django.db.migrations.exceptions.CircularDependencyError

Question

I have a problem with Django migrations on empty DB. When I want to migrate I have a circular dependency error. Circular dependency error between two apps that related by foreign keys

/firstapp/models.py

class Person(models.Model):
   ...


class Doctor(Person):
    hospital = models.ForeignKey('hospital.Hospital', on_delete=models.SET_NULL, null=True, default=None,blank = True)
    ...

class Patient(Person):
    doctor = models.ForeignKey('Doctor', on_delete=models.SET_NULL, null=True, default=None)

/secondapp/models.py

class Hospital(models.Model):
    ...
    main_doctor = models.ForeignKey('authoriz.Doctor', on_delete=models.SET_NULL, null=True,verbose_name="Main Doctor")
    calendar = models.ForeignKey('schedule.Calendar',verbose_name="calendar",null = True)
    ...

class Seat(models.Model):
    hospital = models.ForeignKey('Hospital', on_delete=models.CASCADE)
    ...

After

python manage.py migrate

Traceback

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/home/user/project/lib/python3.5/site-packages/django/core/management/__init__.py", line 367, in execute_from_command_line
    utility.execute()
  File "/home/user/project/lib/python3.5/site-packages/django/core/management/__init__.py", line 359, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/user/project/lib/python3.5/site-packages/django/core/management/base.py", line 305, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/home/user/project/lib/python3.5/site-packages/django/core/management/base.py", line 356, in execute
    output = self.handle(*args, **options)
  File "/home/user/project/lib/python3.5/site-packages/django/core/management/commands/migrate.py", line 136, in handle
    plan = executor.migration_plan(targets)
  File "/home/user/project/lib/python3.5/site-packages/django/db/migrations/executor.py", line 60, in migration_plan
    for migration in self.loader.graph.forwards_plan(target):
  File "/home/user/project/lib/python3.5/site-packages/django/db/migrations/graph.py", line 280, in forwards_plan
    self.ensure_not_cyclic(target, lambda x: (parent.key for parent in self.node_map[x].parents))
  File "/home/user/project/lib/python3.5/site-packages/django/db/migrations/graph.py", line 370, in ensure_not_cyclic
    raise CircularDependencyError(", ".join("%s.%s" % n for n in cycle))
django.db.migrations.exceptions.CircularDependencyError: authoriz.0001_initial, hospital.0001_initial

Thanks for help.

Answer 1

Temporarily comment out foreign keys to break the circular dependency. It looks like you could do this by commenting out Hospital.doctor. Remove the existing migrations and run makemigrations to recreate them.

Finally, uncomment the foreign keys, and run makemigrations again. You should end up with migrations without any circular dependencies.