from sqlalchemy import *
db = create_engine("sqlite:///:memory:")
metadata = BoundMetaData(db)
session = create_session()
class Employee(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return self.__class__.__name__ + " " + self.name
class Manager(Employee):
def __init__(self, name, manager_data):
self.name = name
self.manager_data = manager_data
def __repr__(self):
return self.__class__.__name__ + " " + self.name + " " + self.manager_data
class Engineer(Employee):
def __init__(self, name, engineer_info):
self.name = name
self.engineer_info = engineer_info
def __repr__(self):
return self.__class__.__name__ + " " + self.name + " " + self.engineer_info
employees_table = Table('employees', metadata,
Column('employee_id', Integer, primary_key=True),
Column('name', String(50)),
Column('manager_data', String(50)),
Column('engineer_info', String(50)),
Column('type', String(20))
)
employee_mapper = mapper(Employee, employees_table, polymorphic_on=employees_table.c.type)
manager_mapper = mapper(Manager, inherits=employee_mapper, polymorphic_identity='manager')
engineer_mapper = mapper(Engineer, inherits=employee_mapper, polymorphic_identity='engineer')
employees_table.create()
session.save(Manager('Tom', 'knows how to manage things'))
session.save(Engineer('Kurt', 'knows how to hack'))
session.flush()
# this gives you [Engineer Kurt knows how to hack, Manager Tom knows how to manage things]
# as it should be
session.query(Employee).select()
# this gives you [Engineer Kurt knows how to hack, Manager Tom knows how to manage things]
# instead of [Engineer Kurt knows how to hack]
session.query(Engineer).select()
# this gives you [Engineer Kurt knows how to hack, Manager Tom knows how to manage things]
# instead of [Manager Tom knows how to manage things]
session.query(Manager).select()
