I am mapping 2 classes with <many-to-one> or <one-to-one> with "property-ref" attribute



Then using this HQL: what I expected is NHibernate can just send one query to the DB to fetch the data:


But NHibernate is acctually issuing 2 queries, the first one is what I expected, join fetched both ClassA and ClassB. But the 2nd one is a query to get ClassB AGAIN with condition "ClassB.A_ID = :p0"

If I get rid of "property-ref" in ClassA mapping, that means I need to add a column in ClassA's table named "B_ID", then the HQL can run with one query, but I don't like to change the table or create a View, it's a legacy database, and I am afraid View will be slow.


why this is happening, does Hibernate 3.x solved this already :?:

The problem with property-refs is that NHibernate keeps track of all objects by their identifier, so it has trouble figuring out whether the object is already loaded when all it has is its property-ref value. So expect a bit slower performance for such a schema. I don't know if Hibernate3 has any workarounds for this. You should try creating the view and evaluating its performance.