Thomas Kellerer <spam_eater@gmx.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
