Received: from maia.hub.org (unknown [200.46.204.183]) by mail.postgresql.org (Postfix) with ESMTP id 74A9279786B for ; Wed, 17 Mar 2010 11:31:01 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 25151-02 for ; Wed, 17 Mar 2010 14:30:50 +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 C3AD7643591 for ; Wed, 17 Mar 2010 11:30:50 -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 o2HEUhrj027970; Wed, 17 Mar 2010 10:30:43 -0400 (EDT) To: Greg Smith cc: Rob Wultsch , pgsql-performance@postgresql.org Subject: Re: Building multiple indexes concurrently In-reply-to: <4BA0AAD1.5040508@2ndquadrant.com> References: <2c5ef4e31003161804l5e32ceb9v6b7019118f30004d@mail.gmail.com> <4BA0AAD1.5040508@2ndquadrant.com> Comments: In-reply-to Greg Smith message dated "Wed, 17 Mar 2010 06:11:29 -0400" Date: Wed, 17 Mar 2010 10:30:43 -0400 Message-ID: <27969.1268836243@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-2.599 tagged_above=-10 required=5 tests=BAYES_00=-2.599 X-Spam-Level: X-Archive-Number: 201003/197 X-Sequence-Number: 38022 Greg Smith writes: > Rob Wultsch wrote: >> At a minimum I assume that if both of the commands were started at >> about the same time they would each scan the table in the same >> direction and whichever creation was slower would benefit from most of >> the table data it needed being prepopulated in shared buffers. Is this >> the case? > This might be optimistic; No, it's not optimistic in the least, at least not since we implemented synchronized seqscans (in 8.3 or thereabouts). regards, tom lane