blocks|key|4830970|text|MongoDB+4.0现在添加了对多文档ACID事务的支持。参考See+Refrence|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4830971|entityMap|0|LINK|mutability|MUTABLE|url|https://www.mongodb.com/transactions^0|W|C|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

MongoDB 4.0 adds support for multi-document ACID transactions now.
For reference
<a href="https://www.mongodb.com/transactions" rel="noreferrer">See Refrence</a>

blocks|key|1980721|text|MongoDB不支持multi-document事务。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1980722|但是，MongoDB确实提供了对单个文档的原子操作。通常，这些文档级原子操作足以解决在关系数据库中需要ACID事务的问题。|1980723|例如，在MongoDB中，您可以将相关数据嵌入到单个文档中的嵌套数组或嵌套文档中，并在单个原子操作中更新整个文档。关系数据库可能用多个表和行来表示同一类型的数据，这将需要事务支持才能自动更新数据。|1980724|entityMap^0|A|E|0|3|1M|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|R|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|K|$]]

MongoDB does not support multi-document transactions.

However, MongoDB does provide atomic operations on a single document. Often these document-level atomic operations are sufficient to solve problems that would require ACID transactions in a relational database.

For example, in MongoDB, you can embed related data in nested arrays or nested documents within a single document and update the entire document in a single atomic operation. Relational databases might represent the same kind of data with multiple tables and rows, which would require transaction support to update the data atomically.

blocks|key|68158|text|MongoDB不支持事务，但是保存一个文档是原子的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|68159|因此，最好将数据库模式设计为这样一种方式，即所有需要原子保存的数据都放在一个文档中。|68160|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

MongoDB doesn't support transactions, but saving one document is atomic.

So, it is better to design you database schema in such a way, that all the data needed to be saved atomically will be placed in one document.

blocks|key|69081|text|MongoDB不支持关系数据库中的事务。事务中的ACID公设是由MySQL中的存储引擎提供的完全不同的功能|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|69082|MySQL中的InnoDB+engine的一些功能：|69083|69084|Crash+Recovery|unordered-list-item|69085|Double+write+buffer|69086|69087|+settings|69088|Isolation+Level|69089|自动提交|69090|这是MongoDB社区所说的：|69091|MongoDB不支持传统的锁定或使用回滚的复杂事务。|69092|MongoDB的目标是轻量级、快速和可预测的性能。通过保持非常简单的事务支持，MongoDB可以提供更高的性能，特别是对于具有多个数据库服务器进程的分区或复制系统。|69093|事务的目的是确保在发生多个操作时，整个数据库保持一致。|69094|但与大多数关系数据库相反，MongoDB并不是设计为在单个主机上运行的。它被设计为多个分片的集群，其中每个分片都是多个服务器的副本集(可选地位于不同的地理位置)。|69095|但如果您仍在寻找使事务成为可能的方法：|69096|69097|尝试使用Mongo提供的文档级原子性mongo中的|69098|两阶段提交为基本Mongo提供了简单的事务机制构建在Mongo之上，还支持他们所说的|69099|+MySQL和Mongo|69100|的混合事务|69101|entityMap^0|0|11|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1H|8|@$9|1I|A|1J|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1K|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]|$1|I|3|J|5|K|7|1M|8|@]|D|@]|E|$]]|$1|L|3|M|5|K|7|1N|8|@]|D|@]|E|$]]|$1|N|3|-4|5|K|7|1O|8|@]|D|@]|E|$]]|$1|O|3|P|5|K|7|1P|8|@]|D|@]|E|$]]|$1|Q|3|R|5|K|7|1Q|8|@]|D|@]|E|$]]|$1|S|3|T|5|6|7|1R|8|@]|D|@]|E|$]]|$1|U|3|V|5|6|7|1S|8|@]|D|@]|E|$]]|$1|W|3|X|5|6|7|1T|8|@]|D|@]|E|$]]|$1|Y|3|Z|5|6|7|1U|8|@]|D|@]|E|$]]|$1|10|3|11|5|6|7|1V|8|@]|D|@]|E|$]]|$1|12|3|13|5|6|7|1W|8|@]|D|@]|E|$]]|$1|14|3|15|5|6|7|1X|8|@]|D|@]|E|$]]|$1|16|3|-4|5|6|7|1Y|8|@]|D|@]|E|$]]|$1|17|3|18|5|K|7|1Z|8|@]|D|@]|E|$]]|$1|19|3|1A|5|K|7|20|8|@]|D|@]|E|$]]|$1|1B|3|1C|5|K|7|21|8|@]|D|@]|E|$]]|$1|1D|3|1E|5|6|7|22|8|@]|D|@]|E|$]]|$1|1F|3|-4|5|6|7|23|8|@]|D|@]|E|$]]]|1G|$]]

