python - SQLAlchemy - bool 混合属性

Question

我希望能够运行以下 SQLAlchemy 查询:

q_done = Batch.query.filter(Batch.done)
q_running = Batch.query.filter(~Batch.done)

但我无法专心写 expression对应我的 done混合属性。

SQLAlchemy 模型:

class Action(db.Model):
    id          = db.Column(db.Integer, primary_key=True)
    action      = db.Column(db.String(32))
    done        = db.Column(db.Boolean, default=False)
    batch       = db.relationship(Batch.__name__, backref='actions')

class Batch(db.Model):
    id                = db.Column(db.Integer, primary_key=True)
    name              = db.Column(db.String(255), default='unknown')

    @hybrid_property
    def total_actions(self):
        return db.session.query(Action).join(Action.batch).filter(Batch.id == self.id).count()

    @hybrid_property
    def finished_actions(self):
        return db.session.query(Action).join(Action.batch).filter(Batch.id == self.id).filter(Action.done).count()

    @hybrid_property
    def done(self):
        return self.total_actions == self.finished_actions

我尝试实现了相应的 expression没有太大的成功。很难理解如何返回 bool 查询。这是我卑微的尝试:

@done.expression
def done(self):
    total_actions = db.session.query(func.sum(Batch.actions))
    finished_actions = db.session.query(func.sum(Batch.actions.done))
    return db.session.query(Batch).filter(total_actions == finished_actions)

Answer 1

问题是 total_actions和 finished_actions都是hybrid attributes因此不能在 expression 中使用对于 done .

我必须添加相应的expression对于每个返回查询而不是值的人。

这是完整的代码:

class Action(db.Model):
    id          = db.Column(db.Integer, primary_key=True)
    action      = db.Column(db.String(32))
    done        = db.Column(db.Boolean, default=False)
    batch       = db.relationship(Batch.__name__, backref='actions')

class Batch(db.Model):
    id = db.Column(db.Integer, primary_key=True)

    @hybrid_property
    def total_actions(self):
        return db.session.query(Action).join(Action.batch).filter(Batch.id == self.id).count()

    @total_actions.expression
    def total_actions(cls):
       return (select([func.count(Action.id)]).
                where(Action.bid == cls.id).
                label("total_actions"))

    @hybrid_property
    def finished_actions(self):
        return db.session.query(Action).join(Action.batch).filter(Batch.id == self.id).filter(Action.done).count()

    @finished_actions.expression
    def finished_actions(cls):
       return (select([func.count(Action.id)]).
                where(Action.bid == cls.id).
                where(Action.done).
                label("finished_actions"))

    @hybrid_property
    def done(self):
       return self.total_actions == self.finished_actions

    @done.expression
    def done(cls):
       return cls.total_actions == cls.finished_actions