Slide 1
Slide 1 text
AssociationͷΩϟογϡ
ӡ༻ʹؾΛ͚ͭͯ
(Otemachirb#20)
גࣜձࣾπΫϧόɹαʔόαΠυΤϯδχΞ
ງɹ@CASIXx1
Slide 2
Slide 2 text
• ීஈʮcowcamoʯͱ͍͏ΞϓϦΛ։ൃͯ͠
·͢
• αʔόαΠυɺRailsʢ5.2ʣΛͬͯ·͢
Slide 3
Slide 3 text
Slide 4
Slide 4 text
ISUCON͍ۙͰ͢Ͷ
Slide 5
Slide 5 text
ISUCONͷաڈ
ͬͯΔͷͰ͕͢
Slide 6
Slide 6 text
N + 1
ఆ൪Ͱ͢ΑͶɻɻɻ
Slide 7
Slide 7 text
Slide 8
Slide 8 text
෮शʣN + 1ͱʁ
Slide 9
Slide 9 text
ҎԼͷϞσϧ͕͋ͬͨ߹
app/models/user.rb
class User < ApplicationRecord
has_many :memos
end
app/models/memo.rb
class Memo < ApplicationRecord
belongs_to :user
end
Slide 10
Slide 10 text
͜ΕΛ࣮ߦ͢Δͱ…
@memos = Memo.all
@memos.each do |memo|
memo.id
memo.user.name
end
Slide 11
Slide 11 text
N + 1͕ൃੜ͢Δ
N(memo.userͷ) +
1(Memo.allͷΞΫηε)
SELECT 'memos'.* FROM 'memos' # Memo.allͷΞΫηε
# memo.user.nameͷΞΫηε
SELECT 'users'.* FROM 'users' WHERE 'users'.'id' = 1 LIMIT 1
SELECT 'users'.* FROM 'users' WHERE 'users'.'id' = 2 LIMIT 1
SELECT 'users'.* FROM 'users' WHERE 'users'.'id' = 3 LIMIT 1
Slide 12
Slide 12 text
RailsͬͯΔͱɺ
N + 1Λ؆୯ʹղফͰ͖·͢ΑͶ
Slide 13
Slide 13 text
includes, preload, eager_load
Λ͑ྑ͍
@memos = Memo.all.includes(:user)
@memos.each do |memo|
memo.id
memo.user.name
end
SELECT 'memo'.* FROM 'memos'
SELECT 'users'.* FROM 'users' WHERE 'users'.'id' IN (1, 2, 3)
N + 1→1 + 1ʹͳΔ
Slide 14
Slide 14 text
includesͱ͔eager_loadͱ͔
৭ʑ͋Γ·͢ΑͶ
Slide 15
Slide 15 text
N + 1ΛղܾͰ͖Δ͔൱͔
• N + 1ΛղܾͰ͖ͳ͍
• joins
• N + 1ΛղܾͰ͖Δʢؔ࿈ςʔϒϧใΛؚΊͯΩϟογϡ͢Δʣ
• eager_load
• LEFT OUTER JOINΛར༻͢Δʢt0_r0Έ͍ͨͳͭʣ
• preload
• IN۟Λར༻ͯ͠ɺෳΫΤϦͰऔͬͯ͘Δ
• whereͰؔ࿈ςʔϒϧͷใΛߜΕͳ͍
• includes
• eager_load, preloadΛঢ়گʹԠͯ͡ɺ͍͚͢Δ
Slide 16
Slide 16 text
AssociationͷΩϟογϡ
ສೳ͔??
