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これでわかるB-treeアルゴリズム / B-tree algorithm
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ハトネコエ
December 06, 2018
Technology
10
8.7k
これでわかるB-treeアルゴリズム / B-tree algorithm
・二分探索木 (binary search tree)
・AVL tree
・B-tree
・B+ tree
について順を追いながら説明。
流れを細かく書いたので、わかりやすいと思います。
ハトネコエ
December 06, 2018
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Transcript
͜ΕͰΘ͔Δ(?) B-tree ΞϧΰϦζϜ 2018/12/06 ࣾษڧձ ϋτωίΤ
ϋτωίΤ @nekonenene ࢲॳԻϛΫͰ͢ ͝ଘ͋ͷํ
• BͱݺΕΔ • σʔλߏͷҰछͰ͋ΔߏͷҰछ • ϧʔτ͔Βͷߴ͕͞Ұఆͷฏߧʢ͍͜͏͗ʣͷҰछ • Mongo DBͳͲͷσʔλϕʔεͷ΄͔ɺ WindowsͷϑΝΠϧγεςϜNTFS
MacͷϑΝΠϧγεςϜAPFS ͳͲͰΘΕ͍ͯΔ B-tree
• MySQLͷσʔλϕʔεΤϯδϯ InnoDB Ͱɺ ॱʑʹΞΫηε͢ΔੑೳΛ্͛ͨ B+ tree ͕ΘΕ͍ͯΔ • Oracle
Database MacͷϑΝΠϧγεςϜͩͬͨHFS+ Ͱ B* tree ͕ΘΕ͍ͯΔʢࠓճѻ͍·ͤΜʣ B-tree ѥछ
Χϯλϯͳͷ͔Β ࢝Ί͍ͯ͜͏
• ͬͱ୯७ͳߏ • খ͍͞ΛࠨԼʹɺେ͖͍ΛӈԼʹ͚͍ͭͯ͘ ೋ୳ࡧ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ ೋ୳ࡧɿྫ 10 5
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ ೋ୳ࡧɿྫ 10 5 ϊʔυ ࢠϊʔυ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ ೋ୳ࡧɿྫ 10 5 3 2
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ ೋ୳ࡧɿྫ 10 5 3 2 8
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ ೋ୳ࡧɿྫ 10 5 3 2 8 4
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ ೋ୳ࡧɿྫ 10 5 3 2 1 8 4
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ ೋ୳ࡧɿྫ 10 5 3 2 1 8 4 6
• ͷόϥϯε͕ۉʹ͍ͬͯΕɺ ཁૉ n ʹରͯ͠୳ࡧʹ͔͔Δ࠷ѱܭࢉྔ O (log n) ʹͰ͖Δ •
ͭ·Γɺσʔλ͕૿͑ͯݕࡧͷ͕࣌ؒ૿͑ͳ͍ ೋ୳ࡧͷར 10 5 2 8 16 12 20 ཁૉ n ܭࢉྔ
• ࠨԼͷਤͷΑ͏ͳภͬͨߏͷ࠷ѱͷ߹Λߟ͑Δ • ཁૉ͕ଟ͍΄ͲൺֱΛ͓͜ͳ͏ͷͰ࠷ѱܭࢉྔ O (n) ೋ୳ࡧͷܽ ཁૉ n ܭࢉྔ
10 5 3 2
ͦΕͳΒͬͨ ߏʹ͠Α͏ʂ
• ߟҊऀͷ2ਓͷ໊લ͕༝དྷʢAdelson-Velskii and Landis' treeʣ • ࠨ෦ͷߴ͞ͱӈ෦ͷߴ͕͞1ΑΓେ͖͘ͳͬͨΒ ʮͷճసʯʹΑΓ࠶ߏ͠ɺฏߧΛอͭ AVL
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5 3 ʮ10ʯ͔Βݟͯ ࠨߴ͞ 2 ӈߴ͞ 0 ʹͳͬͯ͠·͏ ͦ͜Ͱɺͷճసʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5 3 த৺ʹ͍ͨ ʮ5ʯΛʹͯ͠ ଞΛࢠʹ͢Δ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5 3 2
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5 3 2 8
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5 3 2 8 4
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5 3 2 8 4 1
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5 3 2 8 4 1 ͭͳ͛ΒΕΔՕॴͷߴ͞ͷ͕ࠩ2 ͜Εͷճస͕ى͜Δʁ ? ?
