Re: Vacuum statistics

On Thu, May 30, 2024 at 11:57 PM Alena Rybakina
<lena(dot)ribackina(at)yandex(dot)ru> wrote:
>
> On 30.05.2024 10:33, Alena Rybakina wrote:
> >
> > I suggest gathering information about vacuum resource consumption for
> > processing indexes and tables and storing it in the table and index
> > relationships (for example, PgStat_StatTabEntry structure like it has
> > realized for usual statistics). It will allow us to determine how well
> > the vacuum is configured and evaluate the effect of overhead on the
> > system at the strategic level, the vacuum has gathered this
> > information already, but this valuable information doesn't store it.
> >
> My colleagues and I have prepared a patch that can help to solve this
> problem.
>
> We are open to feedback.

I was reading through the patch here are some initial comments.

--
+typedef struct LVExtStatCounters
+{
+ TimestampTz time;
+ PGRUsage ru;
+ WalUsage walusage;
+ BufferUsage bufusage;
+ int64 VacuumPageMiss;
+ int64 VacuumPageHit;
+ int64 VacuumPageDirty;
+ double VacuumDelayTime;
+ PgStat_Counter blocks_fetched;
+ PgStat_Counter blocks_hit;
+} LVExtStatCounters;

I noticed that you are storing both pgBufferUsage and
VacuumPage(Hit/Miss/Dirty) stats. Aren't these essentially the same?
It seems they both exist in the system because some code, like
heap_vacuum_rel(), uses pgBufferUsage, while do_analyze_rel() still
relies on the old counters. And there is already a patch to remove
those old counters.

--
+static Datum
+pg_stats_vacuum(FunctionCallInfo fcinfo, ExtVacReportType type, int ncolumns)
+{

I don't think you need this last parameter (ncolumns) we can anyway
fetch that from tupledesc, so adding an additional parameter
just for checking doesn't look good to me.

--
+ /* Tricky turn here: enforce pgstat to think that our database us dbid */
+
+ MyDatabaseId = dbid;

typo
/think that our database us dbid/think that our database has dbid

Also, remove the blank line between the comment and the next code
block that is related to that comment.

--
VacuumPageDirty = 0;
+ VacuumDelayTime = 0.;

There is an extra "." after 0

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com