pg_dbms_lock

pig build pkg pg_dbms_lock         # build DEB packages

pig repo add pgsql -u          # Add repo and update cache

CREATE EXTENSION pg_dbms_lock CASCADE;  -- requires: pg_background

CREATE EXTENSION pg_dbms_lock;

DO $$
DECLARE
    lockhandle varchar;
BEGIN
    CALL dbms_lock.allocate_unique(
        lockname => 'printer_lock',
        lockhandle => lockhandle
    );
    RAISE NOTICE 'Handle: %', lockhandle;
END;
$$;

DO $$
DECLARE
    lock_res int;
BEGIN
    lock_res := dbms_lock.request(
        id => 123,
        lockmode => 6,           -- Exclusive
        timeout => 300,
        release_on_commit => false
    );
    IF lock_res <> 0 THEN
        RAISE EXCEPTION 'Lock request failed: %', lock_res;
    END IF;
END;
$$;

DO $$
DECLARE
    lock_res int;
BEGIN
    lock_res := dbms_lock.release(id => 123);
    IF lock_res <> 0 THEN
        RAISE EXCEPTION 'Release failed: %', lock_res;
    END IF;
END;
$$;

CALL dbms_lock.sleep(0.70);  -- sleep 0.7 seconds

DO $$
DECLARE
    lock_res int;
    printer_lockhandle varchar;
BEGIN
    CALL dbms_lock.allocate_unique('printer_lock', printer_lockhandle);
    lock_res := dbms_lock.request(lockhandle => printer_lockhandle, lockmode => 6, timeout => 5);
    IF lock_res <> 0 THEN
        RAISE EXCEPTION 'REQUEST failed: %', lock_res;
    END IF;
    -- do exclusive work here
    lock_res := dbms_lock.release(lockhandle => printer_lockhandle);
END;
$$;