Using SETOF functions in SQL

Hi!

  Is it possible to use a function that returns SETOF and doesn't take constant parameters?

I have a function 'connections(id1 bigint, id2 bigint) returns setof text' that I use to list all paths from id1 to id2. However, I haven't figured out a way to call the function with non-constant functions. For example, if I try to write:

SELECT t1.node, t2.node, path FROM t1,t2, connections(t1.id, t2.id) as path

I get the notorious:  ERROR:  subquery in FROM may not refer to other relations of same query level


Is there a way to reformulate the query in SQL, or I am stuck with PgSQL now?

Thanks!
Pavel Velikhov
ISP RAS