Finding embedded document by unique property in Mongoose ODM

Question

Finding embedded document by unique property in Mongoose ODM

We have this Schemes:

var SubsetSchema = new mongoose.Schema({
    number: {
        type: Number,
        index: true,
        unique: true,
    },
    name: String,
});

var RootSchema = new mongoose.Schema({
    name: String,
    subsets: [SubsetSchema],
});

mongoose.model('collection', RootSchema);
var Root = module.exports = mongoose.model('collection');

How would i perform search for a single Subset document across the whole collection where number = 3?

And i am not clear. In the case of schema above, would number be unique in the entire collection or per Root document?

node.js
mongodb
mongoose

Answer 1

You could use dot notation in the query and the $ positional operator in the projection to filter the output to just the matched subsets element like this:

Root.findOne({'subsets.number': 3}, {_id: 0, 'subsets.$': 1}, ...);

Regarding your second question, number would be enforced as unique across the entire collection, but (counter-intuitively) would still be allowed to exist multiple times in the same Root document.