title: return custom query select in activerecord
body: <p>I've got a query that does some math and returns a calculated custom select field with the result set. I cannot figure out how to access that in the activerecord object that is returned. I've added an attr_accessor for it also.</p>
  
  <pre><code>attr_accessor :percentage_used
  
  select('gateways.*, (num_transactions_today/ SUM(num_transactions_today)) AS percentage_used ').joins(:gateway_groups).where('map_gateway_groups.gateway_group_id = ?', gateway_group_id)
  </code></pre>
  
  <p>in the result set, I would expect to have access to :percentage_used, but it is not in there. Any ideas on what i'm doing wrong? i've never needed to do this before.</p>
  
  <p>Thanks</p>