Learn the differences between MySQL’s copy and in‑place (online) DDL algorithms, how they manage locks, the steps of each process, the new Instant Add Column feature in MySQL 8, and practical strategies—including master‑slave switching—to safely alter tables in production.
This article explains MySQL's Instant Add Column feature, describing the traditional costly column‑addition process, the instant method’s internal mechanics, how data is read and written before and after the change, and the practical constraints that limit its usage.
The article recounts how Tencent Game DBA engineers contributed two core features—instant ADD COLUMN and large‑field compression—to MariaDB 10.3.2 Alpha, slashing a 12‑hour schema change to 0.04 seconds, earning public thanks from the MariaDB project and its founder Monty, and illustrating the impact of open‑source collaboration on high‑performance game databases.
