performance - 当跨实体组 (XG) 事务实际上只命中一个实体组时，它是否会产生开销？

Question

App Engine 最近宣布支持 Cross Group (XG) transactions ;人们会期望这些事务在跨多个实体组使用时会产生额外的开销，但如果我在事务开始时指定我想要一个 XG 事务，但实际上只访问一个实体组，我会看到显着的性能影响吗？

我问是因为 JDO 要求在持久性管理器级别指定 XG-ness，而且为所有事务打开它会简单得多(我只需要在少数情况下使用它)...

Answer 1

来自官方文档:

An XG transaction that touches only a single entity group behaves like a single-group transaction. Operations within such a transaction have the same performance and cost as in an equivalent single-group transaction with regard to billing and resource usage, but will experience higher latency.

来源: https://developers.google.com/appengine/docs/python/datastore/overview