我有一个正在运行的Django博客，在我的本地机器上运行sqlite3 db.我想要的是
- 将sqlite3数据库转换为mysql数据库
- 更改Django settings.py文件以服务于MySQL数据库
在我跑进第一步之前，我先跳到了第二步.我关注了this web page(在MacOS上).我在root用户上创建了名为djangolocaldb的数据库，并将这些信息放在/etc/mysql/my.cnf中，如下所示:
# /etc/mysql/my.cnf
[client]
database=djangolocaldb
user=root
password=ROOTPASSWORD
default-character-set=utf8
当然，我创建了db，但没有在其中创建表.
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| djangolocaldb |
| employees |
| information_schema |
| mydatabase |
| mysql |
| performance_schema |
| sys |
+--------------------+
7 rows in set (0.00 sec)
我按照网页上的建议换了settings.py元.以下是操作方法:
# settings.py
...
# Database
# https://docs.djangoproject.com/en/3.0/ref/settings/#databases
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.mysql',
#'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
'OPTIONS' : {
'read_default_file': '/etc/mysql/my.cnf',
}
}
}
...
现在，当我在venv激活的情况下跑python manage.py runserver的时候，我得到了这样一个残酷的回溯(我先跑了python manage.py migrate，回溯看起来几乎是一样的):
(.venv) ➜ django-local-blog git:(master) ✗ python manage.py runserver
Watching for file changes with StatReloader
Exception in thread django-main-thread:
Traceback (most recent call last):
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/MySQLdb/__init__.py", line 18, in <module>
from . import _mysql
ImportError: dlopen(/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/MySQLdb/_mysql.cpython-37m-darwin.so, 2): Library not loaded: @rpath/libmysqlclient.21.dylib
Referenced from: /Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/MySQLdb/_mysql.cpython-37m-darwin.so
Reason: image not found
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/Users/gwanghyeongim/.pyenv/versions/3.7.6/lib/python3.7/threading.py", line 926, in _bootstrap_inner
self.run()
File "/Users/gwanghyeongim/.pyenv/versions/3.7.6/lib/python3.7/threading.py", line 870, in run
self._target(*self._args, **self._kwargs)
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/utils/autoreload.py", line 53, in wrapper
fn(*args, **kwargs)
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/core/management/commands/runserver.py", line 109, in inner_run
autoreload.raise_last_exception()
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/utils/autoreload.py", line 76, in raise_last_exception
raise _exception[1]
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/core/management/__init__.py", line 357, in execute
autoreload.check_errors(django.setup)()
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/utils/autoreload.py", line 53, in wrapper
fn(*args, **kwargs)
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/__init__.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/apps/registry.py", line 114, in populate
app_config.import_models()
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/apps/config.py", line 211, in import_models
self.models_module = import_module(models_module_name)
File "/Users/gwanghyeongim/.pyenv/versions/3.7.6/lib/python3.7/importlib/__init__.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
File "<frozen importlib._bootstrap>", line 983, in _find_and_load
File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 728, in exec_module
File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/contrib/auth/models.py", line 2, in <module>
from django.contrib.auth.base_user import AbstractBaseUser, BaseUserManager
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/contrib/auth/base_user.py", line 47, in <module>
class AbstractBaseUser(models.Model):
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/models/base.py", line 121, in __new__
new_class.add_to_class('_meta', Options(meta, app_label))
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/models/base.py", line 325, in add_to_class
value.contribute_to_class(cls, name)
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/models/options.py", line 208, in contribute_to_class
self.db_table = truncate_name(self.db_table, connection.ops.max_name_length())
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/__init__.py", line 28, in __getattr__
return getattr(connections[DEFAULT_DB_ALIAS], item)
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/utils.py", line 207, in __getitem__
backend = load_backend(db['ENGINE'])
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/utils.py", line 111, in load_backend
return import_module('%s.base' % backend_name)
File "/Users/gwanghyeongim/.pyenv/versions/3.7.6/lib/python3.7/importlib/__init__.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/backends/mysql/base.py", line 16, in <module>
import MySQLdb as Database
File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/MySQLdb/__init__.py", line 24, in <module>
version_info, _mysql.version_info, _mysql.__file__
NameError: name '_mysql' is not defined
所以这NameError: name '_mysql' is not defined就是问题所在.我之前安装了mysqlclient，更改了settings.py，在MySQL中创建了数据库，但这些步骤都没有任何帮助.
我注意到，即使我把我的settings.py改回sqlite3，我的博客也吐出了同样的_mysql not defined error.所以我最终恢复了我的提交，现在我又回到了sqlite3(至少我的博客在运行它).
我猜可能是我没有先转换数据，但我不是百分之百确定.
任何建议都将不胜感激.提前谢谢您！
EDITED on Aug 18, 2020
如果在运行python manage.py migrate时仍然看到_mysql not defined错误，请判断以下两个设置.
- 如果在Python虚拟环境中运行
pip freeze时看到mysqlclient，
(.venv) ➜ SqlDjango git:(master) ✗ pip freeze
...
Django==3.0.8
mysqlclient==2.0.1
...
确保在python虚拟环境中安装了mysqlclient，而不是mysql-client.前者支持python3，而后者支持python2，我认为这可能不是您想要的.
- 确保在bash配置文件中放入以下行(
~/.zshrc代表zsh，~/.bashrc或~/.bash_profile代表bash等)
export DYLD_LIBRARY_PATH=/usr/local/mysql/lib/
之后，通过运行source ~/.your_shell_config_file应用更改.参见python manage.py migrate作品.