Extendable hashing is an advanced hashing technique that uses a dynamic directory structure and adjustable bucket sizes to effectively manage varying data volumes while minimizing collisions and the need for rehashing. This method enhances scalability and performance in data storage and retrieval, making it ideal for database management and caching systems. Its flexibility allows it to adapt to changing data distributions, addressing the limitations of traditional fixed-size hash tables.

1. Extendable
Hashing
E.CHAITHANYA KUMAR
23H51A6713
CSD-03

2. Hashing Fundamentals
1 Hash Functions
Hashing maps data to a
unique fixed-size value
or "hash code" using a
hash function.
2 Hash Tables
Data is stored in hash
tables and accessed by
its hash code, providing
constant-time lookup.
3 Collisions
Collisions occur when
different inputs map to
the same hash code,
leading to performance
issues.

3. Limitations of Traditional Hashing
Fixed Size
Traditional hash tables have a fixed
size, limiting their ability to adapt to
changing data volumes.
Collisions
Collisions can lead to performance
degradation as the hash table fills up.
Resizing
Resizing a hash table is an expensive operation, requiring rehashing of all existing data.

4. Extendable Hashing Concept
1 Dynamic Directories
Extendable hashing uses a dynamic directory structure to handle growing
data volumes.
2 Adaptive Bucket Size
Bucket sizes are adjusted based on data distribution, avoiding performance
issues.
3 Efficient Scaling
The hash table can be expanded or contracted as needed, without the need
for rehashing.

5. Extendable Hashing Structure
Global Depth
Indicates the maximum
number of bits used to index
the directory.
Local Depth
Specifies the number of
significant bits used to index
each bucket.
Buckets
Data is stored in variable-
sized buckets, with the
number of buckets
dynamically adjusted.

6. Extendable Hashing Operations
Insertion
New data is hashed and stored in the appropriate bucket.
Splitting
Buckets are split when they reach capacity, updating the directory structure.
Searching
Data is efficiently located using the dynamic directory and bucket structure.

7. Advantages of Extendable Hashing
Scalability
Extendable hashing can
dynamically adapt to changes
in data volume.
Performance
Efficient data storage and
retrieval, with minimal collisions
and rehashing.
Flexibility
The hashing structure can be
easily adjusted to suit the data
distribution.

8. Conclusion and Applications
Extendable hashing is a powerful technique that addresses the limitations of traditional hashing. It has
wide-ranging applications in database management, caching systems, and other data-intensive domains
that require efficient and scalable data storage and retrieval.