Mongo聚合嵌套数组 [英] Mongo aggregate nested array

问题描述

我有一个具有以下结构的mongo集合

I have a mongo collection with following structure

{
    "userId" : ObjectId("XXX"),
    "itemId" : ObjectId("YYY"),
    "resourceId" : 1,
    "_id" : ObjectId("528455229486ca3606004ec9"),
    "parameter" : [
        {
            "name" : "name1",
            "value" : 150,
            "_id" : ObjectId("528455359486ca3606004eed")
        },
        {
            "name" : "name2",
            "value" : 0,
            "_id" : ObjectId("528455359486ca3606004eec")
        },
        {
            "name" : "name3",
            "value" : 2,
            "_id" : ObjectId("528455359486ca3606004eeb")
        }
    ]
}

可以有多个文档，这些文档具有相同的"useId"和不同的"itemId"，但参数在所有文档中都具有相同的键/值对.

There can be multiple documents with the same 'useId' with different 'itemId' but the parameter will have same key/value pairs in all of them.

我要完成的工作是为每个唯一的"userId"返回聚合参数"name1"，"name2"和"name3"，而无需考虑"itemId".因此最终结果看起来像每个用户:

What I am trying to accomplish is return aggregated parameters "name1", "name2" and "name3" for each unique "userId" disregard the 'itemId'. so final results would look like for each user :

{
  "userId" : ObjectId("use1ID"),
  "name1" : (aggregatedValue),
  "name2" : (aggregatedValue),
  "name3" : (aggregatedVAlue) 
},
{
  "userId" : ObjectId("use2ID"),
  "name1" : (aggregatedValue),
  "name2" : (aggregatedValue),
  "name3" : (aggregatedVAlue) 
}

是否可以使用mongoDB的聚合方法来完成此操作?您能帮我建立适当的查询来完成此操作吗?

Is it possible to accomplish this using the aggregated methods of mongoDB ? Could you please help me to build the proper query to accomplish that ?

推荐答案

最简单的形式是使事物以参数"名称"为键:

The simplest form of this is to keep things keyed by the "parameter" "name":

db.collection.aggregate(
   // Unwind the array
   { "$unwind": "$parameter"},

   // Group on the "_id" and "name" and $sum "value"
   { "$group": {
       "_id": { 
           "userId": "$userId",
           "name": "$parameter.name"
       }, 
       "value": { "$sum": "$parameter.value" } 
   }},

   // Put things into an array for "nice" processing
   { "$group": {
       "_id": "$_id.userId",
       "values": { "$push": { 
           "name": "$_id.name",
           "value": "$value"
       }}
   }}
)

如果您真的需要名称的值"作为字段值，则可以执行以下操作.但是，由于要投影"字段/属性，因此必须在代码中全部指定.您再也无法保持动态"，并且每个人都编码/生成:

If you really need to have the "values" of names as the field values, you can do the the following. But since you are "projecting" the fields/properties then you must specify them all in your code. You cannot be "dynamic" anymore and you are coding/generating each one:

db.collection.aggregate([
    // Unwind the array
    { "$unwind": "$parameter"},

   // Group on the "_id" and "name" and $sum "value"
    { "$group": {
        "_id": {
             "userId": "$userId",
             "name": "$parameter.name"
        },
        "value": { "$sum": "$parameter.value"}
    }},

    // Project out discrete "field" names with $cond
    { "$project": {
        "name1": { "$cond": [
            { "$eq": [ "$_id.name", "name1" ] },
            "$value",
            0
        ]},
        "name2": { "$cond": [
            { "$eq": [ "$_id.name", "name2" ] },
            "$value",
            0
        ]},
        "name3": { "$cond": [
            { "$eq": [ "$_id.name", "name3" ] },
            "$value",
            0
        ]},
    }},

    // The $cond put "0" values in there. So clean up with $group and $sum
    { "$group": { 
        _id: "$_id.userId",
        "name1": { "$sum": "$name1" },
        "name2": { "$sum": "$name2" },
        "name3": { "$sum": "$name3" }
    }}

])

因此，尽管额外的步骤可以为您提供所需的结果(最后一个项目将_id更改为userId)，但在我看来，除非您确实需要，否则简短的版本就足够了.还要考虑那里的输出:

So while the extra steps give you the result that you want ( well with a final project to change the _id to userId ), for my mind the short version is workable enough, unless you really do need it. Consider the output from there as well:

{
    "_id" : ObjectId("53245016ea402b31d77b0372"),
    "values" : [
        {
            "name" : "name3",
            "value" : 2
        },
        {
            "name" : "name2",
            "value" : 0
        },
        {
            "name" : "name1",
            "value" : 150
        }
    ]
}

因此，这将是我个人使用的.但是您的选择.

So that would be what I would use, personally. But your choice.

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