Xaprb » mysqluc2008

Baron Schwartz on a podcast at MySQL Conference and Expo 2008

Xaprb — Fri, 25 Apr 2008 13:35:15 +0000

I did an interview with Barton George from Sun while I was at the conference last week. Barton has now posted the interview. If you’re quick, you can listen to it before I do.

Topics: everything and anything, including Maatkit and PostgreSQL.

Further Reading:

MySQL Conference and Expo 2008, Day Three

Xaprb — Sat, 19 Apr 2008 05:22:31 +0000

Here’s a rundown of Thursday (day 3) of the MySQL Conference and Expo. This day’s sessions were much more interesting to me than Wednesday’s, and in fact I wanted to go to several of them in a single time slot a couple of times.

Inside the PBXT Storage Engine

This session was, as it sounds, a look at the internals of PBXT, a transactional storage engine for MySQL that has some interesting design techniques. I had been looking forward to this session for a while, and Paul McCullagh’s nice explanations with clear diagrams were a welcome aid to understanding how PBXT works. Unlike some of the other storage engines, PBXT is being developed in full daylight, with an emphasis on community involvement and input. (Indeed, I may be contributing to it myself, in order to make its monitoring and tuning capabilities second to none).

PBXT has not only a unique design, but a clear vision for differentiating itself from other transactional storage engines. It’s not trying to clone any particular engine; Paul and friends are planning to add some capabilities that will really set it apart from other engines, including high-availability features and blob streaming.

I left this session with a much better understanding of how PBXT balances various demands to satisfy all sorts of different workload characteristics, how it writes data, how it achieves transactional durability, and so on. I think these capabilities, and its performance, can really be assessed only in the real world (of course), but in principle it sounds good. I love knowing how things work!

There were about 30 people in the talk. I wish there had been more, because I think PBXT is going to be an important part of the open ecosystem going forward. However, I feel pretty confident people will take more notice if it starts to get used in the real world. Someone had a video camera there, so you might check out the video when it’s available. Paul’s explanations are really good.

Helping InnoDB Scale on Servers with Many CPU Cores and Disks

This session was Mark Callaghan’s chance to unveil the work he and others have been doing on InnoDB’s scalability issues, which mostly revolve around mutex contention. Mark’s team has completely solved the problems on their workload and benchmarks. In fact, after the changes, InnoDB exhibited significantly better performance even than MyISAM, which began to be limited by the single mutex that synchronizes access to its key cache. (Yes, in fact MyISAM has scalability problems too).

Google’s workload for MySQL, in case you’re wondering, is pretty traditional (i.e. not web-like; more like an “enterprise” application). Heavily I/O-bound, 24/7 critical systems, and so on.

Mark also wore several community t-shirts at various points in the talk, including one of my Maatkit t-shirts. Mark said Maatkit would be perfect if only it were written in Python (Google’s preferred scripting language). Alas, Mark, it’ll stay in Perl. But thanks for the nice compliment anyway.

The room was packed full.

Scaling Heavy Concurrent Writes In Real Time

Dathan Pattishall, formerly the lead architect at Flickr, explained his techniques for scaling Flickr’s write capacity. He talked about how he’d worked to reduce primary key sizes, queued writes for batching, separated different types of data into different types of tables, and more. Dathan has never been afraid to do what he thinks is a good idea, even if it flies in the face of “best practices,” so I was happy to finally hear him talk.

By the way, Dathan pointed out that distributed locking with memcached and add() isn’t a silver bullet. It works ok until memcached evicts your lock due to the LRU policy. He uses MySQL’s built-in GET_LOCK() function for locking.

Dathan’s blog is a good source of information about his sometimes unorthodox approaches to database design.

The Power of Lucene

This was the only one of Frank (Farhan) Mashraqi’s talks I got to attend. This was pretty technical: how Lucene works, how to configure and install it, how to index documents, how to execute searches. If you were wondering how much work and complexity it would be to install and use Lucene, this talk would have been good for you to attend; I’ve never used it myself, but I’m pretty sure Frank covered everything you need to know.

Further Reading:

MySQL Conference and Expo 2008, Day Two

Xaprb — Thu, 17 Apr 2008 17:01:02 +0000

Day two of the conference was a little disappointing, as far as sessions went. There were several time blocks where I simply wasn’t interested in any of the sessions. Instead, I went to the expo hall and tried to pry straight answers out of sly salespeople. Here’s what I attended.

