Mongoose Index on a field in nested document

Question

I have a small schema

var PostSchema = new mongoose.Schema({
  title: String,
  link: String,
  author: {type:String,required:true},
  upvotes: {type: Number, default: 0},
  nesteddoc : {
      field1: String
  }
});

//This is broken - index on field1
PostSchema.index({nesteddoc.field1:1},{unique:true});

Is it possible to have an index on nested field by specifying in Mongoose schema and not running a MongoDB query to ensure the index ?

Answer 1

Use quotes around "nesteddoc.field1" to evaluate the nested field :

PostSchema.index({ "nesteddoc.field1": 1 }, { unique: true });

Furthermore, mongoose will call ensureIndex internally, from mongoose doc :

When your application starts up, Mongoose automatically calls ensureIndex for each defined index in your schema. Mongoose will call ensureIndex for each index sequentially, and emit an 'index' event on the model when all the ensureIndex calls succeeded or when there was an error. While nice for development, it is recommended this behavior be disabled in production since index creation can cause a significant performance impact. Disable the behavior by setting the autoIndex option of your schema to false, or globally on the connection by setting the option config.autoIndex to false.

You can also define index in schema :

var PostSchema = new mongoose.Schema({
    title: String,
    link: String,
    author: { type: String, required: true },
    upvotes: { type: Number, default: 0 },
    nesteddoc: {
        field1: { type: String, unique: true, index: true },
    }
});