graphql.ts

// graphql.ts

// ...other codes

enum PaginationSortByEnum {
  ASC = 'asc',
  DESC = 'desc'
}

interface IPagination {
  limit: number
  offset: number
  orderBy: string
  sortBy: PaginationSortByEnum
  search: string
}

const loaders = () => {
  let productsPagination: IPagination;
  const productsByMerchantIdLoader = new Dataloader(async merchantIds => {
    const connection = Knex(config.get('database'));
    const table = connection('products');
    const {limit, offset, orderBy, sortBy, search} = productsPagination;
    if(search)
        table.where('name', 'LIKE', `%${search}%`)
    const products = await connection.union(
        merchantIds.map(id =>
            table
                .where('merchantId', id)
                .orderBy(orderBy, sortBy)
                .limit(limit)
                .offset(offset)
        ),
        true //option for wrap queries
    );
    return merchantIds.map(merchantId => products.filter(product => product.merchantId === merchantId));
  });

  return {
    getLocationsByMerchantId: new Dataloader(async merchantIds => {
      const locations = await Knex(config.get('database'))('locations')
        .whereIn('merchantId', merchantIds);
      return merchantIds.map(merchantId => locations.find(location => location.merchantId === merchantId));
    }),
    getProductsByMerchantId(pagination: IPagination){
      productsPagination = pagination;
      return productsByMerchantIdLoader;
    }
  };
};

// ...other codes

@alfari16 thanks for your great article on medium.com. I was wondering how you would return the total number of results to the client.