Paying It Forward: Harnessing the MySQL Contributory Resources

This was a talk focused on how MySQL has made it possible for community members to contribute to MySQL. There was quite a bit of talk about IRC channels, mailing lists, and the like. However, the talk gave short shrift to how MySQL plans to become truly open source (in terms of its development model, not its license). I think there was basically nothing to talk about there. I had a good conversation about some of my concerns with the speaker and some others from MySQL right afterwards.

There was basically nobody there — I didn’t count, but I’d say maybe 10 or 12 people. I think this is a telling sign.

Architecture of Maria: A New Storage Engine with a Transactional Design

I was interested in this talk because I’m interested in the tension between Falcon and Maria (and between Falcon and everything, for that matter) but I left and went to the expo hall again after a bit. The talk was good but I’d already seen and/or read it, and the question-and-answer component wasn’t enough to keep me there.

The MySQL Query Cache

This was the second session I gave at the conference, and again it was standing-room-only, with nearly 300 attendees according to the person who was watching the door. The questions were frequent and added a lot to the discussion. Slides will be on the conference website when they post them.

Grazr: Lessons Learned Building a Web 2.0 Application Using MySQL

I was keenly interested in this talk because a) I am a big fan of Patrick Galbraith’s work with many different projects, and b) I had heard a lot about Grazr but didn’t know much about it. However, I missed most of the talk. About ten minutes into it, I got a call I couldn’t refuse: my wife!

However, I did sneak back into the room for the last bit too. And I gave Grazr a try. Unfortunately, I got really confused by it; I tried a bunch of different ways to import my Google Reader’s OPML. I got that to work, but then I couldn’t figure out how to read the feeds in the OPML via Grazr. Then I think I figured that out (I’m not sure) but it didn’t strike me as a very handy way to read my feeds. I’ll try taking another look at it later if I get time. (I’m all ears if there’s a better way to read feeds).

Extending MySQL

This one was mostly for fun. I knew a lot about UDFs already (I’ve created some) and I knew about the pluggable storage engine API. But I didn’t know about pluggable event daemons. Holy cow, what a great way to shoot yourself (or your server) in the foot! All the power of an atomic bomb, with all the safety of SPF 5 sunblock in a nuclear attack. Or something like that. But darn, it sure is nifty. Brian is a great speaker too — very lively.

You know, there’s another way to extend MySQL that most people don’t seem to know about, which Brian didn’t mention. That is procedures (not stored procedures). They are sort of like a post-filter for a result set, and like UDFs they’ve been around forever. I have never heard of anyone writing their own, but there’s an example in the server itself: PROCEDURE ANALYSE.

Expo hall

I went to the expo hall to meet and greet many of the companies that Percona (my employer) is already working with (doing independent benchmarks, performance verification, analysis etc) or will be in the future. I also wanted to grill some of the vendors on their technology. Usually I find them very cagey; they claim X times faster this-or-that, but won’t tell you how, and won’t tell you what their systems don’t do well. I don’t understand why they take this approach; you can’t hide your system’s strong and weak spots. There is no security through obscurity, and shrewd independent observers are going to get to the bottom of it with or without your permission.

So, for instance, I was talking with Tokutek, who claimed to be a drop-in replacement for InnoDB with 200x better performance and apparently no downsides. However, on closer questioning, I did get him to admit that the system has table-level locking. Thus it won’t give any concurrency, so saying it’s a drop-in InnoDB replacement is questionable. And the comparison against InnoDB seemed contrived to create a worst-case situation with bad tuning and a workload so it would perform terribly. An honest comparison tunes both systems to their highest performance and measures them; you can’t tune one system as badly as possible and compare it to the other’s best-case performance. I pressed on further and asked about range scans in some specific cases (they claim they’re great at range queries, and equal to InnoDB on everything else). At last they admitted they can’t perform well on some very common queries such as real-life queries InnoDB performs very well on for me. They said these are “point queries” but that’s not true; you can design indexes to support many different ways to range-query a table in InnoDB and get great performance. So it sounds to me like Tokutek’s storage format is extremely narrowly focused, and there is indeed a trade-off. I will be interested to see how their technology develops, though. It’s not done yet.

In general

There are a lot of Maatkit t-shirts walking around, which makes me happy. If I’d printed 200 of them, I probably could have given them all away. I was wearing a PostgreSQL t-shirt myself. Proudly, I might add. I’m not the only person here who’s interested in PostgreSQL. This morning I met a person from EnterpriseDB.

Yesterday was a bit slow in terms of interesting sessions, but there was a lot going on in the hallways, the expo hall, the meetings over lunch, and so on.

