title: JPA inheritance query (Eclipse Link)
body: <p>Consider the following schema:</p>
  
  <pre class="lang-java prettyprint-override"><code>public class A {
      @Id
      int id;
      String fieldA;
  }
  </code></pre>
  
  <pre class="lang-java prettyprint-override"><code>public class B extends A {
      String fieldB;
  }
  </code></pre>
  
  <pre class="lang-java prettyprint-override"><code>public class C extends A {
      String fieldC;
  }
  </code></pre>
  
  <p>How can I query <code>A</code> in such a way to get <strong><em>all</em></strong> the <code>C</code>'s and get <strong><em>only</em></strong> the <code>B</code>'s where <code>fieldB="someValue"</code>?</p>
  
  <p>I have tried to use <strong>treat</strong> in order to make downcast but it seems that the filter on <code>B</code> is working on all the parent class (<code>A</code>).</p>
  
  <p>Is such query possible in the first place?</p>