Schema Evolution

In this example, we implemented the updated reviews schema to include an optional locale field, in the properties document, which accepts only fr or en values:

const bookstore_reviews_international = {
    bsonType: "object",
    required: [“_id”, "review_id", "user_id", "timestamp", "review", "rating"],
    additionalProperties: false,
    properties: {
        _id: { bsonType: "objectId" },
        review_id: { bsonType: "string" },
        user_id: { bsonType: "string" },
        timestamp: { bsonType: "date" },
        review: { bsonType: "string" },
        rating: {
            bsonType: "int",
            minimum: 0,
            maximum: 5,
        },
        comments: {
            bsonType: "array",
            maxItems: 3,
            items: {
                bsonType: "object",
            },
        },
        locale: { 
            enum: [“en”, “fr”]},
        },
    },
};

To enable or update schema validation for the existing collection, use the collMod command and provide the validator option. In our example, we used the $jsonSchema operator to build the validator and set the validation level and validation action options to moderate and warn:

const schema_validation_international = 
{ $jsonSchema: bookstore_reviews_international };

db.runCommand({
    collMod: "reviews",
    validator: schema_validation_international,
    validationLevel: "moderate",
    validationAction: "warn",
});