CREATE LANGUAGE plperlu;
\set ECHO none
CREATE TEMP TABLE test(a INTEGER, b INTEGER, c INTEGER);
INSERT INTO test VALUES(1, 2, 3);
CREATE TRIGGER check_updates_on_test BEFORE INSERT OR UPDATE ON test
FOR EACH ROW EXECUTE PROCEDURE check_updates('', 'a', 'b', '%s + %s > 20', 'NEW.a', 'NEW.b');
-- allow --
UPDATE test SET c = 10;
-- deny --
UPDATE test SET a = 5, b = 4 WHERE a = 1;
ERROR:  error from Perl trigger function: update of attribute "a" denied by the trigger "check_updates_on_test" when expression 5 + 4 > 20 is false at line 98.
-- allow --
UPDATE test SET a = 11, b = 10 WHERE a = 1;
DROP LANGUAGE plperlu CASCADE;
NOTICE:  drop cascades to function check_updates()
NOTICE:  drop cascades to trigger check_updates_on_test on table test