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実行計画から学ぶ PostgreSQL の内部動作とクエリ最適化 / Learn PostgreSQL from Explain

実行計画から学ぶ PostgreSQL の内部動作とクエリ最適化 / Learn PostgreSQL from Explain

2019年 Wantedly 新人研修の資料です。

SQL に対する Explain 結果をベースに、SQL 実行時の PostgreSQL の内部動作や、それを踏まえた上でのクエリ最適化について話しました。

Nao Minami

May 15, 2019
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  1. ©2019 Wantedly, Inc. ࣮ߦܭը͔ΒֶͿ 1PTUHSF42-ͷ಺෦ಈ࡞ͱ ΫΤϦ࠷దԽ 15.May.2019 - Nao Minami

    (@south37) Wantedly, Inc. New Joiner Training 2019
  2. ©2019 Wantedly, Inc. ͸͡Ίʹ

  3. ©2019 Wantedly, Inc. 42-ͷ࣮ߦ࣌ʹ3%#ͰߦΘΕΔ಺෦ಈ࡞Λ஌Δ &YQMBJOͷಡΈํɺద੾ͳJOEFYͷઃఆΛ஌Δ ࠓ೔ͷΰʔϧ

  4. ©2019 Wantedly, Inc. ࠓ೔ѻ͏ςʔϒϧͷεΩʔϚ Table "jobs" Column | Type |

    Collation | Nullable | Default -------------+------------+-----------+----------+--------------------------------- id | bigint | | not null | nextval('jobs_id_seq'::regclass) company_id | integer | | | Indexes: "jobs_pkey" PRIMARY KEY, btree (id) "index_jobs_on_company_id" btree (company_id) Table "companies" Column | Type | Collation | Nullable | Default -------------+----------------------+-----------+----------+-------------------------------- id | bigint | | not null | nextval('jobs_id_seq'::regclass) country | character varying(2) | | not null | 'JP'::character varying Indexes: "companies_pkey" PRIMARY KEY, btree (id) "index_companies_on_country" btree (country)
  5. ©2019 Wantedly, Inc. ࠓ೔಺෦ಈ࡞Λཧղ͢Δ42- SELECT companies.country, COUNT(jobs.id) FROM jobs INNER

    JOIN companies ON companies.id = jobs.company_id WHERE companies.id < 1000 GROUP BY companies.country
  6. ©2019 Wantedly, Inc. ·ͣ͸42-Λ&YQMBJOͯ͠ΈΑ͏

  7. ©2019 Wantedly, Inc. EXPLAIN SELECT companies.country, COUNT(jobs.id) FROM jobs INNER

    JOIN companies ON companies.id = jobs.company_id WHERE companies.id < 1000 GROUP BY companies.country 1PTUHSF42-ͷ&YQMBJO
  8. ©2019 Wantedly, Inc. 1PTUHSF42-ͷ&YQMBJO݁ՌΛݟͯΈΔ QUERY PLAN ------------------------------------------------------------------------------------------------------ HashAggregate (cost=1213.79..1220.12 rows=634

    width=16) -> Hash Join (cost=54.28..1188.79 rows=5000 width=16) Hash Cond: (jobs.company_id = companies.id) -> Seq Scan on jobs (cost=0.00..897.00 rows=50000 width=8) -> Hash (cost=41.78..41.78 rows=1000 width=16) -> Index Scan using companies_pkey on companies (cost=0.29..41.78 rows=1000 width=16) Index Cond: (id < 1000) ࣮ߦܭը͸πϦʔߏ଄ )BTI"HHSFHBUF )BTI+PJO 4FR4DBO )BTI *OEFY4DBO
  9. ©2019 Wantedly, Inc. ίετͷݟํ Seq Scan on jobs (cost=0.00..897.00 rows=50000

