Question

使用SQLAlchemy ORM获取属于某个用户的角色但是收到以下错误

无法确定父/子表之间的连接条件关系AppRole.users - 有多个外键路径通过辅助表'app_user_role'链接表。指定 'foreign_keys'参数，提供那些列的列表应被视为包含来自的外键引用每个父表和子表的辅助表。

表格定义为：

class AppUserRole(Base_Write):
    __tablename__ = 'app_user_role'
    id = Column(Integer, primary_key=True)
    created_at = Column(DateTime, server_default=text('NOW()'), nullable=False)
    created_by = Column(Integer, ForeignKey('app_user.id'), nullable=False)
    is_deleted = Column(Boolean, server_default='0', nullable=False)
    date_deleted = Column(DateTime)
    deleted_by = Column(Integer, ForeignKey('app_user.id'))
    user_id = Column(Integer, ForeignKey('app_user.id'), nullable=False)
    role_id = Column(Integer, ForeignKey('app_role.id'), nullable=False)
    date_assigned = Column(DateTime, nullable=False)


class AppRole(Base_Write):
    __tablename__ = 'app_role'
    id = Column(Integer, primary_key=True)
    created_at = Column(DateTime, server_default=text('NOW()'), nullable=False)
    created_by = Column(Integer)
    is_deleted = Column(Boolean, server_default='0', nullable=False)
    date_deleted = Column(DateTime)
    deleted_by = Column(Integer, ForeignKey('app_user.id'))
    role_classification_id = Column(Integer, ForeignKey('app_role_classification.id'), nullable=False)
    role_code = Column(String(10), nullable=False, unique=True)
    role_name = Column(String(30), nullable=False)

    users = relationship("AppUser", secondary="app_user_role", back_populates="app_role")


class AppUser(Base_Write):
    __tablename__ = 'app_user'
    id = Column(Integer, primary_key=True)
    created_at = Column(DateTime, server_default=text('NOW()'), nullable=False)
    created_by = Column(Integer, ForeignKey('app_user.id'), nullable=False)
    is_deleted = Column(Boolean, server_default='0', nullable=False)
    date_deleted = Column(DateTime)
    deleted_by = Column(Integer, ForeignKey('app_user.id'))
    username = Column(String(50), nullable=False, unique=True)

    roles = relationship("AppRole", secondary="app_user_role", back_populates="app_user")

正在运行的查询是：

for app_user in session.query(AppUser).\
filter(AppUser.is_deleted == False).filter(AppUser.id == user_id):
    #print the names of the roles assigned
    print(app_user.roles.role_name)

问题是，我有其他表格，我已经定义了其他多对多关系参数，一切正常。虽然我不断收到这个错误。在这里还有其他类似的问题，但尝试了不同的建议，但没有运气。我已经尝试通过建议的错误并使用我之前的问题here on SO，但即使放置foreign_keys选项似乎也不起作用，虽然我必须承认我真的在猜测放在哪里。

SQLAlchemy version == 1.0.12，Postgresql 9.5

Answer 1

正如错误消息所示，您有多个外键将AppRole与AppUser相关联，即AppUserRole.user_id，AppUserRole.deleted_by和AppUserRole.created_by，所以你需要指定foreign_keys参数：

class AppRole(Base):
    ...
    users = relationship("AppUser", secondary="app_user_role", 
                         foreign_keys=[AppUserRole.user_id, AppUserRole.role_id],
                         back_populates="roles")


class AppUser(Base):
    ...
    roles = relationship("AppRole", secondary="app_user_role",
                         foreign_keys=[AppUserRole.user_id, AppUserRole.role_id],
                         back_populates="users")

SQLAlchemy多对多关系参数

1 个答案: