Using multiple databases with single sqlalchemy model

Question

I want to use multiple database engines with a single sqlalchemy database model.

Following situation: I have a photo album software (python) and the different album

Answer 1

You can achieve this with multiple engines and sessions (you don't need multiple metadata):

engine1 = create_engine("sqlite:///tmp1.db")
engine2 = create_engine("sqlite:///tmp2.db")
Base.metadata.create_all(bind=engine1)
Base.metadata.create_all(bind=engine2)
session1 = Session(bind=engine1)
session2 = Session(bind=engine2)
print(session1.query(Picture).all())  # []
print(session2.query(Picture).all())  # []
session1.add(Picture())
session1.commit()
print(session1.query(Picture).all())  # [Picture]
print(session2.query(Picture).all())  # []
session2.add(Picture())
session2.commit()
print(session1.query(Picture).all())  # [Picture]
print(session2.query(Picture).all())  # [Picture]
session1.close()
session2.close()

For scoped_session, you can create multiple of those as well.

engine1 = create_engine("sqlite:///tmp1.db")
engine2 = create_engine("sqlite:///tmp2.db")
Base.metadata.create_all(bind=engine1)
Base.metadata.create_all(bind=engine2)
Session1 = scoped_session(sessionmaker(bind=engine1))
Session2 = scoped_session(sessionmaker(bind=engine2))
session1 = Session1()
session2 = Session2()
...

If you have a variable number of databases you need to have open, scoped_session might be a little cumbersome. You'll need some way to keep track of them.