ruby-on-rails – Rails 3 – 如何从带有订单的模型中获取行号

我正在整理一个具有排行榜概念的小应用程序.基本上,模型只是一个player_name和一个current_score.

我想要做的是获得特定玩家的排名,并且考虑到新的分数一直在进行,它需要是动态的.显然,我可以使用order by子句进行正常查找,然后我必须循环遍历每条记录.当我有100,000行时,效率不高.

我应该采取什么方法的任何建议？

以下是表的迁移：

class CreateScores < ActiveRecord::Migration
  def self.up
    create_table :scores do |t|
      t.string  :player_name
      t.integer :current_score

      t.timestamps
    end
  end

  def self.down
    drop_table :scores
  end
end

编辑
举个例子,我有以下几点：

Score.select('player_name,current_score').limit(20)
=> [#<Score player_name: "Keith Hughes",current_score: 9>,#<Score player_name: "Diane Chapman",current_score: 8>,#<Score player_name: "Helen Dixon",current_score: 4>,#<Score player_name: "Donald Lynch",#<Score player_name: "Shawn Snyder",current_score: 2>,#<Score player_name: "Nancy Palmer",#<Score player_name: "Janet Arnold",current_score: 1>,#<Score player_name: "Sharon Torres",#<Score player_name: "Keith Ortiz",current_score: 5>,#<Score player_name: "Judith Day",current_score: 3>,#<Score player_name: "Gregory Watson",current_score: 7>,#<Score player_name: "Jeremy Welch",#<Score player_name: "Sharon Oliver",#<Score player_name: "Donald Lewis",#<Score player_name: "Timothy Frazier",#<Score player_name: "John Richards",#<Score player_name: "Carolyn White",#<Score player_name: "Ronald Smith",#<Score player_name: "Emily Freeman",#<Score player_name: "Gregory Wright",current_score: 2>]

我如何计算出“唐纳德刘易斯”的排名？

解决方法

您可以计算具有更高current_score的记录数.您仍然必须按记录执行此操作(或在您的sql中执行子查询).

class Score < ActiveRecord::Base

  def ranking
    Score.count(:conditions => ['current_score > ?',self.current_score])
  end

end