[CF 5956] v3 - Enhance statistics reset functions to return reset timestamp

This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/5956

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/CAOzEurTH9g9oirw7U8s4DrqKdr29D0z70QjSawY_F8EJ0-dgkw@mail.gmail.com
Author(s): Shinya Kato

Author: Commitfest Bot

contrib/test_decoding/expected/stats.out

@@ -47,10 +47,10 @@ SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count,
 
 RESET logical_decoding_work_mem;
 -- reset stats for one slot, others should be unaffected
-SELECT pg_stat_reset_replication_slot('regression_slot_stats1');
- pg_stat_reset_replication_slot 
---------------------------------
- 
+SELECT pg_stat_reset_replication_slot('regression_slot_stats1') IS NOT NULL AS t;
+ t 
+---
+ t
 (1 row)
 
 SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes, mem_exceeded_count = 0 AS mem_exceeded_count FROM pg_stat_replication_slots ORDER BY slot_name;
@@ -62,10 +62,10 @@ SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count,
 (3 rows)
 
 -- reset stats for all slots
-SELECT pg_stat_reset_replication_slot(NULL);
- pg_stat_reset_replication_slot 
---------------------------------
- 
+SELECT pg_stat_reset_replication_slot(NULL) IS NOT NULL AS t;
+ t 
+---
+ t
 (1 row)
 
 SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes, mem_exceeded_count = 0 AS mem_exceeded_count FROM pg_stat_replication_slots ORDER BY slot_name;
@@ -91,6 +91,25 @@ SELECT * FROM pg_stat_get_replication_slot('do-not-exist');
  do-not-exist |          0 |           0 |           0 |           0 |            0 |            0 |                  0 |          0 |           0 | 
 (1 row)
 
+-- verify physical replication slot stats are not reset
+SELECT 'init' FROM pg_create_physical_replication_slot('regression_slot_stats_physical') ps;
+ ?column? 
+----------
+ init
+(1 row)
+
+SELECT pg_stat_reset_replication_slot('regression_slot_stats_physical');
+ pg_stat_reset_replication_slot 
+--------------------------------
+ 
+(1 row)
+
+SELECT pg_drop_replication_slot('regression_slot_stats_physical');
+ pg_drop_replication_slot 
+--------------------------
+ 
+(1 row)
+
 -- spilling the xact
 BEGIN;
 INSERT INTO stats_test SELECT 'serialize-topbig--1:'||g.i FROM generate_series(1, 5000) g(i);

contrib/test_decoding/sql/stats.sql

@@ -19,18 +19,23 @@ SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count,
 RESET logical_decoding_work_mem;
 
 -- reset stats for one slot, others should be unaffected
-SELECT pg_stat_reset_replication_slot('regression_slot_stats1');
+SELECT pg_stat_reset_replication_slot('regression_slot_stats1') IS NOT NULL AS t;
 SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes, mem_exceeded_count = 0 AS mem_exceeded_count FROM pg_stat_replication_slots ORDER BY slot_name;
 
 -- reset stats for all slots
-SELECT pg_stat_reset_replication_slot(NULL);
+SELECT pg_stat_reset_replication_slot(NULL) IS NOT NULL AS t;
 SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes, mem_exceeded_count = 0 AS mem_exceeded_count FROM pg_stat_replication_slots ORDER BY slot_name;
 
 -- verify accessing/resetting stats for non-existent slot does something reasonable
 SELECT * FROM pg_stat_get_replication_slot('do-not-exist');
 SELECT pg_stat_reset_replication_slot('do-not-exist');
 SELECT * FROM pg_stat_get_replication_slot('do-not-exist');
 