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5 3 2 8 4 1 ʮ5ʯ͔Βݟͯ ࠨͷߴ͞ 3 ӈͷߴ͞ 2 ʮ3ʯ͔Βݟͯ ࠨͷߴ͞ 2 ӈͷߴ͞ 1 ࠨ෦ͱӈ෦ͷߴ͞ͷࠩΛ ݟΔͷͰɺ·ͩ͑·͢
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5 3 2 8 4 1 6 ʮ10ʯ͔Βݟͯ ࠨͷߴ͞ 2 ӈͷߴ͞ 0 ͷճసνϟϯεʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 10 5 3 2 8 4 1 6 த৺ʹ͍Δ ʮ8ʯΛʹ͠ɺ ଞ2ͭࢠʹ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ AVLɿྫ 8 5 3 2 6 4 1 10 ʂ
• ࠷ѱܭࢉྔ͕େ͖͘ͳΒͳ͍Α͏ɺ ͷճసΛ༻͍ɺͰ͖Δ͚ͩภΓͷͳ͍Λ࡞͍ͬͯͬͨ • ͜ͷΑ͏ͳฏୱʹ͚ۙΔߏΛ ฏߧʢ͍͜͏͗ʣͱݺͿ AVL ͓͞Β͍
• ͷߴ͕͞ߴ͘ͳΓ͍͢ • ݁Ռɺσʔλྔ͕ͱͯଟ͍߹ɺݕࡧʹ͕͔͔࣌ؒΔ • → ͦ͜Ͱ B-tree ʂ AVLͷܽ
• ֤ϊʔυʹ࣋ͨͤΔΛ1ͭͰͳ͘ෳʹ͠ɺͷߴ͞Λ͑Δ • ࠓ·ͰͷϊʔυXΑΓখ͍͔ͦ͞ΕҎ্͔ɺͷ 2ຊͷࢬ͔͍࣋ͬͯ͠ͳ͔͕ͬͨɺB-treeͰΑΓଟ͘ͷࢬΛ࣋ͭ • ྫ͑ X ͱ Y
ͷ 2 ͭͷΛϊʔυʹͭͱܾΊͨ߹ɺ Xະຬ / XҎ্ͰYະຬ / YҎ্ ͷ3ຊͷࢬΛϊʔυ࠷େͰ࣋ͭʢΦʔμʔ3ʣ ͦ͜Ͱ B-tree
• ϊʔυ͕࠷େͰ࣋ͭࢬͷʹԠͯ͡ɺ ʮΦʔμʔ m ͷB-treeʯͱ͍͏ݴ͍ํΛ͢Δ • Φʔμʔ 3 ʙ 5
͕Α͋͘ΔΒ͍͠ • ࠓճɺΦʔμʔ 3 ͷ B-tree ʢͭ·Γϊʔυʹ2ͭͷΛ࣋ͭʣ ʹ͍ͭͯྫΛݟ͍ͯ͘ɻ ࢠϊʔυΛ2ʙ3࣋ͭ͜ͱ͔Βɺ2-3 tree ͱݺΕΔ Φʔμʔ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 5 10 ϊʔυʹ2ͭͷ Λͭ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 5 10 ϊʔυʹ 3ͭͷ͕…… 3 த৺ͷϊʔυʹҠಈʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 5 10 3
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 5 10 2 3
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 5 8 2 3 10
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 5 8 2 3 10 4
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 5 8 2 3 10 4 த৺ͷ ϊʔυʹҠಈʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 5 8 2 3 10 4 Զ͕ϊʔυͩʂ த৺ͷ ϊʔυʹҠಈʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 3 8 2 10 4 5
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 3 8 1 10 4 5 2
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 3 6 1 8 4 5 2 10 த৺ͷ ϊʔυʹҠಈʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 3 6 1 8 4 5 2 10 ͋Ε……͓अຐʁ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 3 6 1 8 4 5 2 10 த৺ͷ ϊʔυʹҠಈʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B-treeɿྫ 3 6 1 8 4 5 2 10 ߴ͞Ξοϓʂ ˍʂ
• جຊͷΞϧΰϦζϜ B-tree • ࠷ԼͷϊʔυΛϙΠϯλͰͭͳ͗߹Θͤͨ͜ͱͰɺ খ͞ͳ͔Βେ͖ͳॱʑʹΞΫηε͍ͯ͘͠ ͱ͍͏ڍಈͷύϑΥʔϚϯεΛ্͛Δ͜ͱʹޭ • ઌ΄Ͳಉ༷ɺΦʔμʔ 3
ʢϊʔυ͕࠷େͰ࣋ͭࢬ͕3ຊʣͷ B+ tree ʹ͍ͭͯݟ͍ͯ͘ B+ tree
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 10
