On Tue, 27 Jan 2026 at 08:27, jian he <[email protected]> wrote: > > While reviewing ON CONFLICT DO SELECT, I found an elog(ERROR) behavior, which > may a bug.
Hmm, AFAICS this has never worked. Here's a simpler example (taking ON CONFLICT out of the equation, since it has nothing to do with that): DROP TABLE IF EXISTS foo, bar; CREATE TABLE foo (a int); CREATE TABLE bar (a int); CREATE RULE foo_ins AS ON INSERT TO foo DO INSTEAD INSERT INTO bar VALUES (new.a) RETURNING *; INSERT INTO foo VALUES (1) RETURNING tableoid, a; This gives the same error, because tableoid (or any other system attribute) is not in the rule's RETURNING list, and so cannot be returned by the outer query. Also, there's no way for the user to add support for returning system attributes, because the rule's RETURNING list must have the same number (and types) of (user) columns as the relation the rule is on. Arguably then, this is correct behaviour, within the limitations of the rules system, although the error message is not very friendly. Given the near-deprecated nature of rules, it's also arguable that it's not worth trying to fix this, except perhaps to improve the error message. Regards, Dean
