Introduce a new view for checkpointer related stats

From 724d9bee5bc3bc124dd37909878a6450c4fe1019 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Tue, 22 Nov 2022 12:06:20 +0000
Subject: [PATCH v2] Introduce a new view for checkpointer related stats

pg_stat_bgwriter view currently reports checkpointer stats as well.
It is that way because historically checkpointer was part of
bgwriter until the commits 806a2ae and bf405ba, that went into
PG 9.2, separated them out.

It is time for us to separate checkpointer stats to its own view
called pg_stat_checkpointer.

Bump catalog version.
---
 doc/src/sgml/monitoring.sgml                  | 110 +++++++++++++-----
 src/backend/catalog/system_views.sql          |  18 +--
 .../utils/activity/pgstat_checkpointer.c      |   1 +
 src/backend/utils/adt/pgstatfuncs.c           |  19 +--
 src/include/catalog/pg_proc.dat               |  22 ++--
 src/include/pgstat.h                          |   1 +
 src/test/recovery/t/029_stats_restart.pl      |   6 +-
 src/test/regress/expected/rules.out           |  15 +--
 src/test/regress/expected/stats.out           |  21 +++-
 src/test/regress/sql/stats.sql                |  12 +-
 10 files changed, 155 insertions(+), 70 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index e2426f7210..e532c4be08 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -448,6 +448,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
      </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
+      <entry>One row only, showing statistics about the
+       checkpointer process's activity. See
+       <link linkend="monitoring-pg-stat-checkpointer-view">
+       <structname>pg_stat_checkpointer</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_wal</structname><indexterm><primary>pg_stat_wal</primary></indexterm></entry>
       <entry>One row only, showing statistics about WAL activity. See
@@ -3631,7 +3640,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
 
   <para>
    The <structname>pg_stat_bgwriter</structname> view will always have a
-   single row, containing global data for the cluster.
+   single row, containing data about the bgwriter of the cluster.
   </para>
 
   <table id="pg-stat-bgwriter-view" xreflabel="pg_stat_bgwriter">
@@ -3651,97 +3660,138 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
     <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_timed</structfield> <type>bigint</type>
+       <structfield>buffers_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of scheduled checkpoints that have been performed
+       Number of buffers written by the background writer
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_req</structfield> <type>bigint</type>
+       <structfield>maxwritten_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of requested checkpoints that have been performed
+       Number of times the background writer stopped a cleaning
+       scan because it had written too many buffers
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
+       <structfield>buffers_alloc</structfield> <type>bigint</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are written to disk, in milliseconds
+       Number of buffers allocated
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are synchronized to disk, in
-       milliseconds
+       Time at which these statistics were last reset
       </para></entry>
      </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
+
+ <sect2 id="monitoring-pg-stat-checkpointer-view">
+  <title><structname>pg_stat_checkpointer</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_checkpointer</primary>
+  </indexterm>
 
+  <para>
+   The <structname>pg_stat_checkpointer</structname> view will always have a
+   single row, containing data about the checkpointer process of the cluster.
+  </para>
+
+  <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
+   <title><structname>pg_stat_checkpointer</structname> View</title>
+   <tgroup cols="1">
+    <thead>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
+       Column Type
       </para>
       <para>
-       Number of buffers written during checkpoints
+       Description
       </para></entry>
      </row>
+    </thead>
 
+    <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_clean</structfield> <type>bigint</type>
+       <structfield>checkpoints_timed</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written by the background writer
+       Number of scheduled checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>maxwritten_clean</structfield> <type>bigint</type>
+       <structfield>checkpoints_req</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of times the background writer stopped a cleaning
-       scan because it had written too many buffers
+       Number of requested checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend</structfield> <type>bigint</type>
+       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of buffers written directly by a backend
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are written to disk, in milliseconds
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
+       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of times a backend had to execute its own
-       <function>fsync</function> call (normally the background writer handles those
-       even when the backend does its own write)
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are synchronized to disk, in
+       milliseconds
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_alloc</structfield> <type>bigint</type>
+       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers allocated
+       Number of buffers written during checkpoints
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_backend</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written directly by a backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a backend had to execute its own
+       <function>fsync</function> call (normally the checkpointer handles those
+       even when the backend does its own write)
       </para></entry>
      </row>
 
@@ -5391,8 +5441,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         Resets some cluster-wide statistics counters to zero, depending on the
         argument.  The argument can be <literal>bgwriter</literal> to reset
         all the counters shown in
-        the <structname>pg_stat_bgwriter</structname>
-        view, <literal>archiver</literal> to reset all the counters shown in
+        the <structname>pg_stat_bgwriter</structname> view,
+        <literal>checkpointer</literal> to reset all the counters shown in
+        the <structname>pg_stat_checkpointer</structname> view,
+        <literal>archiver</literal> to reset all the counters shown in
         the <structname>pg_stat_archiver</structname> view,
         <literal>wal</literal> to reset all the counters shown in the
         <structname>pg_stat_wal</structname> view or
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 2d8104b090..131d949dfb 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1105,18 +1105,22 @@ CREATE VIEW pg_stat_archiver AS
 
 CREATE VIEW pg_stat_bgwriter AS
     SELECT
-        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-        pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-        pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-        pg_stat_get_buf_written_backend() AS buffers_backend,
-        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_checkpointer AS
+    SELECT
+        pg_stat_get_timed_checkpoints() AS checkpoints_timed,
+        pg_stat_get_requested_checkpoints() AS checkpoints_req,
+        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+        pg_stat_get_buf_written_checkpoints() AS buffers_checkpoint,
+        pg_stat_get_buf_written_backend() AS buffers_backend,
+        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
+        pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
+
 CREATE VIEW pg_stat_wal AS
     SELECT
         w.wal_records,
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index af8d513e7b..2757a10b7e 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -89,6 +89,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
 									&stats_shmem->stats,
 									sizeof(stats_shmem->stats),
 									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
 	LWLockRelease(&stats_shmem->lock);
 }
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index ae3365d917..38a2595cdd 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1662,19 +1662,19 @@ pg_stat_get_db_sessions_killed(PG_FUNCTION_ARGS)
 }
 
 Datum
-pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_timed_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_requested_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_buf_written_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
 }
@@ -1707,6 +1707,12 @@ pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
 					 pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
 }
 
+Datum
+pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
+}
+
 Datum
 pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 {
@@ -2082,14 +2088,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 	if (strcmp(target, "archiver") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
 	else if (strcmp(target, "bgwriter") == 0)
-	{
-		/*
-		 * Historically checkpointer was part of bgwriter, continue to reset
-		 * both for now.
-		 */
 		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+	else if (strcmp(target, "checkpointer") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
-	}
 	else if (strcmp(target, "recovery_prefetch") == 0)
 		XLogPrefetchResetStats();
 	else if (strcmp(target, "wal") == 0)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index f15aa2dbb1..ec97c6015e 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5628,20 +5628,24 @@
   proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}',
   prosrc => 'pg_stat_get_archiver' },
 { oid => '2769',
-  descr => 'statistics: number of timed checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_timed_checkpoints', provolatile => 's',
+  descr => 'statistics: number of timed checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_timed_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_timed_checkpoints' },
+  prosrc => 'pg_stat_get_timed_checkpoints' },
 { oid => '2770',
-  descr => 'statistics: number of backend requested checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_requested_checkpoints', provolatile => 's',
+  descr => 'statistics: number of backend requested checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_requested_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_requested_checkpoints' },
+  prosrc => 'pg_stat_get_requested_checkpoints' },
 { oid => '2771',
-  descr => 'statistics: number of buffers written by the bgwriter during checkpoints',
-  proname => 'pg_stat_get_bgwriter_buf_written_checkpoints', provolatile => 's',
+  descr => 'statistics: number of buffers written by the checkpointer',
+  proname => 'pg_stat_get_buf_written_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_buf_written_checkpoints' },
+  prosrc => 'pg_stat_get_buf_written_checkpoints' },
+{ oid => '8206', descr => 'statistics: last reset for the checkpointer',
+  proname => 'pg_stat_get_checkpointer_stat_reset_time', provolatile => 's',
+  proparallel => 'r', prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_stat_get_checkpointer_stat_reset_time' },
 { oid => '2772',
   descr => 'statistics: number of buffers written by the bgwriter for cleaning dirty buffers',
   proname => 'pg_stat_get_bgwriter_buf_written_clean', provolatile => 's',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9e2ce6f011..e23d80bba8 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -274,6 +274,7 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter buf_written_checkpoints;
 	PgStat_Counter buf_written_backend;
 	PgStat_Counter buf_fsync_backend;
+	TimestampTz stat_reset_timestamp;
 } PgStat_CheckpointerStats;
 
 typedef struct PgStat_StatDBEntry
diff --git a/src/test/recovery/t/029_stats_restart.pl b/src/test/recovery/t/029_stats_restart.pl
index 1bf7b568cc..f4e262a4bf 100644
--- a/src/test/recovery/t/029_stats_restart.pl
+++ b/src/test/recovery/t/029_stats_restart.pl
@@ -173,7 +173,7 @@ is($wal_start->{reset}, $wal_restart->{reset},
 
 ## Check that checkpoint stats are reset, WAL stats aren't affected
 
-$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('bgwriter')");
+$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('checkpointer')");
 
 $sect = "post ckpt reset";
 my $ckpt_reset     = checkpoint_stats();
@@ -323,9 +323,9 @@ sub checkpoint_stats
 	my %results;
 
 	$results{count} = $node->safe_psql($connect_db,
-		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter");
+		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_checkpointer");
 	$results{reset} = $node->safe_psql($connect_db,
-		"SELECT stats_reset FROM pg_stat_bgwriter");
+		"SELECT stats_reset FROM pg_stat_checkpointer");
 
 	return \%results;
 }
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 624d0e5aae..4496619271 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1811,17 +1811,18 @@ pg_stat_archiver| SELECT s.archived_count,
     s.last_failed_time,
     s.stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
-pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
+pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
+    pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
+    pg_stat_get_buf_alloc() AS buffers_alloc,
+    pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+pg_stat_checkpointer| SELECT pg_stat_get_timed_checkpoints() AS checkpoints_timed,
+    pg_stat_get_requested_checkpoints() AS checkpoints_req,
     pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
     pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
-    pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
-    pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
+    pg_stat_get_buf_written_checkpoints() AS buffers_checkpoint,
     pg_stat_get_buf_written_backend() AS buffers_backend,
     pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
-    pg_stat_get_buf_alloc() AS buffers_alloc,
-    pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT d.oid AS datid,
     d.datname,
         CASE
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 1d84407a03..8ed7f895b2 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -782,8 +782,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
  t
 (1 row)
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
 CREATE TEMP TABLE test_stats_temp AS SELECT 17;
@@ -793,7 +793,7 @@ DROP TABLE test_stats_temp;
 -- results of the first.
 CHECKPOINT;
 CHECKPOINT;
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_checkpointer;
  ?column? 
 ----------
  t
@@ -884,6 +884,21 @@ SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 (1 row)
 
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index b4d6753c71..c8c24abea8 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -387,8 +387,8 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
 SELECT pg_stat_force_next_flush();
 SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database());
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
@@ -402,7 +402,7 @@ DROP TABLE test_stats_temp;
 CHECKPOINT;
 CHECKPOINT;
 
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_checkpointer;
 SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
 
 -- Test pg_stat_get_backend_idset() and some allied functions.
@@ -440,6 +440,12 @@ SELECT pg_stat_reset_shared('bgwriter');
 SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
 
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
-- 
2.34.1

From ec09bfcde836cb23f090fd6088b89f0fb9a68000 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Mon, 28 Nov 2022 10:07:55 +0000
Subject: [PATCH v3] Introduce a new view for checkpointer related stats

pg_stat_bgwriter view currently reports checkpointer stats as well.
It is that way because historically checkpointer was part of
bgwriter until the commits 806a2ae and bf405ba, that went into
PG 9.2, separated them out.

It is time for us to separate checkpointer stats to its own view
called pg_stat_checkpointer.

For now, we deprecate the use of these checkpointer related fields
under pg_stat_bgwriter view for smoother transitioning.
Eventually, we need to remove them from pg_stat_bgwriter view.

Bump catalog version.

Author: Bharath Rupireddy
Reviewed-by: Andres Freund, Bertrand Drouvot
Discussion: https://www.postgresql.org/message-id/CALj2ACVxX2ii=66RypXRweZe2EsBRiPMj0aHfRfHUeXJcC7kHg@mail.gmail.com
---
 doc/src/sgml/monitoring.sgml                  | 165 +++++++++++++++++-
 src/backend/catalog/system_views.sql          |  17 +-
 .../utils/activity/pgstat_checkpointer.c      |   1 +
 src/backend/utils/adt/pgstatfuncs.c           |  19 +-
 src/include/catalog/pg_proc.dat               |  22 ++-
 src/include/pgstat.h                          |   1 +
 src/test/recovery/t/029_stats_restart.pl      |   6 +-
 src/test/regress/expected/rules.out           |  14 +-
 src/test/regress/expected/stats.out           |  21 ++-
 src/test/regress/sql/stats.sql                |  12 +-
 10 files changed, 236 insertions(+), 42 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 5579b8b9e0..c69d3b21c0 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -448,6 +448,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
      </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
+      <entry>One row only, showing statistics about the
+       checkpointer process's activity. See
+       <link linkend="monitoring-pg-stat-checkpointer-view">
+       <structname>pg_stat_checkpointer</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_wal</structname><indexterm><primary>pg_stat_wal</primary></indexterm></entry>
       <entry>One row only, showing statistics about WAL activity. See
@@ -3654,7 +3663,11 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>checkpoints_timed</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of scheduled checkpoints that have been performed
+       Number of scheduled checkpoints that have been performed. Use of this
+       field under <structname>pg_stat_bgwriter</structname> view has been
+       deprecated, because the field actually shows checkpointer process
+       activity and is moved to a new view called
+       <structname>pg_stat_checkpointer</structname>.
       </para></entry>
      </row>
 
@@ -3663,7 +3676,11 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>checkpoints_req</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of requested checkpoints that have been performed
+       Number of requested checkpoints that have been performed. Use of this
+       field under <structname>pg_stat_bgwriter</structname> view has been
+       deprecated, because the field actually shows checkpointer process
+       activity and is moved to a new view called
+       <structname>pg_stat_checkpointer</structname>.
       </para></entry>
      </row>
 
@@ -3673,7 +3690,11 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </para>
       <para>
        Total amount of time that has been spent in the portion of
-       checkpoint processing where files are written to disk, in milliseconds
+       checkpoint processing where files are written to disk, in milliseconds.
+       Use of this field under <structname>pg_stat_bgwriter</structname> view
+       has been deprecated, because the field actually shows checkpointer
+       process activity and is moved to a new view called
+       <structname>pg_stat_checkpointer</structname>.
       </para></entry>
      </row>
 
@@ -3684,7 +3705,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       <para>
        Total amount of time that has been spent in the portion of
        checkpoint processing where files are synchronized to disk, in
-       milliseconds
+       milliseconds. Use of this field under
+       <structname>pg_stat_bgwriter</structname> view has been deprecated,
+       because the field actually shows checkpointer process activity and is
+       moved to a new view called <structname>pg_stat_checkpointer</structname>.
       </para></entry>
      </row>
 
@@ -3693,7 +3717,11 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>buffers_checkpoint</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written during checkpoints
+       Number of buffers written during checkpoints. Use of this field under
+       <structname>pg_stat_bgwriter</structname> view has been deprecated,
+       because the field actually shows checkpointer process activity and is
+       moved to a new view called
+       <structname>pg_stat_checkpointer</structname>.
       </para></entry>
      </row>
 
@@ -3721,7 +3749,11 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>buffers_backend</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written directly by a backend
+       Number of buffers written directly by a backend. Use of this field
+       under <structname>pg_stat_bgwriter</structname> view has been
+       deprecated, because the field actually shows checkpointer process
+       activity and is moved to a new view called
+       <structname>pg_stat_checkpointer</structname>.
       </para></entry>
      </row>
 
@@ -3732,7 +3764,11 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       <para>
        Number of times a backend had to execute its own
        <function>fsync</function> call (normally the background writer handles those
-       even when the backend does its own write)
+       even when the backend does its own write). Use of this field under
+       <structname>pg_stat_bgwriter</structname> view has been deprecated,
+       because the field actually shows checkpointer process activity and is
+       moved to a new view called
+       <structname>pg_stat_checkpointer</structname>.
       </para></entry>
      </row>
 
@@ -3759,6 +3795,115 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
 
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-checkpointer-view">
+  <title><structname>pg_stat_checkpointer</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_checkpointer</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_checkpointer</structname> view will always have a
+   single row, containing data about the checkpointer process of the cluster.
+  </para>
+
+  <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
+   <title><structname>pg_stat_checkpointer</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>checkpoints_timed</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of scheduled checkpoints that have been performed
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>checkpoints_req</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of requested checkpoints that have been performed
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
+      </para>
+      <para>
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are written to disk, in milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+      </para>
+      <para>
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are synchronized to disk, in
+       milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written during checkpoints
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_backend</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written directly by a backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a backend had to execute its own
+       <function>fsync</function> call (normally the checkpointer handles those
+       even when the backend does its own write)
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+      </para>
+      <para>
+       Time at which these statistics were last reset
+      </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-wal-view">
    <title><structname>pg_stat_wal</structname></title>
 
@@ -5391,8 +5536,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         Resets some cluster-wide statistics counters to zero, depending on the
         argument.  The argument can be <literal>bgwriter</literal> to reset
         all the counters shown in
-        the <structname>pg_stat_bgwriter</structname>
-        view, <literal>archiver</literal> to reset all the counters shown in
+        the <structname>pg_stat_bgwriter</structname> view,
+        <literal>checkpointer</literal> to reset all the counters shown in
+        the <structname>pg_stat_checkpointer</structname> view,
+        <literal>archiver</literal> to reset all the counters shown in
         the <structname>pg_stat_archiver</structname> view,
         <literal>wal</literal> to reset all the counters shown in the
         <structname>pg_stat_wal</structname> view or
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 2d8104b090..e4e49efe76 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1105,11 +1105,11 @@ CREATE VIEW pg_stat_archiver AS
 
 CREATE VIEW pg_stat_bgwriter AS
     SELECT
-        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-        pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
+        pg_stat_get_timed_checkpoints() AS checkpoints_timed,
+        pg_stat_get_requested_checkpoints() AS checkpoints_req,
         pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
         pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-        pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
+        pg_stat_get_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
         pg_stat_get_buf_written_backend() AS buffers_backend,
@@ -1117,6 +1117,17 @@ CREATE VIEW pg_stat_bgwriter AS
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_checkpointer AS
+    SELECT
+        pg_stat_get_timed_checkpoints() AS checkpoints_timed,
+        pg_stat_get_requested_checkpoints() AS checkpoints_req,
+        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+        pg_stat_get_buf_written_checkpoints() AS buffers_checkpoint,
+        pg_stat_get_buf_written_backend() AS buffers_backend,
+        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
+        pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
+
 CREATE VIEW pg_stat_wal AS
     SELECT
         w.wal_records,
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index af8d513e7b..2757a10b7e 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -89,6 +89,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
 									&stats_shmem->stats,
 									sizeof(stats_shmem->stats),
 									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
 	LWLockRelease(&stats_shmem->lock);
 }
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index ae3365d917..38a2595cdd 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1662,19 +1662,19 @@ pg_stat_get_db_sessions_killed(PG_FUNCTION_ARGS)
 }
 
 Datum
-pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_timed_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_requested_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_buf_written_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
 }
@@ -1707,6 +1707,12 @@ pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
 					 pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
 }
 
+Datum
+pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
+}
+
 Datum
 pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 {
@@ -2082,14 +2088,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 	if (strcmp(target, "archiver") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
 	else if (strcmp(target, "bgwriter") == 0)
-	{
-		/*
-		 * Historically checkpointer was part of bgwriter, continue to reset
-		 * both for now.
-		 */
 		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+	else if (strcmp(target, "checkpointer") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
-	}
 	else if (strcmp(target, "recovery_prefetch") == 0)
 		XLogPrefetchResetStats();
 	else if (strcmp(target, "wal") == 0)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index f9301b2627..1b24969a01 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5628,20 +5628,24 @@
   proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}',
   prosrc => 'pg_stat_get_archiver' },
 { oid => '2769',
-  descr => 'statistics: number of timed checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_timed_checkpoints', provolatile => 's',
+  descr => 'statistics: number of timed checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_timed_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_timed_checkpoints' },
+  prosrc => 'pg_stat_get_timed_checkpoints' },
 { oid => '2770',
-  descr => 'statistics: number of backend requested checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_requested_checkpoints', provolatile => 's',
+  descr => 'statistics: number of backend requested checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_requested_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_requested_checkpoints' },
+  prosrc => 'pg_stat_get_requested_checkpoints' },
 { oid => '2771',
-  descr => 'statistics: number of buffers written by the bgwriter during checkpoints',
-  proname => 'pg_stat_get_bgwriter_buf_written_checkpoints', provolatile => 's',
+  descr => 'statistics: number of buffers written by the checkpointer',
+  proname => 'pg_stat_get_buf_written_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_buf_written_checkpoints' },
+  prosrc => 'pg_stat_get_buf_written_checkpoints' },
+{ oid => '8206', descr => 'statistics: last reset for the checkpointer',
+  proname => 'pg_stat_get_checkpointer_stat_reset_time', provolatile => 's',
+  proparallel => 'r', prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_stat_get_checkpointer_stat_reset_time' },
 { oid => '2772',
   descr => 'statistics: number of buffers written by the bgwriter for cleaning dirty buffers',
   proname => 'pg_stat_get_bgwriter_buf_written_clean', provolatile => 's',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9e2ce6f011..e23d80bba8 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -274,6 +274,7 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter buf_written_checkpoints;
 	PgStat_Counter buf_written_backend;
 	PgStat_Counter buf_fsync_backend;
+	TimestampTz stat_reset_timestamp;
 } PgStat_CheckpointerStats;
 
 typedef struct PgStat_StatDBEntry
diff --git a/src/test/recovery/t/029_stats_restart.pl b/src/test/recovery/t/029_stats_restart.pl
index 1bf7b568cc..f4e262a4bf 100644
--- a/src/test/recovery/t/029_stats_restart.pl
+++ b/src/test/recovery/t/029_stats_restart.pl
@@ -173,7 +173,7 @@ is($wal_start->{reset}, $wal_restart->{reset},
 