MongoDB does not support transactions as in Relational DB. ACID postulates in transactions is a complete different functionality provided by storage engines in MySQL

Some of the features of InnoDB engine in MySQL:

<ul>
<li>Crash Recovery</li>
<li>Double write buffer</li>
<li>Auto commit settings</li>
<li>Isolation Level</li>
</ul>

This is what MongoDB community has to say:

MongoDB does not have support for traditional locking or complex transactions with rollback. 

MongoDB aims to be lightweight, fast, and predictable in its performance. By keeping transaction support extremely simple, MongoDB can provide greater performance especially for partitioned or replicated systems with a number of database server processes.

The purpose of a transaction is to make sure that the whole database stays consistent while multiple operations take place. 

But in contrary to most relational databases, MongoDB isn't designed to run on a single host. It is designed to be set up as a cluster of multiple shards where each shard is a replica-sets of multiple servers (optionally at different geographical locations).

But if you are still looking for way to make transactions possible:

<ul>
<li>Try using document level atomicity provided by mongo</li>
<li>two phase commit in Mongo provides simple transaction mechanism for basic operations</li>
<li>mongomvcc is built on the top of mongo and also supports transaction as they say</li>
<li>Hybrid of MySQL and Mongo</li>
</ul>

blocks|key|69059|text|使用此处描述的两阶段提交方法的多文档更新或“多文档事务”：http://docs.mongodb.org/manual/tutorial/perform-two-phase-commits/|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|69060|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.mongodb.org/manual/tutorial/perform-two-phase-commits/^0|T|1U|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Multi-document updates or “multi-document transactions” using a two-phase commit approac described here: <a href="http://docs.mongodb.org/manual/tutorial/perform-two-phase-commits/" rel="nofollow">http://docs.mongodb.org/manual/tutorial/perform-two-phase-commits/</a>

blocks|key|4830932|text|这个问题已经很老了，但是对于任何偶然发现这个页面的人来说，你可以使用fawn。这是一个解决这个问题的npm包。披露:这是我写的|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4830933|假设你有两个银行账户，一个属于约翰·史密斯，另一个属于破产个人。你想从约翰·史密斯那里转账20美元给破产的个人。假设所有名字和姓氏对都是唯一的，则可能如下所示：|4830934|var+Fawn+=+require("fawn");
var+task+=+Fawn.Task()

//assuming+"Accounts"+is+the+Accounts+collection+
task.update("Accounts",+{firstName:+"John",+lastName:+"Smith"},+{$inc:+{balance:+-20}})
++.update("Accounts",+{firstName:+"Broke",+lastName:+"Individual"},+{$inc:+{balance:+20}})
++.run()
++.then(function(){
++++//update+is+complete+
++})
++.catch(function(err){
++++//+Everything+has+been+rolled+back.+

++++//log+the+error+which+caused+the+failure+
++++console.log(err);
++});|code-block|syntax|javascript|4830935|注意:任务目前并不是孤立的(正在处理)，因此，从技术上讲，两个任务可以检索和编辑同一文档，因为这就是MongoDB的工作方式。|4830936|它实际上只是教程站点上的两阶段提交示例的通用实现：https://docs.mongodb.com/manual/tutorial/perform-two-phase-commits/|4830937|entityMap|0|LINK|mutability|MUTABLE|url|https://www.npmjs.com/package/fawn|1|https://docs.mongodb.com/manual/tutorial/perform-two-phase-commits/^0|Y|4|0|0|0|0|0|P|1V|1|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|13|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|C|$]]|$1|M|3|N|5|6|7|15|8|@]|9|@$A|16|B|17|1|18]]|C|$]]|$1|O|3|-4|5|6|7|19|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]|W|$5|R|S|T|C|$U|X]]]]

