X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [64.117.224.130]) by svr1.postgresql.org (Postfix) with ESMTP id C1EEED1B897 for ; Fri, 29 Aug 2003 03:32:32 +0000 (GMT) Received: from svr1.postgresql.org ([64.117.224.193]) by localhost (neptune.hub.org [64.117.224.130]) (amavisd-new, port 10024) with ESMTP id 76611-04 for ; Fri, 29 Aug 2003 00:32:22 -0300 (ADT) Received: from wolff.to (wolff.to [66.93.249.74]) by svr1.postgresql.org (Postfix) with SMTP id A9A76D1B8CC for ; Fri, 29 Aug 2003 00:32:21 -0300 (ADT) Received: (qmail 5636 invoked by uid 500); 29 Aug 2003 03:38:18 -0000 Date: Thu, 28 Aug 2003 22:38:18 -0500 From: Bruno Wolff III To: Ken Geis Cc: pgsql-performance@postgresql.org Subject: Re: bad estimates / non-scanning aggregates Message-ID: <20030829033818.GA5577@wolff.to> Mail-Followup-To: Ken Geis , pgsql-performance@postgresql.org References: <3F4E99F7.7080604@speakeasy.org> <20030829025109.GD4373@wolff.to> <3F4EBF7E.8020602@speakeasy.org> <20030829030156.GF4373@wolff.to> <3F4EC1D0.5010503@speakeasy.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3F4EC1D0.5010503@speakeasy.org> User-Agent: Mutt/1.5.4i X-Virus-Scanned: by amavisd-new at postgresql.org X-Archive-Number: 200308/462 X-Sequence-Number: 3278 On Thu, Aug 28, 2003 at 20:00:32 -0700, Ken Geis wrote: > Bruno Wolff III wrote: > >>Not according to the optimizer! Plus, this is not guaranteed to return > >>the correct results. > > > >For it to be fast you need an index on (stock_id, price_date) so that > >you can use an index scan. > > I already said that such an index existed. In fact, it is the primary > key of the table. And yes, I *am* analyzed! Your original example didn't actually match that of the table you are showing examples from. In that example the second half of the primary key was the date not the end of the day price. If this is the case for the real table, then that is the reason the distinct on doesn't help.