Re: pgsql/src/test/regress/expected (union.out)

Alfred Perlstein <bright@wintelcom.net> writes:
>> Reimplementation of UNION/INTERSECT/EXCEPT.

> Does this mean that in the next release EXCEPT will be a lot faster?
> Will I probably be able to drop my "NOT EXISTS" hacks that I've
> been using?

UNION/INTERSECT/EXCEPT are now all basically a sort phase and a
unique-filter phase, with minor variations on what the unique filter
thinks it should output.  So the cost should be O((M+N) log (M+N)) for
M+N input tuples, as opposed to O(M*N) for the old INTERSECT and
EXCEPT code.

I didn't do anything to change EXISTS ...

            regards, tom lane