Complex joins with Peewee - mysql

Question

It's rather embarrassing to ask this question, since it seems to be so trivial, yet I can't find a solution that works.
I have the following function:
def planner(departure_id, arrival_id):
departure = Stop.get(Stop.id == departure_id)
arrival = Stop.get(Stop.id == arrival_id)
buses = Bus.select().join(RideStopRelationship).join(Stop).where(Stop.id == departure)
for bus in buses:
print bus.line
for stop in bus.stops:
print stop.time, stop.stop.name
based on the following models:
class Stop(BaseModel):
name = CharField()
#lat = FloatField()
#lng = FloatField()
class Bus(BaseModel):
line = IntegerField()
number = IntegerField()
direction = IntegerField()
class RideStopRelationship(BaseModel):
bus = ForeignKeyField(Bus, related_name = "stops")
stop = ForeignKeyField(Stop, related_name = "buses")
time = TimeField()
The crucial line is Bus.select().join(RideStopRelationship).join(Stop).where(Stop.id == departure). I'm trying to get all buses that will stop at both departure and arrival. However, the above query returns all buses that stop at departure. How would I get buses that stop at both 'departure' and 'arrival'?
If I'm making this too complicated (either my models being too complicated, or my query), feel free to correct me.
EDIT:
There's one way that does work:
buses_departure = Bus.select().join(RideStopRelationship).join(Stop).where(Stop.id == departure)
buses_arrival = Bus.select().join(RideStopRelationship).join(Stop).where(Stop.id == arrival)
buses = Bus.select().where(Bus.id << buses_departure & Bus.id << buses_arrival)
but it's rather long for what should be a simply query...

Answer 1

You might try something like this:
departure = Stop.get(...)
arrival = Stop.get(...)
query = (Bus
.select(Bus)
.join(RideStopRelationship)
.where(RideStopRelationship.stop << [departure, arrival])
.group_by(Bus)
.having(fn.Count(Bus.id) == 2))
Unrelated, but one thing to note is that due to the way python evaluates operators, you need to put parentheses around your in queries:
buses = Bus.select().where(
(Bus.id << buses_departure) &
*Bus.id << buses_arrival))