带有C#的Mongo DB-添加文档而与事务无关 [英] Mongo DB with C# - document added regardless of transaction

问题描述

我正在尝试用我编写的一个简单示例测试Mongo DB中新支持的事务. 我正在将Mongo DB版本4.0.5与驱动程序版本2.8.1结合使用. 这只是一个没有分片/副本的主实例.

I'm trying to test the newly supported transactions in Mongo DB with a simple example I wrote. I'm using Mongo DB version 4.0.5 with driver version 2.8.1. It's only a primary instance with no shards/replicas.

我必须在以下代码中缺少一些基本知识. 我创建一个Mongo客户，会话&数据库，然后开始事务，添加文档并中止该事务.在此代码之后，我希望数据库中没有任何更改，但已添加了文档.调试时，我还可以使用Robo 3T(Mongo客户端GUI)在InsertOne()之后立即看到文档.

I must be missing something basic in the following code. I create a Mongo client, session & database, then start a transaction, add a document and abort the transaction. After this code, I expect nothing to change in the database, but the document is added. When debugging I can also see the document right after the InsertOne() by using Robo 3T (Mongo client GUI).

知道我想念什么吗?

        var client =  new MongoClient("mongodb://localhost:27017");
        var session = client.StartSession();
        var database = session.Client.GetDatabase("myDatabase", new MongoDatabaseSettings
        {
            GuidRepresentation = GuidRepresentation.Standard,
            ReadPreference = ReadPreference.Primary,
            WriteConcern = new WriteConcern(1, 
                new MongoDB.Driver.Optional<TimeSpan?>(TimeSpan.FromSeconds(30))),

        });

        var entities = database.GetCollection<MyEntity>("test");            

        session.StartTransaction();

        // After this line I can already see the document in the db collection using Mongo client GUI (Robo 3T), although I expect not to see it until committing
        entities.InsertOne(new MyEntity { Name =  "Entity" });

        // This does not have any effect
        session.AbortTransaction();

可以将MongoDB作为1节点副本集运行，尽管我不确定独立副本和1节点副本集有什么区别. 请参阅下面的我的帖子.

It's possible to run MongoDB as a 1-node replica set, although I'm not sure what's the difference between a standalone and a 1-node replica set. See my post below.

无论如何，要使用已启动的事务，插入代码必须将会话作为参数接收:

In any case, to use the started transaction the insertion code must receive the session as a parameter:

entities.InsertOne(session, new MyEntity { Name = "Entity" });

现在有了这两项更改，交易就可以了.

With these 2 change now the transaction works.

推荐答案

这本质上是MongoDB本身的属性. (更多此处和

This is inherently a property of MongoDB itself. (More here and here)

交易仅在副本集设置中可用

Transactions are only available in a replica set setup

为什么它不能用于独立实例?

借助子文档和数组，文档数据库(MongoDB)允许相关数据在单个数据结构内按层次结构进行统一.可以使用原子操作来更新文档，从而为文档提供与关系数据库中的多表事务相同的数据完整性保证.

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