title: django Cannot combine queries once a slice has been taken
body: <p>is there any way to concatenate sliced querysets?
  its simplified example (i realize this particular example can be written in one query):</p>
  
  <pre><code>&gt;&gt;&gt; ...
  &gt;&gt;&gt; query_set_1 = Model.objects.filter(...)[:3]
  &gt;&gt;&gt; query_set_2 = Model.objects.filter(...)[5:]
  
  &gt;&gt;&gt; query_set_1 | query_set_2
  </code></pre>
  
  <p>not going to work,</p>
  
  <pre><code>&gt;&gt;&gt; AssertionError: Cannot combine queries once a slice has been taken.
  </code></pre>
  
  <p>any suggestions?
  thanks!</p>