django.db.utils.OperationalError 不管我怎么努力
django.db.utils.OperationalError no matter what I try
好吧，我被难住了。我想我已经尝试了一切。
我在应用程序的 models.py 中创建了一个模型，并向现有模型添加了更多字段（均具有默认值）。那我运行makemigrations。结果：
$ python3 manage.py makemigrations
Traceback (most recent call last):
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/sqlite3/base.py", line 323, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.OperationalError: no such column: myapp_MyExistingModel.first_new_field
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 14, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 345, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 348, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 398, in execute
self.check()
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 426, in check
include_deployment_checks=include_deployment_checks,
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/registry.py", line 75, in run_checks
new_errors = check(app_configs=app_configs)
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/urls.py", line 13, in check_url_config
return check_resolver(resolver)
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/urls.py", line 23, in check_resolver
for pattern in resolver.url_patterns:
File "/usr/local/lib/python3.5/dist-packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/usr/local/lib/python3.5/dist-packages/django/core/urlresolvers.py", line 417, in url_patterns
patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
File "/usr/local/lib/python3.5/dist-packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/usr/local/lib/python3.5/dist-packages/django/core/urlresolvers.py", line 410, in urlconf_module
return import_module(self.urlconf_name)
File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 986, in _gcd_import
File "<frozen importlib._bootstrap>", line 969, in _find_and_load
File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 665, in exec_module
File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
File "/path/to/myproject/myproject/urls.py", line 49, in <module>
url(r'^someurl/', include('myapp.urls')),
File "/usr/local/lib/python3.5/dist-packages/django/conf/urls/__init__.py", line 52, in include
urlconf_module = import_module(urlconf_module)
File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 986, in _gcd_import
File "<frozen importlib._bootstrap>", line 969, in _find_and_load
File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 665, in exec_module
File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
File "/path/to/myproject/myapp/urls.py", line 2, in <module>
from . import views
File "/path/to/myproject/myapp/views.py", line 8, in <module>
existing_model = MyExistingModel.objects.all()[0]
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 297, in __getitem__
return list(qs)[0]
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 258, in __iter__
self._fetch_all()
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 1074, in _fetch_all
self._result_cache = list(self.iterator())
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 52, in __iter__
results = compiler.execute_sql()
File "/usr/local/lib/python3.5/dist-packages/django/db/models/sql/compiler.py", line 848, in execute_sql
cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/utils.py", line 95, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/usr/local/lib/python3.5/dist-packages/django/utils/six.py", line 685, in reraise
raise value.with_traceback(tb)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/sqlite3/base.py", line 323, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.OperationalError: no such column: myapp_MyExistingModel.first_new_field
如果重要的话，我正在使用 Mezzanine CMS，而 MyExistingModel 是其 Page class 的扩展。它只有一个实例。
接下来我尝试了以下方法：
manage.py migrate --fakemanage.py flush- 正在重命名我的数据库以便创建一个新数据库
所有这些都抛出相同的回溯。我进入了该应用程序的最后一次迁移。它包含一个用于我的新模型的 AddModel 和一个用于我重命名的旧模型中的字段的 RemoveField，但没有用于我创建的新字段的 AddField。所以我手动将它们添加到迁移文件并重试 manage.py migrate --fake。相同的回溯。我也尝试了所有其他命令。相同的回溯。
最后，我删除了所有应用程序的迁移，只留下 __init__.py。我还重命名了数据库，以便重新创建它。我重试了 flush、makemigrations 和 migrate（有和没有 --fake）。所有这些都导致了这个回溯：
Traceback (most recent call last):
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/sqlite3/base.py", line 323, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.OperationalError: no such table: myapp_MyExistingModel
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 14, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 345, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 348, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 398, in execute
self.check()
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 426, in check
include_deployment_checks=include_deployment_checks,
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/registry.py", line 75, in run_checks
new_errors = check(app_configs=app_configs)
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/urls.py", line 13, in check_url_config
return check_resolver(resolver)
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/urls.py", line 23, in check_resolver
for pattern in resolver.url_patterns:
File "/usr/local/lib/python3.5/dist-packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/usr/local/lib/python3.5/dist-packages/django/core/urlresolvers.py", line 417, in url_patterns
patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
File "/usr/local/lib/python3.5/dist-packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/usr/local/lib/python3.5/dist-packages/django/core/urlresolvers.py", line 410, in urlconf_module
return import_module(self.urlconf_name)
File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 986, in _gcd_import
File "<frozen importlib._bootstrap>", line 969, in _find_and_load
File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 665, in exec_module
File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
File "/path/to/myproject/myproject/urls.py", line 49, in <module>
url(r'^someurl/', include('myapp.urls')),
File "/usr/local/lib/python3.5/dist-packages/django/conf/urls/__init__.py", line 52, in include
urlconf_module = import_module(urlconf_module)
File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 986, in _gcd_import
File "<frozen importlib._bootstrap>", line 969, in _find_and_load
File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 665, in exec_module
File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
File "/path/to/myproject/myapp/urls.py", line 2, in <module>
from . import views
File "/path/to/myproject/myapp/views.py", line 8, in <module>
existing_model = MyExistingModel.objects.all()[0]
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 297, in __getitem__
return list(qs)[0]
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 258, in __iter__
self._fetch_all()
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 1074, in _fetch_all
self._result_cache = list(self.iterator())
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 52, in __iter__
results = compiler.execute_sql()
File "/usr/local/lib/python3.5/dist-packages/django/db/models/sql/compiler.py", line 848, in execute_sql
cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/utils.py", line 95, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/usr/local/lib/python3.5/dist-packages/django/utils/six.py", line 685, in reraise
raise value.with_traceback(tb)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/sqlite3/base.py", line 323, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.OperationalError: no such table: myapp_MyExistingModel
在这一点上，除了 start over，我什至不知道下一步该尝试什么。任何建议表示赞赏。
我想通了！经验教训：阅读整个堆栈跟踪，而不仅仅是最后一行。在这种情况下，攻击线在我的 views.py:
File "/path/to/myproject/myapp/views.py", line 8, in <module>
existing_model = MyExistingModel.objects.all()[0]
就像我说的，MyExistingModel 只有一个实例，这一行将该实例设置为局部变量 existing_model 以便在 views.py 代码中使用。
我还是不明白为什么 makemigrations 需要 运行 views.py。但它确实如此，显然！在这样做时，MyExistingModel 是从 models.py 导入的， 包括 新字段。但这些字段尚未迁移。因此，操作错误。
好吧，我被难住了。我想我已经尝试了一切。
我在应用程序的 models.py 中创建了一个模型，并向现有模型添加了更多字段（均具有默认值）。那我运行makemigrations。结果：
$ python3 manage.py makemigrations
Traceback (most recent call last):
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/sqlite3/base.py", line 323, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.OperationalError: no such column: myapp_MyExistingModel.first_new_field
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 14, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 345, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 348, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 398, in execute
self.check()
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 426, in check
include_deployment_checks=include_deployment_checks,
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/registry.py", line 75, in run_checks
new_errors = check(app_configs=app_configs)
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/urls.py", line 13, in check_url_config
return check_resolver(resolver)
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/urls.py", line 23, in check_resolver
for pattern in resolver.url_patterns:
File "/usr/local/lib/python3.5/dist-packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/usr/local/lib/python3.5/dist-packages/django/core/urlresolvers.py", line 417, in url_patterns
patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
File "/usr/local/lib/python3.5/dist-packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/usr/local/lib/python3.5/dist-packages/django/core/urlresolvers.py", line 410, in urlconf_module
return import_module(self.urlconf_name)
File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 986, in _gcd_import
File "<frozen importlib._bootstrap>", line 969, in _find_and_load
File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 665, in exec_module
File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
File "/path/to/myproject/myproject/urls.py", line 49, in <module>
url(r'^someurl/', include('myapp.urls')),
File "/usr/local/lib/python3.5/dist-packages/django/conf/urls/__init__.py", line 52, in include
urlconf_module = import_module(urlconf_module)
File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 986, in _gcd_import
File "<frozen importlib._bootstrap>", line 969, in _find_and_load
File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 665, in exec_module
File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
File "/path/to/myproject/myapp/urls.py", line 2, in <module>
from . import views
File "/path/to/myproject/myapp/views.py", line 8, in <module>
existing_model = MyExistingModel.objects.all()[0]
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 297, in __getitem__
