1: Is it necessary to perform a VACUUM and REINDEXING operation after restoring the dump from Postgres 9.6 to Postgres 13? The dump size could be 1/2 TB to 1 TB.
Perform VACUUM after there have been many updates and deletes. There have been zero updates and deleted after pg_restore; therefore, no need to vacuum.
I disagree. You're right about the "zero updates and deletes", so no need to vacuum for bloat. But you need vacuum to get the visibility map of each relation, so that the planner can use index-only scans.
