Re: Berserk Autovacuum (let's save next Mandrill)

The invoking autovacuum on table based on inserts, not only deletes
and updates, seems good idea to me. But in this case, I think that we
can not only freeze tuples but also update visibility map even when
setting all-visible. Roughly speaking  I think vacuum does the
following operations.

1. heap vacuum
2. HOT pruning
3. freezing tuples
4. updating visibility map (all-visible and all-frozen)
5. index vacuum/cleanup
6. truncation

With the proposed patch[1] we can control to do 5 or not. In addition
to that, another proposed patch[2] allows us to control 6.

[1] https://commitfest.postgresql.org/22/1817/
[2] https://commitfest.postgresql.org/22/1981/