On fre, 2009-11-13 at 10:01 -0500, Tom Lane wrote:
> Peter Eisentraut <peter_e@gmx.net> writes:
> > On fre, 2009-11-13 at 03:16 +0000, Andrew Gierth wrote:
> >> Caveat: as discussed earlier, this patch changes the behaviour of
> >> array_agg(DISTINCT x) when applied to NULL inputs. Formerly, the NULLs
> >> were unconditionally skipped; now, they are treated just like DISTINCT
> >> or GROUP BY normally do.
>
> > The right answer to that should be in the SQL standard.
>
> It's not. The standard defines the behavior of certain specific
> aggregates; it doesn't provide general rules that would apply to
> user-defined aggregates.
But array_agg is in the standard.