Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{_id:1,customer_id:"100"},{_id:2,customer_id:"100"},{_id:3,customer_id:"200"}]
Query
db.collection.aggregate([{$group:{_id:"$customer_id",total_count:{$sum:1}}}])
Result