CREATE EVENT TRIGGER

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 Event Triggers. 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 Overview of Event Trigger Behavior 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

Notes

Only superusers can create event triggers.

Event triggers are disabled in single-user mode (see postgres) as well as when [event_triggers (boolean)

   event_triggers
   configuration parameter](braised:ref/runtime-config-client#event-triggers-boolean-event-triggers-configuration-parameter) is set to `false`. If an erroneous event trigger disables the database so much that you can\'t even drop the trigger, restart with [event_triggers (boolean)
  
   event_triggers
   configuration parameter](braised:ref/runtime-config-client#event-triggers-boolean-event-triggers-configuration-parameter) set to `false` to temporarily disable event triggers, or in single-user mode, and you\'ll be able to do that.

Examples

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

Compatibility

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