Further Reading:

Get a free sample chapter of High Performance MySQL Second Edition

Xaprb — Wed, 16 Apr 2008 05:56:20 +0000

If you’re at the MySQL Conference and Expo, you can get a free sample chapter of the upcoming High Performance MySQL Second Edition. Just go to the exhibition area. As you go through the doors, take an immediate left and look for the sample chapter on O’Reilly’s table. It’s a rough draft and contains typos and my incredibly crude drawings instead of those that will go into the final book, but it should serve to give you an idea of the book’s depth and scope. Kudos to Andy Oram, our editor, who was able to get these done for us on very short notice.

Further Reading:

MySQL Conference and Expo 2008, Day One

Xaprb — Wed, 16 Apr 2008 05:51:54 +0000

Today is the first day at the conference (aside from the tutorials, which were yesterday). Here’s what I went to:

New Subquery Optimizations in 6.0

By Sergey Petrunia. This was a similar session to one I went to last year. MySQL has a few cases where subqueries are badly optimized, and this session went into the details of how this is being addressed in MySQL 6.0. There are several new optimization techniques for all types of subqueries, such as inside-out subqueries, materialization, and converting to joins. The optimizations apply to scalar subqueries and subqueries in the FROM clause. Performance results are very good, depending on which data you choose to illustrate. The overall point is that the worst-case subquery nastiness should be resolved. I’m speaking of WHERE NOT IN(SELECT…) and friends. It remains to be seen how this shakes out as 6.0 matures, and what edge cases will pop up.

The Lost Art Of the Self Join

This was just great. Among many other things, Beat Vontobel showed how a Su Doku can be solved entirely with declarative queries: a very large self-join query against a table of digits and a table of the board’s initial state. I had been promoting this session because last year’s was so very good. I can’t wait to see what he comes up with for next year. Can he find another creative idea? Time will tell.

He wasn’t able to solve a 9×9 puzzle with MySQL because of the limitation on the number of joins, but PostgreSQL had no trouble doing it.

EXPLAIN Demystified

This was my session, of course. (Slides will be on the O’Reilly conference site, if they aren’t already). It went great, I thought. The room was full and people were standing in the back of the room and in the door. The questions came fast and furious; all really good questions. I think we ended up exploring a lot of the MySQL query execution method, strengths, and weaknesses by the time we were through. And I gave away all the remaining Maatkit t-shirts. Hopefully the people who took them will wear them tomorrow and the conference will be sea of deep, rich red shirts.

Someone did an audio recording of the session, but I don’t recall who it was.

Investigating InnoDB Scalability Limits

This session was given by Peter Zaitsev (disclosure: I now work for Percona, the company he co-founded). Peter and Vadim Tkachenko spent a lot of time over the last weeks and months running a dizzying array of benchmarks on MySQL 5.0.22, 5.0.51, and 5.1.24 (if I recall the versions correctly). They were able to show InnoDB’s scaling patterns for a number of different micro-benchmarks on a variety of configurations. If you didn’t attend, please look up the slides if you care about InnoDB performance. A lot of work went into the benchmarks — a lot of work. The slides should be on the conference website or on our blog, http://www.mysqlperformanceblog.com/.

Replication Tricks and Tips

Lars Thalmann and Mats Kindahl gave this session. At a high level, I’d say it was a run-down of all the different ways you can use MySQL replication. Replication is really a flexible tool, and they covered a large array of the most important ways you can use it to achieve different purposes. Many of the techniques they mentioned are implemented by various tools in Maatkit. A couple of the others are implemented in MySQL Master Master Manager and MySQL Semi Multi-Master tools. Don’t re-code these! You can save weeks of work and get quality code by using the pre-built tools. (I built Maatkit, so I know exactly how tricky it is to get some of these things right.)

BoF Sessions

I dropped in on a few BoF sessions, including the Sphinx one and the PBXT/Blob Streaming one. (Keep an eye on the PrimeBase folks — they are up to great things.) Ronald Bradford protected me from those who wanted to get me drunk. Hint: it’s really easy… I have to say, though, Monty’s black vodka was amazing.

Speaking of Blob Streaming, Paul McCullagh and I were talking earlier in the day about the project’s name, MyBS. This has been smirked about a few times. I think it’s a great name, because after all my initials are BS (I usually insert one of my four middle names in to alleviate this problem, but I digress). The conversation went like this:

Me: I like it. My initials are BS.

Paul: BS actually means British Standard, so it can’t be bad.

Me: Better than American Standard. That’s a toilet.

We also debated the merits of watching the original move The Blob. It’s a classic. It must be good.

Further Reading: