FWIW, I've seen planning+query times triple with JIT on, with no partitioned tables involved. It just takes forever to JIT sometimes. (This was with Postgres 13 and 14, IIRC.)
Update: I checked some old IRC logs, and found a query that took 1476 ms without JIT and 8754 ms with JIT on. And that is execution time, not planning time!
Update: I checked some old IRC logs, and found a query that took 1476 ms without JIT and 8754 ms with JIT on. And that is execution time, not planning time!