sqlalchemy join two models, which relate to other 1 model - sql

Question

I'm working on FCM notification and I need to select all my push-tokens from user_notification_tokens table with filtering by other table datetime column, but there is no relation between these two tables, but they have relation with users table.
How can I do it with sqlalchemy?
simplified schema of sqlalchemy models relations:
I've tried to do it like this:
def get_tokens()
db: Session = next(db_service.get_session())
x_minutes_to_event = datetime.now(pytz.utc) + timedelta(minutes=config.MINUTES_TO_PRESCRIPTION)
tokens = [
item[0]
for item in db.query(models.UserNotificationsToken)\
.join(
models.User,
models.User.id == models.UserNotificationsToken.user_id,
)\
.join(
models.UserPrescription,
models.UserPrescription.user_id == models.User.id
)\
.filter(
models.UserPrescription.visiting_at <= x_minutes_to_event,
models.UserPrescription.visiting_at > datetime.now(pytz.utc),
)\
.values(column('token'))
]
# or
tokens = [
item[0]
for item in db.query(models.UserNotificationsToken)\
.join(
models.UserPrescription,
models.UserNotificationsToken.user_id == models.UserPrescription.user_id,
)\
.filter(
models.UserPrescription.visiting_at <= x_minutes_to_event,
models.UserPrescription.visiting_at > datetime.now(pytz.utc),
)\
.values(column('token'))
]
but I got this errors:
sqlalchemy.exc.InvalidRequestError: Don't know how to join to <Mapper at 0x7f0921681fd0; User>. Please use the .select_from() method to establish an explicit left side, as well as providing an explicit ON clause if not present already to help resolve the ambiguity.
# or
sqlalchemy.exc.InvalidRequestError: Don't know how to join to <Mapper at 0x7f54970e4970; UserPrescription>. Please use the .select_from() method to establish an explicit left side, as well as providing an explicit ON clause if not present already to help resolve the ambiguity.

Answer 1

class UserNotificationToken(Base):
__tablename__ = 'user_notification_tokens'
id = Column(Integer, primary_key=True)
user_id = Column(Integer, ForeignKey('users.id'), nullable=False)
token = Column(String)
user = relationship('User', back_populates='tokens')
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
tokens = relationship(UserNotificationToken, back_populates='user')
prescriptions = relationship('UserPrescription', back_populates='user')
class UserPrescription(Base):
__tablename__ = 'user_prescriptions'
id = Column(Integer, primary_key=True)
user_id = Column(Integer, ForeignKey('users.id'), nullable=False)
visiting_at = Column(DateTime)
user = relationship(User, back_populates='prescriptions')
metadata.create_all(engine)
class Config:
MINUTES_TO_PRESCRIPTION = 60
with Session(engine) as session, session.begin():
now = datetime.now(timezone.utc)
x_minutes_to_event = now + timedelta(minutes=60)
# Example 1 with explicit joins.
query = session.query(
UserNotificationToken.token
).join(
User, UserNotificationToken.user_id == User.id
).join(
UserPrescription, User.id == UserPrescription.user_id
).where(
and_(
UserPrescription.visiting_at <= x_minutes_to_event,
UserPrescription.visiting_at > now))
for (token,) in query.all():
print (token)
# Example 2 with joins inferred from relationships.
query = session.query(
UserNotificationToken.token
).join(
UserNotificationToken.user
).join(
User.prescriptions
).where(
and_(
UserPrescription.visiting_at <= x_minutes_to_event,
UserPrescription.visiting_at > now))
for (token,) in query.all():
print (token)
# Example 3 join directly between tables with user_id FKs, use distinct
query = session.query(
UserNotificationToken.token
).join(
UserPrescription, UserNotificationToken.user_id == UserPrescription.user_id
).where(
and_(
UserPrescription.visiting_at <= x_minutes_to_event,
UserPrescription.visiting_at > now)).distinct()
for (token,) in query.all():
print (token)