计算字段的活动模型序列化程序缓存

Question

我正在尝试缓存一组项目，这是我的 AMS：

class ApplicationCategorySerializer < ActiveModel::Serializer

  cache({})
  cache key: 'application_category', expires_in: 3.days

  attributes :id
  attributes :name
  attributes :active
  attributes :group
  attributes :num_of_protocols

  belongs_to :group do |serializer|
    serializer.attributes[:group][:name]
  end


  def num_of_protocols
    ApplicationCategory.find(object.id).protocol_categories.count
  end
end

我的问题是，如果没有 :num_of_protocols 部分，生成响应需要快 10 倍，

当我查看日志时，我可以看到：

Started GET "/application_categories.json" for 127.0.0.1 at 2016-08-04 19:12:27 +0300
Processing by ApplicationCategoriesController#index as JSON
  ApplicationCategory Load (3.0ms)  SELECT "application_categories".* FROM "application_categories"
[active_model_serializers]   Group Load (1.0ms)  SELECT  "groups".* FROM "groups" WHERE "groups"."id" = ? LIMIT 1  [["id", 2066]]
[active_model_serializers]   ApplicationCategory Load (0.0ms)  SELECT  "application_categories".* FROM "application_categories" WHERE "application_categories"."id" = ? LIMIT 1  [["id", 1]]
[active_model_serializers]    (0.0ms)  SELECT COUNT(*) FROM "protocol_categories" INNER JOIN "application_categories_protocol_categories" ON "protocol_categories"."id" = "application_categories_protocol_categories"."protocol_category_id" WHERE "application_categories_protocol_categories"."application_category_id" = ?  [["application_category_id", 1]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "groups".* FROM "groups" WHERE "groups"."id" = ? LIMIT 1  [["id", 2066]]
[active_model_serializers]   ApplicationCategory Load (0.0ms)  SELECT  "application_categories".* FROM "application_categories" WHERE "application_categories"."id" = ? LIMIT 1  [["id", 2]]
[active_model_serializers]    (0.0ms)  SELECT COUNT(*) FROM "protocol_categories" INNER JOIN "application_categories_protocol_categories" ON "protocol_categories"."id" = "application_categories_protocol_categories"."protocol_category_id" WHERE "application_categories_protocol_categories"."application_category_id" = ?  [["application_category_id", 2]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "groups".* FROM "groups" WHERE "groups"."id" = ? LIMIT 1  [["id", 2066]]
...................... [many many more lines like those...]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "application_categories".* FROM "application_categories" WHERE "application_categories"."id" = ? LIMIT 1  [["id", 608]]
[active_model_serializers]   CACHE (0.0ms)  SELECT COUNT(*) FROM "protocol_categories" INNER JOIN "application_categories_protocol_categories" ON "protocol_categories"."id" = "application_categories_protocol_categories"."protocol_category_id" WHERE "application_categories_protocol_categories"."application_category_id" = ?  [["application_category_id", 608]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "application_categories".* FROM "application_categories" WHERE "application_categories"."id" = ? LIMIT 1  [["id", 609]]
[active_model_serializers]   CACHE (0.0ms)  SELECT COUNT(*) FROM "protocol_categories" INNER JOIN "application_categories_protocol_categories" ON "protocol_categories"."id" = "application_categories_protocol_categories"."protocol_category_id" WHERE "application_categories_protocol_categories"."application_category_id" = ?  [["application_category_id", 609]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "application_categories".* FROM "application_categories" WHERE "application_categories"."id" = ? LIMIT 1  [["id", 610]]
[active_model_serializers]   CACHE (0.0ms)  SELECT COUNT(*) FROM "protocol_categories" INNER JOIN "application_categories_protocol_categories" ON "protocol_categories"."id" = "application_categories_protocol_categories"."protocol_category_id" WHERE "application_categories_protocol_categories"."application_category_id" = ?  [["application_category_id", 610]]
[active_model_serializers] Rendered ActiveModel::Serializer::CollectionSerializer with ActiveModelSerializers::Adapter::Attributes (1521.15ms)

如何通过缓存获得更好的结果？ - 当我注释掉 cache 行时，我得到了 aprox。与他们相同的时间，当我删除 :num_of_protocols 时，我得到了相同的时间，并且没有缓存。

我配置错了什么？

Answer 1

你能做到吗？

def num_of_protocols
  object.protocol_categories.count
end

而且，序列化程序对我来说已经有一段时间了，但我认为你能够做到这一点......

def num_of_protocols
  protocol_categories.count
end

这是更好的 ruby​​（如果 protocal_categories 已经作为数组加载）

def num_of_protocols
  protocol_categories.size
end

而且，如果所有这些都有效，请确保在渲染到 json 之前实例化 @application_category 时包含协议类别和组。您执行的查询过多。