I'm having trouble unpickling model instances where the class has an
attribute-mapped collection:
import pickle
from sqlalchemy import create_engine, Column, Integer, Unicode, ForeignKey
from sqlalchemy.orm import Session, relationship
from sqlalchemy.orm.collections import attribute_mapped_collection
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
engine = create_engine('sqlite:///')
session = Session(engine)
class Parent(Base):
__tablename__ = 'parents'
id = Column(Integer, primary_key=True)
children = relationship('Child', cascade='all, delete-orphan',
lazy='subquery', collection_class=attribute_mapped_collection('key'))
class Child(Base):
__tablename__ = 'children'
parent_id = Column(Integer, ForeignKey(Parent.id), primary_key=True)
key = Column(Integer, primary_key=True)
value = Column(Unicode)
Base.metadata.create_all(engine)
parent = Parent()
session.add(parent)
session.flush()
session.refresh(parent)
pickled = pickle.dumps(parent, 2)
pickle.loads(pickled)
Executing this results in:
Traceback (most recent call last):
File "sqlatest.py", line 32, in <module>
pickle.loads(pickled)
File "/usr/lib/python2.7/pickle.py", line 1382, in loads
return Unpickler(file).load()
File "/usr/lib/python2.7/pickle.py", line 858, in load
dispatch[key](self)
File "/usr/lib/python2.7/pickle.py", line 1083, in load_newobj
obj = cls.__new__(cls, *args)
TypeError: attrgetter expected 1 arguments, got 0
If I remove the relationship, pickling and unpickling work fine. None of
the other mapped collection variants work either, though they produce
different tracebacks. Is this a bug or am I doing something wrong?
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