I'm trying to create a relation that has a between join. Here is a shortish example of what I'm trying to do:

#!/usr/bin/env python
import sqlalchemy as sa
from sqlalchemy import orm
from sqlalchemy.engine.base import Engine
from sqlalchemy.ext.declarative import declarative_base


metadata = sa.MetaData()
Base = declarative_base(metadata=metadata)

engine = sa.create_engine('sqlite:///:memory:')

class Network(Base):
    __tablename__ =  "network"
    id = sa.Column(sa.Integer, primary_key=True)
    ip_net_addr_db = sa.Column('ip_net_addr', sa.Integer, index=True)
    ip_broadcast_addr_db = sa.Column('ip_broadcast_addr', sa.Integer, index=True)
    # This can be determined from the net address and the net mask, but we store
    # it in the db so that we can join with the address table.
    ip_net_mask_len = sa.Column(sa.SmallInteger)

class Address(Base):
    __tablename__ =  "address"
    ip_addr_db = sa.Column('ip_addr', sa.Integer, primary_key=True,
              index=True, unique=True)

Network.addresses = orm.relation(Address, 
    primaryjoin=Address.ip_addr_db.between(
                Network.ip_net_addr_db,
                Network.ip_broadcast_addr_db),
    foreign_keys=[Address.ip_addr_db])    

metadata.create_all(engine) 

Session = orm.sessionmaker(bind=engine)

Network()

I you run this, you get this error:

ArgumentError: Could not determine relation direction for primaryjoin condition 
'address.ip_addr BETWEEN network.ip_net_addr AND network.ip_broadcast_addr', on relation Network.addresses. 
Do the columns in 'foreign_keys' represent only the 'foreign' columns in this join condition ?

The answer to that question is Yes, but I cant figure out how to tell it that