How Does a Database Work?

This project is a Java implementation of cstack’s original db tutorial project in C. The Java code here is purely educational, but feel free to propose relevant enhancements.

• What format is data saved in? (in memory and on disk)
• When does it move from memory to disk?
• Why can there only be one primary key per table?
• How does rolling back a transaction work?
• How are indexes formatted?
• When and how does a full table scan happen?
• What format is a prepared statement saved in?

In short, how does a database work?

I’m building a clone of sqlite from scratch in C in order to understand, and I’m going to document my process as I go.

Table of Contents

• Part 1 - Introduction and Setting up the REPL
• Part 2 - World’s Simplest SQL Compiler and Virtual Machine
• Part 3 - An In-Memory, Append-Only, Single-Table Database
• Part 4 - Our First Tests (and Bugs)
• Part 5 - Persistence to Disk
• Part 6 - The Cursor Abstraction
• Part 7 - Introduction to the B-Tree
• Part 8 - B-Tree Leaf Node Format
• Part 9 - Binary Search and Duplicate Keys
• Part 10 - Splitting a Leaf Node
• Part 11 - Recursively Searching the B-Tree
• Part 12 - Scanning a Multi-Level B-Tree
• Part 13 - Updating Parent Node After a Split

“What I cannot create, I do not understand.” – Richard Feynman

sqlite architecture (https://www.sqlite.org/arch.html)