t.rb

    def export
      favorites = Favorite.all
      @products = Product.where(id: favorites.map(&:product_id).uniq)

      count = favorites.group_by(&:product_id).map do |product_id, favorites|
        [@products.find { |product| product.id == product_id }, favorites.length]
      end

      @favorite_count = count.sort_by { |arr| arr.last }.reverse.to_h
    end

SQL: