November 2021
Intermediate to advanced
410 pages
12h 1m
Chinese
Content preview from MongoDB权威指南（第3版）
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168
｜
第
8
章
证数据和数据库状态的有效性，即使在出现断电或其他错误的情况下也是如此。
原子性确保了事务中的所有操作要么都被应用，要么都不被应用。事务永远不能应用部分
操作，要么被提交，要么被中止。
一致性确保了如果事务成功，那么数据库将从一个一致性状态转移到下一个一致性状态。
隔离性是允许多个事务同时在数据库中运行的属性。它保证了一个事务不会查看到任何其他
事务的部分结果，这意味着多个事务并行运行与依次运行每个事务所获得的结果相同。
持久性确保了在提交事务时，即使系统发生故障，所有数据也都会保持持久化。
当数据库满足所有这些属性并且只有成功的事务才会被处理时，它就被称为是符合
ACID
的数据库。如果在事务完成之前发生故障，那么
ACID
确保不会更改任何数据。
MongoDB
是一个分布式数据库
，它支持跨副本集和
/
或分片的
ACID
事务。网络层增加了
额外的复杂性。
MongoDB
的工程团队提供了一些记录和谈话视频
，描述了他们是如何实
现支持
ACID
事务的必要特性的。
8.2
如何使用事务
MongoDB
提供了两种
API
来使用事务。第一种是与关系数据库类似的语法（如
start_
transaction
和
commit_transaction
），称为核心
API
；第二种称为回调
API
，这是使用事
务的推荐方法。
核心
API
不为大多数错误提供重试逻辑
，它要求开发人员为操作、事务提交函数以及所需
的任何重试和错误逻辑手动编写代码。
与核心
API
不
同，回调
API
提供了一个单独的函数，该函数封装了大量功能，包括启动与
指定逻辑会话关联的事务、执行作为回调函数提供的函数以及提交事务（或在出现错误时 ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.