On Mar 23, 2011, at 11:28 AM, [email protected] wrote:
> Hello everyone,
>
> I am currently working on a Pylons project, and keep on receiving the
> following error from SQLAlchemy:
>
> InvalidRequestError: stale association proxy, parent object has gone
> out of scope
this is because the parent is being garbage collected while the association
proxy is still doing its work:
# will not work with immediate gc
for item in session.query(Order).first().items:
print item
the solution is to do it like this:
o1 = session.query(Order).first()
for item in o1.items:
print item
example is attached.
>
> Here is the code for the model:
>
> class AccountInfo(Base):
> __tablename__ = 'account_info'
>
> userid = schema.Column(types.Integer,
> schema.ForeignKey("users.id"), nullable=False, primary_key=True)
> enabled = schema.Column(types.Integer, default=1)
> username = schema.Column(types.Unicode(25), nullable=False,unique=True)
> password = schema.Column(types.Unicode(255), default=u'password')
> #leveled_privs = orm.relation("PrivilegeLevel",
> backref="account_info",
> collection_class=attribute_mapped_collection('priv_id'))
> # Below creates a relationship between AccountInfo and
> PrivilegeLevel placed into a dict sorted by priv_id
> perms = orm.relation("Privilege", secondary=privileges_assoc)#,
> backref="account_info")
> privileges = association_proxy("perms","name")
> def __init__(self,info):
> for k,v in info:
> setattr(self, k, v)
>
> "privileges" is the source of the problem. Whenever I try to use it in
> the site, I get the previously mentioned error. I've taken a look at
> the documentation on the site, and I believe that I am using it
> correctly.
>
> When I searched google, I wasn't able to find anything useful. I did
> find something about removing stale cached attribute instances here:
> http://www.mail-archive.com/[email protected]/msg08914.html
>
> But I couldn't find any attributes on my instances that seemed similar
> to what that user was speaking about.
>
> Here's an example of how I'm using it, if that helps:
>
>> "edit.perms" in myAccountInfoInstance.privileges
> True
>
> In the Python shell, it works occasionally. In a request, not at all
>
> Is anyone able to help me?
>
> Cody
>
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from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.associationproxy import association_proxy
Base = declarative_base()
class Order(Base):
__tablename__ = 'order'
order_id = Column(Integer, primary_key=True)
order_items = relationship("OrderItem",)
items = association_proxy("order_items", "item")
class Item(Base):
__tablename__ = 'item'
item_id = Column(Integer, primary_key=True)
class OrderItem(Base):
__tablename__ = 'orderitem'
order_id = Column(Integer, ForeignKey('order.order_id'), primary_key=True)
item_id = Column(Integer, ForeignKey('item.item_id'), primary_key=True)
price = Column(Float, nullable=False)
item = relationship(Item)
engine = create_engine('sqlite://')
Base.metadata.create_all(engine)
session = Session(engine)
i1, i2, i3 = Item(), Item(), Item()
o1 = Order(order_items=[
OrderItem(item=i1, price=5),
OrderItem(item=i2, price=20),
OrderItem(item=i3, price=10),
])
session.add(o1)
del o1
# will work
o1 = session.query(Order).first()
for item in o1.items:
print item
del o1
# will not work with immediate gc
for item in session.query(Order).first().items:
print item
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