mongodb count value of one field based on other -

i have collection named genre_collection of following structure :

user     | genres  ----------------  1       |   comedy  1       |   action  1       |   thriller  1       |   comedy  1       |   action  2       |   war  2       |   adventure  2       |   war  2       |   thriller 

i'm trying find count each genre each user i.e. ideal final result :

1 | comedy |2 1 | action |1 1 | thriller |1 2 | war |2 2 | adventure |1 2 | thriller |1 

any helps useful.

you can aggregation using $group

try :

db.genre_collection.aggregate([    {       $group:{          _id:{             genre:"$genres",             user:"$user"          },          count:{             $sum:1          }       }    } ]) 

output:

{ "_id" : { "genre" : "adventure", "user" : 2 }, "count" : 1 } { "_id" : { "genre" : "action", "user" : 1 }, "count" : 2 } { "_id" : { "genre" : "thriller", "user" : 2 }, "count" : 1 } { "_id" : { "genre" : "war", "user" : 2 }, "count" : 2 } { "_id" : { "genre" : "comedy", "user" : 1 }, "count" : 2 } { "_id" : { "genre" : "thriller", "user" : 1 }, "count" : 1 }