1

Query Processing: The Basics

Chapter 10

(animations)

2

Merge: An Example

2 3 5 6

1 7 10 15

Input buffersOutput buffer

1 2 3 5 6 7 10 15

2 3

1 7

5 6

10 15

1 23 56 710 15

Output runInput runs

3

Duplicate elimination During Merge

2 3 5 6

1 3 5 15

Input buffersOutput buffer

1 2 3 5 6 15

2 3

1 3

5 6

5 15

1 23 56 15

Output runInput runs Last key used

1215356

Key 3 ignored: duplicate

Key 5 ignored: duplicate

4

Block-Nested Loop Illustrated

Output buffer

s

r

Input buffer for s

Input buffer for r

… and so on

r s

5

Join During Merge Illustrated

1 3p p

r

s

DA

BE

p p4 0

0 9q q

r9

8 7 3s s s

s7

t t2 5

u u u2 5 0

5 7u u

1 1v v

x0

1 3 1 3p p p pp p p p4 0 0 4

8 7 3s s ss s s7 7 7

5 7 5 7 5 7u u u u u uu u u u u u2 2 5 5 0 0

r A=B s