Mongo $ sum is compounded when $ unwind is executed, and then $ group on multiple fields

Question

Mongo $ sum is compounded when $ unwind is executed, and then $ group on multiple fields

I have the following document structure

{
    "app_id": "DHJFK67JDSJjdasj909",
    "date": ISODate("2014-08-07T00:00:00.000Z"),
    "event_count": 100,
    "events": [
        { "type": 0,  "value": 12  },
        { "type": 10, "value": 24 },
        { "type": 20, "value": 36  },
        { "type": 30, "value": 43 }
    ],
    "unique_events": [
        { "type": 0,  "value": 5  },
        { "type": 10, "value": 8 },
        { "type": 20, "value": 12  },
        { "type": 30, "value": 56 }
    ]
}

I am trying to get the sum of event_counts, as well as the values for unique_events and events for each type. This is the result that I expect when the event_count value and each event and unique_events value were summed for each type.

{
    "app_id": "DHJFK67JDSJjdasj909",
    "date": ISODate("2014-08-07T00:00:00.000Z"),
    "event_count": 4345,
    "events": [
        { "type": 0,  "value": 624  },
        { "type": 10, "value": 234 },
        { "type": 20, "value": 353 },
        { "type": 30, "value": 472 }
    ],
    "unique_events": [
        { "type": 0,  "value": 433  },
        { "type": 10, "value": 554 },
        { "type": 20, "value": 645  },
        { "type": 30, "value": 732 }
    ]
}

This is my request.

db.events.aggregate([
    { "$unwind": "$events" },
    { "$group": {
        "_id": { 
            "app_id": "$app_id",
            "type": "$events.type"
            "unique_type": "$unique_events.type"
        },
        "event_count": { "$sum": "$event_count" },
        "event_value": { "$sum": "$events.value" },
        "unique_event_value": { "$sum": "$unique_events.value" }
    }},
    { "$group": {
        "_id": "$_id.app_id",
        "event_count": { "$sum": "$event_count" },
        "events": { "$push": { "type": "$_id.type", "value": "$event_value" } }
        "unique_events": { "$push": { "type": "$_id.unique_type", "value": "$unique_event_value" } }
    }}
])

The problem is that using two $ unwinds and then grouping by both events and unique_events results in $ sum being compounded and too large. Is there a way to fix this with mongo or do I need to run two queries and then combine the two result sets into code.

thank

Irfan

+4

mongodb mongodb-query aggregation-framework

Irfan Aug 08 '14 at 10:15

2

:
, variable events unique_events.
collection, out: "session_stat" mapReduce Function.

var mapFunction = function() {
                      var key = this.app_id;
                      var value = {                                 
                                    event_count: this.event_count,
                                    events: this.events,
                                    unique_events: this.unique_events
                                   };

                      emit( key, value );
                  };

var reduceFunction = function(key, values) {

                        var reducedObject = {
                                              app_id: key,
                                              events_wise_total: 0,
                                              unique_events_wise_total:0,
                                              total_event_count:0
                                            };

                        var events_wise_total = [];
                        var events_0_total = { type:0, value :0};
                        var events_10_total = { type:10, value :0};
                        var events_20_total = { type:20, value :0};
                        var events_30_total = { type:30, value :0};

                        var unique_events_wise_total = [];
                        var unique_events_0_total = { type:0, value :0};
                        var unique_events_10_total = { type:10, value :0};
                        var unique_events_20_total = { type:20, value :0};
                        var unique_events_30_total = { type:30, value :0};

                        var total_event_count = 0;
                        values.forEach( function(value) {
                                total_event_count += value.event_count;
                                var events = value.events;

                                events.forEach(function(event){
                                                if(event.type == 0){events_0_total.value += event.value;}
                                                if(event.type == 10){events_10_total.value += event.value;}
                                                if(event.type == 20){events_20_total.value += event.value;}
                                                if(event.type == 30){events_30_total.value += event.value;}
                                        });

                                var unique_events = value.unique_events;

                                unique_events.forEach(function(unique_event){
                                                if(unique_event.type == 0){unique_events_0_total.value += unique_event.value;}
                                                if(unique_event.type == 10){unique_events_10_total.value += unique_event.value;}
                                                if(unique_event.type == 20){unique_events_20_total.value += unique_event.value;}
                                                if(unique_event.type == 30){unique_events_30_total.value += unique_event.value;}
                                        }); 
                            }
                          );
                        events_wise_total.push(events_0_total);
                        events_wise_total.push(events_10_total);
                        events_wise_total.push(events_20_total);
                        events_wise_total.push(events_30_total);

                        unique_events_wise_total.push(unique_events_0_total);
                        unique_events_wise_total.push(unique_events_10_total);
                        unique_events_wise_total.push(unique_events_20_total);
                        unique_events_wise_total.push(unique_events_30_total);

                        reducedObject.events_wise_total = events_wise_total;
                        reducedObject.unique_events_wise_total = unique_events_wise_total;
                        reducedObject.total_event_count = total_event_count;

                        return reducedObject;
                     };

var finalizeFunction = function (key, reducedValue) {
                          return reducedValue;
                       };                    

db.GroupBy.mapReduce(
                       mapFunction,
                       reduceFunction,
                       {
                         out: "session_stat",
                         finalize: finalizeFunction
                       });

,

+2

Harsh Patel 12 . '14 7:54

Neil Lunn · Accepted Answer · 2014-08-08T15:06:48+0000

, , " ". , , , , () .

