Fluent Hibernate Mapping hitch - passing wrong column name for subclass - nhibernate

Question

I finished following the summer of nhibernate screen casts and am trying to convert it to fluent, just for the sake of knowledge.
I have two classes (very simple)
public class Customer { ... }
public class PreferredCustomer : Customer { ... }
These follow table per sub class strategy and so the fluent mapping is so:
CustomerMap -
//nothing related to PreferredCustomer - the spec says not required
public class PreferredCustomerMap : SubclassMap<PreferredCustomer>
{
Map(x => x.CustomerSince);
Map(x => x.OrderDiscountRate);
}
Thats it.
My test is failing, upon inspection, its complaining that sql cant find column customer_id
this is the sql produced by hibernate:
SELECT customer0_.CustomerId as CustomerId1_0_,
customer0_.Version as Version1_0_,
customer0_.Firstname as Firstname1_0_,
customer0_.Lastname as Lastname1_0_,
customer0_1_.CustomerSince as Customer2_2_0_,
customer0_1_.OrderDiscountRate as OrderDis3_2_0_,
//here, customer0_1_.customer_id needs to be CustomerID really.
case when customer0_1_.Customer_id is not null then 1 when customer0_.CustomerId is not null then 0 end as clazz_0_
FROM [Customer] customer0_ left outer join [PreferredCustomer] customer0_1_ on customer0_.CustomerId=customer0_1_.Customerid
WHERE customer0_.Customer_Id=1
Its clearly doing that only on PreferredCustomer joined table. Cant find what needs to be done.
Any Ideas please?
edit: how do I read the xml's produced by fluent? that could be a good start.

Answer 1

You need a call to KeyColumn("CustomerID"); in your SubclassMaps.