Database Performance Debugging
Table of Contents
Overview
Database performance issues directly impact application responsiveness. Debugging focuses on identifying slow queries and optimizing execution plans.
When to Use
- Slow application response times
- High database CPU
- Slow queries identified
- Performance regression
- Under load stress
Quick Start
Minimal working example:
-- Enable slow query log (MySQL)
SET GLOBAL slow_query_log = 'ON';
SET GLOBAL long_query_time = 0.5;
-- View slow queries
SHOW GLOBAL STATUS LIKE 'Slow_queries';
SELECT * FROM mysql.slow_log;
-- PostgreSQL slow queries
CREATE EXTENSION pg_stat_statements;
SELECT mean_exec_time, calls, query
FROM pg_stat_statements
ORDER BY mean_exec_time DESC LIMIT 10;
-- SQL Server slow queries
SELECT TOP 10
execution_count,
total_elapsed_time,
statement_text
FROM sys.dm_exec_query_stats
ORDER BY total_elapsed_time DESC;
-- Query profiling
EXPLAIN ANALYZE
SELECT * FROM orders WHERE user_id = 123;
// ... (see reference guides for full implementation)
Reference Guides
Detailed implementations in the references/ directory:
| Guide | Contents | |---|---| | Identify Slow Queries | Identify Slow Queries | | Common Issues & Solutions | Common Issues & Solutions | | Execution Plan Analysis | Execution Plan Analysis | | Debugging Process | Debugging Process |
Best Practices
✅ DO
- Follow established patterns and conventions
- Write clean, maintainable code
- Add appropriate documentation
- Test thoroughly before deploying
❌ DON'T
- Skip testing or validation
- Ignore error handling
- Hard-code configuration values