title: Atomic increment of a counter in django
body: <p>I'm trying to atomically increment a simple counter in Django. My code looks like this:</p>
  
  <pre><code>from models import Counter
  from django.db import transaction
  
  @transaction.commit_on_success
  def increment_counter(name):
      counter = Counter.objects.get_or_create(name = name)[0]
      counter.count += 1
      counter.save()
  </code></pre>
  
  <p>If I understand Django correctly, this should wrap the function in a transaction and make the increment atomic. But it doesn't work and there is a race condition in the counter update. How can this code be made thread-safe?</p>