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Fan Qi Database Lab 1, com1 #01-08 CS3223 Tutorial 4.

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Presentation on theme: "Fan Qi Database Lab 1, com1 #01-08 CS3223 Tutorial 4."— Presentation transcript:

1 Fan Qi fan.qi@nus.edu.sg Database Lab 1, com1 #01-08 CS3223 Tutorial 4

2 Block I/O Sorting 1 block for output

3 Selection Access: Table Scan Index Scan Index Seek Index Intersection Index Access: B+ Tree : range and equality Hash : equality only Cost B+ Tree Navigation cost Leaf page scan cost RID look up cost Hash Index Chain Cost (Reading Bucket Page into Memory) RID look up cost

4 Question 1

5 Disk 1 1 2 2 … … 320 321 322 … … 640 641 642 … … 960 961 962 … … 1280 Memory in out

6 Question 1

7 Take-away points Block I/O reduces sorting time Diminishing return at some point, why? In practice, read/write block are of the same size SortTime 319-Merge640,000,000ms 256-Merge, 1 in 64 out344,687,500ms 16-Merge, 16 in 64 out126,875,000ms 8-Merge, 32 in 64 out135,156,250ms 4-Merge,64 in 64 out195,500,000ms

8 Question 3 1. Table Scan

9 Disk Question 3 pr 250 pages Rid Look up to get name

10 Question 3 p r 250 pages500 pages Intersect Disk Rid Look up to get name

11 Question 3 Disk p 200 pages Rid Look up to get name for each record

12 Question 4

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