Dave, your result is not so strange, since the foreign key reference is not present in postgres.
My guess is that adding the simple rreference will give the same results as Oracle, while the multi-field version will make them behave identically.
Regarding the last comment: That is the entire point, right? You don't need the extra condition, but in many cases you inherit it from underlying views. And it slows things down for Oracle.
/Nis
