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社区首页 >问答首页 >Active Model序列化程序-提高渲染性能

问Active Model序列化程序-提高渲染性能
EN

Stack Overflow用户
提问于 2016-08-30 01:30:42
回答 2查看 2.8K关注 0票数 17

我遇到了一种特殊的情况，ActiveModel::Serializer生成的渲染json非常慢(大约6-8秒)。如何提高渲染的速度？这是代码。

型号：

代码语言：javascript
复制
class Comment < ActiveRecord::Base
  has_many :children_comments,
           class_name: 'Comment',
           foreign_key: 'parent_comment_id'

  belongs_to :user
  belongs_to :parent_comment,
             class_name: 'Comment',
             foreign_key: 'parent_comment_id'
end

序列化程序：

代码语言：javascript
复制
class CommentSerializer < ActiveModel::Serializer
  include ActionView::Helpers::DateHelper

  attributes :id, :message, :created_at_in_words,
             :created_at, :parent_comment_id
  belongs_to :user
  has_many :children_comments

  def created_at_in_words
    time_ago_in_words(object.created_at) + ' ago'
  end

  def children_comments
    object.children_comments.map do |comment|
      CommentSerializer.new(comment).as_json
    end
  end
end

class UserSerializer < ActiveModel::Serializer
  attributes :id, :name, :avatar_url

  def avatar_url
    object.avatar.url
  end
end

在我的控制器里我有

代码语言：javascript
复制
  parent_comments = Comment.where(parent_comment_id: nil)

  render status: :ok,
         json: parent_comments,
         each_serializer: CommentSerializer,
         key_transform: :camel_lower

下面是我调用服务器时的部分日志输出。正如您所看到的，Active Model序列化程序进行每个查询调用大约需要20毫秒。

代码语言：javascript
复制
Started GET "/comments?lesson_id=420" for ::1 at 2016-09-01 11:09:14 -0400
Processing by Api::CommentsController#index as HTML
  Parameters: {"lesson_id"=>"420"}
  User Load (0.4ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1  ORDER BY "users"."id" ASC LIMIT 1  [["id", 102]]
  Lesson Load (0.5ms)  SELECT  "lessons".* FROM "lessons" WHERE "lessons"."id" = $1  ORDER BY position ASC LIMIT 1  [["id", 420]]
  Comment Load (53.0ms)  SELECT "comments".* FROM "comments" WHERE "comments"."commentable_id" = $1 AND "comments"."commentable_type" = $2 AND "comments"."parent_comment_id" IS NULL  [["commentable_id", 420], ["commentable_type", "Lesson"]]
[active_model_serializers]   User Load (0.5ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (24.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41401]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (20.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41402]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (22.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41403]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (21.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41404]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.4ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41405]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (20.5ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41406]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (20.4ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41407]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (20.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41408]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41409]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41410]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.2ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41411]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.4ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41412]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.8ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41413]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (23.5ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41414]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41415]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.4ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41416]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (23.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41417]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.5ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41418]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41419]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41420]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.4ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41421]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.9ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41422]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41423]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (20.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41424]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.8ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41425]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41426]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.2ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41427]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41428]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41429]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41430]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.9ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41431]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41432]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41433]]
[active_model_serializers]   CACHE (0.1ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (21.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41434]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.8ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41435]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (21.5ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41436]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.4ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41437]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.8ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41438]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (22.9ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41439]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41440]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.4ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41441]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.9ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41442]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.8ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41443]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41444]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.2ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41445]]
[active_model_serializers]   CACHE (0.1ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41446]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.5ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41447]]
[active_model_serializers]   CACHE (0.1ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.5ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41448]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41449]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.0ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41450]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.2ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41451]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41452]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.2ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41453]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.0ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41454]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (22.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41455]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (22.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41456]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41457]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41458]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.2ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41459]]
[active_model_serializers]   CACHE (0.1ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.5ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41460]]
[active_model_serializers]   CACHE (0.1ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (20.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41461]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41462]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41463]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41464]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (20.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41465]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41466]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.8ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41467]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.5ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41468]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41469]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41470]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.0ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41471]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (20.4ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41472]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.4ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41473]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.0ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41474]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41475]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41476]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (19.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41477]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41478]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.8ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41479]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (20.4ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41480]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.2ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41534]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41535]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.6ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41536]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.8ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41537]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (18.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 41538]]
[active_model_serializers] Rendered ActiveModel::Serializer::CollectionSerializer with ActiveModelSerializers::Adapter::Json (3895.33ms)
Completed 200 OK in 4007ms (Views: 1222.1ms | ActiveRecord: 2743.8ms)

