This isn’t actually new — it has been out for a few releases. The mk-query-digest tool from Maatkit now outputs information about each class of queries’ variance-to-mean ratio. The new output goes in a couple of places, including perhaps most usefully the “profile” report. Here’s an example from a real MySQL system:

# Profile
# Rank Query ID           Response time    Calls R/Call Apdx V/M   Item
# ==== ================== ================ ===== ====== ==== ===== =======
#    1 0xBFCF8E3F293F6466 11256.3618 68.1% 78069 0.1442 1.00  0.21 SELECT [redacted]
#    2 0x620B8CAB2B1C76EC  2029.4730 12.3% 14415 0.1408 1.00  0.21 SELECT [redacted]
#    3 0xB90978440CC11CC7  1345.3445  8.1%  3520 0.3822 1.00  0.00 SHOW STATUS
#    4 0xCB73D6B5B031B4CF  1341.6432  8.1%  3509 0.3823 1.00  0.00 SHOW STATUS
# MISC 0xMISC               560.7556  3.4% 23930 0.0234   NS   0.0 <17 …

The most efficient performance optimization of a SQL statement is to eliminate it. Cary Millsap’s recent Kaleidoscope presentation again highlighted that improving performance is function of code path. Removing code will improve performance.

You may think that it could be hard to eliminate SQL, however when you know every SQL statement that is executed in your code path obvious improvements may be possible. In the sequence SQL was implemented sometimes easy observations can lead to great gains. Let me provide some actual client examples that were discovered by using the MySQL General Log.

Example 1

5 Query   SELECT *  FROM `artist`
5 Query   SELECT *  FROM `artist`
5 Query …

Guerrilla Capacity Planning

Guerrilla Capacity Planning. By Neil J. Gunther, Springer 2007. Page count: about 200 pages, plus appendixes. (Here’s a link to the publisher’s site.)

Of all the books I’ve reviewed, this one has taken me the longest to study first. That’s because there is a lot of math involved, and Neil Gunther knows a lot more about it than I do. Here’s the short version: I’m learning how to use this in the real world, but that’s going to take many months, probably years. I’ve already spent about 10 months studying this book, and …

Cary Millsap has a concise, readable paper on performance. Anyone involved in database performance optimization should read it. Cary’s writing has heavily influenced the mk-query-digest tool for analyzing MySQL/PostgreSQL/Memcached/HTTP query performance, and I think you’ll get a lot more from mk-query-digest if you read this paper — and you should also read his book, reviewed here. It’s one of the top books on my Essential Books List.

Related posts:

1. …

Optimizing Oracle Performance by Cary Millsap and Jeff Holt uses Oracle to make its points, but these points apply also to MySQL. The primary lesson I took away from this book is: all else aside, optimize/fix the user-action that provides the most economic benefit to the company; do this by profiling just that action and optimizing/fixing the most time-consuming events even if they are “idle” or “wait” events.

The authors call the aforementioned approach to performance optimization “Method R”. It’s meant to be deterministic and teachable unlike “Method C”–the conventional method–whereby one uses their best judgment and experience to find the cause(s) of problems and fix them. I agree, and Method R is fundamentally, imho, just the scientific method in practice. Therefore, I like Method R because it puts “science” back into “computer science.” …

The best overall method of performance optimization is optimization for response time. Users care about response time, not load average or cache hit ratios. The job of a system is to accept some request and do the required work, and deliver a result. The time elapsed between the request and the result is the response time.

Methods of Response Time Optimization

Not all optimization methods are created equal. Here are a few I see commonly.

• No method. Most people simply have no method of performance optimization at all. They just look for things that look “bad” and try to make them look “better.” In the MySQL database world, the classic example is trying to improve a cache hit ratio. This is utter folly, and doesn’t become any less stupid no matter how many times it is taught and repeated.
• Server Load Reduction. One step up from that is to try …

Optimizing Oracle Performance

Optimizing Oracle Performance. By Cary Millsap, O’Reilly 2003. Page count: about 375 pages with appendices. (Here’s a link to the publisher’s site.)

This is easily one of the best books I’ve ever read on performance optimization. I’ve just finished reading it for the second-and-a-half time in two weeks, and I very rarely read a book more than once. I’ve been telling a lot of people about it.

Despite the title, it is actually not about Oracle performance. It is a book on how to optimize a) any system, …

Having written about what I think is cool about the upcoming MySQL Conference and the MySQL Camp, now I want to finish up with what I’d like to see at the Percona Performance Conference. Just to recap, this is a conference we created to serve those who want to learn about performance — not “learn about MySQL,” not “learn about database performance,” just learn about performance, period.

I want to see everything. I think this is going to be the single best conference I’ve ever been to. Even the way the conference is organized is exciting. For example, it’s running from early morning till late at night, nonstop. The sessions are also (mostly) only 25 minutes. This means if you decide a session isn’t all that interesting, you didn’t spend much time on it, and you don’t have long to wait for the next one.

So here is a small sample of the …