title: Hibernate updates @Version property of entity when adding items to @OneToMany collection - is this normal?
body: <p>I have two Foo and Bar entities which have a 1:n relationship:</p>
  
  <pre><code>@Entity
  public class Foo {
      @Id 
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      @Column(name = "foo_id")
      Integer id;
  
      @OneToMany(fetch = FetchType.LAZY)
      @JoinColumn(name = "foo_id")
      private Set&lt;Bar&gt; bars;
  
      @NotNull
      @Version
      @Temporal(TemporalType.TIMESTAMP)
      @Column(name="update_date", nullable=false)
      private Date updateDate;
  
      // getters and setters ...
  }
  
  @Entity
  public class Bar{
      @Id 
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      @Column(name = "bar_id")
      Integer id;
  
      @ManyToOne(fetch = FetchType.LAZY)
      @JoinColumn(name = "foo_id")
      private Foo foo;
  
  
      // getters and setters ...
  }
  </code></pre>
  
  <p>Now I add a Bar to an existing Foo:</p>
  
  <pre><code>Foo foo = entityManager.find(Foo.class, 1);
  Bar bar = new Bar();
  entityManager.persist(bar);
  foo.getBars().add(bar);
  entityManager.flush();
  </code></pre>
  
  <p>The strange thing is that foo.updateDate gets updated when I call entityManager.flush(), even though the only thing that should happen in the database is an INSERT of a new row to Bar - i.e. the existing Foo row should not be modified. 
  Is this behavior of the Hibernate EntityManager normal / intentional?</p>