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Mongodb 使用$addFields时，如何将值合并到单个数组中？

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Mongodb 使用$addFields时，如何将值合并到单个数组中？,mongodb,mongoose,Mongodb,Mongoose,我是MongoDB的新手，基本上来自RDBMS。我使用$addFields从联接表中检索单个列，如下所示 { "_id" : ObjectId("5cd720dda185d600170278fd"), "action" : [ "5cf35c027807f0f65b5e9627" ], "events" : [ { "_id" : ObjectId("5cfa8b20ee38ea10717b3e72"),

我是MongoDB的新手，基本上来自RDBMS。我使用$addFields从联接表中检索单个列，如下所示

{
    "_id" : ObjectId("5cd720dda185d600170278fd"),
    "action" : [ 
        "5cf35c027807f0f65b5e9627"
    ],
    "events" : [ 
        {
            "_id" : ObjectId("5cfa8b20ee38ea10717b3e72"),
            "movieId" : ObjectId("5cd720dda185d600170278fd"),
            "sourceId" : ObjectId("5cfa0bb8f5b21607b245eff3"),
            "type" : "news",
            "description" : "Kathua rape, murder case verdict LIVE updates: Victim's family likely to challenge verdict giving life term to three main accused",
            "resources" :{
                "posterLinks" : [ 
                    {
                        "_v" : 1560167750,
                        "image" : "xxxx/posters/orgomohvopr0ykxgmq2g"
                    }, 
                    {
                        "_v" : 1560167752,
                        "image" : "xxxx/posters/bnskv36qbdj9wnaomvre"
                    }
                ],
                "youtubeLinks" : [ 
                    "https://www.youtube.com/watch?v=ocnzgwjXdLw", 
                    "https://www.youtube.com/watch?v=oLRHNYQ-Dno"
                ]
            },
            "createdDate" : ISODate("2019-06-07T16:04:48.980Z")
        }, 
        {
            "_id" : ObjectId("5cfa8d03e8604410c74a65ab"),
            "movieId" : ObjectId("5cd720dda185d600170278fd"),
            "sourceId" : ObjectId("5cfa0bb8f5b21607b245eff3"),
            "type" : "news",
            "description" : "Former Pakistani president Asif Ali Zardari arrested on corruption charges",
            "resources" : {
                "posterLinks" : [ 
                    {
                        "_v" : 1560167915,
                        "image" : "xxxx/posters/ldu3iceqarnaaw1qeyhk"
                    }, 
                    {
                        "_v" : 1560167917,
                        "image" : "xxxx/posters/r1oi172lpxdylnqaify5"
                    }
                ]
            },
            "createdDate" : ISODate("2019-06-07T16:12:51.927Z")
        }, 
    "resources" : [ 
        {
            "posterLinks" : [ 
                {
                    "_v" : 1560167750,
                    "image" : "xxxx/posters/orgomohvopr0ykxgmq2g"
                }, 
                {
                    "_v" : 1560167752,
                    "image" : "xxxx/posters/bnskv36qbdj9wnaomvre"
                }
            ],
            "youtubeLinks" : [ 
                "https://www.youtube.com/watch?v=ocnzgwjXdLw", 
                "https://www.youtube.com/watch?v=oLRHNYQ-Dno"
            ]
        }, 
        {
            "posterLinks" : [ 
                {
                    "_v" : 1560167915,
                    "image" : "xxxx/posters/ldu3iceqarnaaw1qeyhk"
                }, 
                {
                    "_v" : 1560167917,
                    "image" : "xxxx/posters/r1oi172lpxdylnqaify5"
                }
            ]
        }
    ]
}

电影
收藏结构：

{
    "_id" : ObjectId("5cd30088ccbfc800173dcd42"),
    "name" : "NGK",
    "sourceId" : "5cd3007cccbfc800173dcd41"
}

