Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id A5074B5DBD8 for ; Wed, 14 Sep 2011 06:04:11 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 96711-06 for ; Wed, 14 Sep 2011 09:04:05 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0-rc2 Received: from exprod7og114.obsmtp.com (exprod7og114.obsmtp.com [64.18.2.215]) by mail.postgresql.org (Postfix) with ESMTP id 549C3B5DBD6 for ; Wed, 14 Sep 2011 06:04:04 -0300 (ADT) Received: from mail-fx0-f45.google.com ([209.85.161.45]) (using TLSv1) by exprod7ob114.postini.com ([64.18.6.12]) with SMTP ID DSNKTnBuA6VHD3kqQ+ODCHR35MtKi98WgbDc@postini.com; Wed, 14 Sep 2011 02:04:05 PDT Received: by fxh13 with SMTP id 13so1815670fxh.18 for ; Wed, 14 Sep 2011 02:04:02 -0700 (PDT) Received: by 10.223.57.70 with SMTP id b6mr1680298fah.124.1315991041979; Wed, 14 Sep 2011 02:04:01 -0700 (PDT) Received: from [192.168.1.183] (dsl-hkibrasgw2-ff7ac300-240.dhcp.inet.fi. [88.195.122.240]) by mx.google.com with ESMTPS id g5sm2903271fad.19.2011.09.14.02.03.59 (version=TLSv1/SSLv3 cipher=OTHER); Wed, 14 Sep 2011 02:04:00 -0700 (PDT) Message-ID: <4E706DFE.40801@enterprisedb.com> Date: Wed, 14 Sep 2011 12:03:58 +0300 From: Heikki Linnakangas User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; fi-FI; rv:1.9.2.21) Gecko/20110831 Icedove/3.1.13 MIME-Version: 1.0 To: Tom Lane CC: Peter Geoghegan , Stefan Keller , pgsql-performance@postgresql.org Subject: Re: Hash index use presently(?) discouraged since 2005: revive or bury it? References: <16096.1315959870@sss.pgh.pa.us> In-Reply-To: <16096.1315959870@sss.pgh.pa.us> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.9 tagged_above=-10 required=5 tests=BAYES_00=-1.9 X-Spam-Level: X-Archive-Number: 201109/209 X-Sequence-Number: 44985 On 14.09.2011 03:24, Tom Lane wrote: > The big picture though is that we're not going to remove hash indexes, > even if they're nearly useless in themselves, because hash index > opclasses provide the foundation for the system's knowledge of how to > do the datatype-specific hashing needed for hash joins and hash > aggregation. And those things *are* big wins, even if hash indexes > themselves never become so. We could drop the hash indexam code but keep the opclasses etc. I'm not sure that would gain us, though. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com