python - backref lazy='dynamic' - does not support object population - eager loading cannot be applied -

how can planes bookings between 2 dates specified. need bookings filtered down included if they're between 2 dates. tried error: 'plane.bookings' not support object population - eager loading cannot applied.

why error occur , how can fixed?

planes = (db.session.query(plane)              .join(booking)              .filter(booking.start_date >= date)              .options(contains_eager(plane.bookings))) 

the models:

class booking(db.model):         id = db.column(db.integer, primary_key=true)         start_date = db.column(db.datetime)         end_date = db.column(db.datetime)          person_id = db.column(db.integer, db.foreignkey('person.id'))         person = db.relationship('person', foreign_keys=[person_id], backref=db.backref('bookings', lazy='dynamic'))          instructor_id = db.column(db.integer, db.foreignkey('person.id'))         instructor = db.relationship('person', foreign_keys=[instructor_id], backref=db.backref('instructor_bookings', lazy='dynamic'))          plane_id = db.column(db.integer, db.foreignkey('plane.id'))         plane = db.relationship('plane', backref=db.backref('bookings', lazy='dynamic'))          def __init__(self, start_date, end_date, plane_id, instructor_id, person_id):             self.start_date = start_date             self.end_date = end_date             self.plane_id = plane_id             self.instructor_id = instructor_id             self.person_id = person_id          def __repr__(self):             return '<booking... %r>'          def as_dict(self):            return {c.name: getattr(self, c.name) c in self.__table__.columns}       class plane(db.model):         id = db.column(db.integer, primary_key=true)         name = db.column(db.string(80))         description = db.column(db.string(120))          def __init__(self, name, description):             self.name = name             self.description = description          def __repr__(self):             return '<plane... %r>'          def as_dict(self):            return {c.name: getattr(self, c.name) c in self.__table__.columns} 

the error message tells "wrong": lazy='dynamic' relationship can't eager loaded. dynamic relationships produce new queries, not collections (lists). doesn't make sense pre-load dynamic relationship because entire point of dynamic relationship able construct other queries.

use dynamic relationship filter bookings when accessing them. isn't optimal requires query per plane bookings.

planes = plane.query.join(plane.bookings).filter(booking.start_date >= date) plane in planes:     bookings = plane.bookings.filter(booking.start_date >= date) 

more likely, wanted non-dynamic relationship. remove lazy='dynamic' relationship's backref. if pass contains_eager join has been filtered, resulting collection have filtered items.

plane = db.relationship(lambda: plane, backref='bookings') # ... planes = plane.query.join(plane.bookings ).filter(booking.start_date >= date ).options(db.contains_eager(plane.bookings)) 

also note there nothing stopping defining 2 relationships same collection, 1 dynamic , 1 not, using whichever needed doing @ time.