title: How to use devices field of the user table in FQL query?
body: <p>I would like the result of a FQL query to only return friends of a user which have a iOS device in their devices list. The following query:</p>
  
  <pre><code>SELECT uid, first_name, devices 
  FROM user 
  WHERE uid IN (SELECT uid2 FROM friend WHERE uid1 = me())
  ORDER BY profile_update_time DESC 
  LIMIT 0, 100
  </code></pre>
  
  <p>returns a list like this:</p>
  
  <pre><code>{
    "data": [
      {
        "uid": 12345678, 
        "first_name": "John", 
        "devices": [
          {
            "os": "iOS", 
            "hardware": "iPhone"
          }
        ]
      },
      {
        "uid": 1234345678, 
        "first_name": "Pete", 
      }
  }
  </code></pre>
  
  <p>Now I would like to only retrieve users who have at least one device where the os is "iOS". I have tried including </p>
  
  <pre><code>devices.os = "iOS"
  </code></pre>
  
  <p>in the query but this returned an error.</p>
  
  <p>Is this possible through the FQL query?  Or should this be solved client side?</p>