delete on collection element performs update on parent

flf-hibernate · **Joined:** Tue Mar 09, 2004 12:01 am **Posts:** 9

I have a parent-child relationship mapped using a Set, (one-to-many). When I remove an element from the collection (parent.getChildren().remove(child)) and submit the change to hibernate using session.update(parent) then 2 SQL queries are produced, one updating the parent (every field of it) and one doing the right update on the child (id=null).

I am supposing the update of every field happens because I am updating the parent in another session than the one where I retrieved it (web app).

Is there a way to tell hibernate to commit the collection changes only.

Fabien.

PS: this is with hibernate 2.1 and mysql 3.51 transactional

Sample of code:

Code:

public class Parent  {
// [...]

    /**
     * @hibernate.set cascade="delete"
     *                table="children"
     *                where="type='place'"
     * @hibernate.collection-key column="owner_id"
     * @hibernate.collection-one-to-many  
     *                                   class="ChildImpl"
     */
     Collection getChildren() {
          return children
      }
}

Code:

Session session = sessionFactory.openSession();
Parent parent = (Parent) session.get(Parent.class,"1");
session.close();

// later

parent.getChildren().remove(aChild);
Session session = sessionFactory.openSession();
Transaction transaction = session.beginTransaction();
session.update(parent);
transaction.commit();
session.close();

// --> 2 SQL statements

emmanuel · **Posted:** Tue Mar 09, 2004 3:04 pm

http://www.hibernate.org/155.html

flf-hibernate · **Joined:** Tue Mar 09, 2004 12:01 am **Posts:** 9

inverse="true" on the set does not solve the problem (although it is problably a good idea in this case).
I just need to do:

Code:

parent.remove(aChild)
aChild.setParentId(parent.getId());
session.update(aChild);

This will not do the best possible update since it will update child name and parentid in the db instead of parentid only.
To better optimize it, it looks like a HQL query would do it.

My problem was not due to inverse="false" but just to the fact that I am doing the update of the parent in another session (it would actually do only one update on the children if asked in 1 session only).

Another way to optimize it would maybe be to use JCS, but I am not sure about it and JCS docs are too short to answer this question.

michael · **Posted:** Tue Mar 09, 2004 4:00 pm

For a start, you should not have "setParentId" at all, but "setParent", mapped with a many-to-one relation element.

flf-hibernate · **Joined:** Tue Mar 09, 2004 12:01 am **Posts:** 9

Yes you are probably right. But that does not change things much, I will just have a

Code:

Child aChild = new Child();
parent.add(aChild);
aChild.setParent(parent);
session.save(aChild);

to add a child and

Code:

parent.remove(aChild);
aChild.setParent(null);
session.update(aChild);

to remove a child.

In fact it works the same way with parentId, except that the parent is not accessible through the child, I am even quite sure that cascade delete would work with parentId. One reason why I used parentId was to avoid too many relations, for possible easier serialization, and because I never need to access the parent from the child in my case.

The bad idea was to update the parent when not in the same session (although very practicle when retrieving parent and removing child in the same session).