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