v2-0001-pg_wait_event.patch

From 63f1316b2c160b72bdc1bcff6272e2888fce0db4 Mon Sep 17 00:00:00 2001
From: bdrouvotAWS <bdrouvot@amazon.com>
Date: Sat, 5 Aug 2023 12:39:42 +0000
Subject: [PATCH v2] pg_wait_event

Adding a new system view, namely pg_wait_event, that describes the wait events.
---
 doc/src/sgml/system-views.sgml                | 55 ++++++++++++++
 src/backend/catalog/system_views.sql          |  3 +
 src/backend/utils/activity/.gitignore         |  1 +
 src/backend/utils/activity/Makefile           |  6 +-
 .../activity/generate-wait_event_types.pl     | 76 +++++++++++++------
 src/backend/utils/activity/meson.build        |  1 +
 src/backend/utils/activity/pg_wait_event.c    | 41 ++++++++++
 src/include/catalog/pg_proc.dat               |  6 ++
 src/include/utils/meson.build                 |  4 +-
 src/test/regress/expected/rules.out           |  3 +
 src/test/regress/expected/sysviews.out        |  8 ++
 src/test/regress/sql/sysviews.sql             |  4 +
 src/tools/msvc/clean.bat                      |  1 +
 13 files changed, 183 insertions(+), 26 deletions(-)
  19.8% doc/src/sgml/
  60.6% src/backend/utils/activity/
   5.3% src/include/catalog/
   5.7% src/test/regress/expected/
   3.0% src/test/regress/sql/
   5.3% src/

diff --git a/doc/src/sgml/system-views.sgml b/doc/src/sgml/system-views.sgml
index 57b228076e..e9cbeff682 100644
--- a/doc/src/sgml/system-views.sgml
+++ b/doc/src/sgml/system-views.sgml
@@ -221,6 +221,11 @@
       <entry>views</entry>
      </row>
 
+     <row>
+      <entry><link linkend="view-pg-wait-event"><structname>pg_wait_event</structname></link></entry>
+      <entry>wait events</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -4825,4 +4830,54 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
   </table>
  </sect1>
 
+
+ <sect1 id="view-pg-wait-event">
+  <title><structname>pg_wait_event</structname></title>
+
+  <indexterm zone="view-pg-wait-event">
+   <primary>pg_wait_event</primary>
+  </indexterm>
+
+  <para>
+   The view <structname>pg_wait_event</structname> provides description about the
+   wait events.
+  </para>
+
+  <table>
+   <title><structname>pg_wait_event</structname> Columns</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>wait_event_name</structfield> <type>text</type>
+      </para>
+      <para>
+       Wait event name
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>description</structfield> <type>texte</type>
+      </para>
+      <para>
+       Wait event description
+      </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+ </sect1>
+
 </chapter>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index af65af6bdd..f86a4dd770 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1342,3 +1342,6 @@ CREATE VIEW pg_stat_subscription_stats AS
         ss.stats_reset
     FROM pg_subscription as s,
          pg_stat_get_subscription_stats(s.oid) as ss;
+
+CREATE VIEW pg_wait_event AS
+    SELECT * FROM pg_get_wait_events() AS we;
diff --git a/src/backend/utils/activity/.gitignore b/src/backend/utils/activity/.gitignore
index d77079285b..ad089a0b63 100644
--- a/src/backend/utils/activity/.gitignore
+++ b/src/backend/utils/activity/.gitignore
@@ -1,2 +1,3 @@
 /pgstat_wait_event.c
 /wait_event_types.h
+/pg_wait_event_insert.c
diff --git a/src/backend/utils/activity/Makefile b/src/backend/utils/activity/Makefile
index f1117745d4..8595e6ea77 100644
--- a/src/backend/utils/activity/Makefile
+++ b/src/backend/utils/activity/Makefile
@@ -32,10 +32,14 @@ OBJS = \
 	pgstat_subscription.o \
 	pgstat_wal.o \
 	pgstat_xact.o \
+	pg_wait_event.o \
 	wait_event.o
 
 include $(top_srcdir)/src/backend/common.mk
 
+pg_wait_event.o: pg_wait_event_insert.c
+pg_wait_event_insert.c: wait_event_types.h
+
 wait_event.o: pgstat_wait_event.c
 pgstat_wait_event.c: wait_event_types.h
 	touch $@
@@ -44,4 +48,4 @@ wait_event_types.h: $(top_srcdir)/src/backend/utils/activity/wait_event_names.tx
 	$(PERL) $(srcdir)/generate-wait_event_types.pl --code $<
 
