Hello,
i just got started with SA and tried to follow the polymorphic loading
example from:
http://www.sqlalchemy.org/docs/adv_datamapping.myt#advdatamapping_inheritance_multiple
(the example needed some modifications: %s/Person/Employee/g)
However polymorphic loading seems broken with SA 0.2.5.
An interactive session with the attached file results in:
>>> from polymorphic import *
>>> create_some_employees()
>>> session.query(Engineer).select()
[Engineer Kurt knows how to hack]
>>> session.query(Employee).select()
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "build/bdist.linux-i686/egg/sqlalchemy/orm/session.py", line 179,
in query
File "build/bdist.linux-i686/egg/sqlalchemy/orm/query.py", line 28, in
__init__
AttributeError: 'Mapper' object has no attribute 'pks_by_table'
Did i miss something or is this a newly introduced bug?
Cheers, Sol.
from sqlalchemy import *
db = create_engine('postgres:///satest')
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
people = Table('people', metadata,
Column('person_id', Integer, primary_key=True),
Column('name', String(50)),
Column('type', String(30)))
engineers = Table('engineers', metadata,
Column('person_id', Integer, ForeignKey('people.person_id'), primary_key=True),
Column('engineer_info', String(50)),
)
managers = Table('managers', metadata,
Column('person_id', Integer, ForeignKey('people.person_id'), primary_key=True),
Column('manager_data', String(50)),
)
person_join = polymorphic_union( {
'engineer':people.join(engineers),
'manager':people.join(managers),
'person':people.select(people.c.type=='person'),
}, None, 'pjoin')
person_mapper = mapper(Employee, people, select_table=person_join, polymorphic_on=person_join.c.type, polymorphic_identity='person')
mapper(Engineer, engineers, inherits=person_mapper, polymorphic_identity='engineer')
mapper(Manager, managers, inherits=person_mapper, polymorphic_identity='manager')
def create_some_employees():
people.create()
engineers.create()
managers.create()
session.save(Manager('Tom', 'knows how to manage things'))
session.save(Engineer('Kurt', 'knows how to hack'))
session.flush()
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