Fix VACUUM's reporting of dead-tuple counts to the stats collector.

Historically, VACUUM has just reported its new_rel_tuples estimate
(the same thing it puts into pg_class.reltuples) to the stats collector.
That number counts both live and dead-but-not-yet-reclaimable tuples.
This behavior may once have been right, but modern versions of the
pgstats code track live and dead tuple counts separately, so putting
the total into n_live_tuples and zero into n_dead_tuples is surely
pretty bogus.  Fix it to report live and dead tuple counts separately.

This doesn't really do much for situations where updating transactions
commit concurrently with a VACUUM scan (possibly causing double-counting or
omission of the tuples they add or delete); but it's clearly an improvement
over what we were doing before.

Hari Babu, reviewed by Amit Kapila

1 files changed, 3 insertions, 2 deletions

diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 96ecc3aff65..0b458e59bb2 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -333,7 +333,8 @@ typedef struct PgStat_MsgVacuum
 	Oid			m_tableoid;
 	bool		m_autovacuum;
 	TimestampTz m_vacuumtime;
-	PgStat_Counter m_tuples;
+	PgStat_Counter m_live_tuples;
+	PgStat_Counter m_dead_tuples;
 } PgStat_MsgVacuum;
 
 
@@ -775,7 +776,7 @@ extern void pgstat_reset_single_counter(Oid objectid, PgStat_Single_Reset_Type t
 
 extern void pgstat_report_autovac(Oid dboid);
 extern void pgstat_report_vacuum(Oid tableoid, bool shared,
-					 PgStat_Counter tuples);
+					 PgStat_Counter livetuples, PgStat_Counter deadtuples);
 extern void pgstat_report_analyze(Relation rel,
 					  PgStat_Counter livetuples, PgStat_Counter deadtuples);