python - 如何替换 SQLAlchemy 映射器已弃用的 "order_by"选项？

Question

我有一个 Single Table Inheritance看起来像这样的 sqlalchemy orm 模型:

class Human(Base):
    
    __tablename__ = "human"

    id = Column(Integer, primary_key=True)
    name = Column(String)
    index = Column(Integer)
    parent_id = Column(Integer, ForeignKey("human.id"), nullable=True)
    type = Column(String)
    parent = relationship(
        "Human",
        cascade="save-update, merge",
        backref=backref("children", cascade="all"),
        lazy=False,
        remote_side="Human.id",
    )

    __mapper_args__ = {"polymorphic_on": type, "polymorphic_identity": "human"}

class Parent(Human):

    __mapper_args__ = {"polymorphic_identity": "parent"}

class Child(Human):

    hobby = Column(String)
    pet = Column(String)

    __mapper_args__ = {"polymorphic_identity": "child"}

这种关系看起来像一个嵌套的树，我可以在其中查询最年长的人(即:曾祖 parent ，使用 query.get(1))，然后查询他的 children归他所有children将出席，每个 child 也将有他们的children展示。
这种关系在各个方面都运行良好。
我想要 children当我查询 Parent 时所查询的(由于lazy=False)由index 订购列不是id列(这是默认值)。
我通过添加以下内容来实现这一点 "order_by": "index"到 Human类(class)'__mapper_args__如下:

__mapper_args__ = {"polymorphic_on": type, "polymorphic_identity": "human", "order_by": "index"}

我最近发现在 SQLAlchemy 中 order_by mapper() 中的参数自 SQLAlchemy 版本 1.1 起不推荐使用类( reference )。他们说要使用 Query.order_by()改为订购该套装，但由于某种原因这对我不起作用。
我尝试了以下方法:

添加 order_by到查询，session.query(Human).order_by(Human.index).get(1)

添加 order_by="Human.index"到 relationship()在 Human类(class)。

这两种方法都行不通。
我怎样才能达到和order_by一样的效果在 mapper()现在它正在被弃用？

Answer 1

我在 sqlalchemy's github 上提问后得到了答案.
我正在提出响应，以防其他人搜索此问题并在此处而不是 sqlalchemy 的 github 中找到它。
The answer:

the ordering of a collection loaded by a relationship is controlled by the order_by parameter of relationship() and/or backref. In this case you want "children" to be ordered so you put that where you define "children":

parent = relationship(
       "Human",
       cascade="save-update, merge",
       backref=backref("children", cascade="all", order_by="Human.index"),
       lazy=False,
       remote_side="Human.id",
   )

that is, this has nothing to do with mapper.order_by, although that attribute was having the effect you were seeking. if you had tried relationship->order_by on the "parent' side, that was the wrong side, it goes where the actual thing to be ordered is defined, in this case the backref.