PostgreSQL Performance Skill

Atomic skill for query optimization

Overview

Production-ready patterns for EXPLAIN analysis, index design, and configuration tuning.

Prerequisites

• PostgreSQL 16+
• pg_stat_statements extension

Parameters

parameters:
  operation:
    type: string
    required: true
    enum: [analyze_query, create_index, tune_config, diagnose]
  target_time_ms:
    type: integer
    default: 100

Quick Reference

EXPLAIN Commands

EXPLAIN (ANALYZE, BUFFERS) SELECT * FROM users WHERE email = 'test@example.com';

Index Types

Use Case	Type	Example
Equality	B-tree	CREATE INDEX idx ON t(col)
JSONB	GIN	USING GIN(data jsonb_path_ops)
Time-series	BRIN	USING BRIN(created_at)

Key Metrics

Metric	Healthy	Warning
Seq Scan rows	< 10K	> 100K
Buffer hit	> 99%	< 95%
Planning time	< 10ms	> 100ms

Diagnostic Queries

-- Slow queries
SELECT query, mean_exec_time FROM pg_stat_statements ORDER BY mean_exec_time DESC LIMIT 10;

-- Unused indexes
SELECT indexrelname, idx_scan FROM pg_stat_user_indexes WHERE idx_scan = 0;

-- Table bloat
SELECT tablename, n_dead_tup FROM pg_stat_user_tables WHERE n_dead_tup > 10000;

Troubleshooting

Problem	Cause	Solution
Seq Scan	Missing index	Create index
High buffer reads	Cold cache	Increase shared_buffers
Wrong estimates	Stale stats	Run ANALYZE

Usage

Skill("postgresql-performance")