{
    "_id" : ObjectId("5cfa8b20ee38ea10717b3e72"),
    "movieId" : ObjectId("5cd720dda185d600170278fd"),
    "type" : "news",
    "description" : "Kathua rape, murder case verdict LIVE updates: Victim's family likely to challenge verdict giving life term to three main accused",
    "resources" :{
        "posterLinks" : [ 
            {
                "_v" : 1560167750,
                "image" : "xxxx/posters/orgomohvopr0ykxgmq2g"
            }, 
            {
                "_v" : 1560167752,
                "image" : "xxxx/posters/bnskv36qbdj9wnaomvre"
            }
        ],
        "youtubeLinks" : [ 
            "https://www.youtube.com/watch?v=ocnzgwjXdLw", 
            "https://www.youtube.com/watch?v=oLRHNYQ-Dno"
        ]
    },
    "createdDate" : ISODate("2019-06-07T16:04:48.980Z")
}, 
{
    "_id" : ObjectId("5cfa8d03e8604410c74a65ab"),
    "movieId" : ObjectId("5cd720dda185d600170278fd"),
    "sourceId" : ObjectId("5cfa0bb8f5b21607b245eff3"),
    "type" : "news",
    "description" : "Former Pakistani president Asif Ali Zardari arrested on corruption charges",
    "resources" : {
        "posterLinks" : [ 
            {
                "_v" : 1560167915,
                "image" : "xxxx/posters/ldu3iceqarnaaw1qeyhk"
            }, 
            {
                "_v" : 1560167917,
                "image" : "xxxx/posters/r1oi172lpxdylnqaify5"
            }
        ]
    },
    "createdDate" : ISODate("2019-06-07T16:12:51.927Z")
}

事件
集合结构：

{
    "_id" : ObjectId("5cd30088ccbfc800173dcd42"),
    "name" : "NGK",
    "sourceId" : "5cd3007cccbfc800173dcd41"
}

{
    "_id" : ObjectId("5cfa8b20ee38ea10717b3e72"),
    "movieId" : ObjectId("5cd720dda185d600170278fd"),
    "type" : "news",
    "description" : "Kathua rape, murder case verdict LIVE updates: Victim's family likely to challenge verdict giving life term to three main accused",
    "resources" :{
        "posterLinks" : [ 
            {
                "_v" : 1560167750,
                "image" : "xxxx/posters/orgomohvopr0ykxgmq2g"
            }, 
            {
                "_v" : 1560167752,
                "image" : "xxxx/posters/bnskv36qbdj9wnaomvre"
            }
        ],
        "youtubeLinks" : [ 
            "https://www.youtube.com/watch?v=ocnzgwjXdLw", 
            "https://www.youtube.com/watch?v=oLRHNYQ-Dno"
        ]
    },
    "createdDate" : ISODate("2019-06-07T16:04:48.980Z")
}, 
{
    "_id" : ObjectId("5cfa8d03e8604410c74a65ab"),
    "movieId" : ObjectId("5cd720dda185d600170278fd"),
    "sourceId" : ObjectId("5cfa0bb8f5b21607b245eff3"),
    "type" : "news",
    "description" : "Former Pakistani president Asif Ali Zardari arrested on corruption charges",
    "resources" : {
        "posterLinks" : [ 
            {
                "_v" : 1560167915,
                "image" : "xxxx/posters/ldu3iceqarnaaw1qeyhk"
            }, 
            {
                "_v" : 1560167917,
                "image" : "xxxx/posters/r1oi172lpxdylnqaify5"
            }
        ]
    },
    "createdDate" : ISODate("2019-06-07T16:12:51.927Z")
}
我的问题是：

db.getCollection('movies').aggregate([
   {
        $lookup: {
            from: "events",
            localField: "_id",
            foreignField: "movieId",
            as: "events"
        }
   },
   { 
       $addFields: { 
           "resources": "$events.resources"
        }
   }
]);
结果如下:

