Received: from maia.hub.org (maia-5.hub.org [200.46.204.29]) by mail.postgresql.org (Postfix) with ESMTP id 9A276B62569 for ; Wed, 1 Jun 2011 09:41:02 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.29]) (amavisd-maia, port 10024) with ESMTP id 42329-04 for ; Wed, 1 Jun 2011 12:40:55 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from sam.nabble.com (sam.nabble.com [216.139.236.26]) by mail.postgresql.org (Postfix) with ESMTP id 5C5B6B62515 for ; Wed, 1 Jun 2011 09:40:55 -0300 (ADT) Received: from [192.168.236.26] (helo=sam.nabble.com) by sam.nabble.com with esmtp (Exim 4.72) (envelope-from ) id 1QRkjH-0001QW-33 for pgsql-hackers@postgresql.org; Wed, 01 Jun 2011 05:40:55 -0700 Date: Wed, 1 Jun 2011 05:40:55 -0700 (PDT) From: panam To: pgsql-hackers@postgresql.org Message-ID: <1306932055085-4445123.post@n5.nabble.com> In-Reply-To: References: <7913.1306900062@sss.pgh.pa.us> Subject: Re: [PERFORM] Hash Anti Join performance degradation MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-0.767 tagged_above=-5 required=5 tests=BAYES_00=-1.9, FREEMAIL_FROM=0.001, T_TO_NO_BRKTS_FREEMAIL=0.01, URI_HEX=1.122 X-Spam-Level: X-Archive-Number: 201106/26 X-Sequence-Number: 188739 Tom Lane-2 wrote: > > It looks like it ought to be an O(N^2) > situation, so the improvement should be noticeable but not amazing. > Hm, the performance was reasonable again when doing a cluster... So I believe this should be more a technical than an algorithmical/complexity issue. Maybe it is the way the hashtable is built and that order makes a difference in that case? In short: Why is clustered data not affected? Regards, panam -- View this message in context: http://postgresql.1045698.n5.nabble.com/Re-PERFORM-Hash-Anti-Join-performance-degradation-tp4443803p4445123.html Sent from the PostgreSQL - hackers mailing list archive at Nabble.com.