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)...