title: Django model instances primary keys do not reset to 1 after all instances are deleted
body: <p>I have been working on an offline version of my Django web app and have frequently deleted model instances for a certain ModelX.</p>
  
  <p>I have done this from the admin page and have experienced no issues. The model only has two fields: name and order and no other relationships to other models.</p>
  
  <p>New instances are given the next available pk which makes sense, and when I have deleted all instances, adding a new instance yields a pk=1, which I expect.</p>
  
  <p>Moving the code online to my actual database I noticed that this is not the case. I needed to change the model instances so I deleted them all but to my surprise the primary keys kept on incrementing without resetting back to 1.</p>
  
  <p>Going into the database using the Django API I have checked and the old instances are gone, but even adding new instances yield a primary key that picks up where the last deleted instance left off, instead of 1.</p>
  
  <p>Wondering if anyone knows what might be the issue here.</p>