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Re: variance aggregates per SQL:2003

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Neil Conway <neilc(at)samurai(dot)com>
Cc: David Fetter <david(at)fetter(dot)org>, pgsql-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: variance aggregates per SQL:2003
Date: 2006-03-08 03:25:33
Message-ID: 7783.1141788333@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-patches
Neil Conway <neilc(at)samurai(dot)com> writes:
> Well, I realize that stddev(DISTINCT x) != stddev(x) and that most
> people are going to be interested in stddev(x), but I don't think it's
> inconceivable for someone to be interested in stddev(DISTINCT x).
> Explicitly checking for and rejecting it doesn't serve any useful
> purpose that I can see, beyond compliance with the letter of the
> standard -- if the user asks for stddev(DISTINCT x), are we really
> providing useful behavior if we refuse to calculate it?

Agreed, refusing this is not something we should waste code on.

			regards, tom lane

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