Lock-Free Hash

Tencent Database Technology

Nov 24, 2017 · Databases

MySQL Metadata Lock (MDL): Usage, Implementation, Deadlock Detection, and Lock‑Free Optimizations

This article explains MySQL's Metadata Lock (MDL) subsystem, describing how MDL protects metadata, the lock types and modes, the transaction‑level implementation introduced in MySQL 5.5 and refined in 5.7, the lock acquisition and release algorithms, deadlock detection mechanisms, and the lock‑free hash table used to store lock objects.