To: Merlin Moncure <mmoncure@gmail.com>
cc: Claudio Freire <klaussfreire@gmail.com>,
	Robert Klemme <shortcutter@googlemail.com>,
	Stefan Keller <sfkeller@gmail.com>, Jeff Janes <jeff.janes@gmail.com>,
	Peter Geoghegan <peter@2ndquadrant.com>, pgsql-performance@postgresql.org
Subject: Re: Hash index use presently(?) discouraged since 2005: revive or
	bury it?
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Comments: In-reply-to Merlin Moncure <mmoncure@gmail.com>
	message dated "Tue, 20 Sep 2011 11:11:28 -0500"
Date: Tue, 20 Sep 2011 12:25:19 -0400
Message-ID: <9496.1316535919@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Merlin Moncure <mmoncure@gmail.com> writes:
> just selects.  update test is also very interesting -- the only test I
> did  for for updates is 'update foo set x=x+1' which was a win for
> btree (20-30% faster typically).  perhaps this isn't algorithm induced
> though -- lack of wal logging could actually hurt time to commit
> because it deserializes i/o.

In 9.1+, you could remove WAL from the comparison by doing the tests on
an unlogged table.

			regards, tom lane