Re: BUG #5606: DEFERRABLE and DEFERRABLE INITIALLY DEFERRED are the same

Frank Heikens <f(dot)heikens(at)anva(dot)nl> writes:
> The wikipage says
>> a deferrable constraint CAN be checked at the end of a
>> transaction. You still have to ask PostgreSQL to defer it.
> http://wiki.postgresql.org/wiki/What%27s_new_in_PostgreSQL_9.0#DEFERRABLE_UNIQUE_CONSTRAINTS

> I don't have to ask PostgreSQL to defer, it works in the second test
as well in the third test without any changes. I guess the example in
the wiki isn't correct, right?

No, not even a little bit :-(. I hadn't seen that text; it needs to be
corrected. Will hack on it in a moment.

> A single UPDATE touching all records will check the uniqueness after the complete update, not right after each update of a row as it does on non-deferrable constraints.

Right.
non-deferrable -> uniqueness is enforced after each row change
DEFERRABLE IMMEDIATE -> uniqueness is enforced at end of statement
DEFERRABLE DEFERRED -> uniqueness is enforced at end of transaction

> Maybe someone could make this clear in the manual and wiki?

AFAIK the manual is OK; do you see a place where it gets this wrong?

regards, tom lane