    width=8) ॳظԽίετ ૯ίετ Ϩίʔυ਺ Ϩίʔυ͋ͨΓͷσʔλαΠζ όΠτ ૯ίετॳظԽίετ   Ϩίʔυ਺ʷϨίʔυ͋ͨΓͷऔಘίετ
  10. ©2019 Wantedly, Inc. ༨ஊ&91-"*/"/"-:4&ͩͱ࣮ࡍʹ࣮ߦ EXPLAIN ANALYSE SELECT companies.country, COUNT(jobs.id) FROM

    jobs INNER JOIN companies ON companies.id = jobs.company_id WHERE companies.id < 1000 GROUP BY companies.country
  11. ©2019 Wantedly, Inc. ༨ஊ&91-"*/"/"-:4&ͩͱ࣮ࡍʹ࣮ߦ HashAggregate (cost=1213.79..1220.12 rows=634 width=16) (actual time=20.290..20.465

    rows=950 loops=1) -> Hash Join (cost=54.28..1188.79 rows=5000 width=16) (actual time=1.018..18.102 rows=4983 loops=1) Hash Cond:(jobs.company_id = companies.id) -> Seq Scan on jobs (cost=0.00..897.00 rows=50000 width=8) (actual time=0.009..6.352 rows=50000 loops=1) -> Hash (cost=41.78..41.78 rows=1000 width=16) (actual time=0.995..0.995 rows=999 loops=1) Buckets: 1024 Batches: 1 Memory Usage: 51kB -> Index Scan using companies_pkey on companies (cost=0.29..41.78 rows=1000 width=16) (actual time=0.022..0.527 rows=999 loops=1)
  12. ©2019 Wantedly, Inc. &91-"*/ʹ͍ͭͯ IUUQXXXQPTUHSFTRMPSHEPDTDVSSFOUTUBUJDTRMFYQMBJOIUNM ΑΓৄ͘͠஌Γ͍ͨํ͸ެࣜυΩϡϝϯτΛࢀর

  13. ©2019 Wantedly, Inc. 42-࣮ߦͷ'JSTU4UFQσʔλऔಘ

  14. ©2019 Wantedly, Inc. 42-࣮ߦͷ'JSTU4UFQσʔλऔಘ QUERY PLAN ------------------------------------------------------------------------------------------------------ HashAggregate (cost=1213.79..1220.12 rows=634

    width=16) -> Hash Join (cost=54.28..1188.79 rows=5000 width=16) Hash Cond: (jobs.company_id = companies.id) -> Seq Scan on jobs (cost=0.00..897.00 rows=50000 width=8) -> Hash (cost=41.78..41.78 rows=1000 width=16) -> Index Scan using companies_pkey on companies (cost=0.29..41.78 rows=1000 width=16) Index Cond: (id < 1000) )BTI"HHSFHBUF )BTI+PJO 4FR4DBO )BTI *OEFY4DBO
  15. ©2019 Wantedly, Inc. *OEFY4DBOJOEFYΛར༻ͨ͠σʔλऔಘ )BTI"HHSFHBUF )BTI+PJO 4FR4DBO )BTI *OEFY4DBO ·ͣ͸JOEFY4DBOʹ஫໨͢Δ

  16. ©2019 Wantedly, Inc. *OEFYͷ࢓૊Έ #USFFJOEFY w ϊʔυ͋ͨΓ਺ඦཁૉ w ཁૉͱͯ͠ɺஈͰສ݅֨ೲ ߴ଎ͳσʔλऔಘ

    IUUQTXXXWFSUBCFMPDPNCMPHUFDIOJDBMBSUJDMFTBMMBCPVUJOEFYFTQBSUNZTRMJOEFYTUSVDUVSFBOEQFSGPSNBODF ΑΓҾ༻
  17. ©2019 Wantedly, Inc. *OEFYͷར༻ʹΑΔߴ଎Խ EXPLAIN SELECT jobs.* FROM jobs WHERE

    jobs.id = 1 QUERY PLAN ----------------------------------------------------------------------- Index Scan using jobs_pkey on jobs (cost=0.29..8.31 rows=1 width=28) Index Cond: (id = 1) JOEFY͋Γ EXPLAIN SELECT jobs.* FROM jobs WHERE jobs.id = 1 QUERY PLAN ----------------------------------------------------------------------- Seq Scan on jobs (cost=0.00..1022.00 rows=1 width=28) Filter: (id = 1) JOEFYແ͠ JOEFYʹΑͬͯίετΛ཈͑Δࣄ͕Ͱ͖Δ
  18. ©2019 Wantedly, Inc. ҰํɺJOEFYͷར༻ʹ͸ؾΛ͚ͭΔϙΠϯτ΋͋Δ

