Slideshow:
Intro to bitmap index:
requirement
Requirement to use a bitmap index:
Intro to bitmap index:
current set of values
The bitmap index of a
record field f
Example bitmap index of a
record field f
Example bitmap index of a
record field f
Example bitmap index of a
record field f
Bitmap index of the
jewelry purchase data
Input data:
Bitmap index of the
jewelry purchase data
Input data:
Bitmap index of the
jewelry purchase data
Input data:
- Assumption:
- Records in
a file/relation
occupy a
permanent location
in the file/relation
- I.e.:
- A records is uniquely identified by a position ID
- Records in
a file/relation
occupy a
permanent location
in the file/relation
- Current Value Set:
- F = the current set of values stored in a field f in the records
- Example:
Records: field f ---------+--------+------ Record 1: ..... 5 ... Record 2: ..... 7 ... Record 3: ..... 5 ... Record 4: ..... 8 ... Record 5: ..... 7 ... F = {5, 7, 8} (= current set of values in field f)
- Bitmap index of a field f:
- is a collection of
bit vectors of
length
n
(where n is the
number of records)
- there is one bit vector
for each current value v in
field f
- The bit vector for
the value v is
constructed as follows:
x1 x2 x3 x4 ..... xi ...... xn xi = 1 if the ith record's field f = v = 0 otherwise
- is a collection of
bit vectors of
length
n
(where n is the
number of records)
- Examples:
- A file has 6 records
Fields: A B -------------------------------- record 1: 30 foo record 2: 30 bar record 3: 40 baz record 4: 50 foo record 5: 40 bar record 6: 30 bazThe bitmap index for the field A is:
value 123456 ---------------------------- 30 110001 <---- bit vector 40 001010 50 000100 Explanation: The value 30 appears in the records: 1, 2, 6 So: bit #1, #2 and #6 are setThe bitmap index for the field B is:
value 123456 ---------------------------- foo 100100 <---- bit vector bar 010010 baz 001001 Explanation: The value foo appears in the records: 1, 4 So: bit #1 and #4 are set
- A file has 6 records
- Data on people who
buy jewelry:
(age, salary (in $1,000)) 1(25,60) 2(45,60) 3(50,75) 4(50,100) 5(50,120) 6(70,110) 7(85,140) 8(30,260) 9(25,400) 10(45,350) 11(50,275) 12(60,260)
- The bitmap index on
age:
Value 123456789012 ------------------------------ 25 100000001000 30 000000010000 45 010000000100 50 001110000010 60 000000000001 70 000001000000 85 000000100000The bitmap index on salary:
Value 123456789012 ------------------------------- 60 110000000000 75 001000000000 100 000100000000 110 000001000000 120 000010000000 140 000000100000 260 000000010001 275 000000000010 350 000000000100 400 000000001000(The bit index for 2 records are high lighted in red)