Received: from maia.hub.org (unknown [200.46.204.183]) by mail.postgresql.org (Postfix) with ESMTP id BDA7D6332E6 for ; Sun, 21 Mar 2010 12:39:26 -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 46898-04 for ; Sun, 21 Mar 2010 15:39:16 +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 1B09F6330A6 for ; Sun, 21 Mar 2010 12:39:15 -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 o2LFd4g8022118; Sun, 21 Mar 2010 11:39:04 -0400 (EDT) To: Craig Ringer cc: David Newall , pgsql-performance@postgresql.org, robertmhaas@gmail.com, dcrooke@gmail.com Subject: Re: pg_dump far too slow In-reply-to: <4BA62596.8050604@postnewspapers.com.au> References: <4B9C97E1.40509@davidnewall.com> <24696.1268598111@sss.pgh.pa.us> <4BA61C74.70506@davidnewall.com> <4BA62596.8050604@postnewspapers.com.au> Comments: In-reply-to Craig Ringer message dated "Sun, 21 Mar 2010 21:56:38 +0800" Date: Sun, 21 Mar 2010 11:39:04 -0400 Message-ID: <22117.1269185944@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: 201003/258 X-Sequence-Number: 38083 Craig Ringer writes: > On 21/03/2010 9:17 PM, David Newall wrote: >> and wonder if I should read up on gzip to find why it would work so >> slowly on a pure text stream, albeit a representation of PDF which >> intrinsically is fairly compressed. > In fact, PDF uses deflate compression, the same algorithm used for gzip. > Gzip-compressing PDF is almost completely pointless - Yeah. I would bet that the reason for the slow throughput is that gzip is fruitlessly searching for compressible sequences. It won't find many. regards, tom lane