Re: BUG #18261: Inconsistent results of SELECT affected by joined subqueries

On Fri, Jan 5, 2024 at 11:32 AM Andrei Lepikhov <a.lepikhov@postgrespro.ru> wrote:

The regression test shows where two fully equal join clauses, applied on
different join levels, differ by the only required_relids. It covers the
problem and can be helpful by itself. IMO, one line in this test is
redundant (see attachment).

Hmm, I don't think the insert statement in the test case is redundant.
It's needed to verify that the query in the test case gives the correct
result.  Without the insert statement, the wrong plan would give the
same result as the correct plan, i.e., an empty set in this case.

IMO, if we make some code changes and add a test case for that, we need
to ensure the test can give a different (and correct of course) result
than what came before.