What indexes are available in PostgreSQL?

PostgreSQL offers the following index types:

• B-tree — the most common type, suitable for most comparison operations (=, <, >, BETWEEN).
• Hash — for fast equality searches, but less versatile and used less frequently.
• GIN (Generalized Inverted Index) — for indexing arrays, JSONB, full-text search.
• GiST (Generalized Search Tree) — for complex data structures, such as geometric objects, full-text search.
• SP-GiST (Space-partitioned GiST) — for specific data structures, such as points, grids.
• BRIN (Block Range Index) — for very large tables with ordered data, saves space.

Each index type is suitable for different tasks and data types; the choice depends on the nature of queries and data structure.