In our patch, we only proceed with the ANTI JOIN transformation if
subplan_is_hashable(subplan) is
false, it requires the subquery to be planned at this point.
To avoid planning the subquery again later on, I want to keep a pointer of
the subplan in SubLink so that we can directly reuse the subplan when
needed. However, this change breaks initdb for some reason and I'm trying to
figure it out.
I'll send the rebased patch in the following email since it's been a while.
--
Sent from: http://www.postgresql-archive.org/PostgreSQL-hackers-f1928748.html