title: Mongodb projection returning a given position
body: <p>I am trying to do something as simple as return a subarray of a document. So my query is:</p>
  
  <pre><code>db.mydocs.findOne({_id:ObjectId("af7a85f758e338d762000012")},{'house.0.room.4.windows':1});
  </code></pre>
  
  <p>I want to return only that value. But I get an empty structure. I know I could do it with $slice. But as far as I know, I can't do it for subarrays. I mean: <code>{'house':{'$slice':0}}</code> would work. But I don't know how to get house 0 and room 4.</p>