What are indexes in PostgreSQL and what types exist?

Indexes in PostgreSQL are needed to speed up searching and data retrieval from tables. Without indexes, the DBMS has to scan the entire table, which is slow with large volumes of data.

Main types of indexes in PostgreSQL:

• B-tree — the most common type, suitable for most comparison operations (=, <, >, BETWEEN).
• Hash — optimized for equality operations, but less versatile.
• GIN (Generalized Inverted Index) — used for indexing arrays, JSON, full-text search.
• GiST (Generalized Search Tree) — for complex data structures, such as geometric objects.
• SP-GiST — specialized index for non-standard data structures.
• BRIN (Block Range Index) — effective for very large tables with ordered data.

Example of creating a B-tree index:

CREATE INDEX idx_users_email ON users(email);

Indexes significantly improve query performance but require additional space and affect insert/update speeds.