嵌入式阵列更新后如何取回新值? [英] How to get back the new value after an update in a embedded array?

问题描述

给出以下MongoDB集合:

Given the following MongoDB collection:

{
    "_id": ObjectId("56d6a7292c06e85687f44541"),
    "name": "My ranking list",
    "rankings": [
        {
            "_id": ObjectId("46d6a7292c06e85687f55542"),
            "name": "Ranking 1",
            "score": 1
        },
        {
            "_id": ObjectId("46d6a7292c06e85687f55543"),
            "name": "Ranking 2",
            "score": 10
        },
        {
            "_id": ObjectId("46d6a7292c06e85687f55544"),
            "name": "Ranking 3",
            "score": 15
        },
    ]
}

这是我如何提高给定排名的分数:

Here is how I increase the score of a given ranking:

db.collection.update(
    { "_id": ObjectId("56d6a7292c06e85687f44541"), "rankings._id" : ObjectId("46d6a7292c06e85687f55543") },
    { $inc : { "rankings.$.score" : 1 } }
);

如何获取新的分数值?在上一个查询中，我将第二个排名从10增加到11 ...更新后如何重新获得这个新值?

How do I get the new score value? In the previous query I increase the second ranking from 10 to 11... How do I get this new value back after the update?

推荐答案

如果您使用的是MongoDB 3.0或更高版本，则需要使用 $elemMatch 投影运算符，因为您不能使用位置投影并返回新文档.

If you are on MongoDB 3.0 or newer, you need to use the .findOneAndUpdate() and use projection option to specify the subset of fields to return. You also need to set returnNewDocument to true. Of course you need to use the $elemMatch projection operator here because you cannot use a positional projection and return the new document.

有人指出:

您应该使用 .findOneAndUpdate() 是因为 .findAndModify() 已被高列为每种正式语言均已弃用司机.另一件事是，语法和选项在.findOneAndUpdate()的驱动程序之间非常一致.使用.findAndModify()，大多数驱动程序不会通过查询/更新/字段"键使用相同的单个对象.因此，当有人申请另一种语言以保持一致时，它会减少一些混乱. .findOneAndUpdate()的标准化API更改实际上对应于服务器版本3.x，而不是3.2.x.完全的区别是shell方法在实现该方法时实际上落后于其他驱动程序(一次！).因此，大多数驱动程序实际上都具有与3.x版本相对应的主要发行版变更.

You should be using .findOneAndUpdate() because .findAndModify() is highlighed as deprecated in every official language driver. The other thing is that the syntax and options are pretty consistent across drivers for .findOneAndUpdate(). With .findAndModify(), most drivers don't use the same single object with "query/update/fields" keys. So it's a bit less confusing when someone applies to another language to be consistent. Standardized API changes for .findOneAndUpdate() actually correspond to server release 3.x rather than 3.2.x. The full distinction being that the shell methods actually lagged behind the other drivers ( for once ! ) in implementing the method. So most drivers actually had a major release bump corresponding with the 3.x release with such changes.

db.collection.findOneAndUpdate( 
    { 
        "_id": ObjectId("56d6a7292c06e85687f44541"), 
         "rankings._id" : ObjectId("46d6a7292c06e85687f55543") 
    },  
    { $inc : { "rankings.$.score" : 1 } },  
    { 
        "projection": { 
            "rankings": { 
                "$elemMatch": { "_id" : ObjectId("46d6a7292c06e85687f55543") } 
            }
        }, 
        "returnNewDocument": true 
    }
)

从MongoDB 3.0开始，您需要使用 findAndModify 和fields选项，还需要将new设置为true，以返回新值.

From MongoDB 3.0 onwards, you need to use findAndModify and the fields options also you need to set new to true in other to return the new value.

db.collection.findAndModify({   
    query: { 
        "_id": ObjectId("56d6a7292c06e85687f44541"), 
        "rankings._id" : ObjectId("46d6a7292c06e85687f55543") 
    },     
    update: { $inc : { "rankings.$.score" : 1 } },       
    new: true,  
    fields: { 
        "rankings": { 
            "$elemMatch": { "_id" : ObjectId("46d6a7292c06e85687f55543") }
        }  
    }
})

两个查询都产生:

{
        "_id" : ObjectId("56d6a7292c06e85687f44541"),
        "rankings" : [
                {
                        "_id" : ObjectId("46d6a7292c06e85687f55543"),
                        "name" : "Ranking 2",
                        "score" : 11
                }
        ]
}

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