Slide 92
Slide 92 text
Self-joinがなぜ問題か︖
• ナイーブなTruncationがうまく機能しない
• あるユーザの追加/削除が他のユーザにも影響してしまうため
• Self-joinなしの従来の想定よりも閾値𝝉の値に⼤きく依存してしまう à 𝜏 をどう設定するか︖
92
SELCT SUM(Amount)
FROM Transaction, People P1, People P2
WHERE P1.ID = From AND P2.ID = To;
ID Location
p1 Tokyo
p2 Kyoto
p3 Hokkaido
p4 Okinawa
…
From To Amount
p1 p2 1,000
p3 p4 1,000
p5 p6 1,000
p7 p8 1,000
p9 p10 1,000
…
…
p1
p3
p5
p7
p9
p2
p4
p6
p8
p10
𝜏 = 1,000
𝐼 𝐼3
…
p1
p3
p5
p7
p9
p2
p4
p6
p8
p10
pz α
𝑄 𝐼, 𝜏 = 1,000×
1
2
𝑁 𝑄 𝐼3, 𝜏 = 0
N
追加
People(ID, Location) Transaction(From, To, Amount)