什么是sqlalchemy中MapperExtension的`connection`参数? [英] What is the `connection` parameter of MapperExtension in sqlalchemy?
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问题描述
类 MapperExtension
有一些方法, before_insert
, before_update
,...都有一个参数连接
。
The class MapperExtension
has some methods, and before_insert
, before_update
, ... all have a parameter connection
.
def before_insert(self, mapper, connection, instance):
c $ c> MapperExtension ,但是没有发现这个连接
。它是什么?如何使用它?
I've read the documents of MapperExtension
, but found nothing about this connection
. What is it? And how to use it?
推荐答案
这是 Connection
class 。最新版本的SQLAlchemy发行版有示例目录,请参阅 examples / nested_sets / nested_sets.py 来了解如何在mapper扩展中使用它。
It's an instance of Connection
class. Recent versions of SQLAlchemy distribution have examples directory, see examples/nested_sets/nested_sets.py to get an idea on how to use it in mapper extension.
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