Django 将迁移问题更改为新的 Postgres DB答案

【问题标题】：Django make migrations issue changing to new Postgres DBDjango 将迁移问题更改为新的 Postgres DB
【发布时间】：2026-02-07 07:25:02
【问题描述】：

我还没有找到适合我的 SO 解决方案，所以我想我会发布一个问题。

我在使用 django 将数据库架构迁移到新的 PostgreSQL 数据库时遇到问题。

这是我的第一个数据库的连接，它可以正常工作，并且我能够完美地运行迁移。这是我最初用于测试的数据库，现在我想使用辅助数据库并迁移架构。

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'HOST': '[HOST]',
        'NAME': 'postgres',
        'USER': 'postgres',
        'PASSWORD': '[PW]',
        }
    }

这是更新的设置：

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'HOST': '[HOST]',
        'NAME': 'test_mh',       # this is only difference
        'USER': 'postgres',
        'PASSWORD': '[PW]',
        }
    }

我在第一次连接时运行 python3 manage.py makemigrations，没问题。

当我使用更新后的数据库名称运行相同的命令时，我会收到声明我的表不存在的异常。

  Traceback (most recent call last):
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 85, in _execute
      return self.cursor.execute(sql, params)
  psycopg2.ProgrammingError: relation "objects_community" does not exist
  LINE 1: ...y"."state", "objects_community"."date_added" FROM "objects_c...
                                                               ^


  The above exception was the direct cause of the following exception:

  Traceback (most recent call last):
    File "manage.py", line 15, in <module>
      execute_from_command_line(sys.argv)
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
      utility.execute()
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/__init__.py", line 375, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 316, in run_from_argv
      self.execute(*args, **cmd_options)
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 350, in execute
      self.check()
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 379, in check
      include_deployment_checks=include_deployment_checks,
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 366, in _run_checks
      return checks.run_checks(**kwargs)
    File "/usr/local/lib/python3.6/dist-packages/django/core/checks/registry.py", line 71, in run_checks
      new_errors = check(app_configs=app_configs)
    File "/usr/local/lib/python3.6/dist-packages/django/core/checks/urls.py", line 40, in check_url_namespaces_unique
      all_namespaces = _load_all_namespaces(resolver)
    File "/usr/local/lib/python3.6/dist-packages/django/core/checks/urls.py", line 57, in _load_all_namespaces
      url_patterns = getattr(resolver, 'url_patterns', [])
    File "/usr/local/lib/python3.6/dist-packages/django/utils/functional.py", line 37, in __get__
      res = instance.__dict__[self.name] = self.func(instance)
    File "/usr/local/lib/python3.6/dist-packages/django/urls/resolvers.py", line 533, in url_patterns
      patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
    File "/usr/local/lib/python3.6/dist-packages/django/utils/functional.py", line 37, in __get__
      res = instance.__dict__[self.name] = self.func(instance)
    File "/usr/local/lib/python3.6/dist-packages/django/urls/resolvers.py", line 526, in urlconf_module
      return import_module(self.urlconf_name)
    File "/usr/lib/python3.6/importlib/__init__.py", line 126, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "<frozen importlib._bootstrap>", line 994, in _gcd_import
    File "<frozen importlib._bootstrap>", line 971, in _find_and_load
    File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
    File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
    File "<frozen importlib._bootstrap_external>", line 678, in exec_module
    File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
    File "/home/viatech/Projects/ExactEstate/ExactEstate/ExactEstate/urls.py", line 21, in <module>
      path('adm/', include('interface_admin.urls')),
    File "/usr/local/lib/python3.6/dist-packages/django/urls/conf.py", line 34, in include
      urlconf_module = import_module(urlconf_module)
    File "/usr/lib/python3.6/importlib/__init__.py", line 126, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "<frozen importlib._bootstrap>", line 994, in _gcd_import
    File "<frozen importlib._bootstrap>", line 971, in _find_and_load
    File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
    File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
    File "<frozen importlib._bootstrap_external>", line 678, in exec_module
    File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
    File "/home/viatech/Projects/ExactEstate/ExactEstate/interface_admin/urls.py", line 2, in <module>
      from interface_admin import views
    File "/home/viatech/Projects/ExactEstate/ExactEstate/interface_admin/views.py", line 4, in <module>
      from forms import RegistrationForm, SQLForm, SingleFileUploadForm, ApartmentTableFormBuilder
    File "/home/viatech/Projects/ExactEstate/ExactEstate/forms/ApartmentTableFormBuilder.py", line 10, in <module>
      class ApartmentTableFormBuilder(forms.Form):
    File "/home/viatech/Projects/ExactEstate/ExactEstate/forms/ApartmentTableFormBuilder.py", line 16, in ApartmentTableFormBuilder
      for community in Community.objects.all():
    File "/usr/local/lib/python3.6/dist-packages/django/db/models/query.py", line 268, in __iter__
      self._fetch_all()
    File "/usr/local/lib/python3.6/dist-packages/django/db/models/query.py", line 1186, in _fetch_all
      self._result_cache = list(self._iterable_class(self))
    File "/usr/local/lib/python3.6/dist-packages/django/db/models/query.py", line 54, in __iter__
      results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
    File "/usr/local/lib/python3.6/dist-packages/django/db/models/sql/compiler.py", line 1065, in execute_sql
      cursor.execute(sql, params)
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 100, in execute
      return super().execute(sql, params)
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 68, in execute
      return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 77, in _execute_with_wrappers
      return executor(sql, params, many, context)
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 85, in _execute
      return self.cursor.execute(sql, params)
    File "/usr/local/lib/python3.6/dist-packages/django/db/utils.py", line 89, in __exit__
      raise dj_exc_value.with_traceback(traceback) from exc_value
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 85, in _execute
      return self.cursor.execute(sql, params)
  django.db.utils.ProgrammingError: relation "objects_community" does not exist
  LINE 1: ...y"."state", "objects_community"."date_added" FROM "objects_c...