return list(qs)[0]
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 258, in __iter__
self._fetch_all()
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 1074, in _fetch_all
self._result_cache = list(self.iterator())
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 52, in __iter__
results = compiler.execute_sql()
File "/usr/local/lib/python3.5/dist-packages/django/db/models/sql/compiler.py", line 848, in execute_sql
cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/utils.py", line 95, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/usr/local/lib/python3.5/dist-packages/django/utils/six.py", line 685, in reraise
raise value.with_traceback(tb)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/sqlite3/base.py", line 323, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.OperationalError: no such column: myapp_MyExistingModel.first_new_field
如果重要的话，我正在使用 Mezzanine CMS，而 MyExistingModel 是其 Page class 的扩展。它只有一个实例。
接下来我尝试了以下方法：
manage.py migrate --fakemanage.py flush- 正在重命名我的数据库以便创建一个新数据库
所有这些都抛出相同的回溯。我进入了该应用程序的最后一次迁移。它包含一个用于我的新模型的 AddModel 和一个用于我重命名的旧模型中的字段的 RemoveField，但没有用于我创建的新字段的 AddField。所以我手动将它们添加到迁移文件并重试 manage.py migrate --fake。相同的回溯。我也尝试了所有其他命令。相同的回溯。
最后，我删除了所有应用程序的迁移，只留下 __init__.py。我还重命名了数据库，以便重新创建它。我重试了 flush、makemigrations 和 migrate（有和没有 --fake）。所有这些都导致了这个回溯：
Traceback (most recent call last):
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/sqlite3/base.py", line 323, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.OperationalError: no such table: myapp_MyExistingModel
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 14, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 345, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 348, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 398, in execute
self.check()
File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 426, in check
include_deployment_checks=include_deployment_checks,
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/registry.py", line 75, in run_checks
new_errors = check(app_configs=app_configs)
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/urls.py", line 13, in check_url_config
return check_resolver(resolver)
File "/usr/local/lib/python3.5/dist-packages/django/core/checks/urls.py", line 23, in check_resolver
for pattern in resolver.url_patterns:
File "/usr/local/lib/python3.5/dist-packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/usr/local/lib/python3.5/dist-packages/django/core/urlresolvers.py", line 417, in url_patterns
patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
File "/usr/local/lib/python3.5/dist-packages/django/utils/functional.py", line 33, in __get__
res = instance.__dict__[self.name] = self.func(instance)
File "/usr/local/lib/python3.5/dist-packages/django/core/urlresolvers.py", line 410, in urlconf_module
return import_module(self.urlconf_name)
File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 986, in _gcd_import
File "<frozen importlib._bootstrap>", line 969, in _find_and_load
File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 665, in exec_module
File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
File "/path/to/myproject/myproject/urls.py", line 49, in <module>
url(r'^someurl/', include('myapp.urls')),
File "/usr/local/lib/python3.5/dist-packages/django/conf/urls/__init__.py", line 52, in include
urlconf_module = import_module(urlconf_module)
File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 986, in _gcd_import
File "<frozen importlib._bootstrap>", line 969, in _find_and_load
File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 665, in exec_module
File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
File "/path/to/myproject/myapp/urls.py", line 2, in <module>
from . import views
File "/path/to/myproject/myapp/views.py", line 8, in <module>
existing_model = MyExistingModel.objects.all()[0]
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 297, in __getitem__
return list(qs)[0]
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 258, in __iter__
self._fetch_all()
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 1074, in _fetch_all
self._result_cache = list(self.iterator())
File "/usr/local/lib/python3.5/dist-packages/django/db/models/query.py", line 52, in __iter__
results = compiler.execute_sql()
File "/usr/local/lib/python3.5/dist-packages/django/db/models/sql/compiler.py", line 848, in execute_sql
cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/utils.py", line 95, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/usr/local/lib/python3.5/dist-packages/django/utils/six.py", line 685, in reraise
raise value.with_traceback(tb)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.5/dist-packages/django/db/backends/sqlite3/base.py", line 323, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.OperationalError: no such table: myapp_MyExistingModel
在这一点上，除了 start over，我什至不知道下一步该尝试什么。任何建议表示赞赏。
我想通了！经验教训：阅读整个堆栈跟踪，而不仅仅是最后一行。在这种情况下，攻击线在我的 views.py:
File "/path/to/myproject/myapp/views.py", line 8, in <module>
existing_model = MyExistingModel.objects.all()[0]
就像我说的，MyExistingModel 只有一个实例，这一行将该实例设置为局部变量 existing_model 以便在 views.py 代码中使用。
我还是不明白为什么 makemigrations 需要 运行 views.py。但它确实如此，显然！在这样做时，MyExistingModel 是从 models.py 导入的， 包括 新字段。但这些字段尚未迁移。因此，操作错误。