What is rehashing?

Rehashing is the process of redistributing elements in a hash table when a certain load factor threshold is reached. Usually, when new elements are added to a hash table, if the number of elements becomes too large relative to the size of the bucket array, performance drops due to increased collisions.

To avoid this, a new larger array is created, and all existing elements are re-calculated (rehash) using a new hash function or the same algorithm but considering the new array size. This helps distribute elements more evenly and maintain the efficiency of insert, search, and delete operations.

In Go, for example, the built-in map automatically rehashes when necessary, which is hidden from the user.