Things you didn't know about indexes

A practical guide to database indexing covering both fundamentals and common pitfalls. Explains how indexes work (B-tree structure, binary search), the read-fast/write-slow trade-off, and storage costs. Covers four key gotchas and index types: composite index column ordering (left-prefix rule), function-wrapped columns breaking index usage, functional/expression indexes, partial indexes for low-cardinality or filtered data, and covering indexes (Index Only Scan) using PostgreSQL's INCLUDE clause. Uses a Pokémon table as a running example throughout, with EXPLAIN and EXPLAIN ANALYZE shown as diagnostic tools.