Database-from-scratch

This project is a simple, persistent, single-file database implemented from scratch in C, inspired by SQLite. It features a command-line interface (REPL) and uses a B-Tree data structure for efficient data storage and retrieval.

Features

• Persistent Storage: The database is saved to a single file.
• B-Tree Implementation: Data is organized in a B-Tree to allow for efficient insertions and lookups, even as the database grows.
• REPL Interface: Interact with the database through a simple command-line shell.
• Basic SQL Commands:
  • insert <id> <username> <email>: Inserts a new record.
  • select: Retrieves and displays all records.
• Meta-Commands:
  • .exit: Exits the database shell, saving all changes to the file.
  • .constants: Displays the size of various data structures.
  • .visualize: Prints a visual representation of the B-Tree structure.

How to Build and Run

Prerequisites

• A C compiler, such as GCC.

Compilation

Navigate to the project directory and compile the source files using the following command:

gcc main.c -o db_executable

This will create an executable file named db_executable.

Running the Database

To start the database shell, run the compiled executable and provide a name for your database file. If the file does not exist, it will be created.

./db_executable my_database.db

You will then see the db > prompt, where you can enter commands.

Usage Example

Here is a sample session demonstrating the basic functionality:

$ ./db_executable test.db
db > insert 1 john john@example.com
db > insert 2 jane jane@example.com
db > insert 3 cstack cstack@example.com
db > select
id:1 ,Username:john, Email:john@example.com 
id:2 ,Username:jane, Email:jane@example.com 
id:3 ,Username:cstack, Email:cstack@example.com 
db > .visualize
Tree: 
- Internal (size 1)
  - leaf (size 2)
   - 1
   - 2
  - key 2
  - leaf (size 1)
   - 3
db > .exit
Database Closed Successfully.

Project Structure

• main.c: Contains the main function, the REPL (Read-Eval-Print Loop), and handles user input parsing.
• inputBuffer.h: The core of the database. It defines all data structures (Row, Pager, Table, Cursor), constants for node layouts, and implements all the logic for:
  • Serialization/Deserialization of rows.
  • Page management and file I/O (Pager).
  • B-Tree operations (insertion, searching, node splitting).
  • Statement preparation and execution.
• README.md: This documentation file.