Почему я получаю столько SQL вызовов за столом, что я не слишком много запрашиваю? - PullRequest
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Почему я получаю столько SQL вызовов за столом, что я не слишком много запрашиваю?

0 голосов
/ 07 марта 2020

Я заметил, что я получаю несколько SQL вызовов для моей таблицы editions, хотя я загружаю ее только один раз в контроллер. Что еще более странно для меня, так это то, что каждый вызов относится к разному edition, хотя я загружаю страницу show для одного издания.

Вывод консоли здесь: 

Started GET "/editions/48" for 127.0.0.1 at 2020-03-07 08:37:53 +0530
Processing by EditionsController#show as HTML
  Parameters: {"id"=>"48"}
  Edition Load (0.5ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 48], ["LIMIT", 1]]
  User Load (0.8ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 ORDER BY "users"."id" ASC LIMIT $2  [["id", 1], ["LIMIT", 1]]
  Rendering editions/show.html.erb within layouts/application
  Product Load (0.4ms)  SELECT  "products".* FROM "products" WHERE "products"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
  Rendered shared/_arrow.html.erb (0.3ms)
  Edition Load (0.6ms)  SELECT  "editions".* FROM "editions" WHERE (product_id = 1 AND date < '2018-02-18') ORDER BY "editions"."date" DESC LIMIT $1  [["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE (product_id = 1 AND date < '2018-02-18') ORDER BY "editions"."date" DESC LIMIT $1  [["LIMIT", 1]]
  Edition Load (0.5ms)  SELECT  "editions".* FROM "editions" WHERE (product_id = 1 AND date > '2018-02-18') ORDER BY "editions"."date" ASC LIMIT $1  [["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE (product_id = 1 AND date > '2018-02-18') ORDER BY "editions"."date" ASC LIMIT $1  [["LIMIT", 1]]
  Rendered editions/_admin_controls.html.erb (0.9ms)
  Section Load (0.8ms)  SELECT DISTINCT "sections".* FROM "sections" INNER JOIN "contents" "contents_sections" ON "contents_sections"."section_id" = "sections"."id" INNER JOIN "contents" ON "sections"."id" = "contents"."section_id" WHERE "contents"."edition_id" = $1 AND "contents"."top_story" = $2 ORDER BY "sections"."position" ASC  [["edition_id", 48], ["top_story", "f"]]
  Content Load (0.6ms)  SELECT "contents".* FROM "contents" WHERE "contents"."edition_id" = $1 AND "contents"."top_story" = $2  [["edition_id", 48], ["top_story", "t"]]
  Content Load (0.6ms)  SELECT "contents".* FROM "contents" WHERE "contents"."edition_id" = $1 AND "contents"."top_story" = $2 ORDER BY "contents"."position" ASC  [["edition_id", 48], ["top_story", "t"]]
  Rendered contents/_admin_controls.html.erb (0.5ms)
  Source Load (0.4ms)  SELECT  "sources".* FROM "sources" WHERE "sources"."id" = $1 LIMIT $2  [["id", 5], ["LIMIT", 1]]
  Rendered shared/_content.html.erb (7.0ms)
  Rendered contents/_admin_controls.html.erb (0.3ms)
  Source Load (0.4ms)  SELECT  "sources".* FROM "sources" WHERE "sources"."id" = $1 LIMIT $2  [["id", 2], ["LIMIT", 1]]
  Rendered shared/_content.html.erb (6.9ms)
  Rendered contents/_admin_controls.html.erb (0.3ms)
  CACHE Source Load (0.0ms)  SELECT  "sources".* FROM "sources" WHERE "sources"."id" = $1 LIMIT $2  [["id", 2], ["LIMIT", 1]]
  Rendered shared/_content.html.erb (7.9ms)
  Rendered contents/_admin_controls.html.erb (0.3ms)
  CACHE Source Load (0.0ms)  SELECT  "sources".* FROM "sources" WHERE "sources"."id" = $1 LIMIT $2  [["id", 2], ["LIMIT", 1]]
  Rendered shared/_content.html.erb (7.0ms)
  Content Load (0.6ms)  SELECT "contents".* FROM "contents" WHERE "contents"."section_id" = $1 ORDER BY "contents"."position" ASC  [["section_id", 2]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 40], ["LIMIT", 1]]
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 22], ["LIMIT", 1]]
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 14], ["LIMIT", 1]]
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 41], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 14], ["LIMIT", 1]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 4], ["LIMIT", 1]]
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 38], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 4], ["LIMIT", 1]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 34], ["LIMIT", 1]]
