V6_0001-Adds-two-parallel-workers-stat-columns-to-pg_stat_da.patch

From f759381fdd2315b9fc3bf7c31f505f80f89a5d90 Mon Sep 17 00:00:00 2001
From: benoit <benoit.lobreau@dalibo.com>
Date: Fri, 11 Oct 2024 17:29:13 +0200
Subject: [PATCH 1/3] Adds two parallel workers stat columns to
 pg_stat_database

* parallel_workers_to_launch
* parallel_workers_launched
---
 doc/src/sgml/monitoring.sgml                  | 18 +++++++++++++
 src/backend/catalog/system_views.sql          |  2 ++
 src/backend/executor/execMain.c               |  6 +++++
 src/backend/utils/activity/pgstat_database.c  | 18 +++++++++++++
 src/backend/utils/adt/pgstatfuncs.c           |  6 +++++
 src/include/catalog/pg_proc.dat               | 10 +++++++
 src/include/pgstat.h                          |  4 +++
 src/test/regress/expected/rules.out           |  2 ++
 src/test/regress/expected/select_parallel.out | 26 +++++++++++++++++++
 src/test/regress/sql/select_parallel.sql      | 13 ++++++++++
 10 files changed, 105 insertions(+)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 331315f8d3..840d7f8161 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3611,6 +3611,24 @@ 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>parallel_workers_to_launch</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of parallel workers planned to be launched by queries on this database
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>parallel_workers_launched</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of parallel workers launched by queries on this database
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 3456b821bc..da9a8fe99f 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1073,6 +1073,8 @@ CREATE VIEW pg_stat_database AS
             pg_stat_get_db_sessions_abandoned(D.oid) AS sessions_abandoned,
             pg_stat_get_db_sessions_fatal(D.oid) AS sessions_fatal,
             pg_stat_get_db_sessions_killed(D.oid) AS sessions_killed,
+            pg_stat_get_db_parallel_workers_to_launch(D.oid) as parallel_workers_to_launch,
+            pg_stat_get_db_parallel_workers_launched(D.oid) as parallel_workers_launched,
             pg_stat_get_db_stat_reset_time(D.oid) AS stats_reset
     FROM (
         SELECT 0 AS oid, NULL::name AS datname
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index cc9a594cba..e3da94cb10 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -52,6 +52,7 @@
 #include "miscadmin.h"
 #include "nodes/queryjumble.h"
 #include "parser/parse_relation.h"
+#include "pgstat.h"
 #include "rewrite/rewriteHandler.h"
 #include "tcop/utility.h"
 #include "utils/acl.h"
@@ -483,6 +484,11 @@ standard_ExecutorEnd(QueryDesc *queryDesc)
 
 	Assert(estate != NULL);
 
+	if (estate->es_parallel_workers_to_launch > 0)
+		pgstat_update_parallel_workers_stats(
+			(PgStat_Counter) estate->es_parallel_workers_to_launch,
+			(PgStat_Counter) estate->es_parallel_workers_launched);
+
 	/*
 	 * Check that ExecutorFinish was called, unless in EXPLAIN-only mode. This
 	 * Assert is needed because ExecutorFinish is new as of 9.1, and callers
diff --git a/src/backend/utils/activity/pgstat_database.c b/src/backend/utils/activity/pgstat_database.c
index 29bc090974..efa3d51408 100644
--- a/src/backend/utils/activity/pgstat_database.c
+++ b/src/backend/utils/activity/pgstat_database.c
@@ -262,6 +262,22 @@ AtEOXact_PgStat_Database(bool isCommit, bool parallel)
 	}
 }
 
+/*
+ * reports parallel_workers_to_launch and parallel_workers_launched into
+ * PgStat_StatDBEntry
+ */
+void
+pgstat_update_parallel_workers_stats(PgStat_Counter parallel_workers_to_launch, PgStat_Counter parallel_workers_launched)
+{
+	PgStat_StatDBEntry *dbentry;
+	if (!OidIsValid(MyDatabaseId))
+		return;
+
+	dbentry = pgstat_prep_database_pending(MyDatabaseId);
+	dbentry->parallel_workers_to_launch += parallel_workers_to_launch;
+	dbentry->parallel_workers_launched += parallel_workers_launched;
+}
+
 /*
  * Subroutine for pgstat_report_stat(): Handle xact commit/rollback and I/O
  * timings.
@@ -425,6 +441,8 @@ pgstat_database_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 	PGSTAT_ACCUM_DBCOUNT(sessions_abandoned);
 	PGSTAT_ACCUM_DBCOUNT(sessions_fatal);
 	PGSTAT_ACCUM_DBCOUNT(sessions_killed);
+	PGSTAT_ACCUM_DBCOUNT(parallel_workers_to_launch);
+	PGSTAT_ACCUM_DBCOUNT(parallel_workers_launched);
 #undef PGSTAT_ACCUM_DBCOUNT
 
 	pgstat_unlock_entry(entry_ref);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index f7b50e0b5a..054c416ab4 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1039,6 +1039,12 @@ PG_STAT_GET_DBENTRY_INT64(sessions_fatal)
 /* pg_stat_get_db_sessions_killed */
 PG_STAT_GET_DBENTRY_INT64(sessions_killed)
 
