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. In particular, all the standard aggregates
are strict and so they just ignore nulls anyhow. The proposed change
would only affect the behavior of aggregates with non-strict transition
functions.
regards, tom lane