如何在MongoDB中将数组转换为对象 [英] how to convert array to object in MongoDB

问题描述

我有一个对象数组，其中包含未知数量的数组元素:

 { "内容": [{"_id": "参考书",总计":189，已发表":189，创建":0，批准":0，拒绝":0，sent_for_approval":0},{"_id": "网络链接",总计":1911，发表":1899，创建":10，批准":2，拒绝":0，sent_for_approval":0},.................]}

我想将其转换为给定的对象:

 {内容":{{"_id": "参考书",总计":189，已发表":189，创建":0，批准":0，拒绝":0，sent_for_approval":0},{"_id": "网络链接",总计":1911，发表":1899，创建":10，批准":2，拒绝":0，sent_for_approval":0},.................}}

我尝试使用 $unwind，但没有得到所需的输出.如何在 MongoDB 中实现这个内部聚合管道?

我使用的是 Mongo 3.4 版.

解决方案

我找到了解决方案.

<预><代码>{$项目:{内容": {$arrayToObject":{$地图":{输入":$内容"，"as": "el",在": {"k": "$$el._id","v": "$$el"}}}}}

I have an array of object as given with unknown number of array elements:

               { "content": [
                    {
                        "_id": "refbooks",
                        "total": 189,
                        "published": 189,
                        "created": 0,
                        "approved": 0,
                        "rejected": 0,
                        "sent_for_approval": 0
                    },
                    {
                        "_id": "weblinks",
                        "total": 1911,
                        "published": 1899,
                        "created": 10,
                        "approved": 2,
                        "rejected": 0,
                        "sent_for_approval": 0
                    },.................]}

I want to convert it to an object like given:

                    { "content": {
                    {
                        "_id": "refbooks",
                        "total": 189,
                        "published": 189,
                        "created": 0,
                        "approved": 0,
                        "rejected": 0,
                        "sent_for_approval": 0
                    },
                    {
                        "_id": "weblinks",
                        "total": 1911,
                        "published": 1899,
                        "created": 10,
                        "approved": 2,
                        "rejected": 0,
                        "sent_for_approval": 0
                    },.................}}

I tried using $unwind, but I did't get my required output. How to implement this inside aggregation pipeline in MongoDB?

I'm using Mongo version 3.4.

解决方案

I found the solution.

{
            $project: {
                "content": {
                    "$arrayToObject": {
                        "$map": {
                            "input": "$content",
                            "as": "el",
                            "in": {
                                "k": "$$el._id",
                                "v": "$$el"
                            }
                        }
                    }
                }
}

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