Page 224 - DCAP603_DATAWARE_HOUSING_AND_DATAMINING

Data Warehousing and Data Mining

notes
Example:
Let |sc| = found set * total number of tuples = 10% * 10,000 = 1,000
Let ati = 0.01

Let itime(bm) = 0.04
The response time of a query = |sc| * ati * itime(rdi)
= 1,000 * (0.01 + 0.04) = 50 sec..
If the foundset is 20%, it will be 2,000 * (0.01 + 0.04) = 100 sec. and the response time are summarised
in Table 11.7.
table 11.7: the response time of BitMap index in different found sets

found set response time found set response time
10% 50 sec. 60 % 300 sec.
20% 100 sec. 70 % 350 sec.
30% 150 sec. 80 % 400 sec.
40% 200 sec. 90 % 450 sec.
50% 250 sec. 100 % 500 sec.

Based on Table 11.7, the average response time from 10 % to 100% found sets is (50 + 100 + 150 +
200 + 250 + 300 + 350 + 400 + 450 + 500)/ 10 = 275 sec.

11.5 comparison of the Query processing strategies

The Comparison of the Query Processing Strategies is shown in Table 11.8.
table 11.8: comparison of the Query processing strategies

Query processing full scan riD index BitMap index inverted
strategies technique technique technique partition index
technique
Data Processing Table Level Index and Table Index and Table Index Level
Level Level Level
Average Response 1500 Sec. 990 sec. 902 sec. 275 sec.
time
Time required 0.05 sec. 0.07 sec. 1.2 sec. 0.04 sec.
to execution
Instructions of
Algorithm
Small Selective Bad Good Good Excellent
Tuples
Large Selective Excellent Average Average Excellent
Tuples
Small Selected Bad Bad Bad Excellent
Attributes
Select or Retrieve Yes Yes Yes No
all Attributes from
table level
Frequently set No No No No
attributes

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