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To: "Peter Childs" <peterachilds@gmail.com>
cc: "Postgresql Performance" <pgsql-performance@postgresql.org>
Subject: Re: GROUP BY vs DISTINCT 
In-reply-to: <a2de01dd0612200316g92cc189jf3369ccedf1b8c12@mail.gmail.com> 
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	<20061220105739.GB31739@uio.no>
	<a2de01dd0612200316g92cc189jf3369ccedf1b8c12@mail.gmail.com>
Comments: In-reply-to "Peter Childs" <peterachilds@gmail.com>
	message dated "Wed, 20 Dec 2006 11:16:40 +0000"
Date: Wed, 20 Dec 2006 10:36:38 -0500
Message-ID: <22279.1166628998@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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"Peter Childs" <peterachilds@gmail.com> writes:
> Is it actually in the sql spec to sort in a distinct

No.  PG's code that supports GROUP BY is newer and smarter than the code
that supports DISTINCT, is all.  One of the things on the to-do list is
to revise DISTINCT so it can also consider hash-based implementations.
The hard part of that is not to break DISTINCT ON ...

			regards, tom lane