  19. ©2019 Wantedly, Inc. *OEFYόουύλʔϯJOEFYΛ࡞੒ͨ͠ΧϥϜʹԋࢉ EXPLAIN SELECT profiles.* FROM profiles WHERE

    (lower(email) = '[email protected]') LIMIT 1 QUERY PLAN ----------------------------------------------------------------------- Limit (cost=0.00..5.08 rows=1 width=54) -> Seq Scan on profiles (cost=0.00..254.00 rows=50 width=54) Filter: (lower(email) = '[email protected]'::text) #USFFJOEFY͸LFZͷൺֱͰTPSUͯ͠ΔͷͰɺԋࢉ͕ߦΘΕΔͱར༻Ͱ͖ͳ͍ ʮΫΤϦॻ͖׵͑ʯPSʮ*OEFYFTPO&YQSFTTJPOΛར༻ʯ
  20. ©2019 Wantedly, Inc. *OEFYόουύλʔϯߜΓࠐΈ৚݅ͷΏΔ͍8)&3& EXPLAIN SELECT profiles.* FROM profiles WHERE

    profiles.gender = “female” QUERY PLAN ----------------------------------------------------------------------- Seq Scan on profiles (cost=0.00..229.00 rows=5038 width=54) Filter: (gender = 'female'::text) QSPpMFTHFOEFSͷ෼෍͕ҎԼͩͱɺ*OEFY͸ར༻͞Εͳ͍ σϑΥϧτͩͱɺ෼ͷҎԼʹߜΓࠐ·ΕΔඞཁ͋Γ male female
  21. ©2019 Wantedly, Inc. )%%΁ͷϥϯμ ϜΞΫηεͱ γʔέϯγϟϧΞΫηεͷ଎౓͕ࠩݪҼ 4FR4DBO *OEFY4DBO 3BOEPN"DDFTT 

      ̐     ཁૉ୯Ґͩͱߴίετ ͳͥߜΓࠐΈ৚͕݅؇͍ͱJOEFY͕࢖ΘΕͳ͍ͷ͔ʁ
  22. ©2019 Wantedly, Inc. EXPLAIN SELECT profiles.* FROM profiles WHERE profiles.gender

    = “female” QUERY PLAN ----------------------------------------------------------------------- Bitmap Heap Scan on boxer_profiles (cost=28.08..114.66 rows=1006 width=25) Recheck Cond: (gender = ‘female'::text) -> Bitmap Index Scan on index_boxer_profiles_on_gender (cost=0.00..27.83 rows=1006 width=0) Index Cond: (gender = 'female'::text) QSPpMFTHFOEFSͷ෼෍͕ҎԼͳΒɺ*OEFY͸ར༻͞ΕΔ male female ϕετϓϥΫςΟε8)&3&ͰͪΌΜͱߜΓࠐ·ΕΔΑ͏ʹ͢Δ σʔλͷ෼෍ʮ౷ܭ৘ใʯ͕େࣄ
  23. ©2019 Wantedly, Inc. ༨ஊ1PTUHSF42-಺ͰͷσʔλϨΠΞ΢τ ৄ͘͠஌Γ͍ͨํ͸ IUUQXXXQPTUHSFTRMPSHEPDTDVSSFOUTUBUJDTUPSBHFIUNM ·ͨ͸ʮ಺෦ߏ଄͔ΒֶͿ1PTUHSF42-ઃܭɾӡ༻ܭըͷమଇʯΛࢀর ʮ಺෦ߏ଄͔ΒֶͿ1PTUHSF42-ઃܭɾӡ༻ܭըͷమଇ  ٕज़ධ࿦ࣾʯΑΓҾ༻

