Hibernate: updating child object

Question

I have such structure:

// all objects have valid mapping to database
public class Child {
   private int id;
   private String name;
}
public class Parent {
   private int id;
   private String name;
   private List<Child> chidlren;
}

and I have to update specific child B inside parent A.

There are two ways:

1. Update child's fields inside collection and update the whole object:
   Parent temp = dao.getParent(id);
temp.getChildren.get(0).setName('test');
dao.updateParent(temp);

2. Update only child object:
   Child temp = dao.getChild(id);
temp.setName('test');
dao.updateChild(temp);

Which one is better if I want to get more perfomance?

Thank you

Answer 1

On the surface, I would surmise that the second solution

2.Update only child object

would be more performant.

However, the only way you determine this quantitatively would be to turn on Hibernate's show_sql , capture the SQL for Solution 1 and Solution 2, run an Explain Plan for each of your solutions, and compare the resulting Explain Plans.

You could get differing results depending on what else has changed/not changed in the Parent object and other children in the Parent.children collection. When capturing SQL for Explain Plans, you would want to try different scenarios.