Dynamic Hashing

Definition of Dynamic Hashing

Dynamic hashing, also known as extendible hashing, is a data structure technique used in database management systems to efficiently handle growing or shrinking datasets. It involves the use of hash functions, which map search keys to specific data storage locations, while allowing the number of hash buckets to be increased or decreased as needed. This adaptability prevents excessive storage use and maintains search efficiency in varying data loads, ultimately providing better performance and flexibility.


The phonetics of “Dynamic Hashing” can be represented as:Dynamic: duh-ɪ-nam-ɪkHashing: ha-shɪŋ

Key Takeaways

  1. Dynamic Hashing automatically adjusts the storage size according to the number of keys, ensuring efficient use of storage and speedier lookups.
  2. It is adaptable to the changing input patterns, making it a suitable choice for databases and applications in which insertions, deletions, and retrievals are frequent and unpredictable.
  3. Two widely used techniques in Dynamic Hashing are Extendible Hashing and Linear Hashing, both of which enable reallocation of memory and redistribution of keys without the need to rehash all the keys in the table.

Importance of Dynamic Hashing

Dynamic hashing is an important technology term because it allows data structures to grow or shrink efficiently while maintaining a balanced distribution of key-value pairs across the hash table.

This adaptability ensures that the system can achieve optimal performance, as it automatically adjusts to accommodate increasing or decreasing data loads.

Furthermore, dynamic hashing eliminates the need to rehash the entire table when resizing, saving both processing time and computational resources.

Overall, dynamic hashing contributes to enhanced performance and flexibility in database systems and other applications that rely on efficient indexing and retrieval of data.


Dynamic Hashing, often employed in database management systems, plays a crucial role in ensuring efficient storage and retrieval of data. Its purpose is to optimize performance and minimize the response time of accessing records, allowing data to be managed proficiently even when the amount of stored data fluctuates.

The technique accomplishes this through adaptively modifying the hash function without the need for a complete rehashing process. One of the key benefits of dynamic hashing is the ability to handle the growth or decline in the size of a database, making it an ideal solution for systems with variable workloads and record counts.

Dynamic Hashing is commonly used to manage data in various applications such as distributed databases, file systems, content-addressable storage systems, and even caching in web servers. By utilizing consistent hashing or extendible hashing algorithms, this technique seamlessly accommodates the addition or removal of storage units or data buckets.

Consequently, it resolves the issue of uneven distributions, minimizes the probability of hash collisions, and ensures that the system continues to deliver optimal performance. Overall, dynamic hashing is a flexible and scalable technology that allows systems to manage their data effectively and respond to the ever-changing storage needs of today’s computing environments.

Examples of Dynamic Hashing

Database Management Systems: Many database management systems, such as PostgreSQL, MySQL, and Oracle, use dynamic hashing as part of their indexing strategy. This allows these systems to efficiently store, locate, and retrieve records, even as the size and contents of the database change. Dynamic hashing automatically resizes the hash table, avoiding excessive memory usage and ensuring that query performance remains consistent as the data grows.

Distributed Hash Tables (DHTs): Dynamic hashing is a crucial component of DHTs, which are used in distributed systems like peer-to-peer networks and content delivery systems. Examples of popular applications that use DHTs include the BitTorrent protocol for file-sharing and the InterPlanetary File System (IPFS). Dynamic hashing ensures that data is distributed evenly among participating nodes and helps the system adapt to changes, such as nodes joining or leaving the network.

Caching Systems: Caching solutions, such as Memcached and Redis, use dynamic hashing algorithms to distribute cached data among available cache servers. This evenly distributes the load and minimizes the likelihood of data “hotspots” or cache evictions. As cache servers are added or removed, dynamic hashing allows the caching system to reorganize its data, while minimizing the impact on overall performance.

Dynamic Hashing FAQ

1. What is dynamic hashing?

Dynamic hashing is a method used in databases and computer programming that allows the hash table to grow and shrink as necessary, adapting to the number of data items being stored. By avoiding the need to specify the size of the hash table ahead of time, storage and performance can be optimized as the data set evolves.

2. How does dynamic hashing work?

Dynamic hashing works by adjusting the hash functions used to calculate the positions of data items in the hash table based on the number of entries. As more items are added, the hash function may change, requiring the data to be redistributed into new positions within the table. Similarly, as data is removed, the table may shrink, and the data is rearranged to optimize storage and access.

3. What are the benefits of dynamic hashing?

Dynamic hashing offers several benefits, such as improved performance by automatically resizing the hash table to minimize collisions, reduced storage requirements by optimizing the table size for the data set, and not requiring the user to determine and specify the optimal hash table size in advance.

4. When should dynamic hashing be used?

Dynamic hashing is ideal for use cases where the number of data items to be stored and accessed is not known in advance or may change over time, such as databases that grow and shrink with data additions and deletions. It can also be useful for cases with fluctuating performance requirements, where data access speeds need to be optimized for shifting workloads.

5. Are there any drawbacks to using dynamic hashing?

Some potential drawbacks to using dynamic hashing include the increased complexity of the underlying implementation, the need to regularly recompute and redistribute data as the table evolves, and possible overhead costs associated with resizing and reorganizing the hash table. However, these trade-offs can be worth it in situations with unpredictable data volumes and the need for efficient storage and access.

Related Technology Terms

  • Load Factor
  • Rehashing
  • Extendable Hashing
  • Linear Hashing
  • Bucket Splitting

Sources for More Information


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