 maintainer-clean: clean
-	rm -f wait_event_types.h pgstat_wait_event.c
+	rm -f wait_event_types.h pgstat_wait_event.c pg_wait_event_insert.c
diff --git a/src/backend/utils/activity/generate-wait_event_types.pl b/src/backend/utils/activity/generate-wait_event_types.pl
index 56335e8730..6f2b823b6b 100644
--- a/src/backend/utils/activity/generate-wait_event_types.pl
+++ b/src/backend/utils/activity/generate-wait_event_types.pl
@@ -4,6 +4,7 @@
 # Generate wait events support files from wait_event_names.txt:
 # - wait_event_types.h (if --code is passed)
 # - pgstat_wait_event.c (if --code is passed)
+# - pg_wait_event_insert.c (if --code is passed)
 # - wait_event_types.sgml (if --docs is passed)
 #
 # Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
@@ -98,8 +99,10 @@ if ($gen_code)
 	# multiple times.
 	my $htmp = "$output_path/wait_event_types.h.tmp$$";
 	my $ctmp = "$output_path/pgstat_wait_event.c.tmp$$";
+	my $ictmp = "$output_path/pg_wait_event_insert.c.tmp$$";
 	open my $h, '>', $htmp or die "Could not open $htmp: $!";
 	open my $c, '>', $ctmp or die "Could not open $ctmp: $!";
+	open my $ic, '>', $ictmp or die "Could not open $ictmp: $!";
 
 	my $header_comment =
 	  '/*-------------------------------------------------------------------------
@@ -129,16 +132,17 @@ if ($gen_code)
 
 	printf $c $header_comment, 'pgstat_wait_event.c';
 
+	printf $ic $header_comment, 'pg_wait_event_insert.c';
+
 	# uc() is being used to force the comparison to be case-insensitive.
 	foreach my $waitclass (sort { uc($a) cmp uc($b) } keys %hashwe)
 	{
 
-		# Don't generate .c and .h files for Extension, LWLock and
-		# Lock, these are handled independently.
-		next
-		  if ( $waitclass eq 'WaitEventExtension'
-			|| $waitclass eq 'WaitEventLWLock'
-			|| $waitclass eq 'WaitEventLock');
+		# Don't generate .c (except pg_wait_event_insert.c) and .h files for
+		# Extension, LWLock and Lock, these are handled independently.
+		my $is_exception = $waitclass eq 'WaitEventExtension' ||
+						   $waitclass eq 'WaitEventLWLock' ||
+						   $waitclass eq 'WaitEventLock';
 
 		my $last = $waitclass;
 		$last =~ s/^WaitEvent//;
@@ -147,50 +151,76 @@ if ($gen_code)
 		my $firstpass = 1;
 		my $pg_wait_class;
 
-		printf $c
-		  "static const char *\npgstat_get_wait_$lastlc($waitclass w)\n{\n";
-		printf $c "\tconst char *event_name = \"unknown wait event\";\n\n";
-		printf $c "\tswitch (w)\n\t{\n";
+		if (!$is_exception)
+		{
+			printf $c
+			  "static const char *\npgstat_get_wait_$lastlc($waitclass w)\n{\n";
+			printf $c "\tconst char *event_name = \"unknown wait event\";\n\n";
+			printf $c "\tswitch (w)\n\t{\n";
+		}
 
 		foreach my $wev (@{ $hashwe{$waitclass} })
 		{
-			if ($firstpass)
+			if ($firstpass && !$is_exception)
 			{
 				printf $h "typedef enum\n{\n";
 				$pg_wait_class = "PG_WAIT_" . $lastuc;
 				printf $h "\t%s = %s", $wev->[0], $pg_wait_class;
 				$continue = ",\n";
 			}
-			else
+			elsif (!$is_exception)
 			{
 				printf $h "%s\t%s", $continue, $wev->[0];
 				$continue = ",\n";
 			}
-			$firstpass = 0;
 
-			printf $c "\t\t case %s:\n", $wev->[0];
-			# Apply quotes to the wait event name string.
-			printf $c "\t\t\t event_name = \"%s\";\n\t\t\t break;\n",
-			  $wev->[1];
+			if (!$is_exception)
+			{
+				$firstpass = 0;
+
+				printf $c "\t\t case %s:\n", $wev->[0];
+				# Apply quotes to the wait event name string.
+				printf $c "\t\t\t event_name = \"%s\";\n\t\t\t break;\n",
+				$wev->[1];
+			}
+
+			my $new_desc = substr $wev->[2], 1, -2;
+			$new_desc =~ s/'/\\'/g;
+			$new_desc =~ s/<.*>(.*?)<.*>/$1/g;
+			$new_desc =~ s/<xref linkend="guc-(.*?)"\/>/$1/g;
+			$new_desc =~ s/; see.*$//;
+
+			printf $ic "\tmemset(values, 0, sizeof(values));\n";
+			printf $ic "\tmemset(nulls, 0, sizeof(nulls));\n\n";
+			printf $ic "\tvalues[0] = CStringGetTextDatum(\"%s\");\n", $wev->[1];
+			printf $ic "\tvalues[1] = CStringGetTextDatum(\"%s\");\n\n", $new_desc;
+
+			printf $ic "\ttuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);\n\n";
 		}
 
