title: MongoDB retrieving selected objects from nested documents
body: <p>Is it possible to query for specific objects within a nested document? Heres an example,</p>
  
  <pre><code>Collection : Threads
  {
      Documents : Messages
      {
          threadId = 1
          messages = [
              {
                  user = amy
                  date = 01/01/2012
                  content = hey
              },
              {
                  user = bell
                  date = 01/01/2012
                  content = hey
              },
              {
                  user = bell
                  date = 01/02/2012
                  content = whats up
              }
          ]
      },
      {
          threadId = 2
          messages = [
              {
                  user = courtney
                  date = 01/03/2012
                  content = first!
              }
          ]
      }
  }
  </code></pre>
  
  <p>I would like my query to say <code>{ threadId : 1, 'messages.date' : { $gt : 01/01/2012 } }, { fields : { messages : 1 } }</code>. But it will return all of that documents messages when really all i want as a result is this,</p>
  
  <pre><code>messages = [
      {
          user = bell
          date = 01/02/2012
          content = whats up
      }
  ]
  </code></pre>