Re: pg_stat_statements issue with parallel maintenance (Was Re: WAL usage calculation patch)

On Sat, Mar 28, 2020 at 8:47 PM Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote:
>
> On Sat, Mar 28, 2020 at 02:38:27PM +0100, Julien Rouhaud wrote:
> > On Sat, Mar 28, 2020 at 04:14:04PM +0530, Amit Kapila wrote:
> > >
> > > I see some basic problems with the patch. The way it tries to compute
> > > WAL usage for parallel stuff doesn't seem right to me. Can you share
> > > or point me to any test done where we have computed WAL for parallel
> > > operations like Parallel Vacuum or Parallel Create Index?
> >
> > Ah, that's indeed a good point and AFAICT WAL records from parallel utility
> > workers won't be accounted for. That being said, I think that an argument
> > could be made that proper infrastructure should have been added in the original
> > parallel utility patches, as pg_stat_statement is already broken wrt. buffer
> > usage in parallel utility, unless I'm missing something.
>
> Just to be sure I did a quick test with pg_stat_statements behavior using
> parallel/non-parallel CREATE INDEX and VACUUM, and unsurprisingly buffer usage
> doesn't reflect parallel workers' activity.
>

Sawada-San would like to investigate this? If not, I will look into
this next week.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com