X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 13EFC529C8 for ; Wed, 6 Jul 2005 19:34:08 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 99288-02 for ; Wed, 6 Jul 2005 22:34:04 +0000 (GMT) Received: from megazone.bigpanda.com (megazone.bigpanda.com [64.147.171.210]) by svr1.postgresql.org (Postfix) with ESMTP id 940E6529C3 for ; Wed, 6 Jul 2005 19:34:03 -0300 (ADT) Received: by megazone.bigpanda.com (Postfix, from userid 1001) id 6BF3C353CD; Wed, 6 Jul 2005 15:34:03 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by megazone.bigpanda.com (Postfix) with ESMTP id 6A7DC350DB; Wed, 6 Jul 2005 15:34:03 -0700 (PDT) Date: Wed, 6 Jul 2005 15:34:03 -0700 (PDT) From: Stephan Szabo To: Dario Cc: pgsql-performance@postgresql.org Subject: Re: join and query planner In-Reply-To: Message-ID: <20050706152750.V50953@megazone.bigpanda.com> References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.006 tagged_above=0 required=5 tests=AWL X-Spam-Level: X-Archive-Number: 200507/55 X-Sequence-Number: 13296 On Wed, 6 Jul 2005, Dario wrote: > > (first at all, sorry for my english) > Hi. > - Does "left join" restrict the order in which the planner must join > tables? I've read about join, but i'm not sure about left join... Yes. Reordering the outer joins can change the results in some cases which would be invalid. Before we can change the ordering behavior, we really need to know under what conditions it is safe to do the reordering.