title: NHibernate queries return multiple copies of the target objects
body: <p>I have two classes mapped in NHibernate: <code>Dragon</code> and its subclass <code>FierceDragon</code>, with a few <code>FierceDragon</code>s stored stored in a table called <code>Dragons</code>.  When I run an HQL query like <code>from Dragon...</code> I get back two objects per row: the expected <code>FierceDragon</code> and an ordinary <code>Dragon</code> that's a copy of the <code>FierceDragon</code> (insofar as is possible; naturally it lacks the <code>FierceDragon</code>'s extra <code>Ferocity</code> and <code>TimeSinceLastMeal</code> properties).  In particular, their IDs are identical.  When I do <code>from FierceDragon</code> I get only <code>FierceDragon</code>s, with no extra copies, but that won't work for me in general.</p>
  
  <p>Why does this happen, and how can I prevent it?</p>