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.

Strunk

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.

Waver

I have the same issue but, in my case, I don't get the name of the models in circular dependency, I just get the names of the apps. How can I know which models are circularly dependent? – Raymond

@HugoLuisVillalobosCanto the error message here didn't name the models either, I had to look at the foreign keys between apps. We can't help you in the comments here, because we don't know your models. – Waver

There must be a better way, right? Why is there not another solution other than commenting and uncommenting. – Bering

@NickSmith this question is several years old, uses made-up variables like firstapp, and doesn't include the migrations that were failing, so it's not the best place to try to solve your problem. When I created two apps with fks to each other in Django 3.1, it created two migrations for one of the apps and avoided a circular dependency in the migrations, so no commenting-out was necessary. – Waver

@Waver Cool to see a response!! I am still getting the err, can I post a new question with my details and paste the link here? – Bering

@NickSmith No promises I'll be able to help, but if you post a new question I'll have a look. – Waver

@Waver Would love your help... question is posted here: #65332966 THANK YOU SOOOO MUCH – Bering

Answer 2

Should be useful if you add your Calendar model. However don't use the inheritance without abstract modal.

class Person(models.Model):
    ...

    class Meta:
        abstract = True

Whereon

Thanks for your attention, it will be usefull for my case. – Strunk

Answer 3

Like you might have defined them as something below:

new_field = models.ForeignKey(ForeignModel, ...)

Instead do this:

new_field = models.ForeignKey("ForeignModel", ...)

Valedictory

Answer 4

1. Delete your existing virtual environment and create a new one.
2. In your models files, comment out all ForeignKey fields.
3. Run migrations and migrate
4. Uncomment the ForeignKey fields you commented
5. Again run migrations and migrate

Royce