Magnus Jonsson <bigfoot(at)acc(dot)umu(dot)se> writes:
> I discoverd what seems to be a bug in postgresql 7.4.12 (also on
> 7.4.7).
AFAIR, 7.4 and earlier didn't really have a sane way of representing
NULL composite-type values, so this aggregate isn't going to work
before 8.0.
regards, tom lane