NHibernate duplicate insert in many-to-many and composite-element

Question

I have in an NHibernate 2 application an Product entity which has an many-to-many relationship to an Location. The Location entity does not have any navigation properties or mappings back to the product. It is mapped like this:

<bag name="Locations" table="ProductLocation" cascade="none">
  <key column="ProductId" />
  <many-to-many column="LocationId" class="Location"/>
</bag>

The product also has an composite-element, a Component with a concentration mapped via the ProductComponent class. The class has no navigation property or mapping back to the product.

<bag name="ProductComponents" table="ProductComponent" access="nosetter.camelcase">
  <key column="ProductId" />
  <composite-element class="ProductComponent">
    <property name="Concentration"/>
    <many-to-one name="Component" column="ComponentId" access="nosetter.camelcase"/>
  </composite-element>
</bag>

This all works fine when just inserting one product at a time. It however fails when batch inserting multiple products.

While the products itself get inserted fine, each product does get an own unique Id, the elements in the many-to-many (Locations) and composite-element (ProductComponent) doesn't get inserted well. This is because NHibernate multiple times executes the insert to the ProductLocation table with the same ProductId.

This causes an duplicate record in the link table. How can this be prevented?

MichaC MichaC · Accepted Answer · 2013-10-14T06:56:05

You'll have to define one site of the relationship to be the owner so that only one side does the insert. This can be achieved with Inverse set to true on the other side.

Find a more detailed explanation here

NHibernate duplicate insert in many-to-many and composite-element

1 Answers