I was looking at using a UUID as primary key for a table. Using the
backend-agnostic GUID type from
http://docs.sqlalchemy.org/en/rel_0_8/core/types.html#backend-agnostic-guid-type
I get strange behaviour though. I whipped up a simple test case:
class Data(BaseObject):
__tablename__ = 'data'
uuid = Column(GUID(), primary_key=True)
metadata.create_all()
session = sessionmaker(autocommit=False)()
uuid = 'ac4daeff-3af3-4b83-b8c7-3aa34e34151c'
obj = Data(uuid=uuid)
session.add(obj)
assert session.query(Data).get(uuid) is obj
assert session.query(Data).filter(Data.uuid == uuid).first() is obj
Both asserts fail when I do this. The problem appears to be conversion from to
a uuid.UUID instance in GUID.process_result_value: this always creates a new
UUID instance, which probably causes a miss when SQLAlchemy tries to find an
instance in its identify map.
Is this a bug in the GUID example in the documentation, or is this something
that can be improved in the identity map?
Wichert.
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