> I do think re-prioritization is worth considering, but IMHO we should leave
> it out of phase 1. I think it's pretty easy to reason about one round of
> prioritization being okay. The order is completely arbitrary today, so how
> could ordering by vacuum-related criteria make things any worse?
While it’s true that the current table order is arbitrary, that arbitrariness
naturally helps distribute vacuum work across tables of various sizes
at a given time
The proposal now is by design forcing all the top bloated table, that
will require more I/O to vacuum to be vacuumed at the same time,
by all workers. Users may observe this after they upgrade and wonder
why their I/O profile changed and perhaps slowed others non-vacuum
related processing down. They also don't have a knob to go back to
the previous behavior.
Of course, this behavior can and will happen now, but with this
prioritization, we are forcing it.
Is this a concern?
--
Sami Imseih
Amazon Web Services (AWS)