+/* pg_stat_get_db_parallel_workers_to_launch*/
+PG_STAT_GET_DBENTRY_INT64(parallel_workers_to_launch)
+
+/* pg_stat_get_db_parallel_workers_launched*/
+PG_STAT_GET_DBENTRY_INT64(parallel_workers_launched)
+
 /* pg_stat_get_db_temp_bytes */
 PG_STAT_GET_DBENTRY_INT64(temp_bytes)
 
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 8876bebde0..fe05b279f2 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5810,6 +5810,16 @@
   proname => 'pg_stat_get_db_sessions_killed', provolatile => 's',
   proparallel => 'r', prorettype => 'int8', proargtypes => 'oid',
   prosrc => 'pg_stat_get_db_sessions_killed' },
+{ oid => '8403',
+  descr => 'statistics: number of parallel workers planned to be launched for queries',
+  proname => 'pg_stat_get_db_parallel_workers_to_launch', provolatile => 's',
+  proparallel => 'r', prorettype => 'int8', proargtypes => 'oid',
+  prosrc => 'pg_stat_get_db_parallel_workers_to_launch' },
+{ oid => '8404',
+  descr => 'statistics: number of parallel workers effectively launched for queries',
+  proname => 'pg_stat_get_db_parallel_workers_launched', provolatile => 's',
+  proparallel => 'r', prorettype => 'int8', proargtypes => 'oid',
+  prosrc => 'pg_stat_get_db_parallel_workers_launched' },
 { oid => '3195', descr => 'statistics: information about WAL archiver',
   proname => 'pg_stat_get_archiver', proisstrict => 'f', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index df53fa2d4f..cfba5615a7 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -387,6 +387,9 @@ typedef struct PgStat_StatDBEntry
 	PgStat_Counter sessions_fatal;
 	PgStat_Counter sessions_killed;
 
+	PgStat_Counter parallel_workers_to_launch;
+	PgStat_Counter parallel_workers_launched;
+
 	TimestampTz stat_reset_timestamp;
 } PgStat_StatDBEntry;
 
@@ -583,6 +586,7 @@ extern void pgstat_report_deadlock(void);
 extern void pgstat_report_checksum_failures_in_db(Oid dboid, int failurecount);
 extern void pgstat_report_checksum_failure(void);
 extern void pgstat_report_connect(Oid dboid);
+extern void pgstat_update_parallel_workers_stats(PgStat_Counter parallel_workers_to_launch, PgStat_Counter parallel_workers_launched);
 
 #define pgstat_count_buffer_read_time(n)							\
 	(pgStatBlockReadTime += (n))
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2b47013f11..3014d047fe 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1863,6 +1863,8 @@ pg_stat_database| SELECT oid AS datid,
     pg_stat_get_db_sessions_abandoned(oid) AS sessions_abandoned,
     pg_stat_get_db_sessions_fatal(oid) AS sessions_fatal,
     pg_stat_get_db_sessions_killed(oid) AS sessions_killed,
+    pg_stat_get_db_parallel_workers_to_launch(oid) AS parallel_workers_to_launch,
+    pg_stat_get_db_parallel_workers_launched(oid) AS parallel_workers_launched,
     pg_stat_get_db_stat_reset_time(oid) AS stats_reset
    FROM ( SELECT 0 AS oid,
             NULL::name AS datname
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index d17ade278b..d1bb0bd61a 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -1,6 +1,17 @@
 --
 -- PARALLEL
 --
+-- Get a reference for parallel stats in pg_stat_database
+select pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+select parallel_workers_to_launch as parallel_workers_to_launch_before,
+       parallel_workers_launched as parallel_workers_launched_before
+from pg_stat_database
+where datname = 'regression' \gset
 create function sp_parallel_restricted(int) returns int as
   $$begin return $1; end$$ language plpgsql parallel restricted;
 begin;
@@ -1407,3 +1418,18 @@ CREATE UNIQUE INDEX parallel_hang_idx
 SET debug_parallel_query = on;
 DELETE FROM parallel_hang WHERE 380 <= i AND i <= 420;
 ROLLBACK;
+select pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+select parallel_workers_to_launch > :'parallel_workers_to_launch_before'  AS wrk_to_launch,
+       parallel_workers_launched > :'parallel_workers_launched_before' AS wrk_launched
+from pg_stat_database
+where datname = 'regression';
+ wrk_to_launch | wrk_launched 
+---------------+--------------
+ t             | t
+(1 row)
+
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 9ba1328fd2..5da7d6bcc8 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -2,6 +2,13 @@
 -- PARALLEL
 --
 
+-- Get a reference for parallel stats in pg_stat_database
+select pg_stat_force_next_flush();
+select parallel_workers_to_launch as parallel_workers_to_launch_before,
+       parallel_workers_launched as parallel_workers_launched_before
+from pg_stat_database
+where datname = 'regression' \gset
+
 create function sp_parallel_restricted(int) returns int as
   $$begin return $1; end$$ language plpgsql parallel restricted;
 
@@ -574,3 +581,9 @@ SET debug_parallel_query = on;
 DELETE FROM parallel_hang WHERE 380 <= i AND i <= 420;
 
 ROLLBACK;
+
+select pg_stat_force_next_flush();
+select parallel_workers_to_launch > :'parallel_workers_to_launch_before'  AS wrk_to_launch,
+       parallel_workers_launched > :'parallel_workers_launched_before' AS wrk_launched
+from pg_stat_database
+where datname = 'regression';
-- 
2.46.2