python - OperationError：无法保存文档（LEFT_SUBFIELD 仅支持 Object：ancestors.0 而不是：7）

Question

我在 MongoDB 中有一个组织数据库。我正在尝试使用mongoengine. 我正在使用Djnago服务器。当我创建对象时，它工作正常，但在编辑后它给出了一些错误。

class Organization(Document):
    username= StringField()
    ancestors = ListField(ReferenceField('Organization',dbref=False), default = list)
    parents = ListField(ReferenceField('Organization',dbref=False),default = list)
    descendants = ListField(ReferenceField('Organization',dbref=False), default = list)


obj1 = Organization(username = 'kousik')
obj1.save()
<Organization: Organization object> #obj1 created

obj2 = Organization(username = 'chowdhury',ancestors = [obj1],parents=[obj1])
obj2.save()
<Organization: Organization object> #obj2 created

obj3 = Organization(username = 'kchowdhury',ancestors = [obj1,obj2],parents=[obj2])
obj3.save()
<Organization: Organization object> #obj3 creaed

obj1.descendants = [obj2,obj3]
obj1.save()
<Organization: Organization object> #obj1 updated

obj2.descendants = [obj3]
obj2.save()

Traceback (most recent call last):
  File "<pyshell#43>", line 1, in <module>
    obj2.save()
  File "C:\Python27\lib\site-packages\mongoengine\document.py", line 267, in save
    raise OperationError(message % unicode(err))
OperationError: Could not save document (LEFT_SUBFIELD only supports Object: ancestors.0 not: 7)

Answer 1

这是 mongoengine 错误。我为此创建了问题：https ://github.com/MongoEngine/mongoengine/issues/422 。

目前解决方案：

1. 在更新之前使用完整的重新加载文档（只是reload不工作，因为留下参考）：

   obj1 = Organization.objects(username=obj1.username).first()
   obj1.descendants = [obj2, obj3]
   obj1.save()
   
   
   obj2 = Organization.objects(username=obj2.username).first()
   obj2.descendants = [obj3]
   obj2.save()
   

2. 请改用原子更新save。

3. 用于to_dbref参考：

   obj1 = Organization(username='kousik')
   print obj1.save()
   # <Organization: Organization object> #obj1 created
   
   obj2 = Organization(username='chowdhury', ancestors=[obj1.to_dbref()], parents=[obj1.to_dbref()])
   print obj2.save()
   # <Organization: Organization object> #obj2 created
   
   obj3 = Organization(username='kchowdhury', ancestors=[obj1.to_dbref(), obj2.to_dbref()], parents=[obj2.to_dbref()])
   print obj3.save()
   # <Organization: Organization object> #obj3 creaed
   
   obj1.descendants = [obj2.to_dbref(), obj3.to_dbref()]
   print obj1.save()
   # <Organization: Organization object> #obj1 updated
   
   obj2.descendants = [obj3.to_dbref()]
   print obj2.save()
   # <Organization: Organization object> #obj2 updated