Question

For following class mapping:

<class name="Person" table="Person" discriminator-value="null">
    <id name="ID" column="ID" >
        <generator class="identity"/>
    </id>
    <discriminator column="MasterId" />
    <property name="LongName" column="LONGNAME" />
    <property name="ShortName" column="SHORTNAME" />
    // other stuff here ...
    <subclass name="PersonHistory" discriminator-value="not null">
        <property name="MasterId" />
    </subclass>
</class>

when I execute:

        var query =
            from lac in session.Query<Person>()
            orderby lac.LongName
            select lac;
        return query.ToList();

I get all entries from Person table, both with MasterId set to null and not null. Is there a way to get NHibernate fetch only entities with MasterId = null?

Answer 1

In order to achieve what I wanted, I’ve created base class + two subclasses. This is the configuration:

• subclasses with discriminator-value:

  <subclass name="People" discriminator-value="null">
  </subclass>
  <subclass name="PeopleHistory" discriminator-value="not null">
      <property name="MasterRowId" />
  </subclass>
  

• discriminator in base class:

  <discriminator column="MasterRowId" />