我还无法找到适用于我的SO解决方案，所以我认为我会提出一个问题。
我遇到了使用django将数据库模式迁移到新的PostgreSQL DB的问题。
这是我第一个数据库的连接，它可以正常工作，并且我能够很好地运行迁移。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将架构迁移。
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]',
}
}
我在第一个连接上运行 python3 manage.py makemigrations ，这很好。
当我使用更新后的数据库名称运行相同的命令时，出现异常，指出我的表不存在。
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...
答案 0 :(得分：2)
回溯告诉您，模块加载时，表单ApartmentTableFormBuilder导致查询Community.objects.all()。
在新数据库上运行migrate或makemigrations时，由于尚未创建objects_community表，因此会导致错误。
正确的解决方案是修改表单，以便在模块加载时不会引起任何查询。黑客解决方案是暂时注释掉引起问题的代码，直到您第一次运行makemigrations和migrate。