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减少铁路数据库的碰撞
原标题：Reducing database hits in Rails

我有两个模型:<代码>项目和 www.un.org/spanish/ecosoc (言辞实际上只是一个模式,每个项目每天写上字数。)

我认为,我也这样做,这表明该项目从一开始至尾都有几天时间,以及当天写过多少字。

<% project_range(@project.start, @project.end).each do |day| %>
    <%= day %>
    <%= get_word_count_by_date(@project, day ) %>
<% end %>

我的帮助者:

def project_range(start, finish)
  project_days = (start..finish).collect
end

def get_word_count_by_date(project, date)
  word_count = Word.find_by_project_id_and_wrote_on(project, date)
  if word_count
    word_count.quantity
  else
    0
  end
end

据认为,这可打到我的数据库。 例如,如果该项目为30天,我可以:

  Word Load (0.2ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-01  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-02  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-03  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-04  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-05  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-06  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-07  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-08  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-09  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-10  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-11  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-12  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-13  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-14  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-15  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-16  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-17  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-18  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-19  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-20  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-21  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-22  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-23  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-24  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-25  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-26  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-27  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-28  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-29  LIMIT 1
  Word Load (0.1ms)  SELECT "words".* FROM "words" WHERE "words"."project_id" = 2 AND "words"."wrote_on" =  2011-09-30  LIMIT 1

如果没有在项目时间上每一天提出询问,是否有办法这样做? 首先,我试图把项目的所有字装上一字,但无法说明如何用零用一天。

最佳回答

您可以利用一个助手来保持清扫,避免发现:

def project_range(project, start, finish, &blk)
  words = project.words.where(:wrote_on => start..finish)
  word_map = words.index_by(&:wrote_on)
  for day in start..finish
    word_count = word_map[day] ? word_map[day].quantity : 0
    blk.call(day, word_count)
  end
end

然后使用它。

<% project_range(project, start, finish) do |day, word_count| %>
   <%= day %>
   <%= word_count %>
<% end %>

您也可通过预先排定的口号清单或使用<条码>> 镜子/代码对助手进行清理。

EDIT: m_x建议start.finish where Clause on wrote_on 更清洁!

时间：2011-09-05 15:26:49
问题回答

This is a "n+1" problem... What you want to do is join words and projects in your query so that all the words for each project are included in the result set.

Assuming that your project "has_many :words":

@project = Project.find(:id, :include => :words)

现在,每个项目的文字收集将预先用在1个问题中的字句。

Read more under the "Eager Loading of Associations" http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

时间：2011-09-05 15:24:53

我只想说:

@words = @project.words.where("wrote_on >= ? and wrote_on <= ?", start, end)

http://api.rubyonrails.org/classes/Evidable.html#method-i-group_by”rel=“nofollow” a. 显示:

@words.group_by(&:wrote_on).each do |day, word|
<%= day %>
<%= word.quantity %>
end
时间：2011-09-05 15:28:14


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