hi,
i'm new to sqlalchemy, so far it seems really nice, by far the best
opensource orm in python, i ran into a problem though trying to model
a user system, with users and groups subclassed from principals, and a
many to many relation between users and groups. i have the following
code, attached but it tosses an error when trying to define the
relation, not sure what to make of it. if i remove the inheritance
everything works fine. should i file an issue in trac?
> python model.py
Traceback (most recent call last):
File "model.py", line 73, in ?
properties=dict( users = relation(User.mapper, user_group_map,
lazy=True, backref='groups' ) )
File
"/home/hazmat/Desktop/sqlalchemy/lib/sqlalchemy/mapping/__init__.py",
line 114, in assign_mapper
m = mapper(class_, *args, **params)
File
"/home/hazmat/Desktop/sqlalchemy/lib/sqlalchemy/mapping/__init__.py",
line 49, in mapper
return Mapper(class_, table, *args, **params)
File
"/home/hazmat/Desktop/sqlalchemy/lib/sqlalchemy/mapping/mapper.py", line
175, in __init__
prop.init(key, self)
File
"/home/hazmat/Desktop/sqlalchemy/lib/sqlalchemy/mapping/mapper.py", line
770, in init
self.do_init(key, parent)
File
"/home/hazmat/Desktop/sqlalchemy/lib/sqlalchemy/mapping/properties.py",
line 168, in do_init
self.secondaryjoin = sql.join(self.target, self.secondary).onclause
File "/home/hazmat/Desktop/sqlalchemy/lib/sqlalchemy/sql.py", line
41, in join
return Join(left, right, onclause, **kwargs)
File "/home/hazmat/Desktop/sqlalchemy/lib/sqlalchemy/sql.py", line
834, in __init__
self.onclause = self._match_primaries(left, right)
File "/home/hazmat/Desktop/sqlalchemy/lib/sqlalchemy/sql.py", line
856, in _match_primaries
if fk.references(secondary):
File "/home/hazmat/Desktop/sqlalchemy/lib/sqlalchemy/schema.py", line
53, in __getattr__
return getattr(self._impl, key)
AttributeError: 'ColumnImpl' object has no attribute 'references'
cheers,
kapil
"""
principal base class -
- user derives
- group derives
many2many user group mapping
dies when defining relation
"""
import sqlalchemy
from sqlalchemy import *
engine = sqlalchemy.engine.create_engine(
'postgres',
{'database':'example', 'user':'hazmat' },
echo=True
)
principals = Table(
'principals',
engine,
Column('principal_id', Integer, Sequence('principal_id_seq', optional=False), primary_key=True),
Column('name', String(50), nullable=False),
)
users = Table(
'users',
engine,
Column('principal_id', Integer, ForeignKey('principals.principal_id'), primary_key=True),
Column('password', String(50), nullable=False),
Column('email', String(50), nullable=False),
Column('login_id', String(50), nullable=False),
)
groups = Table(
'groups',
engine,
Column( 'principal_id', Integer, ForeignKey('principals.principal_id'), primary_key=True),
)
user_group_map = Table(
'user_group_map',
engine,
Column('user_id', Integer, ForeignKey( "users.principal_id"), primary_key=True ),
Column('group_id', Integer, ForeignKey( "groups.principal_id"), primary_key=True )
)
class Principal( object ):
pass
class User( Principal ):
pass
class Group( Principal ):
pass
assign_mapper( Principal, principals )
assign_mapper(
User,
users,
inherits=Principal.mapper
)
assign_mapper(
Group,
groups,
inherits=Principal.mapper,
properties=dict( users = relation(User.mapper, user_group_map, lazy=True, backref='groups' ) )
)
