What is indexes in PostgreSQL?

In PostgreSQL, the index is a common way for database performance enhancement. It allows the database server to find the retrieve specific rows faster compared to without index. It also adds overhead to the database system as a whole, so users have to implement them sensibly.

Indexes are special lookup tables that are used by the database search engine to speed up data retrieval. Simply defining, an index is a pointer to a specific data in a table.