Hibernate version:
NHibernate 2.0 Beta 2
Hi,
this is probably a basic question and I am very sorry if it has been answered a thousand times.
For the past i-dont-know days I've been trying to understand how to map a "little" more complex class hierarchy then the quick start (and the Hibernate quick start) says.
The classes look like this:
Code:
internal abstract class BaseClass
{
public virtual long ID { get; set; }
public virtual string BaseText { get; set; }
}
internal class Sub1 : BaseClass
{
public virtual string Sub1Text { get; set; }
}
internal abstract class Sub2 : BaseClass
{
public virtual string Sub2Text { get; set; }
}
internal class Sub21 : Sub2
{
public virtual string Sub21Text { get; set; }
}
Now this works perfectly well if I map everything with <joined-subclass> and the table per subclass strategy. However it might get pretty inefficient because the children of Sub2 are very similar or have no columns at all. So I want to map the first level by table per subclass and the second by table per class (sub?)hierarchy with Sub2 being "the" table.
I tried several mappings and with one all the Sub21 data went into the BaseClass table (which is perfectly understandable but doesn't make sense in this case) and I want it to go into Sub2 table.
This is the mapping that nearly does what I want (if my "want" is wrong -- correct me!):
Code:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="ConsoleApplication20.BaseClass, ConsoleApplication20" abstract="true">
<id name="ID">
<generator class="native" />
</id>
<discriminator column="Disc" />
<property name="BaseText" />
<joined-subclass name="ConsoleApplication20.Sub1, ConsoleApplication20">
<key column="ID" />
<property name="Sub1Text" />
</joined-subclass>
<joined-subclass name="ConsoleApplication20.Sub2, ConsoleApplication20" abstract="true">
<key column="ID" />
<property name="Sub2Text" />
</joined-subclass>
</class>
<subclass name="ConsoleApplication20.Sub21, ConsoleApplication20" extends="ConsoleApplication20.Sub2, ConsoleApplication20">
<property name="Sub21Text" />
</subclass>
</hibernate-mapping>
I put the last subclass out of Sub2 to get the <subclass>; I hope this is not some form of black voodoo magic.
This is what happens:
Code:
NHibernate: INSERT INTO BaseClass (BaseText) VALUES (@p0); select last_insert_rowid(); @p0 = 'ATXT'
NHibernate: INSERT INTO Sub2 (Sub2Text, Sub21Text, ID) VALUES (@p0, @p1, @p2); @p0 = 'bar2', @p1 = 'foo21Text', @p2 = '1'
NHibernate: INSERT INTO Sub2 (ID) VALUES (@p0); @p0 = '1'
As you can see, the last insert raises a constraint violation (same ID). Oh, I use SQLite by the way.
I hope you can help me with what I'd like to do (although I could just change the class model :)).
I asked a bunch of (Java-) people and they answered "well, we simply limited our class model to a depth of one". Which leaves my other question, should I make the model "simpler"?
Thanks a lot,
Jabe
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