sqlalchemy中MapperExtension的`connection`参数是什么? [英] What is the `connection` parameter of MapperExtension in sqlalchemy?

问题描述

MapperExtension类有一些方法，before_insert,before_update,...都有参数connection.

The class MapperExtension has some methods, and before_insert, before_update, ... all have a parameter connection.

def before_insert(self, mapper, connection, instance):

我已经阅读了 MapperExtension 的文档，但是没有找到关于这个 connection 的信息.它是什么?以及如何使用?

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

它是 Connection 类.SQLAlchemy 发行版的最新版本有示例目录，请参阅 examples/nested_sets/nested_sets.py 了解如何在映射器扩展中使用它.

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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