-		printf $h "\n} $waitclass;\n\n";
+		if (!$is_exception)
+		{
+			printf $h "\n} $waitclass;\n\n";
 
-		printf $c
-		  "\t\t\t /* no default case, so that compiler will warn */\n";
-		printf $c "\t}\n\n";
-		printf $c "\treturn event_name;\n";
-		printf $c "}\n\n";
+			printf $c
+			  "\t\t\t /* no default case, so that compiler will warn */\n";
+			printf $c "\t}\n\n";
+			printf $c "\treturn event_name;\n";
+			printf $c "}\n\n";
+		}
 	}
 
 	printf $h "#endif                          /* WAIT_EVENT_TYPES_H */\n";
 	close $h;
 	close $c;
+	close $ic;
 
 	rename($htmp, "$output_path/wait_event_types.h")
 	  || die "rename: $htmp to $output_path/wait_event_types.h: $!";
 	rename($ctmp, "$output_path/pgstat_wait_event.c")
 	  || die "rename: $ctmp to $output_path/pgstat_wait_event.c: $!";
+	rename($ictmp, "$output_path/pg_wait_event_insert.c")
+	  || die "rename: $ictmp to $output_path/pg_wait_event_insert.c: $!";
 }
 # Generate the .sgml file.
 elsif ($gen_docs)
diff --git a/src/backend/utils/activity/meson.build b/src/backend/utils/activity/meson.build
index 9633f3623c..774e0bd348 100644
--- a/src/backend/utils/activity/meson.build
+++ b/src/backend/utils/activity/meson.build
@@ -23,6 +23,7 @@ backend_sources += files(
 # seems nicer to not add that as an include path for the whole backend.
 waitevent_sources = files(
   'wait_event.c',
+  'pg_wait_event.c',
 )
 
 wait_event = static_library('wait_event_names',
diff --git a/src/backend/utils/activity/pg_wait_event.c b/src/backend/utils/activity/pg_wait_event.c
new file mode 100644
index 0000000000..9407d18254
--- /dev/null
+++ b/src/backend/utils/activity/pg_wait_event.c
@@ -0,0 +1,41 @@
+/* ----------
+ * pg_wait_event.c
+ *    Wait event reporting infrastructure.
+ *
+ * Copyright (c) 2001-2023, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *    src/backend/utils/activity/pg_wait_event.c
+ *
+ * NOTES
+ *
+ * The "pg_wait_event_insert.c" included in this file is generated by
+ *                    src/backend/utils/activity/generate-wait_event_types.pl
+ *
+ */
+#include "postgres.h"
+
+#include "funcapi.h"
+#include "utils/builtins.h"
+
+/*
+ * This function lists the wait events and their descriptions.
+ *
+ * The system view pg_wait_event provides a user interface to this
+ * SRF.
+ */
+Datum
+pg_get_wait_events(PG_FUNCTION_ARGS)
+{
+#define NUM_WAIT_EVENT_TABLES_ELEM 2
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	Datum       values[NUM_WAIT_EVENT_TABLES_ELEM];
+	bool        nulls[NUM_WAIT_EVENT_TABLES_ELEM];
+
+	/* Build tuplestore to hold the result rows */
+	InitMaterializedSRF(fcinfo, 0);
+
+	#include "pg_wait_event_insert.c"
+	return (Datum) 0;
+}
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 6996073989..57d8875dee 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5417,6 +5417,12 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '8403', descr => 'describe wait events',
+  proname => 'pg_get_wait_events', procost => '10', prorows => '100',
+  proretset => 't', provolatile => 's', prorettype => 'record',
+  proargtypes => '', proallargtypes => '{text,text}',
+  proargmodes => '{o,o}', proargnames => '{wait_event_name,description}',
+  prosrc => 'pg_get_wait_events' },
 { oid => '3318',
   descr => 'statistics: information about progress of backends running maintenance command',
   proname => 'pg_stat_get_progress_info', prorows => '100', proretset => 't',
diff --git a/src/include/utils/meson.build b/src/include/utils/meson.build
index 6de5d93799..4f14f770ef 100644
--- a/src/include/utils/meson.build
+++ b/src/include/utils/meson.build
@@ -1,6 +1,6 @@
 # Copyright (c) 2022-2023, PostgreSQL Global Development Group
 
