20:39:59 +0000 Received: from makus.postgresql.org ([2001:4800:1501:1::229]) by malur.postgresql.org with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1X1iMo-0006tN-4Q for pgsql-performance@postgresql.org; Mon, 30 Jun 2014 20:39:58 +0000 Received: from sss.pgh.pa.us ([66.207.139.130]) by makus.postgresql.org with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1X1iMh-0000rr-1w for pgsql-performance@postgresql.org; Mon, 30 Jun 2014 20:39:56 +0000 Received: from sss1.sss.pgh.pa.us (localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.4/8.14.4) with ESMTP id s5UKdiss021475; Mon, 30 Jun 2014 16:39:44 -0400 From: Tom Lane To: Jeff Frost cc: Andres Freund , Matheus de Oliveira , Soni M , Heikki Linnakangas , pgsql-performance Subject: Re: Postgres Replaying WAL slowly In-reply-to: <943ECC8E-8899-422E-937C-50DE20E1F7AC@pgexperts.com> References: <20140630171416.GK21422@awork2.anarazel.de> <8DA8C140-818D-4184-AAE6-CA37278B983C@pgexperts.com> <20140630183908.GT26930@awork2.anarazel.de> <0A7B96D4-DB10-49A8-A268-F28960F2E137@pgexperts.com> <20300.1404156750@sss.pgh.pa.us> <20140630201523.GV26930@awork2.anarazel.de> <943ECC8E-8899-422E-937C-50DE20E1F7AC@pgexperts.com> Comments: In-reply-to Jeff Frost message dated "Mon, 30 Jun 2014 13:21:08 -0700" Date: Mon, 30 Jun 2014 16:39:44 -0400 Message-ID: <21474.1404160784@sss.pgh.pa.us> X-Pg-Spam-Score: -1.9 (-) 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 Jeff Frost writes: > On Jun 30, 2014, at 1:15 PM, Andres Freund wrote: >> So these are probably relations created in uncommitted >> transactions. Possibly ON COMMIT DROP temp tables? > That would make sense. There are definitely quite a few of those being used. Uh-huh. I doubt that the mechanism that handles propagation of AccessExclusiveLocks to the standby is smart enough to ignore locks on temp tables :-( > Another item of note is the system catalogs are quite bloated: > Would that cause the replica to spin on StandbyReleaseLocks? AFAIK, no. It's an unsurprising consequence of heavy use of short-lived temp tables though. So it seems like we have a candidate explanation. I'm a bit surprised that StandbyReleaseLocks would get this slow if there are only a dozen AccessExclusiveLocks in place at any one time, though. Perhaps that was a low point and there are often many more? regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance