If you do it properly, you can .get(primary_key) the user from the
SQLAlchemy session and it only hits the storage once per transaction. If the
object hasn't been garbage collected, subsequent .get() calls will hit the
identity map, which can be used as a kind of cache but which is really there
to make sure your code has a consistent idea of what objects look like
during a transaction.
The following will execute 100 queries in CPython:
Session = sessionmaker(create_engine('sqlite:///:memory:', echo=True),
weak_identity_map=True) # default
for i in range(100): # weak referenced user will be gc'd and re-queried
session.query(stucco_auth.tables.User).get(1)
One query, since we hold a reference to the user 'u':
Session = sessionmaker(create_engine('sqlite:///:memory:', echo=True),
weak_identity_map=True) # default
for i in range(100): # 'u' keeps user alive
u = session.query(stucco_auth.tables.User).get(1)
One query, since the session holds on to its objects:
Session = sessionmaker(create_engine('sqlite:///:memory:', echo=True),
weak_identity_map=False)
for i in range(100): # weak referenced user will be gc'd and re-queried
session.query(stucco_auth.tables.User).get(1)
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