{
    "_id" : ObjectId("5cd720dda185d600170278fd"),
    "action" : [ 
        "5cf35c027807f0f65b5e9627"
    ],
    "events" : [ 
        {
            "_id" : ObjectId("5cfa8b20ee38ea10717b3e72"),
            "movieId" : ObjectId("5cd720dda185d600170278fd"),
            "sourceId" : ObjectId("5cfa0bb8f5b21607b245eff3"),
            "type" : "news",
            "description" : "Kathua rape, murder case verdict LIVE updates: Victim's family likely to challenge verdict giving life term to three main accused",
            "resources" :{
                "posterLinks" : [ 
                    {
                        "_v" : 1560167750,
                        "image" : "xxxx/posters/orgomohvopr0ykxgmq2g"
                    }, 
                    {
                        "_v" : 1560167752,
                        "image" : "xxxx/posters/bnskv36qbdj9wnaomvre"
                    }
                ],
                "youtubeLinks" : [ 
                    "https://www.youtube.com/watch?v=ocnzgwjXdLw", 
                    "https://www.youtube.com/watch?v=oLRHNYQ-Dno"
                ]
            },
            "createdDate" : ISODate("2019-06-07T16:04:48.980Z")
        }, 
        {
            "_id" : ObjectId("5cfa8d03e8604410c74a65ab"),
            "movieId" : ObjectId("5cd720dda185d600170278fd"),
            "sourceId" : ObjectId("5cfa0bb8f5b21607b245eff3"),
            "type" : "news",
            "description" : "Former Pakistani president Asif Ali Zardari arrested on corruption charges",
            "resources" : {
                "posterLinks" : [ 
                    {
                        "_v" : 1560167915,
                        "image" : "xxxx/posters/ldu3iceqarnaaw1qeyhk"
                    }, 
                    {
                        "_v" : 1560167917,
                        "image" : "xxxx/posters/r1oi172lpxdylnqaify5"
                    }
                ]
            },
            "createdDate" : ISODate("2019-06-07T16:12:51.927Z")
        }, 
    "resources" : [ 
        {
            "posterLinks" : [ 
                {
                    "_v" : 1560167750,
                    "image" : "xxxx/posters/orgomohvopr0ykxgmq2g"
                }, 
                {
                    "_v" : 1560167752,
                    "image" : "xxxx/posters/bnskv36qbdj9wnaomvre"
                }
            ],
            "youtubeLinks" : [ 
                "https://www.youtube.com/watch?v=ocnzgwjXdLw", 
                "https://www.youtube.com/watch?v=oLRHNYQ-Dno"
            ]
        }, 
        {
            "posterLinks" : [ 
                {
                    "_v" : 1560167915,
                    "image" : "xxxx/posters/ldu3iceqarnaaw1qeyhk"
                }, 
                {
                    "_v" : 1560167917,
                    "image" : "xxxx/posters/r1oi172lpxdylnqaify5"
                }
            ]
        }
    ]
}
我得到了预期的结果，但正如您所看到的，当一部电影有多个事件时，当一部电影有多个事件时，资源中有多个数组

我正在寻找一种方法，通过单个
posterLinks
和
youtubeLinks
对象为每部电影获取单个资源数组，我知道这可以通过在检索值后使用循环来实现。但在查询本身中是否有这样做的方法

此外，我不需要在结果中再次使用事件数组，因为所需的资源已在结果中可用。如果您对此有任何建议，我们将不胜感激。

对于您可以使用的任意资源

大概是这样的：

db.getCollection('movies').aggregate([
    {
       $lookup:
         {
            from: "events",
            let: { movieId: "$_id" },
            pipeline: [ 
                { $match: { $expr: { $eq: ["$movieId", "$$movieId"] } } },
                { $project: { resources: { $objectToArray: "$resources" } } },
                { $unwind: "$resources" },
                { $unwind: "$resources.v" },
                { $group: { _id:"$resources.k", "v": { $addToSet:"$resources.v" } } },
                { $group: { _id:null, resources: { $push: { k:"$_id", v:"$v" } } } },
                { $project: { resources: { $arrayToObject: "$resources" } } },
                { $replaceRoot: { newRoot:"$resources" } }
            ],
            as: "events"
         }
    },
    { $project: { resources:0 } },
    { $unwind: "$events" }
]);
查找中的管道按键对资源进行分组。 它允许在生成的数组中使用重复的资源。如果不打算这样做，则应相应修改子查询管道

记住这是一个相当昂贵的查询。如果资源的结构是预定义的且稳定的，您可以通过在主管道中使用带有硬编码键的数组函数来提高查询效率。

您能否显示预期的输出。资源是否始终仅限于PosterLink和YouTubeLink？嗨，Alex，非常感谢您的回复。它适用于大多数情况，但当文档中没有
引用
数组时，它不会将其包含在结果中。@陌生人对不起，我不明白，
引用
数组是什么？你确定你的评论是对的吗？对不起，这不是引用，这是资源。我的意思是，当有一个包含关键引用的文档时，它不会被提取，只提取存在“资源”的文档。亲爱的陌生人，你从未提过文档可能有“引用”在这种情况下，字段也不是您期望的结果。你对SO并不陌生，并且知道它是如何工作的。我们所掌握的唯一信息是你在问题中发布的内容。此外，答案说明了方法-调整管道以满足您的特殊需求。