443 - 507: Indexing based on Hashing

Question 1

What is the purpose of a hash function in database indexing?

Answer 1

To map data to buckets for efficient storage and retrieval.

Question 2

What is a limitation of static hashing?

Answer 2

It cannot dynamically adjust to the data size, leading to potential overflows and underutilization.

Question 3

What is the main goal of dynamic hashing techniques like extendible hashing?

Answer 3

To adapt the number of buckets dynamically without global reorganization.

Question 4

In extendible hashing, what is the role of the directory?

Answer 4

Maps records to pages and grows dynamically when needed.

Question 5

What happens when a page with local depth c reaches global depth d in extendible hashing?

A) The entire directory is reorganized.
B) The global depth d is increased.
C) The page is deleted.
D) A new hash function is applied.

Answer 5

B) The global depth d is increased.

Question 6

Which method resolves overflow in static hashing?

A) Dynamic bucketing
B) Linear probing
C) Directory doubling
D) Re-indexing

Answer 6

B) Linear probing

Question 7

What is the primary advantage of Linear Hashing over Extendible Hashing?
a) Better range query support
b) Requires no directory
c) Higher storage utilization
d) Faster retrieval speed

Answer 7

b) Requires no directory

Question 8

Define Linear Hashing.

Answer 8

Linear Hashing dynamically splits buckets one by one in a round-robin fashion to handle data growth without requiring a directory.

Question 9

What is the allocation factor (β) in Linear Hashing?

Answer 9

It is defined as 𝛽=𝑥/𝑏×𝑀 , where x is the number of records, b is the bucket capacity, and M is the number of buckets in the primary file.

Question 10

What triggers a split in Linear Hashing?

Answer 10

A split occurs when the allocation factor β exceeds a predefined threshold.