Question

我为以下组提供了简化的代码，这些组可以具有具有角色的子组：

Arc<GigabyteMap>

运行此命令时，我得到from sqlalchemy import ( CheckConstraint, Column, ForeignKey, PrimaryKeyConstraint, String, create_engine, ) from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker, relationship Base = declarative_base() class Group(Base): __tablename__ = 'groups' name = Column(String, primary_key=True) group_roles = relationship('GroupRole', back_populates='group') class GroupRole(Base): __tablename__ = 'group_roles' name = Column(String, ForeignKey(Group.name)) group_name = Column(String, ForeignKey(Group.name)) role = Column(String, nullable=False) __table_args__ = ( CheckConstraint('name != group_name'), PrimaryKeyConstraint('name', 'group_name'), ) group = relationship(Group, foreign_keys=[name], back_populates='group_roles') engine = create_engine('sqlite:///:memory:') Base.metadata.create_all(engine) session = sessionmaker(bind=engine)() session.add(Group(name='test'))

我还尝试过在sqlalchemy.exc.AmbiguousForeignKeysError: Could not determine join condition between parent/child tables on relationship Group.group_roles - there are multiple foreign key path s linking the tables. Specify the 'foreign_keys' argument, providing a list of those columns which should be counted as containing a foreign key reference to the parent table.表下方添加以下内容，以代替GroupRole中已经定义的相应行：

Group

但是我遇到了同样的错误，而且看起来其他人也没有这样做。我究竟做错了什么？如何获得Group.group_roles = relationship('GroupRole', foreign_keys=[Column(String, ForeignKey(GroupRole.name))], back_populates='group')表来引用我的GroupRole表？我正在使用SQLAlchemy 1.3和python 3.7。

Answer 1

您可以使代码仅与backref关系上的GroupRole.group一起使用，例如：

class Group(Base):
    __tablename__ = 'groups'
    name = Column(String, primary_key=True)

class GroupRole(Base):
    __tablename__ = 'group_roles'
    name = Column(String, ForeignKey(Group.name))
    group_name = Column(String, ForeignKey(Group.name))
    role = Column(String, nullable=False)
    __table_args__ = (
        CheckConstraint('name != group_name'),
        PrimaryKeyConstraint('name', 'group_name'),
    )
    group = relationship(Group,
                         foreign_keys=[name],
                         backref='group_roles')

虽然不确定这是什么目的，但是可以工作：

g = Group(name='test', group_roles=[
    GroupRole(group_name='testrole', name='test', role='testrole'),
    GroupRole(group_name='testrole2', name='test', role='testrole2')
])
session.add(g)

SQLAlchemy：AmbiguousForeignKeysError对父对象的双重引用

1 个答案: