table name specified more than once

Question

I have the following tables configured:

class User(Base): __tablename__ = "user" id = Column(Integer, primary_key=True) name = Column(String) class Gadget(Base): __tablename__ = "gadget" id = Column(Integer, primary_key=True) brand = Column(String) class UserGadget(Base): __tablename__ = "user_gadget" user_id = Column(Integer, ForeignKey('user.id'), primary_key=True) gadget_id = Column(Integer, ForeignKey('gadget.id'), primary_key=True) user = relationship("User", backref=backref('userGadgets', order_by=user_id)) gadget = relationship("Gadget", backref=backref('userGadgets', order_by=gadget_id)) class GadgetComponent(Base): __tablename__ = "gadget_component" id = Column(String, primary_key=True) gadget_id = Column(Integer,ForeignKey('gadget.id')) component_maker = Column(String) host = relationship("Gadget", backref=backref('components', order_by=id)) class ComponentUsingMetal(Base): __tablename__ = "component_metal" id = Column(Integer, primary_key=True) component_id = Column(Integer, ForeignKey('GadgetComponent.id')) metal = Column(String) component = relationship("GadgetComponent", backref=backref('gadgetComponentMetals', order_by=id))

On doing the following query: session.query(User).join("userGadgets", "gadget", "components","gadgetComponentMetals").filter(ComponentUsingMetal.metal == 'iron') , component_metal gets attached to the query twice giving an error 'table name component_metal specified more than once'.
Any idea what I am doing wrong?

Ranjan · Accepted Answer · 2014-02-21 10:48:14Z

I traced the problem down to the following line in selectable.py: froms = [f for f in froms if f not in toremove] This line removes the tables which are already covered by joins so that FROM clause doesn't have the same table specified more than once. The line didn't remove component_metal even though toremove had it meaning that I had two different Table objects for the same db table. And then I noticed the import for component_metal's class, ComponentUsingMetal, looked different. The others imports looked like:

from myschema import GadgetComponent from myschema import Gadget from python.myschema ComponentUsingMetal

As soon as fixed the import the issue went away.

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