Rails：將這些請求轉換為counter_cache的最佳方法

Question

每個頁面加載時我都有幾個這樣的請求：

SELECT COUNT(*) FROM `impressions` WHERE `impressions`.`impressionable_id` IN (229) AND `impressions`.`impressionable_type` = 'Document' AND (YEAR(created_at) = 2013 && MONTH(created_at) = 8 && DAY(created_at) = 12)
SELECT COUNT(*) FROM `impressions` WHERE `impressions`.`impressionable_id` IN (229) AND `impressions`.`impressionable_type` = 'Document' AND (YEAR(created_at) = 2013 && MONTH(created_at) = 8 && DAY(created_at) = 13)
SELECT COUNT(*) FROM `impressions` WHERE `impressions`.`impressionable_id` IN (229) AND `impressions`.`impressionable_type` = 'Document' AND (YEAR(created_at) = 2013 && MONTH(created_at) = 8 && DAY(created_at) = 14)
SELECT COUNT(*) FROM `impressions` WHERE `impressions`.`impressionable_id` IN (229) AND `impressions`.`impressionable_type` = 'Document' AND (YEAR(created_at) = 2013 && MONTH(created_at) = 8 && DAY(created_at) = 15)

我想減少服務器上的負載，所以我試圖將其變成counter_cache解決方案。 由於我要計算的復雜關系，我需要一些幫助來設計它。 這是獲取計數的查詢：

Impression.where(:impressionable_id => component.publications.where(:document_id => document).first.id).count

我應該在哪里放置counter_cache列？ 我應該如何編寫遷移？ Component和Document通過Publications具有has_many關系。

Answer 1

假設印象數是Publication ，並且印象數將按天分組。

您可以創建PublicationImpression模型作為每天每個Publication的印象的計數器。

class CreatePublicationImpressions < ActiveRecord::Migration
  def self.up
    create_table :publication_impressions, :id => false do |t|
      t.integer :impressions, :default => 0
      t.datetime :date
      t.references :publication

      t.timestamps
    end
  end

  def self.down
    drop_table :publication_impressions
  end
end