MongoDB: Create Object in Aggregation result

Question

I want to return Object as a field in my Aggregation result similar to the solution in this question. However in the solution mentioned above, the Aggregation results in an Array of Objects with just one item in that array, not a standalone Object. For example, a query like the following with a $push operation

 $group:{
     _id: "$publisherId",
     'values' : { $push:{
         newCount: { $sum: "$newField" },
         oldCount: { $sum: "$oldField" } }
     }
}

returns a result like this

{
        "_id" : 2,
        "values" : [ 
            {
                "newCount" : 100, 
                "oldCount" : 200
            }
        ]
    }
}

not one like this

{
        "_id" : 2,
        "values" : {
                "newCount" : 100, 
                "oldCount" : 200
         }
    }
}

The latter is the result that I require. So how do I rewrite the query to get a result like that? Is it possible or is the former result the best I can get?

chridam · Accepted Answer · 2016-05-23 12:29:28Z

13

You don't need the $push operator, just add a final $project pipeline that will create the embedded document. Follow this guideline:

var pipeline = [
    {
        "$group": {
            "_id": "$publisherId",      
            "newCount": { "$sum": "$newField" },
            "oldCount": { "$sum": "$oldField" } 
        }
    },
    {
        "$project" {
            "values": {
                "newCount": "$newCount",
                "oldCount": "$oldCount"
            }
        }       
    }   
];

db.collection.aggregate(pipeline);

edited May 23, 2016 at 12:29

answered May 23, 2016 at 12:21

chridam

104k26 gold badges246 silver badges243 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

MongoDB: Create Object in Aggregation result

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related