Hello all,
When using sqlalchemy 0.7 with sqlite, if I enter the path URI
incorrectly I will get an error like this:
OperationalError: (OperationalError) unable to open database file
None None
What does the "None None" signify? Would it be possible to change this
exception to be a bit more descriptive and a little less cryptic? eg.
Include the URI that failed?
Additionally, I notice that sqlalchemy doesn't attempt to make an
actual connection to the database until you perform the first query.
That means that code like this will appear to work:
Session = sessionmaker()
engine = create_engine('sqlite:///%s' % "invalid_filename")
Base.metadata.bind = engine
db_session = Session(bind=engine)
Yet eventually, when you make a query within your app code, you'll get
an exception because the URI was wrong. In my case, due to the
exception text being a little vague, I thought this was a problem with
my app's db access patterns (as I do things like delete the database
file manually) when it was just a problem with the initial connection.
I found a way to trigger this error earlier, by issuing
engine.connect() in the above routine, but I notice that this isn't
explicitly documented in "Using The Session" (http://
www.sqlalchemy.org/docs/orm/session.html). I expect I am not unusual
in wanting an error in session configuration to fail as soon as
possible, so if it's not possible or efficient to do this
automatically as part of creating the session, perhaps this part of
the docs could be clarified so that new users in future will know
exactly what to call to test this configuration? (In fact, this part
of the docs is a bit confusing in general - there seem to be a fair
few permutations of how to approach it - pass arguments to
sessionmaker? or to Session.configure? or to Session's constructor? -
and it's not clear why they all have to exist.)
--
Ben Sizer
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