django.db.migrations.exceptions.CircularDependencyError

Question

我对空DB上的Django迁移有问题。当我想要迁移时，我有一个循环依赖错误。外键关联的两个app出现循环依赖错误

/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应用程序/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)
    ...

之后

python manage.py migrate

回溯

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

谢谢你的帮助。

Answer 1

暂时注释掉外键以中断循环依赖。看起来你可以通过注释掉Hospital.doctor来做到这一点。删除现有迁移并运行makemigrations重新创建它们。

最后，取消注释外键，并再次运行makemigrations。您应该以不存在任何循环依赖关系的迁移结束。

Answer 2

如果你添加你的日历模型，它应该是有用的。但是，在没有抽象模式的情况下，不要使用继承。

class Person(models.Model):
    ...

    class Meta:
        abstract = True

Answer 3

就像您可能已经将它们定义为以下内容：

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

取而代之的是：

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