Screen Scraping with nokogiri

Question

我是一个全栈ruby开发人员。我正试图从网站上刮到数据，我成功地获得了数据。但问题是，下次当我获取数据时，我只想获取新的数据，我不想覆盖数据库中的所有数据。我只想添加最近添加的新记录。但我不能找到任何解决方案，如何做到这一点与最少的查询和最少的代码。

这是我的代码，我使用的报废:

   client = Mechanize.new
         index_page = client.get('https://www.google.com/')
         document_page_index = Nokogiri::HTML::Document.parse(index_page.body)
         page_no_merchant = document_page_index.css('.pagination.pagination-centered ul li:nth-last-child(2) a').text.to_i
         1.upto(page_no_merchant) do |page_number|
             client.get("https://www.google.com/buy-gift-cards?page=#{page_number}") do |page|
                 document = Nokogiri::HTML::Document.parse(page.body)

                 document.css('.product-source').each do |item|
                    merchant_name= item.children.css('.name').text.gsub("Gift Cards", "")
                     puts merchant_name
                     href = item.css('a').first.attr('href')
                     puts href
                     image_url=item.children.css('.img img').attr('data-src').text.strip
                     puts image_url
                      image_url=URI.parse(image_url)
                      @merchant=Merchant.create!(name: merchant_name , image_url:image_url)
                     first_page = client.get("https://www.google.com#{href}")
                     document_page = Nokogiri::HTML::Document.parse(first_page.body)
                     page_no = document_page.css('.pagination.pagination-centered ul li:nth-last-child(2) a').text.to_i
                     1.upto(page_no) do |page_number_giftcard|
                       type1=[]
                         card_page = client.get("https://www.google.com#{href}?page=#{page_number_giftcard}")
                         document_page = Nokogiri::HTML::Document.parse(card_page.body)
                         document_page.xpath('//table/tbody/tr[@class="toggle-details"]').collect do |row|

                           row.at("td[2] ul").children.each do |typeli|
                           type = typeli.text.strip if typeli.text.strip.length != 0
                           type1 << type if typeli.text.strip.length != 0
                           end
                             value = row.at('td[3]').text.strip
                             value = value.to_s.tr('$', '').to_f
                             puts value
                             per_discount = row.at('td[4]').text.strip
                             per_discount = per_discount.to_s.tr('%', '').to_f
                             puts per_discount
                             final_price = row.at('td[5] strong').text.strip
                             final_price = final_price.to_s.tr('$', '').to_f
                             puts final_price
                             puts '******************************'
                               @giftcard=Giftcard.create(card_type:1, card_value:value, per_off:per_discount, card_price: final_price, merchant_id: @merchant.id)
                         end
                           @giftcard.update_attribute()
                     end
                 end
             end
         end

提前感谢。

Answer 1

这样做基本上是在保存所有数据。

@merchant=Merchant.create!(name: merchant_name , image_url:image_url)

你可以试试find_or_create_by。

@merchant=Merchant.find_or_create_by(name: merchant_name , image_url:image_url)

http://apidock.com/rails/v4.0.2/ActiveRecord/Relation/first_or_createhttp://apidock.com/rails/v4.0.2/ActiveRecord/Relation/find_or_create_by