-wait_event_output = ['wait_event_types.h', 'pgstat_wait_event.c']
+wait_event_output = ['wait_event_types.h', 'pgstat_wait_event.c', 'pg_wait_event_insert.c']
 wait_event_target = custom_target('wait_event_names',
   input: files('../../backend/utils/activity/wait_event_names.txt'),
   output: wait_event_output,
@@ -11,7 +11,7 @@ wait_event_target = custom_target('wait_event_names',
   ],
   build_by_default: true,
   install: true,
-  install_dir: [dir_include_server / 'utils', false],
+  install_dir: [dir_include_server / 'utils', false, false],
 )
 
 wait_event_types_h = wait_event_target[0]
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index e07afcd4aa..23b5f7dbca 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2631,6 +2631,9 @@ pg_views| SELECT n.nspname AS schemaname,
    FROM (pg_class c
      LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace)))
   WHERE (c.relkind = 'v'::"char");
+pg_wait_event| SELECT wait_event_name,
+    description
+   FROM pg_get_wait_events() we(wait_event_name, description);
 SELECT tablename, rulename, definition FROM pg_rules
 WHERE schemaname = 'pg_catalog'
 ORDER BY tablename, rulename;
diff --git a/src/test/regress/expected/sysviews.out b/src/test/regress/expected/sysviews.out
index 001c6e7eb9..12309be267 100644
--- a/src/test/regress/expected/sysviews.out
+++ b/src/test/regress/expected/sysviews.out
@@ -134,6 +134,14 @@ select name, setting from pg_settings where name like 'enable%';
  enable_tidscan                 | on
 (21 rows)
 
+-- There will surely be at least 240 wait events and at least 27 related to WAL
+select count(*) > 239 as ok, count(*) FILTER (WHERE description like '%WAL%') > 26 AS ok_wal_desc
+  from pg_wait_event;
+ ok | ok_wal_desc 
+----+-------------
+ t  | t
+(1 row)
+
 -- Test that the pg_timezone_names and pg_timezone_abbrevs views are
 -- more-or-less working.  We can't test their contents in any great detail
 -- without the outputs changing anytime IANA updates the underlying data,
diff --git a/src/test/regress/sql/sysviews.sql b/src/test/regress/sql/sysviews.sql
index 351e469c77..6bc6bd1322 100644
--- a/src/test/regress/sql/sysviews.sql
+++ b/src/test/regress/sql/sysviews.sql
@@ -55,6 +55,10 @@ select count(*) = 0 as ok from pg_stat_wal_receiver;
 -- a regression test run.
 select name, setting from pg_settings where name like 'enable%';
 
+-- There will surely be at least 240 wait events and at least 27 related to WAL
+select count(*) > 239 as ok, count(*) FILTER (WHERE description like '%WAL%') > 26 AS ok_wal_desc
+  from pg_wait_event;
+
 -- Test that the pg_timezone_names and pg_timezone_abbrevs views are
 -- more-or-less working.  We can't test their contents in any great detail
 -- without the outputs changing anytime IANA updates the underlying data,
diff --git a/src/tools/msvc/clean.bat b/src/tools/msvc/clean.bat
index 7cb23ea894..028d174d87 100755
--- a/src/tools/msvc/clean.bat
+++ b/src/tools/msvc/clean.bat
@@ -55,6 +55,7 @@ if exist src\include\catalog\header-stamp del /q src\include\catalog\header-stam
 if exist doc\src\sgml\version.sgml del /q doc\src\sgml\version.sgml
 
 if %DIST%==1 if exist src\backend\utils\activity\pgstat_wait_event.c del /q src\backend\utils\activity\pgstat_wait_event.c
+if %DIST%==1 if exist src\backend\utils\activity\pg_wait_event_insert.c del /q src\backend\utils\activity\pg_wait_event_insert.c
 if %DIST%==1 if exist src\backend\utils\activity\wait_event_types.h del /q src\backend\utils\activity\wait_event_types.h
 if %DIST%==1 if exist src\backend\utils\fmgroids.h del /q src\backend\utils\fmgroids.h
 if %DIST%==1 if exist src\backend\utils\fmgrprotos.h del /q src\backend\utils\fmgrprotos.h
-- 
2.34.1