将数据库引擎更改为 MySQL。现在 Django 不创建表

Question

我有一个带有标准 sqlite3 数据库的 Django 应用程序。现在我想使用 MySQL。所以我把我的DATABASES改成了settings.py，效果很好，但是我不能运行服务器，因为它说

django.db.utils.InternalError: (1049, "Unknown database 'django'")

所以我在客户端创建了这个数据库，现在它说

django.db.utils.ProgrammingError: (1146, "Table 'django.Cat' doesn't exist")

似乎我必须自己创建所有表格，这是我能做的最糟糕的变体。

#settings.py
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'OPTIONS': {
            'read_default_file': '/path/to/db.conf',
        },
    }
}

和

#conf.db
[client]
database = django
host = localhost
user = DjangoUser
password = password_you_cant_guess
default-character-set = utf8

如何让 Django 创建我拥有的所有表？

我什至不能用任何命令运行python3 manage.py，因为它给了我这个例外。

追溯：

Traceback (most recent call last):
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 86, in _execute
    return self.cursor.execute(sql, params)
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/backends/mysql/base.py", line 74, in execute
    return self.cursor.execute(query, args)
  File "/path/to/project/venv/lib/python3.6/site-packages/MySQLdb/cursors.py", line 209, in execute
    res = self._query(query)
  File "/path/to/project/venv/lib/python3.6/site-packages/MySQLdb/cursors.py", line 315, in _query
    db.query(q)
  File "/path/to/project/venv/lib/python3.6/site-packages/MySQLdb/connections.py", line 239, in query
    _mysql.connection.query(self, query)
MySQLdb._exceptions.ProgrammingError: (1146, "Table 'django.Cat' doesn't exist")

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

Traceback (most recent call last):
  File "manage.py", line 21, in <module>
    main()
  File "manage.py", line 17, in main
    execute_from_command_line(sys.argv)
  File "/path/to/project/venv/lib/python3.6/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "/path/to/project/venv/lib/python3.6/site-packages/django/core/management/__init__.py", line 377, in execute
    django.setup()
  File "/path/to/project/venv/lib/python3.6/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/path/to/project/venv/lib/python3.6/site-packages/django/apps/registry.py", line 122, in populate
    app_config.ready()
  File "/path/to/project/External/apps.py", line 13, in ready
    active_cats = list(Cat.objects.filter(active_cat=True).all())
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/models/query.py", line 276, in __iter__
    self._fetch_all()
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/models/query.py", line 1261, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/models/query.py", line 57, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/models/sql/compiler.py", line 1151, in execute_sql
    cursor.execute(sql, params)
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 100, in execute
    return super().execute(sql, params)
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 68, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 77, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 86, in _execute
    return self.cursor.execute(sql, params)
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 86, in _execute
    return self.cursor.execute(sql, params)
  File "/path/to/project/venv/lib/python3.6/site-packages/django/db/backends/mysql/base.py", line 74, in execute
    return self.cursor.execute(query, args)
  File "/path/to/project/venv/lib/python3.6/site-packages/MySQLdb/cursors.py", line 209, in execute
    res = self._query(query)
  File "/path/to/project/venv/lib/python3.6/site-packages/MySQLdb/cursors.py", line 315, in _query
    db.query(q)
  File "/path/to/project/venv/lib/python3.6/site-packages/MySQLdb/connections.py", line 239, in query
    _mysql.connection.query(self, query)
django.db.utils.ProgrammingError: (1146, "Table 'django.Cat' doesn't exist")

Answer 1

你的问题在这里：

File "/path/to/project/External/apps.py", line 13, in ready
    active_cats = list(Cat.objects.filter(active_cat=True).all())

此代码作为初始化过程的一部分执行。这就是阻止您执行任何管理命令的原因。注意this is documented with a very clear warning:

警告

虽然您可以如上所述访问模型类，但避免 在您的 ready() 实现中与数据库交互。这 包括执行查询的模型方法（save()、delete()、manager 方法等），以及通过 django.db.connection 进行的原始 SQL 查询。您的 ready() 方法将在每个管理命令启动期间运行。 例如，即使测试数据库配置是分开的 从生产设置中，manage.py test 仍然会执行一些 针对生产数据库的查询！