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

On Sun, 29 Mar 2020 at 14:23, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> 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.

Sure, I'll investigate this issue today.

Regards,

--
Masahiko Sawada http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services