Re: Ordering behavior for aggregates

On 12/13/22 18:22, Tom Lane wrote:
> "David G. Johnston" <david.g.johnston@gmail.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