Unique functional index and FK constraints

Tom,

When you restructured the unique index location and validation for
foreign key constraints around 9/22 you added the restriction that the
supporting unique index may not be functional.  I believe that this
restriction is not necessary.  Suppose I had a unique index on
LOWER(login).  That would imply that login is unique as well.  Any
function which returns different results given the same input is no good
for a functional index anyway.

http://archives.postgresql.org/pgsql-committers/2002-09/msg00293.php

Kris Jurka