CREATE EVENT TRIGGER
CREATE EVENT TRIGGER — define a new event trigger
Synopsis
CREATE EVENT TRIGGERnameONevent[ WHENfilter_variableIN (filter_value[, ... ]) [ AND ... ] ] EXECUTE PROCEDUREfunction_name()
Description
CREATE EVENT TRIGGER creates a new event trigger. Whenever the designated event occurs and theWHEN condition associated with the trigger, if any, is satisfied, the trigger function will be executed. For a general introduction to event triggers, seeChapter 37. The user who creates an event trigger becomes its owner.
Parameters
nameThe name to give the new trigger. This name must be unique within the database.
eventThe name of the event that triggers a call to the given function. SeeSection 37.1 for more information on event names.
filter_variableThe 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_variableisTAG.filter_valueA list of values for the associated
filter_variablefor which the trigger should fire. ForTAG, this means a list of command tags (e.g.,'DROP FUNCTION').function_nameA user-supplied function that is declared as taking no argument and returning type
event_trigger.
Notes
Only superusers can create event triggers.
Event triggers are disabled in single-user mode (seepostgres). 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 anyDDL 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 PROCEDURE abort_any_command();
Compatibility
There is noCREATE EVENT TRIGGER statement in the SQL standard.