Question

由于某种原因，我今天无法使用python manage.py dumpdata或从可以下载mysql文件的链接转储数据库。

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

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或其他东西有关。

models.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，最近添加了字段用户，日期时间和注释。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，日期和注释时。客户端表显示user_id，datetime和note有Null值（这就是我想要的）。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

你需要告诉Django它应该在最近添加的字段上允许NULL值。它只查看字段定义，它不从数据库中获取模式。

当客户端没有关联用户并且访问self.field.rel.to.DoesNotExist时，很可能会引发client.user错误。这是因为默认情况下所有字段都是必需的。如果您更改模型定义，如下所示，错误应该消失。

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NULL字段上的None值。
blank=True允许您以模型形式将字段留空（例如，在管理员中）。

（blank和null默认为False）

执行dumpdata时，疑难解答“错误：无法序列化数据库：”

1 个答案: