mysql - 执行转储数据时出现 "Error: Unable to serialize database:"故障排除

Question

由于某些原因，今天我无法使用 python manage.py dumpdata 或从可以下载 mysql 文件的链接转储我的数据库。

我尝试使用 python manage.py dumpdata --traceback，这是我掌握的信息。

Traceback (most recent call last):
  File "manage.py", line 11, in <module>
    execute_manager(settings)
  File "/usr/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 438, in execute_manager
    utility.execute()
  File "/usr/local/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/local/lib/python2.7/site-packages/django/core/management/base.py", line 191, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/local/lib/python2.7/site-packages/django/core/management/base.py", line 220, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/site-packages/django/core/management/commands/dumpdata.py", line 114, in handle
    use_natural_keys=use_natural_keys)
  File "/usr/local/lib/python2.7/site-packages/django/core/serializers/__init__.py", line 91, in serialize
    s.serialize(queryset, **options)
  File "/usr/local/lib/python2.7/site-packages/django/core/serializers/base.py", line 48, in serialize
    self.handle_fk_field(obj, field)
  File "/usr/local/lib/python2.7/site-packages/django/core/serializers/python.py", line 48, in handle_fk_field
    related = getattr(obj, field.name)
  File "/usr/local/lib/python2.7/site-packages/django/db/models/fields/related.py", line 301, in __get__
    raise self.field.rel.to.DoesNotExist
django.contrib.auth.models.DoesNotExist

它说 django.contrib.auth.models.DoesNotExist。我想知道它是否与外键有关。

模型.py

class Client(models.Model):
    name = models.CharField(max_length = 40)
    telephone = models.CharField(max_length = 20)
    website = models.URLField(verify_exists = False)
    fax = models.CharField(max_length = 20)
    email = models.EmailField()
    is_active = models.BooleanField()
    user  = models.ForeignKey(User)
    datetime = models.DateTimeField(default=datetime.now)
    note = models.TextField()
    def __unicode__(self):
        return self.name

从我的 models.py 中，字段 user、datetime 和 note 是最近添加的。现在，如果对于客户端，这些字段中的任何一个都没有值，即空白，我将收到错误 Unable to serialize database。

当我在 mysql 中查找用户、日期时间和注释时。 Client 表显示 user_id、datetime 和 note 具有 Null 值(这是我想要的)。为什么它不允许 Null 值？

+-----------+--------------+------+-----+---------+----------------+| Field     | Type         | Null | Key | Default | Extra          |+-----------+--------------+------+-----+---------+----------------+| id        | int(11)      | NO   | PRI | NULL    | auto_increment | | name      | varchar(40)  | NO   |     | NULL    |                | | telephone | varchar(20)  | NO   |     | NULL    |                | | website   | varchar(200) | NO   |     | NULL    |                | | fax       | varchar(20)  | NO   |     | NULL    |                | | email     | varchar(75)  | NO   |     | NULL    |                | | is_active | tinyint(1)   | NO   |     | NULL    |                | | user_id   | int(11)      | YES  | MUL | NULL    |                | | datetime  | datetime     | YES  |     | NULL    |                | | note      | longtext     | YES  |     | NULL    |                | +-----------+--------------+------+-----+---------+----------------+

Answer 1

您需要告诉 Django 它应该允许在那些最近添加的字段上使用 NULL 值。它只查看字段定义，不从数据库中获取架构。

self.field.rel.to.DoesNotExist 错误最有可能在客户端没有关联用户且访问 client.user 时出现。这是因为默认情况下所有字段都是必需的。如果您如下所示更改模型定义，错误应该会消失。

class Client(models.Model):
    # ...
    user  = models.ForeignKey(User, 
                             null=True, blank=True) 
    datetime = models.DateTimeField(default=datetime.now,
                             null=True, blank=True)
    note = models.TextField(null=True, blank=True)

• null=True 分别允许字段上的 NULL None 值。
• blank=True 允许您在模型表单中将字段留空(例如，在管理员中)。

(blank 和 null 默认都是 False)