Do we use hash tables in practise?

Question

I just read about Hash tables and am curious if we use it in practise because if I write a program that stores data in a Hash table, the storage will only be temporary. So, why not use a database to store it ?

In other words, what kinds of real world programs use hash tables for their functioning?

Answer 1

You would use hash tables to store data while you are working. Using the database for that would in many cases be orders of magnitude slower then using in-memory hash tables. See for example:

• http://en.wikipedia.org/wiki/Caching

Hash maps are about speed, not persistence.

Take a look at the other uses in the Uses section of Hash table entry on Wikipedia:

• http://en.wikipedia.org/wiki/Hash_table