Django syncdb 错误

Question

我在我的安装应用里有django.contrib.auth，之前一切都运行得很好，大约10分钟前还没问题。因为我在使用south迁移时遇到了一些麻烦，所以我删除了现有的数据库。当我尝试重新建立数据库时，出现了一个错误。

错误信息：django.db.utils.DatabaseError: 没有这个表：auth_user

Traceback (most recent call last):
  File "manage.py", line 11, in <module>
    execute_manager(settings)
  File "/usr/lib/python2.7/site-packages/django/core/management/__init__.py", line 438, in execute_manager
    utility.execute()
  File "/usr/lib/python2.7/site-packages/django/core/management/__init__.py", line 379, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/lib/python2.7/site-packages/django/core/management/base.py", line 191, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/lib/python2.7/site-packages/django/core/management/base.py", line 219, in execute
    self.validate()
  File "/usr/lib/python2.7/site-packages/django/core/management/base.py", line 249, in validate
    num_errors = get_validation_errors(s, app)
  File "/usr/lib/python2.7/site-packages/django/core/management/validation.py", line 35, in get_validation_errors
    for (app_name, error) in get_app_errors().items():
  File "/usr/lib/python2.7/site-packages/django/db/models/loading.py", line 146, in get_app_errors
    self._populate()
  File "/usr/lib/python2.7/site-packages/django/db/models/loading.py", line 61, in _populate
    self.load_app(app_name, True)
  File "/usr/lib/python2.7/site-packages/django/db/models/loading.py", line 78, in load_app
    models = import_module('.models', app_name)
  File "/usr/lib/python2.7/site-packages/django/utils/importlib.py", line 35, in import_module
    __import__(name)
  File "/home/bruk/workspace/hungryDroid/src/hungryDroid/Ingredient/models.py", line 22, in <module>
    class Ingredient(models.Model):
  File "/home/bruk/workspace/hungryDroid/src/hungryDroid/Ingredient/models.py", line 26, in Ingredient
    FKowner = models.ForeignKey(User, default=User.objects.get(pk=1).id)
  File "/usr/lib/python2.7/site-packages/django/db/models/manager.py", line 132, in get
    return self.get_query_set().get(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/django/db/models/query.py", line 342, in get
    num = len(clone)
  File "/usr/lib/python2.7/site-packages/django/db/models/query.py", line 80, in __len__
    self._result_cache = list(self.iterator())
  File "/usr/lib/python2.7/site-packages/django/db/models/query.py", line 271, in iterator
    for row in compiler.results_iter():
  File "/usr/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 677, in results_iter
    for rows in self.execute_sql(MULTI):
  File "/usr/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 732, in execute_sql
    cursor.execute(sql, params)
  File "/usr/lib/python2.7/site-packages/django/db/backends/util.py", line 15, in execute
    return self.cursor.execute(sql, params)
  File "/usr/lib/python2.7/site-packages/django/db/backends/sqlite3/base.py", line 200, in execute
    return Database.Cursor.execute(self, query, params)
**django.db.utils.DatabaseError: no such table: auth_user**

Answer 1

问题在于你正在对用户模型进行查询

  File "/home/bruk/workspace/hungryDroid/src/hungryDroid/Ingredient/models.py", line 26, in Ingredient
FKowner = models.ForeignKey(User, default=User.objects.get(pk=1).id)

这个查询是在同步数据库的过程中进行的（实际上是在字段声明的时候，所以每次你的模块被导入时，比如在这个验证过程中）。

这样可以确保在创建auth_user表之前，auth_user查询就已经执行了。

要安全地使用默认用户的功能，可以这样做

def get_default_user():
    return User.objects.get(pk=1)

然后在你的字段声明中，做如下操作

FKowner = models.ForeignKey(User, default=get_default_user)

根据模型字段参考，默认值可以是一个可调用的函数。请注意，如果你在这里使用get_default_user()，你会遇到同样的问题——那样的话，它会立即执行，而不是按需执行。