Rails activeRecord 补丁和提交答案

【问题标题】：Rails activeRecord patch and commitRails activeRecord 补丁和提交
【发布时间】：2014-08-29 20:26:04
【问题描述】：

我正在使用 Rails 开发一个标记的博客系统。现在它可以使用连接表，但我对性能有些怀疑。

现在，每次我创建博客及其关联标签时，它都会将每条语句提交到数据库。我认为更好的做法应该是修补所有这些语句并只提交一次数据库。在rails中可以吗？

创建日志转储：

Started POST "/articles" for 127.0.0.1 at 2014-08-29 15:30:48 -0400
Processing by ArticlesController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"K4rWQEh0810X2jMe/Z9pC/PN2WeOcO0F0TkjKUZTPec=", "title"=>"test27", "text"=>"ddddd", "tag"=>"a,k,g", "commit"=>"Submit"}
Unpermitted parameters: utf8, authenticity_token, tag, commit
   (0.9ms)  BEGIN
  SQL (0.3ms)  INSERT INTO `articles` (`created_at`, `text`, `title`, `updated_at`) VALUES ('2014-08-29 19:30:48', 'ddddd', 'test27', '2014-08-29 19:30:48')
   (0.2ms)  COMMIT
  Tag Load (0.3ms)  SELECT  `tags`.* FROM `tags`  WHERE `tags`.`name` = 'a' LIMIT 1
   (0.2ms)  BEGIN
  SQL (0.3ms)  INSERT INTO `articles_tags` (`article_id`, `tag_id`) VALUES (28, 1)
   (0.2ms)  COMMIT
  Tag Load (0.2ms)  SELECT  `tags`.* FROM `tags`  WHERE `tags`.`name` = 'k' LIMIT 1
   (0.1ms)  BEGIN
  SQL (0.2ms)  INSERT INTO `tags` (`name`) VALUES ('k')
   (0.1ms)  COMMIT
   (0.1ms)  BEGIN
  SQL (0.3ms)  INSERT INTO `articles_tags` (`article_id`, `tag_id`) VALUES (28, 17)
   (8.3ms)  COMMIT
  Tag Load (0.3ms)  SELECT  `tags`.* FROM `tags`  WHERE `tags`.`name` = 'g' LIMIT 1
   (0.1ms)  BEGIN
  SQL (0.2ms)  INSERT INTO `tags` (`name`) VALUES ('g')
   (0.1ms)  COMMIT
   (0.1ms)  BEGIN
  SQL (0.4ms)  INSERT INTO `articles_tags` (`article_id`, `tag_id`) VALUES (28, 18)
   (0.2ms)  COMMIT

模型设计：

class Article < ActiveRecord::Base
    has_and_belongs_to_many :tag
end

class Tag < ActiveRecord::Base
    has_and_belongs_to_many :article, :uniq => true
end

博客创建代码：

    def create
        @article = Article.new(article_params)
        tag_arr = params[:tag].split(',')

        if @article.save
          tag_arr.each do |name|
                tag = Tag.find_or_create_by(name: name) # create a new tag only if tag.name not exist
                @article.tag << tag
          end
          redirect_to @article
        else
          render 'new'
        end
    end

【问题讨论】：

标签： ruby-on-rails database activerecord

【解决方案1】：

要将文章和标签保存在单个事务中，请将操作包装在 transaction 块中。

def create
  @article = Article.new(article_params)
  tag_arr = params[:tag].split(',')

  Article.transaction do
    if @article.save
      tag_arr.each do |name|
        article.tags.find_or_create_by(name: name)
      end
    end
  end

  if @article.new_record?
    render 'new'
  else
    redirect_to @article
  end
end

这将导致 SQL 查询类似于：

(0.9ms)  BEGIN
SQL (0.3ms)  INSERT INTO `articles` (`created_at`, `text`, `title`, `updated_at`) VALUES ('2014-08-29 19:30:48', 'ddddd', 'test27', '2014-08-29 19:30:48')
Tag Load (0.3ms)  SELECT  `tags`.* FROM `tags`  WHERE `tags`.`name` = 'a' LIMIT 1
SQL (0.3ms)  INSERT INTO `articles_tags` (`article_id`, `tag_id`) VALUES (28, 1)
Tag Load (0.2ms)  SELECT  `tags`.* FROM `tags`  WHERE `tags`.`name` = 'k' LIMIT 1
SQL (0.2ms)  INSERT INTO `tags` (`name`) VALUES ('k')
SQL (0.3ms)  INSERT INTO `articles_tags` (`article_id`, `tag_id`) VALUES (28, 17)
Tag Load (0.3ms)  SELECT  `tags`.* FROM `tags`  WHERE `tags`.`name` = 'g' LIMIT 1
SQL (0.2ms)  INSERT INTO `tags` (`name`) VALUES ('g')
SQL (0.4ms)  INSERT INTO `articles_tags` (`article_id`, `tag_id`) VALUES (28, 18)
(0.2ms)  COMMIT

【讨论】：