MongoDB concurrent update with sub collection?

To perform concurrent updates with sub collections in MongoDB, use the update() method combined with the $push operator and dot notation to reach nested fields within embedded documents and arrays.

Syntax

db.collection.update(
    { "field": "value" },
    { $push: { "parentField.subField.arrayField": newValue } }
);

Create Sample Data

Let us create a collection with documents ?

db.demo547.insertOne({
    Name: "Chris",
    Test: {
        "FirstTest": {
            Scores: [56, 29, 76]
        },
        "SecondTest": {
            Scores: [98, 91, 78]
        }
    }
});

{
    "acknowledged": true,
    "insertedId": ObjectId("5e8e2d579e5f92834d7f05dd")
}

Display Current Data

db.demo547.find();

{
    "_id": ObjectId("5e8e2d579e5f92834d7f05dd"),
    "Name": "Chris",
    "Test": {
        "FirstTest": {
            "Scores": [56, 29, 76]
        },
        "SecondTest": {
            "Scores": [98, 91, 78]
        }
    }
}

Concurrent Update with Sub Collection

Following is the query for concurrent update with subcollection ?

db.demo547.update(
    {"Name": "Chris"},
    { $push: { "Test.FirstTest.Scores": 99 } }
);

WriteResult({ "nMatched": 1, "nUpserted": 0, "nModified": 1 })

Verify Result

db.demo547.find();

{
    "_id": ObjectId("5e8e2d579e5f92834d7f05dd"),
    "Name": "Chris",
    "Test": {
        "FirstTest": {
            "Scores": [56, 29, 76, 99]
        },
        "SecondTest": {
            "Scores": [98, 91, 78]
        }
    }
}

Conclusion

Use $push with dot notation to append values to arrays within nested sub collections. The dot notation "Test.FirstTest.Scores" traverses the nested document structure to reach the target array for concurrent updates.