Re: *very* inefficient choice made by the planner (regarding

On Thu, 10 Jun 2004, Jean-Luc Lachance wrote:

> I agree, but it should be a simple rewrite. No?

It's NULLs inside the subselect that are the issue.

select 1 in (select a from foo)
select exists ( select 1 from foo where a=1)

If foo.a contains a row with NULL but no rows containing a 1, the above
give different results (unknown and exists) and IIRC, exists cannot
return unknown, so there's no simple rewrite of the subselect that gives
equivalent behavior.