It is well known that MySQL can use a lot of temporary files and that, using a ramdisk (tmpfs on Linux) can improve performance drastically as Matt has shown here. The problem with tmpfs is its limited size. You need just one query creating a huge temporary file that happens once per day to screw up the tmpfs scenario. I have done some fuse programming in my previous job and I think it is possible to use fuse to mix a tmpfs filesystem with a regular filesystem, the regular filesystem being used only when the tmpfs is full. Fuse has a lower performance level than a regular filesystem but I think the possibility to use tmpfs the vast majority of the queries needing a temporary file will overcome the performance limitation of fuse.

That is the explanation for the MiniWheatFS name, the frosted side is the tmpfs and the healthy side is the regular filesystem. There are many fuse …

One might have thought Microsoft was back rattling the patented software sabres against Linux and open source this week, reading some of the recent reports regarding Redmond’s patent infringement suit against automotive navigation and GPS player TomTom. However, upon further review, it seems that Microsoft is making a point to say that these suits are not aimed at the Linux OS or open source. In response to my own query, the company offered this:

First, to answer your earlier question on how the suit with TomTom involves the Linux Operating System, three of the infringed patents read on the Linux kernel as implemented by TomTom. However, open source software is not the focal point of this action. …

Shortly after I blogged about my upcoming talks and events, I got informed that one of my session proposals for the next09 conference was accepted. This event will take place in Hamburg, Germany on Tuesday and Wednesday (5th and 6th of May), so at least there isn't much travel involved.

My talk about "Working for a Virtual Company: How we do it at MySQL" has been scheduled for 9:00 am on Wednesday morning, parallel to a keynote by Brian Solis from FutureWorks. I'm not sure how many people will actually show up, but I look forward to giving a talk about a less …

This neat one line command can be of interest when you are rebuilding a MySQL slave and replication is currently catching up.

$ watch --interval=1 --differences 'mysql -uuser -ppassword -e "show slave status\G"'

You will see the standard SHOW SLAVE STATUS output, but the watch command presents an updated view every second, and highlights differences. This can be useful in a background window to keep an eye on those ‘Seconds Behind Master’.

*************************** 1. row ***************************
             Slave_IO_State: Waiting for master to send event
                Master_Host: 10.10.10.10
                Master_User: slave
                Master_Port: 3306
              Connect_Retry: 60
            Master_Log_File: mysql-bin.000626
        Read_Master_Log_Pos: 88159239
             Relay_Log_File: slave-relay.000005
              Relay_Log_Pos: 426677632
      Relay_Master_Log_File: mysql-bin.000621 …

My calendar for the upcoming months is already filling up with conferences, trade fairs and other events at which I'll speak about MySQL. Here's a quick overview:

• This coming Thursday at 15:00 CET, I'll be speaking about "Backing up MySQL using file system snapshots" at the MySQL University. The session will be hosted live using DimDim, which is a great online conferencing and presentation system (Flash required). Attendance is free, so come and join me if you want to learn more about this backup technique!
• On Friday, 6th of March at 15:15 I'll give a presentation about "MySQL Backup and Security" in the …

This Thursday (February 26th, 14:00 UTC), Lenz Grimmer will give a MySQL University session on Backing up MySQL using file system snapshots. Lenz is a member of the MySQL Community team and the maintainer of the mylvmbackup tool. mylvmbackup is a tool for quickly creating backups of a MySQL server's data files. To perform a backup, mylvmbackup obtains a read lock on all tables and flushes all server caches to disk, creates a snapshot of the volume containing the MySQL data directory, and unlocks the tables again. The snapshot process takes only a small amount of time. When it is done, the server can continue normal operations, while the actual file backup proceeds.

For MySQL University sessions, point …

Sorry for the downtime of this site - until around a week ago I hosted my home page on a trusty Genesi Pegasos II system (powered by a PowerPC G4 Processor clocked at 1GHz, using Debian 4.0 PPC with 512 MB of RAM), serving these pages from my home DSL connection. Unfortunately this system provided no means of redundancy - the hard disk drive died.

Luckily I perform frequent backups, so I moved most parts of the site to a shared hosting space now - the picture gallery is unfortunately too big to fit into the space that I have there. I'll try to move the pictures into my Flickr account instead, but this will take some time.

Note that the primary domain name of this site is now lenzg.net - lenzg.org, (the …

Let’s say you need to do a website that must support multiple languages for cultures as diverse as Japan, France, Russia, Saudi Arabia, and Brazil, as well as the US. This can be quite a daunting task, with all kinds of unexpected gotchas.

The ideal character set of choice is, of course, UTF8. Alas, you will note that most of the systems you’ll need to use defaults to LATIN1, including MySQL. If your site is written in PHP, that also by default is set to LATIN1.

I find it quite puzzling that in this day and age of globalization that many of the tools don’t default to UTF8. And there are major issues with this, because everything in the chain of delivery must either be set to UTF8 or can handle UTF8 or you’ll see bizarreness when you attempt to display the characters of some languages. You will probably see a series of question marks (“??? ??? ?????”) instead of the actual words. Sometimes you may see a series of squares. …

If you’re using Fedora 10, and are a KDE desktop user, you’ll notice that your latest KDE 4.2 update, requires having a local MySQL server installed. This is due to Akonadi, part of the KDE PIM packages, that now rely on MySQL as a default server, for storing PIM data. Just a few months ago, I mentioned the news that Amarok 2 will also use MySQL as a default database.

Akonadi uses MySQL mainly as a cache, not as a data store. This is something that Debian users will also see. Eventually, anyone with KDE 4.2 will see the requirement to have a MySQL server installed. If you already have a native installation of MySQL provided for by your distribution (maintained by RPM/DPKG), it …

Today I had to swap 2 columns in one of my MySQL tables. The task, which seems easily accomplishable by a temp variable, proved to be a bit harder to complete. But only just a bit.

Here are my findings:

1. The

   UPDATE swap_test SET x=y, y=x;

   approach doesn't work, as it'll just set both values to y.

   PostgreSQL seems to handle this query differently, as it apparently uses the old values throughout the whole query. [Reference]

2. Here's a method that uses a temporary variable. Thanks to Antony from the comments for the "IS NOT NULL" tweak. Without it, the query works unpredictably. See the table schema at the end of the post. This method doesn't swap the values if one of them is NULL. Use method #3 that doesn't have this limitation. …