django.db.utils.ProgrammingError：关系不存在与递归模型答案

【问题标题】：django.db.utils.ProgrammingError: relation does not exist with recursive modeldjango.db.utils.ProgrammingError：关系不存在与递归模型
【发布时间】：2021-09-19 16:23:28
【问题描述】：

我有一个 django 应用程序，它在我的本地电脑上按预期工作。但是当我将它部署到 heroku 时，它会打印消息：

django.db.utils.ProgrammingError: 关系“core_menuoption”不存在

现在，我对此进行了很多搜索，但没有一个案例与我的相似。我认为我的问题是因为我的模型 MenuOption 是 recusive。这是模型：

class MenuOption(models.Model):
    parent = models.ForeignKey('self', on_delete=models.CASCADE, blank=True, null=True)
    title = models.CharField(max_length=50, unique=True)
    
    ...

如您所见，参数parent 是该模型的外键。所以我认为因为模型尚未创建，django 不知道与哪个模型相关。

我想过可能删除这个字段，迁移然后把它带回来，但是太多的东西依赖这个字段。

完整的追溯：

remote: Traceback (most recent call last):
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/db/backends/utils.py", line 84, in _execute
remote:     return self.cursor.execute(sql, params)
remote: psycopg2.errors.UndefinedTable: relation "core_menuoption" does not exist
remote: LINE 1: ...tion"."parent_id", "core_menuoption"."title" FROM "core_menu...
remote:                                                              ^
remote:
remote:
remote: The above exception was the direct cause of the following exception:
remote:
remote: Traceback (most recent call last):
remote:   File "/app/manage.py", line 22, in <module>
remote:     main()
remote:   File "/app/manage.py", line 18, in main
remote:     execute_from_command_line(sys.argv)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/core/management/__init__.py", line 419, in execute_from_command_line
remote:     utility.execute()
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/core/management/__init__.py", line 413, in execute
remote:     self.fetch_command(subcommand).run_from_argv(self.argv)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/core/management/base.py", line 354, in run_from_argv
remote:     self.execute(*args, **cmd_options)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/core/management/base.py", line 398, in execute
remote:     output = self.handle(*args, **options)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/core/management/base.py", line 89, in wrapped
remote:     res = handle_func(*args, **kwargs)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/core/management/commands/migrate.py", line 75, in handle
remote:     self.check(databases=[database])
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/core/management/base.py", line 419, in check
remote:     all_issues = checks.run_checks(
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/core/checks/registry.py", line 76, in run_checks
remote:     new_errors = check(app_configs=app_configs, databases=databases)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/core/checks/urls.py", line 40, in check_url_namespaces_unique
remote:     all_namespaces = _load_all_namespaces(resolver)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/core/checks/urls.py", line 57, in _load_all_namespaces
remote:     url_patterns = getattr(resolver, 'url_patterns', [])
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/utils/functional.py", line 48, in __get__
remote:     res = instance.__dict__[self.name] = self.func(instance)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/urls/resolvers.py", line 598, in url_patterns
remote:     patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/utils/functional.py", line 48, in __get__
remote:     res = instance.__dict__[self.name] = self.func(instance)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/urls/resolvers.py", line 591, in urlconf_module
remote:     return import_module(self.urlconf_name)
remote:   File "/app/.heroku/python/lib/python3.9/importlib/__init__.py", line 127, in import_module
remote:     return _bootstrap._gcd_import(name[level:], package, level)
remote:   File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
remote:   File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
remote:   File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
remote:   File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
remote:   File "<frozen importlib._bootstrap_external>", line 855, in exec_module
remote:   File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
remote:   File "/app/ExplosiveArea/urls.py", line 20, in <module>
remote:     path('', include('core.urls')),
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/urls/conf.py", line 34, in include
remote:     urlconf_module = import_module(urlconf_module)
remote:   File "/app/.heroku/python/lib/python3.9/importlib/__init__.py", line 127, in import_module
remote:     return _bootstrap._gcd_import(name[level:], package, level)
remote:   File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
remote:   File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
remote:   File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
remote:   File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
remote:   File "<frozen importlib._bootstrap_external>", line 855, in exec_module
remote:   File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
remote:   File "/app/core/urls.py", line 3, in <module>
remote:     from . import views
remote:   File "/app/core/views.py", line 11, in <module>
remote:     from core.forms import UserForm, MenuOptionForm, ExerciseForm
remote:   File "/app/core/forms.py", line 20, in <module>
remote:     class MenuOptionForm(forms.ModelForm):
remote:   File "/app/core/forms.py", line 21, in MenuOptionForm
remote:     class Meta:
remote:   File "/app/core/forms.py", line 25, in Meta
remote:     'parent': forms.Select(attrs={'class': 'form-control mb-1'}, choices=[(m, m) for m in MenuOption.objects.all()]),
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/db/models/query.py", line 280, in __iter__
remote:     self._fetch_all()
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/db/models/query.py", line 1324, in _fetch_all
remote:     self._result_cache = list(self._iterable_class(self))
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/db/models/query.py", line 51, in __iter__
remote:     results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/db/models/sql/compiler.py", line 1175, in execute_sql
remote:     cursor.execute(sql, params)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/db/backends/utils.py", line 66, in execute
remote:     return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/db/backends/utils.py", line 75, in _execute_with_wrappers
remote:     return executor(sql, params, many, context)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/db/backends/utils.py", line 84, in _execute
remote:     return self.cursor.execute(sql, params)
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/db/utils.py", line 90, in __exit__
remote:     raise dj_exc_value.with_traceback(traceback) from exc_value
remote:   File "/app/.heroku/python/lib/python3.9/site-packages/django/db/backends/utils.py", line 84, in _execute
remote:     return self.cursor.execute(sql, params)
remote: django.db.utils.ProgrammingError: relation "core_menuoption" does not exist
remote: LINE 1: ...tion"."parent_id", "core_menuoption"."title" FROM "core_menu...

