Schema evolution is one of the trickiest aspects of database management. For developers and DBAs, the dreaded ALTER TABLE command often conjures fears of downtime, locks, and performance bottlenecks. But MySQL offers a powerful word! The "ALGORITHM" modifier that determines how schema changes are executed. In this article, we’ll break down the three key algorithms "INPLACE", "INSTANT", and "COPY" to help you understand their trade-offs, performance implications, and even some unconventional ways to use them. Whether you’re optimizing for zero downtime or experimenting with stress testing, this guide will give you practical insights and real-world strategies. IMPORTANT: Check your MySQL version: In MySQL 8.0+, many table changes are instantaneous, and the command modifications presented here are only available in this and later versions. Understanding the ALGORITHM Modifier When you run an ALTER TABLE in MySQL, you can specify the algorithm, lik...
Have you ever wondered why your database sorts strings differently than expected, or why a seemingly simple query delivers "quirky" results? If you’ve worked with databases like MySQL, PostgreSQL, or SQL Server, you’ve likely stumbled across the mysterious world of collation and the subtle but critical differences between VARBINARY and VARCHAR data types. In this article I hope to unravel these concepts for you, explore how collation shapes database behavior, and dive into an experimental case study to reveal surprising insights. Whether you’re a developer or a database engineer, this deep dive will equip you with practical knowledge to avoid common pitfalls and optimize your database designs. Let’s get started! What Is Collation and Why Does It Matter? Collation refers to the set of rules a database uses to compare and sort character strings. It governs how strings are ordered (e.g., is “Apple” less than “apple”?), how accents are treated (e.g., does “é” equal “e”?), and eve...