DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.it;
	h=X-YMail-OSG:Received:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding;
	b=mHqfVoNeO7MSeFvUnkWHMh21uuKVsMyGnNnl6tzB53j8uH9XpQ2GDOnYDDSZ86V8waYyz4je2PTjY6wKb8/IKNqVXHYymeMSMIdpLKKQVhCGQkcKnIvsAAqb8km+oVDdyPw5w6MAGsoAujVRWYCTQScrXQTSJXLx3B0/hgH8Phw=;
References: 
 <CAFcOn293Rzi7cZYWBT8tjxCtNX5pYdbknANXgf9mWfBizK8Frg@mail.gmail.com>
	<CAEYLb_Udue8_XSE9K0KMqKBE_62yurv1bY4Wc+qJoGykZ_rXtA@mail.gmail.com>
	<16096.1315959870@sss.pgh.pa.us>
Message-ID: <1315993407.43414.YahooMailNeo@web29009.mail.ird.yahoo.com>
Date: Wed, 14 Sep 2011 10:43:27 +0100 (BST)
From: Leonardo Francalanci <m_lists@yahoo.it>
Reply-To: Leonardo Francalanci <m_lists@yahoo.it>
Subject: Re: Hash index use presently(?) discouraged since 2005: revive or
	bury it?
To: Tom Lane <tgl@sss.pgh.pa.us>, Peter Geoghegan <peter@2ndquadrant.com>
Cc: Stefan Keller <sfkeller@gmail.com>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
In-Reply-To: <16096.1315959870@sss.pgh.pa.us>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

>>  Hash indexes have been improved since 2005 - their performance was=0A=
=0A>>  improved quite a bit in 9.0. Here's a more recent analysis:=0A> =0A>=
>  http://www.depesz.com/index.php/2010/06/28/should-you-use-hash-index/=0A=
> =0A> The big picture though is that we're not going to remove hash indexe=
s,=0A> even if they're nearly useless in themselves=0A=0AWell, if they prov=
ide 3x the performance of btree indexes on index creation,=0AI wouldn't cal=
l them "useless" just because they're not logged or they can't=0Abe unique.=
 In fact, I think the docs should specify that in index creation=0Athey're =
actually better than btree (if, in fact, they are and the "depesz" test=0Ai=
s not a corner case).