This question is quite old but for anyone who stumbles upon this page, you could use <a href="https://www.npmjs.com/package/fawn" rel="nofollow noreferrer">fawn</a>. It's an npm package that solves this exact problem. Disclosure: I wrote it

Say you have two bank accounts, one belongs to John Smith and the other belongs to Broke Individual. You would like to transfer $20 from John Smith to Broke Individual. Assuming all first name and last name pairs are unique, this might look like:

<pre><code>var Fawn = require("fawn");
var task = Fawn.Task()

//assuming "Accounts" is the Accounts collection 
task.update("Accounts", {firstName: "John", lastName: "Smith"}, {$inc: {balance: -20}})
 .update("Accounts", {firstName: "Broke", lastName: "Individual"}, {$inc: {balance: 20}})
 .run()
 .then(function(){
 //update is complete 
 })
 .catch(function(err){
 // Everything has been rolled back. 

 //log the error which caused the failure 
 console.log(err);
 });
</code></pre>

Caveat:
tasks are currently not isolated(working on that) so, technically, it's possible for two tasks to retrieve and edit the same document just because that's how MongoDB works. 

It's really just a generic implementation of the two phase commit example on the tutorial site: <a href="https://docs.mongodb.com/manual/tutorial/perform-two-phase-commits/" rel="nofollow noreferrer">https://docs.mongodb.com/manual/tutorial/perform-two-phase-commits/</a>

blocks|key|2718162|text|从4.0版开始，MongoDB将添加对多文档事务的支持。因此，您将拥有MongoDB中具有ACID保证的文档模型的强大功能。MongoDB中的事务将类似于关系数据库中的事务。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2718163|详情请访问以下链接：https://www.mongodb.com/blog/post/multi-document-transactions-in-mongodb?jmp=community|offset|length|2718164|entityMap|0|LINK|mutability|MUTABLE|url|https://www.mongodb.com/blog/post/multi-document-transactions-in-mongodb?jmp=community^0|0|A|2E|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

Starting from version 4.0 MongoDB will add support for multi-document transactions. So you will have the power of the document model with ACID guarantees in MongoDB.
Transactions in MongoDB will be like transactions in relational databases.

For details visit this link: <a href="https://www.mongodb.com/blog/post/multi-document-transactions-in-mongodb?jmp=community" rel="nofollow noreferrer">https://www.mongodb.com/blog/post/multi-document-transactions-in-mongodb?jmp=community</a>

blocks|key|1980767|text|仅支持单文档事务。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1980768|您可以在以下位置查看：https://docs.mongodb.com/v3.2/tutorial/perform-two-phase-commits/|1980769|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.mongodb.com/v3.2/tutorial/perform-two-phase-commits/^0|3|5|0|B|1T|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@$9|T|A|U|1|V]]|E|$]]|$1|H|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

Only support Single Document Transaction.

You can see it at: <a href="https://docs.mongodb.com/v3.2/tutorial/perform-two-phase-commits/" rel="nofollow noreferrer">https://docs.mongodb.com/v3.2/tutorial/perform-two-phase-commits/</a>

I am new to MongoDB. I read that <code>MongoDB does not support multi-document transactions</code>here <a href="http://docs.mongodb.org/manual/faq/fundamentals/" rel="noreferrer">http://docs.mongodb.org/manual/faq/fundamentals/</a>.

If I want to save data in two collections(A and B) atomically, then i can't do that using MongoDB i.e. if save fails in case of B, still A will have the data. Isn't it a big disadvantage? 

Still, people are using MongoDB rather than RDBMS. Why?

Transaction support in MongoDB

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我是MongoDB的新手。我在这里读到了那个MongoDB does not support multi-document transactions。如果我想将数据原子地保存在两个集合(A和B)中，那么我不能使用MongoDB来实现这一点，也就是说，如果在B的情况下保存失败，A仍然可以保存数据。这不是一个很大的缺点吗？尽管如此，人们仍然在使用MongoDB而不是关系型数据库。为什么？

问MongoDB中的事务支持
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