Re: unstable query plan on pg 16,17,18

Thanks. But I meant your 'good' plan built by the PG14. I think a new feature invented later has added some problems.

Current conjecture is the following. As I see, the main problem is with Right Hash Join:
-> Hash Right Join (cost=210369.25..210370.30 rows=8 width=99)
Its inner side (Hash table) is rebuilt multiple times (around 1k) due to an external parameter (gauf_1.id) in the subtree. It looks like a disaster, and before I thought we don't build hash tables over parameterised query trees at all.

So, let me discover a little more, but your PG14 explain could add more details here.