QP interaction with the DB

I had recently dug into QP to discover exactly what it expects in terms 
of api from the DB, and then I extracted the methods into a separate 
class. In my QP-based environment, this class is then instantiated by 
the SIte's Publisher... (but more on this soon hopefully...)

In the light of the ongoing discussion of precisely the issue of what 
QP expects from the DB, here's the gutted version of that interface 
class, that I think speaks very clearly. In last release of QP, these 
methods have been re-organized, thus improving clarity in the source 
code itself.

To tell the whole story, one should keep in mind that there *is* a 
specific API that the Session and User class hierarchies are expected 
to implement... for example SessionDB.get(key), Session.is_valid(), 
Session.get_owner(), Session.set_authenticated(), User.has_password(), 
etc. However, in my variations I retained the same API's on these 
classes so I never worried about it too much.

Anyhow, as such, QP would not be at be able to know anything about how 
the Session and User classes are achieved... they could be thin 
wrappers of raw sql queires for that matter, and none of QP's features 
will be affected in any way (please correct me if I am wrong!). So, if 
anyone is reluctant to check QP out because of Durus... just do it ;)

But, the only place where there are any real Durus-specific assumptions 
is in the qp admin script itself. If the logic for starting and 
stopping the db, along with that for getting a connection (in 
Site.get_publisher()), are hooked out in some way, then QP in and of 
itself will have nothing that is Durus specific -- something that 
probably would be a good thing for both QP and Durus...


class QPDB(object):

     def __init__(self, connection=None):
         # Called by SitePublisher.__init__()

     def ensure_database_initialized(self):
         # Called from Publisher.__init__()

     def get_sessions(self):
         ''' () -> SessionDatabase '''
         # Called from Publisher.fill_response()

     def create_session(self):
         # Called from Publisher.fill_response()

     def get_users(self):
         ''' () -> UserDatabase '''
         # Called from Publisher.ensure_signed_in_*
         # Called from within session.py

     def create_user(self, userid, ...  ):
         # Not called from QP code outside User class

    def get_connection(self):
         # Called from Site.get_connection()
         # Initialized in Site.get_publisher()

     def commit(self):
         # shortcut on self.get_connection. commit()

     def abort(self):
         # shortcut on self.get_connection.abort()

     def get_root(self):
         # shortcut  on self.get_connection.get_root()