[{"_id":ObjectId("5d2040f9f7c5ac1e9d8ef712"),"lang_content_list":[{"lang":"en"},{"lang":"np"}],"_class":"com.sn.application.model.Product"},{"_id":ObjectId("5d2040f9f7c5ac1e548ef712"),"lang_content_list":[{"lang":"es"},{"lang":"ar"}],"_class":"com.sn.application.model.Product"}]

db.collection.aggregate([{$match:{"lang_content_list.lang":"en"}},{$unwind:"$lang_content_list"},{$match:{"lang_content_list.lang":"en"}},{$group:{"_id":"$_id","_class":{$first:"$_class"},"lang_content_list":{$push:"$lang_content_list"}}}])