Re: cost based vacuum (parallel)

Greetings,

* Jeff Janes (jeff(dot)janes(at)gmail(dot)com) wrote:
> On Mon, Nov 4, 2019 at 1:54 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > For parallel vacuum [1], we were discussing what is the best way to
> > divide the cost among parallel workers but we didn't get many inputs
> > apart from people who are very actively involved in patch development.
> > I feel that we need some more inputs before we finalize anything, so
> > starting a new thread.
>
> Maybe a I just don't have experience in the type of system that parallel
> vacuum is needed for, but if there is any meaningful IO throttling which is
> active, then what is the point of doing the vacuum in parallel in the first
> place?

With parallelization across indexes, you could have a situation where
the individual indexes are on different tablespaces with independent
i/o, therefore the parallelization ends up giving you an increase in i/o
throughput, not just additional CPU time.

Thanks,

Stephen