CREATE_EVENT_TRIGGER(7)

1CREATE EVENT TRIGGER(7)  PostgreSQL 13.3 Documentation CREATE EVENT TRIGGER(7)
2
3
4

NAME

6       CREATE_EVENT_TRIGGER - define a new event trigger
7

SYNOPSIS

9       CREATE EVENT TRIGGER name
10           ON event
11           [ WHEN filter_variable IN (filter_value [, ... ]) [ AND ... ] ]
12           EXECUTE { FUNCTION | PROCEDURE } function_name()
13

DESCRIPTION

15       CREATE EVENT TRIGGER creates a new event trigger. Whenever the
16       designated event occurs and the WHEN condition associated with the
17       trigger, if any, is satisfied, the trigger function will be executed.
18       For a general introduction to event triggers, see Chapter 39. The user
19       who creates an event trigger becomes its owner.
20

PARAMETERS

22       name
23           The name to give the new trigger. This name must be unique within
24           the database.
25
26       event
27           The name of the event that triggers a call to the given function.
28           See Section 39.1 for more information on event names.
29
30       filter_variable
31           The name of a variable used to filter events. This makes it
32           possible to restrict the firing of the trigger to a subset of the
33           cases in which it is supported. Currently the only supported
34           filter_variable is TAG.
35
36       filter_value
37           A list of values for the associated filter_variable for which the
38           trigger should fire. For TAG, this means a list of command tags
39           (e.g., 'DROP FUNCTION').
40
41       function_name
42           A user-supplied function that is declared as taking no argument and
43           returning type event_trigger.
44
45           In the syntax of CREATE EVENT TRIGGER, the keywords FUNCTION and
46           PROCEDURE are equivalent, but the referenced function must in any
47           case be a function, not a procedure. The use of the keyword
48           PROCEDURE here is historical and deprecated.
49

NOTES

51       Only superusers can create event triggers.
52
53       Event triggers are disabled in single-user mode (see postgres(1)). If
54       an erroneous event trigger disables the database so much that you can't
55       even drop the trigger, restart in single-user mode and you'll be able
56       to do that.
57

EXAMPLES

59       Forbid the execution of any DDL command:
60
61           CREATE OR REPLACE FUNCTION abort_any_command()
62             RETURNS event_trigger
63            LANGUAGE plpgsql
64             AS $$
65           BEGIN
66             RAISE EXCEPTION 'command % is disabled', tg_tag;
67           END;
68           $$;
69
70           CREATE EVENT TRIGGER abort_ddl ON ddl_command_start
71              EXECUTE FUNCTION abort_any_command();
72

COMPATIBILITY

74       There is no CREATE EVENT TRIGGER statement in the SQL standard.
75