Martijn van Oosterhout wrote:
> Sure, UNIQUE constraints are not deferrable. With normal constraints
> you can defer the check until the end of transaction and be in an
> inconsistant state for while. However, PostgreSQL doesn't support
> this for uniqueness checks.
Note that even a nondeferred unique constraint would let the command
proceed because a nondeferred constraint is checked after the
statement, not at seemingly random points during it.
--
Peter Eisentraut
http://developer.postgresql.org/~petere/