Re: Fwd: PG12 autovac issues

On Wed, Mar 18, 2020 at 1:40 PM Michael Lewis <mlewis(at)entrata(dot)com> wrote:
>
> Do you have default fillfactor set on this table? If not, I would wonder if reducing it to 50% or even 20% would allow many more HOT updates that would reduce bloat.

I don't believe we have a default fillfactor, but I'm still trying to
understand why autovacs would completely stop -- that seems like a
bug. Especially since there was no change between PG10 and PG12 and
this problem never existed there.

> Also, is there any period of lower activity on your system that you could schedule a vacuum freeze for daily or weekly? I believe having frozen pages would also mean all the autovacuums would be able to skip more pages and therefore be faster.
>
> >> autovacuum_vacuum_cost_delay = 20
>
> This was changed to 2ms in PG12. You should reduce that most likely.

Actually, we set that back from 2ms > 20ms to replicate what PG10 was
doing just in case it had an impact (spoiler: it did not).