CREATE EVENT TRIGGER(7)  PostgreSQL 16.2 Documentation CREATE EVENT TRIGGER(7)

NAME
       CREATE_EVENT_TRIGGER - define a new event trigger

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

DESCRIPTION
       CREATE EVENT TRIGGER creates a new event trigger. Whenever the
       designated event occurs and the WHEN condition associated with the
       trigger, if any, is satisfied, the trigger function will be executed.
       For a general introduction to event triggers, see Chapter 40. The user
       who creates an event trigger becomes its owner.

PARAMETERS
       name
           The name to give the new trigger. This name must be unique within
           the database.

       event
           The name of the event that triggers a call to the given function.
           See Section 40.1 for more information on event names.

       filter_variable
           The name of a variable used to filter events. This makes it
           possible to restrict the firing of the trigger to a subset of the
           cases in which it is supported. Currently the only supported
           filter_variable is TAG.

       filter_value
           A list of values for the associated filter_variable for which the
           trigger should fire. For TAG, this means a list of command tags
           (e.g., 'DROP FUNCTION').

       function_name
           A user-supplied function that is declared as taking no argument and
           returning type event_trigger.

           In the syntax of CREATE EVENT TRIGGER, the keywords FUNCTION and
           PROCEDURE are equivalent, but the referenced function must in any
           case be a function, not a procedure. The use of the keyword
           PROCEDURE here is historical and deprecated.

NOTES
       Only superusers can create event triggers.

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

EXAMPLES
       Forbid the execution of any DDL command:

           CREATE OR REPLACE FUNCTION abort_any_command()
             RETURNS event_trigger
            LANGUAGE plpgsql
             AS $$
           BEGIN
             RAISE EXCEPTION 'command % is disabled', tg_tag;
           END;
           $$;

           CREATE EVENT TRIGGER abort_ddl ON ddl_command_start
              EXECUTE FUNCTION abort_any_command();

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

SEE ALSO
       ALTER EVENT TRIGGER (ALTER_EVENT_TRIGGER(7)), DROP EVENT TRIGGER
       (DROP_EVENT_TRIGGER(7)), CREATE FUNCTION (CREATE_FUNCTION(7))

PostgreSQL 16.2                      2024              CREATE EVENT TRIGGER(7)