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SQL Locking and Transactions – OSDC 2011 video

Open Query — Thu, 24 Nov 2011 02:10:30 +0000

This recent session at OSDC 2011 Canberra is based on part of an Open Query training day, and (due to time constraints) without much of the usual interactivity, exercises and further MySQL specific detail. People liked it anyway, which is nice! The info as presented is not MySQL specific, it provides general insight in how databases implement concurrency and what trade-offs they make.

See http://2011.osdc.com.au/sqll for the talk abstract.

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Why do I recommend switching over from MyISAM to Innodb!

Ovais Tariq — Tue, 16 Nov 2010 11:47:33 +0000

Although MyISAM has been the default storage engine for MySQL but its soon going to change with the release of MySQL server 5.5. Not only that, more and more people are shifting over to the Innodb storage engine and the reasons for that is the tremendous benefits, not only in terms of performance, concurrency, ACID-transactions, foreign key constraints, but also because of the way it helps out the DBA with hot-backups support, automatic crash recovery and avoiding data inconsistencies which can prove to be a pain with MyISAM. In this article I try to hammer out the reasons why you should move on to using Innodb instead of MyISAM.
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A growing trend: InnoDB mutex contention

Baron Schwartz (xaprb) — Thu, 04 Mar 2010 05:51:01 +0000

I’ve been noticing an undeniable trend in my consulting engagements in the last year or so, and when I vocalized this today, heads nodded all around me. Everyone sees a growth in the number of cases where otherwise well-optimized systems are artificially limited by InnoDB contention problems.

A year ago, I simply wasn’t seeing the need for analysis of GDB backtraces en masse. These days, I’m writing custom tools to gather and analyze backtraces. A year ago, I simply looked at the SEMAPHORE section of SHOW INNODB STATUS. These days I’m writing custom tools to aggregate and reformat that data so I can interpret it more easily. And I’m actually seeing cases of this type of problem multiple times every week. I remember the first time I ran into a server that was literally optimized to the limit, but struggling under the load. It was something new for me, not that long ago. Oh, I’d seen it before, plenty, but was always able to point out where something could be improved without changing InnoDB itself. Now it’s commonplace: schemas are fine — check. Queries are all well-indexed — check. Everything else — check. InnoDB is bottlenecked and absolutely nothing can be improved — check.

Part of the difference is the rapidly improving hardware. It’s getting hard to buy a server with fewer than 8 or even 16 cores, and 16GB of RAM feels like something I’d install in a wristwatch. But I also suspect that if I’d been characterizing the workload of servers over time in a way that was easy to compare, I’d see a clear trend towards bigger data and more queries per second. We’re just pushing MySQL + InnoDB harder today than we ever have before.

What can be done? Well, InnoDB needs to be improved, that’s all. Oracle, Percona, Google, Facebook and others are working on it, and in many cases these efforts have yielded dramatic results. But there is still much room for improvement.

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MySQL University: Concurrency Control: How It Really Works

Stefan Hinz — Wed, 23 Sep 2009 09:49:02 +0000

This Thursday (September 24th, 14:00 UTC), Heikki Tuuri, the father of InnoDB, will give a session on Concurrency Control: How It Really Works. He'll describe how InnoDB manages concurrency control, so that the system protects data integrity. Beginning with the basics of transaction management, Heikki will include a discussion of the ACID (atomicity, consistency, isolation, and durability) properties, and explain various transaction modes, locking, deadlocks, and more advanced topics such as the impact of next-key (gap) locking, referential integrity, XA (distributed transaction management) support, and more. While the discussion will focus on the InnoDB implementation, many of the concepts presented apply to other database systems and storage engines.

For MySQL University sessions, point your browser to this page. You need a browser with a working Flash plugin. You may register for a Dimdim account, but you don't have to. (Dimdim is the conferencing system we're using for MySQL University sessions. It provides integrated voice streaming, chat, whiteboard, session recording, and more.) All MySQL University sessions are recorded, that is, slides and voice can be viewed as a Flash movie (.flv). You can find those recordings on the respective MySQL University session pages which are listed on the MySQL University home page.

MySQL University is a free educational online program for engineers/developers. MySQL University sessions are open to anyone, not just Sun employees. Sessions are recorded (slides and audio), so if you can't attend the live session you can look at the recording anytime after the session.

Here's the schedule for the upcoming weeks:

October 1: InnoDB Internals: InnoDB File Formats and Source Code Structure (Calvin Sun)
October 8: Building MySQL Releases on Unix (Jörg Brühe)
October 15: The Spider Storage Engine (Giuseppe Maxia)
November 12: Gearman for MySQL (Giuseppe Maxia)

The schedule is not engraved in stone at this point. Please visit http://forge.mysql.com/wiki/MySQL_University#Upcoming_Sessions for the up-to-date list. On that page, you can also find the starting time for many time zones.

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