From: | Vik Fearing <vik(at)postgresfriends(dot)org> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
Cc: | Ronan Dunklau <ronan(dot)dunklau(at)aiven(dot)io>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Magnus Hagander <magnus(at)hagander(dot)net> |
Subject: | Re: Ordering behavior for aggregates |
Date: | 2022-12-13 18:02:16 |
Message-ID: | 52ca6930-fd6e-8eb5-2dae-e45fadd43222@postgresfriends.org |
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Lists: | pgsql-hackers |
On 12/13/22 18:22, Tom Lane wrote:
> "David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
>> I'm more keen on the idea of having the system understand when an ORDER BY
>> is missing - that seems like what users are more likely to actually do.
>
> That side of it could perhaps be useful, but not if it's an unintelligent
> analysis. If someone has a perfectly safe query written according to
> the old-school method:
>
> SELECT string_agg(...) FROM (SELECT ... ORDER BY ...) ss;
>
> they are not going to be too pleased with a nanny-ish warning (much
> less an error) saying that the aggregate's input ordering is
> underspecified.
That is a good point
> I also wonder whether we'd accept any ORDER BY whatsoever, or try
> to require one that produces a sufficiently-unique input ordering.
I would accept anything. agg(x order by y) is a common thing.
--
Vik Fearing
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