Re: Clause accidentally pushed down ( Possible bug in Making Vars outer-join aware)

On Wed, Feb 22, 2023 at 6:24 PM Richard Guo <guofenglinux@gmail.com> wrote:

ISTM that for outer join identity 3, if we are given form
    (A leftjoin B on (Pab)) leftjoin C on (Pbc)
then references to C Vars in higher qual levels would be marked with the
B/C join.  If we've transformed it to form
    A leftjoin (B leftjoin C on (Pbc)) on (Pab)
then references to C Vars in higher qual levels should be adjusted to
include both B/C join and A/B join in their varnullingrels.

A quick hack that comes to my mind is that for a pushed down clause we
check all outer join relids it mentions and add the outer joins'
commute_below to the clause's required_relids, so that after we've
commuted the outer joins, the clause would still be placed in the right
place.