BUG #16015: information_schema.triggers lack of truncate trigger

The following bug has been logged on the website:

Bug reference: 16015
Logged by: DamionZ Zhao
Email address: zhq651(at)126(dot)com
PostgreSQL version: 11.4
Operating system: linux
Description:

1.create scripts
--base table
CREATE TABLE student (
id int primary key,
name varchar(50)
);
CREATE TABLE score (
studentId int,
studentname varchar(50),
math int
);
--function for triggers
CREATE OR REPLACE FUNCTION student_delete_trigger()RETURNS TRIGGER AS
$$BEGIN DELETE FROM score where studentId = OLD.id; RETURN
OLD;END;$$LANGUAGE plpgsql;

--delete
CREATE TRIGGER delete_trigger AFTER DELETE ON student FOR EACH ROW EXECUTE
PROCEDURE student_delete_trigger();
--update
CREATE TRIGGER delete_trigger_1 BEFORE update ON student FOR EACH ROW
EXECUTE PROCEDURE student_delete_trigger();
--isnert
CREATE TRIGGER insert_trigger after insert ON student FOR EACH ROW EXECUTE
PROCEDURE student_delete_trigger();
--truncate
CREATE TRIGGER truncate_trigger before truncate ON student FOR EACH
STATEMENT EXECUTE PROCEDURE student_delete_trigger();

2. compare
2.1 Let's see pg_trigger below. It is OK. We can see the last record :
[truncate_trigger]

postgres=# select *from pg_trigger where tgrelid=(select oid from pg_class
where relname='student');
tgrelid | tgname | tgfoid | tgtype | tgenabled | tgisinternal |
tgconstrrelid | tgconstrindid | tgconstraint | tgdeferrable | tginitdeferred
| tgnargs | tgattr | tgargs | tgqual | tgoldtable |
tgnewtable
---------+------------------+--------+--------+-----------+--------------+---------------+---------------+--------------+--------------+----------------+---------+--------+--------+--------+------------+
------------
88223 | delete_trigger | 88231 | 9 | O | f |
0 | 0 | 0 | f | f |
0 | | \x | | |

88223 | delete_trigger_1 | 88231 | 19 | O | f |
0 | 0 | 0 | f | f |
0 | | \x | | |

88223 | insert_trigger | 88231 | 5 | O | f |
0 | 0 | 0 | f | f |
0 | | \x | | |

88223 | truncate_trigger | 88231 | 34 | O | f |
0 | 0 | 0 | f | f |
0 | | \x | | |

(4 rows)

2.2 see information_schema.triggers, there is no record of
[truncate_trigger]
postgres=# select *from information_schema.triggers where
event_object_table='student';
trigger_catalog | trigger_schema | trigger_name | event_manipulation |
event_object_catalog | event_object_schema | event_object_table |
action_order | action_condition | action_stateme
nt | action_orientation | action_timing |
action_reference_old_table | action_reference_new_table |
action_reference_old_row | action_reference_new_row | created
-----------------+----------------+------------------+--------------------+----------------------+---------------------+--------------------+--------------+------------------+----------------------------
----------------+--------------------+---------------+----------------------------+----------------------------+--------------------------+--------------------------+---------
postgres | public | insert_trigger | INSERT |
postgres | public | student |
1 | | EXECUTE PROCEDURE student_d
elete_trigger() | ROW | AFTER |
| | |
|
postgres | public | delete_trigger | DELETE |
postgres | public | student |
1 | | EXECUTE PROCEDURE student_d
elete_trigger() | ROW | AFTER |
| | |
|
postgres | public | delete_trigger_1 | UPDATE |
postgres | public | student |
1 | | EXECUTE PROCEDURE student_d
elete_trigger() | ROW | BEFORE |
| | |
|
(3 rows)

