Add system view pg_wait_events

This new view, wrapped around a SRF, shows some information known about
wait events, as of:
- Name.
- Type (Activity, I/O, Extension, etc.).
- Description.

All the information retrieved comes from wait_event_names.txt, and the
description is the same as the documentation with filters applied to
remove any XML markups.  This view is useful when joined with
pg_stat_activity to get the description of a wait event reported.

Custom wait events for extensions are included in the view.

Original idea by Yves Colin.

Author: Bertrand Drouvot
Reviewed-by: Kyotaro Horiguchi, Masahiro Ikeda, Tom Lane, Michael
Paquier
Discussion: https://postgr.es/m/0e2ae164-dc89-03c3-cf7f-de86378053ac@gmail.com

3 files changed, 9 insertions, 2 deletions

diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 6996073989a..12fac15ceb2 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 => '250',
+  proretset => 't', provolatile => 'v', prorettype => 'record',
+  proargtypes => '', proallargtypes => '{text,text,text}',
+  proargmodes => '{o,o,o}', proargnames => '{type,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 6de5d937991..c1794786117 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', 'wait_event_funcs_data.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/include/utils/wait_event.h b/src/include/utils/wait_event.h
index 3eebdfad38b..009b03a520a 100644
--- a/src/include/utils/wait_event.h
+++ b/src/include/utils/wait_event.h
@@ -63,6 +63,7 @@ extern void WaitEventExtensionShmemInit(void);
 extern Size WaitEventExtensionShmemSize(void);
 
 extern uint32 WaitEventExtensionNew(const char *wait_event_name);
+extern char **GetWaitEventExtensionNames(int *nwaitevents);
 
 /* ----------
  * pgstat_report_wait_start() -