ToyDB is a distributed SQL database that provides a system for storing and querying data across multiple nodes. It focuses on maintaining strong consistency and fault tolerance through the implementation of a distributed consensus algorithm.
The project distinguishes itself by supporting historical data versioning, enabling time-travel queries to retrieve the state of the database from a specific point in the past. It utilizes multi-version concurrency control to manage ACID transactions and ensure data integrity during concurrent operations.
The system covers relational data modeling with table schemas, primary keys, and foreign keys to enforce referential integrity. Its query engine parses SQL statements and executes them through an optimized pipeline of operators, supporting joins, aggregations, and heuristic query optimization. Data is persisted via pluggable storage backends, including log-structured and in-memory engines.
