I have entity Client, it has one-to-many relation to entity Address. Address has column type, witch can be primary (int 1) or secondary (int 2).
I can access client addresses through client.addresses == [...] Now can I create accessors witch would act as one-to-one, eg: client.primary_address == Address(...) witch would evaluate to JOIN with extra JOIN arg: ON (client.id == address.client_id and address.type = 1)?
Following Specifying Alternate Join Conditions documentation, you can do:
class Client(Base):
__tablename__ = "client"
client_id = Column(Integer, primary_key=True)
# ...
addresses = relationship(Address, ...)
primary_address = relationship(Address, uselist=False,
primaryjoin = and_(Address.client_id == client_id, Address.type == 1),
)
secondary_address = relationship(Address, uselist=False,
primaryjoin = and_(Address.client_id == client_id, Address.type == 2),
)
This will allow you to access (read) both primary and secondary addresses as if it were 1-1 relationship. You can event set (write) it like below:
my_client.primary_address = Address(type=1, ...)
but you will have to ensure that the Address has proper value (1 or 2) for the type column which seems to be a technical field.
Side remark: type is reserved word in python.
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