 ## Check that checkpoint stats are reset, WAL stats aren't affected
 
-$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('bgwriter')");
+$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('checkpointer')");
 
 $sect = "post ckpt reset";
 my $ckpt_reset     = checkpoint_stats();
@@ -323,9 +323,9 @@ sub checkpoint_stats
 	my %results;
 
 	$results{count} = $node->safe_psql($connect_db,
-		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter");
+		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_checkpointer");
 	$results{reset} = $node->safe_psql($connect_db,
-		"SELECT stats_reset FROM pg_stat_bgwriter");
+		"SELECT stats_reset FROM pg_stat_checkpointer");
 
 	return \%results;
 }
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 37c1c86473..81bb0adfc3 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1814,17 +1814,25 @@ pg_stat_archiver| SELECT s.archived_count,
     s.last_failed_time,
     s.stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
-pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
+pg_stat_bgwriter| SELECT pg_stat_get_timed_checkpoints() AS checkpoints_timed,
+    pg_stat_get_requested_checkpoints() AS checkpoints_req,
     pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
     pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
+    pg_stat_get_buf_written_checkpoints() AS buffers_checkpoint,
     pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_written_backend() AS buffers_backend,
     pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+pg_stat_checkpointer| SELECT pg_stat_get_timed_checkpoints() AS checkpoints_timed,
+    pg_stat_get_requested_checkpoints() AS checkpoints_req,
+    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+    pg_stat_get_buf_written_checkpoints() AS buffers_checkpoint,
+    pg_stat_get_buf_written_backend() AS buffers_backend,
+    pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
+    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT d.oid AS datid,
     d.datname,
         CASE
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 1d84407a03..8ed7f895b2 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -782,8 +782,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
  t
 (1 row)
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
 CREATE TEMP TABLE test_stats_temp AS SELECT 17;
@@ -793,7 +793,7 @@ DROP TABLE test_stats_temp;
 -- results of the first.
 CHECKPOINT;
 CHECKPOINT;
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_checkpointer;
  ?column? 
 ----------
  t
@@ -884,6 +884,21 @@ SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 (1 row)
 
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index b4d6753c71..c8c24abea8 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -387,8 +387,8 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
 SELECT pg_stat_force_next_flush();
 SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database());
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
@@ -402,7 +402,7 @@ DROP TABLE test_stats_temp;
 CHECKPOINT;
 CHECKPOINT;
 
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_checkpointer;
 SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
 
 -- Test pg_stat_get_backend_idset() and some allied functions.
@@ -440,6 +440,12 @@ SELECT pg_stat_reset_shared('bgwriter');
 SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
 
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
-- 
2.34.1

From 724d9bee5bc3bc124dd37909878a6450c4fe1019 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Tue, 22 Nov 2022 12:06:20 +0000
Subject: [PATCH v2] Introduce a new view for checkpointer related stats

pg_stat_bgwriter view currently reports checkpointer stats as well.
It is that way because historically checkpointer was part of
bgwriter until the commits 806a2ae and bf405ba, that went into
PG 9.2, separated them out.

It is time for us to separate checkpointer stats to its own view
called pg_stat_checkpointer.

Bump catalog version.
---
 doc/src/sgml/monitoring.sgml                  | 110 +++++++++++++-----
 src/backend/catalog/system_views.sql          |  18 +--
 .../utils/activity/pgstat_checkpointer.c      |   1 +
 src/backend/utils/adt/pgstatfuncs.c           |  19 +--
 src/include/catalog/pg_proc.dat               |  22 ++--
 src/include/pgstat.h                          |   1 +
 src/test/recovery/t/029_stats_restart.pl      |   6 +-
 src/test/regress/expected/rules.out           |  15 +--
 src/test/regress/expected/stats.out           |  21 +++-
 src/test/regress/sql/stats.sql                |  12 +-
 10 files changed, 155 insertions(+), 70 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index e2426f7210..e532c4be08 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -448,6 +448,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
      </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
+      <entry>One row only, showing statistics about the
+       checkpointer process's activity. See
+       <link linkend="monitoring-pg-stat-checkpointer-view">
+       <structname>pg_stat_checkpointer</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_wal</structname><indexterm><primary>pg_stat_wal</primary></indexterm></entry>
       <entry>One row only, showing statistics about WAL activity. See
@@ -3631,7 +3640,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
 
   <para>
    The <structname>pg_stat_bgwriter</structname> view will always have a
-   single row, containing global data for the cluster.
+   single row, containing data about the bgwriter of the cluster.
   </para>
 
   <table id="pg-stat-bgwriter-view" xreflabel="pg_stat_bgwriter">
@@ -3651,97 +3660,138 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
     <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_timed</structfield> <type>bigint</type>
+       <structfield>buffers_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of scheduled checkpoints that have been performed
+       Number of buffers written by the background writer
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_req</structfield> <type>bigint</type>
+       <structfield>maxwritten_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of requested checkpoints that have been performed
+       Number of times the background writer stopped a cleaning
+       scan because it had written too many buffers
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
+       <structfield>buffers_alloc</structfield> <type>bigint</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are written to disk, in milliseconds
+       Number of buffers allocated
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are synchronized to disk, in
-       milliseconds
+       Time at which these statistics were last reset
       </para></entry>
      </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
+
+ <sect2 id="monitoring-pg-stat-checkpointer-view">
+  <title><structname>pg_stat_checkpointer</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_checkpointer</primary>
+  </indexterm>
 
+  <para>
+   The <structname>pg_stat_checkpointer</structname> view will always have a
+   single row, containing data about the checkpointer process of the cluster.
+  </para>
+
+  <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
+   <title><structname>pg_stat_checkpointer</structname> View</title>
+   <tgroup cols="1">
+    <thead>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
+       Column Type
       </para>
       <para>
-       Number of buffers written during checkpoints
+       Description
       </para></entry>
      </row>
+    </thead>
 
+    <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_clean</structfield> <type>bigint</type>
+       <structfield>checkpoints_timed</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written by the background writer
+       Number of scheduled checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>maxwritten_clean</structfield> <type>bigint</type>
+       <structfield>checkpoints_req</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of times the background writer stopped a cleaning
-       scan because it had written too many buffers
+       Number of requested checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend</structfield> <type>bigint</type>
+       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of buffers written directly by a backend
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are written to disk, in milliseconds
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
+       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of times a backend had to execute its own
-       <function>fsync</function> call (normally the background writer handles those
-       even when the backend does its own write)
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are synchronized to disk, in
+       milliseconds
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_alloc</structfield> <type>bigint</type>
+       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers allocated
+       Number of buffers written during checkpoints
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_backend</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written directly by a backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a backend had to execute its own
+       <function>fsync</function> call (normally the checkpointer handles those
+       even when the backend does its own write)
       </para></entry>
      </row>
 
@@ -5391,8 +5441,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         Resets some cluster-wide statistics counters to zero, depending on the
         argument.  The argument can be <literal>bgwriter</literal> to reset
         all the counters shown in
-        the <structname>pg_stat_bgwriter</structname>
-        view, <literal>archiver</literal> to reset all the counters shown in
+        the <structname>pg_stat_bgwriter</structname> view,
+        <literal>checkpointer</literal> to reset all the counters shown in
+        the <structname>pg_stat_checkpointer</structname> view,
+        <literal>archiver</literal> to reset all the counters shown in
         the <structname>pg_stat_archiver</structname> view,
         <literal>wal</literal> to reset all the counters shown in the
         <structname>pg_stat_wal</structname> view or
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 2d8104b090..131d949dfb 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1105,18 +1105,22 @@ CREATE VIEW pg_stat_archiver AS
 
 CREATE VIEW pg_stat_bgwriter AS
     SELECT
-        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-        pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-        pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-        pg_stat_get_buf_written_backend() AS buffers_backend,
-        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_checkpointer AS
+    SELECT
+        pg_stat_get_timed_checkpoints() AS checkpoints_timed,
+        pg_stat_get_requested_checkpoints() AS checkpoints_req,
+        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+        pg_stat_get_buf_written_checkpoints() AS buffers_checkpoint,
+        pg_stat_get_buf_written_backend() AS buffers_backend,
+        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
+        pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
+
 CREATE VIEW pg_stat_wal AS
     SELECT
         w.wal_records,
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index af8d513e7b..2757a10b7e 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -89,6 +89,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
 									&stats_shmem->stats,
 									sizeof(stats_shmem->stats),
 									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
 	LWLockRelease(&stats_shmem->lock);
 }
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index ae3365d917..38a2595cdd 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1662,19 +1662,19 @@ pg_stat_get_db_sessions_killed(PG_FUNCTION_ARGS)
 }
 
 Datum
-pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_timed_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_requested_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_buf_written_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
 }
@@ -1707,6 +1707,12 @@ pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
 					 pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
 }
 
+Datum
+pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
+}
+
 Datum
 pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 {
@@ -2082,14 +2088,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 	if (strcmp(target, "archiver") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
 	else if (strcmp(target, "bgwriter") == 0)
-	{
-		/*
-		 * Historically checkpointer was part of bgwriter, continue to reset
-		 * both for now.
-		 */
 		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+	else if (strcmp(target, "checkpointer") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
-	}
 	else if (strcmp(target, "recovery_prefetch") == 0)
 		XLogPrefetchResetStats();
 	else if (strcmp(target, "wal") == 0)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index f15aa2dbb1..ec97c6015e 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5628,20 +5628,24 @@
   proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}',
   prosrc => 'pg_stat_get_archiver' },
 { oid => '2769',
-  descr => 'statistics: number of timed checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_timed_checkpoints', provolatile => 's',
+  descr => 'statistics: number of timed checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_timed_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_timed_checkpoints' },
+  prosrc => 'pg_stat_get_timed_checkpoints' },
 { oid => '2770',
-  descr => 'statistics: number of backend requested checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_requested_checkpoints', provolatile => 's',
+  descr => 'statistics: number of backend requested checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_requested_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_requested_checkpoints' },
+  prosrc => 'pg_stat_get_requested_checkpoints' },
 { oid => '2771',
-  descr => 'statistics: number of buffers written by the bgwriter during checkpoints',
-  proname => 'pg_stat_get_bgwriter_buf_written_checkpoints', provolatile => 's',
+  descr => 'statistics: number of buffers written by the checkpointer',
+  proname => 'pg_stat_get_buf_written_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_buf_written_checkpoints' },
+  prosrc => 'pg_stat_get_buf_written_checkpoints' },
+{ oid => '8206', descr => 'statistics: last reset for the checkpointer',
+  proname => 'pg_stat_get_checkpointer_stat_reset_time', provolatile => 's',
+  proparallel => 'r', prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_stat_get_checkpointer_stat_reset_time' },
 { oid => '2772',
   descr => 'statistics: number of buffers written by the bgwriter for cleaning dirty buffers',
   proname => 'pg_stat_get_bgwriter_buf_written_clean', provolatile => 's',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9e2ce6f011..e23d80bba8 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -274,6 +274,7 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter buf_written_checkpoints;
 	PgStat_Counter buf_written_backend;
 	PgStat_Counter buf_fsync_backend;
+	TimestampTz stat_reset_timestamp;
 } PgStat_CheckpointerStats;
 
 typedef struct PgStat_StatDBEntry
diff --git a/src/test/recovery/t/029_stats_restart.pl b/src/test/recovery/t/029_stats_restart.pl
index 1bf7b568cc..f4e262a4bf 100644
--- a/src/test/recovery/t/029_stats_restart.pl
+++ b/src/test/recovery/t/029_stats_restart.pl
@@ -173,7 +173,7 @@ is($wal_start->{reset}, $wal_restart->{reset},
 
 ## Check that checkpoint stats are reset, WAL stats aren't affected
 
-$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('bgwriter')");
+$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('checkpointer')");
 
 $sect = "post ckpt reset";
 my $ckpt_reset     = checkpoint_stats();
@@ -323,9 +323,9 @@ sub checkpoint_stats
 	my %results;
 
 	$results{count} = $node->safe_psql($connect_db,
-		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter");
+		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_checkpointer");
 	$results{reset} = $node->safe_psql($connect_db,
-		"SELECT stats_reset FROM pg_stat_bgwriter");
+		"SELECT stats_reset FROM pg_stat_checkpointer");
 
 	return \%results;
 }
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 624d0e5aae..4496619271 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1811,17 +1811,18 @@ pg_stat_archiver| SELECT s.archived_count,
     s.last_failed_time,
     s.stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
-pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
+pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
+    pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
+    pg_stat_get_buf_alloc() AS buffers_alloc,
+    pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+pg_stat_checkpointer| SELECT pg_stat_get_timed_checkpoints() AS checkpoints_timed,
+    pg_stat_get_requested_checkpoints() AS checkpoints_req,
     pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
     pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
-    pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
-    pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
+    pg_stat_get_buf_written_checkpoints() AS buffers_checkpoint,
     pg_stat_get_buf_written_backend() AS buffers_backend,
     pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
-    pg_stat_get_buf_alloc() AS buffers_alloc,
-    pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT d.oid AS datid,
     d.datname,
         CASE
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 1d84407a03..8ed7f895b2 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -782,8 +782,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
  t
 (1 row)
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
 CREATE TEMP TABLE test_stats_temp AS SELECT 17;
@@ -793,7 +793,7 @@ DROP TABLE test_stats_temp;
 -- results of the first.
 CHECKPOINT;
 CHECKPOINT;
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_checkpointer;
  ?column? 
 ----------
  t
@@ -884,6 +884,21 @@ SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 (1 row)
 
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index b4d6753c71..c8c24abea8 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -387,8 +387,8 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
 SELECT pg_stat_force_next_flush();
 SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database());
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
@@ -402,7 +402,7 @@ DROP TABLE test_stats_temp;
 CHECKPOINT;
 CHECKPOINT;
 
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_checkpointer;
 SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
 
 -- Test pg_stat_get_backend_idset() and some allied functions.
@@ -440,6 +440,12 @@ SELECT pg_stat_reset_shared('bgwriter');
 SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
 
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
-- 
2.34.1

From 8280223b2b8fde888dd8540328336421bbf6138c Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Fri, 2 Dec 2022 04:58:46 +0000
Subject: [PATCH v4] Introduce a new view for checkpointer related stats

pg_stat_bgwriter view currently reports checkpointer stats as well.
It is that way because historically checkpointer was part of
bgwriter until the commits 806a2ae and bf405ba, that went into
PG 9.2, separated them out.

It is time for us to separate checkpointer stats to its own view
called pg_stat_checkpointer.

Bump catalog version.
---
 doc/src/sgml/monitoring.sgml                  | 110 +++++++++++++-----
 src/backend/catalog/system_views.sql          |  18 +--
 .../utils/activity/pgstat_checkpointer.c      |   1 +
 src/backend/utils/adt/pgstatfuncs.c           |  19 +--
 src/include/catalog/pg_proc.dat               |  22 ++--
 src/include/pgstat.h                          |   1 +
 src/test/recovery/t/029_stats_restart.pl      |   6 +-
 src/test/regress/expected/rules.out           |  17 +--
 src/test/regress/expected/stats.out           |  21 +++-
 src/test/regress/sql/stats.sql                |  12 +-
 10 files changed, 156 insertions(+), 71 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 11a8ebe5ec..1279b47d27 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -448,6 +448,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
      </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
+      <entry>One row only, showing statistics about the
+       checkpointer process's activity. See
+       <link linkend="monitoring-pg-stat-checkpointer-view">
+       <structname>pg_stat_checkpointer</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_wal</structname><indexterm><primary>pg_stat_wal</primary></indexterm></entry>
       <entry>One row only, showing statistics about WAL activity. See
@@ -3633,7 +3642,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
 
   <para>
    The <structname>pg_stat_bgwriter</structname> view will always have a
-   single row, containing global data for the cluster.
+   single row, containing data about the bgwriter of the cluster.
   </para>
 
   <table id="pg-stat-bgwriter-view" xreflabel="pg_stat_bgwriter">
@@ -3653,97 +3662,138 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
     <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_timed</structfield> <type>bigint</type>
+       <structfield>buffers_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of scheduled checkpoints that have been performed
+       Number of buffers written by the background writer
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_req</structfield> <type>bigint</type>
+       <structfield>maxwritten_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of requested checkpoints that have been performed
+       Number of times the background writer stopped a cleaning
+       scan because it had written too many buffers
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
+       <structfield>buffers_alloc</structfield> <type>bigint</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are written to disk, in milliseconds
+       Number of buffers allocated
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are synchronized to disk, in
-       milliseconds
+       Time at which these statistics were last reset
       </para></entry>
      </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
+
+ <sect2 id="monitoring-pg-stat-checkpointer-view">
+  <title><structname>pg_stat_checkpointer</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_checkpointer</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_checkpointer</structname> view will always have a
+   single row, containing data about the checkpointer process of the cluster.
+  </para>
 
+  <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
+   <title><structname>pg_stat_checkpointer</structname> View</title>
+   <tgroup cols="1">
+    <thead>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
+       Column Type
       </para>
       <para>
-       Number of buffers written during checkpoints
+       Description
       </para></entry>
      </row>
+    </thead>
 
+    <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_clean</structfield> <type>bigint</type>
+       <structfield>timed_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written by the background writer
+       Number of scheduled checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>maxwritten_clean</structfield> <type>bigint</type>
+       <structfield>requested_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of times the background writer stopped a cleaning
-       scan because it had written too many buffers
+       Number of requested checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend</structfield> <type>bigint</type>
+       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of buffers written directly by a backend
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are written to disk, in milliseconds
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
+       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of times a backend had to execute its own
-       <function>fsync</function> call (normally the background writer handles those
-       even when the backend does its own write)
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are synchronized to disk, in
+       milliseconds
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_alloc</structfield> <type>bigint</type>
+       <structfield>buffers_written_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers allocated
+       Number of buffers written during checkpoints
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_written_backend</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written directly by a backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_fsync_backend</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a backend had to execute its own
+       <function>fsync</function> call (normally the checkpointer handles those
+       even when the backend does its own write)
       </para></entry>
      </row>
 
@@ -5393,8 +5443,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         Resets some cluster-wide statistics counters to zero, depending on the
         argument.  The argument can be <literal>bgwriter</literal> to reset
         all the counters shown in
-        the <structname>pg_stat_bgwriter</structname>
-        view, <literal>archiver</literal> to reset all the counters shown in
+        the <structname>pg_stat_bgwriter</structname> view,
+        <literal>checkpointer</literal> to reset all the counters shown in
+        the <structname>pg_stat_checkpointer</structname> view,
+        <literal>archiver</literal> to reset all the counters shown in
         the <structname>pg_stat_archiver</structname> view,
         <literal>wal</literal> to reset all the counters shown in the
         <structname>pg_stat_wal</structname> view or
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 2d8104b090..89e40db1c1 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1105,18 +1105,22 @@ CREATE VIEW pg_stat_archiver AS
 
 CREATE VIEW pg_stat_bgwriter AS
     SELECT
-        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-        pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-        pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-        pg_stat_get_buf_written_backend() AS buffers_backend,
-        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_checkpointer AS
+    SELECT
+        pg_stat_get_timed_checkpoints() AS timed_checkpoints,
+        pg_stat_get_requested_checkpoints() AS requested_checkpoints,
+        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+        pg_stat_get_buf_written_checkpoints() AS buffers_written_checkpoints,
+        pg_stat_get_buf_written_backend() AS buffers_written_backend,
+        pg_stat_get_buf_fsync_backend() AS buffers_fsync_backend,
+        pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
+
 CREATE VIEW pg_stat_wal AS
     SELECT
         w.wal_records,
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index af8d513e7b..2757a10b7e 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -89,6 +89,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
 									&stats_shmem->stats,
 									sizeof(stats_shmem->stats),
 									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
 	LWLockRelease(&stats_shmem->lock);
 }
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index ae3365d917..38a2595cdd 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1662,19 +1662,19 @@ pg_stat_get_db_sessions_killed(PG_FUNCTION_ARGS)
 }
 
 Datum
-pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_timed_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_requested_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_buf_written_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
 }
@@ -1707,6 +1707,12 @@ pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
 					 pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
 }
 
