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 1354C5350E for ; Mon, 9 May 2005 19:39:52 -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 02873-05 for ; Mon, 9 May 2005 22:39:34 +0000 (GMT) Received: from out1.smtp.messagingengine.com (out1.smtp.messagingengine.com [66.111.4.25]) by svr1.postgresql.org (Postfix) with ESMTP id 8D82653414 for ; Mon, 9 May 2005 19:38:58 -0300 (ADT) Received: from frontend3.messagingengine.com (frontend3.internal [10.202.2.152]) by frontend1.messagingengine.com (Postfix) with ESMTP id 27A60C8E619; Mon, 9 May 2005 18:38:50 -0400 (EDT) X-Sasl-enc: PuAeKWZaWJ3YFdmPrYz0VY8Mp5AymtlixCxBFraRs4ZS 1115678328 Received: from [192.168.0.4] (i-83-67-25-205.freedom2surf.net [83.67.25.205]) by www.fastmail.fm (Postfix) with ESMTP id A8C7C5F; Mon, 9 May 2005 18:38:47 -0400 (EDT) In-Reply-To: <427F6853.90308@cs.concordia.ca> References: <427F6853.90308@cs.concordia.ca> Mime-Version: 1.0 (Apple Message framework v622) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: <6f6c081fabe7002128433e3b99b09e50@diroussel.xsmail.com> Content-Transfer-Encoding: 7bit Cc: pgsql-perform From: David Roussel Subject: Re: "Hash index" vs. "b-tree index" (PostgreSQL 8.0) Date: Mon, 9 May 2005 23:38:47 +0100 To: Ying Lu X-Mailer: Apple Mail (2.622) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.05 tagged_above=0 required=5 tests=FORGED_RCVD_HELO X-Spam-Level: X-Archive-Number: 200505/125 X-Sequence-Number: 12289 > *Note: * Testing has shown PostgreSQL's hash indexes to perform no > better than B-tree indexes, and the index size and build time for hash > indexes is much worse. For these reasons, hash index use is presently > discouraged. > > May I know for simple "=" operation query, for "Hash index" vs. > "B-tree" index, which can provide better performance please? If you trust the documentation use a b-tree. If you don't trust the documentation do your own tests. please don't cross post.