Django manage.py 测试：“数据库后端不接受 0 作为 AutoField 的值”（mysql）

Posted 2023-02-24

【中文标题】Django manage.py 测试：“数据库后端不接受 0 作为 AutoField 的值”（mysql）

【英文标题】：Django manage.py test: “database backend does not accept 0 as a value for AutoField” (mysql)

【发布时间】：2019-07-19 07:56:31

【问题描述】：

我正在尝试使用以下方法运行 Django 测试文件：

python3.6 manage.py test

我使用：MySQL 5.5.62、Python 3.6、Django 2.0.0

它开始安装测试数据库并失败并出现错误：

ValueError: The database backend does not accept 0 as a value for AutoField.

我搜索了这个错误，但我发现的所有主题都与迁移有关，例如this one。我对迁移没有问题，它们运行顺利。

追溯：

Traceback (most recent call last):
  File "manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/__init__.py", line 371, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.6/site-packages/django/core/management/__init__.py", line 365, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/commands/test.py", line 26, in run_from_argv
    super().run_from_argv(argv)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/base.py", line 335, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/commands/test.py", line 59, in handle
    failures = test_runner.run_tests(test_labels)
  File "/usr/local/lib/python3.6/site-packages/django/test/runner.py", line 601, in run_tests
    old_config = self.setup_databases()
  File "/usr/local/lib/python3.6/site-packages/django/test/runner.py", line 548, in setup_databases
    self.parallel, **kwargs
  File "/usr/local/lib/python3.6/site-packages/django/test/utils.py", line 176, in setup_databases
    serialize=connection.settings_dict.get('TEST', ).get('SERIALIZE', True),
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/base/creation.py", line 68, in create_test_db
    run_syncdb=True,
  File "/usr/local/lib/python3.6/site-packages/django/core/management/__init__.py", line 141, in call_command
    return command.execute(*args, **defaults)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/base.py", line 335, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 200, in handle
    fake_initial=fake_initial,
  File "/usr/local/lib/python3.6/site-packages/django/db/migrations/executor.py", line 117, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python3.6/site-packages/django/db/migrations/executor.py", line 147, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python3.6/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/usr/local/lib/python3.6/site-packages/django/db/migrations/migration.py", line 122, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/usr/local/lib/python3.6/site-packages/django/db/migrations/operations/fields.py", line 216, in database_forwards
    schema_editor.alter_field(from_model, from_field, to_field)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 509, in alter_field
    old_db_params, new_db_params, strict)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 613, in _alter_field
    old_default = self.effective_default(old_field)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 224, in effective_default
    default = field.get_db_prep_save(default, self.connection)
  File "/usr/local/lib/python3.6/site-packages/django/db/models/fields/related.py", line 936, in get_db_prep_save
    return self.target_field.get_db_prep_save(value, connection=connection)
  File "/usr/local/lib/python3.6/site-packages/django/db/models/fields/__init__.py", line 767, in get_db_prep_save
    return self.get_db_prep_value(value, connection=connection, prepared=False)
  File "/usr/local/lib/python3.6/site-packages/django/db/models/fields/__init__.py", line 940, in get_db_prep_value
    value = connection.ops.validate_autopk_value(value)
  File "/usr/local/lib/python3.6/site-packages/django/db/backends/mysql/operations.py", line 163, in validate_autopk_value
    raise ValueError('The database backend does not accept 0 as a '
ValueError: The database backend does not accept 0 as a value for AutoField.

如何修复此错误并运行测试？

【问题讨论】：

好吧，根据回溯，它确实发生在迁移期间：测试数据库的迁移。

@WillemVanOnsem 谢谢，这确实是真的，但是对于测试迁移我能做些什么呢？他们在迁移文件夹中没有迁移文件。

看看这个：***.com/a/46402659/6808714

@MahrezBenHamad 谢谢，我在发布之前已经看过它，但我花了一段时间才意识到这些是切换到 MTPP 引起的迁移问题，并设置了 lft、level 等解决方法......为 0，然后删除这些字段。我最终删除了迁移，因为这是一个测试项目。

【参考方案1】：

好吧，看来这确实是 @Willem Van Onsem 建议的迁移。我最终删除了迁移并解决了问题。

可能值得指出的是，混乱是由于从 Django 模型切换到 Django MTPP 模型并使用0 作为新添加的 MTPP 字段的默认值以避免该过程中的另一个问题造成的。