+Datum
+pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
+}
+
 Datum
 pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 {
@@ -2082,14 +2088,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 	if (strcmp(target, "archiver") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
 	else if (strcmp(target, "bgwriter") == 0)
-	{
-		/*
-		 * Historically checkpointer was part of bgwriter, continue to reset
-		 * both for now.
-		 */
 		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+	else if (strcmp(target, "checkpointer") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
-	}
 	else if (strcmp(target, "recovery_prefetch") == 0)
 		XLogPrefetchResetStats();
 	else if (strcmp(target, "wal") == 0)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index f9301b2627..1b24969a01 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5628,20 +5628,24 @@
   proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}',
   prosrc => 'pg_stat_get_archiver' },
 { oid => '2769',
-  descr => 'statistics: number of timed checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_timed_checkpoints', provolatile => 's',
+  descr => 'statistics: number of timed checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_timed_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_timed_checkpoints' },
+  prosrc => 'pg_stat_get_timed_checkpoints' },
 { oid => '2770',
-  descr => 'statistics: number of backend requested checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_requested_checkpoints', provolatile => 's',
+  descr => 'statistics: number of backend requested checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_requested_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_requested_checkpoints' },
+  prosrc => 'pg_stat_get_requested_checkpoints' },
 { oid => '2771',
-  descr => 'statistics: number of buffers written by the bgwriter during checkpoints',
-  proname => 'pg_stat_get_bgwriter_buf_written_checkpoints', provolatile => 's',
+  descr => 'statistics: number of buffers written by the checkpointer',
+  proname => 'pg_stat_get_buf_written_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_buf_written_checkpoints' },
+  prosrc => 'pg_stat_get_buf_written_checkpoints' },
+{ oid => '8206', descr => 'statistics: last reset for the checkpointer',
+  proname => 'pg_stat_get_checkpointer_stat_reset_time', provolatile => 's',
+  proparallel => 'r', prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_stat_get_checkpointer_stat_reset_time' },
 { oid => '2772',
   descr => 'statistics: number of buffers written by the bgwriter for cleaning dirty buffers',
   proname => 'pg_stat_get_bgwriter_buf_written_clean', provolatile => 's',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9e2ce6f011..e23d80bba8 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -274,6 +274,7 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter buf_written_checkpoints;
 	PgStat_Counter buf_written_backend;
 	PgStat_Counter buf_fsync_backend;
+	TimestampTz stat_reset_timestamp;
 } PgStat_CheckpointerStats;
 
 typedef struct PgStat_StatDBEntry
diff --git a/src/test/recovery/t/029_stats_restart.pl b/src/test/recovery/t/029_stats_restart.pl
index 1bf7b568cc..25ae0a36e6 100644
--- a/src/test/recovery/t/029_stats_restart.pl
+++ b/src/test/recovery/t/029_stats_restart.pl
@@ -173,7 +173,7 @@ is($wal_start->{reset}, $wal_restart->{reset},
 
 ## Check that checkpoint stats are reset, WAL stats aren't affected
 
-$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('bgwriter')");
+$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('checkpointer')");
 
 $sect = "post ckpt reset";
 my $ckpt_reset     = checkpoint_stats();
@@ -323,9 +323,9 @@ sub checkpoint_stats
 	my %results;
 
 	$results{count} = $node->safe_psql($connect_db,
-		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter");
+		"SELECT timed_checkpoints + requested_checkpoints FROM pg_stat_checkpointer");
 	$results{reset} = $node->safe_psql($connect_db,
-		"SELECT stats_reset FROM pg_stat_bgwriter");
+		"SELECT stats_reset FROM pg_stat_checkpointer");
 
 	return \%results;
 }
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 37c1c86473..2cf97dcee1 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1814,17 +1814,18 @@ pg_stat_archiver| SELECT s.archived_count,
     s.last_failed_time,
     s.stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
-pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
-    pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
+pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-    pg_stat_get_buf_written_backend() AS buffers_backend,
-    pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+pg_stat_checkpointer| SELECT pg_stat_get_timed_checkpoints() AS timed_checkpoints,
+    pg_stat_get_requested_checkpoints() AS requested_checkpoints,
+    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+    pg_stat_get_buf_written_checkpoints() AS buffers_written_checkpoints,
+    pg_stat_get_buf_written_backend() AS buffers_written_backend,
+    pg_stat_get_buf_fsync_backend() AS buffers_fsync_backend,
+    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT d.oid AS datid,
     d.datname,
         CASE
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 1d84407a03..85aaebe7b6 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -782,8 +782,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
  t
 (1 row)
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT requested_checkpoints AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
 CREATE TEMP TABLE test_stats_temp AS SELECT 17;
@@ -793,7 +793,7 @@ DROP TABLE test_stats_temp;
 -- results of the first.
 CHECKPOINT;
 CHECKPOINT;
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT requested_checkpoints > :rqst_ckpts_before FROM pg_stat_checkpointer;
  ?column? 
 ----------
  t
@@ -884,6 +884,21 @@ SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 (1 row)
 
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index b4d6753c71..e867bc15e3 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -387,8 +387,8 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
 SELECT pg_stat_force_next_flush();
 SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database());
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT requested_checkpoints AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
@@ -402,7 +402,7 @@ DROP TABLE test_stats_temp;
 CHECKPOINT;
 CHECKPOINT;
 
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT requested_checkpoints > :rqst_ckpts_before FROM pg_stat_checkpointer;
 SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
 
 -- Test pg_stat_get_backend_idset() and some allied functions.
@@ -440,6 +440,12 @@ SELECT pg_stat_reset_shared('bgwriter');
 SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
 
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
-- 
2.34.1

From e705916c40649d13a66299159cc992d0572960f5 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Fri, 20 Jan 2023 14:20:03 +0000
Subject: [PATCH v5] Introduce a new view for checkpointer related stats

pg_stat_bgwriter view currently reports checkpointer stats as well.
It is that way because historically checkpointer was part of
bgwriter until the commits 806a2ae and bf405ba, that went into
PG 9.2, separated them out.

It is time for us to separate checkpointer stats to its own view
called pg_stat_checkpointer.

Bump catalog version.
---
 doc/src/sgml/monitoring.sgml                  | 110 +++++++++++++-----
 src/backend/catalog/system_views.sql          |  18 +--
 .../utils/activity/pgstat_checkpointer.c      |   1 +
 src/backend/utils/adt/pgstatfuncs.c           |  19 +--
 src/include/catalog/pg_proc.dat               |  22 ++--
 src/include/pgstat.h                          |   1 +
 src/test/recovery/t/029_stats_restart.pl      |   6 +-
 src/test/regress/expected/rules.out           |  17 +--
 src/test/regress/expected/stats.out           |  21 +++-
 src/test/regress/sql/stats.sql                |  12 +-
 10 files changed, 156 insertions(+), 71 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index e3a783abd0..54166d88fc 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -494,6 +494,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
+      <entry>One row only, showing statistics about the
+       checkpointer process's activity. See
+       <link linkend="monitoring-pg-stat-checkpointer-view">
+       <structname>pg_stat_checkpointer</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_wal</structname><indexterm><primary>pg_stat_wal</primary></indexterm></entry>
       <entry>One row only, showing statistics about WAL activity. See
@@ -3671,7 +3680,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
 
   <para>
    The <structname>pg_stat_bgwriter</structname> view will always have a
-   single row, containing global data for the cluster.
+   single row, containing data about the bgwriter of the cluster.
   </para>
 
   <table id="pg-stat-bgwriter-view" xreflabel="pg_stat_bgwriter">
@@ -3691,97 +3700,138 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
     <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_timed</structfield> <type>bigint</type>
+       <structfield>buffers_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of scheduled checkpoints that have been performed
+       Number of buffers written by the background writer
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_req</structfield> <type>bigint</type>
+       <structfield>maxwritten_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of requested checkpoints that have been performed
+       Number of times the background writer stopped a cleaning
+       scan because it had written too many buffers
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
+       <structfield>buffers_alloc</structfield> <type>bigint</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are written to disk, in milliseconds
+       Number of buffers allocated
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are synchronized to disk, in
-       milliseconds
+       Time at which these statistics were last reset
       </para></entry>
      </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
+
+ <sect2 id="monitoring-pg-stat-checkpointer-view">
+  <title><structname>pg_stat_checkpointer</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_checkpointer</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_checkpointer</structname> view will always have a
+   single row, containing data about the checkpointer process of the cluster.
+  </para>
 
+  <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
+   <title><structname>pg_stat_checkpointer</structname> View</title>
+   <tgroup cols="1">
+    <thead>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
+       Column Type
       </para>
       <para>
-       Number of buffers written during checkpoints
+       Description
       </para></entry>
      </row>
+    </thead>
 
+    <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_clean</structfield> <type>bigint</type>
+       <structfield>timed_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written by the background writer
+       Number of scheduled checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>maxwritten_clean</structfield> <type>bigint</type>
+       <structfield>requested_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of times the background writer stopped a cleaning
-       scan because it had written too many buffers
+       Number of requested checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend</structfield> <type>bigint</type>
+       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of buffers written directly by a backend
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are written to disk, in milliseconds
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
+       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of times a backend had to execute its own
-       <function>fsync</function> call (normally the background writer handles those
-       even when the backend does its own write)
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are synchronized to disk, in
+       milliseconds
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_alloc</structfield> <type>bigint</type>
+       <structfield>buffers_written_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers allocated
+       Number of buffers written during checkpoints
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_written_backend</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written directly by a backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_fsync_backend</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a backend had to execute its own
+       <function>fsync</function> call (normally the checkpointer handles those
+       even when the backend does its own write)
       </para></entry>
      </row>
 
@@ -5431,8 +5481,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         Resets some cluster-wide statistics counters to zero, depending on the
         argument.  The argument can be <literal>bgwriter</literal> to reset
         all the counters shown in
-        the <structname>pg_stat_bgwriter</structname>
-        view, <literal>archiver</literal> to reset all the counters shown in
+        the <structname>pg_stat_bgwriter</structname> view,
+        <literal>checkpointer</literal> to reset all the counters shown in
+        the <structname>pg_stat_checkpointer</structname> view,
+        <literal>archiver</literal> to reset all the counters shown in
         the <structname>pg_stat_archiver</structname> view,
         <literal>wal</literal> to reset all the counters shown in the
         <structname>pg_stat_wal</structname> view or
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 8608e3fa5b..1ac72031fc 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1105,18 +1105,22 @@ CREATE VIEW pg_stat_archiver AS
 
 CREATE VIEW pg_stat_bgwriter AS
     SELECT
-        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-        pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-        pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-        pg_stat_get_buf_written_backend() AS buffers_backend,
-        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_checkpointer AS
+    SELECT
+        pg_stat_get_timed_checkpoints() AS timed_checkpoints,
+        pg_stat_get_requested_checkpoints() AS requested_checkpoints,
+        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+        pg_stat_get_buf_written_checkpoints() AS buffers_written_checkpoints,
+        pg_stat_get_buf_written_backend() AS buffers_written_backend,
+        pg_stat_get_buf_fsync_backend() AS buffers_fsync_backend,
+        pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
+
 CREATE VIEW pg_stat_wal AS
     SELECT
         w.wal_records,
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index 3e9ab45103..d9942b64d4 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -89,6 +89,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
 									&stats_shmem->stats,
 									sizeof(stats_shmem->stats),
 									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
 	LWLockRelease(&stats_shmem->lock);
 }
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 6737493402..271f19688b 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1176,19 +1176,19 @@ PG_STAT_GET_DBENTRY_FLOAT8(idle_in_transaction_time)
 PG_STAT_GET_DBENTRY_FLOAT8(session_time)
 
 Datum
-pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_timed_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_requested_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_buf_written_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
 }
@@ -1221,6 +1221,12 @@ pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
 					 pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
 }
 
+Datum
+pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
+}
+
 Datum
 pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 {
@@ -1596,14 +1602,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 	if (strcmp(target, "archiver") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
 	else if (strcmp(target, "bgwriter") == 0)
-	{
-		/*
-		 * Historically checkpointer was part of bgwriter, continue to reset
-		 * both for now.
-		 */
 		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+	else if (strcmp(target, "checkpointer") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
-	}
 	else if (strcmp(target, "recovery_prefetch") == 0)
 		XLogPrefetchResetStats();
 	else if (strcmp(target, "wal") == 0)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 86eb8e8c58..decd98c327 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5639,20 +5639,24 @@
   proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}',
   prosrc => 'pg_stat_get_archiver' },
 { oid => '2769',
-  descr => 'statistics: number of timed checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_timed_checkpoints', provolatile => 's',
+  descr => 'statistics: number of timed checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_timed_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_timed_checkpoints' },
+  prosrc => 'pg_stat_get_timed_checkpoints' },
 { oid => '2770',
-  descr => 'statistics: number of backend requested checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_requested_checkpoints', provolatile => 's',
+  descr => 'statistics: number of backend requested checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_requested_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_requested_checkpoints' },
+  prosrc => 'pg_stat_get_requested_checkpoints' },
 { oid => '2771',
-  descr => 'statistics: number of buffers written by the bgwriter during checkpoints',
-  proname => 'pg_stat_get_bgwriter_buf_written_checkpoints', provolatile => 's',
+  descr => 'statistics: number of buffers written by the checkpointer',
+  proname => 'pg_stat_get_buf_written_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_buf_written_checkpoints' },
+  prosrc => 'pg_stat_get_buf_written_checkpoints' },
+{ oid => '8206', descr => 'statistics: last reset for the checkpointer',
+  proname => 'pg_stat_get_checkpointer_stat_reset_time', provolatile => 's',
+  proparallel => 'r', prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_stat_get_checkpointer_stat_reset_time' },
 { oid => '2772',
   descr => 'statistics: number of buffers written by the bgwriter for cleaning dirty buffers',
   proname => 'pg_stat_get_bgwriter_buf_written_clean', provolatile => 's',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5e3326a3b9..b8d8a3710c 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -274,6 +274,7 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter buf_written_checkpoints;
 	PgStat_Counter buf_written_backend;
 	PgStat_Counter buf_fsync_backend;
+	TimestampTz stat_reset_timestamp;
 } PgStat_CheckpointerStats;
 
 typedef struct PgStat_StatDBEntry
diff --git a/src/test/recovery/t/029_stats_restart.pl b/src/test/recovery/t/029_stats_restart.pl
index 83d6647d32..463f29101e 100644
--- a/src/test/recovery/t/029_stats_restart.pl
+++ b/src/test/recovery/t/029_stats_restart.pl
@@ -173,7 +173,7 @@ is($wal_start->{reset}, $wal_restart->{reset},
 
 ## Check that checkpoint stats are reset, WAL stats aren't affected
 
-$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('bgwriter')");
+$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('checkpointer')");
 
 $sect = "post ckpt reset";
 my $ckpt_reset     = checkpoint_stats();
@@ -323,9 +323,9 @@ sub checkpoint_stats
 	my %results;
 
 	$results{count} = $node->safe_psql($connect_db,
-		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter");
+		"SELECT timed_checkpoints + requested_checkpoints FROM pg_stat_checkpointer");
 	$results{reset} = $node->safe_psql($connect_db,
-		"SELECT stats_reset FROM pg_stat_bgwriter");
+		"SELECT stats_reset FROM pg_stat_checkpointer");
 
 	return \%results;
 }
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index e7a2f5856a..1215e0f881 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1814,17 +1814,18 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
-pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
-    pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
+pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-    pg_stat_get_buf_written_backend() AS buffers_backend,
-    pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+pg_stat_checkpointer| SELECT pg_stat_get_timed_checkpoints() AS timed_checkpoints,
+    pg_stat_get_requested_checkpoints() AS requested_checkpoints,
+    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+    pg_stat_get_buf_written_checkpoints() AS buffers_written_checkpoints,
+    pg_stat_get_buf_written_backend() AS buffers_written_backend,
+    pg_stat_get_buf_fsync_backend() AS buffers_fsync_backend,
+    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT oid AS datid,
     datname,
         CASE
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 1d84407a03..85aaebe7b6 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -782,8 +782,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
  t
 (1 row)
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT requested_checkpoints AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
 CREATE TEMP TABLE test_stats_temp AS SELECT 17;
@@ -793,7 +793,7 @@ DROP TABLE test_stats_temp;
 -- results of the first.
 CHECKPOINT;
 CHECKPOINT;
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT requested_checkpoints > :rqst_ckpts_before FROM pg_stat_checkpointer;
  ?column? 
 ----------
  t
@@ -884,6 +884,21 @@ SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 (1 row)
 
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index b4d6753c71..e867bc15e3 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -387,8 +387,8 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
 SELECT pg_stat_force_next_flush();
 SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database());
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT requested_checkpoints AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
@@ -402,7 +402,7 @@ DROP TABLE test_stats_temp;
 CHECKPOINT;
 CHECKPOINT;
 
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT requested_checkpoints > :rqst_ckpts_before FROM pg_stat_checkpointer;
 SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
 
 -- Test pg_stat_get_backend_idset() and some allied functions.
@@ -440,6 +440,12 @@ SELECT pg_stat_reset_shared('bgwriter');
 SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
 
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
-- 
2.34.1

From 87829fec1f51a2ed764c6e48825caf13ef4b2725 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Thu, 9 Feb 2023 06:25:35 +0000
Subject: [PATCH v6] Introduce a new view for checkpointer related stats

pg_stat_bgwriter view currently reports checkpointer stats as well.
It is that way because historically checkpointer was part of
bgwriter until the commits 806a2ae and bf405ba, that went into
PG 9.2, separated them out.

It is time for us to separate checkpointer stats to its own view
called pg_stat_checkpointer.

Bump catalog version.
---
 doc/src/sgml/monitoring.sgml                  | 110 +++++++++++++-----
 src/backend/catalog/system_views.sql          |  18 +--
 .../utils/activity/pgstat_checkpointer.c      |   1 +
 src/backend/utils/adt/pgstatfuncs.c           |  19 +--
 src/include/catalog/pg_proc.dat               |  22 ++--
 src/include/pgstat.h                          |   1 +
 src/test/recovery/t/029_stats_restart.pl      |   6 +-
 src/test/regress/expected/rules.out           |  17 +--
 src/test/regress/expected/stats.out           |  21 +++-
 src/test/regress/sql/stats.sql                |  12 +-
 10 files changed, 156 insertions(+), 71 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index b246ddc634..f53f5769fc 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -494,6 +494,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
+      <entry>One row only, showing statistics about the
+       checkpointer process's activity. See
+       <link linkend="monitoring-pg-stat-checkpointer-view">
+       <structname>pg_stat_checkpointer</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_wal</structname><indexterm><primary>pg_stat_wal</primary></indexterm></entry>
       <entry>One row only, showing statistics about WAL activity. See
@@ -3681,7 +3690,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
 
   <para>
    The <structname>pg_stat_bgwriter</structname> view will always have a
-   single row, containing global data for the cluster.
+   single row, containing data about the bgwriter of the cluster.
   </para>
 
   <table id="pg-stat-bgwriter-view" xreflabel="pg_stat_bgwriter">
@@ -3701,97 +3710,138 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
     <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_timed</structfield> <type>bigint</type>
+       <structfield>buffers_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of scheduled checkpoints that have been performed
+       Number of buffers written by the background writer
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_req</structfield> <type>bigint</type>
+       <structfield>maxwritten_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of requested checkpoints that have been performed
+       Number of times the background writer stopped a cleaning
+       scan because it had written too many buffers
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
+       <structfield>buffers_alloc</structfield> <type>bigint</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are written to disk, in milliseconds
+       Number of buffers allocated
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are synchronized to disk, in
-       milliseconds
+       Time at which these statistics were last reset
       </para></entry>
      </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
+
+ <sect2 id="monitoring-pg-stat-checkpointer-view">
+  <title><structname>pg_stat_checkpointer</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_checkpointer</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_checkpointer</structname> view will always have a
+   single row, containing data about the checkpointer process of the cluster.
+  </para>
 
+  <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
+   <title><structname>pg_stat_checkpointer</structname> View</title>
+   <tgroup cols="1">
+    <thead>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
+       Column Type
       </para>
       <para>
-       Number of buffers written during checkpoints
+       Description
       </para></entry>
      </row>
+    </thead>
 
+    <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_clean</structfield> <type>bigint</type>
+       <structfield>timed_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written by the background writer
+       Number of scheduled checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>maxwritten_clean</structfield> <type>bigint</type>
+       <structfield>requested_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of times the background writer stopped a cleaning
-       scan because it had written too many buffers
+       Number of requested checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend</structfield> <type>bigint</type>
+       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of buffers written directly by a backend
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are written to disk, in milliseconds
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
+       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of times a backend had to execute its own
-       <function>fsync</function> call (normally the background writer handles those
-       even when the backend does its own write)
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are synchronized to disk, in
+       milliseconds
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_alloc</structfield> <type>bigint</type>
+       <structfield>buffers_written_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers allocated
+       Number of buffers written during checkpoints
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_written_backend</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written directly by a backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_fsync_backend</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of times a backend had to execute its own
+       <function>fsync</function> call (normally the checkpointer handles those
+       even when the backend does its own write)
       </para></entry>
      </row>
 
@@ -5441,8 +5491,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         Resets some cluster-wide statistics counters to zero, depending on the
         argument.  The argument can be <literal>bgwriter</literal> to reset
         all the counters shown in
-        the <structname>pg_stat_bgwriter</structname>
-        view, <literal>archiver</literal> to reset all the counters shown in
+        the <structname>pg_stat_bgwriter</structname> view,
+        <literal>checkpointer</literal> to reset all the counters shown in
+        the <structname>pg_stat_checkpointer</structname> view,
+        <literal>archiver</literal> to reset all the counters shown in
         the <structname>pg_stat_archiver</structname> view,
         <literal>io</literal> to reset all the counters shown in the
         <structname>pg_stat_io</structname> view,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 8608e3fa5b..1ac72031fc 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1105,18 +1105,22 @@ CREATE VIEW pg_stat_archiver AS
 