Slide 17
Slide 17 text
ύϑΥʔϚϯεతʹ
ؾΛ͚ͭͳ͚ΕͳΒͳ͍͋ΔΒ͍͕͠…
Slide 18
Slide 18 text
ӡ༻໘ͰؾΛ͚ͭͳ͍ͱ͍͚ͳ͍ʂ
Slide 19
Slide 19 text
ؔ࿈ઌςʔϒϧͷΧϥϜΛ
আ͍ͨ͠ͱ͢Δ
• UserςʔϒϧͰɺআ͍ͨ͠ΧϥϜ͕͋Δͱ͢Δ
• Ծʹɺ deprecated_columnͱ͍͏໊લʹ͠·͢
• Α͠ʂΧϥϜআ͢Δ
ϚΠάϨʔγϣϯΛ͔͚Α͏ʂ
• ͔͠͠ɺΤϥʔ͕ग़ͯ͠·͍·ͨ͠ɻ
ԿނͰ͠ΐ͏ʁʁ
Slide 20
Slide 20 text
ؔ࿈ઌςʔϒϧͷΧϥϜΛআ
͍ͨ͠ͱ͢Δ
• લఏ݅
• ↓ͷίʔυ͕ଘࡏ͢Δ
• ΞϓϦέʔγϣϯίʔυ͔Βɺ
deprecated_columnΛࢀর͠ͳ͍Α͏ʹमਖ਼ࡁΈ
@memos = Memo.includes(:user).where(users: { name: ‘horikawa’ })
@memos.each do |memo|
memo.id
memo.user.name
end
Slide 21
Slide 21 text
͑
• ؔ࿈ςʔϒϧͷΩϟογϡΛऔಘ͢Δࡍʹɺ
શͯͷΧϥϜใΛSELECTจͰࢦఆͨ͠ΫΤϦΛൃߦ͠Α͏ͱ͢Δ
(SELECT … `users`.`id` AS t1_r0, `users`.`deprecated_column` AS
t1_r1)
↓
• ϚΠάϨʔγϣϯͰɺΧϥϜΛআ͢Δ
ˣ
• ΫΤϦΛ࣮ߦ͢ΔࡍʹɺΩϟογϡΛ͏ͷͰɺ
ଘࡏ͠ͳ͍ΧϥϜʹର͢ΔΞΫηεΛͯ͠ɺΤϥʔ͕ग़Δ
Slide 22
Slide 22 text
͑
# whereͰ݅ذ͢Δͱɺleft outer joinͰΩϟογϡΛੜ͢Δ
@memos = Memo.includes(:user).where(users: { name: ‘horikawa’ })
# ॲཧ͕͜͜Βลʹ͍ΔλΠϛϯάͰɺΧϥϜΛআ͞Εͯ͠·͏ͱ…
# memo.deprecated_column͕ͳ͍ͱΤϥʔ͕ग़Δ
@memos.each do |memo|
memo.id
memo.user.name
end
Slide 23
Slide 23 text
ରࡦ
Slide 24
Slide 24 text
Rails 5.xͰ͋Ε
• ignored_columnsΛ͓͏ʂ
• εΩʔϚใʹՃ͑ͳ͍Α͏ʹͯ͘͠ΕΔ
• User.column_namesͰ
deprecated_column͕ग़ͳ͚Ε͓k
class User < ApplicationRecord
self.ignored_columns = %w(deprecated_column)
end
Slide 25
Slide 25 text
ਖ਼͍͠σϓϩΠॱ
• deprecated_columnΛࢀর͢ΔίʔυΛআ͢
Δ
ˣ
• ignored_columnʹdeprecated_columnΛՃ
ˣ
• ΧϥϜΛআ
Slide 26
Slide 26 text
ͪͳΈʹRails 4.xͰ͋Ε
• ActiveRecord::Base.columnsΛΦʔόʔϥΠ
υͯ͠ɺ
deprecated_columnΛreject͢Δඞཁ͕͋Δ
Έ͍ͨͰ͢
Slide 27
Slide 27 text
Rails ্͛Α͏
Slide 28
Slide 28 text
ࢀߟ
• https://moneyforward.com/engineers_blog/2019/04/02/
activerecord-includes-preload-eagerload/
• https://dev.classmethod.jp/server-side/activerecord-join/
• https://qiita.com/ykamez/items/0c81a33ec1b90219d541
• https://qiita.com/SoarTec-lab/items/
a192d381323cb741538e
• https://eagletmt.hateblo.jp/entry/2017/09/24/004709