title: MongoDB query comparing 2 fields in same collection without $where
body: <p>Does MongoDB supports comparing two fields in same collection by using <strong>native operators</strong> (not $where and JavaScript)? 
  I already looked at <a href="https://stackoverflow.com/questions/8433046/mongodb-query-with-fields-in-the-same-documents">similar</a> <a href="https://stackoverflow.com/questions/4442453/mongodb-query-condition-on-comparing-2-fields">questions</a> and all answers used $where / JavaScript. </p>
  
  <p>MongoDB <a href="http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-JavascriptExpressionsand%7B%7B$where%7D%7D" rel="nofollow noreferrer">documentation</a> clearly states that: </p>
  
  <blockquote>
    <p>JavaScript executes more slowly than the native operators listed on this page, but is very flexible.</p>
  </blockquote>
  
  <p>My primary concern is speed and I would like to use indexes if possible. So is comparing two fields in MongoDB possible without using JavaScript?</p>