PostgreSQL Query Optimization with EXPLAIN ANALYZE
Tutorial on using EXPLAIN ANALYZE to identify slow queries and optimize them with proper indexing strategies.
Slow database queries were killing our API performance. EXPLAIN ANALYZE became my best friend for understanding what PostgreSQL was actually doing.
Step 1: Identify Slow Queries
Enable pg_stat_statements to log query execution times. Sort by total_time to find the biggest offenders. Often it's not the slowest query, but the moderately slow one called 1000x.
Step 2: Run EXPLAIN ANALYZE
EXPLAIN shows the plan, ANALYZE actually runs it. Look for Seq Scan on large tables (bad), high rows vs actual rows (bad stats), and nested loops with high row counts.
Step 3: Add Strategic Indexes
Create indexes on columns used in WHERE, JOIN, and ORDER BY. Partial indexes for filtered queries. Composite indexes for multi-column conditions. Run ANALYZE after.