Received: from maia.hub.org (maia-3.hub.org [200.46.204.243]) by mail.postgresql.org (Postfix) with ESMTP id A3E351336FA7 for ; Wed, 27 Oct 2010 18:49:52 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.243]) (amavisd-maia, port 10024) with ESMTP id 56044-07 for ; Wed, 27 Oct 2010 21:49:45 +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 43383133655C for ; Wed, 27 Oct 2010 18:49:45 -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 o9RLng8a029057; Wed, 27 Oct 2010 17:49:42 -0400 (EDT) To: Kenneth Marshall cc: Pierre C , Robert Haas , Mladen Gogala , pgsql-performance@postgresql.org Subject: Re: Select count(*), the sequel In-reply-to: <20101027204115.GB27429@aart.is.rice.edu> References: <4CB9D89E.7050701@vmsinfo.com> <20101016184443.GA4993@aart.is.rice.edu> <2091.1288133491@sss.pgh.pa.us> <20101027204115.GB27429@aart.is.rice.edu> Comments: In-reply-to Kenneth Marshall message dated "Wed, 27 Oct 2010 15:41:15 -0500" Date: Wed, 27 Oct 2010 17:49:42 -0400 Message-ID: <29056.1288216182@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.91 tagged_above=-10 required=5 tests=BAYES_00=-1.9, T_RP_MATCHES_RCVD=-0.01 X-Spam-Level: X-Archive-Number: 201010/517 X-Sequence-Number: 40935 Kenneth Marshall writes: > Just keeping the hope alive for faster compression. Is there any evidence that that's something we should worry about? I can't recall ever having seen a code profile that shows the pg_lzcompress.c code high enough to look like a bottleneck compared to other query costs. Now, the benefits of 2X or 3X space savings would be pretty obvious, but I've seen no evidence that we could easily achieve that either. regards, tom lane