Re: DELETE using an outer join

Thomas Kellerer <spam_eater(at)gmx(dot)net> writes:
> Lately I had some queries of the form:

> select t.*
> from some_table t
> where t.id not in (select some_id from some_other_table);

> I could improve the performance of them drastically by changing the NOT NULL into an outer join:

> select t.*
> from some_table t
> left join some_other_table ot on ot.id = t.id
> where ot.id is null;

If you're using a reasonably recent version of PG, replacing the NOT IN
by a NOT EXISTS test should also help.

> Now I was wondering if a DELETE statement could be rewritten with the same "strategy":

Not at the moment. There have been discussions of allowing the same
table name to be respecified in USING, but there are complications.

regards, tom lane