Re: non-deterministic error related to MIN/MAX optimization

2008/8/26 Tom Lane <tgl@sss.pgh.pa.us>:
> Jeff Davis <pgsql@j-davis.com> writes:
>> => -- make "foo" into a subquery and add a no-op
>> => -- to prevent it from pulling up the subquery
>> => select max(a), generate_series(1,2) as g from (select a as a from foo
>> offset 0) dummy;
>> ERROR:  set-valued function called in context that cannot accept a set
>
>> So, although Dan's transformations were semantically correct, they ended
>> up causing this regression failure.
>
>> It doesn't have anything to do with the ORDER BY, so that part of my
>> example was unnecessary.
>
> Hmm ... after a bit of poking at it, the reason it's failing is that Agg
> plan nodes don't support SRFs in their targetlists.  (Group nodes don't
> either.)  Kind of interesting that no one ever complained about that
> before ... although given that plpgsql SRFs don't work in targetlists
> anyway, maybe it's been masked for common uses.
>
> I'm not entirely sure if we should add SRF support to Agg/Group or just
> write it off as being a deprecated feature anyhow.  Given the
> definitional issues involved with multiple SRFs in the same targetlist,
> putting more effort into the feature doesn't seem like a great
> investment of time.

I dislike this feature - sometime we can do nice hack with it, but
it's very dificult readable.

regards
Pavel Stehule

>
>                        regards, tom lane
>
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