 CREATE VIEW pg_stat_bgwriter AS
     SELECT
-        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-        pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-        pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-        pg_stat_get_buf_written_backend() AS buffers_backend,
-        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_checkpointer AS
+    SELECT
+        pg_stat_get_timed_checkpoints() AS timed_checkpoints,
+        pg_stat_get_requested_checkpoints() AS requested_checkpoints,
+        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+        pg_stat_get_buf_written_checkpoints() AS buffers_written_checkpoints,
+        pg_stat_get_buf_written_backend() AS buffers_written_backend,
+        pg_stat_get_buf_fsync_backend() AS buffers_fsync_backend,
+        pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
+
 CREATE VIEW pg_stat_wal AS
     SELECT
         w.wal_records,
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index 26dec112f6..f949095841 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -94,6 +94,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
 									&stats_shmem->stats,
 									sizeof(stats_shmem->stats),
 									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
 	LWLockRelease(&stats_shmem->lock);
 }
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 924698e6ae..b8a208a5b5 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1176,19 +1176,19 @@ PG_STAT_GET_DBENTRY_FLOAT8(idle_in_transaction_time)
 PG_STAT_GET_DBENTRY_FLOAT8(session_time)
 
 Datum
-pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_timed_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_requested_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_buf_written_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
 }
@@ -1221,6 +1221,12 @@ pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
 					 pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
 }
 
+Datum
+pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
+}
+
 Datum
 pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 {
@@ -1601,14 +1607,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 	if (strcmp(target, "archiver") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
 	else if (strcmp(target, "bgwriter") == 0)
-	{
-		/*
-		 * Historically checkpointer was part of bgwriter, continue to reset
-		 * both for now.
-		 */
 		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+	else if (strcmp(target, "checkpointer") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
-	}
 	else if (strcmp(target, "io") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_IO);
 	else if (strcmp(target, "recovery_prefetch") == 0)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index c0f2a8a77c..97a8c823fc 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5666,20 +5666,24 @@
   proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}',
   prosrc => 'pg_stat_get_archiver' },
 { oid => '2769',
-  descr => 'statistics: number of timed checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_timed_checkpoints', provolatile => 's',
+  descr => 'statistics: number of timed checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_timed_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_timed_checkpoints' },
+  prosrc => 'pg_stat_get_timed_checkpoints' },
 { oid => '2770',
-  descr => 'statistics: number of backend requested checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_requested_checkpoints', provolatile => 's',
+  descr => 'statistics: number of backend requested checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_requested_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_requested_checkpoints' },
+  prosrc => 'pg_stat_get_requested_checkpoints' },
 { oid => '2771',
-  descr => 'statistics: number of buffers written by the bgwriter during checkpoints',
-  proname => 'pg_stat_get_bgwriter_buf_written_checkpoints', provolatile => 's',
+  descr => 'statistics: number of buffers written by the checkpointer',
+  proname => 'pg_stat_get_buf_written_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_buf_written_checkpoints' },
+  prosrc => 'pg_stat_get_buf_written_checkpoints' },
+{ oid => '8206', descr => 'statistics: last reset for the checkpointer',
+  proname => 'pg_stat_get_checkpointer_stat_reset_time', provolatile => 's',
+  proparallel => 'r', prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_stat_get_checkpointer_stat_reset_time' },
 { oid => '2772',
   descr => 'statistics: number of buffers written by the bgwriter for cleaning dirty buffers',
   proname => 'pg_stat_get_bgwriter_buf_written_clean', provolatile => 's',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index db9675884f..98418b7610 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -275,6 +275,7 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter buf_written_checkpoints;
 	PgStat_Counter buf_written_backend;
 	PgStat_Counter buf_fsync_backend;
+	TimestampTz stat_reset_timestamp;
 } PgStat_CheckpointerStats;
 
 
diff --git a/src/test/recovery/t/029_stats_restart.pl b/src/test/recovery/t/029_stats_restart.pl
index 83d6647d32..463f29101e 100644
--- a/src/test/recovery/t/029_stats_restart.pl
+++ b/src/test/recovery/t/029_stats_restart.pl
@@ -173,7 +173,7 @@ is($wal_start->{reset}, $wal_restart->{reset},
 
 ## Check that checkpoint stats are reset, WAL stats aren't affected
 
-$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('bgwriter')");
+$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('checkpointer')");
 
 $sect = "post ckpt reset";
 my $ckpt_reset     = checkpoint_stats();
@@ -323,9 +323,9 @@ sub checkpoint_stats
 	my %results;
 
 	$results{count} = $node->safe_psql($connect_db,
-		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter");
+		"SELECT timed_checkpoints + requested_checkpoints FROM pg_stat_checkpointer");
 	$results{reset} = $node->safe_psql($connect_db,
-		"SELECT stats_reset FROM pg_stat_bgwriter");
+		"SELECT stats_reset FROM pg_stat_checkpointer");
 
 	return \%results;
 }
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index e7a2f5856a..1215e0f881 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1814,17 +1814,18 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
-pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
-    pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
+pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-    pg_stat_get_buf_written_backend() AS buffers_backend,
-    pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+pg_stat_checkpointer| SELECT pg_stat_get_timed_checkpoints() AS timed_checkpoints,
+    pg_stat_get_requested_checkpoints() AS requested_checkpoints,
+    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+    pg_stat_get_buf_written_checkpoints() AS buffers_written_checkpoints,
+    pg_stat_get_buf_written_backend() AS buffers_written_backend,
+    pg_stat_get_buf_fsync_backend() AS buffers_fsync_backend,
+    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT oid AS datid,
     datname,
         CASE
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 1d84407a03..85aaebe7b6 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -782,8 +782,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
  t
 (1 row)
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT requested_checkpoints AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
 CREATE TEMP TABLE test_stats_temp AS SELECT 17;
@@ -793,7 +793,7 @@ DROP TABLE test_stats_temp;
 -- results of the first.
 CHECKPOINT;
 CHECKPOINT;
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT requested_checkpoints > :rqst_ckpts_before FROM pg_stat_checkpointer;
  ?column? 
 ----------
  t
@@ -884,6 +884,21 @@ SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 (1 row)
 
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index b4d6753c71..e867bc15e3 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -387,8 +387,8 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
 SELECT pg_stat_force_next_flush();
 SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database());
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT requested_checkpoints AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
@@ -402,7 +402,7 @@ DROP TABLE test_stats_temp;
 CHECKPOINT;
 CHECKPOINT;
 
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT requested_checkpoints > :rqst_ckpts_before FROM pg_stat_checkpointer;
 SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
 
 -- Test pg_stat_get_backend_idset() and some allied functions.
@@ -440,6 +440,12 @@ SELECT pg_stat_reset_shared('bgwriter');
 SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
 
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
-- 
2.34.1

From edb5ee994b179034273edd42c139aa57c9106922 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Fri, 10 Feb 2023 11:45:14 +0000
Subject: [PATCH v7] Drop buffers_backend column from pg_stat_bgwriter view

---
 doc/src/sgml/monitoring.sgml                  |  9 ---------
 src/backend/catalog/system_views.sql          |  1 -
 src/backend/postmaster/checkpointer.c         | 20 +++++--------------
 .../utils/activity/pgstat_checkpointer.c      |  2 --
 src/backend/utils/adt/pgstatfuncs.c           |  6 ------
 src/include/catalog/pg_proc.dat               |  4 ----
 src/include/pgstat.h                          |  1 -
 src/test/regress/expected/rules.out           |  1 -
 8 files changed, 5 insertions(+), 39 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index b246ddc634..380085eedd 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3766,15 +3766,6 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </para></entry>
      </row>
 
-     <row>
-      <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend</structfield> <type>bigint</type>
-      </para>
-      <para>
-       Number of buffers written directly by a backend
-      </para></entry>
-     </row>
-
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 8608e3fa5b..2b1b2bf7c3 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1112,7 +1112,6 @@ CREATE VIEW pg_stat_bgwriter AS
         pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-        pg_stat_get_buf_written_backend() AS buffers_backend,
         pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index aaad5c5228..baadd08044 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -91,17 +91,15 @@
  * requesting backends since the last checkpoint start.  The flags are
  * chosen so that OR'ing is the correct way to combine multiple requests.
  *
- * num_backend_writes is used to count the number of buffer writes performed
- * by user backend processes.  This counter should be wide enough that it
- * can't overflow during a single processing cycle.  num_backend_fsync
- * counts the subset of those writes that also had to do their own fsync,
- * because the checkpointer failed to absorb their request.
+ * num_backend_fsync counts the subset of buffer writes performed by user
+ * backend processes that also had to do their own fsync, because the
+ * checkpointer failed to absorb their request.
  *
  * The requests array holds fsync requests sent by backends and not yet
  * absorbed by the checkpointer.
  *
- * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
- * the requests fields are protected by CheckpointerCommLock.
+ * Unlike the checkpoint fields, num_backend_fsync and the requests fields are
+ * protected by CheckpointerCommLock.
  *----------
  */
 typedef struct
@@ -125,7 +123,6 @@ typedef struct
 	ConditionVariable start_cv; /* signaled when ckpt_started advances */
 	ConditionVariable done_cv;	/* signaled when ckpt_done advances */
 
-	uint32		num_backend_writes; /* counts user backend buffer writes */
 	uint32		num_backend_fsync;	/* counts user backend fsync calls */
 
 	int			num_requests;	/* current # of requests */
@@ -1096,10 +1093,6 @@ ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
 
 	LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
 
-	/* Count all backend writes regardless of if they fit in the queue */
-	if (!AmBackgroundWriterProcess())
-		CheckpointerShmem->num_backend_writes++;
-
 	/*
 	 * If the checkpointer isn't running or the request queue is full, the
 	 * backend will have to perform its own fsync request.  But before forcing
@@ -1272,12 +1265,9 @@ AbsorbSyncRequests(void)
 	LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
 
 	/* Transfer stats counts into pending pgstats message */
-	PendingCheckpointerStats.buf_written_backend
-		+= CheckpointerShmem->num_backend_writes;
 	PendingCheckpointerStats.buf_fsync_backend
 		+= CheckpointerShmem->num_backend_fsync;
 
-	CheckpointerShmem->num_backend_writes = 0;
 	CheckpointerShmem->num_backend_fsync = 0;
 
 	/*
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index 26dec112f6..a048205d6e 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -52,7 +52,6 @@ pgstat_report_checkpointer(void)
 	CHECKPOINTER_ACC(checkpoint_write_time);
 	CHECKPOINTER_ACC(checkpoint_sync_time);
 	CHECKPOINTER_ACC(buf_written_checkpoints);
-	CHECKPOINTER_ACC(buf_written_backend);
 	CHECKPOINTER_ACC(buf_fsync_backend);
 #undef CHECKPOINTER_ACC
 
@@ -120,7 +119,6 @@ pgstat_checkpointer_snapshot_cb(void)
 	CHECKPOINTER_COMP(checkpoint_write_time);
 	CHECKPOINTER_COMP(checkpoint_sync_time);
 	CHECKPOINTER_COMP(buf_written_checkpoints);
-	CHECKPOINTER_COMP(buf_written_backend);
 	CHECKPOINTER_COMP(buf_fsync_backend);
 #undef CHECKPOINTER_COMP
 }
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 924698e6ae..ce16884f1b 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1227,12 +1227,6 @@ pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_bgwriter()->stat_reset_timestamp);
 }
 
-Datum
-pg_stat_get_buf_written_backend(PG_FUNCTION_ARGS)
-{
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_backend);
-}
-
 Datum
 pg_stat_get_buf_fsync_backend(PG_FUNCTION_ARGS)
 {
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index c0f2a8a77c..3188d9ee1f 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5704,10 +5704,6 @@
   proname => 'pg_stat_get_checkpoint_sync_time', provolatile => 's',
   proparallel => 'r', prorettype => 'float8', proargtypes => '',
   prosrc => 'pg_stat_get_checkpoint_sync_time' },
-{ oid => '2775', descr => 'statistics: number of buffers written by backends',
-  proname => 'pg_stat_get_buf_written_backend', provolatile => 's',
-  proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_buf_written_backend' },
 { oid => '3063',
   descr => 'statistics: number of backend buffer writes that did their own fsync',
   proname => 'pg_stat_get_buf_fsync_backend', provolatile => 's',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index db9675884f..d1675909db 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -273,7 +273,6 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter checkpoint_write_time;	/* times in milliseconds */
 	PgStat_Counter checkpoint_sync_time;
 	PgStat_Counter buf_written_checkpoints;
-	PgStat_Counter buf_written_backend;
 	PgStat_Counter buf_fsync_backend;
 } PgStat_CheckpointerStats;
 
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index e7a2f5856a..c98f9cd747 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1821,7 +1821,6 @@ pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints
     pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
     pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-    pg_stat_get_buf_written_backend() AS buffers_backend,
     pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
-- 
2.34.1

From 8f2ca94acc8773d6c6ff6a4b2a00a4767ec63911 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Fri, 10 Feb 2023 11:51:20 +0000
Subject: [PATCH v7] Drop buffers_backend_fsync column from pg_stat_bgwriter
 view

---
 doc/src/sgml/monitoring.sgml                  | 11 ----------
 src/backend/access/transam/slru.c             |  4 ++++
 src/backend/catalog/system_views.sql          |  1 -
 src/backend/postmaster/checkpointer.c         | 22 ++-----------------
 .../utils/activity/pgstat_checkpointer.c      |  2 --
 src/backend/utils/adt/pgstatfuncs.c           |  6 -----
 src/include/catalog/pg_proc.dat               |  5 -----
 src/include/pgstat.h                          |  1 -
 src/test/regress/expected/rules.out           |  1 -
 9 files changed, 6 insertions(+), 47 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 380085eedd..5fe39b305d 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3766,17 +3766,6 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </para></entry>
      </row>
 
-     <row>
-      <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
-      </para>
-      <para>
-       Number of times a backend had to execute its own
-       <function>fsync</function> call (normally the background writer handles those
-       even when the backend does its own write)
-      </para></entry>
-     </row>
-
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>buffers_alloc</structfield> <type>bigint</type>
diff --git a/src/backend/access/transam/slru.c b/src/backend/access/transam/slru.c
index 5ab86238a9..4ae2040f39 100644
--- a/src/backend/access/transam/slru.c
+++ b/src/backend/access/transam/slru.c
@@ -1593,10 +1593,14 @@ SlruScanDirectory(SlruCtl ctl, SlruScanCallback callback, void *data)
 int
 SlruSyncFileTag(SlruCtl ctl, const FileTag *ftag, char *path)
 {
+	SlruShared	shared = ctl->shared;
 	int			fd;
 	int			save_errno;
 	int			result;
 
+	/* update the stats counter of flushes */
+	pgstat_count_slru_flush(shared->slru_stats_idx);
+
 	SlruFileName(ctl, path, ftag->segno);
 
 	fd = OpenTransientFile(path, O_RDWR | PG_BINARY);
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 2b1b2bf7c3..7ef3d2ebd4 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1112,7 +1112,6 @@ CREATE VIEW pg_stat_bgwriter AS
         pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index baadd08044..12c92f3de9 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -91,15 +91,11 @@
  * requesting backends since the last checkpoint start.  The flags are
  * chosen so that OR'ing is the correct way to combine multiple requests.
  *
- * num_backend_fsync counts the subset of buffer writes performed by user
- * backend processes that also had to do their own fsync, because the
- * checkpointer failed to absorb their request.
- *
  * The requests array holds fsync requests sent by backends and not yet
  * absorbed by the checkpointer.
  *
- * Unlike the checkpoint fields, num_backend_fsync and the requests fields are
- * protected by CheckpointerCommLock.
+ * Unlike the checkpoint fields, reqquests related fields are protected by
+ * CheckpointerCommLock.
  *----------
  */
 typedef struct
@@ -123,8 +119,6 @@ typedef struct
 	ConditionVariable start_cv; /* signaled when ckpt_started advances */
 	ConditionVariable done_cv;	/* signaled when ckpt_done advances */
 
-	uint32		num_backend_fsync;	/* counts user backend fsync calls */
-
 	int			num_requests;	/* current # of requests */
 	int			max_requests;	/* allocated array size */
 	CheckpointerRequest requests[FLEXIBLE_ARRAY_MEMBER];
@@ -1102,12 +1096,6 @@ ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
 		(CheckpointerShmem->num_requests >= CheckpointerShmem->max_requests &&
 		 !CompactCheckpointerRequestQueue()))
 	{
-		/*
-		 * Count the subset of writes where backends have to do their own
-		 * fsync
-		 */
-		if (!AmBackgroundWriterProcess())
-			CheckpointerShmem->num_backend_fsync++;
 		LWLockRelease(CheckpointerCommLock);
 		return false;
 	}
@@ -1264,12 +1252,6 @@ AbsorbSyncRequests(void)
 
 	LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
 
-	/* Transfer stats counts into pending pgstats message */
-	PendingCheckpointerStats.buf_fsync_backend
-		+= CheckpointerShmem->num_backend_fsync;
-
-	CheckpointerShmem->num_backend_fsync = 0;
-
 	/*
 	 * We try to avoid holding the lock for a long time by copying the request
 	 * array, and processing the requests after releasing the lock.
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index a048205d6e..03ed5dddda 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -52,7 +52,6 @@ pgstat_report_checkpointer(void)
 	CHECKPOINTER_ACC(checkpoint_write_time);
 	CHECKPOINTER_ACC(checkpoint_sync_time);
 	CHECKPOINTER_ACC(buf_written_checkpoints);
-	CHECKPOINTER_ACC(buf_fsync_backend);
 #undef CHECKPOINTER_ACC
 
 	pgstat_end_changecount_write(&stats_shmem->changecount);
@@ -119,6 +118,5 @@ pgstat_checkpointer_snapshot_cb(void)
 	CHECKPOINTER_COMP(checkpoint_write_time);
 	CHECKPOINTER_COMP(checkpoint_sync_time);
 	CHECKPOINTER_COMP(buf_written_checkpoints);
-	CHECKPOINTER_COMP(buf_fsync_backend);
 #undef CHECKPOINTER_COMP
 }
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index ce16884f1b..7f4c39f052 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1227,12 +1227,6 @@ pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_bgwriter()->stat_reset_timestamp);
 }
 
-Datum
-pg_stat_get_buf_fsync_backend(PG_FUNCTION_ARGS)
-{
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_fsync_backend);
-}
-
 Datum
 pg_stat_get_buf_alloc(PG_FUNCTION_ARGS)
 {
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3188d9ee1f..84bacd0329 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5704,11 +5704,6 @@
   proname => 'pg_stat_get_checkpoint_sync_time', provolatile => 's',
   proparallel => 'r', prorettype => 'float8', proargtypes => '',
   prosrc => 'pg_stat_get_checkpoint_sync_time' },
-{ oid => '3063',
-  descr => 'statistics: number of backend buffer writes that did their own fsync',
-  proname => 'pg_stat_get_buf_fsync_backend', provolatile => 's',
-  proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_buf_fsync_backend' },
 { oid => '2859', descr => 'statistics: number of buffer allocations',
   proname => 'pg_stat_get_buf_alloc', provolatile => 's', proparallel => 'r',
   prorettype => 'int8', proargtypes => '', prosrc => 'pg_stat_get_buf_alloc' },
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index d1675909db..28fb6292d9 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -273,7 +273,6 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter checkpoint_write_time;	/* times in milliseconds */
 	PgStat_Counter checkpoint_sync_time;
 	PgStat_Counter buf_written_checkpoints;
-	PgStat_Counter buf_fsync_backend;
 } PgStat_CheckpointerStats;
 
 
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index c98f9cd747..d32f47cdb0 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1821,7 +1821,6 @@ pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints
     pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
     pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-    pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT oid AS datid,
-- 
2.34.1

From c7dd583d288add34a7fdb412675d2b6258480f1e Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Fri, 10 Feb 2023 16:04:27 +0000
Subject: [PATCH v7] Introduce a new view for checkpointer related stats

pg_stat_bgwriter view currently reports checkpointer stats as well.
It is that way because historically checkpointer was part of
bgwriter until the commits 806a2ae and bf405ba, that went into
PG 9.2, separated them out.

It is time for us to separate checkpointer stats to its own view
called pg_stat_checkpointer.

