title: Django Data Migration, using South with Inheritance
body: <p>We are migrating the data in several instances of our Django project to a new schema.  </p>
  
  <p>The old schema had:</p>
  
  <pre><code>class Group(models.Model)
  class User(models.Model)
  </code></pre>
  
  <p>And the new schema has:</p>
  
  <pre><code>class AccessEntity(models.Model)
  class Group(AccessEntity)
  class User(AccessEntity)
  </code></pre>
  
  <p>We are trying to use South to do a data migration for these groups and users. <a href="http://south.aeracode.org/docs/tutorial/part3.html" rel="nofollow">http://south.aeracode.org/docs/tutorial/part3.html</a></p>
  
  <p>I've gathered that I'll need to use forward rules to specify how to migrate the Users but there are a few issues I've run up against.</p>
  
  <p>The main issue is how to keep the ID of the User/Group the same if I were to create a new User object that extends the AccessEntity class.</p>
  
  <p>Users &amp; Groups are referenced to by objects they own or are assigned to them. If I change their ID that information would be lost. Is there a way of keeping the same ID for an object even though I need it to now extend from AccessEntity? </p>