Flask-appbuilder 多对可能关系 sqlalchemy.exc.NoReferencedTableError 错误

Question

我已经阅读了所有这些 (https://stackoverflow.com/search?q=sqlalchemy.exc.NoReferencedTableError%3A)、Flask-appbuilder 文档、sqlalchemy 文档和 Flask-sqlalchemy 文档等等。不幸的是，我找不到任何多对多 sqlalchemy 关系的完整示例。

我有一个使用 flask-appbuilder 的 python Flask 应用程序（它依赖于 flask-sqlalchemy）。我的 app/model.py 文件有这个：

field_feature_association = Table('field_feature_association',Base.metadata,
                                            Column('field_id', Integer, ForeignKey('field.id')),
                                            Column('feature_id',Integer, ForeignKey('feature.id')),
                                            schema="main"
                                        )

class field(Model):
    __tablename__ = 'field'
    id = Column(Integer, primary_key=True)
    name = Column(String(70), nullable=False)
    database_type = Column(String(70)) #varchar(255), text, int
    joinable_to = Column(Text()) 
    notes = Column(Text()) #don't use this for X 
    table_id = Column(Integer, ForeignKey('table.id'))
    table = relationship("table")
    features = relationship("feature",
                    secondary = field_feature_association,
                    backref = backref('fields'), 
                    )

    def __repr__(self):
        return self.name

class feature(Model):
    __tablename__ = 'feature'
    id = Column(Integer, primary_key=True)
    name = Column(String(70), unique = True, nullable=False)
    field_id = Column(Integer, ForeignKey('field.id'))
    #field = relationship("field")

    def __repr__(self):
        return self.name

它正在生成此错误：

sqlalchemy.exc.NoReferencedTableError: Foreign key associated with column 'field_feature_association.feature_id' could not find table 'feature' with which to generate a foreign key to target column 'id'

关于如何修复此错误的想法？

Answer 1

这里是 SQLAlchemy 中的a working sample of many-to-many。此外，我修改了您的模型并且效果很好：

field_feature_association = db.Table('field_feature_association', db.Model.metadata,
                                     db.Column('field_id', db.Integer, db.ForeignKey('field.id')),
                                     db.Column('feature_id', db.Integer, db.ForeignKey('feature.id')),
                                          schema="main"
        )


class Field(db.Model):
    __tablename__ = 'field'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(70), nullable=False)
    database_type = db.Column(db.String(70))  # varchar(255), text, int
    joinable_to = db.Column(db.Text())
    notes = db.Column(db.Text())  # don't use this for X
    features = db.relationship("Feature",
                            secondary=field_feature_association,
                            backref=db.backref('fields'),
    )

    def __repr__(self):
        return self.name


class Feature(db.Model):
    __tablename__ = 'feature'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(70), unique=True, nullable=False)
    field_id = db.Column(db.Integer, db.ForeignKey('field.id'))
    # field = relationship("field")

    def __repr__(self):
        return self.name

这是如何使用它：

field = Field()
field.name="filed1"
feature = Feature()
feature.name = "feature1"
field.features.append(feature)
db.session.add(field)
db.session.commit()

我的数据库对象被导入为“db”，我明确地使用它来引用其他类型。