CREATE_EVENT_TRIGGER(7)

1CREATE EVENT TRIGGER(7)  PostgreSQL 15.4 Documentation CREATE EVENT TRIGGER(7)
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NAME

6       CREATE_EVENT_TRIGGER - define a new event trigger
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SYNOPSIS

9       CREATE EVENT TRIGGER name
10           ON event
11           [ WHEN filter_variable IN (filter_value [, ... ]) [ AND ... ] ]
12           EXECUTE { FUNCTION | PROCEDURE } function_name()
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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 40. The user
19       who creates an event trigger becomes its owner.
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PARAMETERS

22       name
23           The name to give the new trigger. This name must be unique within
24           the database.
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26       event
27           The name of the event that triggers a call to the given function.
28           See Section 40.1 for more information on event names.
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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.
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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').
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41       function_name
42           A user-supplied function that is declared as taking no argument and
43           returning type event_trigger.
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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.
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NOTES

51       Only superusers can create event triggers.
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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.
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EXAMPLES

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

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