  24. ©2019 Wantedly, Inc. *OEFYʹ͸σϝϦοτ΋͋ΔࣄΛ஌Δ #USFFJOEFYߋ৽ʹίετ͕͔͔Δ w Ϩίʔυͷߋ৽ʹ͕͔͔࣌ؒΔΑ͏ʹͳΔ w %#ͷ࢖༻͢ΔσʔλαΠζ͕૿͑Δ )05͕ޮ͔ͳ͍

    w )05͸1PTUHSF42-ͷΧϥϜͷߋ৽Λૣ͘͢Δ࢓૊ΈʢඞཁͳՕॴͷΈΛߋ৽͢Δʣ w ৄ͘͠͸IUUQMFUTQPTUHSFTRMKQEPDVNFOUTUVUPSJBM[email protected]ࢀর
  25. ©2019 Wantedly, Inc. 1PTUHSF42-ʹ͸༷ʑͳ*OEFY͕͋Δ  6OJRVF*OEFY  .VMUJDPMVNO*OEFY  *OEFYFTPO&YQSFTTJPOT

     1BSUJBM*OEFYFT
  26. ©2019 Wantedly, Inc. 1PTUHSF42-ʹ͸༷ʑͳ*OEFY͕͋Δ  6OJRVF*OEFY  .VMUJDPMVNO*OEFY  *OEFYFTPO&YQSFTTJPOT

     1BSUJBM*OEFYFT
  27. ©2019 Wantedly, Inc. .VMUJDPMVNO*OEFY IUUQTVTFUIFJOEFYMVLFDPNTRMXIFSFDMBVTFUIFFRVBMTPQFSBUPSDPODBUFOBUFELFZTΑΓҾ༻ lෳ਺ΧϥϜʹରͯ͠ͷJOEFYzΧϥϜͷ૊Έ߹Θͤͱͯ͠ιʔτ

  28. ©2019 Wantedly, Inc. .VMUJDPMVNO*OEFYͷར༻ʹΑΔߴ଎Խ EXPLAIN SELECT tourist_spots.* FROM tourist_spots WHERE

    tourist_spots.country = “japan" AND tourist_spots.city = “tokyo” QUERY PLAN ----------------------------------------------------------------------- Index Scan using index_tourist_spots_on_country_and_city on tourist_spots (cost=0.42..8.44 rows=1 width=52) Index Cond: ((country = 'japan'::text) AND (city = 'tokyo'::text)) .VMUJDPMVNOJOEFY͋Γ EXPLAIN SELECT jobs.* FROM jobs WHERE jobs.id = 1 QUERY PLAN ----------------------------------------------------------------------- Index Scan using index_tourist_spot_without_multiple_indices_on_city on tourist_spot_without_multiple_indices (cost=0.42..8.44 rows=1 width=52) Index Cond: (city = ‘tokyo’::text) Filter: (country = 'japan'::text) .VMUJDPMVNOJOEFYແ͠
  29. ©2019 Wantedly, Inc. .VMUJDPMVNO*OEFYͷར༻ʹΑΔߴ଎Խ EXPLAIN SELECT "tourist_spots".* FROM "tourist_spots" WHERE

    "tourist_spots"."country QUERY PLAN ----------------------------------------------------------------------- Bitmap Heap Scan on tourist_spots (cost=4.50..41.67 rows=10 width=52) Recheck Cond: (country = ‘japan’::text) -> Bitmap Index Scan on index_tourist_spots_on_country_and_city (cost=0.00..4.49 rows=10 width=0) Index Cond: (country = 'japan'::text) .VMUJDPMVNO*OEFY͸ઌ಄ͷཁૉͷJOEFYͱͯ͠΋ಈ࡞͢Δ ΑΓৄࡉΛ஌Γ͍ͨํ͸ IUUQXXXQPTUHSFTRMPSHEPDTDVSSFOUTUBUJDJOEFYFTNVMUJDPMVNOIUNM
  30. ©2019 Wantedly, Inc. *OEFYFTPO&YQSFTTJPOT ؔ਺ͳͲͷฦΓ஋ΛLFZͱͯ͠JOEFYΛ࡞Δࣄ͕Ͱ͖Δ Table "profiles" Column | Type

