python - 无效请求错误 : Object '' is already attached to session

Question

我得到:

sqlalchemy.exc.InvalidRequestError: Object '<DBEdge at 0x103c4a190>' is already attached to session '1' (this is '2')

在这一行

session.add(edge)

当我尝试运行它时:

  def findOrCreateEdge(self,user1,user2): #user1 is followed by user2
    if user1.id>user2.id:
      user1, user2 = user2, user1
      kind = 2
    else:
      kind = 1
    edge = self.findEdge(user1,user2)
    if edge:
      if edge.kind==1 and kind==2:
        edge.kind = 3
      if edge.kind==2 and kind==1:
        edge.kind = 3
      return edge
    else:
      edge = DBEdge(user1,user2)
      edge.kind = kind
      user1.edge_count = user1.edge_count + 1
      user2.edge_count = user2.edge_count + 1
      #session.save(edge) # we don't flush edges here, because it gives us a huge speedup to do a bunch at once then flush.
      try:
        session.add(edge)
        session.commit()
      except:
        session = Session()
        session.add(edge)
        session.commit()
      return edge

Answer 1

问题在于两次添加边缘，一次添加到第一个 session ，然后在出现异常时添加到第二个 session 。我不知道你到底想在这里实现什么，但如果你调查错误并解决问题，而不是粗暴地将边缘塞入新 session ，会更好。或者，您可能希望回滚之前的 session 并重新启动它，然后向其添加边缘。

在已有 session 的情况下创建新 session 几乎总是错误的(除非上下文本身发生了变化，但这里似乎不是这种情况)。