How to query an array of objects in mongodb

Question

I have an object structure as shown below

{
    "_id" : ObjectId("55d164f1c8f2c53a82535b9a"),
    "plant_name" : "TOTAL",
    "installed_capacity" : 3473,
    "wind_data" : [ 
        {
            "date" : "16-08-15",
            "timestamp" : " 16:27:15",
            "generated_capacity" : 617.24,
            "frequency" : 50.01
        }, 
        {
            "date" : "16-08-15",
            "timestamp" : " 21:21:15",
            "generated_capacity" : 670.25,
            "frequency" : 49.94
        }, ....]
}

I need to sum up (at least retrieve) "generated_capacity" of all the objects under "wind_data" having "date" equal to "16-08-15" of "TOTAL" object. I have tried this query

   db.collectionName.aggregate(
      {"$unwind":"$wind_data"},
      {"$match":{"plant_name":"TOTAL","wind_data.date":"16-08-15"}}
      )

But, this query is not working. Please suggest some way to figure this out.

You are missing a closing quote, and you really should also $match first as well, but otherwise this should be working up to this point. What is wrong? — Blakes Seven
– Blakes Seven, Commented Aug 17, 2015 at 6:51
It returns all the fields of the object. How to find the sum of particular field inside the array. Like "generated_capacity" inside the array. — chaitu
– chaitu, Commented Aug 17, 2015 at 6:56
add this after match {"$group":{"_id":"$wind_data.date","generated_capacity_sum":{"$sum":"$generated_capacity}}} — Neo-coder
– Neo-coder, Commented Aug 17, 2015 at 6:58
This is a very basic operation. You should spend some time reading SQL to Aggregation Mapping Chart which includes things like this as common examples. — Blakes Seven
– Blakes Seven, Commented Aug 17, 2015 at 7:01
Thanks @BlakesSeven . i am two days old to this querying in mongodb. Couldnt find any useful material. Anyway thanks for sharing. Will build upon this — chaitu
– chaitu, Commented Aug 17, 2015 at 7:06

Arun K · Accepted Answer · 2015-08-17 09:48:56Z

0

The following query would do the job

    db.collectionName.aggregate([      
      {"$unwind":"$wind_data"},       
      {"$match":{"plant_name":"TOTAL","wind_data.date":"16-08-15"}},
      {"$group":{"_id":"$wind_data.date","generated_capacity_sum":{"$sum":"$wind_data.generated_capacity"}}}
    ])

answered Aug 17, 2015 at 9:48

Arun K

2521 silver badge5 bronze badges

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

Collectives™ on Stack Overflow

How to query an array of objects in mongodb

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