I'm having a very strange issue with delete-orphan where I insert an item and
its parent becomes and orphan and gets deleted on session.flush(). I tried to
make a test case that reproduces the error, but was not successful. I also
tried to trace the problem to see where its originating. I payed particular
attention to InstrumentedAttribute.sethasparent(),
InstrumentedAttribute.hasparent() and Mapper._is_orphan().
First some background:
<class 'orderentry.model.Order'> is the parent type of
<OrderLineItem id=82>, which is the parent instance of
<OrderLineItemSize id=None>, which is the new item being inserted
Here's the pdb session where things start to get strange:
> .../lib/sqlalchemy/attributes.py(42)sethasparent()
-> if item is not None:
(pdb) n
> .../lib/sqlalchemy/attributes.py(43)sethasparent()
-> item._state[('hasparent', id(self))] = value
(pdb) item
<OrderLineItem id=82>
(pdb) id(self)
21105808 <----- NOTE THIS IS THE child's backref PROPERTY ID
(pdb) u
> .../lib/sqlalchemy/attributes.py(186)set()
-> self.sethasparent(value, True)
(pdb) obj
<OrderLineItemSize id=None>
Explanation: <OrderLineItem id=82>._state gets a ('hasparent', 21105808): True,
which refers to its sizes[0].lineItem UOWProperty instance. I.E. the child's
backref property is registered as the parent's parent property. I believe
that's a bug...
Here's the debug session where errors pop up during flush() due to
<OrderLineItem id=82> being flagged as an orphan even though it is not an
orphan at all
> .../lib/sqlalchemy/orm/mapper.py(144)_is_orphan()
-> for (key,klass) in self.delete_orphans:
(pdb) n
> .../lib/sqlalchemy/orm/mapper.py(145)_is_orphan()
-> if not getattr(klass, key).hasparent(obj):
(pdb)
> .../lib/sqlalchemy/orm/mapper.py(146)_is_orphan()
-> return True
(pdb) obj
<OrderLineItem id=82>
(pdb) key
'lineItems'
(pdb) klass
<class 'orderentry.model.Order'>
(pdb) obj.sizes[0]
<OrderLineItemSize id=None>
(pdb) obj.sizes[0].lineItem
<OrderLineItem id=82>
(pdb) obj._state
{('hasparent', 21105808): True, ... )}
(pdb) id(type(obj.sizes[0]).lineItem)
21105808 <----- NOTE THIS IS THE child's backref PROPERTY ID
Explanation: <OrderLineItem id=82> is checked for orphan-hood using the
'lineItems' property of Order (i.e. the correct parent property). The line item
has a 'hasparent' key in its _state, but its the wrong one (i.e. the hasparent
entry in _state points to the child's backref property, not the parent
property).
I realize this is very complicated and hard to follow. Is there something else
I can do to help find the problem?
Thanks,
~ Daniel
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