| CREATE_EVENT_TRIGGER(7) - phpMan
CREATE EVENT TRIGGER(7) PostgreSQL 12.3 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 39. 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 39.1 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 12.3 2020 CREATE EVENT TRIGGER(7)
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