SQLAlchemy與association_proxy問題的關係

Question

我一直在通過很多網站瀏覽以試圖瞭解發生了什麼，但我真的需要一些直接幫助。如果我錯過了文檔中顯而易見的內容，我很抱歉。

這裏就是我想要做的（我已經切出一切，但基本代碼）：

Base = declarative_base() 

class User(Base): 
    __tablename__ = 'user' 
    login = Column(String(60), primary_key=True, nullable=False) 

    groups = association_proxy('user_to_groups', 'group', creator=lambda group: UserToGroup(group_name=group.name)) 

    def __init__(self, login, groups=None): 
     self.login = login 
     if groups: 
      for group in groups: 
       self.groups.append(group) 


class Group(Base): 
    __tablename__ = 'group' 
    name = Column(String(100), primary_key=True, nullable=False) 
    description = Column(String(100), nullable=True) 

    users = association_proxy('group_to_user', 'user', creator=lambda user: UserToGroup(user_login=user.login)) 

    def __eq__(self, other): 
     return self.name == other.name 


class UserToGroup(Base): 
    __tablename__ = 'user_to_group' 
    user_login = Column(String(60), ForeignKey(User.login), primary_key=true) 
    group_name = Column(String(100), ForeignKey(Group.name), primary_key=true) 

    user = relationship(User, backref='user_to_groups', cascade='all') #, cascade="all, delete" #, delete-orphan ? 
    group = relationship(Group, backref='group_to_user', cascade='all') #, cascade="all, delete" #, delete-orphan ? 


group1 = Group(name ="g:superadmin") 
group2 = Group(name ="g:admin") 
session.add_all([group1, group2]) 
session.flush() 
user1 = User(login = "test", groups=[group1, group2]) 
session.add(user1) 
session.flush() 


user1 = session.query(User).filter(User.login=='test').one() 
print(user1.user_to_groups) 
print(type(user1.groups), dir(user1.groups)) 
user1.groups.remove(Group(name='g:admin')) 

而這裏的響應回溯試圖運行user1.groups.remove(Group(name='g:admin'))後：

AssertionError: Dependency rule tried to blank-out primary key column 'user_to_group.user_login' on instance '<UserToGroup at 0x7f33f49bd190>'

我希望它只是刪除user_to_group表中的行並相應地更新對象以反映更改。

我有它當關系表沒有映射到一個對象之前的工作，but I need it to be mapped to an object to use inheritance

Answer 1

瀑布從擁有父到子對象被刪除去，所以User.user_to_groups，Group.group_to_user：

class UserToGroup(Base): 
    __tablename__ = 'user_to_group' 
    user_login = Column(String(60), ForeignKey(User.login), primary_key=True) 
    group_name = Column(String(100), ForeignKey(Group.name), primary_key=True) 

    user = relationship(User, backref=backref('user_to_groups', cascade='all, delete-orphan')) 
    group = relationship(Group, backref=backref('group_to_user', cascade='all, delete-orphan'))