Received: from maia.hub.org (maia-5.hub.org [200.46.204.29]) by mail.postgresql.org (Postfix) with ESMTP id C45CFB5F8A4 for ; Mon, 6 Jun 2011 20:02:39 -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 36304-03 for ; Mon, 6 Jun 2011 23:02:32 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by mail.postgresql.org (Postfix) with ESMTP id 0C7BAB5F5D0 for ; Mon, 6 Jun 2011 20:02:31 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.2/8.14.2) with ESMTP id p56N2NIE014956; Mon, 6 Jun 2011 19:02:23 -0400 (EDT) To: Josh Berkus cc: pgsql-performance@postgresql.org Subject: Re: 8.4/9.0 simple query performance regression In-reply-to: <4DED4A87.7000901@agliodbs.com> References: <4DED4A87.7000901@agliodbs.com> Comments: In-reply-to Josh Berkus message dated "Mon, 06 Jun 2011 14:45:43 -0700" Date: Mon, 06 Jun 2011 19:02:23 -0400 Message-ID: <14955.1307401343@sss.pgh.pa.us> From: Tom Lane 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: 201106/39 X-Sequence-Number: 43972 Josh Berkus writes: > Just got this simple case off IRC today: > [ hashed versus non-hashed subplan ] > I'm at a bit of a loss as to what's happening here. Possibly work_mem is smaller in the second installation? (If I'm counting on my fingers right, you'd need a setting of at least a couple MB to let it choose a hashed subplan for this case.) regards, tom lane