Michael Bayer wrote:
> for this program, move the "managers" property after the compilation of
> the other mappers:
>
> person_mapper.compile()
> person_mapper.add_property('managers', relation(Manager,
> secondary=people_managers, lazy=False))
>
> this is a workaround for this particular issue.
For sqlite it works now. But if i choose to use a postgresql database i
will only be able to select employees, others will fail.
e. g.
>>> from polymorphic import *
>>> session.query(Manager).select()
...
...
SQLError: (ProgrammingError) relation "anon_d9b1" does not exist
Thanks for your help so far:)
Cheers, Sol.
from sqlalchemy import *
db = create_engine('sqlite:///sqlite_base')
#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)),
)
people_managers = Table('people_managers', metadata,
Column('person_id', Integer, ForeignKey("people.person_id")),
Column('manager_id', Integer, ForeignKey("managers.person_id"))
)
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',
#properties = dict(managers = relation(Manager, secondary=people_managers, lazy=False))
)
engineer_mapper = mapper(Engineer, engineers, inherits=person_mapper, polymorphic_identity='engineer')
manager_mapper = mapper(Manager, managers, inherits=person_mapper, polymorphic_identity='manager')
person_mapper.compile()
person_mapper.add_property('managers', relation(Manager, secondary=people_managers, lazy=False))
def create_some_employees():
people.create()
engineers.create()
managers.create()
people_managers.create()
session.save(Manager('Tom', 'knows how to manage things'))
session.save(Engineer('Kurt', 'knows how to hack'))
session.flush()
create_some_employees()
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