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

4 files changed, 30 insertions, 0 deletions

diff --git a/src/test/modules/worker_spi/t/001_worker_spi.pl b/src/test/modules/worker_spi/t/001_worker_spi.pl
index 26b8a49beca..2965acd7890 100644
--- a/src/test/modules/worker_spi/t/001_worker_spi.pl
+++ b/src/test/modules/worker_spi/t/001_worker_spi.pl
@@ -47,6 +47,12 @@ $result = $node->poll_query_until(
 is($result, 1,
 	'dynamic bgworker has reported "worker_spi_main" as wait event');
 
+# Check the wait event used by the dynamic bgworker appears in pg_wait_events
+$result = $node->safe_psql('postgres',
+	q[SELECT count(*) > 0 from pg_wait_events where type = 'Extension' and name = 'worker_spi_main';]
+);
+is($result, 't', '"worker_spi_main" is reported in pg_wait_events');
+
 note "testing bgworkers loaded with shared_preload_libraries";
 
 # Create the database first so as the workers can connect to it when
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index e07afcd4aa6..5058be5411a 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2631,6 +2631,10 @@ 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_events| SELECT type,
+    name,
+    description
+   FROM pg_get_wait_events() pg_get_wait_events(type, 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 001c6e7eb9d..aae5d51e1c9 100644
--- a/src/test/regress/expected/sysviews.out
+++ b/src/test/regress/expected/sysviews.out
@@ -134,6 +134,22 @@ select name, setting from pg_settings where name like 'enable%';
  enable_tidscan                 | on
 (21 rows)
 
+-- There are always wait event descriptions for various types.
+select type, count(*) > 0 as ok FROM pg_wait_events
+  group by type order by type COLLATE "C";
+   type    | ok 
+-----------+----
+ Activity  | t
+ BufferPin | t
+ Client    | t
+ Extension | t
+ IO        | t
+ IPC       | t
+ LWLock    | t
+ Lock      | t
+ Timeout   | t
+(9 rows)
+
 -- 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 351e469c77b..6b4e24601d9 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 are always wait event descriptions for various types.
+select type, count(*) > 0 as ok FROM pg_wait_events
+  group by type order by type COLLATE "C";
+
 -- 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,