Not sure if __abstract__ is the way to go. Should I instead be creating
mixins?
http://docs.sqlalchemy.org/en/rel_0_9/orm/extensions/declarative.html#mixin-and-custom-base-classes
On Saturday, April 26, 2014 5:07:23 PM UTC-4, Brian Findlay wrote:
>
> My project requires querying an externally-managed database as well as a
> project-specific database. What I've been doing to date is copying the
> external database (which changes very infrequently) into the
> project-specific database so I only need one engine and one dbsession. I'm
> now trying to correct this monstrosity by binding the external-specific
> classes to the external engine, still using a single session.
>
> Per agronholm's suggestion on IRC, I'm attempting to do this via a base
> class for each database in order to avoid having to individually bind each
> class to the correct engine. Not quite sure how to proceed, though, because
> 'binds' isn't accepting my keys when those keys are empty base classes.
>
>
> from sqlalchemy.ext.declarative import declarative_base
> from sqlalchemy.orm import (
> scoped_session,
> sessionmaker
> )
> from zope.sqlalchemy import ZopeTransactionExtension
>
>
> Base = declarative_base()
> DBSession =
> scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
>
>
> class DB1(Base):
> __abstract__ = True
>
> class DB2(Base):
> __abstract__ = True
>
> class SomeInternalClass(DB1):
> __tablename__ = 'table_in_db1'
>
> class SomeExternalClass(DB2):
> __tablename__ = 'table_in_db2'
>
> db1_engine = engine_from_config(settings, 'sqlalchemy.db1.')
> db2_engine = engine_from_config(settings, 'sqlalchemy.db2.')
> DBSession.configure(binds={DB1:db1_engine, DB2:db2_engine})
>
>
> This raises an exception: sqlalchemy.exc.NoInspectionAvailable: No
> inspection system is available for object of type <class
> 'sqlalchemy.ext.declarative.api.DeclarativeMeta'>
>
>
> But when I keep the same class structure and switch back to the original
> bind, it works:
>
>
> DBSession.configure(bind=db1_engine)
>
>
> Of course, that means I'm back to using the monster database again. So
> what's wrong this?
>
>
> DBSession.configure(binds={DB1:db1_engine, DB2:db2_engine})
>
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