Database
[{name:"John",a:20,b:30,c:40,d:50},{name:"Rich",a:20,b:30,c:40,d:50},{name:"Anne",a:20,b:30,c:40,d:50},{name:"Sam",a:20,b:30,c:40,d:50}]
Query
db.collection.aggregate([{$project:{_id:0,fields:{$filter:{input:{$objectToArray:"$$ROOT"},cond:{$eq:[{$type:"$$this.v"},"double"]}}}}},{$unwind:"$fields"},{$group:{_id:"$fields.k",total:{$sum:"$fields.v"}}},{$group:{_id:null,aggregates:{$push:{k:"$_id",v:"$total"}}}},{$replaceRoot:{newRoot:{$arrayToObject:"$aggregates"}}}])