At Tue, 19 Mar 2019 17:51:32 +0900, Masahiko Sawada <sawada.mshk@gmail.com> wrote in
<CAD21AoCUZQmyXrwDw57ejoR-j1QrGqm_vrQKOkif_aJK4Gih6Q@mail.gmail.com>
> On Tue, Mar 19, 2019 at 10:39 AM Haribabu Kommi
> <kommi.haribabu@gmail.com> wrote:
> > The performance results are good. Do we want to add the recommended
> > size in the document for the parallel option? the parallel option for smaller
> > tables can lead to performance overhead.
> >
>
> Hmm, I don't think we can add the specific recommended size because
> the performance gain by parallel lazy vacuum depends on various things
> such as CPU cores, the number of indexes, shared buffer size, index
> types, HDD or SSD. I suppose that users who want to use this option
> have some sort of performance problem such as that vacuum takes a very
> long time. They would use it for relatively larger tables.
Agree that we have no recommended setting, but I strongly think that documentation on the downside or possible side
effectof this feature is required for those who are to use the feature.
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center