[Sqlalchemy-tickets] Issue #3004: don't generate relationships for joined subclass to superclass / automap (zzzeek/sqlalchemy)

[Mike B. <iss...@bi...>]

New issue 3004: don't generate relationships for joined subclass to superclass / automap
https://bitbucket.org/zzzeek/sqlalchemy/issue/3004/dont-generate-relationships-for-joined

Mike Bayer:


```
#!python

from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.automap import automap_base

Base = automap_base(declarative_base=declarative_base())

class Employee(Base):
    __tablename__ = 'employee'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))
    type = Column(String(50))
    __mapper_args__ = {
        'polymorphic_identity':'employee', 'polymorphic_on':type
    }

class Engineer(Employee):
    __tablename__ = 'engineer'
    id = Column(Integer, ForeignKey('employee.id'), primary_key=True)
    engineer_name = Column(String(30))
    __mapper_args__ = {
        'polymorphic_identity':'engineer',
    }


engine = create_engine("sqlite://")
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)

Base.prepare(engine, reflect=True)
assert not Engineer.__mapper__.relationships


```