问Mongodb聚合管道如何限制群组推流

EN

[
    {
        "submitted": date,
        "loc": {
            "lng": 13.739251,
            "lat": 51.049893
        },
        "name": "first",
        "preview": "my first"
    },
    {
        "submitted": date,
        "loc": {
            "lng": 13.639241,
            "lat": 51.149883
        },
        "name": "second",
        "preview": "my second"
    },
    {
        "submitted": date,
        "loc": {
            "lng": 13.715422,
            "lat": 51.056384
        },
        "name": "nearpoint2",
        "preview": "my nearpoint2"
    }
]

  var pipeline = [{
    //I want to limit the data to a certain area
    $match: {
        loc: {
            $geoWithin: {
                $box: [
                    [locBottomLeft.lng, locBottomLeft.lat],
                    [locUpperRight.lng, locUpperRight.lat]
                ]
            }
        }
    }
},
// I just want to get the latest entries  
{
    $sort: {
        submitted: -1
    }
},
// I group by name
{
    $group: {
        _id: "$name",
        < --get name
        submitted: {
            $max: "$submitted"
        },
        < --get the latest date
        locs: {
            $push: "$loc"
        },
        < --push every loc into an array THIS SHOULD BE LIMITED TO AN AMOUNT 5 or 10
        preview: {
            $first: "$preview"
        }
    }
},
//Limit the query to at least 10 entries.
{
    $limit: 10
}
];