Bump catalog version.
---
 doc/src/sgml/monitoring.sgml                  | 98 ++++++++++++++-----
 src/backend/catalog/system_views.sql          | 14 ++-
 .../utils/activity/pgstat_checkpointer.c      |  1 +
 src/backend/utils/adt/pgstatfuncs.c           | 19 ++--
 src/include/catalog/pg_proc.dat               | 22 +++--
 src/include/pgstat.h                          |  1 +
 src/test/recovery/t/029_stats_restart.pl      |  6 +-
 src/test/regress/expected/rules.out           | 13 +--
 src/test/regress/expected/stats.out           | 21 +++-
 src/test/regress/sql/stats.sql                | 12 ++-
 10 files changed, 146 insertions(+), 61 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 5fe39b305d..13f9ded5f3 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -451,6 +451,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
      </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
+      <entry>One row only, showing statistics about the
+       checkpointer process's activity. See
+       <link linkend="monitoring-pg-stat-checkpointer-view">
+       <structname>pg_stat_checkpointer</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_database</structname><indexterm><primary>pg_stat_database</primary></indexterm></entry>
       <entry>One row per database, showing database-wide statistics. See
@@ -3681,7 +3690,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
 
   <para>
    The <structname>pg_stat_bgwriter</structname> view will always have a
-   single row, containing global data for the cluster.
+   single row, containing data about the bgwriter of the cluster.
   </para>
 
   <table id="pg-stat-bgwriter-view" xreflabel="pg_stat_bgwriter">
@@ -3701,77 +3710,118 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
     <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_timed</structfield> <type>bigint</type>
+       <structfield>buffers_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of scheduled checkpoints that have been performed
+       Number of buffers written by the background writer
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_req</structfield> <type>bigint</type>
+       <structfield>maxwritten_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of requested checkpoints that have been performed
+       Number of times the background writer stopped a cleaning
+       scan because it had written too many buffers
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
+       <structfield>buffers_alloc</structfield> <type>bigint</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are written to disk, in milliseconds
+       Number of buffers allocated
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are synchronized to disk, in
-       milliseconds
+       Time at which these statistics were last reset
       </para></entry>
      </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
 
+ <sect2 id="monitoring-pg-stat-checkpointer-view">
+  <title><structname>pg_stat_checkpointer</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_checkpointer</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_checkpointer</structname> view will always have a
+   single row, containing data about the checkpointer process of the cluster.
+  </para>
+
+  <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
+   <title><structname>pg_stat_checkpointer</structname> View</title>
+   <tgroup cols="1">
+    <thead>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
+       Column Type
       </para>
       <para>
-       Number of buffers written during checkpoints
+       Description
       </para></entry>
      </row>
+    </thead>
 
+    <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_clean</structfield> <type>bigint</type>
+       <structfield>timed_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written by the background writer
+       Number of scheduled checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>maxwritten_clean</structfield> <type>bigint</type>
+       <structfield>requested_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of times the background writer stopped a cleaning
-       scan because it had written too many buffers
+       Number of requested checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_alloc</structfield> <type>bigint</type>
+       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of buffers allocated
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are written to disk, in milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+      </para>
+      <para>
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are synchronized to disk, in
+       milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_written_checkpoints</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written during checkpoints
       </para></entry>
      </row>
 
@@ -5421,8 +5471,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         Resets some cluster-wide statistics counters to zero, depending on the
         argument.  The argument can be <literal>bgwriter</literal> to reset
         all the counters shown in
-        the <structname>pg_stat_bgwriter</structname>
-        view, <literal>archiver</literal> to reset all the counters shown in
+        the <structname>pg_stat_bgwriter</structname> view,
+        <literal>checkpointer</literal> to reset all the counters shown in
+        the <structname>pg_stat_checkpointer</structname> view,
+        <literal>archiver</literal> to reset all the counters shown in
         the <structname>pg_stat_archiver</structname> view,
         <literal>io</literal> to reset all the counters shown in the
         <structname>pg_stat_io</structname> view,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 7ef3d2ebd4..8fc8c0908f 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1105,16 +1105,20 @@ CREATE VIEW pg_stat_archiver AS
 
 CREATE VIEW pg_stat_bgwriter AS
     SELECT
-        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-        pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-        pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_checkpointer AS
+    SELECT
+        pg_stat_get_timed_checkpoints() AS timed_checkpoints,
+        pg_stat_get_requested_checkpoints() AS requested_checkpoints,
+        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+        pg_stat_get_buf_written_checkpoints() AS buffers_written_checkpoints,
+        pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
+
 CREATE VIEW pg_stat_wal AS
     SELECT
         w.wal_records,
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index 03ed5dddda..aa0b7d2c06 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -92,6 +92,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
 									&stats_shmem->stats,
 									sizeof(stats_shmem->stats),
 									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
 	LWLockRelease(&stats_shmem->lock);
 }
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 7f4c39f052..1a2390977e 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1176,19 +1176,19 @@ PG_STAT_GET_DBENTRY_FLOAT8(idle_in_transaction_time)
 PG_STAT_GET_DBENTRY_FLOAT8(session_time)
 
 Datum
-pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_timed_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_requested_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_buf_written_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
 }
@@ -1221,6 +1221,12 @@ pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
 					 pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
 }
 
+Datum
+pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
+}
+
 Datum
 pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 {
@@ -1589,14 +1595,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 	if (strcmp(target, "archiver") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
 	else if (strcmp(target, "bgwriter") == 0)
-	{
-		/*
-		 * Historically checkpointer was part of bgwriter, continue to reset
-		 * both for now.
-		 */
 		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+	else if (strcmp(target, "checkpointer") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
-	}
 	else if (strcmp(target, "io") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_IO);
 	else if (strcmp(target, "recovery_prefetch") == 0)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 84bacd0329..e5e716f349 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5666,20 +5666,24 @@
   proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}',
   prosrc => 'pg_stat_get_archiver' },
 { oid => '2769',
-  descr => 'statistics: number of timed checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_timed_checkpoints', provolatile => 's',
+  descr => 'statistics: number of timed checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_timed_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_timed_checkpoints' },
+  prosrc => 'pg_stat_get_timed_checkpoints' },
 { oid => '2770',
-  descr => 'statistics: number of backend requested checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_requested_checkpoints', provolatile => 's',
+  descr => 'statistics: number of backend requested checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_requested_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_requested_checkpoints' },
+  prosrc => 'pg_stat_get_requested_checkpoints' },
 { oid => '2771',
-  descr => 'statistics: number of buffers written by the bgwriter during checkpoints',
-  proname => 'pg_stat_get_bgwriter_buf_written_checkpoints', provolatile => 's',
+  descr => 'statistics: number of buffers written by the checkpointer',
+  proname => 'pg_stat_get_buf_written_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_buf_written_checkpoints' },
+  prosrc => 'pg_stat_get_buf_written_checkpoints' },
+{ oid => '8206', descr => 'statistics: last reset for the checkpointer',
+  proname => 'pg_stat_get_checkpointer_stat_reset_time', provolatile => 's',
+  proparallel => 'r', prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_stat_get_checkpointer_stat_reset_time' },
 { oid => '2772',
   descr => 'statistics: number of buffers written by the bgwriter for cleaning dirty buffers',
   proname => 'pg_stat_get_bgwriter_buf_written_clean', provolatile => 's',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 28fb6292d9..b08928cefc 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -273,6 +273,7 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter checkpoint_write_time;	/* times in milliseconds */
 	PgStat_Counter checkpoint_sync_time;
 	PgStat_Counter buf_written_checkpoints;
+	TimestampTz stat_reset_timestamp;
 } PgStat_CheckpointerStats;
 
 
diff --git a/src/test/recovery/t/029_stats_restart.pl b/src/test/recovery/t/029_stats_restart.pl
index 83d6647d32..463f29101e 100644
--- a/src/test/recovery/t/029_stats_restart.pl
+++ b/src/test/recovery/t/029_stats_restart.pl
@@ -173,7 +173,7 @@ is($wal_start->{reset}, $wal_restart->{reset},
 
 ## Check that checkpoint stats are reset, WAL stats aren't affected
 
-$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('bgwriter')");
+$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('checkpointer')");
 
 $sect = "post ckpt reset";
 my $ckpt_reset     = checkpoint_stats();
@@ -323,9 +323,9 @@ sub checkpoint_stats
 	my %results;
 
 	$results{count} = $node->safe_psql($connect_db,
-		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter");
+		"SELECT timed_checkpoints + requested_checkpoints FROM pg_stat_checkpointer");
 	$results{reset} = $node->safe_psql($connect_db,
-		"SELECT stats_reset FROM pg_stat_bgwriter");
+		"SELECT stats_reset FROM pg_stat_checkpointer");
 
 	return \%results;
 }
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index d32f47cdb0..7eae7f4184 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1814,15 +1814,16 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
-pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
-    pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
+pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+pg_stat_checkpointer| SELECT pg_stat_get_timed_checkpoints() AS timed_checkpoints,
+    pg_stat_get_requested_checkpoints() AS requested_checkpoints,
+    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+    pg_stat_get_buf_written_checkpoints() AS buffers_written_checkpoints,
+    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT oid AS datid,
     datname,
         CASE
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 1d84407a03..85aaebe7b6 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -782,8 +782,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
  t
 (1 row)
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT requested_checkpoints AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
 CREATE TEMP TABLE test_stats_temp AS SELECT 17;
@@ -793,7 +793,7 @@ DROP TABLE test_stats_temp;
 -- results of the first.
 CHECKPOINT;
 CHECKPOINT;
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT requested_checkpoints > :rqst_ckpts_before FROM pg_stat_checkpointer;
  ?column? 
 ----------
  t
@@ -884,6 +884,21 @@ SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 (1 row)
 
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index b4d6753c71..e867bc15e3 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -387,8 +387,8 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
 SELECT pg_stat_force_next_flush();
 SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database());
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT requested_checkpoints AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
@@ -402,7 +402,7 @@ DROP TABLE test_stats_temp;
 CHECKPOINT;
 CHECKPOINT;
 
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT requested_checkpoints > :rqst_ckpts_before FROM pg_stat_checkpointer;
 SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
 
 -- Test pg_stat_get_backend_idset() and some allied functions.
@@ -440,6 +440,12 @@ SELECT pg_stat_reset_shared('bgwriter');
 SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
 
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
-- 
2.34.1

From c7d1a10b113c90e3712e5f836c21b5a40f909a24 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Mon, 13 Feb 2023 05:01:52 +0000
Subject: [PATCH v8] Drop buffers_backend column from pg_stat_bgwriter view

---
 doc/src/sgml/monitoring.sgml                  |  9 ---------
 src/backend/catalog/system_views.sql          |  1 -
 src/backend/postmaster/checkpointer.c         | 20 +++++--------------
 .../utils/activity/pgstat_checkpointer.c      |  2 --
 src/backend/utils/adt/pgstatfuncs.c           |  6 ------
 src/include/catalog/pg_proc.dat               |  4 ----
 src/include/pgstat.h                          |  1 -
 src/test/regress/expected/rules.out           |  1 -
 8 files changed, 5 insertions(+), 39 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index dca50707ad..c0cae0f4f3 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -4059,15 +4059,6 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </para></entry>
      </row>
 
-     <row>
-      <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend</structfield> <type>bigint</type>
-      </para>
-      <para>
-       Number of buffers written directly by a backend
-      </para></entry>
-     </row>
-
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 34ca0e739f..9bb96e27aa 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1112,7 +1112,6 @@ CREATE VIEW pg_stat_bgwriter AS
         pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-        pg_stat_get_buf_written_backend() AS buffers_backend,
         pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index aaad5c5228..baadd08044 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -91,17 +91,15 @@
  * requesting backends since the last checkpoint start.  The flags are
  * chosen so that OR'ing is the correct way to combine multiple requests.
  *
- * num_backend_writes is used to count the number of buffer writes performed
- * by user backend processes.  This counter should be wide enough that it
- * can't overflow during a single processing cycle.  num_backend_fsync
- * counts the subset of those writes that also had to do their own fsync,
- * because the checkpointer failed to absorb their request.
+ * num_backend_fsync counts the subset of buffer writes performed by user
+ * backend processes that also had to do their own fsync, because the
+ * checkpointer failed to absorb their request.
  *
  * The requests array holds fsync requests sent by backends and not yet
  * absorbed by the checkpointer.
  *
- * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
- * the requests fields are protected by CheckpointerCommLock.
+ * Unlike the checkpoint fields, num_backend_fsync and the requests fields are
+ * protected by CheckpointerCommLock.
  *----------
  */
 typedef struct
@@ -125,7 +123,6 @@ typedef struct
 	ConditionVariable start_cv; /* signaled when ckpt_started advances */
 	ConditionVariable done_cv;	/* signaled when ckpt_done advances */
 
-	uint32		num_backend_writes; /* counts user backend buffer writes */
 	uint32		num_backend_fsync;	/* counts user backend fsync calls */
 
 	int			num_requests;	/* current # of requests */
@@ -1096,10 +1093,6 @@ ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
 
 	LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
 
-	/* Count all backend writes regardless of if they fit in the queue */
-	if (!AmBackgroundWriterProcess())
-		CheckpointerShmem->num_backend_writes++;
-
 	/*
 	 * If the checkpointer isn't running or the request queue is full, the
 	 * backend will have to perform its own fsync request.  But before forcing
@@ -1272,12 +1265,9 @@ AbsorbSyncRequests(void)
 	LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
 
 	/* Transfer stats counts into pending pgstats message */
-	PendingCheckpointerStats.buf_written_backend
-		+= CheckpointerShmem->num_backend_writes;
 	PendingCheckpointerStats.buf_fsync_backend
 		+= CheckpointerShmem->num_backend_fsync;
 
-	CheckpointerShmem->num_backend_writes = 0;
 	CheckpointerShmem->num_backend_fsync = 0;
 
 	/*
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index 26dec112f6..a048205d6e 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -52,7 +52,6 @@ pgstat_report_checkpointer(void)
 	CHECKPOINTER_ACC(checkpoint_write_time);
 	CHECKPOINTER_ACC(checkpoint_sync_time);
 	CHECKPOINTER_ACC(buf_written_checkpoints);
-	CHECKPOINTER_ACC(buf_written_backend);
 	CHECKPOINTER_ACC(buf_fsync_backend);
 #undef CHECKPOINTER_ACC
 
@@ -120,7 +119,6 @@ pgstat_checkpointer_snapshot_cb(void)
 	CHECKPOINTER_COMP(checkpoint_write_time);
 	CHECKPOINTER_COMP(checkpoint_sync_time);
 	CHECKPOINTER_COMP(buf_written_checkpoints);
-	CHECKPOINTER_COMP(buf_written_backend);
 	CHECKPOINTER_COMP(buf_fsync_backend);
 #undef CHECKPOINTER_COMP
 }
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 9d707c3521..28075fa6fb 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1227,12 +1227,6 @@ pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_bgwriter()->stat_reset_timestamp);
 }
 
-Datum
-pg_stat_get_buf_written_backend(PG_FUNCTION_ARGS)
-{
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_backend);
-}
-
 Datum
 pg_stat_get_buf_fsync_backend(PG_FUNCTION_ARGS)
 {
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 66b73c3900..e800fdfd5f 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5704,10 +5704,6 @@
   proname => 'pg_stat_get_checkpoint_sync_time', provolatile => 's',
   proparallel => 'r', prorettype => 'float8', proargtypes => '',
   prosrc => 'pg_stat_get_checkpoint_sync_time' },
-{ oid => '2775', descr => 'statistics: number of buffers written by backends',
-  proname => 'pg_stat_get_buf_written_backend', provolatile => 's',
-  proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_buf_written_backend' },
 { oid => '3063',
   descr => 'statistics: number of backend buffer writes that did their own fsync',
   proname => 'pg_stat_get_buf_fsync_backend', provolatile => 's',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index db9675884f..d1675909db 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -273,7 +273,6 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter checkpoint_write_time;	/* times in milliseconds */
 	PgStat_Counter checkpoint_sync_time;
 	PgStat_Counter buf_written_checkpoints;
-	PgStat_Counter buf_written_backend;
 	PgStat_Counter buf_fsync_backend;
 } PgStat_CheckpointerStats;
 
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 174b725fff..5b4f441245 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1821,7 +1821,6 @@ pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints
     pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
     pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-    pg_stat_get_buf_written_backend() AS buffers_backend,
     pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
-- 
2.34.1

From 09afb4d2da776b863aee9d87f475eb8cd852d44c Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Mon, 13 Feb 2023 05:02:17 +0000
Subject: [PATCH v8] Drop buffers_backend_fsync column from pg_stat_bgwriter
 view

---
 doc/src/sgml/monitoring.sgml                  | 11 ----------
 src/backend/access/transam/slru.c             |  4 ++++
 src/backend/catalog/system_views.sql          |  1 -
 src/backend/postmaster/checkpointer.c         | 22 ++-----------------
 .../utils/activity/pgstat_checkpointer.c      |  2 --
 src/backend/utils/adt/pgstatfuncs.c           |  6 -----
 src/include/catalog/pg_proc.dat               |  5 -----
 src/include/pgstat.h                          |  1 -
 src/test/regress/expected/rules.out           |  1 -
 9 files changed, 6 insertions(+), 47 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index c0cae0f4f3..098ca5999d 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -4059,17 +4059,6 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </para></entry>
      </row>
 
-     <row>
-      <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
-      </para>
-      <para>
-       Number of times a backend had to execute its own
-       <function>fsync</function> call (normally the background writer handles those
-       even when the backend does its own write)
-      </para></entry>
-     </row>
-
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>buffers_alloc</structfield> <type>bigint</type>
diff --git a/src/backend/access/transam/slru.c b/src/backend/access/transam/slru.c
index 5ab86238a9..4ae2040f39 100644
--- a/src/backend/access/transam/slru.c
+++ b/src/backend/access/transam/slru.c
@@ -1593,10 +1593,14 @@ SlruScanDirectory(SlruCtl ctl, SlruScanCallback callback, void *data)
 int
 SlruSyncFileTag(SlruCtl ctl, const FileTag *ftag, char *path)
 {
+	SlruShared	shared = ctl->shared;
 	int			fd;
 	int			save_errno;
 	int			result;
 
+	/* update the stats counter of flushes */
+	pgstat_count_slru_flush(shared->slru_stats_idx);
+
 	SlruFileName(ctl, path, ftag->segno);
 
 	fd = OpenTransientFile(path, O_RDWR | PG_BINARY);
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 9bb96e27aa..2b8e462532 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1112,7 +1112,6 @@ CREATE VIEW pg_stat_bgwriter AS
         pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index baadd08044..12c92f3de9 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -91,15 +91,11 @@
  * requesting backends since the last checkpoint start.  The flags are
  * chosen so that OR'ing is the correct way to combine multiple requests.
  *
- * num_backend_fsync counts the subset of buffer writes performed by user
- * backend processes that also had to do their own fsync, because the
- * checkpointer failed to absorb their request.
- *
  * The requests array holds fsync requests sent by backends and not yet
  * absorbed by the checkpointer.
  *
- * Unlike the checkpoint fields, num_backend_fsync and the requests fields are
- * protected by CheckpointerCommLock.
+ * Unlike the checkpoint fields, reqquests related fields are protected by
+ * CheckpointerCommLock.
  *----------
  */
 typedef struct
@@ -123,8 +119,6 @@ typedef struct
 	ConditionVariable start_cv; /* signaled when ckpt_started advances */
 	ConditionVariable done_cv;	/* signaled when ckpt_done advances */
 
-	uint32		num_backend_fsync;	/* counts user backend fsync calls */
-
 	int			num_requests;	/* current # of requests */
 	int			max_requests;	/* allocated array size */
 	CheckpointerRequest requests[FLEXIBLE_ARRAY_MEMBER];
@@ -1102,12 +1096,6 @@ ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
 		(CheckpointerShmem->num_requests >= CheckpointerShmem->max_requests &&
 		 !CompactCheckpointerRequestQueue()))
 	{
-		/*
-		 * Count the subset of writes where backends have to do their own
-		 * fsync
-		 */
-		if (!AmBackgroundWriterProcess())
-			CheckpointerShmem->num_backend_fsync++;
 		LWLockRelease(CheckpointerCommLock);
 		return false;
 	}
@@ -1264,12 +1252,6 @@ AbsorbSyncRequests(void)
 
 	LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
 
-	/* Transfer stats counts into pending pgstats message */
-	PendingCheckpointerStats.buf_fsync_backend
-		+= CheckpointerShmem->num_backend_fsync;
-
-	CheckpointerShmem->num_backend_fsync = 0;
-
 	/*
 	 * We try to avoid holding the lock for a long time by copying the request
 	 * array, and processing the requests after releasing the lock.
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index a048205d6e..03ed5dddda 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -52,7 +52,6 @@ pgstat_report_checkpointer(void)
 	CHECKPOINTER_ACC(checkpoint_write_time);
 	CHECKPOINTER_ACC(checkpoint_sync_time);
 	CHECKPOINTER_ACC(buf_written_checkpoints);
-	CHECKPOINTER_ACC(buf_fsync_backend);
 #undef CHECKPOINTER_ACC
 
 	pgstat_end_changecount_write(&stats_shmem->changecount);
@@ -119,6 +118,5 @@ pgstat_checkpointer_snapshot_cb(void)
 	CHECKPOINTER_COMP(checkpoint_write_time);
 	CHECKPOINTER_COMP(checkpoint_sync_time);
 	CHECKPOINTER_COMP(buf_written_checkpoints);
-	CHECKPOINTER_COMP(buf_fsync_backend);
 #undef CHECKPOINTER_COMP
 }
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 28075fa6fb..087ba87a86 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1227,12 +1227,6 @@ pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_bgwriter()->stat_reset_timestamp);
 }
 
-Datum
-pg_stat_get_buf_fsync_backend(PG_FUNCTION_ARGS)
-{
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_fsync_backend);
-}
-
 Datum
 pg_stat_get_buf_alloc(PG_FUNCTION_ARGS)
 {
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index e800fdfd5f..5ed66af0e3 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5704,11 +5704,6 @@
   proname => 'pg_stat_get_checkpoint_sync_time', provolatile => 's',
   proparallel => 'r', prorettype => 'float8', proargtypes => '',
   prosrc => 'pg_stat_get_checkpoint_sync_time' },
-{ oid => '3063',
-  descr => 'statistics: number of backend buffer writes that did their own fsync',
-  proname => 'pg_stat_get_buf_fsync_backend', provolatile => 's',
-  proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_buf_fsync_backend' },
 { oid => '2859', descr => 'statistics: number of buffer allocations',
   proname => 'pg_stat_get_buf_alloc', provolatile => 's', proparallel => 'r',
   prorettype => 'int8', proargtypes => '', prosrc => 'pg_stat_get_buf_alloc' },
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index d1675909db..28fb6292d9 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -273,7 +273,6 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter checkpoint_write_time;	/* times in milliseconds */
 	PgStat_Counter checkpoint_sync_time;
 	PgStat_Counter buf_written_checkpoints;
-	PgStat_Counter buf_fsync_backend;
 } PgStat_CheckpointerStats;
 
 
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 5b4f441245..9c9adb6140 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1821,7 +1821,6 @@ pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints
     pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
     pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-    pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT oid AS datid,
-- 
2.34.1

From 5b349d6b3a3b8db1498e038aed81909fd1f15fe4 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Mon, 13 Feb 2023 05:05:07 +0000
Subject: [PATCH v8] Introduce a new view for checkpointer related stats

pg_stat_bgwriter view currently reports checkpointer stats as well.
It is that way because historically checkpointer was part of
bgwriter until the commits 806a2ae and bf405ba, that went into
PG 9.2, separated them out.

