About the TiDB Source Code

The target audience of this document is the contributors in the TiDB community. The document aims to help them understand the TiDB project. It covers the system architecture, the code structure, and the execution process.

Adding Built-in Functions

This document describes how to add built-in functions to TiDB.

Subquery Optimization in TiDB

Subquery optimization, especially rewriting the correlated subquery, is a very difficult part in SQL query optimization. To be compatible with MySQL, TiDB enables users to write subqueries anywhere they want. For those subqueries that are not correlated, which are also called uncorrelated subqueries, TiDB evaluates in advance; for those correlated subqueries, TiDB removes the correlations as much as possible. For example, TiDB can rewrite a correlated subquery to `SemiJoin`. This article is focused on introducing the correlated subquery optimization methods in TiDB.


This document gives an overview of MVCC implementation in TiKV.

Travelling Back in Time and Reclaiming the Lost Treasures

This document introduces the History Read feature in TiDB.