Re: NOT IN subquery optimization

"Li, Zheng" <zhelli@amazon.com> writes:
> Although adding "or var is NULL" to the anti join condition forces the planner to choose nested loop anti join, it is
alwaysfaster compared to the original plan. 

TBH, I am *really* skeptical of sweeping claims like that.  The existing
code will typically produce a hashed-subplan plan, which ought not be
that awful as long as the subquery result doesn't blow out memory.
It certainly is going to beat a naive nested loop.

            regards, tom lane