title: Mongoose bulk update operation
body: <p>Is there a way to do bulk updates on a collection in mongoose? The strategy I had found used the raw collection driver as follows:</p>
  
  <pre><code>var bulk = Person.collection.initializeOrderedBulkOp();
  bulk.find(query).update(update);
  ...
  bulk.execute(callback)
  </code></pre>
  
  <p>However, <code>bulk</code> is undefined when I do this. Is it just not supported by mongoose?</p>