Thoughts on the new PERFORMANCE_SCHEMA in MySQL

Peter Gulutzan and Mark Leith have both written about the new PERFORMANCE_SCHEMA in MySQL. I’ve read through the worklog, or most of it – there were some spots where Firefox seemed to start overlaying parts with other parts, quite weird. But anyway I’ve read as much as I can.

Obviously many people have been putting a ton of thought into this for years, and I can’t pretend to judge their work in a single sitting. But I have opinions nevertheless.

If the implementation turns out to be as good as the initial swing at it looks, this is a great development. This is the way things should be done – this is, finally, the level of detail of instrumentation other databases have. There’s a lot of complexity; it is a large worklog and I can’t say whether it’s complete or something is put in the wrong place or will turn out to be not quite what’s needed; that’s where I stop trying to form an opinion. But overall, this is just a great development.

A few questions and comments, though.