Re: Performance issue post upgrade on Version 13 - Incorrect Estimation Cost choosing Hash Aggregate-Nested Left Loop Join

Prajna Shetty <Prajna.Shetty@mindtree.com> writes:
> There is change in query plan in 12.4 version and Version 13 resulting in performance slowness post upgrade.

Standard upgrade methods don't transfer statistics from the old version,
so the first question to ask is have you ANALYZE'd the relevant tables
since upgrading?

If you have, then to offer useful help with this we'll need to see all
the details described in

https://wiki.postgresql.org/wiki/Slow_Query_Questions

In any case, this is unlikely to be a bug.  The pgsql-performance
list would be a more suitable place to discuss it.

            regards, tom lane