We are on Postgres 15.5 (Aurora) and capturing query plans via auto_explain. We are seeing a large number of query plans for 2 queries that have 12 tables. Every fast (or "fast enough") plan has a left deep tree and every slow plan has a bushy tree. Is there a way to determine if a plan was generated by GECO?
We have from_collapse_limit, join_collapse_limit and geqo_threshold all set to 12. (There is a COUNT(*) above derived table - could that be somehow affecting this?)
I've manually explained plans and haven't seen the problem, but then it turns up the next day (with the same parameter values) with multiple execution plans.
I'm not aware of ability to see if grow was involved, but with Aurora, should be able can provision a thin (CoW) clone with PITR to a specific point when you suspect the plan in question was used ("slow") -- and study the planner behavior in detail, experimenting and adjusting planner parameters.
