section24.6.md

Section 24.6: Indexes in models

MongoDB supports secondary indexes. In Mongoose, we define these indexes within our schema. Defining indexes at schema level is necessary when we need to create compound indexes.

Mongoose Connection

let strConnection = 'mongodb://localhost:27017/dbName';
let db = mongoose.createConnection(strConnection)

Creating a basic schema

let Schema = require('mongoose').Schema;
let usersSchema = new Schema({
  username: {
    type: String,
    required: true,
    unique: true
  },
  email: {
    type: String,
    required: true
  },
  password: {
    type: String,
    required: true
  },
  created: {
    type: Date,
    default: Date.now
  }
});

let usersModel = db.model('users', usersSchema);
module.exports = usersModel;

By default, mongoose adds two new fields into our model, even when those are not defined in the model. Those fields are:

• _id
• __v

If you don't want an _id added to your schema at all, you may disable it using this option.

let usersSchema = new Schema({
  username: {
    type: String,
    required: true,
    unique: true
  }, {
    _id: false
  }
);

You can easy disable this field in the model configuration:

let usersSchema = new Schema({
  username: {
    type: String,
    required: true,
    unique: true
  }, {
    versionKey: false
  }
);

Compound indexes

We can create another indexes besides those Mongoose creates.

usersSchema.index({username: 1 });
usersSchema.index({email: 1 });

In these case our model have two more indexes, one for the field username and another for email field. But we can create compound indexes.

usersSchema.index({username: 1, email: 1 });