MenuOptionForm 类：

class MenuOptionForm(forms.ModelForm):
    class Meta:
        model = MenuOption
        fields = ('parent', 'title')
        widgets = {
            'parent': forms.Select(attrs={'class': 'form-control mb-1'}, choices=[(m, m) for m in MenuOption.objects.all()]),
            'title': forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'title})
        }

【问题讨论】：

你在 heroku 上运行了migrate 吗？您的迁移是否已添加到您的版本控制中？
@AbdulAzizBarkat 是的，我在 heroku 上做了migrate。将我的迁移添加到版本控制是什么意思？我之前已经将 django 项目上传到 heroku，除了运行它们之外，我从未对迁移做过任何事情。
你是怎么做到的？ edit你的问题。还将 full 错误回溯添加到问题中。通过将迁移添加到版本控制，我的意思是您的迁移文件应该提交到您的 git 存储库。
@AbdulAzizBarkat 是的，它在版本控制中。我添加了完整的回溯。
在core/forms.py中显示类MenuOptionForm

标签： python django heroku psycopg2

【解决方案1】：

在@AbdulAzizBarkat 的帮助下，我发现问题出在 MenuOptionForm 类中。我试图将 MenuOption 类的所有对象附加到选项中，但该类未迁移。所以我将选择列表更改为：

...
'parent': forms.Select(attrs={'class': 'form-control mb-1'}, choices=["1","2","3"]),
...

heroku 可以为我创建表格，然后我将其更改回来，一切正常！

【讨论】：

不要在小部件中指定选项，ModelChoiceField 会自行处理。见我上面的回答。

【解决方案2】：

问题是您的迁移从未被应用，事实上，当您在服务器上运行 migrate 时，您应该得到同样的错误。这里的问题是您有以下行：

'parent': forms.Select(attrs={'class': 'form-control mb-1'}, choices=[(m, m) for m in MenuOption.objects.all()]),

这一行自然会查询数据库，那有什么问题呢？此行在创建类 MenuOptionForm 时执行，这甚至发生在 migrate 之前（因此错误，甚至还没有发生迁移）实际运行，因为在此之前导入了所有文件。另一个问题是，除非您重新加载服务器，否则您在此表单中的选项将永远不会改变，这可能不是您打算发生的。

您需要做的是不在此处传递选项，由于您没有手动指定表单字段，因此此处使用的字段是ModelChoiceField，它将负责通过以下方式设置选项本身：

class MenuOptionForm(forms.ModelForm):
    class Meta:
        model = MenuOption
        fields = ('parent', 'title')
        widgets = {
            'parent': forms.Select(attrs={'class': 'form-control mb-1'}),
            'title': forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'title})
        }

现在我们需要将更改迁移到数据库，首先确保您的迁移已提交到您的存储库，并且提交已推送到 heroku。接下来，如果您使用 Heroku CLI，那么您可以简单地运行：

heroku run python manage.py migrate

【讨论】：