Re: [PATCH] Negative Transition Aggregate Functions (WIP)

From: Greg Stark <stark(at)mit(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, David Rowley <dgrowleyml(at)gmail(dot)com>
Subject: Re: [PATCH] Negative Transition Aggregate Functions (WIP)
Date: 2013-12-14 23:48:04
Message-ID: CAM-w4HNdTRBViZWH=VJAdvt5NYgQH6Nc=GyMBBkZwQH19Au8Ag@mail.gmail.com
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On 14 Dec 2013 15:40, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> > The attached patch is not quite finished yet, I've not yet fully covered
> > SUM and AVG for all types.
>
> I think you *can't* cover them for the float types; roundoff error
> would mean you don't get the same answers as before.

I was going to say the same thing. But then I started to wonder.... What's
so special about the answers we used to give? They are also subject to
round off and the results are already quite questionable in those cases.

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