[web2py] Update record in session

[scausten]

Is is possible to hold a record in session, something like:

id = db.transactions.insert()
session.transaction = db.transactions[id]

and directly update_record the session.transaction,

session.transaction.update_record(x=y)        # This throws KeyError:
'update_record'

or is it necessary to reselect the record each time the controller is
called?

if session.transaction:
      transaction=db.transaction[session.transaction.id]
      transaction.update_record(x=y)