Dynamic Hashing

Definition of Dynamic Hashing

Dynamic hashing is a technique used in data management to efficiently store and retrieve data in a hash table by adjusting its size dynamically. This method allows the hash table to expand or shrink as the amount of data changes, ensuring optimal utilization of storage space and reducing search time. By using dynamic hashing, the system maintains a balanced load factor to prevent performance issues associated with static hashing, such as excessive collisions and wasted memory.


The phonetic pronunciation of “Dynamic Hashing” is: dʌɪˈnæmɪk ˈhæʃɪŋ- “Dynamic”: dʌɪˈnæmɪk- “Hashing”: ˈhæʃɪŋ

Key Takeaways

  1. Dynamic Hashing automatically adjusts the size of the hash table based on its load, ensuring efficient use of memory and maintaining optimal search/insertion times.
  2. It employs various techniques such as incremental resizing, directory-based approach, and extendible hashing to handle growth and shrinkage of data without requiring massive rehashing.
  3. Dynamic Hashing prevents degradation of performance due to high load factors and is particularly useful in database management systems, distributed systems, and other applications dealing with dynamic and unpredictable data sets.

Importance of Dynamic Hashing

Dynamic hashing is an essential technology term as it addresses the challenge of efficiently managing and accessing data in computer systems.

By allowing the hash table to expand and contract based on the volume of data stored, this technique significantly improves the performance and resource utilization of data structures.

This approach ensures an optimal distribution of key-value pairs and minimizes the risk of collisions while maintaining a constant load factor, greatly enhancing search, insertion, and deletion operations.

Consequently, dynamic hashing contributes to the agility of databases and other applications in meeting the ever-evolving and dynamic data storage needs of modern computing environments.


Dynamic Hashing, also known as extendable hashing, is an advanced data structure technique used to manage, organize, and quickly access data in databases and file systems. The primary purpose of this method is to overcome the limitations of static hashing by allowing the hash table to grow or shrink dynamically based on the number of elements or records in the database. This adaptive nature of dynamic hashing makes it particularly suitable for databases and applications that require efficient allocation of resources and high scalability in response to fluctuating data sizes.

One of the key benefits of dynamic hashing lies in its ability to minimize the time taken for searching and accessing records in a database. This is achieved through the use of a directory or an index structure that points to the actual data or the hash buckets. The address spaces in the directory are dynamically divided, and an algorithm is used to determine the appropriate bucket for each incoming record.

When the data load becomes too high, resulting in the potential for performance degradation, the system automatically increases the number of buckets and redistributes the records evenly among them. Conversely, when there is a decrease in the amount of data, the system can automatically merge and reduce the number of buckets to conserve resources. This adaptability not only ensures optimal utilization of memory but also maintains consistent performance, even as the number of data elements fluctuates over time.

Examples of Dynamic Hashing

Database Management Systems: Dynamic hashing is commonly implemented in database management systems (DBMS) to ensure effective storage and retrieval of data records. As the database grows or shrinks, dynamic hashing adjusts the size of the hash table accordingly. This strategy helps maintain a balance between achieving fast searches and minimizing storage overhead. For example, DBMS like PostgreSQL and MongoDB often use dynamic hashing techniques to store and retrieve records efficiently.

Caching Mechanisms and Content Delivery Networks: Content Delivery Networks (CDNs) such as Cloudflare and Akamai use dynamic hashing to effectively distribute and store web content across their servers. This method helps them serve content efficiently to numerous users without incurring as many cache misses (which could lead to slower load times). For instance, when a frequently accessed web page is requested, the CDN server would calculate its hash value using dynamic hashing and distribute the content efficiently among its nodes.

Distributed File Systems: Dynamic hashing plays a vital role in handling file storage, replication, and retrieval in distributed file systems like Google File System (GFS) and Hadoop Distributed File System (HDFS). Through dynamic hashing, these systems can manage and allocate storage locations across multiple nodes efficiently, making it easier to store and access large datasets required for big data processing operations.

FAQ – Dynamic Hashing

1. What is dynamic hashing?

Dynamic hashing is an advanced hashing technique that adapts its hash table size in response to changes in the number of stored elements. This allows it to maintain constant performance and minimize the chances of hash collisions. Unlike static hashing, dynamic hashing automatically grows and shrinks its hash table size to accommodate data and optimize efficiency.

2. How does dynamic hashing work?

Dynamic hashing works by allocating additional memory for the hash table as needed and rehashing the stored elements to distribute them across the new structure. When the load factor, which is the ratio of stored elements to the total table size, reaches a specific threshold, dynamic hashing increases the table size. Conversely, if the load factor falls below a lower threshold, the table size decreases.

3. What are the benefits of dynamic hashing?

Some advantages of dynamic hashing include constant performance during data insertion or deletion, minimized chances of hash collisions, adaptability to a varying number of elements, and efficient memory usage. This technique provides a scalable and effective hashing method for large databases and real-time systems that require constant optimization.

4. When is dynamic hashing appropriate to use?

Dynamic hashing is suitable for situations where the number of stored elements frequently changes, and constant performance is crucial. Examples include large databases, real-time systems, search engines, and distributed systems where the data storage requirements may increase or decrease over time.

5. How does dynamic hashing compare to other hashing techniques?

Dynamic hashing is more flexible and adaptive than static hashing or chained hashing, as it adjusts the table size for optimal performance. While static hashing requires a fixed table size and suffers from poor performance during hash collisions, dynamic hashing ensures a consistent load factor that reduces the chances of collisions. However, dynamic hashing may require more processing overhead for rehashing and memory allocation compared to other hashing techniques.

Related Technology Terms

  • Load Factor
  • Directory Expansion
  • Collision Resolution
  • Rehashing
  • Extendible Hashing

Sources for More Information

Technology Glossary

Table of Contents

More Terms