PostgreSQL EXPLAIN

Reading EXPLAIN Output

Execution Plan Nodes

Query Optimization Techniques

1. Index Optimization

2. Covering Indexes

3. Composite Index Column Order

4. Avoiding Functions on Indexed Columns

5. LIMIT Optimization

6. Pagination Optimization

7. Join Optimization

8. Subquery Optimization

9. SELECT * Considered Harmful

10. Batch Operations

Statistics and the Query Planner

How the Planner Works

Maintaining Statistics

Advanced Optimization

Partitioning for Query Performance

Materialized Views for Complex Queries

Query Plan Caching (Prepared Statements)

Optimization Checklist

• Run EXPLAIN (ANALYZE) on slow queries
• Check for Seq Scans on large tables
• Verify index usage
• Check row estimates vs actual rows
• Look for high "Rows Removed by Filter"
• Ensure statistics are up to date (ANALYZE)
• Review JOIN order and types
• Check for functions on indexed columns
• Verify LIMIT/OFFSET usage
• Consider covering indexes for common queries
• Review SELECT * usage
• Check for N+1 query patterns
• Consider materialized views for reports
• Review connection pooling settings

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