Re: v16 regression - wrong query results with LEFT JOINs + join removal

Robert Haas <robertmhaas@gmail.com> writes:
> While merging commits from c9f7f926484d69e2806e35343af7e472fadfede7
> through 3db72ebcbe20debc6552500ee9ccb4b2007f12f8 into a fork, my
> colleague Rushabh Lathia and I noticed that the merge caused certain
> queries to return wrong answers.

I believe this is a variant of the existing open issue about
the outer-join-Vars stuff:

https://www.postgresql.org/message-id/flat/0b819232-4b50-f245-1c7d-c8c61bf41827%40postgrespro.ru

although perhaps different in detail --- EXPLAIN shows that the
join condition has gone missing completely, rather than just
being put at the wrong join level.  Possibly related to the
join removal that happened to pg_db_role_setting?

I've been incredibly distracted by $real-life over the past few
weeks, but am hoping to get the outer-join-Vars issues resolved
in the next day or two.

            regards, tom lane