nhibernate does not cascade delete children

Question

The scenario is as follows,

I have 3 objects (i simplified the names) named Parent, parent's child & child's child
parent's child is a set in parent, and child's child is a set in child.

mapping is as follows (relevant parts)

parent

<set name="parentset"
     table="pc-table"
     lazy="false"
     fetch="subselect"
     cascade="all-delete-orphan"
     inverse="true">
  <key column=FK_ID_PC" on-delete="cascade"/>
  <one-to-many class="parentchild,parentchild-ns"/>
</set>

parent's child

<set name="childset"
     table="cc-table"
     lazy="false"
     fetch="subselect"
     cascade="all-delete-orphan"
     inverse="true">
  <key column="FK_ID_CC" on-delete="cascade"/>
  <one-to-many class="childschild,childschild-ns"/>
</set>

What i want to achieve is that when i delete the parent, there would be a cascade delete all the way trough to child's child. But what currently happens is this.

(this is purely for mapping test purposes) getting a parent entity (works fine)

IQuery query = session.CreateQuery("from Parent where ID =" + ID);
IParent doc = query.UniqueResult<Parent>();

now the delete part

session.Delete(doc);
transaction.Commit();

After having solved the 'cannot insert null value' error with cascading and inverse i hopes this would now delete everything with this code, but only the parent is being deleted.

Did i miss something in my mapping which is likely to be missed? Any hint in the right direction is more than welcome!

---

Diego, thank you for the to the point answer. (and explanation)

I went with removing the on-delete="cascade", this because I like as much control as possible in code and not in the database.

The code posted below is the (working) result.

parent

<set name="parentset"     
     table="pc-table"     
     cascade="all-delete-orphan"     
     inverse="true"
     batch-size="5">     
  <key column=FK_ID_PC"/>     
  <one-to-many class="parentchild,parentchild-ns"/>     
</set>

parent's child

<set name="childset"            
     table="cc-table"     
     cascade="all-delete-orphan" 
     batch-size="5"  
     inverse="true">            
  <key column="FK_ID_CC">            
  <one-to-many class="childschild,childschild-ns"/>            
</set>

Hope this helps people with the same problem!

Answer 1

By setting on-delete="cascade" on the keys, you are letting the DB handle the cascading.

Are you generating your schema with NHibernate?

I just reproduced your example and it worked fine with and without that attribute. When removing it, NHibernate does the cascading.

BTW, using lazy="false" fetch="subselect" is not something that you should do by default. If you remove those attributes, leave on-delete="cascade" and change cascade to save-update, you'll only have two queries to retrieve and delete a Parent.