With MySQL it was for a long time the case that a lot of sub queries would actually perform poorly, because of poor execution plans. (This is no longer the case in MariaDB 5.5 or the upcoming MySQL 5.6.) Because of this, any MySQL DBA knows the rule of thumb that sub-queries should basically be avoided and you can usually get the same result by using JOINs instead.

I've now learned why PostgreSQL DBAs like sub queries so much. PostgreSQL - being the most advanced open source database - apparently does the exact opposite optimizations as MySQL: it requires you to rewrite simple queries into complex subqueries to get what you want. (Update: Mark Callaghan points out that MySQL - while it does create indexes automatically for foreign keys - actually has the same problems with the query plan as Postgres has in this post. See comments for details.)

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While I was at Oscon and later at Froscon, one of the most frequent questions I heard was "When will you release MariaDB with Galera?"

Galera is a multi-master cluster solution for MySQL/MariaDB made by Codership.

The reason for the delay has been that we wanted, before the release, to do some QA testing of Galera so that we know how it performs, it's limitations and possible edge cases. Through this we did find some issues that Codership has acted upon.

Now it's finally released.

As this is the first release of MariaDB with Galera, we have labeled the release as 'alpha'. However, don't let the 'alpha' label scare you too much. Galera has been used in production by people I know and they are …

If the basics are right, then the foundation is more likely to be solid, and the growth on that foundation is almost sure to follow the progressive path. Bloggers of Oracle, SQL Server and MySQL are striving hard to set the basics right of the technology in order to help laying a sound foundation for [...]

It has been a long time since I’ve been to Manila, so we’re happy to have a meetup group there with the hopes of turning it regular. If you’re in the Makati area of metro Manila on Tuesday, September 11 2012 at 7pm, feel free to come to the first MariaDB/MySQL Meetup in Manila. RSVP and I hope to see you next Tuesday.

With innodb_file_per_table=1, InnoDB places every table’s data and indexes in a separate .ibd file, but there is still a “global” system tablespace, stored by default in a file named ibdata1. This contains some of each table’s data, such as the undo log and insert buffer. If it is fixed-size, you can fill it up and crash the server, as I’ve mentioned in a few recent blog posts. In older versions of MySQL, the SHOW TABLE STATUS command showed the amount of space free in the tablespace as an entry in the Comment column.

I’ve just released innotop version 1.9.0. This version fixes a lot of bugs, makes the tool work better when monitoring dozens of MySQL servers, and adds two new modes: a Health Dashboard and an InnoDB Blockers/Blocked mode.

CodeConnexx is a 2-day, 1-track conference being held in Indianapolis, Indiana Nov 8-9th. It is only $99 for 2 days; the first day is all tech, and the second day focuses on soft topics like how to manage geeks, working together, mentoring and contributing to open source. The best part about this conference is they truly understand work/life balance and the importance of gender diversity. There is *free* childcare for conference attendees, and 64% of the speakers are female.

I am proud and honored to be doing a tech session on “MySQL Query Optimization with EXPLAIN” and a life skills session on “The Art of Cat Herding: How to Manage Geeks”. And I am also exceedingly proud that …

I previously blogged about work I was doing on automatically finding problems in a MySQL server, with no hardcoded thresholds or predetermined indicators of what is “bad behavior.” I had to pause my studies on that for a while, due to time constraints. I’ve recently been able to resume and I’m happy to report that I’m making good progress.

One of the things I’ve done is a survey of existing literature on this subject. It turns out that the abnormality-detection techniques I’ve developed over the years are well-known in the operations research field. I reinvented some classic techniques used in Statistical Process Control (SPC). These include Shewhart Control Charts, …

Oracle OpenWorld 2012 is just over a month away, and yes, we are organizing the Annual Oracle Bloggers Meetup — one of your top favorite events of OpenWorld.

What: Oracle Bloggers Meetup 2012

When: Wed, 3-Oct-2012, 5:30pm

Where: Main Dining Room, Jillian’s Billiards @ Metreon, 101 Fourth Street, San Francisco, CA 94103 ( …

ConFoo is one of the most important web developer-oriented conferences. ConFoo 2013 will be held on February 25 through March 1 in Montreal, Canada.

We just opened call for papers and we are looking for the best PHP, Java, Ruby, DotNet,HTML5 experts who are willing to share their knowledge with the Canadian community. Candidates can submit proposals until September 23. Consult the call for papers page for details and to start submitting. That page also explains what expenses ConFoo can cover for speakers. You can also get advice on how to write proposals.

The call for papers is public, meaning that all proposals get published on the website for others to vote and comment on. This approach allows the organizers to pick subjects that have …