title: jpa many to many inverse side cant perform merge operation after been cascaded
body: <p>i have two entity classes with mapping @ManytoMany</p>
  
  <pre><code>Inverse Side
  public class Users implements Serializable {
  @ManyToMany(mappedBy = "usersList",cascade=CascadeType.MERGE)
  private List&lt;Tags&gt; tagsList = new ArrayList();
  
  Owning Side
  public class Tags implements Serializable {
   @JoinTable(name = "USERS_TAG_XREF", joinColumns = {
      @JoinColumn(name = "TAG_ID", referencedColumnName = "TAG_ID")}, inverseJoinColumns  = {
      @JoinColumn(name = "USER_ID", referencedColumnName = "USER_ID")})
    @ManyToMany
    private List&lt;Users&gt; usersList = new ArrayList();
  </code></pre>
  
  <p>Now when i perform an operation on the owning side like this;</p>
  
  <pre><code> for(Tags t : tList){
   Users u = em.find(Users.class, id);  
   t.getUsersList().clear();
   em.merge(t);
   }
  </code></pre>
  
  <p>It clears many users U relations with the Tag entity t, i assume this works because Tag entity is the owing side , but when i perform this with the inverse side ;</p>
  
  <pre><code> Users u = em.find(Users.class,id);
   u.getTagList().clear();
   em.merge(u);
  </code></pre>
  
  <p>It doesnt do anything on the table, i actually want the code to clear many Tags t relations with one User u, but i feel since this is an inverse side by adding the cascade=CascadeType.MERGE would allow merge operation as this em.merge(u); but it doesnt
  please help</p>