MongoEngine DynamicDocument中的DictField问题
MongoEngine DynamicDocument中的DictField问题
提问于 2016-04-27 07:58:48
我的问题与Bountysource上的这篇文章相匹配：
我的工作场所使用PyMongo 2.6.3/MongoEngine 0.8.7已经有一段时间了，我们正在考虑升级到PyMongo 3.2.2/MongoEngine 0.10.6。我下载了这些版本并开始测试它们。我开始遇到一个基于使用DictFields的DynamicDocuments的类的问题。
14:20:20 ERROR nas.data.sync Traceback (most recent call last):
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/nas/data/sync.py", line 1484, in main
14:20:20 ERROR nas.data.sync result = funct(external, syncRecord)
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/nas/data/sync.py", line 456, in syncAsset
14:20:20 ERROR nas.data.sync success = scheduleUpdate(asset, v) and success
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/nas/data/sync.py", line 299, in scheduleUpdate
14:20:20 ERROR nas.data.sync for wu in workunits:
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/auxiliary/__all/MongoEngine-0.10.6/mongoengine/queryset/queryset.py", line 80, in _iter_results
14:20:20 ERROR nas.data.sync self._populate_cache()
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/auxiliary/__all/MongoEngine-0.10.6/mongoengine/queryset/queryset.py", line 92, in _populate_cache
14:20:20 ERROR nas.data.sync self._result_cache.append(self.next())
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/auxiliary/__all/MongoEngine-0.10.6/mongoengine/queryset/base.py", line 1407, in next
14:20:20 ERROR nas.data.sync raw_doc = self._cursor.next()
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/auxiliary/__all/MongoEngine-0.10.6/mongoengine/queryset/base.py", line 1481, in _cursor
14:20:20 ERROR nas.data.sync self._cursor_obj = self._collection.find(self._query,
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/auxiliary/__all/MongoEngine-0.10.6/mongoengine/queryset/base.py", line 1515, in _query
14:20:20 ERROR nas.data.sync self._mongo_query = self._query_obj.to_query(self._document)
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/auxiliary/__all/MongoEngine-0.10.6/mongoengine/queryset/visitor.py", line 90, in to_query
14:20:20 ERROR nas.data.sync query = query.accept(QueryCompilerVisitor(document))
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/auxiliary/__all/MongoEngine-0.10.6/mongoengine/queryset/visitor.py", line 155, in accept
14:20:20 ERROR nas.data.sync return visitor.visit_query(self)
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/auxiliary/__all/MongoEngine-0.10.6/mongoengine/queryset/visitor.py", line 78, in visit_query
14:20:20 ERROR nas.data.sync return transform.query(self.document, **query.query)
14:20:20 ERROR nas.data.sync File "E:/alpha_maya_pyside/auxiliary/__all/MongoEngine-0.10.6/mongoengine/queryset/transform.py", line 61, in query
14:20:20 ERROR nas.data.sync raise InvalidQueryError(e)
14:20:20 ERROR nas.data.sync InvalidQueryError: 'DictField' object has no attribute 'document_type'
14:20:20 ERROR nas.data.sync sync failed让类从Document继承而不是从DynamicDocument继承确实解决了这个问题。我一直在钻研MongoEngine的源代码，但没有什么能真正引起我的注意。我唯一的猜测是MongoEngine可能在将DynamicField转换为DictField时遇到了问题。
我添加了一个print语句MongoEngine-0.10.6/mongoengine/queryset/transform.py：
try:
fields = _doc_cls._lookup_field(parts)
print fields
except Exception, e:
raise InvalidQueryError(e)在出现错误消息之前，我得到了以下输出：
[<mongoengine.fields.DynamicField object at 0x00000000048B48D0>]回答 1
Stack Overflow用户
发布于 2016-04-28 09:25:18
我进入mongoengine/base/document.py并签出了__lookup_field函数。在该函数内部有一个相当长的if/else语句。以下是一段摘录。
if field is None:
# Look up first field from the document
if field_name == 'pk':
# Deal with "primary key" alias
field_name = cls._meta['id_field']
if field_name in cls._fields:
field = cls._fields[field_name]
elif cls._dynamic:
field = DynamicField(db_field=field_name)
elif cls._meta.get("allow_inheritance", False) or cls._meta.get("abstract", False):
# 744: in case the field is defined in a subclass
for subcls in cls.__subclasses__():
try:
field = subcls._lookup_field([field_name])[0]
except LookUpError:
continue
if field is not None:
break
else:
raise LookUpError('Cannot resolve field "%s"' % field_name)
else:
raise LookUpError('Cannot resolve field "%s"'
% field_name)
else:
ReferenceField = _import_class('ReferenceField')
GenericReferenceField = _import_class('GenericReferenceField')
if isinstance(field, (ReferenceField, GenericReferenceField)):
raise LookUpError('Cannot perform join in mongoDB: %s' %
'__'.join(parts))
if hasattr(getattr(field, 'field', None), 'lookup_member'):
new_field = field.field.lookup_member(field_name)
elif cls._dynamic and (isinstance(field, DynamicField) or
getattr(getattr(field, 'document_type'), '_dynamic')):
new_field = DynamicField(db_field=field_name)如果运行查询并使用StringField，那么变量field仍然是None。但是，如果使用DictField运行查询，则会将field设置为类似于<mongoengine.fields.DictField object at 0x0000000004506CF8>的值。我不知道field是如何设置为这个值的。无论如何，如果您正在查询的类恰好是一个DynamicDocument，那么您将被送到循环的这一部分。
elif cls._dynamic and (isinstance(field, DynamicField) or
getattr(getattr(field, 'document_type'), '_dynamic')):
new_field = DynamicField(db_field=field_name)我是通过消除的过程得出这个结论的。基本上，我找出了我不想去的地方。正如您所看到的，由于DictField不是DynamicField，因此将向其查询document_type属性。DictField不具有导致InvalidQueryError的该属性。
看起来现在的解决方案是不要在DynamicDocuments中使用DictFields，或者看看是否可以在DynamicDocument中使用EmbeddedDocumentField、EmbeddedDocumentListField或ReferenceField。也许这就是开发人员的意图？
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/36877900
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