JPA和ManyToMany递归关系产生了错误的查询

在Hibernate版本5中,我有一个带有递归 ManyToMany 当我做一个 join fetch 在关系上,我得到一个带有两个连接的查询。我认为只需要一次加入。你知道为什么会生成两个连接,或者如何修复它吗?

@Entity
public class Employee implements Comparable<Employee> {
    @Id Integer id;    
    @ManyToMany
    protected Set<Employee> opinionCitations;
    // getters, setters
}

和

em.createQuery("select distinct e from Employee e left join fetch e.opinionCitations").getSingleResult();

给了我

select distinct 
    employee0_.id as id1_0_0_, 
    employee2_.id as id1_0_1_, 
    opinioncit1_.Employee_id as Employee1_1_0__, 
    opinioncit1_.opinionCitations_id as opinionC2_1_0__ 
from 
    Employee employee0_ 
    left outer join Employee_Employee opinioncit1_ on employee0_.id=opinioncit1_.Employee_id 
    left outer join Employee employee2_ on opinioncit1_.opinionCitations_id=employee2_.id