如何将具有计数结果的列添加到 sqlalchemy 查询并通过 pydantic 检查？

Question

说明

以前，我的查询返回单个 Stories 表的内容。现在我想添加更多信息：我需要为每个故事输出 prizes_count。 Stories 表中没有字段 prizes_count，所以我进行了以下查询。

db.query(models.Stories, func.count(models.Stories.prizes).label("prizes_count")).join(models.Prizes)\
        .group_by(models.Stories.id).all()

但我有两个问题。

1. 我从 Pydantic 得到验证错误，因为这个查询返回一个像 (<database.models.Stories object at 0x0000026BB0055E20>, 1) 这样的元组列表。我必须将 prizes_count 值插入 Stories 对象，反之亦然，将所有字段拉入元组。当然，我可以手动完成，但我认为有更好的方法。
2. 使用此查询，我失去了所有 0 个奖品的故事，因为我的加入忽略了它们。

代码

端点

@app.get("/stories/", response_model=List[schemas.StoryFullInfo])
def get_stories(db: Session = Depends(get_db)):
    return crud.get_stories(db)

粗制滥造

def get_stories(db: Session):
    return db.query(models.Stories, func.count(models.Stories.prizes).label("prizes_count")).join(models.Prizes)\
        .group_by(models.Stories.id).all()

模型

class Stories(Base):
    __tablename__ = "stories"
    id = Column(INTEGER(unsigned=True), primary_key=True)
    title = Column(String(length=128), index=True)
    text = Column(String(length=1000))
    author_id = Column(INTEGER(unsigned=True), ForeignKey("users.id", onupdate="CASCADE", ondelete="CASCADE"),
                       nullable=False)
    status = Column(TINYINT(unsigned=True), server_default="0")
    genre_type = Column(TINYINT(unsigned=True), server_default="0")
    likes_count = Column(INTEGER(unsigned=True), server_default="0")
    image = Column(Text)
    added_to_best_by = Column(INTEGER(unsigned=True))
    creation_DT = Column(DateTime, server_default=func.now())
    change_status_DT = Column(DateTime)

    author = relationship("Users", back_populates="stories")
    comments = relationship("Comments", back_populates="story")
    prizes = relationship("Prizes", back_populates="story")


class Prizes(Base):
    __tablename__ = "prizes"
    id = Column(INTEGER(unsigned=True), primary_key=True)
    title = Column(String(length=128), nullable=False)
    image_id = Column(TINYINT(unsigned=True))
    story_id = Column(INTEGER(unsigned=True), ForeignKey("stories.id", onupdate="CASCADE", ondelete="CASCADE"),
                      nullable=False)
    user_id = Column(INTEGER(unsigned=True), ForeignKey("users.id", onupdate="CASCADE", ondelete="CASCADE"),
                     nullable=False)
    text = Column(String(length=512), nullable=False)
    creation_DT = Column(DateTime, server_default=func.now())

    story = relationship("Stories", back_populates="prizes")
    author = relationship("Users", back_populates="prizes")

模式

class StoryBaseInfo(BaseModel):
    id: int
    title: str = None
    author_id: int

    class Config:
        orm_mode = True


class StoryUpdateInfo(StoryBaseInfo):
    #title: str = None
    text: str = None
    status: int
    genre_type: int
    likes_count: int
    image: str = None
    added_to_best_by: int = None
    change_status_DT: datetime = None

    class Config:
        orm_mode = True


class StoryFullInfo(StoryUpdateInfo):

    creation_DT: datetime
    author: UserBaseInfo
    prizes_count: int

    class Config:
        orm_mode = True


class PrizeBaseInfo(BaseModel):
    id: int
    story_id: int

    class Config:
        orm_mode = True


class PrizeInfo(PrizeBaseInfo):
    title: str
    image_id: int
    text: str
    creation_DT: datetime

    author: UserBaseInfo
    story: StoryBaseInfo

    class Config:
        orm_mode = True

Answer 1

好吧，事实证明，当我问这个问题时，我的想法是错误的。 SQLAlchemy 的特性解决了这个问题。我可以使用我配置的关系来计算奖品。 我的解决方案是将混合属性添加到 Stories SQLAlchemy 模型中

class Stories(Base):
    __tablename__ = "stories"
    id = Column(INTEGER(unsigned=True), primary_key=True)
    title = Column(String(length=128), index=True)
    text = Column(String(length=1000))
    author_id = Column(INTEGER(unsigned=True), ForeignKey("users.id", onupdate="CASCADE", ondelete="CASCADE"),
                       nullable=False)
    status = Column(TINYINT(unsigned=True), server_default="0")
    genre_type = Column(TINYINT(unsigned=True), server_default="0")
    likes_count = Column(INTEGER(unsigned=True), server_default="0")
    image = Column(Text)
    added_to_best_by = Column(INTEGER(unsigned=True))
    creation_DT = Column(DateTime, server_default=func.now())
    change_status_DT = Column(DateTime)

    author = relationship("Users", back_populates="stories")
    comments = relationship("Comments", back_populates="story")
    prizes = relationship("Prizes", back_populates="story")

    @hybrid_property
    def prizes_count(self):
        return len(self.prizes)

然后下面的查询将满足 Pydantic 方案。

def get_stories(db: Session):
    return db.query(models.Stories).all()