I have an application that will need to bind to several different
databases with the same structure. The databases to be accessed are
not known at import time, that will be determined later while the
application is running. I want to use declarative and autoload the
columns. Autoload needs a database connection available when a class
is first compiled to do the database introspection, that is the part I
can't figure out. Maybe a custom metaclass?
If this is already solved, can someone point me at the answer? I
haven't found it yet.
I want to do something like this:
# declare a class used to manage connections to database instances
class MyDatabase(object):
... magic happens here ...
class User(..??..):
__table_args__ = {'autoload':True}
etc.
def __init__(self, dbname):
self.engine = create_engine(.. usual create engine stuff ..)
self.metadata = MetaData(bind=engine)
self.Session = sessionmaker(bind=engine)
# probably have to do something here to create a self.User
class????
def getsession(self):
return self.Session()
then the application code does things like:
# something happens to determine a database to
# connect to as dbname
db = MyDatabase('dbname')
session = db.getsession()
users = session.query(db.User).all()
etc.
Now developers can connect to databases by name and have a ORM based
programming interface.
I have a solution that works well when I define columns in the class
definitions, but I am looking for a solution that lets me use
autoload.
Regards,
Mike
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