How to make sure that a combination of keys is unique in nested documents

[JuliusMoehring]

It may be that this is a stupid question and the approach itself is completely wrong, but I would still like to get rid of the question:

I have a category that can have subcategories. However, I don't want a category with the same name and the same locale to exist twice.

My idea was to make a unique key out of "locale" and "name", but I failed with that.

Here is the code:

export interface ILocalizedCategory {
    locale: LocaleEnum;
    name: string;
    createdAt: Date;
    updatedAt: Date;
}

export interface ICategory extends MongoResult {
    localizedFields: ILocalizedCategory[];
    children: ICategory[];
    createdAt: Date;
    updatedAt: Date;
}

const LocalizedCategorySchema: Schema = new Schema({
    locale: {
        type: String,
        required: true,
        enum: Object.values(LocaleEnum),
        index: true,
    },
    name: {
        type: String,
        required: true,
        index: true,
    },
    createdAt: {
        type: Date,
        required: true,
        default: new Date(),
        immutable: true,
    },
    updatedAt: {
        type: Date,
        required: true,
        default: new Date(),
    },
});

LocalizedCategorySchema.index({locale: 1, name: 1}, {unique: true});

const CategorySchema: Schema = new Schema({
    localizedFields: {
        type: [LocalizedCategorySchema],
        required: true,
    },
    createdAt: {
        type: Date,
        required: true,
        default: new Date(),
        immutable: true,
    },
    updatedAt: {
        type: Date,
        required: true,
        default: new Date(),
    },
});

CategorySchema.add({
    children: {
        type: [CategorySchema],
        required: true,
        default: [],
    },
});

export const Category = mongoose.model<ICategory>('Category', CategorySchema);

Is this possible at all or should I take a completely different approach and for example create all categories as separate documents and only put the ObjectID of the subcategories into the child array?

Thanks for your help!

[vkarpov15]

The approach you specified will make sure there aren't multiple Category documents that have the same locale, name, but one Category document can still have duplicate locale, name. Try mongoose-unique-array, and open an issue on that repo with a repro script if that doesn't work 👍