| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | David Fetter <david(at)fetter(dot)org> |
| Cc: | Vik Fearing <vik(at)postgresfriends(dot)org>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, "bashtanov(at)imap(dot)cc" <bashtanov(at)imap(dot)cc>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [patch] bit XOR aggregate functions |
| Date: | 2021-03-06 20:06:26 |
| Message-ID: | CAKFQuwbPO55vGvYnN1s=rcaqp0ofHVhMqEoJ_w_W1625s5nbqA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Saturday, March 6, 2021, David Fetter <david(at)fetter(dot)org> wrote:
>
> > > SELECT BIT_XOR(b ORDER BY a, c)... /* works */
> > > SELECT BIT_XOR(b) OVER (ORDER BY a, c)... /* works */
> > > SELECT BIT_XOR(b) FROM... /* errors out */
> >
> >
> > Why would such an error be necessary, or even desirable?
>
> Because there is no way to ensure that the results remain consistent
> from one execution to the next without such a guarantee.
>
Numerous existing aggregate functions have this behavior. Making those
error isn’t an option. So is making this a special case something we want
to do (and also maybe make doing so the rule going forward)?
David J.
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