在特定条件下以嵌套级别收集不同的字段名称 [英] Collect distinct field names at nested level with specific condition

问题描述

我有一个问题陈述，其中我需要"config.first.second"子级别的所有字段名称，其中include字段至少为true. 这是我的mongo收集对象.

I have problem statement, in which i need all the field names at child level of "config.first.second" where include field is true at least once. Here is my mongo collection objects.

   [ {
        "_id" : ObjectId("560e97f4a78eb445cd2d75e5"),
        "config" : {
            "first" : {
                "second" : {
                    "field1" : {
                       "include":"true"
                    },
                    "field3" : {
                      "include":"true"
                    },
                    "field9" : {
                        "include":"false"
                    },
                    "field6" : {
                        "include":"false"
                    }
                }
            }
        },
        "date_created" : "Fri Oct 02 14:43:00 UTC 2015",
        "last_updated" : "Mon Apr 11 15:26:37 UTC 2016",
        "id" : ObjectId("560e97f4a78eb445cd2d75e5")
    },
    {
        "_id" : ObjectId("56154465a78e41c04692af20"),
        "config" : {
            "first" : {
                "second" : {
                    "field1" : {
                        "include":"true"
                    },
                    "field3" : {
                        "include":"false"
                    },
                    "field7" : {
                    "include":"true"
                    }
                }
            }
        },
        "date_created" : "Wed Oct 07 16:12:21 UTC 2015",
        "last_updated" : "Mon Apr 11 15:18:58 UTC 2016",
        "id" : ObjectId("56154465a78e41c04692af20")
    }
]

使用以上mongo集合.查询必须返回结果

Using above mongo collection . Query must return result

["field1","field3","field7"]

推荐答案

您可以使用mapReduce运行:

You can run with mapReduce:

db.collection.mapReduce(
  function() {
    Object.keys(this.config.first.second)
      .filter( k => this.config.first.second[k].include === "true" )
      .forEach(k => emit(k,1) );
  },
  function() { },
  { 
    "out": { "inline": 1 },

  }
)['results'].map( d => d._id )

如果您拥有MongoDB 3.4，则可以使用.aggregate():

If you have MongoDB 3.4 then you can use .aggregate():

db.collection.aggregate([
  { "$project": {
    "field": {
      "$filter": {
        "input": { "$objectToArray": "$config.first.second" },
        "as": "f",
        "cond": { "$eq": [ "$$f.v.include", "true" ] }
      }
    }
  }},
  { "$unwind": "$field" },
  { "$group": { "_id": "$field.k" } }
]).toArray().map(d => d._id)

返回:

[
    "field1",
    "field3",
    "field7"
]

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