+-- verify physical replication slot stats are not reset
+SELECT 'init' FROM pg_create_physical_replication_slot('regression_slot_stats_physical') ps;
+SELECT pg_stat_reset_replication_slot('regression_slot_stats_physical');
+SELECT pg_drop_replication_slot('regression_slot_stats_physical');
+
 -- spilling the xact
 BEGIN;
 INSERT INTO stats_test SELECT 'serialize-topbig--1:'||g.i FROM generate_series(1, 5000) g(i);

doc/src/sgml/monitoring.sgml

@@ -5055,10 +5055,11 @@ description | Waiting for a newly initialized WAL file to reach durable storage
          <primary>pg_stat_clear_snapshot</primary>
         </indexterm>
         <function>pg_stat_clear_snapshot</function> ()
-        <returnvalue>void</returnvalue>
+        <returnvalue>timestamp with time zone</returnvalue>
        </para>
        <para>
-        Discards the current statistics snapshot or cached information.
+        Discards the current statistics snapshot or cached information, and
+        returns the time of the discard.
        </para></entry>
       </row>
 
@@ -5068,10 +5069,11 @@ description | Waiting for a newly initialized WAL file to reach durable storage
          <primary>pg_stat_reset</primary>
         </indexterm>
         <function>pg_stat_reset</function> ()
-        <returnvalue>void</returnvalue>
+        <returnvalue>timestamp with time zone</returnvalue>
        </para>
        <para>
-        Resets all statistics counters for the current database to zero.
+        Resets all statistics counters for the current database to zero, and
+        returns the time of the reset.
        </para>
        <para>
         This function is restricted to superusers by default, but other users
@@ -5085,11 +5087,12 @@ description | Waiting for a newly initialized WAL file to reach durable storage
          <primary>pg_stat_reset_shared</primary>
         </indexterm>
         <function>pg_stat_reset_shared</function> ( [ <parameter>target</parameter> <type>text</type> <literal>DEFAULT</literal> <literal>NULL</literal> ] )
-        <returnvalue>void</returnvalue>
+        <returnvalue>timestamp with time zone</returnvalue>
        </para>
        <para>
         Resets some cluster-wide statistics counters to zero, depending on the
-        argument. <parameter>target</parameter> can be:
+        argument, and returns the time of the reset.
+        <parameter>target</parameter> can be:
        <itemizedlist>
         <listitem>
          <para>
@@ -5153,11 +5156,12 @@ description | Waiting for a newly initialized WAL file to reach durable storage
          <primary>pg_stat_reset_single_table_counters</primary>
         </indexterm>
         <function>pg_stat_reset_single_table_counters</function> ( <type>oid</type> )
-        <returnvalue>void</returnvalue>
+        <returnvalue>timestamp with time zone</returnvalue>
        </para>
        <para>
         Resets statistics for a single table or index in the current database
-        or shared across all databases in the cluster to zero.
+        or shared across all databases in the cluster to zero, and returns the
+        time of the reset.
        </para>
        <para>
         This function is restricted to superusers by default, but other users
@@ -5171,11 +5175,12 @@ description | Waiting for a newly initialized WAL file to reach durable storage
          <primary>pg_stat_reset_backend_stats</primary>
         </indexterm>
         <function>pg_stat_reset_backend_stats</function> ( <type>integer</type> )
-        <returnvalue>void</returnvalue>
+        <returnvalue>timestamp with time zone</returnvalue>
        </para>
        <para>
         Resets statistics for a single backend with the specified process ID
-        to zero.
+        to zero, and returns the time of the reset or <literal>NULL</literal>
+        if an invalid backend process ID is specified.
        </para>
        <para>
         This function is restricted to superusers by default, but other users
@@ -5189,11 +5194,11 @@ description | Waiting for a newly initialized WAL file to reach durable storage
          <primary>pg_stat_reset_single_function_counters</primary>
         </indexterm>
         <function>pg_stat_reset_single_function_counters</function> ( <type>oid</type> )
-        <returnvalue>void</returnvalue>
+        <returnvalue>timestamp with time zone</returnvalue>
        </para>
        <para>
         Resets statistics for a single function in the current database to
-        zero.
+        zero, and returns the time of the reset.
        </para>
        <para>
         This function is restricted to superusers by default, but other users
@@ -5207,11 +5212,11 @@ description | Waiting for a newly initialized WAL file to reach durable storage
          <primary>pg_stat_reset_slru</primary>
         </indexterm>
         <function>pg_stat_reset_slru</function> ( [ <parameter>target</parameter> <type>text</type> <literal>DEFAULT</literal> <literal>NULL</literal> ] )
-        <returnvalue>void</returnvalue>
+        <returnvalue>timestamp with time zone</returnvalue>
        </para>
        <para>
         Resets statistics to zero for a single SLRU cache, or for all SLRUs in
-        the cluster. If <parameter>target</parameter> is
+        the cluster, and returns the time of the reset. If <parameter>target</parameter> is
         <literal>NULL</literal> or is not specified, all the counters shown in
         the <structname>pg_stat_slru</structname> view for all SLRU caches are
         reset. The argument can be one of
@@ -5239,12 +5244,13 @@ description | Waiting for a newly initialized WAL file to reach durable storage
           <primary>pg_stat_reset_replication_slot</primary>
         </indexterm>
         <function>pg_stat_reset_replication_slot</function> ( <type>text</type> )
-        <returnvalue>void</returnvalue>
+        <returnvalue>timestamp with time zone</returnvalue>
        </para>
        <para>
-        Resets statistics of the replication slot defined by the argument. If
-        the argument is <literal>NULL</literal>, resets statistics for all
-        the replication slots.
+        Resets statistics of the replication slot defined by the argument, and
+        returns the time of the reset or <literal>NULL</literal> if the replication
+        slot defined by the argument is a physical slot. If the argument is
+        <literal>NULL</literal>, resets statistics for all the replication slots.
        </para>
        <para>
          This function is restricted to superusers by default, but other users
@@ -5258,13 +5264,13 @@ description | Waiting for a newly initialized WAL file to reach durable storage
           <primary>pg_stat_reset_subscription_stats</primary>
         </indexterm>
         <function>pg_stat_reset_subscription_stats</function> ( <type>oid</type> )
-        <returnvalue>void</returnvalue>
+        <returnvalue>timestamp with time zone</returnvalue>
        </para>
        <para>
         Resets statistics for a single subscription shown in the
-        <structname>pg_stat_subscription_stats</structname> view to zero. If
-        the argument is <literal>NULL</literal>, reset statistics for all
-        subscriptions.
+        <structname>pg_stat_subscription_stats</structname> view to zero, and
+        returns the time of the reset. If the argument is
+        <literal>NULL</literal>, reset statistics for all subscriptions.
        </para>
        <para>
         This function is restricted to superusers by default, but other users

