How to execute PostgreSQL function at specific time interval? - postgresql

Question

Is there anything similar to setTimeout setTimeInterval in PostgreSQL which allows to execute piece of code (FUNCTION) at specified time interval?
As far as I know only thing that can execute a FUNCTION according to certain event is Triggers but it is not time based but operation driven (INSERT / UPDATE / DELETE / TRUNCATE)
While I could do this in application code, but prefer to have it delegated to database. Anyway I could achieve this in PostgreSQL? May be an extension?

Answer 1

Yes, there is a way to do this. It's called pg_sleep:
CREATE OR REPLACE FUNCTION my_function() RETURNS VOID AS $$
BEGIN
LOOP
PERFORM pg_sleep(1);
RAISE NOTICE 'This is a notice!';
END LOOP;
END;
$$ LANGUAGE plpgsql;
SELECT my_function();
This will raise the notice every second. You can also make it do other things instead of raising a notice.
OR
You can use PostgreSQL's Background Worker feature.
The following is a simple example of a background worker that prints a message every 5 seconds:
CREATE OR REPLACE FUNCTION print_message() RETURNS VOID AS $$
BEGIN
RAISE NOTICE 'Hello, world!';
END;
$$ LANGUAGE plpgsql;
CREATE OR REPLACE FUNCTION schedule_print_message() RETURNS VOID AS $$
DECLARE
job_id BIGINT;
BEGIN
SELECT bgw_start_recurring_job(
'print-message',
'print_message',
'5 seconds'
) INTO job_id;
END;
$$ LANGUAGE plpgsql;
SELECT schedule_print_message();