database-performance-debugging

SKILL.md

Database Performance Debugging

Table of Contents

Overview

When to Use

Quick Start

Reference Guides

Best Practices

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

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