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 36], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 36], ["LIMIT", 1]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 2], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 2], ["LIMIT", 1]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 27], ["LIMIT", 1]]
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 48], ["LIMIT", 1]]
  Rendered contents/_admin_controls.html.erb (0.4ms)
  Source Load (0.4ms)  SELECT  "sources".* FROM "sources" WHERE "sources"."id" = $1 LIMIT $2  [["id", 4], ["LIMIT", 1]]
  Rendered shared/_content.html.erb (7.4ms)
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 24], ["LIMIT", 1]]
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 13], ["LIMIT", 1]]
  Edition Load (0.2ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 20], ["LIMIT", 1]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 37], ["LIMIT", 1]]
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 34], ["LIMIT", 1]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 23], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 24], ["LIMIT", 1]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 45], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 36], ["LIMIT", 1]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 3], ["LIMIT", 1]]
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 15], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 24], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 37], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 40], ["LIMIT", 1]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 47], ["LIMIT", 1]]
  CACHE Edition Load (0.0ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 14], ["LIMIT", 1]]
  Edition Load (0.4ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 10], ["LIMIT", 1]]
  Edition Load (0.3ms)  SELECT  "editions".* FROM "editions" WHERE "editions"."id" = $1 LIMIT $2  [["id", 29], ["LIMIT", 1]]
  Rendered editions/_edition_sections.html.erb (142.3ms)
  Rendered editions/show.html.erb within layouts/application (246.2ms)
  Rendered shared/_nav_searchbar.html.erb (0.8ms)
  Rendered shared/_nav.html.erb (4.1ms)
  Visit Load (0.5ms)  SELECT  "visits".* FROM "visits" WHERE "visits"."visit_token" = $1 ORDER BY "visits"."id" ASC LIMIT $2  [["visit_token", "40979cb1-0c92-486a-a274-c937560c03b1"], ["LIMIT", 1]]
   (0.2ms)  BEGIN
  Visit Load (0.3ms)  SELECT  "visits".* FROM "visits" WHERE "visits"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
  SQL (0.4ms)  INSERT INTO "ahoy_events" ("visit_id", "user_id", "name", "properties", "time") VALUES ($1, $2, $3, $4, $5) RETURNING "id"  [["visit_id", 1], ["user_id", 1], ["name", "Load edition"], ["properties", "{\"controller\":\"editions\",\"action\":\"show\",\"id\":\"48\"}"], ["time", "2020-03-07 03:07:53.513209"]]
   (0.9ms)  COMMIT
Completed 200 OK in 400ms (Views: 367.2ms | ActiveRecord: 16.8ms)

Остальную часть моего кода можно найти здесь

Мое лучшее предположение состоит в том, что некоторые логики c в представлении show создают больше запросов к базе данных, но я ' я не уверен, где или как это оптимизировать (я новичок в SQL вещи и Rails). На самом деле это стало большой проблемой на моей производственной площадке, из-за которой Heroku выдает ошибки, говоря: R14 - Memory Quota Exceeded

Любой совет?

1 Ответ

1 голос
/ 07 марта 2020

Это называется N + 1 Проблема .

В _editions_sections.html.erb у вас есть: 

if (content.edition == @edition) && (content.top_story == false)

, что это делает для каждого содержимого в l oop загружается edition для сравнения с @edition.

Вы можете решить это двумя способами:

  • 1 (не обычное решение) 

    if (content.edition_id == @edition.id) && (content.top_story == false)

    Это будет проверять только столбец edition_id и не загружать все поля в edition.

  • 2, использовать includes

    in edition.rb, сделать sections_with_regular_content похожим на это: 

    def sections_with_regular_content
  sections.includes(contents: :edition).where(contents: { top_story: false })
end

includes эффективно вычисляет все необходимые идентификаторы и загружает их в один запрос или через объединение.

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