one-to-one does not work in self referencing object

rolandz · **Posted:** Fri Apr 18, 2008 2:16 pm

In my self referencing object scenario the one-to-one properties do not get reflected in database (no appropriate columns are there). What's amazing to me - the criteria queries with criteria "IsNull" on such property does not produce errors... I am using NH 1.2. Please help me with this - I have no idea about it. Being honest I am using one-to-one relationship very seldom. Maybe because I've never been satisfied with the way it works (i.e. lazy loading).

Following is the mapping of my scenario:

Code:

   <class name="Task">
      <id name="Id">
         <generator class="native" />
      </id>

      <property name="TaskState" not-null="true" />
      <one-to-one name="Previous" lazy="proxy" />
      <one-to-one name="Next" lazy="proxy" />

      <joined-subclass name="...">
         <key column="`TASK_ID`" />
                        . . .
      </joined-subclass>

      <joined-subclass name="...">
         <key column="`TASK_ID`" />
                        . . .
      </joined-subclass>
   </class>

rolandz · **Posted:** Sat Apr 19, 2008 1:59 am

[For those who might find it usefull]

I think I can answer to myself. Changing from one-to-one relationship to many-to-one provides mea proper scenario implementation. The point is that the key referensing to the same table implements in fact such a scenario. there may be many rows referencing just one particular.

Moreover there is no way to implement one-to-one relashion between two entities without affecting two tables, is there? It would require to manage triggers or other mechanisms during inserts to check the relationship quantity. NH simply offers one-to-one mapping relashion between two entities.

There is a philosophical question, however. How often the one-to-one relationship can be usefull regarding the limitation (or specification). At least for this particular scenario it is not usefull.