CREATE EVENT TRIGGER

define a new event trigger

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anchor: SQL-CREATEEVENTTRIGGER
file: sql-createeventtrigger.html
lang: en
name: CREATE EVENT TRIGGER
purpose: define a new event trigger
purpose zh: 定义一个新的事件触发器
sections same as: Unknown
slug: 18
synopsis text: CREATE EVENT TRIGGER name ON event [ WHEN filter_variable IN (filter_value [, ... ]) [ AND ... ] ] EXECUTE { FUNCTION | PROCEDURE } function_name()

Syntax

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

Syntax diagrams

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Definition PG 18

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 38. 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 38.1 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) as well as when event_triggers 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 set to false to temporarily disable event triggers, or 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.

Compare versions

Complete source facts

synopsis html

CREATE EVENT TRIGGER <em class="replaceable"><code>name</code></em>
    ON <em class="replaceable"><code>event</code></em>
    [ WHEN <em class="replaceable"><code>filter_variable</code></em> IN (<em class="replaceable"><code>filter_value</code></em> [, ... ]) [ AND ... ] ]
    EXECUTE { FUNCTION | PROCEDURE } <em class="replaceable"><code>function_name</code></em>()

Source references

Full definition and evidence JSON

Definition sources

center · PostgreSQL 18 · wiki-repair-20261023:12d2c785bfae285482b786d6e184a7c8596bbfc860c745a7cf2a76d4686ba5c6

Text language: en · wiki-repair-20261023:12d2c785bfae285482b786d6e184a7c8596bbfc860c745a7cf2a76d4686ba5c6