    | Collation | Nullable | Default ---------+------------------------+-----------+----------+--------------------------------- id | bigint | | not null | nextval('jobs_id_seq'::regclass) email | character varying(255) | | not null | ''::character varying Indexes: "profiles_pkey" PRIMARY KEY, btree (id) "index_profiles_on_lower_email" btree (lower(email::text))
  31. ©2019 Wantedly, Inc. *OEFYFTPO&YQSFTTJPOT MPXFS FNBJM Λར༻ͨ͠8)&3&ͰJOEFY͕ޮ͘ EXPLAIN SELECT profiles.*

    FROM profiles WHERE (lower(email) = '[email protected]') QUERY PLAN ----------------------------------------------------------------------- Index Scan using index_profiles_on_lower_email on profiles (cost=0.29..8.30 rows=1 width=48) Index Cond: (lower(email) = '[email protected]'::text) ৄࡉ͸IUUQXXXQPTUHSFTRMPSHEPDTDVSSFOUTUBUJDJOEFYFTFYQSFTTJPOBMIUNMࢀর
  32. ©2019 Wantedly, Inc. 42-࣮ߦͷ/FYU4UFQ+0*/

  33. ©2019 Wantedly, Inc. 42-࣮ߦͷ/FYU4UFQ+0*/ QUERY PLAN ------------------------------------------------------------------------------------------------------ HashAggregate (cost=1213.79..1220.12 rows=634

    width=16) -> Hash Join (cost=54.28..1188.79 rows=5000 width=16) Hash Cond: (jobs.company_id = companies.id) -> Seq Scan on jobs (cost=0.00..897.00 rows=50000 width=8) -> Hash (cost=41.78..41.78 rows=1000 width=16) -> Index Scan using companies_pkey on companies (cost=0.29..41.78 rows=1000 width=16) Index Cond: (id < 1000) )BTI"HHSFHBUF )BTI+PJO 4FR4DBO )BTI *OEFY4DBO
  34. ©2019 Wantedly, Inc. 1PTUHSF42-ͷ+0*/ΞϧΰϦζϜ ͭͷ+0*/ΞϧΰϦζϜ͕ଘࡏ w /FTUFE-PPQ+PJO w )BTI+PJO w

    .FSHF+PJO ࠷దͳΞϧΰϦζϜ͕ࣗಈతʹબ୒͞ΕΔ w JOEFYͷ༗ແ΍౷ܭ৘ใʢσʔλͷྔɾ෼෍ʣʹґଘ
  35. ©2019 Wantedly, Inc. /FTUFE-PPQ+PJO ,z IUUQTXXXTMJEFTIBSFOFUBEPSFQVNQQPTUHSFTRMQFSGPSNBODFUVOJOHΑΓҾ༻ ॏϧʔϓͰ͢΂ͯͷ૊Έ߹ΘͤΛࢼ͢ w 0 /.

    ʜۃΊͯ஗͍ w Ϩίʔυ਺͕গͳ͚Ε͹ߴ଎ w 5BCMFʹJOEFYΛషΕ͹ɺ͋Δఔ౓ߴ଎Խ͕Մೳ Ϩίʔυ਺/ Ϩίʔυ਺.
  36. ©2019 Wantedly, Inc. 5BCMFʹରͯ͠ɺҰ౓ϑϧεΩϟϯͯ͠ )BTI5BCMFΛ࡞੒ w 0 / . 