It is time for us to separate checkpointer stats to its own view
called pg_stat_checkpointer.

Bump catalog version.
---
 doc/src/sgml/monitoring.sgml                  | 98 ++++++++++++++-----
 src/backend/catalog/system_views.sql          | 14 ++-
 .../utils/activity/pgstat_checkpointer.c      |  1 +
 src/backend/utils/adt/pgstatfuncs.c           | 19 ++--
 src/include/catalog/pg_proc.dat               | 22 +++--
 src/include/pgstat.h                          |  1 +
 src/test/recovery/t/029_stats_restart.pl      |  6 +-
 src/test/regress/expected/rules.out           | 13 +--
 src/test/regress/expected/stats.out           | 21 +++-
 src/test/regress/sql/stats.sql                | 12 ++-
 10 files changed, 146 insertions(+), 61 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 098ca5999d..47bf6ff247 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -451,6 +451,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
      </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
+      <entry>One row only, showing statistics about the
+       checkpointer process's activity. See
+       <link linkend="monitoring-pg-stat-checkpointer-view">
+       <structname>pg_stat_checkpointer</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_database</structname><indexterm><primary>pg_stat_database</primary></indexterm></entry>
       <entry>One row per database, showing database-wide statistics. See
@@ -3974,7 +3983,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
 
   <para>
    The <structname>pg_stat_bgwriter</structname> view will always have a
-   single row, containing global data for the cluster.
+   single row, containing data about the bgwriter of the cluster.
   </para>
 
   <table id="pg-stat-bgwriter-view" xreflabel="pg_stat_bgwriter">
@@ -3994,77 +4003,118 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
     <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_timed</structfield> <type>bigint</type>
+       <structfield>buffers_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of scheduled checkpoints that have been performed
+       Number of buffers written by the background writer
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_req</structfield> <type>bigint</type>
+       <structfield>maxwritten_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of requested checkpoints that have been performed
+       Number of times the background writer stopped a cleaning
+       scan because it had written too many buffers
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
+       <structfield>buffers_alloc</structfield> <type>bigint</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are written to disk, in milliseconds
+       Number of buffers allocated
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are synchronized to disk, in
-       milliseconds
+       Time at which these statistics were last reset
       </para></entry>
      </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
 
+ <sect2 id="monitoring-pg-stat-checkpointer-view">
+  <title><structname>pg_stat_checkpointer</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_checkpointer</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_checkpointer</structname> view will always have a
+   single row, containing data about the checkpointer process of the cluster.
+  </para>
+
+  <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
+   <title><structname>pg_stat_checkpointer</structname> View</title>
+   <tgroup cols="1">
+    <thead>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
+       Column Type
       </para>
       <para>
-       Number of buffers written during checkpoints
+       Description
       </para></entry>
      </row>
+    </thead>
 
+    <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_clean</structfield> <type>bigint</type>
+       <structfield>timed_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written by the background writer
+       Number of scheduled checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>maxwritten_clean</structfield> <type>bigint</type>
+       <structfield>requested_checkpoints</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of times the background writer stopped a cleaning
-       scan because it had written too many buffers
+       Number of requested checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_alloc</structfield> <type>bigint</type>
+       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of buffers allocated
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are written to disk, in milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+      </para>
+      <para>
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are synchronized to disk, in
+       milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_written_checkpoints</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written during checkpoints
       </para></entry>
      </row>
 
@@ -5714,8 +5764,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         Resets some cluster-wide statistics counters to zero, depending on the
         argument.  The argument can be <literal>bgwriter</literal> to reset
         all the counters shown in
-        the <structname>pg_stat_bgwriter</structname>
-        view, <literal>archiver</literal> to reset all the counters shown in
+        the <structname>pg_stat_bgwriter</structname> view,
+        <literal>checkpointer</literal> to reset all the counters shown in
+        the <structname>pg_stat_checkpointer</structname> view,
+        <literal>archiver</literal> to reset all the counters shown in
         the <structname>pg_stat_archiver</structname> view,
         <literal>io</literal> to reset all the counters shown in the
         <structname>pg_stat_io</structname> view,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 2b8e462532..ad2992fd25 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1105,16 +1105,20 @@ CREATE VIEW pg_stat_archiver AS
 
 CREATE VIEW pg_stat_bgwriter AS
     SELECT
-        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-        pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-        pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_checkpointer AS
+    SELECT
+        pg_stat_get_timed_checkpoints() AS timed_checkpoints,
+        pg_stat_get_requested_checkpoints() AS requested_checkpoints,
+        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+        pg_stat_get_buf_written_checkpoints() AS buffers_written_checkpoints,
+        pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
+
 CREATE VIEW pg_stat_io AS
 SELECT
        b.backend_type,
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index 03ed5dddda..aa0b7d2c06 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -92,6 +92,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
 									&stats_shmem->stats,
 									sizeof(stats_shmem->stats),
 									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
 	LWLockRelease(&stats_shmem->lock);
 }
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 087ba87a86..f2395fc13c 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1176,19 +1176,19 @@ PG_STAT_GET_DBENTRY_FLOAT8(idle_in_transaction_time)
 PG_STAT_GET_DBENTRY_FLOAT8(session_time)
 
 Datum
-pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_timed_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_requested_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
 }
 
 Datum
-pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_buf_written_checkpoints(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
 }
@@ -1221,6 +1221,12 @@ pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
 					 pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
 }
 
+Datum
+pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
+}
+
 Datum
 pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 {
@@ -1730,14 +1736,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 	if (strcmp(target, "archiver") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
 	else if (strcmp(target, "bgwriter") == 0)
-	{
-		/*
-		 * Historically checkpointer was part of bgwriter, continue to reset
-		 * both for now.
-		 */
 		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+	else if (strcmp(target, "checkpointer") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
-	}
 	else if (strcmp(target, "io") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_IO);
 	else if (strcmp(target, "recovery_prefetch") == 0)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 5ed66af0e3..7030597d67 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5666,20 +5666,24 @@
   proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}',
   prosrc => 'pg_stat_get_archiver' },
 { oid => '2769',
-  descr => 'statistics: number of timed checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_timed_checkpoints', provolatile => 's',
+  descr => 'statistics: number of timed checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_timed_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_timed_checkpoints' },
+  prosrc => 'pg_stat_get_timed_checkpoints' },
 { oid => '2770',
-  descr => 'statistics: number of backend requested checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_requested_checkpoints', provolatile => 's',
+  descr => 'statistics: number of backend requested checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_requested_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_requested_checkpoints' },
+  prosrc => 'pg_stat_get_requested_checkpoints' },
 { oid => '2771',
-  descr => 'statistics: number of buffers written by the bgwriter during checkpoints',
-  proname => 'pg_stat_get_bgwriter_buf_written_checkpoints', provolatile => 's',
+  descr => 'statistics: number of buffers written by the checkpointer',
+  proname => 'pg_stat_get_buf_written_checkpoints', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_buf_written_checkpoints' },
+  prosrc => 'pg_stat_get_buf_written_checkpoints' },
+{ oid => '8206', descr => 'statistics: last reset for the checkpointer',
+  proname => 'pg_stat_get_checkpointer_stat_reset_time', provolatile => 's',
+  proparallel => 'r', prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_stat_get_checkpointer_stat_reset_time' },
 { oid => '2772',
   descr => 'statistics: number of buffers written by the bgwriter for cleaning dirty buffers',
   proname => 'pg_stat_get_bgwriter_buf_written_clean', provolatile => 's',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 28fb6292d9..b08928cefc 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -273,6 +273,7 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter checkpoint_write_time;	/* times in milliseconds */
 	PgStat_Counter checkpoint_sync_time;
 	PgStat_Counter buf_written_checkpoints;
+	TimestampTz stat_reset_timestamp;
 } PgStat_CheckpointerStats;
 
 
diff --git a/src/test/recovery/t/029_stats_restart.pl b/src/test/recovery/t/029_stats_restart.pl
index 83d6647d32..463f29101e 100644
--- a/src/test/recovery/t/029_stats_restart.pl
+++ b/src/test/recovery/t/029_stats_restart.pl
@@ -173,7 +173,7 @@ is($wal_start->{reset}, $wal_restart->{reset},
 
 ## Check that checkpoint stats are reset, WAL stats aren't affected
 
-$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('bgwriter')");
+$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('checkpointer')");
 
 $sect = "post ckpt reset";
 my $ckpt_reset     = checkpoint_stats();
@@ -323,9 +323,9 @@ sub checkpoint_stats
 	my %results;
 
 	$results{count} = $node->safe_psql($connect_db,
-		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter");
+		"SELECT timed_checkpoints + requested_checkpoints FROM pg_stat_checkpointer");
 	$results{reset} = $node->safe_psql($connect_db,
-		"SELECT stats_reset FROM pg_stat_bgwriter");
+		"SELECT stats_reset FROM pg_stat_checkpointer");
 
 	return \%results;
 }
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 9c9adb6140..f18c047a42 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1814,15 +1814,16 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
-pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
-    pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
+pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+pg_stat_checkpointer| SELECT pg_stat_get_timed_checkpoints() AS timed_checkpoints,
+    pg_stat_get_requested_checkpoints() AS requested_checkpoints,
+    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
+    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
+    pg_stat_get_buf_written_checkpoints() AS buffers_written_checkpoints,
+    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT oid AS datid,
     datname,
         CASE
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 937b2101b3..2bbe17ba7d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -782,8 +782,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
  t
 (1 row)
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT requested_checkpoints AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
 CREATE TEMP TABLE test_stats_temp AS SELECT 17;
@@ -793,7 +793,7 @@ DROP TABLE test_stats_temp;
 -- results of the first.
 CHECKPOINT;
 CHECKPOINT;
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT requested_checkpoints > :rqst_ckpts_before FROM pg_stat_checkpointer;
  ?column? 
 ----------
  t
@@ -884,6 +884,21 @@ SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 (1 row)
 
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 74e592aa8a..cfc9aa3a37 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -387,8 +387,8 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
 SELECT pg_stat_force_next_flush();
 SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database());
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT requested_checkpoints AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
@@ -402,7 +402,7 @@ DROP TABLE test_stats_temp;
 CHECKPOINT;
 CHECKPOINT;
 
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT requested_checkpoints > :rqst_ckpts_before FROM pg_stat_checkpointer;
 SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
 
 -- Test pg_stat_get_backend_idset() and some allied functions.
@@ -440,6 +440,12 @@ SELECT pg_stat_reset_shared('bgwriter');
 SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
 
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
-- 
2.34.1

From 28982a27f2c2480a68e3345dc0bbcb4a05f15410 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Thu, 26 Oct 2023 10:28:46 +0000
Subject: [PATCH v9] Do not count backend writes and fsycns in checkpointer
 stats

Two of the backend stats 1) number of buffers written directly by
a backend, 2) number of times a backend had to execute its own
fsync are being tracked in checkpointer stats and exposed to the
user via pg_stat_bgwriter view (columns buffers_backend and
buffers_backend_fsync). They are not actually checkpointer
properties but backend properties. Now that we have pg_stat_io to
track all the backend related stats including writes and fsyncs,
it is redundant/inaccurate to keep them in checkpointer stats.
This commit removes both of these columns from checkpointer stats.

Author: Bharath Rupireddy
Reviewed-by: Bertrand Drouvot, Andres Freund
Discussion: https://www.postgresql.org/message-id/20230210004604.mcszbscsqs3bc5nx%40awork3.anarazel.de
---
 doc/src/sgml/monitoring.sgml                  | 20 ------------
 src/backend/catalog/system_views.sql          |  2 --
 src/backend/postmaster/checkpointer.c         | 32 ++-----------------
 .../utils/activity/pgstat_checkpointer.c      |  4 ---
 src/backend/utils/adt/pgstatfuncs.c           | 12 -------
 src/include/catalog/pg_proc.dat               |  9 ------
 src/include/pgstat.h                          |  2 --
 src/test/regress/expected/rules.out           |  2 --
 8 files changed, 2 insertions(+), 81 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f49ff79f3..9fea60b5b2 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -2953,26 +2953,6 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
-     <row>
-      <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend</structfield> <type>bigint</type>
-      </para>
-      <para>
-       Number of buffers written directly by a backend
-      </para></entry>
-     </row>
-
-     <row>
-      <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_backend_fsync</structfield> <type>bigint</type>
-      </para>
-      <para>
-       Number of times a backend had to execute its own
-       <function>fsync</function> call (normally the background writer handles those
-       even when the backend does its own write)
-      </para></entry>
-     </row>
-
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>buffers_alloc</structfield> <type>bigint</type>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index fcb14976c0..886f175fc2 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1118,8 +1118,6 @@ CREATE VIEW pg_stat_bgwriter AS
         pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-        pg_stat_get_buf_written_backend() AS buffers_backend,
-        pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index ace9893d95..4fe403c9a8 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -91,17 +91,11 @@
  * requesting backends since the last checkpoint start.  The flags are
  * chosen so that OR'ing is the correct way to combine multiple requests.
  *
- * num_backend_writes is used to count the number of buffer writes performed
- * by user backend processes.  This counter should be wide enough that it
- * can't overflow during a single processing cycle.  num_backend_fsync
- * counts the subset of those writes that also had to do their own fsync,
- * because the checkpointer failed to absorb their request.
- *
  * The requests array holds fsync requests sent by backends and not yet
  * absorbed by the checkpointer.
  *
- * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
- * the requests fields are protected by CheckpointerCommLock.
+ * Unlike the checkpoint fields, requests related fields are protected by
+ * CheckpointerCommLock.
  *----------
  */
 typedef struct
@@ -125,9 +119,6 @@ typedef struct
 	ConditionVariable start_cv; /* signaled when ckpt_started advances */
 	ConditionVariable done_cv;	/* signaled when ckpt_done advances */
 
-	uint32		num_backend_writes; /* counts user backend buffer writes */
-	uint32		num_backend_fsync;	/* counts user backend fsync calls */
-
 	int			num_requests;	/* current # of requests */
 	int			max_requests;	/* allocated array size */
 	CheckpointerRequest requests[FLEXIBLE_ARRAY_MEMBER];
@@ -1095,10 +1086,6 @@ ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
 
 	LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
 
-	/* Count all backend writes regardless of if they fit in the queue */
-	if (!AmBackgroundWriterProcess())
-		CheckpointerShmem->num_backend_writes++;
-
 	/*
 	 * If the checkpointer isn't running or the request queue is full, the
 	 * backend will have to perform its own fsync request.  But before forcing
@@ -1108,12 +1095,6 @@ ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
 		(CheckpointerShmem->num_requests >= CheckpointerShmem->max_requests &&
 		 !CompactCheckpointerRequestQueue()))
 	{
-		/*
-		 * Count the subset of writes where backends have to do their own
-		 * fsync
-		 */
-		if (!AmBackgroundWriterProcess())
-			CheckpointerShmem->num_backend_fsync++;
 		LWLockRelease(CheckpointerCommLock);
 		return false;
 	}
@@ -1270,15 +1251,6 @@ AbsorbSyncRequests(void)
 
 	LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
 
-	/* Transfer stats counts into pending pgstats message */
-	PendingCheckpointerStats.buf_written_backend
-		+= CheckpointerShmem->num_backend_writes;
-	PendingCheckpointerStats.buf_fsync_backend
-		+= CheckpointerShmem->num_backend_fsync;
-
-	CheckpointerShmem->num_backend_writes = 0;
-	CheckpointerShmem->num_backend_fsync = 0;
-
 	/*
 	 * We try to avoid holding the lock for a long time by copying the request
 	 * array, and processing the requests after releasing the lock.
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index 26dec112f6..03ed5dddda 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -52,8 +52,6 @@ pgstat_report_checkpointer(void)
 	CHECKPOINTER_ACC(checkpoint_write_time);
 	CHECKPOINTER_ACC(checkpoint_sync_time);
 	CHECKPOINTER_ACC(buf_written_checkpoints);
-	CHECKPOINTER_ACC(buf_written_backend);
-	CHECKPOINTER_ACC(buf_fsync_backend);
 #undef CHECKPOINTER_ACC
 
 	pgstat_end_changecount_write(&stats_shmem->changecount);
@@ -120,7 +118,5 @@ pgstat_checkpointer_snapshot_cb(void)
 	CHECKPOINTER_COMP(checkpoint_write_time);
 	CHECKPOINTER_COMP(checkpoint_sync_time);
 	CHECKPOINTER_COMP(buf_written_checkpoints);
-	CHECKPOINTER_COMP(buf_written_backend);
-	CHECKPOINTER_COMP(buf_fsync_backend);
 #undef CHECKPOINTER_COMP
 }
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3b44af8006..6468b6a805 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1233,18 +1233,6 @@ pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_bgwriter()->stat_reset_timestamp);
 }
 
-Datum
-pg_stat_get_buf_written_backend(PG_FUNCTION_ARGS)
-{
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_backend);
-}
-
-Datum
-pg_stat_get_buf_fsync_backend(PG_FUNCTION_ARGS)
-{
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_fsync_backend);
-}
-
 Datum
 pg_stat_get_buf_alloc(PG_FUNCTION_ARGS)
 {
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 06435e8b92..bc41e92677 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5738,15 +5738,6 @@
   proname => 'pg_stat_get_checkpoint_sync_time', provolatile => 's',
   proparallel => 'r', prorettype => 'float8', proargtypes => '',
   prosrc => 'pg_stat_get_checkpoint_sync_time' },
-{ oid => '2775', descr => 'statistics: number of buffers written by backends',
-  proname => 'pg_stat_get_buf_written_backend', provolatile => 's',
-  proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_buf_written_backend' },
-{ oid => '3063',
-  descr => 'statistics: number of backend buffer writes that did their own fsync',
-  proname => 'pg_stat_get_buf_fsync_backend', provolatile => 's',
-  proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_buf_fsync_backend' },
 { oid => '2859', descr => 'statistics: number of buffer allocations',
   proname => 'pg_stat_get_buf_alloc', provolatile => 's', proparallel => 'r',
   prorettype => 'int8', proargtypes => '', prosrc => 'pg_stat_get_buf_alloc' },
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index fe2642f71a..e6fd20f1ce 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -265,8 +265,6 @@ typedef struct PgStat_CheckpointerStats
 	PgStat_Counter checkpoint_write_time;	/* times in milliseconds */
 	PgStat_Counter checkpoint_sync_time;
 	PgStat_Counter buf_written_checkpoints;
-	PgStat_Counter buf_written_backend;
-	PgStat_Counter buf_fsync_backend;
 } PgStat_CheckpointerStats;
 
 
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2c60400ade..798d1610f2 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1823,8 +1823,6 @@ pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints
     pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
     pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
-    pg_stat_get_buf_written_backend() AS buffers_backend,
-    pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT oid AS datid,
-- 
2.34.1

From 8a7680657fb0b97cf8ff47bdb77144eaa6978339 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Thu, 26 Oct 2023 12:52:34 +0000
Subject: [PATCH v9] Count SLRU page flushes during checkpoint or database
 shutdown

SLRU page flushes aren't counted during checkpoint or database
shutdown in SlruSyncFileTag unlike flushes following page writes
in SlruPhysicalWritePage. This commit fixes it by counting the
SLRU flushes even in SlruSyncFileTag.

Author: Bharath Rupireddy
Reviewed-by: Michael Paquier
Discussion: https://www.postgresql.org/message-id/ZTnIHhZiIPpEFLbL%40paquier.xyz
---
 src/backend/access/transam/slru.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/backend/access/transam/slru.c b/src/backend/access/transam/slru.c
index 9ed24e1185..9802b9e1fb 100644
--- a/src/backend/access/transam/slru.c
+++ b/src/backend/access/transam/slru.c
@@ -1593,6 +1593,7 @@ SlruScanDirectory(SlruCtl ctl, SlruScanCallback callback, void *data)
 int
 SlruSyncFileTag(SlruCtl ctl, const FileTag *ftag, char *path)
 {
+	SlruShared	shared = ctl->shared;
 	int			fd;
 	int			save_errno;
 	int			result;
@@ -1611,5 +1612,9 @@ SlruSyncFileTag(SlruCtl ctl, const FileTag *ftag, char *path)
 	CloseTransientFile(fd);
 
 	errno = save_errno;
+
+	/* update the stats counter of flushes */
+	pgstat_count_slru_flush(shared->slru_stats_idx);
+
 	return result;
 }
-- 
2.34.1

From 8843d6e49b7511d8e433058337698355f51c568c Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Thu, 26 Oct 2023 14:45:13 +0000
Subject: [PATCH v9] Introduce a new view for checkpointer related stats

pg_stat_bgwriter view currently reports checkpointer stats as
well. It has been that way so far because historically
checkpointer was part of bgwriter until the commits 806a2ae and
bf405ba separated them out way back in PG 9.2.

It is time for us to separate checkpointer stats to its own view
called pg_stat_checkpointer.

Bump catalog version.

