django.db.migrations.exceptions.CircularDependencyError

Question

我在空数据库上进行 Django 迁移时遇到问题。当我想迁移时，出现循环依赖错误。通过外键关联的两个应用程序之间的循环依赖错误

/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/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

感谢您的帮助。

Answer 1

暂时注释掉外键以打破循环依赖。看来你可以通过注释掉

Hospital.doctor

来做到这一点。删除现有的迁移并运行

makemigrations

重新创建它们。

最后，取消注释外键，然后再次运行

makemigrations

。您最终应该得到没有任何循环依赖的迁移。

Answer 2

如果您添加日历模型，应该会很有用。但是，不要在没有抽象模式的情况下使用继承。

class Person(models.Model):
    ...

    class Meta:
        abstract = True

Answer 3

就像您可能将它们定义为以下内容：

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

而是这样做：

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

Answer 4

1. 删除现有的虚拟环境并创建一个新的。
2. 在模型文件中，注释掉所有

   ForeignKey

   字段。
3. 运行迁移并迁移
4. 取消注释您评论过的

   ForeignKey

   字段
5. 再次运行迁移并迁移