Horton

Re: [patch] bit XOR aggregate functions

Pavel Stehule <pavel.stehule@gmail.com>

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From: Pavel Stehule <pavel.stehule@gmail.com>
To: Vik Fearing <vik@postgresfriends.org>
Cc: "David G. Johnston" <david.g.johnston@gmail.com>, David Fetter <david@fetter.org>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, "bashtanov@imap.cc" <bashtanov@imap.cc>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2021-03-07T10:37:31Z
Lists: pgsql-hackers 
ne 7. 3. 2021 v 11:28 odesílatel Vik Fearing <vik@postgresfriends.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
>

Commits

  1. Add bit_xor aggregate function