title: Mongoid: Order by field and skip N records
body: <p>I have a collection with the following data:</p>
  
  <pre><code>{
    "_id" : ObjectId("516b969beceaed363a000027"),
    "user" : "276",
    "item" : "796",
    "rating" : 1,
  }
  </code></pre>
  
  <p>I want to order by <code>user</code> and then within each user, I want to skip the first 10 records, and only return the other records. If a user doesn't have 10 records, it should return nothing. And I also need this the other way round: Order by user and only return the first 10 records. If a user doesn't have 10 records, it should return for example 6 records.</p>
  
  <p>I have no idea how to do this in Mongoid, without invoking a ruby script. Any ideas?</p>