>>>This is not something I need right now, but I'm curious: is it possible
>>>to add aggregate functions as UDFs?
>>>
> Yes, I mean that KIND of function, but assume you'd want to return for
> example a concatenation of the values in a column:
>
> select Concat_UDF(ITEM)
> from STUFF
> group by CATEGORY

Adding this specific function was discussed yesterday on devel list.

Ivan