Golang mgo возвращающее значение с агрегатом $ group

Question

Как получить агрегированный запрос для возврата значений полей, используемых в выражении $ group.

Код:

type TheGroup struct{ 
    Id bson.ObjectId `json:"id,omitempty" bson:"_id,omitempty"` 
    Totalamount int 
    Dayofyear int 
    Actualyear string 
    Transactiondate string 
    Count int 
} 

var results []TheGroup 

o1 := bson.M{"$match" :bson.M{"transactiontype": transactiontype},} 
o2 := bson.M{"$group" : bson.M{"_id": bson.M{"day": "$dayofyear", "year":"$actualyear"},"totalamount":bson.M{"$sum":"$qty"}, "count":bson.M{"$sum":1}},} 
operations := []bson.M{o1, o2} 
pipe := collection.Pipe(operations) 
err1 := pipe.All(&results) 

if err := json.NewEncoder(w).Encode(results); err != nil { 
panic(err) 
} 

Выход следующим образом:

[{"Totalamount":2061,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":679},{"Totalamount":8705,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":2145},{"Totalamount":8156,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":2806},{"Totalamount":9865,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":3294},{"Totalamount":9619,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":3102},{"Totalamount":9975,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":3457},{"Totalamount":14839,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":4036},{"Totalamount":5100,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":1699},{"Totalamount":9649,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":2854},{"Totalamount":11457,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":3220},{"Totalamount":12643,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":3860},{"Totalamount":10301,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":3620},{"Totalamount":7681,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":2816},{"Totalamount":8130,"Dayofyear":0,"Actualyear":"","Transactiondate":"","Count":3023}] 

Я думаю, что я понимаю, почему DayOfYear/Actualyear не заполняются - потому что, как нет aggregration значений документа в качестве согласованные документы пересекаются группой $ - но как я могу их заселить?

Answer 1

Запуск следующего трубопровода в Монго оболочке должны дать вам правильный результат:

pipeline = [ 
    { 
     "$match": { "transactiontype": transactiontype } 
    }, 
    { 
     "$group": { 
      "_id": { 
       "year": { "$year": "$transactiondate" }, 
       "dayOfYear": { "$dayOfYear": "$transactiondate" }    
      }, 
      "totalamount": { "$sum": "$qty" }, 
      "count": { "$sum": 1 }, 
      "date": { "$first": "$transactiondate"} 
     } 
    }, 
    { 
     "$project": { 
      "_id": 0, 
      "totalamount": 1, 
      "dayOfYear": "$_id.dayOfYear", 
      "actualyear": { "$substr": [ "$_id.year", 0, 4 ] }, 
      "transactiondate": { 
       "$dateToString": { "format": "%Y-%m-%d %H:%M", "date": "$date" } 
      }, 
      "count": 1 
     } 
    } 
] 
db.collection.aggregate(pipeline) 

из которых эквивалентного выражения ЕГО следующим образом (непроверенный):

pipeline := []bson.M{ 
    bson.M{ 
     "$match": bson.M{ "transactiontype": transactiontype } 
    }, 
    bson.M{ 
     "$group": bson.M{ 
      "_id": bson.M{ 
       "year": bson.M{ "$year": "$transactiondate" }, 
       "dayOfYear": bson.M{ "$dayOfYear": "$transactiondate" }    
      }, 
      "totalamount": bson.M{ "$sum": "$qty" }, 
      "count": bson.M{ "$sum": 1 }, 
      "date": bson.M{ "$first": "$transactiondate"} 
     } 
    }, 
    bson.M{ 
     "$project": bson.M{ 
      "_id": 0, 
      "totalamount": 1, 
      "dayOfYear": "$_id.dayOfYear", 
      "actualyear": bson.M{ "$substr": []interface{}{ "$_id.year", 0, 4 } }, 
      "transactiondate": bson.M{ 
       "$dateToString": bson.M{ "format": "%Y-%m-%d %H:%M", "date": "$date" } 
      }, 
      "count": 1 
     } 
    } 
} 

pipe := collection.Pipe(pipeline)