Return document in each group with max value using MongoDB

Question

Given a dataset:

{_id: 0, type: \'banana\', amount: 5}
{_id: 1, type: \'banana\', amount: 3}
{_id: 2, type: \'apple\', amount: 8}
{_id: 3, type: \'apple\', a         


        

Answer 1

You can use below aggregation with $sort amount descending followed by $first operator to project max amount document.

$replaceRoot to promote the max amount document to top level.

collection.aggregate([
 {$sort:{'amount':-1}}, 
 {$group:{ _id: '$type',group:{$first:'$$ROOT'}}},
 {$replaceRoot:{newRoot:"$group"}}
])