根据Michal的回答，下面是日志中的一个小样本。

代码语言：javascript
复制
Started GET "/comments?lesson_id=370" for ::1 at 2016-09-02 17:13:06 -0400
Processing by Api::CommentsController#index as HTML
  Parameters: {"lesson_id"=>"370"}
  User Load (0.4ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1  ORDER BY "users"."id" ASC LIMIT 1  [["id", 102]]
  Lesson Load (0.4ms)  SELECT  "lessons".* FROM "lessons" WHERE "lessons"."id" = $1  ORDER BY position ASC LIMIT 1  [["id", 370]]
  Comment Load (23.0ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" IS NULL AND "comments"."commentable_type" = 'Lesson' AND "comments"."commentable_id" = 370
  User Load (0.9ms)  SELECT "users".* FROM "users" WHERE "users"."id" IN (102)
  Comment Load (25.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" IN (38641, 38687, 38733)
  CACHE (0.0ms)  SELECT "users".* FROM "users" WHERE "users"."id" IN (102)
[active_model_serializers]   Comment Load (20.3ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 38642]]
[active_model_serializers]   User Load (0.5ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (20.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 38643]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]
[active_model_serializers]   Comment Load (30.1ms)  SELECT "comments".* FROM "comments" WHERE "comments"."parent_comment_id" = $1  [["parent_comment_id", 38644]]
[active_model_serializers]   CACHE (0.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 102]]

我的理论是这样的。我确信children_comments序列化是导致大多数性能问题的原因。因为我必须为每个注释调用children_comments，所以这会产生级联效应。我想知道我是否可以用某种方式重写代码来提高性能。

ruby-on-rails
json
ruby-on-rails-4
serialization
active-model-serializers
EN

回答 2

Stack Overflow用户

发布于 2016-09-16 22:10:11

您遇到了n+1查询类型的问题。不幸的是，includes在这里并没有真正帮助你，因为它只帮助你一个级别的关联-它避免单独获取顶级注释的子项，而不是孙子项或曾孙项。

您可能可以通过维护自己的用户id到用户对象的缓存来优化用户查找( rails缓存缓存原始数据，但将一次又一次地重新实例化对象)，但要使这一过程更快，您需要更改加载注释的方式。

如果您使用的是支持递归查询的数据库(比如postgresql)，那么可以选择递归查询(参见https://hashrocket.com/blog/posts/recursive-sql-in-activerecord中的示例)。当树越来越深时，我不知道这个比例。

如果不能选择递归查询，那么有几种方法可以更改您存储的内容。

一种是物化路径模式。例如，假设根注释的id为1，一个子节点的id为101，它的一个子节点的id为426。最后一条评论的路径是1/101/426。它的所有同级都有以1/101/开头的路径。这意味着您可以使用like查询(末尾带有通配符)快速查找子树。ancestry gem实现了这一点。如果注释被移动，那么您需要重写所有注释子项(以及子项等)的路径，但这可能与您的用例无关。我认为非常深的树是有问题的。

另一种是嵌套的集合模式。其核心思想是父节点存储其所有子节点及其子节点的子节点的最小和最大id等。这允许一次性检索所有这些子节点。另一方面，插入和更新需要重写大量数据(比物化路径更需要重写)。多年来，已经有各种不同的gem实现了这一点(目前的一个似乎是awesome_nested_set)。

同样值得检查的是，你是否有正确的索引来支持你的查询--除非给定父对象的评论真的很多，20-30ms对于一个查询来说似乎是相当长的时间。

票数 9
EN

Stack Overflow用户

发布于 2016-09-02 04:54:19

将您的ActiveRecord查询更改为

代码语言：javascript
复制
parent_comments = Comment.where(parent_comment_id: nil).includes(:user, children_comments: :user)

它将摆脱N+1个查询。

票数 6
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/39211912

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