1. MIS 451 Building Business Intelligence Systems
Physical Design

2. Project Planning
Requirements Analysis
Logical Design
Physical Design
Data Staging
Data Analysis (OLAP)

3. The Storage Hierarchy CPU Small Fast Cache Access Speed
MIPS
Small
Fast
Cache
10-8 second
Access Speed
Storage Capacity
Memory
10-7 second
Disk
10-2 second
Large
Slow

4. The Storage Hierarchy
CPU
Memory
Disk

5. The Storage Hierarchy
Logical unit of data transferred between disk and memory is block (4k bytes)
Physical unit on disk is cylinder, tract, sector
There is a mapping between block and sector.

7. Performance Improvement
List total amount of sales for product ’17’
Select sum(SALES_AMT)
From SALESFACT S, PRODUCT P
Where S.Product_key = P. Product_key
and P.PNAME=‘17’

8. Performance Improvement
Consider a simpler query:
List product_key for product ’17’
Select product_key
From PRODUCT
Where PNAME=‘17’

9. Performance Improvement
Product table
1M records, each record 200 bytes long
Block is 4k size, block access time is 0.01s
4k/200=20 records per block
Number of blocks: 1M/20=50K
Sequential search
Time: 25K*0.01s=250s=4min.

10. Performance Improvement
Binary search
Time: lg(50K)*0.01s=16*0.01s=0.16s
B+ tree index
Create index pn on product(pname);
If each node in B+ tree has 117 keys, then
Seek: lg117(1M)=3
Read the block from main file: 1
Total time = 4*0.01 = 0.04s

11. Performance Improvement
List total amount of sales for product category ‘c1’
Select sum(SALES_AMT)
From SALESFACT S, PRODUCT P
Where S.Product_key = P. Product_key
and P.PCNAME=‘C1’

12. Performance Improvement
Consider a simpler query:
List all product_keys for product category ‘c1’
Select product_key
From PRODUCT
Where PCNAME=‘c1’

13. Performance Improvement
Suppose there are only 4 product categories for 1M products
Create a B+ tree index???
Suppose the size of product category and block ID is 10 bytes
Size of index = 1M * 10 = 10 M bytes

14. Performance Improvement
A bitmap index for an attribute A is a collection of bit vectors, one for each possible value of A. The vector for value v has 1 in position i if the ith record has v for attribute A.
CREATE BITMAP INDEX bitpc ON PRODUCT (PCNAME);
Size of bitmap index
1M*4/8=500K bytes

15. Performance Improvement
Bitmap index is suitable for low cardinality attribute.
Cardinality(A) = # of possible values for A/#of records
Compared with B+ tree index, bitmap index has the following advantages for low cardinality attributes
Storage space saving
Efficient for boolean operations