Mongo DB find all records with highest value depending on a key field

Question

I would like to get for each user in my collection the comment of the record with the highest value.

//myCol
[
    {\'user\' : 1, \'value\':20, \"comment\":          


        

Answer 1

You can $sort your documents by value before applying $group with $first

db.myCol.aggregate([
    { 
        $sort: { value: -1 }
    },
    {
        $group: {
            _id: "$user",
            value: { $first: "$value" },
            comment: { $first: "$comment" },
            date: { $first: "$date" }
        }
    },
    {
        $sort: { _id: 1 }
    },
    {
        $project: {
            user: "$_id",
            _id: 0,
            value: 1,
            comment: 1,
            date: 1
        }
    }
])