> I doubt there is any substantial resistance to including such a function > but it would have to be written in C.
Would anything have to be written at all, save the CREATE AGGREGATE suggested in the original message, using the existing array_cat as the state transition function?
I suppose one might add an optimization to the existing array_cat to detect the aggregate case, and realize it could clobber its left argument. (But I'm not sure how much that would save, with arrays.)
Outside my particular area of involvement really; it may be sufficient.