NHibernate prevent cascade delete

Question

Suppose I have a class Foo. I also have a view on Foo called Foo_Foo that lists a many-to-many association between Foos. I mapped this association as a simple immutable set on each Foo, with cascade="none":

<set name="association" table="Foo_Foo" cascade="none" mutable="false">
  <key column="ParentFoo" />
  <many-to-many class="Foo, MyAssembly" column="BaseFoo" />
</set>

However, when I try to delete a Foo, NHibernate tries and rightly fails to delete the Foo.association.

How can I prevent NHibernate from trying to delete the association to a view?

Answer 1

The collection belongs to Foo . You can't share the collection, so there is no need to keep it in the database. Cascade is used to tell NH if the referenced Foo s should be also deleted or not.

Why do you want the Foo_Foo records to keep in the database? If this should be a bidirectional many-to-many self reference, it doesn't work like this.

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Edit, after understanding the question.

Cascade doesn't work in your case, because it affects only the referenced Foos.

To avoid inserts / updates and deletes of the collection table, you may try one of the following:

• First obvious attempt is mutable="false" , which you already tried. I don't really understand why it isn't working. You may ask in the Nhibernate user group.
• Less obvious, but promising is inverse="true" . Inverse tells NH that the collection is mapped somewhere else and doesn't need to be stored from here. So it just omits inserts, but I don't know about deletes.
• If this doesn't work, you need to explore more complex solutions. You could map it as a one-to-many of an intermediate entity which references the Foos. The intermediate entity is a mapping to the view. It is immutable (which still may lead to delete statements). In this case, cascade="false" will work (because it is the referenced entity). It will also work configure insert, update and delete sql statements (which are empty), but this is most probably not even necessary.