查询没有数组的嵌套字段

Posted 2023-03-16

【中文标题】查询没有数组的嵌套字段

【英文标题】：Querying nested fields with no arrays

【发布时间】：2019-01-05 21:54:29

【问题描述】：

对于以下文档“27”，“28”是当月的天数，而“27”下的“6”到“11”代表小时，我希望能够仅检索每个用户数组小时使用 python 进行一些处理，或者理想情况下捕获一整天的用户数组，但如果我可以每小时访问用户，我可以使用 python 做到这一点。

        "values" : 
                "27" : 
                        "6" : 
                                "users" : [
                                        "5b5abc5ddd601f0b6681358a"
                                ],
                                "values" : 
                                        "5b5abc5ddd601f0b6681358a" : 2
                                
                        ,
                        "7" : 
                                "users" : [
                                        "5b5ac75cdd601f0b668157ff",
                                        "5b5acd0ddd601f0b66816803"
                                ],
                                "values" : 
                                        "5b5ac75cdd601f0b668157ff" : 1,
                                        "5b5acd0ddd601f0b66816803" : 4
                                
                        ,
                        "8" : 
                                "users" : [
                                        "5b5acd0ddd601f0b66816803"
                                ],
                                "values" : 
                                        "5b5acd0ddd601f0b66816803" : 2
                                
                        ,
                        "9" : 
                                "users" : [
                                        "5b5acd0ddd601f0b66816803",
                                        "5b5ae89b781e011702f00812"
                                ],
                                "values" : 
                                        "5b5acd0ddd601f0b66816803" : 2,
                                        "5b5ae89b781e011702f00812" : 3
                                
                        ,
                        "10" : 
                                "users" : [
                                        "5b5ae89b781e011702f00812"
                                ],
                                "values" : 
                                        "5b5ae89b781e011702f00812" : 1
                                
                        
                ,
                "28" : 
                        "11" : 
                                "users" : [
                                        "5b5abacadd601f0b6681312e"
                                ],
                                "values" : 
                                        "5b5abacadd601f0b6681312e" : 1
                                
                        
                
        

问题是因为这里没有数组，所以展开不起作用，还有几天和几个小时没有活动，所以没有可用的数据。

【问题讨论】：

这个模型的预期输出是什么？

我的意思是你想如何使用 MongoDB 转换粘贴的文档

我想把它为天：[用户] “27”：[ “5b5abc5ddd601f0b6681358a”， “5b5ac75cdd601f0b668157ff”， “5b5acd0ddd601f0b66816803”， “5b5acd0ddd601f0b66816803”， “5b5acd0ddd601f0b66816803”， “5b5ae89b781e011702f00812” ,"5b5ae89b781e011702f00812"]

"28": ["5b5abacadd601f0b6681312e"]

【参考方案1】：

您需要$objectToArray 才能使用动态键名。然后您可以应用$map 结合$reduce 来展平您的数据模型，并应用$arrayToObject 来获得以天为键的结果：

db.col.aggregate([
    
        $project: 
            days: 
                $map: 
                    input:  $objectToArray: "$values" ,
                    as: "day",
                    in: 
                        k: "$$day.k",
                        v: 
                            $map:  
                                input:  $objectToArray: "$$day.v" ,
                                as: "h",
                                in: 
                                    $map: 
                                        input:  $objectToArray: "$$h.v.values" ,
                                        as: "pair",
                                        in: "$$pair.k"
                                    
                                
                            
                        
                    
                
            
        
    ,
    
        $project: 
            days: 
                $arrayToObject: 
                    $map: 
                        input: "$days",
                        as: "day",
                        in: 
                            k: "$$day.k",
                            v: 
                                $reduce: 
                                    input: "$$day.v",
                                    initialValue: [],
                                    in:  $concatArrays: [ "$$this", "$$value" ] 
                                
                            
                        
                    
                
            
        
    
])

打印：

    "days" : 
            "27" : [
                    "5b5ae89b781e011702f00812",
                    "5b5acd0ddd601f0b66816803",
                    "5b5ae89b781e011702f00812",
                    "5b5acd0ddd601f0b66816803",
                    "5b5ac75cdd601f0b668157ff",
                    "5b5acd0ddd601f0b66816803",
                    "5b5abc5ddd601f0b6681358a"
            ],
            "28" : [
                    "5b5abacadd601f0b6681312e"
            ]
    

【讨论】：

您先生，真是个天才！谢谢。