The attached test program generates the following exception with SA
0.2.6. What does the error:
Cant determine relation direction 'set([])'
mean?
Traceback (most recent call last):
File "test.py", line 56, in ?
order=Order()
File "build\bdist.win32\egg\sqlalchemy\orm\mapper.py", line 423, in init
File "build\bdist.win32\egg\sqlalchemy\orm\mapper.py", line 161, in compile
File "build\bdist.win32\egg\sqlalchemy\orm\mapper.py", line 387, in
_initialize_properties
File "build\bdist.win32\egg\sqlalchemy\orm\mapper.py", line 1129, in init
File "build\bdist.win32\egg\sqlalchemy\orm\properties.py", line 236,
in do_init
File "build\bdist.win32\egg\sqlalchemy\orm\properties.py", line 298,
in _get_direction
sqlalchemy.exceptions.ArgumentError: Cant determine relation direction
'set([])', for 'order_adjustments' in mapper 'Mapper|Or
derAdjustment|order_adjustment' with primary join
'orders.order_id = order_adjustment.order_id'
The special thing about the test script is that the table
'order_item_adjustment' has foreign key relationships with both the
table 'orders' and 'order_item'. And the column
'order_item_adjustment.order_id' is involved in BOTH of the two
relationships. So maybe SA has difficulty in identifying the column
involved in the relationship and I have to use primaryjoin to
explicitly specify the join condition.
What shall I do to create the relationships correctly?
--
Hong Yuan
大管家网上建材超市
装修装潢建材一站式购物
http://www.homemaster.cn
from sqlalchemy import *
engine=create_engine('sqlite:///:memory:', echo=True)
meta=BoundMetaData(engine)
t_order = Table('orders', meta,
Column('order_id', Integer, primary_key=True),
Column('customer_id', Integer),
)
t_order_item = Table('order_item', meta,
Column('order_id', Integer, ForeignKey('orders.order_id'), primary_key=True),
Column('order_item_seq_id', Integer, primary_key=True),
Column('item_name', String(40), nullable=False),
)
t_order_adjustment = Table('order_adjustment', meta,
Column('order_adjust_seq_id', Integer, primary_key=True),
Column('order_id', Integer, ForeignKey('orders.order_id'), nullable=False),
Column('order_item_seq_id', Integer),
Column('amount', Numeric(11,3)),
ForeignKeyConstraint(['order_id', 'order_item_seq_id'],
['order_item.order_id', 'order_item.order_item_seq_id'])
)
meta.create_all()
class Order(object): pass
class OrderItem(object): pass
class OrderAdjustment(object): pass
mapper(OrderAdjustment, t_order_adjustment)
mapper(OrderItem, t_order_item, properties={
'item_adjustments': relation(OrderAdjustment,
primaryjoin=
and_(t_order_item.c.order_id==t_order_adjustment.c.order_id,
t_order_item.c.order_item_seq_id==t_order_adjustment.c.order_item_seq_id),
lazy=True)
})
mapper(Order, t_order, properties={
'order_items': relation(OrderItem, lazy=True),
'order_adjustments': relation(OrderAdjustment,
primaryjoin=t_order.c.order_id==t_order_adjustment.c.order_id,
lazy=True)
})
session = create_session(bind_to=engine)
order=Order()
order.order_id=1
session.save(order)
session.flush()
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