PyAMF DatabaseError：“数据库不支持此查询。”返回 User 对象时

Question

这是我收到的错误：

ERROR    2011-11-19 04:19:55,441 django.py:164] Error encoding AMF request
Traceback (most recent call last):
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/remoting/gateway/django.py", line 161, in __call__
    logger=self.logger, timezone_offset=timezone_offset)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/remoting/__init__.py", line 676, in encode
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/remoting/__init__.py", line 520, in _write_body
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/remoting/__init__.py", line 486, in _encode_body
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/codec.py", line 499, in writeElement
    func(data)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/amf0.py", line 657, in writeAMF3
    self.context.getAMF3Encoder(self).writeElement(data)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/codec.py", line 499, in writeElement
    func(data)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/amf3.py", line 1456, in writeObject
    self.writeElement(value)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/codec.py", line 499, in writeElement
    func(data)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/amf3.py", line 1298, in writeList
    [self.writeElement(x) for x in n]
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/codec.py", line 499, in writeElement
    func(data)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/codec.py", line 358, in __call__
    ret = self.func(data, encoder=self.encoder)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/adapters/_django_db_models_base.py", line 276, in writeDjangoObject
    encoder.writeObject(referenced_object)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/amf3.py", line 1468, in writeObject
    self.writeElement(value)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/codec.py", line 499, in writeElement
    func(data)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/codec.py", line 358, in __call__
    ret = self.func(data, encoder=self.encoder)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/adapters/_django_db_models_base.py", line 276, in writeDjangoObject
    encoder.writeObject(referenced_object)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/amf3.py", line 1468, in writeObject
    self.writeElement(value)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/codec.py", line 499, in writeElement
    func(data)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/codec.py", line 358, in __call__
    ret = self.func(data, encoder=self.encoder)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/adapters/_django_db_models_base.py", line 276, in writeDjangoObject
    encoder.writeObject(referenced_object)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/amf3.py", line 1447, in writeObject
    attrs = alias.getEncodableAttributes(obj, codec=self)
  File "/Library/Python/2.6/site-packages/PyAMF-0.6.1-py2.6-macosx-10.6-universal.egg/pyamf/adapters/_django_db_models_base.py", line 173, in getEncodableAttributes
    attrs[name] = [x for x in getattr(obj, name).all()]
  File "/Users/bryce/Documents/Aptana Studio 3 Workspace/django-blog/django/db/models/query.py", line 107, in _result_iter
    self._fill_cache()
  File "/Users/bryce/Documents/Aptana Studio 3 Workspace/django-blog/django/db/models/query.py", line 774, in _fill_cache
    self._result_cache.append(self._iter.next())
  File "/Users/bryce/Documents/Aptana Studio 3 Workspace/django-blog/django/db/models/query.py", line 275, in iterator
    for row in compiler.results_iter():
  File "/Users/bryce/Documents/Aptana Studio 3 Workspace/DennysBE/djangotoolbox/db/basecompiler.py", line 225, in results_iter
    self.check_query()
  File "/Users/bryce/Documents/Aptana Studio 3 Workspace/DennysBE/djangotoolbox/db/basecompiler.py", line 273, in check_query
    raise DatabaseError('This query is not supported by the database.')
DatabaseError: This query is not supported by the database.

这是对这个问题很重要的模型：

class ChallengeAct(models.Model):
    challenge = models.ForeignKey(Challenge, blank=True, null=True)
    user = models.ForeignKey(User, blank=True, null=True)
    start_date = models.DateTimeField(blank=True, null=True)
    progress_value = models.IntegerField(default=0)
    earned_coupon = models.ForeignKey(EarnedCoupon, blank=True, null=True)

这是导致错误的方法：

def foo_bar(request):
    user = request.user
    c = ChallengeAct()
    c.challenge = Challenge.objects.get(id=1)
    c.start_date = datetime.now()
    c.progress_value = 1
    c.user = user
    c.save()

#    Here is where I set the user to null to avoid the DatabaseError
    c.user = None
    return [c]

有趣的是我需要设置 c.user = None就在我返回它之前，这样我就不会遇到 DatabaseError: This query is not support by the database. 问题。

--update-- 我想得越多，这似乎是获取用户对象的 pyamf 和 django-nonrel 问题。我猜测当 pyamf 尝试获取用户对象时，它正在使用某种类型的连接查询，而 django-nonrel 不支持这种类型。

这是为什么呢？有办法解决吗？

Answer 1

对于用户模型，您不必允许 blank=True, null=True。通常 django.contrib.auth.models.AnonymousUser 会处理匿名请求。它可能会也可能不会解决问题，但值得尝试，即：

class ChallengeAct(RewardActBase):
    user = models.ForeignKey(User)
    ....