Caching associations in rails

Transcript

1. AssociationͷΩϟογϡ͸

   ӡ༻ʹؾΛ͚ͭͯ
   (Otemachirb#20)
   גࣜձࣾπΫϧόɹαʔόαΠυΤϯδχΞ
   ງ઒ɹ@CASIXx1
   
   
   

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2. • ීஈ͸ʮcowcamoʯͱ͍͏ΞϓϦΛ։ൃͯ͠
   ·͢
   • αʔόαΠυ͸ɺRailsʢ5.2ʣΛ࢖ͬͯ·͢
   
   
   

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3. 
   
   

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4. ISUCON͍ۙͰ͢Ͷ
   
   
   

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5. ISUCONͷաڈ໰

   ΍ͬͯΔͷͰ͕͢
   
   
   

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6. N + 1໰୊͸

   ఆ൪Ͱ͢ΑͶɻɻɻ
   
   
   

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7. 
   
   

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8. ෮शʣN + 1ͱ͸ʁ
   
   
   

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9. ҎԼͷϞσϧ͕͋ͬͨ৔߹
   
   
   app/models/user.rb
   class User < ApplicationRecord
   has_many :memos
   end
   app/models/memo.rb
   class Memo < ApplicationRecord
   belongs_to :user
   end
   

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10. ͜ΕΛ࣮ߦ͢Δͱ…
    
    
    @memos = Memo.all
    @memos.each do |memo|
    memo.id
    memo.user.name
    end
    

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11. 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
    
    
    

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12. Rails࢖ͬͯΔͱɺ

    N + 1Λ؆୯ʹղফͰ͖·͢ΑͶ
    
    
    

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13. includes, preload, eager_load
    Λ࢖͑͹ྑ͍
    
    
    @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
    

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14. includesͱ͔eager_loadͱ͔
    ৭ʑ͋Γ·͢ΑͶ
    
    
    

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15. N + 1ΛղܾͰ͖Δ͔൱͔
    • N + 1ΛղܾͰ͖ͳ͍
    • joins
    • N + 1ΛղܾͰ͖Δʢؔ࿈ςʔϒϧ৘ใΛؚΊͯΩϟογϡ͢Δʣ
    • eager_load
    • LEFT OUTER JOINΛར༻͢Δʢt0_r0Έ͍ͨͳ΍ͭʣ
    • preload
    • IN۟Λར༻ͯ͠ɺෳ਺ΫΤϦͰऔͬͯ͘Δ
    • whereͰؔ࿈ςʔϒϧͷ৘ใΛߜΕͳ͍
    • includes
    • eager_load, preloadΛঢ়گʹԠͯ͡ɺ࢖͍෼͚͢Δ
    
    
    

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16. AssociationͷΩϟογϡ͸

    ສೳ͔??
    
    
    

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17. ύϑΥʔϚϯεతʹ

    ؾΛ͚ͭͳ͚Ε͹ͳΒͳ͍࿩΋͋ΔΒ͍͕͠…
    
    
    

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18. ӡ༻໘Ͱ΋ؾΛ͚ͭͳ͍ͱ͍͚ͳ͍ʂ
    
    
    

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19. ؔ࿈ઌςʔϒϧͷΧϥϜΛ

    ࡟আ͍ͨ͠ͱ͢Δ
    • UserςʔϒϧͰɺ࡟আ͍ͨ͠ΧϥϜ͕͋Δͱ͢Δ
    • Ծʹɺ deprecated_columnͱ͍͏໊લʹ͠·͢
    • Α͠ʂΧϥϜ࡟আ͢Δ

    ϚΠάϨʔγϣϯΛ͔͚Α͏ʂ
    • ͔͠͠ɺΤϥʔ͕ग़ͯ͠·͍·ͨ͠ɻ

    ԿނͰ͠ΐ͏ʁʁ
    
    
    

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20. ؔ࿈ઌςʔϒϧͷΧϥϜΛ࡟আ
    ͍ͨ͠ͱ͢Δ
    • લఏ৚݅
    • ↓ͷίʔυ͕ଘࡏ͢Δ
    • ΞϓϦέʔγϣϯίʔυ͔Βɺ 

    deprecated_columnΛࢀর͠ͳ͍Α͏ʹमਖ਼ࡁΈ
    
    
    @memos = Memo.includes(:user).where(users: { name: ‘horikawa’ })
    @memos.each do |memo|
    memo.id
    memo.user.name
    end
    

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21. ౴͑
    • ؔ࿈ςʔϒϧͷΩϟογϡΛऔಘ͢Δࡍʹɺ

    શͯͷΧϥϜ৘ใΛSELECTจͰࢦఆͨ͠ΫΤϦΛൃߦ͠Α͏ͱ͢Δ
    (SELECT … `users`.`id` AS t1_r0, `users`.`deprecated_column` AS
    t1_r1)

    ↓
    • ϚΠάϨʔγϣϯͰɺΧϥϜΛ࡟আ͢Δ

    ˣ
    • ΫΤϦΛ࣮ߦ͢ΔࡍʹɺΩϟογϡΛ࢖͏ͷͰɺ

    ଘࡏ͠ͳ͍ΧϥϜʹର͢ΔΞΫηεΛͯ͠ɺΤϥʔ͕ग़Δ
    
    
    

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22. ౴͑
    
    
    # whereͰ৚݅෼ذ͢Δͱɺleft outer joinͰΩϟογϡΛੜ੒͢Δ
    @memos = Memo.includes(:user).where(users: { name: ‘horikawa’ })
    # ॲཧ͕͜͜Βลʹ͍ΔλΠϛϯάͰɺΧϥϜΛ࡟আ͞Εͯ͠·͏ͱ…
    # memo.deprecated_column͕ͳ͍ͱΤϥʔ͕ग़Δ
    @memos.each do |memo|
    memo.id
    memo.user.name
    end
    

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23. ରࡦ
    
    
    

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24. Rails 5.xͰ͋Ε͹
    • ignored_columnsΛ࢖͓͏ʂ
    • εΩʔϚ৘ใʹՃ͑ͳ͍Α͏ʹͯ͘͠ΕΔ
    • User.column_namesͰ

    deprecated_column͕ग़ͳ͚Ε͹͓k
    
    
    class User < ApplicationRecord
    self.ignored_columns = %w(deprecated_column)
    end
    

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25. ਖ਼͍͠σϓϩΠॱ
    • deprecated_columnΛࢀর͢ΔίʔυΛ࡟আ͢
    Δ

    ˣ
    • ignored_columnʹdeprecated_columnΛ௥Ճ

    ˣ
    • ΧϥϜΛ࡟আ
    
    
    

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26. ͪͳΈʹRails 4.xͰ͋Ε͹
    • ActiveRecord::Base.columnsΛΦʔόʔϥΠ
    υͯ͠ɺ

    deprecated_columnΛreject͢Δඞཁ͕͋Δ
    Έ͍ͨͰ͢
    
    
    

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27. Rails ্͛Α͏
    
    
    

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28. 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
    
    
    

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