La clave para simplificar su modelo es usar associationproxy, por lo tanto, definitivamente debe verificarlo.
Suponiendo que el usuario sólo puede tener un papel dentro de un grupo, el código de abajo debe responder a todas sus preguntas:
- cómo configurar el modelo y las relaciones
- cómo añadir/eliminar/actualizar los papeles
- cómo recuperar los datos (informes) que solicitó
debe hacerse cargo de la parte del modelo y olvida la r est. El contenido por completo y por debajo de la escritura de trabajo:
from sqlalchemy import create_engine, Column, Integer, Unicode, ForeignKey
from sqlalchemy.orm import relationship, scoped_session, sessionmaker
from sqlalchemy.orm.collections import attribute_mapped_collection
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.associationproxy import association_proxy
# Configure test data SA
engine = create_engine(u'sqlite:///:memory:', echo=False)
session = scoped_session(sessionmaker(bind=engine, autoflush=False))
Base = declarative_base()
class _BaseMixin(object):
"""
A helper mixin class to set properties on object creation.
Also provides a convenient default __repr__() function, but be aware that
also relationships are printed, which might result in loading the relation
objects from the database
"""
def __init__(self, **kwargs):
for k, v in kwargs.items():
setattr(self, k, v)
def __repr__(self):
return "<%s(%s)>" % (self.__class__.__name__,
', '.join('%s=%r' % (k, self.__dict__[k])
for k in sorted(self.__dict__)
if '_' != k[0]
#if '_sa_' != k[:4] and '_backref_' != k[:9]
)
)
# relation creator factory functions
def _creator_gr(group, role):
res = UserGroup(group=group, role=role)
return res
def _creator_ur(user, role):
res = UserGroup(user=user, role=role)
return res
##############################################################################
# Object Model
##############################################################################
class Role(Base, _BaseMixin):
__tablename__ = 'roles'
# columns
id = Column(Integer, primary_key=True, autoincrement=True)
name = Column(Unicode(16), unique=True)
# relations
usergroup = relationship("UserGroup", backref='role')
class User(Base, _BaseMixin):
__tablename__ = 'users'
# columns
id = Column(Integer, primary_key=True, autoincrement=True)
name = Column(Unicode(16), unique=True)
# relations
_rel_usergroup = relationship("UserGroup", collection_class=attribute_mapped_collection('group'),
cascade='all,delete-orphan',
backref='user',
)
groups = association_proxy('_rel_usergroup', 'role', creator=_creator_gr)
class Group(Base, _BaseMixin):
__tablename__ = 'groups'
# columns
id = Column(Integer, primary_key=True, autoincrement=True)
name = Column(Unicode(16), unique=True)
# relations
_rel_usergroup = relationship("UserGroup", collection_class=attribute_mapped_collection('user'),
cascade='all,delete-orphan',
backref='group',
)
users = association_proxy('_rel_usergroup', 'role', creator=_creator_ur)
class UserGroup(Base, _BaseMixin):
__tablename__ = 'user_group'
# columns
id = Column(Integer, primary_key=True, autoincrement=True)
user_id = Column(Integer, ForeignKey('users.id', ondelete='CASCADE'), nullable=False)
group_id = Column(Integer, ForeignKey('groups.id', ondelete='CASCADE'), nullable=False)
role_id = Column(Integer, ForeignKey('roles.id', ondelete='CASCADE'), nullable=False)
# relations
# (all backrefs)
##############################################################################
# TESTS (showing usages)
#
# Requirements:
# - list all groups of the user: user.groups (use keys)
# - list all users of the group: group.users (use keys)
# - get all users ordered (grouped) by group with the role title
##############################################################################
def _requirement_get_user_groups(user):
return user.groups.keys()
def _requirement_get_group_users(group):
return group.users.keys()
def _requirement_get_all_users_by_group_with_role():
qry = session.query(Group).order_by(Group.name)
res = []
for g in qry.all():
for u, r in sorted(g.users.items()):
value = (g.name, u.name, r.name)
res.append(value)
return res
def _test_all_requirements():
print '--requirement: all-ordered:'
for v in _requirement_get_all_users_by_group_with_role():
print v
print '--requirement: user-groups:'
for v in session.query(User).order_by(User.id):
print v, " has groups: ", _requirement_get_user_groups(v)
print '--requirement: group-users:'
for v in session.query(Group).order_by(Group.id):
print v, " has users: ", _requirement_get_group_users(v)
# create db schema
Base.metadata.create_all(engine)
##############################################################################
# CREATE TEST DATA
##############################################################################
# create entities
u_peter = User(name='u_Peter')
u_sonja = User(name='u_Sonja')
g_sales = Group(name='g_Sales')
g_wales = Group(name='g_Wales')
r_super = Role(name='r_Super')
r_minor = Role(name='r_Minor')
# helper functions
def _get_entity(entity, name):
return session.query(entity).filter_by(name=name).one()
def get_user(name):
return _get_entity(User, name)
def get_group(name):
return _get_entity(Group, name)
def _checkpoint():
session.commit()
session.expunge_all()
_test_all_requirements()
session.expunge_all()
print '-' * 80
# test: **ADD**
u_peter.groups[g_wales] = r_minor # add
g_wales.users[u_sonja] = r_super # add
g_sales.users[u_peter] = r_minor # add
session.add(g_wales)
#session.add(g_sales)
_checkpoint()
# test: **UPDATE**
u_peter = get_user('u_Peter')
assert u_peter.name == 'u_Peter' and len(u_peter.groups) == 2
assert len(u_peter.groups) == 2
g_wales = get_group('g_Wales')
g_wales.users[u_peter] = r_super # update
_checkpoint()
# test: **DELETE**
u_peter = get_user('u_Peter')
assert u_peter.name == 'u_Peter' and len(u_peter.groups) == 2
g_wales = get_group('g_Wales')
del u_peter.groups[g_wales] # delete
_checkpoint()
IS * papel * una etiqueta sencilla (columna) o se trata de otro atributo clave de la relación y, como tal, parte de la relación PK? Relacionado: ¿puede un usuario tener más de un rol en el mismo grupo? – van
Sí, el rol es una columna. Probablemente debería llamarse posición en su lugar. – dav
¿Y un usuario puede tener más de un rol/posición en el mismo grupo? – van