CREATE TRIGGER ad_task_updates_1
AFTER DELETE ON
    task_updates
FOR EACH ROW
BEGIN

    SELECT debug(
        OLD.update_id,
        OLD.task_id,
        OLD.status_id,
        OLD.title
    );

    INSERT OR IGNORE INTO
        tasks_tomerge(task_id)
    VALUES
        (OLD.task_id)
    ;

    UPDATE
        tasks_tomerge
    SET
        status_id = status_id + (OLD.status_id IS NOT NULL),
        title    = title + (OLD.title IS NOT NULL)
    WHERE
        task_id = OLD.task_id
    ;

END;