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doc_id DBS-PERF-009
doc_title Database System Performance Tuning Guide
doc_version 1.0.0
doc_date 2026-04-04
doc_status Released
project database_system
category PERF

Database System Performance Tuning Guide

SSOT: This document is the single source of truth for Database System Performance Tuning Guide.

Overview

This guide provides comprehensive performance tuning recommendations for the Database System across different backends and use cases.

Backend Selection Guide

Workload Characteristics Matrix

Workload Type Recommended Backend Rationale
Read-heavy OLTP PostgreSQL Superior indexing, parallel queries
Write-heavy OLTP PostgreSQL Strong WAL-based throughput and mature operational tooling
Embedded/Local SQLite Zero configuration, in-process
Complex Analytics PostgreSQL Advanced query planner
Simple Key-Value SQLite Minimal overhead

Backend Performance Comparison

Benchmark: 10,000 mixed operations (70% read, 30% write)

PostgreSQL:  850 ops/sec  (best for complex queries)
SQLite:     1200 ops/sec  (best for embedded use)

Connection Pool Tuning

Pool Size Formula

Optimal Pool Size = (Core Count * 2) + Effective Spindle Count

For SSD-based systems:

Optimal Pool Size = Core Count * 2 + 1

Configuration Example

#include <database/core/database_backend.h>

core::connection_pool_config pool_config;
pool_config.min_connections = 5;     // Minimum warm connections
pool_config.max_connections = 20;    // Maximum connections
pool_config.connection_timeout = std::chrono::seconds(30);
pool_config.idle_timeout = std::chrono::minutes(5);
pool_config.validation_interval = std::chrono::seconds(30);

Pool Size Recommendations

Use Case Min Connections Max Connections
Development 1 5
Small Application 2 10
Medium Application 5 20
High Traffic 10 50

Query Optimization

General Principles

  1. Use Prepared Statements
// Good: Parameterized query
auto stmt = db->prepare("SELECT * FROM users WHERE id = ?");
stmt->bind(1, user_id);
auto result = stmt->execute();

// Avoid: String concatenation
auto result = db->select_query("SELECT * FROM users WHERE id = " + user_id);
  1. Limit Result Sets
// Good: Limit results
auto result = db->select_query("SELECT * FROM logs LIMIT 100");

// Avoid: Unbounded queries
auto result = db->select_query("SELECT * FROM logs");
  1. Select Only Required Columns
// Good: Specific columns
auto result = db->select_query("SELECT id, name FROM users");

// Avoid: SELECT *
auto result = db->select_query("SELECT * FROM users");

Backend-Specific Tuning

PostgreSQL

Key Settings:

-- Connection settings
max_connections = 100
shared_buffers = 256MB        -- 25% of RAM
effective_cache_size = 768MB  -- 75% of RAM
work_mem = 4MB

-- Write performance
wal_buffers = 16MB
checkpoint_completion_target = 0.9

Index Strategy:

  • Use B-tree for equality and range queries
  • Use GIN for full-text search
  • Use BRIN for large, naturally ordered tables

See Also

  • POSTGRESQL_TUNING.md
  • SQLITE_TUNING.md
  • BENCHMARKS.md - Performance benchmark results