env.py 文件源码

def run_migrations_offline():
    """Run migrations in 'offline' mode.

    This configures the context with just a URL
    and not an Engine, though an Engine is acceptable
    here as well.  By skipping the Engine creation
    we don't even need a DBAPI to be available.
    Calls to context.execute() here emit the given string to the
    script output.
    """
    context.configure(
        url=config.get_main_option('sqlalchemy.url'),
        version_table=config.get_main_option('version_table'),
        literal_binds=True,
    )

    with context.begin_transaction():
        context.run_migrations()