Simon Riggs <simon@2ndquadrant.com> writes:
> I vote to make this an ERROR in 8.1 - I see little benefit in allowing
> this situation to continue.
Other than spec compliance, you mean? SQL99 says
... The declared type of each referencing column shall be
comparable to the declared type of the corresponding referenced
column.
It doesn't say that it has to be indexable, and most definitely not that
there has to be an index.
regards, tom lane