Question

我正在尝试在Rails 5.2.1中设置模型和片段缓存

我在Fragment缓存方面取得了成功，但是在为我的模型实施模型缓存之后，我仍然看到数据库查询。

我启用了开发缓存

$ rails dev:cache

模型助手

module LanguagesHelper
  def approved_languages
    Rails.cache.fetch("approved_languages") { Languages.is_active.is_approved }
  end
end

控制器

class LanguagesController < ApplicationController
  include LanguagesHelper

  def index
    @languages = approved_languages
  end
end

观看次数

app / views / languages / index.html.erb

<%= render partial: 'languages/language', collection: @languages, cached: true %>

app / views / languages / _language.html.erb

<% cache language do %>
  <%= language.name %>
<% end %>

控制台

Started GET "/languages" for 127.0.0.1 at 2018-08-21 14:13:29 -0400
Processing by LanguagesController#index as HTML
  Rendering languages/index.html.erb within layouts/application
  Language Load (1.2ms)  SELECT "languages".* FROM "languages" WHERE "languages"."deleted" = $1 AND "languages"."approved" = $2  [["deleted", false], ["approved", true]]
  ↳ app/views/languages/index.html.erb:4
  Rendered collection of languages/_language.html.erb [1 / 1 cache hits] (3.0ms)
  Rendered languages/index.html.erb within layouts/application (10.9ms)
Completed 200 OK in 50ms (Views: 46.2ms | ActiveRecord: 1.2ms)

为什么我仍然在每个请求中看到数据库查询？

Answer 1

这里似乎正在发生的事情是，您正在缓存关系之前，它会加载记录，因此仍然需要实际加载它们才能使用（使用我的广告模型）因为它在那里并且可以在irb中方便地进行测试）：

ads = Ad.all;nil # no query here, this is what I think you're caching
# this next line is where the query is run, (this would be
# equivalent to your render line)
ads.each { ... } 
#  Ad Load (0.1ms)  SELECT "ads".* FROM "ads"

相反，您可以在缓存它之前尝试强制活动记录加载该关系，看看是否有帮助。您可以使用load：

ads = Ad.all.load;nil # query is now run here
#  Ad Load (0.1ms)  SELECT "ads".* FROM "ads"
ads.each { ... } # and not run here

并启用了缓存（所有这些都在一个Rails控制台会话中，多个会话似乎忘记了以前的缓存，但是我尚未配置缓存，因此可能只是某种内存存储）

ads = Rails.cache.fetch("test load") { Ad.all.load };nil # query
#  Ad Load (0.9ms)  SELECT "ads".* FROM "ads"
ads = Rails.cache.fetch("test load") { Ad.all.load };nil # no query
ads.each {  } # no query
ads = Rails.cache.fetch("test without load") { Ad.all };nil # no query
ads.each { };nil # query
#  Ad Load (0.1ms)  SELECT "ads".* FROM "ads"
ads = Rails.cache.fetch("test without load") { Ad.all };nil # no query
ads.each { };nil # query
#  Ad Load (0.1ms)  SELECT "ads".* FROM "ads"

Answer 2

我之前已经关闭，但是现在已经成功实现了缓存。上面的答案是值得赞赏的，但不是我想要的，这是我当前的设置。

当我应该将其移至模型时，我正在Helper模块中调用语言模型查询。

模型

after_save :clear_cache
after_destroy :clear_cache

def clear_language_cache
  Rails.cache.delete('Language.active.approved')
end

def self.active_approved
  Rails.cache.fetch('Language.active.approved') { is_active.is_approved.order(created_at: :desc).to_a }
end

控制器

class LanguagesController < ApplicationController
  def index
    @languages = Language.active_approved
  end
end

控制台

Started GET "/languages" for 127.0.0.1 at 2018-08-22 18:13:21 -0400
Processing by LanguagesController#index as HTML
  Rendering languages/index.html.erb within layouts/application
  Rendered collection of languages/_language.html.erb [1 / 1 cache hits] (11.0ms)
  Rendered languages/index.html.erb within layouts/application (15.9ms)
Completed 200 OK in 68ms (Views: 45.5ms | ActiveRecord: 5.8ms)

Rails 5.2.1-模型和片段缓存

2 个答案: