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database-performance-debugging

Testing & Quality
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Debug database performance issues through query analysis, index optimization, and execution plan review. Identify and fix slow queries.

QUICK START

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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:

GuideContents
Identify Slow QueriesIdentify Slow Queries
Common Issues & SolutionsCommon Issues & Solutions
Execution Plan AnalysisExecution Plan Analysis
Debugging ProcessDebugging 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