Chapter 26

Question 1

Can we use indexing for speed

Answer 1

Yes

Question 2

What is indexing

Answer 2

An example of catalogue and library. Indexing is physical.

Question 3

What are conventional indexing techniques

Answer 3

• Dense
• Sparse
• Multi-level

Question 4

What is Dense indexing technique

Answer 4

Data file is divided into blocks. Then make an index table. Then every block has an entry in index table. just like library example.

Question 5

What is sparse indexing technique

Answer 5

In sparse indexing, it keeps normally only one key of data file and some keys in data file will not have an entry in index file. One big disadvantage is that it searches for data file block again and this degrade performance.

Question 6

What is sparse multilevel indexing technique

Answer 6

In this technique, there are 2 blocks(levels) in sparse. Search mechanism goes from top most 2nd level to 1st level and then in data file

Question 7

What is B-tree indexing

Answer 7

Its a tree structure. B-tree is balance tree. Its all last nodes distance always same from root. It is also called B Plus tree.

Question 8

What are disadvantages of b-tree

Answer 8

B-tree is case sensitive, if there is extra space B-tree does not work, B-tree can be very length and take a lot of time. There are limitations in insert in B-tree. On insert node will break and it could chain reaction of breaking nodes till root. Thus the height of B-tree can change. So dataware house environment it is not recommended.

Question 9

What is hash base indexing

Answer 9

In hash base indexing, a key is allotted for each data set. We maintain a table for that keys and we can search on it easily therefore.

Question 10

What are 2 types of hash base indexing

Answer 10

1- Use external memory

2- Do not use external memory

Question 11

What are 2 categories of hash base indexing

Answer 11

1- Double hash

2- Single hash

Question 12

What is primary index in hash base indexing

Answer 12

We use primary index just like card catalogue to search for records

Question 13

What is secondary index in hash base indexing

Answer 13

We use 2 levels on indexing in secondary indexing. First pointer lead us to first level and if we do not get desired result we will go to second level and then get right record. It means it is just like primary indexing with additional one more level.

Question 14

What is the difference between primary key and primary index

Answer 14

Primary key is always unique but primary index is not always unique. Example of student id and department id. A student is always unique but a student can join multiple departments.

Question 15

What happen when block overflow

Answer 15

Page fault