use backref=backref(somename, lazy=False, <otherargs>).
On Oct 23, 2006, at 8:19 AM, Maciej Szumocki wrote:
>
> After some more testing (the use of loggers in sqlalchemy helped alot
> :)) i have narrowed the issue to backreference creation - they seem to
> be always created lazy, even if relation is set to eager. Here's a
> simple test script (not in unittest format unfortunately as i'm not
> sure how to make one that would work within sqlalchemy unittest
> framework).
>
> from sqlalchemy import *
> dburi = "put your own here"
>
> import logging
> #logging.getLogger("sqlalchemy.orm.mapper.Mapper").setLevel(1)
> #logging.getLogger("sqlalchemy.orm.strategies.EagerLoader").setLevel
> (1)
> #uncomment if you want to see what exactly is going on
>
> engine = create_engine(dburi, strategy='plain', echo=True)
> metadata = BoundMetaData(engine)
>
> middle = Table('middle', metadata,
> Column('id', Integer, primary_key = True, autoincrement=True),
> Column('data', String(50)),
> )
>
> left = Table('left', metadata,
> Column('id', Integer, ForeignKey(middle.c.id), primary_key=True),
> Column('tag', String(50), primary_key=True),
> )
>
> right = Table('right', metadata,
> Column('id', Integer, ForeignKey(middle.c.id), primary_key=True),
> Column('tag', String(50), primary_key=True),
> )
>
> class Middle(object):
> def __init__(self, data): self.data = data
> class Left(object):
> def __init__(self, data): self.tag = data
> class Right(object):
> def __init__(self, data): self.tag = data
>
> mapper(Left, left)
> mapper(Right, right)
> mapper(Middle, middle, properties = {
> 'left': relation(Left, private=True, lazy=False, backref='middle',
> foreignkey=left.c.id, primaryjoin = left.c.id==middle.c.id ),
> 'right': relation(Right, private=True, lazy=False,
> backref='middle',
> foreignkey=right.c.id, primaryjoin = right.c.id==middle.c.id
> ),
> }
> )
>
> def make_data():
> session = create_session(bind_to=engine)
> p = Middle('test1')
> p.left.append(Left('tag1'))
> p.right.append(Right('tag2'))
> session.save(p)
> session.flush()
>
> def test(close_session):
> session = create_session(bind_to=engine)
> obj = session.query(Left).get_by(tag='tag1')
> if close_session:
> session.close()
> print obj.middle.right[0]
>
> if __name__=="__main__":
> metadata.create_all()
> try:
> make_data()
> test(False) # will work fine
> test(True) # will fail
> finally:
> metadata.drop_all()
>
>
> >
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