I'm not *entirely* sure what's going on here, but it seems that when we
do something like
obj = OpaqueObject(...)
Session = sessionmaker(...)
session = Session()
...
session.add(obj)
session.commit()
the primary key (and maybe some foreign relations?) aren't automatically
populated on `obj` following the commit, and will attempt to lazy-load
on next reference. Since expire_on_commit defaults to True, the session
attached to `obj` (which is no longer the `session` in locals!) is closed
out when we later do
session = Session()
get_obj = session.query(OpaqueObject).filter(
ManagedObject.unique_identifier == obj.unique_identifier).one()
leading to a DetachedInstanceError.
There seem to be a few different ways we can fix this:
* Set expire_on_commit=False so the old session is still useful for the
lazy-loading.
* Re-use the same session instead of creating a new one.
* Explicitly refresh added objects post-commit.
Generally prefer the first one; there's some prior art to follow in
services/server/test_engine.py. Curiously, that same file runs into
trouble despite already setting expire_on_commit=False -- so do the
explicit refresh, on the assumption that there was a reason we went to
the trouble of creating a fresh session.
Closes#649
Added the ORM code to be able to persist OpaqueData in a database.
This added the code to the base class ManagedObject as well. Unit
tests are added to demonstrate the code is working correctly.
This change adds an OpaqueObject class to the Pie object hierarchy. A
unit test suite covering the class is included, as are updates to the
Pie object factory and associated tests.
