一对多关系中的多个外键 - SqlAlchemy

Question

我是 SQL Alchemy 的新手，我需要帮助来实现以下关系：

我有两个表Trends和ClosestTrends ，我想声明两个一对多关系：

表关系

在 SQL 中，它将是：

ALTER TABLE "closest_trends" ADD FOREIGN KEY ("id_trend_ref") REFERENCES "trends" ("id") ON DELETE CASCADE;

ALTER TABLE "closest_trends" ADD FOREIGN KEY ("id_trend_close") REFERENCES "trends" ("id") ON DELETE CASCADE;

我尝试了以下实现：

class Trends(Base):
    __tablename__ = "trends"
    __table_args__ = (
        UniqueConstraint(
            "name", "id_region", "language_iso", name="name_id_region_language"
        ),
    )
    id = Column(Integer, primary_key=True, index=True, unique=True)
    .
    .
    .
    closest_trends = relationship("ClosestTrends", backref="Trends")
   
    def __str__(self):
        return "Trends"



class ClosestTrends(Base):
    __tablename__ = "closest_trends"
    __table_args__ = (
        UniqueConstraint(
            "id_trend_ref", "id_trend_close", name="id_trend_ref_id_trend_close"
        ),
    )
    id = Column(Integer, primary_key=True, index=True, unique=True)
    .
    .
    .
    
    id_trend_ref = Column(
        Integer, ForeignKey("trends.id", ondelete="CASCADE"), nullable=False
    )
    id_trend_close = Column(
        Integer, ForeignKey("trends.id", ondelete="CASCADE"), nullable=False
    )
    
    def __str__(self):
        return "ClosestTrends"

我不工作，我收到以下错误：

sqlalchemy.exc.AmbiguousForeignKeysError：无法确定关系 Trends.closest_trends 上父/子表之间的连接条件 - 有多个外键路径链接表。 指定“foreign_keys”参数，提供应被视为包含对父表的外键引用的列的列表。

有谁知道如何解决这个问题？

非常感谢

Answer 1

您的解决方案写在官方网站上。
https://docs.sqlalchemy.org/en/13/orm/join_conditions.html#handling-multiple-join-paths
根据官方网站，我是这样实现的。

class Trends(Base):
    __tablename__ = "trends"
    __table_args__ = (
        UniqueConstraint(
            "name", "id_region", "language_iso", name="name_id_region_language"
        ),
    )
    id = Column(Integer, primary_key=True, index=True, unique=True)
    .
    .
    .
    # closest_trends = relationship("ClosestTrends", backref="Trends")
   
    def __str__(self):
        return "Trends"

class ClosestTrends(Base):
    __tablename__ = "closest_trends"
    __table_args__ = (
        UniqueConstraint(
            "id_trend_ref", "id_trend_close", name="id_trend_ref_id_trend_close"
        ),
    )
    id = Column(Integer, primary_key=True, index=True, unique=True)
    .
    .
    .
    
    id_trend_ref = Column(
        Integer, ForeignKey("trends.id", ondelete="CASCADE"), nullable=False
    )
    id_trend_close = Column(
        Integer, ForeignKey("trends.id", ondelete="CASCADE"), nullable=False
    )
    
    trend_ref = relationship("Trends", foreign_keys=[id_trend_ref])
    trend_close = relationship("Trends", foreign_keys=[id_trend_close])

    def __str__(self):