Add stats_reset to pg_stat_user_functions

It is possible to call pg_stat_reset_single_function_counters() for a
single function, but the reset time was missing the system view showing
its statistics.  Like all the fields of pg_stat_user_functions, the GUC
track_functions needs to be enabled to show the statistics about
function executions.

Bump catalog version.
Bump PGSTAT_FILE_FORMAT_ID, as a result of the new field added to
PgStat_StatFuncEntry.

Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: https://postgr.es/m/aONjnsaJSx-nEdfU@paquier.xyz

4 files changed, 27 insertions, 1 deletions

diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 884b6a23817..c94f1f05f52 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1131,7 +1131,8 @@ CREATE VIEW pg_stat_user_functions AS
             P.proname AS funcname,
             pg_stat_get_function_calls(P.oid) AS calls,
             pg_stat_get_function_total_time(P.oid) AS total_time,
-            pg_stat_get_function_self_time(P.oid) AS self_time
+            pg_stat_get_function_self_time(P.oid) AS self_time,
+            pg_stat_get_function_stat_reset_time(P.oid) AS stats_reset
     FROM pg_proc P LEFT JOIN pg_namespace N ON (N.oid = P.pronamespace)
     WHERE P.prolang != 12  -- fast check to eliminate built-in functions
           AND pg_stat_get_function_calls(P.oid) IS NOT NULL;
diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c
index 48f57e408e1..7ef06150df7 100644
--- a/src/backend/utils/activity/pgstat.c
+++ b/src/backend/utils/activity/pgstat.c
@@ -328,6 +328,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
 		.pending_size = sizeof(PgStat_FunctionCounts),
 
 		.flush_pending_cb = pgstat_function_flush_cb,
+		.reset_timestamp_cb = pgstat_function_reset_timestamp_cb,
 	},
 
 	[PGSTAT_KIND_REPLSLOT] = {
diff --git a/src/backend/utils/activity/pgstat_function.c b/src/backend/utils/activity/pgstat_function.c
index 6214f93d36e..b5db9d15e07 100644
--- a/src/backend/utils/activity/pgstat_function.c
+++ b/src/backend/utils/activity/pgstat_function.c
@@ -214,6 +214,12 @@ pgstat_function_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 	return true;
 }
 
+void
+pgstat_function_reset_timestamp_cb(PgStatShared_Common *header, TimestampTz ts)
+{
+	((PgStatShared_Function *) header)->stats.stat_reset_timestamp = ts;
+}
+
 /*
  * find any existing PgStat_FunctionCounts entry for specified function
  *
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 7e89a8048d5..3802a4cb888 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -204,6 +204,24 @@ PG_STAT_GET_FUNCENTRY_FLOAT8_MS(total_time)
 PG_STAT_GET_FUNCENTRY_FLOAT8_MS(self_time)
 
 Datum
+pg_stat_get_function_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	Oid			funcid = PG_GETARG_OID(0);
+	TimestampTz result;
+	PgStat_StatFuncEntry *funcentry;
+
+	if ((funcentry = pgstat_fetch_stat_funcentry(funcid)) == NULL)
+		result = 0;
+	else
+		result = funcentry->stat_reset_timestamp;
+
+	if (result == 0)
+		PG_RETURN_NULL();
+	else
+		PG_RETURN_TIMESTAMPTZ(result);
+}
+
+Datum
 pg_stat_get_backend_idset(PG_FUNCTION_ARGS)
 {
 	FuncCallContext *funcctx;