By popular request, I'm sticking what I did on here:
I used the pylons docs to figure out part of this:
http://www.pylonshq.com/docs/en/0.9.7/models/#multiple-engines
Here are the files to change:
#--------------
# development.ini
# create 2 or more sqlalchemy urls
sqlalchemy.main.url = sqlite:///%(here)s/devdata.db
sqlalchemy.other.url = sqlite:///%(here)s/devdata2.db
# -------------------------------------------
#--------------
# app_cfg.py (which is in the config folder)
# need to subclass AppConfig and
# override setup_sqlalchemy
from sqlalchemy import engine_from_config
from pyretention.model import init_model
class MyAppConfig(AppConfig):
def setup_sqlalchemy(self):
"""Setup SQLAlchemy database engine."""
engineOne = engine_from_config(pylons_config,
'sqlalchemy.main.')
engineTwo = engine_from_config(pylons_config,
'sqlalchemy.other.')
config['pylons.app_globals'].engineOne = engineOne
config['pylons.app_globals'].engineTwo = engineTwo
# Pass the engine to initmodel, to be able to introspect
tables
init_model(engineOne, engineTwo)
base_config = MyAppConfig()
# -------------------------------------------
#--------------
# model\__init__.py
# Global session manager: DBSession() returns the Thread-local
# session object appropriate for the current web request.
maker = sessionmaker(autoflush=True, autocommit=False,
extension=ZopeTransactionExtension())
DBSession = scoped_session(maker)
maker2 = sessionmaker(autoflush=True, autocommit=False,
extension=ZopeTransactionExtension())
secondSession = scoped_session(maker2)
def init_model(engineOne, engineTwo):
"""Call me before using any of the tables or classes in the
model."""
DBSession.configure(bind=engineTwo)
secondSession.configure(bind=engineOne)
# you only need this metadata
#if you want to autoload a table
second_metadata = MetaData(engineOne)
# -------------------------------------------
Note that in websetup, there is a call to
model.metadata.create_all(bind=config['pylons.app_globals'].sa_engine)
So when you override AppConfig in app_cfg.py, you'll want to change
one of these lines or hack websetup.py and any other references to
sa_engine:
config['pylons.app_globals'].engineOne = engineOne
config['pylons.app_globals'].engineTwo = engineTwo
to
config['pylons.app_globals'].sa_engine = engineOne
Hope that helps others.
- Mike
On Jun 9, 9:10 am, Mike Driscoll <[email protected]> wrote:
> For the record, this was resolved. I didn't know how to set up the
> second session object.
>
> Thanks!
>
> Mike
>
> On Jun 5, 2:06 pm, percious <[email protected]> wrote:
>
> > 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 <[email protected]> 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 <[email protected]> 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
>
>
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