    w 5BCMF͕શͯ.FNPSZʹࡌΔ͘Β͍খ͍͞αΠζͰ͋Δ ࣄ͕৚݅ w .FNPSZ্Ͱ5BCMFͷϨίʔυΛ୳ࡧͰ͖ΔͷͰߴ଎ )BTI+PJO ,z IUUQTXXXTMJEFTIBSFOFU.JLJ4IJNPHBJQPTUHSFTRMFYQMBJOΑΓҾ༻ 5BCMF Ϩίʔυ਺/ 5BCMF Ϩίʔυ਺. )BTI5BCMF
  37. ©2019 Wantedly, Inc. ιʔτࡁΈͷ5BCMFͱ5BCMFʹର͠ ͯɺҰ౓͚ͩϑϧεΩϟϯ w 0 / . 

    w 5BCMF 5BCMFʹࣄલʹJOEFYΛషͬͯ͋Δࣄ͕৚݅ w ςʔϒϧαΠζ͕େ͖͍࣌ʹ͸࠷΋ߴ଎ .FSHF+PJO ,z IUUQTXXXTMJEFTIBSFOFU.JLJ4IJNPHBJQPTUHSFTRMFYQMBJOΑΓҾ༻
  38. ©2019 Wantedly, Inc. JOEFY͕͋ͬͯ΋+0*/͕஗͍έʔε͸ଘࡏ͢Δ

  39. ©2019 Wantedly, Inc. JOEFY͕͋ͬͯ΋+0*/͕஗͍έʔεͱ͸ʁ ͭͷ+0*/ΞϧΰϦζϜ͸ɺͲΜͳʹߴ଎Խͯ͠΋0 / Ҏ্ w /FTUFE-PPQ+PJOʜ0 /.

     w )BTI+PJOʜ0 / .  w .FSHF+PJOʜ0 / .  /͕େ͖͍ͱɺ+0*/͸ඞͣ஗͘ͳΔ
  40. ©2019 Wantedly, Inc. JOEFY͕͋ͬͯ΋+0*/͕஗͘ͳΔέʔε۩ମྫ EXPLAIN SELECT COUNT(*) FROM users INNER

    JOIN profiles ON profiles.user_id = users.id QUERY PLAN ----------------------------------------------------------------------- Aggregate (cost=23288.72..23288.73 rows=1 width=0) -> Hash Join (cost=354.30..23261.80 rows=10769 width=0) Hash Cond: (users.id = profiles.user_id) -> Seq Scan on users (cost=0.00..11441.64 rows=698964 width=4) -> Hash (cost=219.69..219.69 rows=10769 width=4) -> Seq Scan on profiles (cost=0.00..219.69 rows=10769 width=4)
  41. ©2019 Wantedly, Inc. ରࡦՄೳͰ͋Ε͹ࣄલʹߜΓࠐΜͰςʔϒϧαΠζ/ΛݮΒ͢ EXPLAIN SELECT COUNT(*) FROM users INNER

    JOIN profiles ON profiles.user_id = users.id WHERE users.registered = “t” QUERY PLAN ----------------------------------------------------------------------- Aggregate (cost=8131.17..8131.18 rows=1 width=0) -> Hash Join (cost=1850.65..8128.51 rows=1065 width=0) Hash Cond: (users.id = profiles.user_id) -> Bitmap Heap Scan on users (cost=1496.35..6639.86 rows=69151 width=4) Filter: registered -> Bitmap Index Scan on index_users_on_registered (cost=0.00..1479.06 rows=69151 width=0 Index Cond: (registered = true) -> Hash (cost=219.69..219.69 rows=10769 width=4) -> Seq Scan on profiles (cost=0.00..219.69 rows=10769 width=4)
  42. ©2019 Wantedly, Inc. 42-࣮ߦͷ-BTU4UFQσʔλू໿ "HHSFHBUF

