c# - Mongo DB中的Upserting和Id问题

Question

我在使用官方 C# 驱动程序升级到 mongo db 时遇到问题。

public abstract class AggregateRoot
{
    /// <summary>
    /// All mongoDb documents must have an id, we specify it here
    /// </summary>
    protected AggregateRoot()
    {
        Id = ObjectId.GenerateNewId();
    }

    [BsonId]
    public ObjectId Id { get; set; }
}

我的实体已经有 id-s，但我必须创建 mongo 特定的 Id 才能工作，因为集合中的所有文档都应该有一个。现在我在我的系统中收到一个新实体，生成了一个新的 Mongo Id，我得到 mongo cannot change _id of a document old 异常。有什么解决办法吗？

Let me describe the design a bit. All the entities which would be stored as documents were inheriting from AggregateRoot which had the id generation in it. Every sub-document had its id generated automatically and I had no problem with this. The id in AggregateRoot was introduced to correct the problem when retrieving data from MongoCollection to List and the generation was introduced so the id-s are different. Now we can move that id generation to save methods because the new entity for update had a new id generation. But it would mean that every dev on the team must not forget generating id-s in repository which is risky. It would be nicer just to ignore the id than mapping from mongo if it is possible and not to have AggregateRoot class at all

Answer 1

我也遇到过类似的问题。 我想使用官方 C# 驱动程序更新文档。我有这样的课:

public class MyClass
{
    public ObjectId Id { get; set; }
    public int Field1 { get; set; }
    public string Field2 { get; set; }
}

在控制台中我会写: db.collection.update({Field1: 3},{Field1: 3, Field2: "value"}) 它会起作用。我在 C# 中写道:

collection.Update(Query.EQ("Field1", 3),
                Update.Replace(new MyClass { Field1 = 3, Field2 = "value" }),
                UpdateFlags.Upsert);

它没有用!因为驱动程序在更新语句中包含空 id，并且当我插入第二个具有不同值的文档时 Field1 异常 E11000 duplicate key error index 被抛出(在这种情况下，Mongo 尝试插入一个 _id 已经存在的文档分贝)。

当我自己生成 _id(如主题启动器)时，我在更新插入现有值为 Field1 的对象时遇到了相同的异常(mongo 无法更改文档的 _id)。

解决方案是通过[BsonIgnoreIfDefault]属性标记Id属性(不初始化)。在这种情况下，驱动程序会在更新语句中省略 _id 字段，MongoDb 会在必要时生成 Id。