GrayDB

⚙️ Lightweight, embeddable, modular database engine written in pure C — built from scratch, with B+ Trees, hash tables, and a custom query DSL.

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🚀 Overview

GrayDB is a minimal, high-performance embedded database engine written entirely in C. Inspired by the architectural simplicity of SQLite and the modular power of PostgreSQL internals, it uses its own memory-efficient B+ Tree index, open-addressing Hash Table, and a small, expressive domain-specific language (DSL) for querying.

GrayDB is designed for learning, extensibility, and experimentation, without sacrificing performance or elegance.

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🔧 Features

• 📁 B+ Tree Indexing
  Fast insertion, deletion, and range queries with balanced tree structure.

• 🧠 Open Hash Table
  Used internally for symbol resolution and future metadata support.

• 🧵 Multithreading-ready
  Uses pthread and semaphores for concurrency (planned: lock-free optimizations).

• 🗃️ Table Abstraction
  Tables support dynamically-typed columns and are represented as nodes in the index tree.

• 💬 Custom DSL Parser
  Lightweight SQL-inspired syntax: create table, insert into, select * from, etc.

• 🔣 REPL CLI Interface
  With readline integration for history and interactive queries.

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🧱 Architecture

src/             # Source code
└── main.c       # Entry point
└── cli.c        # Interface & REPL
└── dsl.c        # DSL parser and dispatch
└── table.c      # Logical tables and schema
└── ds.c         # Core data structures (B+ tree, hash table)
└── crypt.c      # (Planned) data encryption layer
include/
├── \*.h         # All headers and interfaces

• 🌳 B+ Tree: Manages index nodes and supports efficient lookup, split, and rebalance operations.
• 🔐 Hash Table: Used for internal mappings and planned query caching.
• 🗂️ Table Layer: Maps columnar data to key-value entries in the B+ Tree.

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🛠️ Usage

Build

gcc -o graydb src/main.c src/cli.c src/dsl.c src/ds.c src/table.c -Iinclude -lreadline

Run

./graydb

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💻 Example

  .g8'''bgd  `7MM'''Mq.        db      `YMM'   `MM'`7MM'''Yb.   `7MM'''Yp,
.dP'     `M    MM   `MM.      ;MM:       VMA   ,V    MM    `Yb.   MM    Yb
dM'       `    MM   ,M9      ,V^MM.       VMA ,V     MM     `Mb   MM    dP
MM             MMmmdM9      ,M  `MM        VMMP      MM      MM   MM'''bg.
MM.    `7MMF'  MM  YM.      AbmmmqMA        MM       MM     ,MP   MM    `Y
`Mb.     MM    MM   `Mb.   A'     VML       MM       MM    ,dP'   MM    ,9
  `'bmmmdPY  .JMML. .JMM..AMA.   .AMMA.   .JMML.   .JMMmmmdP'   .JMMmmmd9

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Welcome to GrayDB:
>> create table users
>> insert into users values (1, "Miguel", 19)
>> select * from users where id = 1
>> delete from users where id = 1
>> exit

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📚 DSL Commands (in progress)

Command	Description
create table <name>	Creates a new table
insert into <name>	Inserts a new row
select * from <name>	Fetches all data (soon with filters)
delete from <name>	Deletes a row by primary key
clear	Clears the terminal
exit	Exits the REPL

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🎯 Roadmap

• B+ Tree with split and rebalance
• Hash table with open addressing
• Table schema and metadata
• DSL parser with REPL
• DSL: typed columns in CREATE
• INSERT with real values
• File-based persistence
• Query optimization engine
• Built-in cryptography with AES
• FOX (comming soon procedural language)

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🧠 Author

Miguel Araújo Julio Computer Science student

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📜 License

MIT License. Free for use, study, and modification.

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🤝 Contribute

GrayDB is a solo project, but open to collaboration. If you're into compilers, OS dev, or low-level systems — feel free to fork and explore!