pgstat: stats collector references in comments.

Soon the stats collector will be no more, with statistics instead getting
stored in shared memory. There are a lot of references to the stats collector
in comments. This commit replaces most of these references with "cumulative
statistics system", with the remaining ones getting replaced as part of
subsequent commits.

This is done separately from the - quite large - shared memory statistics
patch to make review easier.

Author: Andres Freund <andres@anarazel.de>
Reviewed-By: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-By: Thomas Munro <thomas.munro@gmail.com>
Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de
Discussion: https://postgr.es/m/20220308205351.2xcn6k4x5yivcxyd@alap3.anarazel.de

1 files changed, 14 insertions, 14 deletions

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 6757df397cf..8cbed1d1bc3 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -693,9 +693,9 @@ allow_immediate_pgstat_restart(void)
 /*
  * Shut down a single backend's statistics reporting at process exit.
  *
- * Flush any remaining statistics counts out to the collector.
- * Without this, operations triggered during backend exit (such as
- * temp table deletions) won't be counted.
+ * Flush out any remaining statistics counts.  Without this, operations
+ * triggered during backend exit (such as temp table deletions) won't be
+ * counted.
  */
 static void
 pgstat_shutdown_hook(int code, Datum arg)
@@ -703,10 +703,10 @@ pgstat_shutdown_hook(int code, Datum arg)
 	Assert(!pgstat_is_shutdown);
 
 	/*
-	 * If we got as far as discovering our own database ID, we can report what
-	 * we did to the collector.  Otherwise, we'd be sending an invalid
-	 * database ID, so forget it.  (This means that accesses to pg_database
-	 * during failed backend starts might never get counted.)
+	 * If we got as far as discovering our own database ID, we can flush out
+	 * what we did so far.  Otherwise, we'd be reporting an invalid database
+	 * ID, so forget it.  (This means that accesses to pg_database during
+	 * failed backend starts might never get counted.)
 	 */
 	if (OidIsValid(MyDatabaseId))
 		pgstat_report_stat(true);
@@ -1065,7 +1065,7 @@ pgstat_collect_oids(Oid catalogid, AttrNumber anum_oid)
 }
 
 /*
- * Tell the statistics collector to reset counters for our database.
+ * Reset counters for our database.
  *
  * Permission checking for this function is managed through the normal
  * GRANT system.
@@ -1084,7 +1084,7 @@ pgstat_reset_counters(void)
 }
 
 /*
- * Tell the statistics collector to reset a single counter.
+ * Reset a single counter.
  *
  * Permission checking for this function is managed through the normal
  * GRANT system.
@@ -1106,7 +1106,7 @@ pgstat_reset_single_counter(Oid objoid, PgStat_Single_Reset_Type type)
 }
 
 /*
- * Tell the statistics collector to reset cluster-wide shared counters.
+ * Reset cluster-wide shared counters.
  *
  * Permission checking for this function is managed through the normal
  * GRANT system.
@@ -1198,8 +1198,8 @@ pgstat_clear_snapshot(void)
 /*
  * Support function for the SQL-callable pgstat* functions. Returns
  * the collected statistics for one database or NULL. NULL doesn't mean
- * that the database doesn't exist, it is just not yet known by the
- * collector, so the caller is better off to report ZERO instead.
+ * that the database doesn't exist, just that there are no statistics, so the
+ * caller is better off to report ZERO instead.
  */
 PgStat_StatDBEntry *
 pgstat_fetch_stat_dbentry(Oid dbid)
@@ -1233,8 +1233,8 @@ pgstat_fetch_global(void)
 /*
  * Support function for the SQL-callable pgstat* functions. Returns
  * the collected statistics for one table or NULL. NULL doesn't mean
- * that the table doesn't exist, it is just not yet known by the
- * collector, so the caller is better off to report ZERO instead.
+ * that the table doesn't exist, just that there are no statistics, so the
+ * caller is better off to report ZERO instead.
  */
 PgStat_StatTabEntry *
 pgstat_fetch_stat_tabentry(Oid relid)