Upgraded 13.7 to 14.4 on RDS by restoring from a snapshot and upgrading that.
My configuration files and instance type are exactly the same. After upgrading, I ran vacuumdb -Z -j 8 and that did its thing.
The upgraded database is slower. I'm running EXPLAIN ANALYZE for various queries and it's getting to the same plan, but it's taking longer to execute.
I've always felt after major upgrades there's some element to "priming the database" where it seems to be much faster a few days in after broader usage. I realize it sounds absurd but I'll swear by this being my experience. So I'm willing to think to some degree that queries will execute faster the more people use the upgraded database.
Just wondering if there is anything I might specifically look at that would account for some of the slowness.