, MongoDB 2.6 :

db.events.aggregate([
    { "$project": {
        "app_id": 1,
        "event_count": 1,
        "all_events": {
            "$setUnion": [
                { "$map": {
                    "input": "$events",
                    "as": "el",
                    "in": {
                        "type": "$$el.type",
                        "value": "$$el.value",
                        "class": { "$literal": "A" }
                    }
                }},
                { "$map": {
                    "input": "$unique_events",
                    "as": "el",
                    "in": {
                        "type": "$$el.type",
                        "value": "$$el.value",
                        "class": { "$literal": "B" }
                    }
                }}
            ]
        }
    }},
    { "$unwind": "$all_events" },
    { "$group": {
        "_id": {
            "app_id": "$app_id",
            "class": "$all_events.class",
            "type": "$all_events.type"
        },
        "event_count": { "$sum": "$event_count" },
        "value": { "$sum": "$all_events.value" }
    }},
    { "$group": {
        "_id": "$_id.app_id",
        "event_count": { "$sum": "$event_count" },
        "events": {
            "$push": {
                "$cond": [
                    { "$eq": [ "$_id.class", "A" ] },
                    { "type": "$_id.type", "value": "$value" },
                    false
                ]
            }
        },
        "unique_events": {
            "$push": {
                "$cond": [
                    { "$eq": [ "$_id.class", "B" ] },
                    { "type": "$_id.type", "value": "$value" },
                    false
                ]
            }
        }
    }},
    { "$project": {
        "event_count": 1,
        "events": { "$setDifference": [ "$events", [false] ] },
        "unique_events": {
            "$setDifference": [ "$unique_events", [false] ]
        }
    }}
])

$setUnion $setDifference. $map, . $unwind. , , , :

db.events.aggregate([
    { "$unwind": "$events" },
    { "$group": {
        "_id": "$_id",
        "app_id": { "$first": "$app_id" },
        "event_count": { "$first": "$event_count" },
        "events": {
            "$push": {
                "type": "$events.type",
                "value": "$events.value",
                "class": { "$const": "A" }
            }
        },
        "unique_events": { "$first": "$unique_events" }            
    }},
    { "$unwind": "$unique_events" },
    { "$group": {
        "_id": "$_id",
        "app_id": { "$first": "$app_id" },
        "event_count": { "$first": "$event_count" },
        "events": { "$first": "$events" },
        "unique_events": {
            "$push": {
                "type": "$unique_events.type",
                "value": "$unique_events.value",
                "class": { "$const": "B" }
            }
        }
    }},
    { "$project": {
        "app_id": 1,
        "event_count": 1,
        "events": 1,
        "unique_events": 1,
        "type": { "$const": [ "A","B" ] }
    }},
    { "$unwind": "$type" },
    { "$unwind": "$events" },
    { "$unwind": "$unique_events" },
    { "$group": {
        "_id": "$_id",
        "app_id": { "$first": "$app_id" },
        "event_count": { "$first": "$event_count" },
        "all_events": {
            "$addToSet": {
                "$cond": [
                     { "$eq": [ "$events.class", "$type" ] },
                     {
                         "type": "$events.type",
                         "value": "$events.value",
                         "class": "$events.class"
                     },
                     {
                         "type": "$unique_events.type",
                         "value": "$unique_events.value",
                         "class": "$unique_events.class"
                     }
                ]
            }
        }
    }},
    { "$unwind": "$all_events" },
   { "$group": {
        "_id": {
            "app_id": "$app_id",
            "class": "$all_events.class",
            "type": "$all_events.type"
        },
        "event_count": { "$sum": "$event_count" },
        "value": { "$sum": "$all_events.value" }
    }},
    { "$group": {
        "_id": "$_id.app_id",
        "event_count": { "$sum": "$event_count" },
        "events": {
            "$push": {
                "$cond": [
                    { "$eq": [ "$_id.class", "A" ] },
                    { "type": "$_id.type", "value": "$value" },
                    false
                ]
            }
        },
        "unique_events": {
            "$push": {
                "$cond": [
                    { "$eq": [ "$_id.class", "B" ] },
                    { "type": "$_id.type", "value": "$value" },
                    false
                ]
            }
        }
    }},
    { "$unwind": "$events" },
    { "$match": { "events": { "$ne": false } } },
    { "$group": {
        "_id": "$_id",
        "event_count": { "$first": "$event_count" },
        "events": { "$push": "$events" },
        "unique_events": { "$first": "$unique_events" }
    }},
    { "$unwind": "$unique_events" },
    { "$match": { "unique_events": { "$ne": false } } },
    { "$group": {
       "_id": "$_id",
        "event_count": { "$first": "$event_count" },
        "events": { "$first": "$events" },
        "unique_events": { "$push": "$unique_events" }
    }}
])

, , , "event_count" .

, , , . - . , , , - .

Mongo $ sum is compounded when $ unwind is executed, and then $ group on multiple fields

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