Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1UOP3v-0000Oj-LE for pgsql-performance@arkaria.postgresql.org; Sat, 06 Apr 2013 09:05:27 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.72) (envelope-from ) id 1UOP3u-0001f2-RX for pgsql-performance@arkaria.postgresql.org; Sat, 06 Apr 2013 09:05:26 +0000 Received: from makus.postgresql.org ([2001:4800:7903:4::125]) by malur.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1UOP3t-0001ew-IN for pgsql-performance@postgresql.org; Sat, 06 Apr 2013 09:05:25 +0000 Received: from smtp04.smtpout.orange.fr ([80.12.242.126] helo=smtp.smtpout.orange.fr) by makus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1UOP3l-0008RP-VJ for pgsql-performance@postgresql.org; Sat, 06 Apr 2013 09:05:25 +0000 Received: from axege.com ([82.127.232.162]) by mwinf5d27 with ME id LZ5G1l00H3WtTCJ03Z5GuK; Sat, 06 Apr 2013 11:05:16 +0200 Received: from localhost (localhost [127.0.0.1]) by axege.com (Postfix) with ESMTP id 3737F43DE03 for ; Sat, 6 Apr 2013 11:05:16 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at myhostname="axege.com." Received: from axege.com ([127.0.0.1]) by localhost (axege.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id OlgIxFhoZkDs for ; Sat, 6 Apr 2013 11:05:15 +0200 (CEST) Received: from [10.0.1.8] (lns-bzn-48f-81-56-219-232.adsl.proxad.net [81.56.219.232]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by axege.com (Postfix) with ESMTPSA id C620E43DE02 for ; Sat, 6 Apr 2013 11:05:12 +0200 (CEST) Message-ID: <515FE547.3010301@axege.com> Date: Sat, 06 Apr 2013 11:05:11 +0200 From: Franck Routier User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130404 Thunderbird/17.0.5 MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: What happens between end of explain analyze and end of query execution ? References: <515D92BF.5000309@axege.com> <515D9FC5.7030105@axege.com> <18910.1365092713@sss.pgh.pa.us> <515DCB34.6040801@axege.com> <6354.1365102532@sss.pgh.pa.us> <515ED7BC.40907@axege.com> <4113.1365171448@sss.pgh.pa.us> In-Reply-To: <4113.1365171448@sss.pgh.pa.us> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms030703090504070303080901" X-Pg-Spam-Score: -1.1 (-) 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 Ceci est un message signé cryptographiquement au format MIME. --------------ms030703090504070303080901 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Le 05/04/2013 16:17, Tom Lane a =E9crit : > What have you got the statistics targets set to in this database? Ok, the problem definitely comes from the default_statistics_target=20 which is obviously too high on the database. I have experimented with explain on queries with another set of 4 joined = tables. In my first attempt, explain took more than 4 seconds (!) Then I have set default_statistics_target to 100 and analyzed the 4=20 tables. Explain took a few ms. Restored default_statistics_target to 5000, analyzed again. Explain took = 1.8 seconds. So, I seem to have two related problems: statistics are somewhat bloated = (as re-analyzing with same target takes the explain time from 4 sec down = to 1.8 sec). And the target is far too high (as default target value take analyse=20 down to a few ms). Now... can someone help me understand what happens ? Where can I look=20 (in pg_stats ?) to see the source of the problem ? maybe a column with a = huge list of different values the palnner has to parse ? 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