> It's not too bad, but you have to do your own custom app setup, and
> modify your init_model stuff to create multiple transaction manager.

> app_cfg.py:

> from webapp.model import init_model
> from sqlalchemy import engine_from_config
> from tg.configuration import AppConfig, Bunch
> from pylons import config as pylons_config

> class MyAppConfig(AppConfig):
>     def setup_sqlalchemy(self):
>         """Setup SQLAlchemy database engine"""
>         users_engine = engine_from_config(pylons_config,
> 'sqlalchemy_users.')
>         samples_engine = engine_from_config(pylons_config,
> 'sqlalchemy_samples.')
>         config['pylons.app_globals'].sa_engine = users_engine
>         config['pylons.app_globals'].sa_users_engine = users_engine
>         config['pylons.app_globals'].sa_samples_engine =
> samples_engine

>         # Pass the engine to initmodel, to be able to introspect
> tables
>         init_model(users_engine, samples_engine)

> base_config = MyAppConfig()
> ...

> model/__init__.py:

> import model.users
> import model.samples

> from model.users.mappers import *
> from model.samples.mappers import *

> from zope.sqlalchemy import ZopeTransactionExtension
> from sqlalchemy.orm import scoped_session, sessionmaker

> # Global session manager.  DBSession() returns the session object
> # appropriate for the current web request.
> maker = sessionmaker(autoflush=True, autocommit=False,
>                      extension=ZopeTransactionExtension())

> DBSession = UsersDBSession = scoped_session(maker)
> maker3 = sessionmaker(autoflush=True, autocommit=False,
>                      extension=ZopeTransactionExtension())

> SamplesDBSession = scoped_session(maker3)
> from model.users.metadata import metadata as users_metadata
> from model.samples.metadata import metadata as samples_metadata

> def init_model(users_engine, samples_engine):
>     """Call me before using any of the tables or classes in the
> model."""

>     global UsersDBSession, SamplesDBSession, users_metadata,
> samples_metadata

>     UsersDBSession.configure(bind=users_engine)
>     SamplesDBSession.configure(bind=samples_engine)

>     users_metadata.bind = users_engine
>     samples_metadata.bind = samples_engine

> This is sort of an off-the cuff answer, we will provide a better one
> in the next documentation release.

> Come find me on IRC if you need some more help.

> cheers.
> -chris

> On Jun 4, 10:31 am, Mike Driscoll <kyoso...@gmail.com> wrote:

> > Hi,

> > According to Mark Ramm's blog, supporting multiple databases is
> > supposed to be easy (seehttp://compoundthinking.com/blog/index.php/2008/07/31/10-reasons-why-...).
> > So where is the documentation that says how to do it??

> > I "think" I need to put multiple sqlalchemy.url's in my
> > development.ini file. But where oh where do I set up the SA engines
> > at? The model's __init__ claims to support multiple databases too
> > using MetaData, but it doesn't show where to bind the engine unless
> > you're supposed to use the undocumented init_model function somehow.

> > I'm pretty sure the init_model came from Perkins. Maybe he can tell me
> > where to put my call to the function and how to set it up for multiple
> > databases?

> > That would be great!

> > Thanks,

> > Mike

> > On May 28, 12:47 pm, Mike Driscoll <kyoso...@gmail.com> wrote:

> > > Hi,

> > > I am having a little trouble wrapping my head around how to configure
> > > my model's __init__.py file for multiple databases. I am working on an
> > > application that accesses 3 databases and does reflection on select
> > > tables from all three.

> > > I assume I need to comment out this line:

> > > metadata = DeclarativeBase.metadata

> > > and instead create three metadata instances based on MetaData(),
> > > correct?

> > > Finally, as I understand it, I can use the "init_model" function to do
> > > the mapping for some of them, but I am not understanding where to
> > > create the engine object to pass to it. Also, once I have my tables
> > > mapped in the function, what do I put in my real model file if
> > > anything?

> > > Hopefully that stuff makes sense. I am using Python 2.5 and TG2 in a
> > > virtualenv on Windows XP.

> > > Thanks!

> > > Mike