youre expressing the secondary join condition on a many-to-many as
shoved into the primary join. SA will be confused by that, as it
requires knowledge of primary/secondary join conditions separately in
order to properly construct lazy loading criterion.
Group.mapper = mapper(Group, groups, properties = {
'members': relation(User, viewonly=True,
secondary=membership,
backref='groups',
primaryjoin=and_(membership.c.level==100,
membership.c.group_id==groups.c.id),
secondaryjoin=membership.c.user_id==users.c.id)
})
On Jun 12, 2007, at 11:53 PM, Michael Carter wrote:
> from sqlalchemy import *
> db = create_engine('sqlite://', echo=True)
> meta = BoundMetaData(db)
> session = create_session()
>
> groups = Table("groups", meta,
> Column("id",Integer, primary_key=True),
> Column("name", Unicode(40)))
>
> membership = Table("membership", meta,
> Column("user_id", Integer, ForeignKey("users.id"),
> primary_key=True),
> Column("group_id", Integer, ForeignKey("groups.id"),
> primary_key=True),
> Column("level", Integer))
>
> users = Table("users", meta,
> Column("id", Integer, primary_key=True),
> Column("name", Unicode(255)))
>
> class User(object):
> def __repr__(self): return str(self)
> def __str__(self): return "<User %s: %s>" % (self.id, self.name)
>
> class Group(object):
> def __repr__(self): return str(self)
> def __str__(self): return "<Group %s: %s>" % (self.id, self.name)
>
> class Membership(object):
> def __repr__(self): return str(self)
> def __str__(self): return "<Membership %s, %s: %s>" %
> (self.user_id, self.group_id, self.level)
>
>
> Group.mapper = mapper(Group, groups, properties = {
> 'members': relation(User, viewonly=True,
> secondary=membership, backref='groups',
> primaryjoin=and_(membership.c.user_id==users.c.id,
> membership.c.level==100, membership.c.group_id==groups.c.id)),
> })
>
> User.mapper = mapper(User, users, properties = {
> })
>
> Membership.mapper = mapper(Membership, membership, properties = {
> 'user': relation(User),
> 'group': relation(Group)
> })
>
> meta.drop_all()
> meta.create_all()
> u = User()
> g = Group()
> m = Membership()
> u.name = 'Michael Carter'
> g.name = 'Home'
> m.group = g
> m.user = u
> m.level = 100
> session.save(u)
> session.save(g)
> session.save(m)
> session.flush()
> print u.groups
> print g.members
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