Janning Vygen <vygen(at)gmx(dot)de> writes:
> So here is my question: How can i define a functional index to be used
> with a primary key (using postgreSQL 7.4.3)?
You can't. The SQL spec says that primary keys are columns or lists of
columns.
I don't see any particular difference between a primary key and a unique
index, anyway, except that the primary key is the default target for
foreign-key references.
regards, tom lane