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SQLid Database Engine

File-based SQL database engine written in C++ from scratch

Core Philosophy

SQLid builds on one fundamental principle: ID is everything. Unlike traditional databases where ID is just another column, in SQLid:

  • ID is built-in - Exists in every table by design
  • Zero storage cost - O(0) memory overhead
  • Always returned - Every operation reveals affected IDs
  • Non-creatable - ID emerges from system, not user input

Why "SQLid"?

The name reflects architecture:

  • SQL - Full SQL support with complex queries
  • id - ID-centric design where identifiers drive everything

SQLid Performance (12k records)

Operation Time (10k operations) Time per query
Full scan (O(n)) 59.8 sec ~6.0 ms
Index search (O(1)) 1.0 sec ~0.1 ms
Range query (O(m)) 1.2 sec ~0.12 ms
Insert (O(1)) 0.9 sec ~0.09 ms

Indexed search acceleration: 60x

Asymptotic Performance

Operation Complexity Description
Single Insert O(1) Hash-based indexing
Batch Insert O(k) k = batch size
Direct Search O(1) By primary key (ID)
Range Query O(m) m = range size
Full Scan O(n) n = total records

Read asymptotics.md for more info

Features

  • Full SQL Support - SELECT, INSERT, UPDATE, DELETE with complex WHERE clauses and ORDER BY
  • Multi-Threaded - Concurrent access with stripe-based locking
  • File-Based Storage - Direct file operations with memory mapping
  • Network API - Remote connections via TCP/IP
  • Backup System - Database backup and restore functionality
  • Cross-Platform - Works on Windows and Linux

Quick Start

Server:

cmake .. -DCMAKE_CXX_STANDARD=23 
make -j4
./SQLid [port] [working_path]
OR
./SQLid
# Set wanted port using console
# Set wanted path using console

Client:

SQLid_API api(boost_contex, ip, port);
api.connect();

auto result = api.request(SQL_command); //Work with database

Look for examples/ on 'ImGuiDemo' branch for more info

SQL Examples:

CREATE DATABASE mydb
CREATE TABLE FOR mydb users name STRING[32] age INT32
ATTACH TO mydb
INSERT INTO users "John" 25
SELECT * FROM users WHERE age > 20
SELECT * FROM users LIMIT 10 ORDER BY name DESC age ASC
UPDATE users SET age = 26 WHERE id == 1
DELETE FROM users WHERE name == "John"

Read documentary.md for more info

Technical Details

  • Language: C++23
  • Storage: Offset-based file system
  • Concurrency: Stripe locking (128 segments)
  • Networking: Boost.Asio
  • SQL Parser: Custom recursive descent parser

Project Structure

src/
	files/          # Database engine
	clients/        # TCP server/client
	parser/         # SQL parser
	data_base/      # Command execution
	exception/      # Exceptions that can be throwed
	result/         # Result class
	system/         # Control databases
include/
	SQLid_API.h	    # Api for distant work

Supported Types

  • Integers: INT32, INT64
  • Floats: FLOAT, DOUBLE
  • Strings: STRING[N], TEXT
  • Boolean: BOOL