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 AB0915292C for ; Thu, 9 Jun 2005 13:55:34 -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 60646-08 for ; Thu, 9 Jun 2005 16:55:25 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id 91DBB5292E for ; Thu, 9 Jun 2005 13:55:23 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.1/8.13.1) with ESMTP id j59GtMFh014200; Thu, 9 Jun 2005 12:55:22 -0400 (EDT) To: Alex Stapleton Cc: pgsql-performance@postgresql.org Subject: Re: random_page_cost = 1? In-reply-to: References: Comments: In-reply-to Alex Stapleton message dated "Thu, 09 Jun 2005 17:37:25 +0100" Date: Thu, 09 Jun 2005 12:55:22 -0400 Message-ID: <14199.1118336122@sss.pgh.pa.us> From: Tom Lane 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: 200506/219 X-Sequence-Number: 12856 Alex Stapleton writes: > Is this advisable? Only if your database is small enough that you expect it to remain fully cached in RAM. In that case random_page_cost = 1 does in fact describe the performance you expect Postgres to see. People occasionally use values for random_page_cost that are much smaller than physical reality would suggest, but I think this is mainly a workaround for deficiencies elsewhere in the planner cost models. regards, tom lane