MongoDB/Mongoose schema unique not working

Question

I want to create a city with name and some other fields, the name should be unique but I am able to create other cities with the same name. How do I make the name unique in mongoose schema in order to obtain unique cities in the database?

cities.service.ts

@Injectable()
export class CitiesService {

  constructor(
    @InjectModel('City') private readonly cityModel: Model<City>,
  ) {}

  async createCity(createCityDto: CreateCityDto) {
      const { name } = createCityDto;
      const city = new this.cityModel({ name });
      await city.save();
      return city;
  }
}

cities.controller.ts

@Post()
  @ApiCreatedResponse({ description: 'Create a new city' })
  @ApiBody({ type: CreateCityDto })
  @ApiConflictResponse({ description: 'This city already exists' })
  createCity(@Body() createCityDto: CreateCityDto) {
    return this.citiesService.createCity(createCityDto);
  }

city.model.ts

import * as mongoose from 'mongoose';

export const CitySchema = new mongoose.Schema({
  name: {
    type: String,
    required: true,
    unique: true,
  }
});

export interface City {
  id: mongoose.Schema.Types.ObjectId;
  name: string;
}

Answer 1

Make sure to set autoIndex on your connection to the database. Also make sure that you data doesn't already have mess-ups. If you already have 2 names that are not unique in your database it will not follow the option.