title: Changing schemas in mongoDB/mongoose
body: <p>I am getting started with mongoDB and mongoose. I was wondering how people manage <strong>evolving schemas</strong>. For example if i started with a schema like this:</p>
  
  <pre><code>user_ID : 123,
  user_firstName : 'bob',
  user_lastName : 'smith'
  </code></pre>
  
  <p>And evolved it to something like this:</p>
  
  <pre><code>user_ID: 123,
  user_name: [first:'bob', last:'smith']
  </code></pre>
  
  <p><strong>How could I update or manage old records that were established using the old schema design?</strong></p>