如何在golang mgo.v2库中使用MongoDB获得汇总管道结果

Question

Question background is I want retrieve aggregated data from MongoDB data by using golang mgo.v2 liabary.

I have a collection dataset as following.collection name is useragents

{
    "_id" : ObjectId("57f940c4932a00aba387b0b0"),
    "tenantID" : 1,
    "date" : "2016-10-09 00:23:56",
    "venueList" : [
        {
            "id" : “VID1212”,
            "sum" : [
                {
                      "name" : "linux",
                      "value" : 12
                },
                {
                    "name" : "ubuntu",
                    "value" : 4
                }
            ],
            “ssidList” : [    // this is list of ssid’s in venue
                {
                    "id" : “SSID1212”,
                    "sum" : [
                        {
                            "name" : "linux",
                            "value" : 8
                        },
                        {
                            "name" : "ubuntu",
                            "value" : 6
                        }
                    ],
                    “macList” : [  // this is mac list inside particular ssid  ex: this is mac list inside the SSID1212
                        {
                            "id" : “12:12:12:12:12:12”,
                            "sum" : [
                                {
                                    "name" : "linux",
                                    "value" : 12
                                },
                                {
                                    "name" : "ubuntu",
                                    "value" : 1
                                }
                            ]
                        }
                    ]
                }
            ]
        },
        {
            "id" : “VID4343”,
            "sum" : [
                {
                     "name" : "linux",
                     "value" : 2
                }
            ],
            "ssidList" : [
                {
                    "id" : “SSID4343”,
                    "sum" : [
                        {
                            "name" : "linux",
                            "value" : 2
                        }
                    ],
                    "macList" : [
                        {
                            "id" : “43:43:43:43:43:34”,
                            "sum" : [
                                {
                                    "name" : "linux",
                                    "value" : 2
                                }
                            ]
                        }
                    ]
                }
            ]
        }
    ]
}

I have already solved MongoDB shell script that i want by help from stack-overflow community.but I am troubling on when I was implemening it in golang using mgo.v2 library.

This is mongodb shell script

db.useragents.aggregate([
    { "$match": { "venueList.id": { "$in": ["VID1212", "VID4343"] } } },
    { "$unwind": "$venueList" },
    { "$match": { "venueList.id": { "$in": ["VID1212", "VID4343"] } } },
    { "$unwind": "$venueList.sum" },    
    { 
        "$group": {
            "_id": "$venueList.sum.name",
            "count": { "$sum": "$venueList.sum.value" }
        }
    },
    { 
        "$group": {
            "_id": null,
            "counts": {
                "$push": {
                    "name": "$_id",
                    "value": "$count"
                }
            }
        }
    }
])

Please go though question background

And I implement golang code as following

func GetBrowserStats(constrains models.Constrains) ([]bson.M, error) {

    session := commons.GetMongoSession()
    defer session.Close()
    var col = session.DB("analytics").C("useragents")

    pipeline1 := bson.M{
        "$match": bson.M{
            "venueList.id": bson.M{
                "$in": []string{"VID1212", "VID4343"},
            },
        },
    }
    pipeline2 := bson.M{
        "$unwind": "$venueList",
    }
    pipeline3 := bson.M{
        "$match": bson.M{
            "venueList.id": bson.M{
                "$in": []string{"VID1212", "VID4343"},
            },
        },
    }
    pipeline4 := bson.M{
        "$unwind": "$venueList.sum",
    }

    pipeline5 := bson.M{
        "$group": bson.M{
            "_id": "$venueList.sum.name",
            "count": bson.M{
                "$sum": "$venueList.sum.value",
            },
        },
    }
    pipeline6 := bson.M{
        "$group": bson.M{
            "_id": bson.NewObjectId(),
            "counts": bson.M{
                "$push": bson.M{
                    "name":  "$_id",
                    "value": "$count",
                },
            },
        },
    }

    all := []bson.M{pipeline1, pipeline2, pipeline3, pipeline4, pipeline5, pipeline6}
    pipe := col.Pipe(all)

    result := []bson.M{}
    err := pipe.All(&result)
    println(result[0])
    if err != nil {
        println(err.Error())
        errMsg := "Error occourred while getting dashboard configs from mongo stack:" + err.Error()
        log.Error()
        return result, errors.New(errMsg)
    }
    return result, nil
}

I have create a pipline and serve it into pipe.All() but there is null result return from the result varible.

I want to return following object in result

{ "_id" : ObjectId("57f73573d6e0ac1a9f2ab346") , "counts" : [ { "name" : "ubuntu", "value" : 1 }, { "name" : "linux", "value" : 14 } ] }

Answer 1

Finally I find the solution.I like to share it with stackoverflow community.

I refer this one : google group answer

 session := commons.GetMongoSession()
    defer session.Close()

    pipeline := []bson.D{
        bson.D{
            {"$match",
                bson.M{
                    "venueList.id": bson.M{"$in": []string{"VID1212", "VID4343"}},
                },
            },
        },
        bson.D{
            {"$unwind", "$venueList"},
        },
        bson.D{
            {"$match",
                bson.M{
                    "venueList.id": bson.M{"$in": []string{"VID1212", "VID4343"}},
                },
            },
        },
        bson.D{
            {"$unwind", "$venueList.sum"},
        },
        bson.D{
            {"$group",

                bson.M{
                    "_id": "$venueList.sum.name",
                    "count": bson.M{
                        "$sum": "$venueList.sum.value",
                    },
                },
            },
        },
        bson.D{
            {"$group",
                bson.M{
                    "_id": bson.NewObjectId(),
                    "counts": bson.M{
                        "$push": bson.M{
                            "name":  "$_id",
                            "value": "$count",
                        },
                    },
                },
            },
        },
    }

    query := bson.D{
        {"aggregate", "useragents"}, // useragents is a collection name
        {"pipeline", pipeline},
    }

    var res interface{}
    err := session.DB("analytics").Run(query, &res)
    if err != nil {
        println(err.Error())
    } else {
        println(res)
    }