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

On Tue, 31 Mar 2020 at 12:58, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Mon, Mar 30, 2020 at 12:31 PM Masahiko Sawada
> <masahiko(dot)sawada(at)2ndquadrant(dot)com> wrote:
> >
> > The patch for vacuum conflicts with recent changes in vacuum. So I've
> > attached rebased one.
> >
>
> + /*
> + * Next, accumulate buffer usage. (This must wait for the workers to
> + * finish, or we might get incomplete data.)
> + */
> + for (i = 0; i < nworkers; i++)
> + InstrAccumParallelQuery(&lps->buffer_usage[i]);
> +
>
> This should be done for launched workers aka
> lps->pcxt->nworkers_launched. I think a similar problem exists in
> create index related patch.

You're right. Fixed in the new patches.

On Mon, 30 Mar 2020 at 17:00, Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote:
>
> Just minor nitpicking:
>
> + int i;
>
> Assert(!IsParallelWorker());
> Assert(ParallelVacuumIsActive(lps));
> @@ -2166,6 +2172,13 @@ lazy_parallel_vacuum_indexes(Relation *Irel, IndexBulkDeleteResult **stats,
> /* Wait for all vacuum workers to finish */
> WaitForParallelWorkersToFinish(lps->pcxt);
>
> + /*
> + * Next, accumulate buffer usage. (This must wait for the workers to
> + * finish, or we might get incomplete data.)
> + */
> + for (i = 0; i < nworkers; i++)
> + InstrAccumParallelQuery(&lps->buffer_usage[i]);
>
> We now allow declaring a variable in those loops, so it may be better to avoid
> declaring i outside the for scope?

We can do that but I was not sure if it's good since other codes
around there don't use that. So I'd like to leave it for committers.
It's a trivial change.

Regards,

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