| From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
|---|---|
| To: | Vik Fearing <vik(at)postgresfriends(dot)org> |
| Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, David Fetter <david(at)fetter(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: | 2021-03-07 10:37:31 |
| Message-ID: | CAFj8pRA_7fj5HHq8133LtfJVnkXRQaSM97Pk5aCnwQb9XS6uGw@mail.gmail.com |
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ne 7. 3. 2021 v 11:28 odesílatel Vik Fearing <vik(at)postgresfriends(dot)org>
napsal:
> On 3/7/21 11:24 AM, Pavel Stehule wrote:
> >>
> >> And so you are now mandating an ORDER BY on every query and in every
> >> aggregate and/or window function. Users will not like that at all. I
> >> certainly shan't.
> >>
> >
> > The mandatory ORDER BY clause should be necessary for operations when the
> > result depends on the order. You need an order for calculation of median.
> > And you don't need to know an order for average. More if the result is
> one
> > number and is not possible to do a visual check of correctness (like
> > median).
>
> The syntax for median (percentile_cont(0.5)) already requires an order
> by clause. You are now requiring one on array_agg().
>
array_agg is discuttable, because PostgreSQL arrays are ordered set type.
But very common usage is using arrays instead and unordered sets (because
ANSI/SQL sets) are not supported. But anyway - for arrays I can do visual
check if it is ordered well or not.
--
> Vik Fearing
>
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