src/backend/access/transam/xlogprefetcher.c

@@ -299,16 +299,18 @@ XLogPrefetchShmemSize(void)
 /*
  * Reset all counters to zero.
  */
-void
+TimestampTz
 XLogPrefetchResetStats(void)
 {
-	pg_atomic_write_u64(&SharedStats->reset_time, GetCurrentTimestamp());
+	TimestampTz ts = GetCurrentTimestamp();
+	pg_atomic_write_u64(&SharedStats->reset_time, ts);
 	pg_atomic_write_u64(&SharedStats->prefetch, 0);
 	pg_atomic_write_u64(&SharedStats->hit, 0);
 	pg_atomic_write_u64(&SharedStats->skip_init, 0);
 	pg_atomic_write_u64(&SharedStats->skip_new, 0);
 	pg_atomic_write_u64(&SharedStats->skip_fpw, 0);
 	pg_atomic_write_u64(&SharedStats->skip_rep, 0);
+	return ts;
 }
 
 void

src/backend/catalog/system_functions.sql

@@ -638,14 +638,14 @@ AS 'unicode_is_normalized';
 
 CREATE OR REPLACE FUNCTION
   pg_stat_reset_shared(target text DEFAULT NULL)
-RETURNS void
+RETURNS timestamp with time zone
 LANGUAGE INTERNAL
 CALLED ON NULL INPUT VOLATILE PARALLEL SAFE
 AS 'pg_stat_reset_shared';
 
