assertion failure with unique index + partitioning + join - Mailing list pgsql-hackers

While I was running some random testing on the TimescaleDB extension, I noticed that I can easily hit an assertion failure in plain Postgres REL_18_STABLE. I haven't analyzed it at all, but thought I should report this:

CREATE TABLE t (a bool UNIQUE) PARTITION BY LIST (a);
CREATE TABLE p PARTITION OF t DEFAULT;  
                                                                                    SELECT
FROM (
    SELECT *
    FROM t  
    LEFT JOIN t r USING (a)
)            
WHERE a
GROUP BY ();


TRAP: failed Assert("bms_is_member(i, root->outer_join_rels)"), File: "../pg/src/backend/optimizer/path/equivclass.c", Line: 3631, PID: 1813021