What types of indexes exist in PostgreSQL and which one is the most common?

In PostgreSQL, there are several types of indexes, each optimized for different tasks:

• B-tree — the most common and versatile index type. Suitable for most comparison operations (=, <, <=, >, >=) and sorting.
• Hash — used for fast equality searches, but less versatile and less frequently used.
• GIN (Generalized Inverted Index) — effective for indexing arrays, JSONB, full-text search.
• GiST (Generalized Search Tree) — supports complex data structures, such as geometric objects.
• SP-GiST — a specialized GiST for certain structures, such as prefix trees.
• BRIN (Block Range Index) — a compact index for large tables with physically ordered data.

The most common and versatile is the B-tree index. It is used by default when creating indexes and covers most typical search and sorting scenarios.