SQLAlchemy - ObjectDeletedError：实例'<Class at ...>'已被删除。帮助

Question

我在从数据库中删除行然后添加新行时遇到了一些问题。代码如下：

for positionid in form_result['responsibilities']:
   inputdata = form_result['responsibilities'][positionid]

    self.__deleterow(dbmyaccount.Responsibilities, session['authed']['userid'])

    for resp in (i.strip() for i in inputdata.split(',')):
        resp_q = dbmyaccount.Responsibilities(session['authed']['userid'])

        resp_q.positionid     = positionid
        resp_q.responsibility = resp

        Session.add(resp_q)
        Session.commit()

def __deleterow(self, table, user):       
    delete_q = Session.query(table).filter_by(userid=user).first()

    if delete_q:
        Session.query(table).filter_by(userid=user).delete()
        Session.commit()

基本上，我从表中擦除所有用户数据，然后添加他们的新选项。问题是，代码产生了这个错误：

ObjectDeletedError: Instance '<Responsibilities at ...>' has been deleted.

我不知道为什么...从我的 Google 搜索结果来看，产生了错误，因为我在从数据库中删除了所有数据后修改了 Responsibilities 类。尽管用新数据重新初始化它，但我不知道如何“放手”这个类。

我做错了什么？

编辑

这是责任类：

class Responsibilities(Base):

__tablename__ = 'responsibilities'

id             = Column(Integer, primary_key=True)
userid         = Column(Integer, ForeignKey('users.id'))
positionid     = Column(Integer)
responsibility = Column(String(50))

def __init__(self, user=None):
    if user:
        self.userid = user

def __repr__(self):
    return "<Responsibilities({0})".format(self.userid)

这是回溯：

File '<string>', line 2 in save
File 'C:\\Users\\Dave\\Documents\\Python\\pylons\\mydevenv\\lib\\site-packages\\pylons-1.0-py2.6.egg\\pylons\\decorators\\rest.py', line 33 in check_methods
  return func(*args, **kwargs)
File 'C:\\Users\\Dave\\Documents\\Python\\pylons\\website\\website\\controllers\\myaccount.py', line 260 in save
  self.__deleterow(dbmyaccount.Responsibilities, session['authed']['userid'])
File 'C:\\Users\\Dave\\Documents\\Python\\pylons\\website\\website\\controllers\\myaccount.py', line 210 in __deleterow
  Session.query(table).filter_by(userid=user).delete()
File 'C:\\Users\\Dave\\Documents\\Python\\pylons\\mydevenv\\lib\\site-packages\\sqlalchemy-0.6.3-py2.6.egg\\sqlalchemy\\orm\\query.py', line 2031 in delete
  eval_condition(obj)]
File 'C:\\Users\\Dave\\Documents\\Python\\pylons\\mydevenv\\lib\\site-packages\\sqlalchemy-0.6.3-py2.6.egg\\sqlalchemy\\orm\\evaluator.py', line 82 in evaluate
  left_val = eval_left(obj)
File 'C:\\Users\\Dave\\Documents\\Python\\pylons\\mydevenv\\lib\\site-packages\\sqlalchemy-0.6.3-py2.6.egg\\sqlalchemy\\orm\\evaluator.py', line 42 in <lambda>
  return lambda obj: get_corresponding_attr(obj)
File 'C:\\Users\\Dave\\Documents\\Python\\pylons\\mydevenv\\lib\\site-packages\\sqlalchemy-0.6.3-py2.6.egg\\sqlalchemy\\orm\\attributes.py', line 163 in __get__
  instance_dict(instance))
File 'C:\\Users\\Dave\\Documents\\Python\\pylons\\mydevenv\\lib\\site-packages\\sqlalchemy-0.6.3-py2.6.egg\\sqlalchemy\\orm\\attributes.py', line 382 in get
  value = callable_(passive=passive)
File 'C:\\Users\\Dave\\Documents\\Python\\pylons\\mydevenv\\lib\\site-packages\\sqlalchemy-0.6.3-py2.6.egg\\sqlalchemy\\orm\\state.py', line 280 in __call__
  self.manager.deferred_scalar_loader(self, toload)
File 'C:\\Users\\Dave\\Documents\\Python\\pylons\\mydevenv\\lib\\site-packages\\sqlalchemy-0.6.3-py2.6.egg\\sqlalchemy\\orm\\mapper.py', line 2441 in _load_scalar_attributes
  state_str(state))
ObjectDeletedError: Instance '<Responsibilities at ...>' has been deleted.

Answer 1

当您进行批量删除时，它会从数据库中删除行，但不会更新对 SQLAlchemy 会话中内存中对象的引用。 您可以使用.delete() 的synchronize_session 参数使其同步会话：

Session.query(table).filter_by(userid=user).delete(synchronize_session='fetch')

请参阅文档中的警告：http://docs.sqlalchemy.org/en/rel_1_0/orm/query.html?highlight=query.delete#sqlalchemy.orm.query.Query.delete

Answer 2

您尝试执行的代码是有效的，我想问题出在您的映射器配置上，特别是您的用户-职责关系。您应该做的是为此关系设置正确的cascade 属性，您应该能够按照此处给出的指南 [cascade 项] 为您的数据库模式找出正确的设置： http://www.sqlalchemy.org/docs/orm/relationships.html#the-relationship-api

Answer 3

我在创建测试时遇到了类似的问题。我将关系配置为“级联”，但问题与创建职责有关，还需要填写 user.response。

这是给下一个人的！