Hi all!
I try to automap my existing database to classes. Between two tables I have
multiple join paths and I have trouble managing those properly.
Here's a sample schema from my database:
CREATE SCHEMA shop;
CREATE TABLE shop.address (
id SERIAL PRIMARY KEY,
name text,
address text
)
CREATE TABLE shop.orders (
id SERIAL PRIMARY KEY,
items text,
billingaddr_id integer REFERENCES address,
shippingaddr_id integer REFERENCES address
);
I have declared relationships for those foreign keys as follows:
from sqlalchemy import create_enginefrom sqlalchemy.orm import
relationship, Sessionfrom sqlalchemy.ext.automap import automap_base
engine = create_engine(
"postgresql://postgres:postgres@localhost:5432/postgres",
future=True
)
Base = automap_base()
class Order(Base):
__tablename__ = 'orders'
__table_args__ = {"schema": "shop"}
billingaddr = relationship('address',
foreign_keys="Order.billingaddr_id", backref="orders_billed")
shippingaddr = relationship('address',
foreign_keys="Order.shippingaddr_id", backref="orders_shipped")
Base.prepare(engine, schema='shop', reflect=True)
Address = Base.classes.address
Now when creating a new Address object:
jack = Address(name='Jack', address='57815 Cheryl Unions')
I get a warning: "SAWarning: relationship 'Order.address' will copy column
address.id to column orders.shippingaddr_id, which conflicts with
relationship(s): 'address.orders_shipped' (copies address.id to
orders.shippingaddr_id), 'Order.shippingaddr' (copies address.id to
orders.shippingaddr_id). If this is not the intention, consider if these
relationships should be linked with back_populates, or if viewonly=True
should be applied to one or more if they are read-only. For the less common
case that foreign key constraints are partially overlapping, the
orm.foreign() annotation can be used to isolate the columns that should be
written towards. The 'overlaps' parameter may be used to remove this
warning."
How should this be solved?
That address relationship is the one automap creates automatically and
is now messing with me. I don't actually need that anymore since I
have created relationships by myself. Can I somehow prevent automap
from creating it by default or can I delete created unnecessary
relationships? I have tried to set address = None in the class
declaration but it didn't work. address relationship is still created.
Thanks,
Lauri
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