Nhibernate subclass mapping problem

Question

I am using nhibernate subclass mapping to handle descriptions of objects of the system. Basically idea is to have a description class and make polymorphic associations by having sub classes specific to the object. My code inserts the description data correctly to the Database; that means the ownerid and ownertype columns are created correctly when I insert data.

But nhibernate is not using the OwnerType column for querying descriptions of Foo when I load Foo object using nhibernate.load() - It just queries the descriptions table using the ownerId column only which creates conflict since there can be other rows in the table with the same id but associated to a different ownertype.

Can you helop me find why it does not include ownerType for descriptions on the load query and how can I fix this? Thanks!

public class Product : EntityBase
{
    public virtual string Name { get; set; }
    public virtual IList<ProductDescription> Descriptions { get; set; }
}

public class ProductDescription : Description
{
    public virtual Product Product { get; set; }
}

public class Description : EntityBase
{
    public virtual string Name { get; set; }
    public virtual string ShortDescription { get; set; }
    public virtual string LongDescription { get; set; }
}


<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="Test.Domain" assembly="Test.Domain">
    <class name="Test.Domain.Product, Test.Domain" table="Products">
        <id name="ID" column="ID" type="Int32" unsaved-value="0">
            <generator class="native" />
        </id>

        <property name="Name" />

        <bag name="Descriptions" inverse="true" cascade="all">
            <key column="OwnerID" />
            <one-to-many class="Test.Domain.ProductDescription, Test.Domain" />
        </bag>
    </class>
</hibernate-mapping>

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="Test.Domain" assembly="Test.Domain">
<class name="Test.Domain.Description, Test.Domain" table="Descriptions" discriminator-value="0">
        <id name="ID" column="ID" type="Int32" unsaved-value="0">
            <generator class="native" />
        </id>

        <discriminator column="OwnerType" />

        <property name="Name" />
        <property name="ShortDescription" />
        <property name="LongDescription" />

        <subclass name="Test.Domain.ProductDescription, Test.Domain" discriminator-value="1">
            <many-to-one name="Product" class="Test.Domain.Product, Test.Domain" column="OwnerID" not-null="true"></many-to-one>
        </subclass>
</class>
</hibernate-mapping>

Answer 1

I have a question for you; Why are you using nHibernate? If you are only doing CRUD operations I suggest just using ODBC you will be far happier.

Straight from the nHibernate docs: Cat fritz = (Cat) sess.Load(typeof(Cat), generatedId);

Is that what you are doing? In the future show the actual code that is being used, its hard to make theoretical guesses.

Answer 2

On your discriminator mapping add force=true

<discriminator column="OwnerType" force="true" />

this will ensure that the ownertype is added to the query