def run_migrations_online():
    """Run migrations in 'online' mode.

    In this scenario we need to create an Engine
    and associate a connection with the context.

    """

    # for the direct-to-DB use case, start a transaction on all
    # engines, then run all migrations, then commit all transactions.

    engines = {}
    for name in re.split(r',\s*', db_names):
        engines[name] = rec = {}
        rec['engine'] = engine_from_config(
            context.config.get_section(name),
            prefix='sqlalchemy.',
            poolclass=pool.NullPool)

    for name, rec in engines.items():
        engine = rec['engine']
        rec['connection'] = conn = engine.connect()

        if USE_TWOPHASE:
            rec['transaction'] = conn.begin_twophase()
        else:
            rec['transaction'] = conn.begin()

    try:
        for name, rec in engines.items():
            logger.info("Migrating database %s" % name)
            context.configure(
                connection=rec['connection'],
                upgrade_token="%s_upgrades" % name,
                downgrade_token="%s_downgrades" + name,
                target_metadata=target_metadata.get(name)
            )
            context.run_migrations(engine_name=name)

        if USE_TWOPHASE:
            for rec in engines.values():
                rec['transaction'].prepare()

        for rec in engines.values():
            rec['transaction'].commit()
    except:
        for rec in engines.values():
            rec['transaction'].rollback()
        raise
    finally:
        for rec in engines.values():
            rec['connection'].close()
dataset/ETHPy150Open quantmind/lux/lux/extensions/odm/commands/template/lux/env.py/run_migrations_online/operator `%` -> `+`