title: Document updates using mongo-ruby-driver?
body: <p>Assuming the following:</p>
  
  <pre><code>irb&gt; x
  irb&gt; =&gt; {"_id"=&gt; 123456, "welcome"=&gt;"Hi!", "welcome2" =&gt; "Enjoy your stay!"}
  irb&gt; coll.class
  irb&gt; =&gt; Mongo::Collection
  </code></pre>
  
  <p>How can I use the raw mongo-ruby-driver to update the document corresponding to x by using both the rewriting method and the atomic update method? (See <a href="http://api.mongodb.org/ruby/current/file.TUTORIAL.html#Updating_a_Document" rel="noreferrer">http://api.mongodb.org/ruby/current/file.TUTORIAL.html#Updating_a_Document</a>)</p>