=?UTF-8?Q?F=C3=A1bio_Moreira?= <fabio@dias.moreira.nom.br> writes:
> From what I could find, PostgreSQL’s tests check for output correctness but
> not if the query planner is actually applying specific optimizations to the
> input query; is that correct?
There are quite a few regression tests that look at EXPLAIN output to
verify that particular optimizations happen (or not) as intended.
There's no user-facing mechanism other than that. For development
purposes, you could consider inserting pprint() calls on Paths at
critical points, or just invoking pprint manually from gdb --- the latter
is what I usually do.
regards, tom lane