3.see implemation of information_schema.triggers

postgres=# \dS+ information_schema.triggers
View
"information_schema.triggers"
Column | Type | Collation
| Nullable | Default | Storage | Description
----------------------------+------------------------------------+-----------+----------+---------+----------+-------------
trigger_catalog | information_schema.sql_identifier |
| | | extended |
trigger_schema | information_schema.sql_identifier |
| | | extended |
trigger_name | information_schema.sql_identifier |
| | | extended |
event_manipulation | information_schema.character_data |
| | | extended |
event_object_catalog | information_schema.sql_identifier |
| | | extended |
event_object_schema | information_schema.sql_identifier |
| | | extended |
event_object_table | information_schema.sql_identifier |
| | | extended |
action_order | information_schema.cardinal_number |
| | | plain |
action_condition | information_schema.character_data |
| | | extended |
action_statement | information_schema.character_data |
| | | extended |
action_orientation | information_schema.character_data |
| | | extended |
action_timing | information_schema.character_data |
| | | extended |
action_reference_old_table | information_schema.sql_identifier |
| | | extended |
action_reference_new_table | information_schema.sql_identifier |
| | | extended |
action_reference_old_row | information_schema.sql_identifier |
| | | extended |
action_reference_new_row | information_schema.sql_identifier |
| | | extended |
created | information_schema.time_stamp |
| | | plain |
View definition:
SELECT current_database()::information_schema.sql_identifier AS
trigger_catalog,
n.nspname::information_schema.sql_identifier AS trigger_schema,
t.tgname::information_schema.sql_identifier AS trigger_name,
em.text::information_schema.character_data AS event_manipulation,
current_database()::information_schema.sql_identifier AS
event_object_catalog,
n.nspname::information_schema.sql_identifier AS event_object_schema,
c.relname::information_schema.sql_identifier AS event_object_table,
rank() OVER (PARTITION BY n.oid, c.oid, em.num, (t.tgtype::integer & 1),
(t.tgtype::integer & 66) ORDER BY
t.tgname)::information_schema.cardinal_number AS action_order,
CASE
WHEN pg_has_role(c.relowner, 'USAGE'::text) THEN
(regexp_match(pg_get_triggerdef(t.oid), '.{35,} WHEN \((.+)\) EXECUTE
PROCEDURE'::text))[1]
ELSE NULL::text
END::information_schema.character_data AS action_condition,
"substring"(pg_get_triggerdef(t.oid),
"position"("substring"(pg_get_triggerdef(t.oid), 48), 'EXECUTE
PROCEDURE'::text) + 47)::information_schema.character_data AS
action_statement,
CASE t.tgtype::integer & 1
WHEN 1 THEN 'ROW'::text
ELSE 'STATEMENT'::text
END::information_schema.character_data AS action_orientation,
CASE t.tgtype::integer & 66
WHEN 2 THEN 'BEFORE'::text
WHEN 64 THEN 'INSTEAD OF'::text
ELSE 'AFTER'::text
END::information_schema.character_data AS action_timing,
t.tgoldtable::information_schema.sql_identifier AS
action_reference_old_table,
t.tgnewtable::information_schema.sql_identifier AS
action_reference_new_table,
NULL::character varying::information_schema.sql_identifier AS
action_reference_old_row,
NULL::character varying::information_schema.sql_identifier AS
action_reference_new_row,
NULL::timestamp with time zone::information_schema.time_stamp AS
created
FROM pg_namespace n,
pg_class c,
pg_trigger t,
( VALUES (4,'INSERT'::text), (8,'DELETE'::text), (16,'UPDATE'::text))
em(num, text)
WHERE n.oid = c.relnamespace AND c.oid = t.tgrelid AND (t.tgtype::integer
& em.num) <> 0 AND NOT t.tgisinternal AND NOT pg_is_other_temp_schema(n.oid)
AND (pg_has_role(c.relowner, 'USAGE'::text) OR has_table_privilege(c.oid,
'INSERT, UPDATE, DELETE, TRUNCATE, REFERENCES, TRIGGER'::text) OR
has_any_column_privilege(c.oid, 'INSERT, UPDATE, REFERENCES'::text));

Look at the line, should "truncate " be here ???
( VALUES (4,'INSERT'::text), (8,'DELETE'::text), (16,'UPDATE'::text))
em(num, text)