Alembic stamp command issues with sqlite in-memory db

Question

I'm experiencing some problems with alembic's stamp command and using sqlite in-memory databases for testing. Tests that work perfectly with file-based sqlite dbs fail with OperationalError: (OperationalError) no such table.

I'm stamping during initialisation to show the database is up-to-date:

def init_db(engine, version):
    tables.Base.metadata.create_all(engine)
    with engine.begin() as connection:
        stamp_alembic(connection)

def stamp_alembic(connection):
    from alembic import command
    from alembic.config import Config

    alembic_cfg = Config('alembic.ini')
    alembic_cfg.attributes['connection'] = connection
    command.stamp(alembic_cfg, 'head')

I'm passing the current connection to env.py as per the cookbook:

def run_migrations_online():
    connectable = config.attributes.get('connection', None)
    if connectable is None:
        # only create Engine if we don't have a Connection
        # from the outside
        connectable = engine_from_config(
            config.get_section(config.config_ini_section),
            prefix='sqlalchemy.',
            poolclass=pool.NullPool
        )
    with connectable.connect() as connection:
        context.configure(
            connection=connection,
            target_metadata=target_metadata
        )
        with context.begin_transaction():
            context.run_migrations()

My test class:

SETTINGS = {'sqlalchemy.url': 'sqlite:///:memory:'}

class TestOperatorUserModel(unittest.TestCase):
    def setUp(self):
        engine = engine_from_config(SETTINGS, 'sqlalchemy.')
        tables.DBSession.configure(bind=engine)
        init_db(engine, SETTINGS['version.db'])
        transaction.begin()

    def tearDown(self):
        engine = engine_from_config(SETTINGS, 'sqlalchemy.')
        transaction.abort()
        tables.Base.metadata.drop_all(engine)
        tables.DBSession.remove()

If I remove the stamp call from initialisation, the tests also run fine. As a workaround, I'm only stamping the db if engine.url.database isn't ':memory:', but I'd ideally like to know what is the real source of the issue.

Environment is Python 2.7.11, SQLAlchemy 0.9.10, alembic 0.8.6 and sqlite 2.8.17.

Alembic stamp command issues with sqlite in-memory db

0 Answers0