Samuel Hwang <samuel@xxxxxxxxxxxx> writes: > Thanks. But I am not looking for how to avoid the problem at this > moment, > I am more interested in why PostgreSQL is designed to work this way. Performance --- it's significantly more expensive to do a deferred uniqueness check, since you have to visit the index a second time. Also backwards compatibility with older versions of PG, which did not have support for deferred uniqueness checks at all. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