  43. ©2019 Wantedly, Inc. 42-࣮ߦͷ-BTU4UFQσʔλू໿ "HHSFHBUF QUERY PLAN ------------------------------------------------------------------------------------------------------ HashAggregate (cost=1213.79..1220.12

    rows=634 width=16) -> Hash Join (cost=54.28..1188.79 rows=5000 width=16) Hash Cond: (jobs.company_id = companies.id) -> Seq Scan on jobs (cost=0.00..897.00 rows=50000 width=8) -> Hash (cost=41.78..41.78 rows=1000 width=16) -> Index Scan using companies_pkey on companies (cost=0.29..41.78 rows=1000 width=16) Index Cond: (id < 1000) )BTI"HHSFHBUF )BTI+PJO 4FR4DBO )BTI *OEFY4DBO
  44. ©2019 Wantedly, Inc. 1PTUHSF42-ͷ"HHSFHBUFΞϧΰϦζϜ ͭͷ"HHSFHBUFΞϧΰϦζϜ͕ଘࡏ w (SPVQ"HHSFHBUF w )BTI"HHSFHBUF

  45. ©2019 Wantedly, Inc.  (SPVQ"HHSFHBUF w ೖྗ͞ΕͨσʔλΛ(SPVQLFZͰιʔτޙɺ֤άϧʔϓΛॱ࣍ॲཧ͢ΔΞϧΰϦζϜ w JOEFY͕͋ͬͯTPSUࡁΈͰ͋Ε͹ɺύΠϓϥΠϯԽ΋Մೳ 

    )BTI"HHSFHBUF w (SPVQLFZΛLFZͱ͢ΔҰ࣌తͳ)BTI5BCMFΛ࡞੒͠ɺ֤άϧʔϓΛॲཧ͢ΔΞϧΰϦζϜ w σʔλαΠζ͕NFNPSZʹࡌΔ͘Β͍খ͚͞Ε͹͜Ε͕બ͹ΕΔ 1PTUHSF42-ͷͭͷ"HHSFHBUFΞϧΰϦζϜ
  46. ©2019 Wantedly, Inc. ͦͷଞͷ1PTUHSF42-ͷ࣮ߦεςοϓ

  47. ©2019 Wantedly, Inc. 4PSUͱ-JNJU 03%&3#:Λࢦఆ͢Δͱɺ4PSUॲཧ͕ߦΘΕΔ w JOEFY͕͋Ε͹͢Ͱʹ4PSUࡁΈͰ͋ΔͨΊɺ4PSUͷίετ͸͔͔Βͳ͍ w JOEFY͕ແ͍৔߹ɺ4PSUΛߦ͏ඞཁ͕͋Δɻ-JNJUͰߴʑ਺݅ཉ͍͠৔߹Ͱ΋ɺςʔϒϧશମ ͷ4DBOͱ4PSU͕૸ΔɻڊେͳσʔλͰ͸%JTLTPSU͕ൃੜ͠ɺۃΊͯ஗͘ͳΔɻ

    EXPLAIN SELECT page_view_logs.* FROM page_view_logs ORDER BY viewed_at ASC LIMIT 20 QUERY PLAN ----------------------------------------------------------------------- Limit (cost=22026.31..22026.36 rows=20 width=28) -> Sort (cost=22026.31..23278.87 rows=501024 width=28) Sort Key: viewed_at -> Seq Scan on page_view_logs (cost=0.00..8694.24 rows=501024 width=28)
  48. ©2019 Wantedly, Inc. 03%&3#:ʹ͸JOEFY EXPLAIN SELECT page_view_logs.* FROM page_view_logs ORDER

    BY viewed_at ASC LIMIT 20 QUERY PLAN ----------------------------------------------------------------------- Limit (cost=0.42..1.09 rows=20 width=28) -> Index Scan using index_page_view_log_with_indices_on_viewed_at on page_view_log_with_indices (cost=0.42..16698.78 rows=501024 width=28) *OEFYʹΑͬͯܶతʹίετ͕Լ͕Δ w ҎԼͷྫͰ͸ɺ ʹݮগʂ
  49. ©2019 Wantedly, Inc. ·ͱΊ

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  54. ©2019 Wantedly, Inc. +40/5ZQFT INSERT INTO events (payload) VALUES (“{\”name\":\"test1\",\"value\":\"OK\"}")

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