BUG #2251: NOT IN clause is not working correctly

The following bug has been logged online:

Bug reference: 2251
Logged by: Sergei Dubov
Email address: sdubov(at)gmail(dot)com
PostgreSQL version: 8.1.2
Operating system: Windows XP
Description: NOT IN clause is not working correctly
Details:

I have two tables, let's say A and B.

B is a child of a in one to many relationship. A contains records that are
not referenced by B.

I am running a query:

select * from A t1 where t1.id not in (select t2.A_id from B t2);

It returns 0 rows.

Now I run
(select t1.id from A t1) except (select t2.A_id from B t2);

And now Postgres correctly returns records from A that are not referenced by
B.

Thanks a lot for your consideration of this bug.

Serge.