1. Dual Bitmap Index: Space-Time Efficient Bitmap
Index for Equality and Membership Queries
Niwan Wattanakitrungroj and Sirirut Vanichayobon
Information Systems Technology and Applied Research Laboratory
Department of Computer Science, Prince of Songkla University

2. Outline Introduction Variations of Bitmap Index - Simple Bitmap Index
- Interval Bitmap Index
- Scatter Bitmap Index
- Encoded Bitmap Index
- Dual Bitmap Index
Performance Study
Conclusion

3. Introduction - A data warehouse is a large repository of information
accessed through OLAP application.
A majority of requests for information from a data warehouse
involve dynamic ad hoc queries.
The ability to answer these queries quickly is a critical issue in
the data warehouse environment.

4. Introduction To speed up query processing : Summary tables Indexes
Parallel machines
To speed up query processing :

5. Bitmap Index Characteristic :  simple to represent  uses less space
Introduction :
Bitmap Index
 simple to represent
 uses less space
 more CPU-efficient
 low-cost Boolean operations
Characteristic :

6. Bitmap Index Introduction : Employee Table Name Gender Education Suda
Select Count(*)
From Employee
Where Gender=“F”;
RID 1 2 3 4 5 …
Name
Gender
Education
Suda F BS
Wichai M
Jonh MS
Marry
PhD
Somsak …
Answer : 2
Equality Query
Select Name
From Employee
Where Gender=“M” and
Education=“MS”
RID 1 2 3 4 5 … F 1 … M 1 … BS 1 … MS 1 …
PhD 1 …
Answer : John
Membership Query
Select Name
From Employee
Where Education in {MS,PhD}
Answer : John, Marry

7. Outline Introduction Variations of Bitmap Index - Simple Bitmap Index
- Interval Bitmap Index
- Scatter Bitmap Index
- Encoded Bitmap Index
- Dual Bitmap Index
Performance Study
Conclusion

8. Simple Bitmap Index Variations of Bitmap Index Related Work C = 15
15 bitmap vectors
Let C be a number of distinct values of the indexed attribute(Cardinallity).
Bitmap vectors :
Query :

9. Interval Bitmap Index Variations of Bitmap Index Related Work C = 15
8 bitmap vectors
Bitmap vectors :
Query

10. Scatter Bitmap Index m = 5 Variations of Bitmap Index Related Work
8 bitmap vectors,
Bitmap vectors :
Query

11. Encoded Bitmap Index Variations of Bitmap Index Related Work C = 15
4 bitmap vectors
Bitmap vectors :
Mapping all Bitmap Vector
Query :

12. Outline Introduction Variations of Bitmap Index - Simple Bitmap Index
- Interval Bitmap Index
- Scatter Bitmap Index
- Encoded Bitmap Index
- Dual Bitmap Index
Performance Study
Conclusion 

13. Dual Bitmap Index Encoding Scheme of five bitmap indices
Variations of Bitmap Index
Dual Bitmap Index
Encoding Scheme of five bitmap indices
Need C
bitmap vectors
Need
bitmap vectors
Need
bitmap vectors
Need
bitmap vectors
Need
bitmap vectors

14. Variations of Bitmap Index
Dual Bitmap Index

15. Creation of Dual Bitmap Index
Variations of Bitmap Index
Creation of Dual Bitmap Index
C =15
A = {0,1,2,…,14}
Assign an increasing sequence of numbers to each of the distinct values of A (i.e., 0,1,…,C-1).
n = 6
2. Calculate n :
(The total number of bitmap vectors created )
3. Calculate :
(the highest value of C that can be represent by n bitmap vector)
hiC = 15
4. For each value v on record at position i in A
if i = r and s
otherwise
where
and v is the value of an indexed attribute for any record.

16. Equality and Membership Queries
Variations of Bitmap Index : Propose Bitmap Index
Equality and Membership Queries
“A = 2”
1. Find the sequence number of the searching value. 2.
where
and v is the value of an indexed attribute for any record.

17. Outline Introduction Variations of Bitmap Index - Simple Bitmap Index
- Interval Bitmap Index
- Scatter Bitmap Index
- Encoded Bitmap Index
- Dual Bitmap Index
Performance Study
Conclusion

18. Performance study

19. Performance study
Number of bitmap vectors used to represent an attribute with cardinality C
(Space)
Simple
Interval
Scatter
Dual
Encoded
Scatter
Dual
Encoded

20. Performance study

21. Performance study Space-Time Trade-off for five Bitmap Indices
C=50, N=1,000,000 (The data sets from TPC-H Benchmark)
Simple
Interval
Scatter
Encoded
Dual

22. Outline Introduction Variations of Bitmap Index - Simple Bitmap Index
- Interval Bitmap Index
- Scatter Bitmap Index
- Encoded Bitmap Index
- Dual Bitmap Index
Performance Study
Conclusion

23. Conclusion Simple Bitmap Index requires the most space.
Encoded Bitmap Index’ s processing time is the worst.
Dual bitmap index uses less space while maintaining query processing time for equality and membership queries.
Dual Bitmap Index achieves this by representing each attribute value using only two bitmap vectors, and only the low-cost Boolean AND operation is used to answer equality query.
Dual Bitmap Index has better space-time performance than the other bitmap indexing techniques.

24. Thank You
Question & answer