Re: sequential scan on select distinct

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: Pierre-Frédéric Caillaud <lists(at)boutiquenumerique(dot)com>, "Ole Langbehn" <ole(at)freiheit(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: sequential scan on select distinct
Date: 2004-10-06 19:38:26
Message-ID: 29194.1097091506@sss.pgh.pa.us
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Greg Stark <gsstark(at)mit(dot)edu> writes:
> why isn't a "skip index scan" plan available? Well, nobody's written the code
> yet.

I don't really think it would be a useful plan anyway. What *would* be
useful is to support HashAggregate as an implementation alternative for
DISTINCT --- currently I believe we only consider that for GROUP BY.
The DISTINCT planning code is fairly old and crufty and hasn't been
redesigned lately.

regards, tom lane

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