 CREATE OR REPLACE FUNCTION
   pg_stat_reset_slru(target text DEFAULT NULL)
-RETURNS void
+RETURNS timestamp with time zone
 LANGUAGE INTERNAL
 CALLED ON NULL INPUT VOLATILE PARALLEL SAFE
 AS 'pg_stat_reset_slru';

src/backend/utils/activity/pgstat.c

@@ -832,14 +832,16 @@ match_db_entries(PgStatShared_HashEntry *entry, Datum match_data)
  * Permission checking for this function is managed through the normal
  * GRANT system.
  */
-void
+TimestampTz
 pgstat_reset_counters(void)
 {
 	TimestampTz ts = GetCurrentTimestamp();
 
 	pgstat_reset_matching_entries(match_db_entries,
 								  ObjectIdGetDatum(MyDatabaseId),
 								  ts);
+
+	return ts;
 }
 
 /*
@@ -851,7 +853,7 @@ pgstat_reset_counters(void)
  * Permission checking for this function is managed through the normal
  * GRANT system.
  */
-void
+TimestampTz
 pgstat_reset(PgStat_Kind kind, Oid dboid, uint64 objid)
 {
 	const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind);
@@ -865,6 +867,8 @@ pgstat_reset(PgStat_Kind kind, Oid dboid, uint64 objid)
 
 	if (!kind_info->accessed_across_databases)
 		pgstat_reset_database_timestamp(dboid, ts);
+
+	return ts;
 }
 
 /*
@@ -873,7 +877,7 @@ pgstat_reset(PgStat_Kind kind, Oid dboid, uint64 objid)
  * Permission checking for this function is managed through the normal
  * GRANT system.
  */
-void
+TimestampTz
 pgstat_reset_of_kind(PgStat_Kind kind)
 {
 	const PgStat_KindInfo *kind_info = pgstat_get_kind_info(kind);
@@ -883,8 +887,9 @@ pgstat_reset_of_kind(PgStat_Kind kind)
 		kind_info->reset_all_cb(ts);
 	else
 		pgstat_reset_entries_of_kind(kind, ts);
-}
 
+	return ts;
+}
 
 /* ------------------------------------------------------------
  * Fetching of stats
@@ -899,7 +904,7 @@ pgstat_reset_of_kind(PgStat_Kind kind)
  * the no-longer-wanted snapshot.  Updates of stats_fetch_consistency can
  * cause this routine to be called.
  */
-void
+TimestampTz
 pgstat_clear_snapshot(void)
 {
 	pgstat_assert_is_up();
@@ -929,6 +934,8 @@ pgstat_clear_snapshot(void)
 
 	/* Reset this flag, as it may be possible that a cleanup was forced. */
 	force_stats_snapshot_clear = false;
+
+	return GetCurrentTimestamp();
 }
 
 void *

src/backend/utils/activity/pgstat_replslot.c

@@ -37,11 +37,14 @@ static int	get_replslot_index(const char *name, bool need_lock);
  *
  * Permission checking for this function is managed through the normal
  * GRANT system.
+ *
+ * NB: Returns the time of the reset or 0 if it is a physical slot.
  */
-void
+TimestampTz
 pgstat_reset_replslot(const char *name)
 {
 	ReplicationSlot *slot;
+	TimestampTz ts = 0;
 
 	Assert(name != NULL);
 
@@ -61,10 +64,12 @@ pgstat_reset_replslot(const char *name)
 	 * as we collect stats only for logical slots.
 	 */
 	if (SlotIsLogical(slot))
-		pgstat_reset(PGSTAT_KIND_REPLSLOT, InvalidOid,
+		ts = pgstat_reset(PGSTAT_KIND_REPLSLOT, InvalidOid,
 					 ReplicationSlotIndex(slot));
 
 	LWLockRelease(ReplicationSlotControlLock);
+
+	return ts;
 }
 
 /*

src/backend/utils/activity/pgstat_slru.c

@@ -41,14 +41,16 @@ static bool have_slrustats = false;
  * Permission checking for this function is managed through the normal
  * GRANT system.
  */
-void
+TimestampTz
 pgstat_reset_slru(const char *name)
 {
 	TimestampTz ts = GetCurrentTimestamp();
 
 	Assert(name != NULL);
 
 	pgstat_reset_slru_counter_internal(pgstat_get_slru_index(name), ts);
+
+	return ts;
 }
 
 /*