X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id ECB61D6FEB for ; Fri, 26 Aug 2005 17:46:17 -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 86282-07 for ; Fri, 26 Aug 2005 20:46:16 +0000 (GMT) Received: from wolff.to (wolff.to [66.93.197.194]) by svr1.postgresql.org (Postfix) with SMTP id CA87ED7CF0 for ; Fri, 26 Aug 2005 17:46:15 -0300 (ADT) Received: (qmail 11667 invoked by uid 500); 26 Aug 2005 20:45:54 -0000 Date: Fri, 26 Aug 2005 15:45:54 -0500 From: Bruno Wolff III To: Chris Hoover Cc: pgsql-performance@postgresql.org Subject: Re: How does the planner execute unions? Message-ID: <20050826204554.GB11078@wolff.to> Mail-Followup-To: Bruno Wolff III , Chris Hoover , pgsql-performance@postgresql.org References: <1d219a6f0508261314516fdb0@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1d219a6f0508261314516fdb0@mail.gmail.com> User-Agent: Mutt/1.5.6i X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.006 required=5 tests=[AWL=0.006] X-Spam-Level: X-Archive-Number: 200508/452 X-Sequence-Number: 14199 On Fri, Aug 26, 2005 at 16:14:18 -0400, Chris Hoover wrote: > Hopefully a quick question. > > In 7.3.4, how does the planner execute a query with union alls in it? > > Does it execute the unions serially, or does it launch a "thread" for > each union (or maybe something else entirely). Postgres doesn't have parallel execution of parts of queries. So it is going to do one part followed by the other part.