Received: from localhost (unknown [200.46.204.182]) by postgresql.org (Postfix) with ESMTP id 639CE9F9AF1 for ; Mon, 24 Sep 2007 16:51:29 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.182]) (amavisd-maia, port 10024) with ESMTP id 03654-07 for ; Mon, 24 Sep 2007 16:51:26 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by postgresql.org (Postfix) with ESMTP id E3AF39F9AEC for ; Mon, 24 Sep 2007 16:51:28 -0300 (ADT) Received: from news.hub.org (news.hub.org [200.46.204.72]) by news.hub.org (8.14.1/8.14.1) with ESMTP id l8OJpQtH014778 for ; Mon, 24 Sep 2007 16:51:26 -0300 (ADT) (envelope-from news@news.hub.org) Received: (from news@localhost) by news.hub.org (8.14.1/8.14.1/Submit) id l8OJbBEr010487 for pgsql-performance@postgresql.org; Mon, 24 Sep 2007 16:37:11 -0300 (ADT) (envelope-from news) From: "Carlo Stonebanks" X-Newsgroups: pgsql.performance Subject: Acceptable level of over-estimation? Date: Mon, 24 Sep 2007 15:37:41 -0400 Organization: Hub.Org Networking Services Lines: 7 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit X-Complaints-To: usenet@news.hub.org X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Windows Mail 6.0.6000.16480 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6000.16480 To: pgsql-performance@postgresql.org X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200709/431 X-Sequence-Number: 26976 Is there a rule of thumb about when the planner's row estimates are too high? In particular, when should I be concerned that planner's estimated number of rows estimated for a nested loop is off? By a factor of 10? 100? 1000? Carlo