Update an array of strings nested within an array of objects in MongoDB

To update an array of strings nested within an array of objects in MongoDB, use the $pull operator with the positional all operator $[] to remove elements from nested arrays across all array elements.

Syntax

db.collection.updateMany(
    { query },
    { $pull: { "arrayField.$[].nestedArray": "valueToRemove" } }
);

Sample Data

db.demo412.insertOne({
    "Information1": [
        {
            "Information2": [
                "John",
                "David"
            ]
        },
        {
            "Information2": [
                "Mike"
            ]
        }
    ]
});

{
    "acknowledged": true,
    "insertedId": ObjectId("5e70f38b15dc524f70227683")
}

Display Current Document

db.demo412.find();

{
    "_id": ObjectId("5e70f38b15dc524f70227683"),
    "Information1": [
        { "Information2": ["John", "David"] },
        { "Information2": ["Mike"] }
    ]
}

Example: Remove "Mike" from All Nested Arrays

db.demo412.updateMany(
    { _id: ObjectId("5e70f38b15dc524f70227683") },
    { $pull: { 'Information1.$[].Information2': "Mike" } }
);

{ "acknowledged": true, "matchedCount": 1, "modifiedCount": 1 }

Verify Result

db.demo412.find();

{
    "_id": ObjectId("5e70f38b15dc524f70227683"),
    "Information1": [
        { "Information2": ["John", "David"] },
        { "Information2": [] }
    ]
}

Key Points

• $[] applies the operation to all elements in the outer array.
• $pull removes all occurrences of the specified value from arrays.
• Use dot notation to access nested arrays within objects.

Conclusion

The $pull operator with $[] effectively removes values from nested string arrays across all objects in the parent array. This approach works when you need to clean up data from multiple nested locations simultaneously.