I am trying to get an collection of objects out of a database and pass it to another process that is not connected to the database. My code looks like the one below but I keep getting:
sqlalchemy.exc.UnboundExecutionError: Instance <MyClass at 0x8db7fec> is not bound to a Session; attribute refresh operation cannot proceed
When I try to look at the elements of my list outside of the get_list() method.
def get_list (obj):
sesson = Session()
lst = session.query(MyClass).all()
session.close()
return lst
However, if I use this:
def get_list_bis (obj)
session = Session()
return session.query(MyClass).all()
I am able to use the elements but worry about the state of the session since it was not closed.
What am I missing here?
If you want a bunch of objects produced by querying a session to be usable outside the scope of the session, you need to expunge them for the session.
In your first function example, you will need to add a line:
session.expunge_all()
before
session.close()
More generally, let's say the session is not closed right away, like in the first example. Perhaps this is a session that is kept active during entire duration of a web request or something like that. In such cases, you don't want to do expunge_all. You will want to be more surgical:
for item in lst:
session.expunge(item)