engine.py 文件源码

def __init__(self, pool, dialect, url, logging_name=None, echo=None,
                 execution_options=None, loop=None, **kwargs):

        self._engine = Engine(
            pool, dialect, url, logging_name=logging_name, echo=echo,
            execution_options=execution_options, **kwargs)

        self._loop = loop

        max_workers = None

        # https://www.python.org/dev/peps/pep-0249/#threadsafety
        if dialect.dbapi.threadsafety < 2:
            # This might seem overly-restrictive, but when we instantiate an
            # AsyncioResultProxy from AsyncioEngine.execute, subsequent
            # fetchone calls could be in different threads. Let's limit to one.
            max_workers = 1

        self._engine_executor = ThreadPoolExecutor(max_workers=max_workers)