>From the create_aggregate man page...

"The arguments to state-transition-function-1 must be
(stype1,basetype), and its return value must be stype1."

create aggregate MIN (sfunc1 = int2smaller,
                      basetype = int2,
                      stype1 = int2);

will fail becase int2smaller and int2larger are in pg_proc
as returning an int4.  Can't happen since both args have to
be int2.

From: Darren King <aixssd!ceodev!darrenk@abs.net>