如何在不获取完整实体的情况下获取从属Hibernate实体的外键列值？

String hql = "SELECT e.id FROM Entity e WHERE e.parentId = :parentId";
Query query = session.createQuery(hql);
query.setParameter("parentId", parentId);
List<Integer> ids = query.list();

Criteria criteria = session.createCriteria(Entity.class);
criteria.setProjection(Projections.property("id"));
criteria.add(Restrictions.eq("parentId", parentId));
List<Integer> ids = criteria.list();

String sql = "SELECT id FROM entity WHERE parent_id = :parentId";
Query query = session.createSQLQuery(sql);
query.setParameter("parentId", parentId);
List<Integer> ids = query.list();

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Integer> cq = cb.createQuery(Integer.class);
Root<Entity> root = cq.from(Entity.class);
cq.select(root.get("id"));
cq.where(cb.equal(root.get("parentId"), parentId));
TypedQuery<Integer> query = entityManager.createQuery(cq);
List<Integer> ids = query.getResultList();