#25426: pickling SimpleLazyObject fails just after accessing related object of
wrapped model instance.
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Reporter: iru | Owner: nobody
Type: Bug | Status: new
Component: Core (Serialization) | Version: 1.8
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Reproduction step :
{{{
import pickle
import django
django.setup()
from django.contrib.auth.models import User
from django.utils.functional import SimpleLazyObject
u = User.objects.select_related('profile').get(id=153)
o = SimpleLazyObject(lambda :u)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python2.7/pickle.py", line 1374, in dumps
Pickler(file, protocol).dump(obj)
File "/usr/local/lib/python2.7/pickle.py", line 224, in dump
self.save(obj)
File "/usr/local/lib/python2.7/pickle.py", line 331, in save
self.save_reduce(obj=obj, *rv)
File "/usr/local/lib/python2.7/pickle.py", line 419, in save_reduce
save(state)
File "/usr/local/lib/python2.7/pickle.py", line 286, in save
f(self, obj) # Call unbound method with explicit self
File "/usr/local/lib/python2.7/pickle.py", line 649, in save_dict
self._batch_setitems(obj.iteritems())
File "/usr/local/lib/python2.7/pickle.py", line 661, in _batch_setitems
for k, v in items:
RuntimeError: dictionary changed size during iteration
pickle.dumps(o) # SUCCEEDS
}}}
This also fails :
{{{
u = User.objects.get(id=153)
o = SimpleLazyObject(lambda :u)
o.profile
pickle.dumps(o)
}}}
This looks to be related with change in Model.__reduce__ in django 1.8
adding DJANGO_VERSION_PICKLE_KEY in __dict__
{{{
def __reduce__(self):
"""
Provides pickling support. Normally, this just dispatches to
Python's
standard handling. However, for models with deferred field
loading, we
need to do things manually, as they're dynamically created classes
and
only module-level classes can be pickled by the default path.
"""
data = self.__dict__
data[DJANGO_VERSION_PICKLE_KEY] = get_version()
if not self._deferred:
class_id = self._meta.app_label, self._meta.object_name
return model_unpickle, (class_id, [], simple_class_factory),
data
defers = []
for field in self._meta.fields:
if isinstance(self.__class__.__dict__.get(field.attname),
DeferredAttribute):
defers.append(field.attname)
model = self._meta.proxy_for_model
class_id = model._meta.app_label, model._meta.object_name
return (model_unpickle, (class_id, defers,
deferred_class_factory), data)
}}}
This is quite hard to patch if we just pass
--
Ticket URL: <https://code.djangoproject.com/ticket/25426>
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