find_unused_django_content_types.py

from django.contrib.auth.models import Permission
from django.db.models.deletion import ProtectedError
from django.contrib.contenttypes.models import ContentType
from django.db.models.deletion import Collector

def get_dependencies(obj):
  collector = Collector(using="default")
  collector.collect([obj])
  return collector.data

def permission_is_used(permission):
  try:
    dependencies = get_dependencies(permission)
  except ProtectedError:
    return True
  if len(dependencies) != 1:
    return True
  if Permission not in dependencies:
    return True
  return False
    

def content_type_is_used(content_type):
  if content_type.model_class():
    return True
  try:
    dependencies = get_dependencies(content_type)
  except ProtectedError:
    return True
  dependencies.pop(ContentType)
  try:
    permissions = dependencies.pop(Permission)
    for perm in permissions:
      if permission_is_used(perm):
        return True
  except KeyError:
    pass
  if len(dependencies) > 0:
    return True
  return False


unused_content_type_ids = []
for content_type in ContentType.objects.all().order_by("app_label", "model"):
  if not content_type_is_used(content_type):
    print(content_type.id, content_type.app_label, content_type.name, content_type.model, content_type.model_class())
    unused_content_type_ids.append(content_type.id)

# Run this if you are sure about everything:
# ContentType.objects.filter(id__in=unused_content_type_ids).delete()