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我正在尝试在 Rails 5.2.1 中设置模型和片段缓存

我在片段缓存方面取得了成功，但在为我的模型实现模型缓存后，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

意见

应用程序/视图/语言/index.html.erb

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

应用程序/视图/语言/_language.html.erb

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

安慰

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)

为什么我仍然看到每个请求的数据库查询？

4

2 回答 2

2

这里似乎发生的是，您在加载记录之前缓存了关系，因此它仍然必须在使用之前实际加载它们（使用我的 Ad 模型，因为它在那里并且便于在 irb 中进行测试） ：

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，您可以尝试在缓存之前强制活动记录加载关系，看看是否有帮助。您可以使用以下方法执行此操作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

并启用缓存（全部在单个 Rails 控制台会话中，多个会话似乎忘记了之前的缓存，但我没有配置缓存，所以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"
于 2018-08-21T19:17:03.287 回答
0

我以前很接近，但现在已经成功实现了缓存。上面的答案很受欢迎，但不是我想要的，这是我目前的设置。

当我应该将语言模型查询移至模型时，我在 Helper 模块中调用它。

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

安慰

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)
于 2018-08-22T22:17:07.930 回答