Database Reference
In-Depth Information
Simple "Hey, I'm called" trigger
The first trigger we work on simply sends back a notice to the database client each
time the trigger is fired and provides some feedback on its firing conditions:
CREATE OR REPLACE FUNCTION notify_trigger()
RETURNS TRIGGER AS $$
BEGIN
RAISE NOTICE 'Hi, I got % invoked FOR % % %
on %',
TG_NAME,
TG_LEVEL,
TG_WHEN,
TG_OP,
TG_TABLE_NAME;
END;
$$ LANGUAGE plpgsql;
Next, we need a table to bind this function to the following:
CREATE TABLE notify_test(i int);
And we are ready to define the trigger. As we try to be simple here, we define a trigger
which is invoked on
INSERT
and which calls the function once on each row:
CREATE TRIGGER notify_insert_trigger
AFTER INSERT ON notify_test
FOR EACH ROW
EXECUTE PROCEDURE notify_trigger();Let's test it
out.postgres=# INSERT INTO notify_test
VALUES(1),(2);
NOTICE: Hi, I got notify_insert_trigger invoked
FOR ROW AFTER INSERT on notify_test
ERROR: control reached end of trigger procedure
without RETURN
CONTEXT: PL/pgSQL function notify_trigger()
