Flask SQLAlchemy filter records from foreign key relationship

Question

I have 2 models:

class Scenario(db.Model):
    __tablename__ = 'scenarios'
    scenario_id = db.Column(db.Integer, primary_key=True)
    scenario_name = db.Column(db.String(120))
    scenario_text = db.Column(db.Text)
    hints = db.relationship('Hint', backref='scenario', lazy='dynamic')

    def __init__(self, scenario_name, scenario_text):
        self.scenario_name = scenario_name
        self.scenario_text = scenario_text

    def __repr__(self):
        return "<Scenario(scenario_name='%s', scenario_text='%s', hints='%s')>" % self.scenario_name, self.scenario_text, self.hints

class Hint(db.Model):
    __tablename__ = 'hints'
    hint_id = db.Column(db.Integer, primary_key=True)
    scenario_id = db.Column(db.Integer, db.ForeignKey('scenarios.scenario_id'))
    hint = db.Column(db.Text)
    release_time = db.Column(db.Integer)    

    def __init__(self, scenario_id, hint, release_time):
        self.scenario_id = scenario_id
        self.hint = hint
        self.release_time = release_time

    def __repr__(self):
        return "<Hint(scenario_id='%s', hint='%s', release_time='%s')>" % self.scenario_id, self.hint, self.release_time

I want to be able to get all the scenarios with their corresponding hints but only the hints that have a release_time less than the current time.

I figured this would work:

scenarios = Scenario.query.filter(Scenario.hints.release_time < time.time())

But I get this error:

AttributeError: Neither 'InstrumentedAttribute' object nor 'Comparator' object associated with Scenario.hints has an attribute 'release_time'

I just started playing around with Flask and SQLAlchemy. Any advice would be appreciated.

Answer 1

Scenario.hints is a query, so you'll need to use a join to perform this kind of filtering.

>>> scenarios = Scenario.query.join(Hint).filter(Hint.release_time < time.time())
>>> scenarios.first()
>>> <Scenario(scenario_name='hi', scenario_text='world', hints='SELECT hints.hint_id AS hints_hint_id, hints.scenario_id AS hints_scenario_id, hints.hint AS hints_hint, hints.release_time AS hints_release_time FROM hints WHERE :param_1 = hints.scenario_id')>

See the query docs and the ORM tutorial for more details.