【问题讨论】：

标签： django postgresql django-migrations

【解决方案1】：

回溯告诉您，当模块加载时，您的表单 ApartmentTableFormBuilder 会导致查询 Community.objects.all()。

当您在新数据库上运行 migrate 或 makemigrations 时，这会导致错误，因为尚未创建 objects_community 表。

正确的解决方案是修改表单，使其在模块加载时不会引起任何查询。一个更老套的解决方案是暂时注释掉导致问题的代码，直到您第一次运行 makemigrations 和 migrate。

【讨论】：

精彩的评论作品！ ApartmentTableFormBuilder 是一种动态表单，用于允许在我的数据库中动态（即非模型）创建公寓表。在那种情况下，我不确定如何不调用 Community.objects.all() 因为这些对象用于列出可用 Communities 的名称HTML 表单的选择选项。虽然这是一个新功能，但我会仔细检查一下，看看我是否可以重新编码事情的工作方式以正确“解决”这个问题。不管怎样，根据你的帖子，我现在很高兴，所以谢谢！
应该可以重新排列您的代码，以便在模块加载时查询不会运行。我无能为力，因为您没有在问题中显示代码。
去劫持这条评论只是为了问@Alasdair一个问题，因为你似乎对这类事情非常了解。考虑这样一个场景，您有一个大型 django 项目，并且您有几个应用程序，这些应用程序的模型在其他应用程序中具有外键。 IE：App1.ModelA 在App2 中有一个模型的FK，App2.ModelB 在App1 中有一个模型的FK。为新数据库进行迁移时，处理此问题的最佳方法是什么？如果您只是尝试运行 makemigrations，它会给出循环依赖错误。谢谢。
@SamCreamer 这是一个不同的问题，它不属于对此答案的评论。