Author: Bharath Rupireddy
Reviewed-by: Bertrand Drouvot, Andres Freund
Discussion: https://www.postgresql.org/message-id/CALj2ACVxX2ii%3D66RypXRweZe2EsBRiPMj0aHfRfHUeXJcC7kHg%40mail.gmail.com
---
 doc/src/sgml/monitoring.sgml                  | 98 ++++++++++++++-----
 src/backend/access/transam/xlog.c             |  4 +-
 src/backend/catalog/system_views.sql          | 14 ++-
 src/backend/postmaster/checkpointer.c         |  6 +-
 src/backend/storage/buffer/bufmgr.c           |  2 +-
 .../utils/activity/pgstat_checkpointer.c      | 21 ++--
 src/backend/utils/adt/pgstatfuncs.c           | 33 ++++---
 src/include/catalog/pg_proc.dat               | 30 +++---
 src/include/pgstat.h                          | 11 ++-
 src/test/recovery/t/029_stats_restart.pl      |  6 +-
 src/test/regress/expected/rules.out           | 13 +--
 src/test/regress/expected/stats.out           | 21 +++-
 src/test/regress/sql/stats.sql                | 12 ++-
 13 files changed, 178 insertions(+), 93 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 9fea60b5b2..0792dadc9b 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -451,6 +451,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
      </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
+      <entry>One row only, showing statistics about the
+       checkpointer process's activity. See
+       <link linkend="monitoring-pg-stat-checkpointer-view">
+       <structname>pg_stat_checkpointer</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_database</structname><indexterm><primary>pg_stat_database</primary></indexterm></entry>
       <entry>One row per database, showing database-wide statistics. See
@@ -2868,7 +2877,7 @@ description | Waiting for a newly initialized WAL file to reach durable storage
 
   <para>
    The <structname>pg_stat_bgwriter</structname> view will always have a
-   single row, containing global data for the cluster.
+   single row, containing data about the bgwriter of the cluster.
   </para>
 
   <table id="pg-stat-bgwriter-view" xreflabel="pg_stat_bgwriter">
@@ -2888,77 +2897,118 @@ description | Waiting for a newly initialized WAL file to reach durable storage
     <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_timed</structfield> <type>bigint</type>
+       <structfield>buffers_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of scheduled checkpoints that have been performed
+       Number of buffers written by the background writer
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_req</structfield> <type>bigint</type>
+       <structfield>maxwritten_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of requested checkpoints that have been performed
+       Number of times the background writer stopped a cleaning
+       scan because it had written too many buffers
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
+       <structfield>buffers_alloc</structfield> <type>bigint</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are written to disk, in milliseconds
+       Number of buffers allocated
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are synchronized to disk, in
-       milliseconds
+       Time at which these statistics were last reset
       </para></entry>
      </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
+
+ <sect2 id="monitoring-pg-stat-checkpointer-view">
+  <title><structname>pg_stat_checkpointer</structname></title>
 
+  <indexterm>
+   <primary>pg_stat_checkpointer</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_checkpointer</structname> view will always have a
+   single row, containing data about the checkpointer process of the cluster.
+  </para>
+
+  <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
+   <title><structname>pg_stat_checkpointer</structname> View</title>
+   <tgroup cols="1">
+    <thead>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
+       Column Type
       </para>
       <para>
-       Number of buffers written during checkpoints
+       Description
       </para></entry>
      </row>
+    </thead>
 
+    <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_clean</structfield> <type>bigint</type>
+       <structfield>num_timed</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written by the background writer
+       Number of scheduled checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>maxwritten_clean</structfield> <type>bigint</type>
+       <structfield>num_requested</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of times the background writer stopped a cleaning
-       scan because it had written too many buffers
+       Number of requested checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_alloc</structfield> <type>bigint</type>
+       <structfield>write_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of buffers allocated
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are written to disk, in milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>sync_time</structfield> <type>double precision</type>
+      </para>
+      <para>
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are synchronized to disk, in
+       milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_written</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written during checkpoints
       </para></entry>
      </row>
 
@@ -4669,8 +4719,10 @@ description | Waiting for a newly initialized WAL file to reach durable storage
         Resets some cluster-wide statistics counters to zero, depending on the
         argument.  The argument can be <literal>bgwriter</literal> to reset
         all the counters shown in
-        the <structname>pg_stat_bgwriter</structname>
-        view, <literal>archiver</literal> to reset all the counters shown in
+        the <structname>pg_stat_bgwriter</structname> view,
+        <literal>checkpointer</literal> to reset all the counters shown in
+        the <structname>pg_stat_checkpointer</structname> view,
+        <literal>archiver</literal> to reset all the counters shown in
         the <structname>pg_stat_archiver</structname> view,
         <literal>io</literal> to reset all the counters shown in the
         <structname>pg_stat_io</structname> view,
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 40461923ea..b541be8eec 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6349,8 +6349,8 @@ LogCheckpointEnd(bool restartpoint)
 												 CheckpointStats.ckpt_sync_end_t);
 
 	/* Accumulate checkpoint timing summary data, in milliseconds. */
-	PendingCheckpointerStats.checkpoint_write_time += write_msecs;
-	PendingCheckpointerStats.checkpoint_sync_time += sync_msecs;
+	PendingCheckpointerStats.write_time += write_msecs;
+	PendingCheckpointerStats.sync_time += sync_msecs;
 
 	/*
 	 * All of the published timing statistics are accounted for.  Only
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 886f175fc2..b65f6b5249 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1111,16 +1111,20 @@ CREATE VIEW pg_stat_archiver AS
 
 CREATE VIEW pg_stat_bgwriter AS
     SELECT
-        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-        pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-        pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_checkpointer AS
+    SELECT
+        pg_stat_get_checkpointer_num_timed() AS num_timed,
+        pg_stat_get_checkpointer_num_requested() AS num_requested,
+        pg_stat_get_checkpointer_write_time() AS write_time,
+        pg_stat_get_checkpointer_sync_time() AS sync_time,
+        pg_stat_get_checkpointer_buffers_written() AS buffers_written,
+        pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
+
 CREATE VIEW pg_stat_io AS
 SELECT
        b.backend_type,
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 4fe403c9a8..a3c1aba24e 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -358,7 +358,7 @@ CheckpointerMain(void)
 		if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
 		{
 			do_checkpoint = true;
-			PendingCheckpointerStats.requested_checkpoints++;
+			PendingCheckpointerStats.num_requested++;
 		}
 
 		/*
@@ -372,7 +372,7 @@ CheckpointerMain(void)
 		if (elapsed_secs >= CheckPointTimeout)
 		{
 			if (!do_checkpoint)
-				PendingCheckpointerStats.timed_checkpoints++;
+				PendingCheckpointerStats.num_timed++;
 			do_checkpoint = true;
 			flags |= CHECKPOINT_CAUSE_TIME;
 		}
@@ -569,7 +569,7 @@ HandleCheckpointerInterrupts(void)
 		 * updates the statistics, increment the checkpoint request and flush
 		 * out pending statistic.
 		 */
-		PendingCheckpointerStats.requested_checkpoints++;
+		PendingCheckpointerStats.num_requested++;
 		ShutdownXLOG(0, 0);
 		pgstat_report_checkpointer();
 		pgstat_report_wal(true);
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 21a29f9081..dc504a1ae0 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -2751,7 +2751,7 @@ BufferSync(int flags)
 			if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
 			{
 				TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
-				PendingCheckpointerStats.buf_written_checkpoints++;
+				PendingCheckpointerStats.buffers_written++;
 				num_written++;
 			}
 		}
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index 03ed5dddda..301a0bc7bd 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -47,11 +47,11 @@ pgstat_report_checkpointer(void)
 	pgstat_begin_changecount_write(&stats_shmem->changecount);
 
 #define CHECKPOINTER_ACC(fld) stats_shmem->stats.fld += PendingCheckpointerStats.fld
-	CHECKPOINTER_ACC(timed_checkpoints);
-	CHECKPOINTER_ACC(requested_checkpoints);
-	CHECKPOINTER_ACC(checkpoint_write_time);
-	CHECKPOINTER_ACC(checkpoint_sync_time);
-	CHECKPOINTER_ACC(buf_written_checkpoints);
+	CHECKPOINTER_ACC(num_timed);
+	CHECKPOINTER_ACC(num_requested);
+	CHECKPOINTER_ACC(write_time);
+	CHECKPOINTER_ACC(sync_time);
+	CHECKPOINTER_ACC(buffers_written);
 #undef CHECKPOINTER_ACC
 
 	pgstat_end_changecount_write(&stats_shmem->changecount);
@@ -92,6 +92,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
 									&stats_shmem->stats,
 									sizeof(stats_shmem->stats),
 									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
 	LWLockRelease(&stats_shmem->lock);
 }
 
@@ -113,10 +114,10 @@ pgstat_checkpointer_snapshot_cb(void)
 
 	/* compensate by reset offsets */
 #define CHECKPOINTER_COMP(fld) pgStatLocal.snapshot.checkpointer.fld -= reset.fld;
-	CHECKPOINTER_COMP(timed_checkpoints);
-	CHECKPOINTER_COMP(requested_checkpoints);
-	CHECKPOINTER_COMP(checkpoint_write_time);
-	CHECKPOINTER_COMP(checkpoint_sync_time);
-	CHECKPOINTER_COMP(buf_written_checkpoints);
+	CHECKPOINTER_COMP(num_timed);
+	CHECKPOINTER_COMP(num_requested);
+	CHECKPOINTER_COMP(write_time);
+	CHECKPOINTER_COMP(sync_time);
+	CHECKPOINTER_COMP(buffers_written);
 #undef CHECKPOINTER_COMP
 }
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 6468b6a805..2d35dbf31b 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1182,21 +1182,21 @@ PG_STAT_GET_DBENTRY_FLOAT8_MS(idle_in_transaction_time)
 PG_STAT_GET_DBENTRY_FLOAT8_MS(session_time)
 
 Datum
-pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_checkpointer_num_timed(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
+	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->num_timed);
 }
 
 Datum
-pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_checkpointer_num_requested(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
+	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->num_requested);
 }
 
 Datum
-pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_checkpointer_buffers_written(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
+	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buffers_written);
 }
 
 Datum
@@ -1212,19 +1212,25 @@ pg_stat_get_bgwriter_maxwritten_clean(PG_FUNCTION_ARGS)
 }
 
 Datum
-pg_stat_get_checkpoint_write_time(PG_FUNCTION_ARGS)
+pg_stat_get_checkpointer_write_time(PG_FUNCTION_ARGS)
 {
 	/* time is already in msec, just convert to double for presentation */
 	PG_RETURN_FLOAT8((double)
-					 pgstat_fetch_stat_checkpointer()->checkpoint_write_time);
+					 pgstat_fetch_stat_checkpointer()->write_time);
 }
 
 Datum
-pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
+pg_stat_get_checkpointer_sync_time(PG_FUNCTION_ARGS)
 {
 	/* time is already in msec, just convert to double for presentation */
 	PG_RETURN_FLOAT8((double)
-					 pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
+					 pgstat_fetch_stat_checkpointer()->sync_time);
+}
+
+Datum
+pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
 }
 
 Datum
@@ -1738,14 +1744,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 	if (strcmp(target, "archiver") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
 	else if (strcmp(target, "bgwriter") == 0)
-	{
-		/*
-		 * Historically checkpointer was part of bgwriter, continue to reset
-		 * both for now.
-		 */
 		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+	else if (strcmp(target, "checkpointer") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
-	}
 	else if (strcmp(target, "io") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_IO);
 	else if (strcmp(target, "recovery_prefetch") == 0)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index bc41e92677..568aa80d92 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5700,20 +5700,24 @@
   proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}',
   prosrc => 'pg_stat_get_archiver' },
 { oid => '2769',
-  descr => 'statistics: number of timed checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_timed_checkpoints', provolatile => 's',
+  descr => 'statistics: number of timed checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_checkpointer_num_timed', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_timed_checkpoints' },
+  prosrc => 'pg_stat_get_checkpointer_num_timed' },
 { oid => '2770',
-  descr => 'statistics: number of backend requested checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_requested_checkpoints', provolatile => 's',
+  descr => 'statistics: number of backend requested checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_checkpointer_num_requested', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_requested_checkpoints' },
+  prosrc => 'pg_stat_get_checkpointer_num_requested' },
 { oid => '2771',
-  descr => 'statistics: number of buffers written by the bgwriter during checkpoints',
-  proname => 'pg_stat_get_bgwriter_buf_written_checkpoints', provolatile => 's',
+  descr => 'statistics: number of buffers written by the checkpointer',
+  proname => 'pg_stat_get_checkpointer_buffers_written', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_buf_written_checkpoints' },
+  prosrc => 'pg_stat_get_checkpointer_buffers_written' },
+{ oid => '8206', descr => 'statistics: last reset for the checkpointer',
+  proname => 'pg_stat_get_checkpointer_stat_reset_time', provolatile => 's',
+  proparallel => 'r', prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_stat_get_checkpointer_stat_reset_time' },
 { oid => '2772',
   descr => 'statistics: number of buffers written by the bgwriter for cleaning dirty buffers',
   proname => 'pg_stat_get_bgwriter_buf_written_clean', provolatile => 's',
@@ -5730,14 +5734,14 @@
   prosrc => 'pg_stat_get_bgwriter_stat_reset_time' },
 { oid => '3160',
   descr => 'statistics: checkpoint time spent writing buffers to disk, in milliseconds',
-  proname => 'pg_stat_get_checkpoint_write_time', provolatile => 's',
+  proname => 'pg_stat_get_checkpointer_write_time', provolatile => 's',
   proparallel => 'r', prorettype => 'float8', proargtypes => '',
-  prosrc => 'pg_stat_get_checkpoint_write_time' },
+  prosrc => 'pg_stat_get_checkpointer_write_time' },
 { oid => '3161',
   descr => 'statistics: checkpoint time spent synchronizing buffers to disk, in milliseconds',
-  proname => 'pg_stat_get_checkpoint_sync_time', provolatile => 's',
+  proname => 'pg_stat_get_checkpointer_sync_time', provolatile => 's',
   proparallel => 'r', prorettype => 'float8', proargtypes => '',
-  prosrc => 'pg_stat_get_checkpoint_sync_time' },
+  prosrc => 'pg_stat_get_checkpointer_sync_time' },
 { oid => '2859', descr => 'statistics: number of buffer allocations',
   proname => 'pg_stat_get_buf_alloc', provolatile => 's', proparallel => 'r',
   prorettype => 'int8', proargtypes => '', prosrc => 'pg_stat_get_buf_alloc' },
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index e6fd20f1ce..f95d8db0c4 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -260,11 +260,12 @@ typedef struct PgStat_BgWriterStats
 
 typedef struct PgStat_CheckpointerStats
 {
-	PgStat_Counter timed_checkpoints;
-	PgStat_Counter requested_checkpoints;
-	PgStat_Counter checkpoint_write_time;	/* times in milliseconds */
-	PgStat_Counter checkpoint_sync_time;
-	PgStat_Counter buf_written_checkpoints;
+	PgStat_Counter num_timed;
+	PgStat_Counter num_requested;
+	PgStat_Counter write_time;	/* times in milliseconds */
+	PgStat_Counter sync_time;
+	PgStat_Counter buffers_written;
+	TimestampTz stat_reset_timestamp;
 } PgStat_CheckpointerStats;
 
 
diff --git a/src/test/recovery/t/029_stats_restart.pl b/src/test/recovery/t/029_stats_restart.pl
index 742bd57e28..f6368ab1d3 100644
--- a/src/test/recovery/t/029_stats_restart.pl
+++ b/src/test/recovery/t/029_stats_restart.pl
@@ -173,7 +173,7 @@ is($wal_start->{reset}, $wal_restart->{reset},
 
 ## Check that checkpoint stats are reset, WAL stats aren't affected
 
-$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('bgwriter')");
+$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('checkpointer')");
 
 $sect = "post ckpt reset";
 my $ckpt_reset = checkpoint_stats();
@@ -323,9 +323,9 @@ sub checkpoint_stats
 	my %results;
 
 	$results{count} = $node->safe_psql($connect_db,
-		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter");
+		"SELECT num_timed + num_requested FROM pg_stat_checkpointer");
 	$results{reset} = $node->safe_psql($connect_db,
-		"SELECT stats_reset FROM pg_stat_bgwriter");
+		"SELECT stats_reset FROM pg_stat_checkpointer");
 
 	return \%results;
 }
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 798d1610f2..1442c43d9c 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1816,15 +1816,16 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
-pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
-    pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
+pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+pg_stat_checkpointer| SELECT pg_stat_get_checkpointer_num_timed() AS num_timed,
+    pg_stat_get_checkpointer_num_requested() AS num_requested,
+    pg_stat_get_checkpointer_write_time() AS write_time,
+    pg_stat_get_checkpointer_sync_time() AS sync_time,
+    pg_stat_get_checkpointer_buffers_written() AS buffers_written,
+    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT oid AS datid,
     datname,
         CASE
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 94187e59cf..d79a5de009 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -828,8 +828,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
  t
 (1 row)
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT num_requested AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
 CREATE TEMP TABLE test_stats_temp AS SELECT 17;
@@ -839,7 +839,7 @@ DROP TABLE test_stats_temp;
 -- results of the first.
 CHECKPOINT;
 CHECKPOINT;
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT num_requested > :rqst_ckpts_before FROM pg_stat_checkpointer;
  ?column? 
 ----------
  t
@@ -930,6 +930,21 @@ SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 (1 row)
 
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 1e21e55c6d..055b52a90c 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -417,8 +417,8 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
 SELECT pg_stat_force_next_flush();
 SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database());
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT num_requested AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
@@ -432,7 +432,7 @@ DROP TABLE test_stats_temp;
 CHECKPOINT;
 CHECKPOINT;
 
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT num_requested > :rqst_ckpts_before FROM pg_stat_checkpointer;
 SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
 
 -- Test pg_stat_get_backend_idset() and some allied functions.
@@ -470,6 +470,12 @@ SELECT pg_stat_reset_shared('bgwriter');
 SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
 
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
-- 
2.34.1

From d64200c575bf8c9f54bdefad95f84dff5a8381eb Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Fri, 27 Oct 2023 04:42:55 +0000
Subject: [PATCH v10] Introduce a new view for checkpointer related stats

pg_stat_bgwriter view currently reports checkpointer stats as
well. It has been that way so far because historically
checkpointer was part of bgwriter until the commits 806a2ae and
bf405ba separated them out way back in PG 9.2.

It is time for us to separate checkpointer stats to its own view
called pg_stat_checkpointer.

Bump catalog version.

Author: Bharath Rupireddy
Reviewed-by: Bertrand Drouvot, Andres Freund
Discussion: https://www.postgresql.org/message-id/CALj2ACVxX2ii%3D66RypXRweZe2EsBRiPMj0aHfRfHUeXJcC7kHg%40mail.gmail.com
---
 doc/src/sgml/monitoring.sgml                  | 98 ++++++++++++++-----
 src/backend/access/transam/xlog.c             |  4 +-
 src/backend/catalog/system_views.sql          | 14 ++-
 src/backend/postmaster/checkpointer.c         |  6 +-
 src/backend/storage/buffer/bufmgr.c           |  2 +-
 .../utils/activity/pgstat_checkpointer.c      | 21 ++--
 src/backend/utils/adt/pgstatfuncs.c           | 35 +++----
 src/include/catalog/pg_proc.dat               | 30 +++---
 src/include/pgstat.h                          | 11 ++-
 src/test/recovery/t/029_stats_restart.pl      |  6 +-
 src/test/regress/expected/rules.out           | 13 +--
 src/test/regress/expected/stats.out           | 21 +++-
 src/test/regress/sql/stats.sql                | 12 ++-
 13 files changed, 179 insertions(+), 94 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 9fea60b5b2..082267e15f 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -451,6 +451,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
      </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
+      <entry>One row only, showing statistics about the
+       checkpointer process's activity. See
+       <link linkend="monitoring-pg-stat-checkpointer-view">
+       <structname>pg_stat_checkpointer</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_database</structname><indexterm><primary>pg_stat_database</primary></indexterm></entry>
       <entry>One row per database, showing database-wide statistics. See
@@ -2868,7 +2877,7 @@ description | Waiting for a newly initialized WAL file to reach durable storage
 
   <para>
    The <structname>pg_stat_bgwriter</structname> view will always have a
-   single row, containing global data for the cluster.
+   single row, containing data about the background writer of the cluster.
   </para>
 
   <table id="pg-stat-bgwriter-view" xreflabel="pg_stat_bgwriter">
@@ -2888,77 +2897,118 @@ description | Waiting for a newly initialized WAL file to reach durable storage
     <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_timed</structfield> <type>bigint</type>
+       <structfield>buffers_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of scheduled checkpoints that have been performed
+       Number of buffers written by the background writer
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoints_req</structfield> <type>bigint</type>
+       <structfield>maxwritten_clean</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of requested checkpoints that have been performed
+       Number of times the background writer stopped a cleaning
+       scan because it had written too many buffers
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_write_time</structfield> <type>double precision</type>
+       <structfield>buffers_alloc</structfield> <type>bigint</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are written to disk, in milliseconds
+       Number of buffers allocated
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Total amount of time that has been spent in the portion of
-       checkpoint processing where files are synchronized to disk, in
-       milliseconds
+       Time at which these statistics were last reset
       </para></entry>
      </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
+
+ <sect2 id="monitoring-pg-stat-checkpointer-view">
+  <title><structname>pg_stat_checkpointer</structname></title>
 
+  <indexterm>
+   <primary>pg_stat_checkpointer</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_checkpointer</structname> view will always have a
+   single row, containing data about the checkpointer process of the cluster.
+  </para>
+
+  <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
+   <title><structname>pg_stat_checkpointer</structname> View</title>
+   <tgroup cols="1">
+    <thead>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_checkpoint</structfield> <type>bigint</type>
+       Column Type
       </para>
       <para>
-       Number of buffers written during checkpoints
+       Description
       </para></entry>
      </row>
+    </thead>
 
