SQL Alchemy 关系与另一个表错误中同一个表的多个关系

Question

你好，我正在为博客文章创建一个 API，我想像那样创建表格

Post(id, title, subtitle, description, content, main_img, thumbnail_img, author, date) 这是它在 sqlalchemy 中的模型：

class Post(db.Model):
    __tablename__ = 'posts'
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100))
    subtitle = db.Column(db.String(100))
    description = db.Column(db.Text, nullable=True)
    content = db.Column(db.Text)
    main_image_id = db.Column(db.Integer, db.ForeignKey('image_details.id'))
    main_image = db.relationship('ImageDetails', back_populates='posts')
    thumbnail_image_id = db.Column(db.Integer, db.ForeignKey('image_details.id'))
    thumbnail_image = db.relationship('ImageDetails', back_populates='posts')
    author_id = db.Column(db.Integer, db.ForeignKey('authors.id'))
    author = db.relationship('Author', back_populates='posts')
    date = db.Column(db.DateTime, default=datetime.now())



    @classmethod
    def get_all(cls):
        return cls.query.all()

    @classmethod
    def get_by_id(cls, id):
        return cls.query.get(id)

    @classmethod
    def get_by_author_id(cls, author_id):
        return cls.query.filter_by(author_id=author_id).all()

    @classmethod
    def get_by_title(cls, title):
        return cls.query.filter_by(title=title).all()

    def add_to_db(self):
        db.session.add(self)
        db.session.commit()

    def delete_from_db(self):
        db.session.delete(self)
        db.session.commit()

我想将它与看起来像这样的 ImageDetails 表联系起来

ImageDetails(id, url_to_img_file, name, alt,) 这是模型的样子：

class ImageDetails(db.Model):
    __tablename__ = 'image_details'
    id = db.Column(db.Integer, primary_key=True)
    url = db.Column(db.String(255), nullable=False)
    name = db.Column(db.String(255), nullable=False)
    alt = db.Column(db.String(255), nullable=False)


    @classmethod
    def get_all(cls):
        return cls.query.all()

    @classmethod
    def get_by_id(cls, id):
        return cls.query.get_or_404(id)

    def add_to_db(self):
        db.session.add(self)
        db.session.commit()

    def delete_from_db(self):
        db.session.delete(self)
        db.session.commit()

但是我收到这个错误：

    sqlalchemy.exc.AmbiguousForeignKeysError: Could not determine join condition between parent/child tables on relationship Post.main_image - there are multiple foreign key paths 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.

我已经尝试过那样使用外键，但没有用

main_image = db.relationship('ImageDetails', back_populates='posts', foreign_keys=[main_image_id])

thumbnail_image = db.relationship('ImageDetails', back_populates='posts', foreign_keys=[thumbnail_image_id])

但是我得到了这个错误：

sqlalchemy.exc.InvalidRequestError: Mapper 'Mapper[ImageDetails(image_details)]' has no property 'posts'.  If this property was indicated from other mappers or configure events, ensure registry.configure() has been called.

也喜欢这个

main_image = db.relationship('ImageDetails', back_populates='posts', foreign_keys="[Post.main_image_id]")

thumbnail_image = db.relationship('ImageDetails', back_populates='posts', foreign_keys="[Post.thumbnail_image_id]")

我得到了这个错误：

sqlalchemy.exc.InvalidRequestError: Mapper 'Mapper[ImageDetails(image_details)]' has no property 'posts'.  If this property was indicated from other mappers or configure events, ensure registry.configure() has been called.

我试图让用户添加图片，然后当他添加帖子时，他可以从添加的图片中选择一张作为缩略图，一张作为主图。他添加图像时不需要设置关系，但在添加帖子时设置它。