How to Sort Embedded Arrays in MongoDB Collections?

Sorting Embedded Arrays in MongoDB Collections

Problem:

You have a MongoDB collection of student records, each containing an embedded array of scores. You wish to sort the scores array in descending order of score for a specific document.

Solution:

To sort an embedded array, you can utilize either custom application code or the Aggregation Framework introduced in MongoDB 2.2.

Using Aggregation Framework:

The following MongoDB shell aggregation pipeline sorts the scores array of the document with _id 1 in descending order of score:

db.students.aggregate(
    { $match: {
        _id : 1
    }},
    { $unwind: '$scores' },
    { $match: {
        'scores.type': 'homework'
    }},
    { $sort: {
        'scores.score': -1
    }}
)

Output:

This aggregation produces the following output, showing the sorted homework scores for the student with _id 1:

{
    "result" : [
        {
            "_id" : 1,
            "name" : "Aurelia Menendez",
            "scores" : {
                "type" : "homework",
                "score" : 71.76133439165544
            }
        },
        {
            "_id" : 1,
            "name" : "Aurelia Menendez",
            "scores" : {
                "type" : "homework",
                "score" : 34.85718117893772
            }
        }
    ],
    "ok" : 1
}

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