Hi Paul, Peter,

I found a Server crash when using UPDATE ... FOR PORTION OF or DELETE ... FOR PORTION OF on a view that has INSTEAD OF triggers.

Repro:

CREATE TABLE t (id INT, valid_at daterange, val INT);
INSERT INTO t VALUES (1, '[2026-01-01,2026-12-31)', 100);
CREATE VIEW v AS SELECT * FROM t;

CREATE FUNCTION v_trig() RETURNS trigger LANGUAGE plpgsql AS $$
BEGIN
    UPDATE t SET val = NEW.val WHERE id = OLD.id;
    RETURN NEW;
END;
$$;
CREATE TRIGGER trg INSTEAD OF UPDATE ON v
    FOR EACH ROW EXECUTE FUNCTION v_trig();

-- This crashes the server:
UPDATE v FOR PORTION OF valid_at FROM '2026-04-01' TO '2026-08-01'
    SET val = 999 WHERE id = 1;

I am thinking we should just reject this case. Attached a draft patch to fix the issue.