+    <tbody>
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_clean</structfield> <type>bigint</type>
+       <structfield>num_timed</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of buffers written by the background writer
+       Number of scheduled checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>maxwritten_clean</structfield> <type>bigint</type>
+       <structfield>num_requested</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of times the background writer stopped a cleaning
-       scan because it had written too many buffers
+       Number of requested checkpoints that have been performed
       </para></entry>
      </row>
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>buffers_alloc</structfield> <type>bigint</type>
+       <structfield>write_time</structfield> <type>double precision</type>
       </para>
       <para>
-       Number of buffers allocated
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are written to disk, in milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>sync_time</structfield> <type>double precision</type>
+      </para>
+      <para>
+       Total amount of time that has been spent in the portion of
+       checkpoint processing where files are synchronized to disk, in
+       milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>buffers_written</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers written during checkpoints
       </para></entry>
      </row>
 
@@ -4669,8 +4719,10 @@ description | Waiting for a newly initialized WAL file to reach durable storage
         Resets some cluster-wide statistics counters to zero, depending on the
         argument.  The argument can be <literal>bgwriter</literal> to reset
         all the counters shown in
-        the <structname>pg_stat_bgwriter</structname>
-        view, <literal>archiver</literal> to reset all the counters shown in
+        the <structname>pg_stat_bgwriter</structname> view,
+        <literal>checkpointer</literal> to reset all the counters shown in
+        the <structname>pg_stat_checkpointer</structname> view,
+        <literal>archiver</literal> to reset all the counters shown in
         the <structname>pg_stat_archiver</structname> view,
         <literal>io</literal> to reset all the counters shown in the
         <structname>pg_stat_io</structname> view,
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 40461923ea..b541be8eec 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6349,8 +6349,8 @@ LogCheckpointEnd(bool restartpoint)
 												 CheckpointStats.ckpt_sync_end_t);
 
 	/* Accumulate checkpoint timing summary data, in milliseconds. */
-	PendingCheckpointerStats.checkpoint_write_time += write_msecs;
-	PendingCheckpointerStats.checkpoint_sync_time += sync_msecs;
+	PendingCheckpointerStats.write_time += write_msecs;
+	PendingCheckpointerStats.sync_time += sync_msecs;
 
 	/*
 	 * All of the published timing statistics are accounted for.  Only
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 886f175fc2..b65f6b5249 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1111,16 +1111,20 @@ CREATE VIEW pg_stat_archiver AS
 
 CREATE VIEW pg_stat_bgwriter AS
     SELECT
-        pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-        pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-        pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-        pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-        pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
         pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
         pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_checkpointer AS
+    SELECT
+        pg_stat_get_checkpointer_num_timed() AS num_timed,
+        pg_stat_get_checkpointer_num_requested() AS num_requested,
+        pg_stat_get_checkpointer_write_time() AS write_time,
+        pg_stat_get_checkpointer_sync_time() AS sync_time,
+        pg_stat_get_checkpointer_buffers_written() AS buffers_written,
+        pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
+
 CREATE VIEW pg_stat_io AS
 SELECT
        b.backend_type,
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 4fe403c9a8..a3c1aba24e 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -358,7 +358,7 @@ CheckpointerMain(void)
 		if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
 		{
 			do_checkpoint = true;
-			PendingCheckpointerStats.requested_checkpoints++;
+			PendingCheckpointerStats.num_requested++;
 		}
 
 		/*
@@ -372,7 +372,7 @@ CheckpointerMain(void)
 		if (elapsed_secs >= CheckPointTimeout)
 		{
 			if (!do_checkpoint)
-				PendingCheckpointerStats.timed_checkpoints++;
+				PendingCheckpointerStats.num_timed++;
 			do_checkpoint = true;
 			flags |= CHECKPOINT_CAUSE_TIME;
 		}
@@ -569,7 +569,7 @@ HandleCheckpointerInterrupts(void)
 		 * updates the statistics, increment the checkpoint request and flush
 		 * out pending statistic.
 		 */
-		PendingCheckpointerStats.requested_checkpoints++;
+		PendingCheckpointerStats.num_requested++;
 		ShutdownXLOG(0, 0);
 		pgstat_report_checkpointer();
 		pgstat_report_wal(true);
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 21a29f9081..dc504a1ae0 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -2751,7 +2751,7 @@ BufferSync(int flags)
 			if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
 			{
 				TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
-				PendingCheckpointerStats.buf_written_checkpoints++;
+				PendingCheckpointerStats.buffers_written++;
 				num_written++;
 			}
 		}
diff --git a/src/backend/utils/activity/pgstat_checkpointer.c b/src/backend/utils/activity/pgstat_checkpointer.c
index 03ed5dddda..301a0bc7bd 100644
--- a/src/backend/utils/activity/pgstat_checkpointer.c
+++ b/src/backend/utils/activity/pgstat_checkpointer.c
@@ -47,11 +47,11 @@ pgstat_report_checkpointer(void)
 	pgstat_begin_changecount_write(&stats_shmem->changecount);
 
 #define CHECKPOINTER_ACC(fld) stats_shmem->stats.fld += PendingCheckpointerStats.fld
-	CHECKPOINTER_ACC(timed_checkpoints);
-	CHECKPOINTER_ACC(requested_checkpoints);
-	CHECKPOINTER_ACC(checkpoint_write_time);
-	CHECKPOINTER_ACC(checkpoint_sync_time);
-	CHECKPOINTER_ACC(buf_written_checkpoints);
+	CHECKPOINTER_ACC(num_timed);
+	CHECKPOINTER_ACC(num_requested);
+	CHECKPOINTER_ACC(write_time);
+	CHECKPOINTER_ACC(sync_time);
+	CHECKPOINTER_ACC(buffers_written);
 #undef CHECKPOINTER_ACC
 
 	pgstat_end_changecount_write(&stats_shmem->changecount);
@@ -92,6 +92,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
 									&stats_shmem->stats,
 									sizeof(stats_shmem->stats),
 									&stats_shmem->changecount);
+	stats_shmem->stats.stat_reset_timestamp = ts;
 	LWLockRelease(&stats_shmem->lock);
 }
 
@@ -113,10 +114,10 @@ pgstat_checkpointer_snapshot_cb(void)
 
 	/* compensate by reset offsets */
 #define CHECKPOINTER_COMP(fld) pgStatLocal.snapshot.checkpointer.fld -= reset.fld;
-	CHECKPOINTER_COMP(timed_checkpoints);
-	CHECKPOINTER_COMP(requested_checkpoints);
-	CHECKPOINTER_COMP(checkpoint_write_time);
-	CHECKPOINTER_COMP(checkpoint_sync_time);
-	CHECKPOINTER_COMP(buf_written_checkpoints);
+	CHECKPOINTER_COMP(num_timed);
+	CHECKPOINTER_COMP(num_requested);
+	CHECKPOINTER_COMP(write_time);
+	CHECKPOINTER_COMP(sync_time);
+	CHECKPOINTER_COMP(buffers_written);
 #undef CHECKPOINTER_COMP
 }
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 6468b6a805..f3ad1e38f7 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1182,21 +1182,21 @@ PG_STAT_GET_DBENTRY_FLOAT8_MS(idle_in_transaction_time)
 PG_STAT_GET_DBENTRY_FLOAT8_MS(session_time)
 
 Datum
-pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_checkpointer_num_timed(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
+	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->num_timed);
 }
 
 Datum
-pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_checkpointer_num_requested(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
+	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->num_requested);
 }
 
 Datum
-pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
+pg_stat_get_checkpointer_buffers_written(PG_FUNCTION_ARGS)
 {
-	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
+	PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buffers_written);
 }
 
 Datum
@@ -1212,19 +1212,25 @@ pg_stat_get_bgwriter_maxwritten_clean(PG_FUNCTION_ARGS)
 }
 
 Datum
-pg_stat_get_checkpoint_write_time(PG_FUNCTION_ARGS)
+pg_stat_get_checkpointer_write_time(PG_FUNCTION_ARGS)
 {
 	/* time is already in msec, just convert to double for presentation */
 	PG_RETURN_FLOAT8((double)
-					 pgstat_fetch_stat_checkpointer()->checkpoint_write_time);
+					 pgstat_fetch_stat_checkpointer()->write_time);
 }
 
 Datum
-pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
+pg_stat_get_checkpointer_sync_time(PG_FUNCTION_ARGS)
 {
 	/* time is already in msec, just convert to double for presentation */
 	PG_RETURN_FLOAT8((double)
-					 pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
+					 pgstat_fetch_stat_checkpointer()->sync_time);
+}
+
+Datum
+pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
 }
 
 Datum
@@ -1738,14 +1744,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 	if (strcmp(target, "archiver") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
 	else if (strcmp(target, "bgwriter") == 0)
-	{
-		/*
-		 * Historically checkpointer was part of bgwriter, continue to reset
-		 * both for now.
-		 */
 		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+	else if (strcmp(target, "checkpointer") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
-	}
 	else if (strcmp(target, "io") == 0)
 		pgstat_reset_of_kind(PGSTAT_KIND_IO);
 	else if (strcmp(target, "recovery_prefetch") == 0)
@@ -1756,7 +1757,7 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("unrecognized reset target: \"%s\"", target),
-				 errhint("Target must be \"archiver\", \"bgwriter\", \"io\", \"recovery_prefetch\", or \"wal\".")));
+				 errhint("Target must be \"archiver\", \"bgwriter\", \"checkpointer\", \"io\", \"recovery_prefetch\", or \"wal\".")));
 
 	PG_RETURN_VOID();
 }
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index bc41e92677..568aa80d92 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5700,20 +5700,24 @@
   proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}',
   prosrc => 'pg_stat_get_archiver' },
 { oid => '2769',
-  descr => 'statistics: number of timed checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_timed_checkpoints', provolatile => 's',
+  descr => 'statistics: number of timed checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_checkpointer_num_timed', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_timed_checkpoints' },
+  prosrc => 'pg_stat_get_checkpointer_num_timed' },
 { oid => '2770',
-  descr => 'statistics: number of backend requested checkpoints started by the bgwriter',
-  proname => 'pg_stat_get_bgwriter_requested_checkpoints', provolatile => 's',
+  descr => 'statistics: number of backend requested checkpoints started by the checkpointer',
+  proname => 'pg_stat_get_checkpointer_num_requested', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_requested_checkpoints' },
+  prosrc => 'pg_stat_get_checkpointer_num_requested' },
 { oid => '2771',
-  descr => 'statistics: number of buffers written by the bgwriter during checkpoints',
-  proname => 'pg_stat_get_bgwriter_buf_written_checkpoints', provolatile => 's',
+  descr => 'statistics: number of buffers written by the checkpointer',
+  proname => 'pg_stat_get_checkpointer_buffers_written', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => '',
-  prosrc => 'pg_stat_get_bgwriter_buf_written_checkpoints' },
+  prosrc => 'pg_stat_get_checkpointer_buffers_written' },
+{ oid => '8206', descr => 'statistics: last reset for the checkpointer',
+  proname => 'pg_stat_get_checkpointer_stat_reset_time', provolatile => 's',
+  proparallel => 'r', prorettype => 'timestamptz', proargtypes => '',
+  prosrc => 'pg_stat_get_checkpointer_stat_reset_time' },
 { oid => '2772',
   descr => 'statistics: number of buffers written by the bgwriter for cleaning dirty buffers',
   proname => 'pg_stat_get_bgwriter_buf_written_clean', provolatile => 's',
@@ -5730,14 +5734,14 @@
   prosrc => 'pg_stat_get_bgwriter_stat_reset_time' },
 { oid => '3160',
   descr => 'statistics: checkpoint time spent writing buffers to disk, in milliseconds',
-  proname => 'pg_stat_get_checkpoint_write_time', provolatile => 's',
+  proname => 'pg_stat_get_checkpointer_write_time', provolatile => 's',
   proparallel => 'r', prorettype => 'float8', proargtypes => '',
-  prosrc => 'pg_stat_get_checkpoint_write_time' },
+  prosrc => 'pg_stat_get_checkpointer_write_time' },
 { oid => '3161',
   descr => 'statistics: checkpoint time spent synchronizing buffers to disk, in milliseconds',
-  proname => 'pg_stat_get_checkpoint_sync_time', provolatile => 's',
+  proname => 'pg_stat_get_checkpointer_sync_time', provolatile => 's',
   proparallel => 'r', prorettype => 'float8', proargtypes => '',
-  prosrc => 'pg_stat_get_checkpoint_sync_time' },
+  prosrc => 'pg_stat_get_checkpointer_sync_time' },
 { oid => '2859', descr => 'statistics: number of buffer allocations',
   proname => 'pg_stat_get_buf_alloc', provolatile => 's', proparallel => 'r',
   prorettype => 'int8', proargtypes => '', prosrc => 'pg_stat_get_buf_alloc' },
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index e6fd20f1ce..f95d8db0c4 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -260,11 +260,12 @@ typedef struct PgStat_BgWriterStats
 
 typedef struct PgStat_CheckpointerStats
 {
-	PgStat_Counter timed_checkpoints;
-	PgStat_Counter requested_checkpoints;
-	PgStat_Counter checkpoint_write_time;	/* times in milliseconds */
-	PgStat_Counter checkpoint_sync_time;
-	PgStat_Counter buf_written_checkpoints;
+	PgStat_Counter num_timed;
+	PgStat_Counter num_requested;
+	PgStat_Counter write_time;	/* times in milliseconds */
+	PgStat_Counter sync_time;
+	PgStat_Counter buffers_written;
+	TimestampTz stat_reset_timestamp;
 } PgStat_CheckpointerStats;
 
 
diff --git a/src/test/recovery/t/029_stats_restart.pl b/src/test/recovery/t/029_stats_restart.pl
index 742bd57e28..f6368ab1d3 100644
--- a/src/test/recovery/t/029_stats_restart.pl
+++ b/src/test/recovery/t/029_stats_restart.pl
@@ -173,7 +173,7 @@ is($wal_start->{reset}, $wal_restart->{reset},
 
 ## Check that checkpoint stats are reset, WAL stats aren't affected
 
-$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('bgwriter')");
+$node->safe_psql($connect_db, "SELECT pg_stat_reset_shared('checkpointer')");
 
 $sect = "post ckpt reset";
 my $ckpt_reset = checkpoint_stats();
@@ -323,9 +323,9 @@ sub checkpoint_stats
 	my %results;
 
 	$results{count} = $node->safe_psql($connect_db,
-		"SELECT checkpoints_timed + checkpoints_req FROM pg_stat_bgwriter");
+		"SELECT num_timed + num_requested FROM pg_stat_checkpointer");
 	$results{reset} = $node->safe_psql($connect_db,
-		"SELECT stats_reset FROM pg_stat_bgwriter");
+		"SELECT stats_reset FROM pg_stat_checkpointer");
 
 	return \%results;
 }
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 798d1610f2..1442c43d9c 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1816,15 +1816,16 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
-pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
-    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
-    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
-    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
-    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
-    pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
+pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
     pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
+pg_stat_checkpointer| SELECT pg_stat_get_checkpointer_num_timed() AS num_timed,
+    pg_stat_get_checkpointer_num_requested() AS num_requested,
+    pg_stat_get_checkpointer_write_time() AS write_time,
+    pg_stat_get_checkpointer_sync_time() AS sync_time,
+    pg_stat_get_checkpointer_buffers_written() AS buffers_written,
+    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
 pg_stat_database| SELECT oid AS datid,
     datname,
         CASE
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 94187e59cf..d79a5de009 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -828,8 +828,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
  t
 (1 row)
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT num_requested AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
 CREATE TEMP TABLE test_stats_temp AS SELECT 17;
@@ -839,7 +839,7 @@ DROP TABLE test_stats_temp;
 -- results of the first.
 CHECKPOINT;
 CHECKPOINT;
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT num_requested > :rqst_ckpts_before FROM pg_stat_checkpointer;
  ?column? 
 ----------
  t
@@ -930,6 +930,21 @@ SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 (1 row)
 
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 1e21e55c6d..055b52a90c 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -417,8 +417,8 @@ SELECT sessions AS db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
 SELECT pg_stat_force_next_flush();
 SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELECT current_database());
 
--- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
-SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
+-- Test pg_stat_checkpointer checkpointer-related stats, together with pg_stat_wal
+SELECT num_requested AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
 
 -- Test pg_stat_wal (and make a temp table so our temp schema exists)
 SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
@@ -432,7 +432,7 @@ DROP TABLE test_stats_temp;
 CHECKPOINT;
 CHECKPOINT;
 
-SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
+SELECT num_requested > :rqst_ckpts_before FROM pg_stat_checkpointer;
 SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
 
 -- Test pg_stat_get_backend_idset() and some allied functions.
@@ -470,6 +470,12 @@ SELECT pg_stat_reset_shared('bgwriter');
 SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset AS bgwriter_reset_ts FROM pg_stat_bgwriter \gset
 
+-- Test that reset_shared with checkpointer specified as the stats type works
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+SELECT pg_stat_reset_shared('checkpointer');
+SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
+SELECT stats_reset AS checkpointer_reset_ts FROM pg_stat_checkpointer \gset
+
 -- Test that reset_shared with wal specified as the stats type works
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 SELECT pg_stat_reset_shared('wal');
-- 
2.34.1

From d679aa38b5d7e828ac7eef4a239e9da3fbdc0704 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Mon, 30 Oct 2023 05:31:03 +0000
Subject: [PATCH v1] Add error case test for pg_stat_reset_shared with unknown
 stats type

This commit adds an error case test for pg_stat_reset_shared with an
unknown stats type to help with the code coverage a bit.
---
 src/test/regress/expected/stats.out | 4 ++++
 src/test/regress/sql/stats.sql      | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 32ad7f3dcc..53b632dcd3 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -991,6 +991,10 @@ SELECT stats_reset = :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
  t
 (1 row)
 
+-- Test error case for reset_shared with unknown stats type
+SELECT pg_stat_reset_shared('unknown');
+ERROR:  unrecognized reset target: "unknown"
+HINT:  Target must be "archiver", "bgwriter", "checkpointer", "io", "recovery_prefetch", or "wal".
 -- Test that reset works for pg_stat_database
 -- Since pg_stat_database stats_reset starts out as NULL, reset it once first so we have something to compare it to
 SELECT pg_stat_reset();
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 8bfeed607f..febb83add0 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -489,6 +489,9 @@ SELECT stats_reset = :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset = :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
 SELECT stats_reset = :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
 
+-- Test error case for reset_shared with unknown stats type
+SELECT pg_stat_reset_shared('unknown');
+
 -- Test that reset works for pg_stat_database
 
 -- Since pg_stat_database stats_reset starts out as NULL, reset it once first so we have something to compare it to
-- 
2.34.1

From 71bcf31a76e56502086e5b60cfbfba5e9c64cb23 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Mon, 30 Oct 2023 06:27:11 +0000
Subject: [PATCH v1] Add test for resetting recovery_prefetch shared stats

This commit adds test for resetting recovery_prefetch shared stats
to help with the code coverage of XLogPrefetchResetStats().
---
 src/test/regress/expected/stats.out | 21 +++++++++++++++++++++
 src/test/regress/sql/stats.sql      |  7 +++++++
 2 files changed, 28 insertions(+)

diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 53b632dcd3..65997334be 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -960,6 +960,21 @@ SELECT stats_reset > :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
 (1 row)
 
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
+-- Test that reset_shared with recovery_prefetch specified as the stats type works
+SELECT stats_reset AS recovery_prefetch_reset_ts FROM pg_stat_recovery_prefetch \gset
+SELECT pg_stat_reset_shared('recovery_prefetch');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT stats_reset > :'recovery_prefetch_reset_ts'::timestamptz FROM pg_stat_recovery_prefetch;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT stats_reset AS recovery_prefetch_reset_ts FROM pg_stat_recovery_prefetch \gset
 -- Test that reset_shared with no specified stats type doesn't reset anything
 SELECT pg_stat_reset_shared(NULL);
  pg_stat_reset_shared 
@@ -991,6 +1006,12 @@ SELECT stats_reset = :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
  t
 (1 row)
 
+SELECT stats_reset = :'recovery_prefetch_reset_ts'::timestamptz FROM pg_stat_recovery_prefetch;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- Test error case for reset_shared with unknown stats type
 SELECT pg_stat_reset_shared('unknown');
 ERROR:  unrecognized reset target: "unknown"
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index febb83add0..498e32de7a 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -482,12 +482,19 @@ SELECT pg_stat_reset_shared('wal');
 SELECT stats_reset > :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 
+-- Test that reset_shared with recovery_prefetch specified as the stats type works
+SELECT stats_reset AS recovery_prefetch_reset_ts FROM pg_stat_recovery_prefetch \gset
+SELECT pg_stat_reset_shared('recovery_prefetch');
+SELECT stats_reset > :'recovery_prefetch_reset_ts'::timestamptz FROM pg_stat_recovery_prefetch;
+SELECT stats_reset AS recovery_prefetch_reset_ts FROM pg_stat_recovery_prefetch \gset
+
 -- Test that reset_shared with no specified stats type doesn't reset anything
 SELECT pg_stat_reset_shared(NULL);
 SELECT stats_reset = :'archiver_reset_ts'::timestamptz FROM pg_stat_archiver;
 SELECT stats_reset = :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
 SELECT stats_reset = :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
 SELECT stats_reset = :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
+SELECT stats_reset = :'recovery_prefetch_reset_ts'::timestamptz FROM pg_stat_recovery_prefetch;
 
 -- Test error case for reset_shared with unknown stats type
 SELECT pg_stat_reset_shared('unknown');
-- 
2.34.1