[Chicago] help from Django and Pylons developers

[Massimo Di Pierro]

How would you handle the case when the two databases have a table  
with the same name?
Is it a problem?

Massimo


On Apr 28, 2008, at 3:27 PM, Kumar McMillan wrote:

> On Mon, Apr 28, 2008 at 3:15 PM, Kumar McMillan
> <kumar.mcmillan at gmail.com> wrote:
>> On Mon, Apr 28, 2008 at 1:18 PM, Ian Bicking <ianb at colorstudy.com>  
>> wrote:
>>>> I have never a Pylons example for connecting to multiple  
>>>> databases. Would
>>> you mind posting an example?
>>>>
>>
>>  I can't find this documented anywhere but if you configure a Pylons
>>  app with this structure (using SQLAlchemy 0.4),
> http://wiki.pylonshq.com/display/pylonsdocs/Using+SQLAlchemy+with 
> +Pylons
>
> duh, an example of multiple databases is actually at the bottom of
> that same page! ;)
>
> They suggest more or less the same thing but it's a little more
> concise and the session construction is more sane ...
>
> [app:main]
> sqlalchemy.default.url = "mysql://..."
> sqlalchemy.default.pool_recycle = 3600
> sqlalchemy.log.url = "sqlite://..."
>
> default_engine = engine_from_config(config, 'sqlalchemy.default.')
> log_engine = engine_from_config(config, 'sqlalchemy.log.')
> init_model(default_engine, log_engine)
>
> ...and so on
>
>
>>
>>  ... then, if you wanted to, say, connect to a read-only db and a
>>  write-only db, you could update your config like this:
>>
>>  [app:main]
>>  # ...
>>  read_db.url = postgres://read_user:pw@readhost/read_db
>>  #read_db.debug = True
>>  write_db.url = postgres://write_user:pw@writehost/write_db
>>
>>  ... and you could change environment.py to call init_model() like:
>>
>>  def load_environment(global_conf, app_conf):
>>     # ...
>>     read_engine = engine_from_config(config, 'read_db.')
>>     write_engine = engine_from_config(config, 'write_db.')
>>     init_model(read_engine, write_engine)
>>
>>  ... and update the init_model() def in model/__init__.py to :
>>
>>  from sqlalchemy import orm
>>  from myapp.model import meta
>>
>>  def init_model(read_engine, write_engine):
>>     ReadSession = orm.scoped_session(orm.sessionmaker 
>> (autoflush=False,
>>  transactional=False, bind=read_engine))
>>     meta.read_metadata.bind = read_engine
>>     meta.read_session = ReadSession()
>>     # setup read mappers here..
>>
>>     WriteSession = orm.scoped_session(orm.sessionmaker 
>> (autoflush=True,
>>  transactional=True, bind=write_engine))
>>     meta.write_metadata.bind = write_engine
>>     meta.write_session = WriteSession()
>>     # setup write mappers here..
>>
>>
>>  In other words, the config file is just a place to store values, any
>>  values you want, and the environment.py module gives you the  
>> chance to
>>  customize the initialization of your app any way you want.  You  
>> store
>>  the initialization code wherever you want, Pylons doesn't force any
>>  conventions on you other than by creating a default module layout  
>> when
>>  you start your project.
>>
>>  Kumar
>>
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