When COMMIT is the slowest query, it means your storage is slow. Let’s look at an example.

Editors and technical reviewers suggested that I cover how to configure MySQL query metrics in chapter 1 of Efficient MySQL Performance, but I deferred because it was out of scope for the book, which focuses on engineers using MySQL, not DBAs. As such, there’s only a note in chapter 1 that says: “Ask your DBA or read the MySQL manual.” But I’ll cover the topic here because that’s what this blog post series is for: behind the book.

Let’s answer a question which, to my knowledge, has never been systematically addressed: What are the requirements for a production-ready query metrics app at scale? I am uniquely qualified to answer that because I have written four query metrics apps, two of which are the open-source standard for MySQL: pt-query-digest and the original (v1) code behind the query metrics/analysis part of Percona Monitoring and Management. I’ve also published a couple of packages related to query metrics: go-mysql/slowlog and go-mysql/query.