Designing the Right PostgreSQL Index Using Query Plans and Statistics

Short summary

PostgreSQL composite index optimization requires: (1) equality predicates before range predicates, (2) most-selective equality columns first, (3) range predicates last. Execution plans reveal whether an index is actually used—many theoretically good indexes don't improve performance because PostgreSQL prefers sequential scans. pgAssistant automates proper design using statistics and query plans.

• •Equality predicates must come before range predicates in B-Tree indexes for efficient navigation
• •Order equality columns by selectivity (n_distinct) to reduce search space earliest
• •Always check EXPLAIN ANALYZE—PostgreSQL may prefer sequential scans over theoretically perfect indexes on small tables

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