Creation of duplicate IDs in arrays of different documents in mongo db

Question

I want to add an element to the array of all collections in the city collection, but Mongo creates the ID as duplicate.

this is my code

await this.cityRepository.updateMany(
    {},
    {
      $push: {
        tags: {
          title: tagValue.title,
          description: tagValue.description,
          applyToAllCity: tagValue.cityId ? false : true,
        },
      },
    },
  );

City Schema

export class BaseCity extends Document {
  @Prop({
    type: String,
    required: true,
  })
  _id: string;

  @Prop({ type: String, unique: true })
  code: string;
  @Prop({ type: String, ref: Province.name })
  province: string | Province;
  @Prop({ type: String })
  faName: string;
}

@Schema({ timestamps: true })
@Schema({ collection: 'city', virtuals: true, _id: false, timestamps: true })
export class City extends BaseCity {
  @Prop({ type: String })
  imageName: string;

  @Prop({ index: true, type: String })
  enName: string;

  @Prop({ type: Number })
  displayOrder: number;

  @Prop({ type: Boolean })
  isFeatured: boolean;

  @Prop({ type: Boolean })
  isEnabled: boolean;

  @Prop({ type: Coordinate })
  coordinate: Coordinate;

  @Prop([{ type: Region, ref: Region.name, default: [] }])
  region: Region[];

  @Prop([{ type: SubMenu }])
  subMenu: SubMenu[];
  @Prop([{ type: CityTags }])
  tags: CityTags[];
}

const CitySchema = SchemaFactory.createForClass(City);

CitySchema.index({ faName: 'text' });

export { CitySchema };

DB

As you can see, ID 63ec8f47efbd82c8face341a is duplicated in all documents.

Is there a solution to solve this problem?

Answer 1

To avoid duplicate IDs, you could use the $addToSet instead of $push. The $addToSet adds an element to an array only if it does not already exist in the set.

Check this:

await this.cityRepository.updateMany(
    {},
    {
      $addToSet: {
        tags: {
          title: tagValue.title,
          description: tagValue.description,
          applyToAllCity: tagValue.cityId ? false : true,
        },
      },
    },
  );

Update:

To keep unique ids

await this.cityRepository.updateMany(
    {},
    {
      $push: {
        tags: {
          _id: new ObjectId(),
          title: tagValue.title,
          description: tagValue.description,
          applyToAllCity: tagValue.cityId ? false : true,
        },
      },
    },
  );