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 10 ϊʔυʹ 3ͭͷ͕…… 3 த৺ͷϊʔυʹҠಈʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 3 10 ϊʔυҠಈͭͭ͠… ͱͷ͢ʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 3 10 ࠷Լಉ࢜Λ ϙΠϯλͰͭͳ͙ʂ ͜Ε͕ B+ tree ͷ Ұ൪ͷಛʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 3 10
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 2 10 3
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 2 8 3 10 த৺ͷ ϊʔυʹҠಈʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 2 8 3 10 8 ͱͷ͢
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 2 8 3 10 8 4 த৺ͷ ϊʔυʹҠಈʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 2 8 3 10 8 4 3 ͱͷ͢
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 8 3 10 8 4 3 3ͭʹͳͬͯ͠·ͬͨ…… 2
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 8 3 10 8 4 3 2 த৺ͷ ϊʔυʹҠಈʂ 3ͭʹͳͬͯ͠·ͬͨ……
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 3 8 5 Θ͔Γ͍͢Α͏ ্෦͚ͩߟ͑Δ ৽͍͠ύύͩΑ ͱͷ͢
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 3 8 5 Θ͔Γ͍͢Α͏ ্෦͚ͩߟ͑Δ 5ະຬ 5Ҏ্
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 8 3 10 8 4 3 2 ͳͷͰಉ༷ʹ……
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 8 3 10 8 4 3 2 5 ͜͏ͳΔʂ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 8 3 10 8 4 3 2 5 ʢҙʣ ͜͏ͳΒͳ͍ Φʔμʔ 3 ͷ BͰ ࠷ 2 ͭͷ ࢠϊʔυΛ࣋ͭ
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 8 3 10 8 4 3 2 5 Λͯ࣍͠…
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 8 3 10 8 4 3 1 5 2
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 8 3 10 8 4 3 1 5 2 6
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 8 3 10 8 4 3 1 5 2 6 ʂ
• ࠷Լͷϊʔυ͕ϙΠϯλͰͭͳ͕͍ͬͯΔͨΊɺ খ͞ͳ͔Βେ͖ͳॱʑʹΞΫηε͍͖͍ͯͨ͠߹ʹɺ ຖճݕࡧͷखؒΛڬ·ͳͯ͘ࡁΉ • ͳ͓ɺ͜ͷ࠷ԼͷϊʔυΛ ʮϦʔϑϊʔυʢleaf nodesʣʯͱݴ͍·͢ B+ tree
͓͞Β͍
• 10 → 5 → 3 → 2 → 8
→ 4 → 1 → 6 ͷॱʹೖΕ͍͖ͯ·͢ B+ treeɿྫ 5 5 8 3 10 8 4 3 1 5 2 6 Ϧʔϑϊʔυ
• ΧϥϜʹΠϯσοΫεΛషΔ͜ͱͰɺ B+ tree ͷߏ͕࡞ΒΕɺॱʑʹͳ͍ͬͯΔͷͰ ൣғݕࡧ͕εϐʔυग़͍͢͠ • ͳ͓ɺInno DB ͰϦʔϑϊʔυؒͷϙΠϯλ͕
ҰํͰͳ͘ํʹͳ͍ͬͯΔ Inno DB ʹ͓͍ͯ 5 8 10 4 3 1 2 6
• AVL https://www.cs.usfca.edu/~galles/visualization/AVLtree.html • B-tree https://www.cs.usfca.edu/~galles/visualization/BTree.html • B+ tree https://www.cs.usfca.edu/~galles/visualization/BPlusTree.html
• ͦͷଞ https://www.cs.usfca.edu/~galles/visualization/Algorithms.html ศརͳγϛϡϨʔλʔ