Re: Add parallel columns for seq scan and index scan on pg_stat_all_tables and _indexes

Hi,

On Wed, Sep 04, 2024 at 02:51:51PM +0200, Guillaume Lelarge wrote:
> Hi,
> 
> Le mer. 4 sept. 2024 à 10:47, Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
> a écrit :
> 
> > What about to get rid of the pgstat_count_parallel_heap_scan and add an
> > extra
> > bolean parameter to pgstat_count_heap_scan to indicate if
> > counts.parallelnumscans
> > should be incremented too?
> >
> > Something like:
> >
> > pgstat_count_heap_scan(scan->rs_base.rs_rd, scan->rs_base.rs_parallel !=
> > NULL)
> >
> > 3 ===
> >
> > Same comment for pgstat_count_index_scan (add an extra bolean parameter)
> > and
> > get rid of pgstat_count_parallel_index_scan()).
> >
> > I think that 2 === and 3 === would help to avoid missing increments should
> > we
> > add those call to other places in the future.
> >
> >
> Oh OK, understood.  Done for both.

Thanks for v2!

1 ===

-#define pgstat_count_heap_scan(rel)
+#define pgstat_count_heap_scan(rel, parallel)
        do {
-               if (pgstat_should_count_relation(rel))
-                       (rel)->pgstat_info->counts.numscans++;
+            if (pgstat_should_count_relation(rel)) {
+                       if (!parallel)
+                               (rel)->pgstat_info->counts.numscans++;
+                       else
+                               (rel)->pgstat_info->counts.parallelnumscans++;
+               }

I think counts.numscans has to be incremented in all the cases (so even if
"parallel" is true).

Same comment for pgstat_count_index_scan().

> 4 ===
> >
> > +       if (lstats->counts.numscans || lstats->counts.parallelnumscans)
> >
> > Is it possible to have (lstats->counts.parallelnumscans) whithout having
> > (lstats->counts.numscans) ?
> >
> >
> Nope, parallel scans are included in seq/index scans, as far as I can tell.
> I could remove the parallelnumscans testing but it would be less obvious to
> read.

2 ===

What about adding a comment instead of this extra check?

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
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