I just realized that I haven't blogged for more than a month! Shame on me. But I will blame it on being away on conferences and vacation for quite some time And if you are following me on twitter, you may have noticed what I was going on in my life and that I did't get hit by a bus...

So what was going on since I returned back home from the MySQL Conference? First off, I uploaded und sorted my pictures from the conference and the Drizzle developer day on Flickr. I also uploaded the slides (PDF) from Colin and myself speaking about "MySQL Server Backup, …

I’ve decided to start a series of blog entries on not-so-obvious findings that I’ve found while working on my new project. By archiving the findings, I’m hoping that I can help those that are looking into developing a storage engine for the MySQL family in the future.

Accumulating these mini-knowledge would also be useful for me since I can refer back to it when I forget something. Also, once I write enough entries I’m planning on summarizing them and making it available on the Drizzle Wiki. If MySQL is interested in updating the engine documentation, I would be more than happy to help there too.

So to begin with, I’ll describe something trivial that I stumbled across while trying to catch an error on duplicate primary key insertion to the data table.

Today I attended the Drizzle Developer Day which took place in the auditorium of the Sun Campus in Santa Clara.

Many of the the Drizzle core hackers as well as several other people interested in the development attended this event, hacking away and discussing various issues. Jeremy Zawodny gave a presentation about Craigslist's needs for Drizzle, Jay Pipes gave an overview over Google's protocol buffers library. I took a number of pictures, which you can find in my …

The MySQL Conference & Expo 2009 in Santa Clara is now in full swing and Karen Padir just gave the opening keynote, talking about Sun's continued and improved commitment to Open Source and the upcoming MySQL products like the MySQL 5.4 performance release or MySQL Cluster 7.0. One of the activities that she mentioned in her keynote is our ongoing activity to improve the acceptance and incorporation of patches contributed by the community.

We've scheduled a BoF about this topic …

As I mentioned in my previous entry, InnoDB has it’s own auto increment counter which it uses to generate the next value for the database kernel (as we call it in Drizzle). At Drizzle project, we came across a suspicion that InnoDB doesn’t increment it’s internal counter on row updates. So what can this mean to you as a database admin?

Well, consider this simple table:

CREATE TABLE t1 (
    a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    val INT
) ENGINE=InnoDB;

and the following statements:

drizzle> INSERT INTO t1 (val) VALUES (1);
Query OK, 1 row affected (0.01 sec)
 
drizzle> UPDATE t1 SET a=4 WHERE a=1;
Query OK, 1 row …

Lately I’ve been having lots of fun going through Drizzle and InnoDB‘s sourcecode to get a grasp of how auto increment is processed internally. I think I now have a fairly good grasp of what’s going on so I’m writing this entry as a note for myself. I’m also hoping that this will be helpful to those that are interested in this topic too.

So in MySQL and Drizzle, the storage engine (in this case InnoDB) is responsible for computing the auto increment value. Here’s an abbreviated execution path for a simple INSERT statement to a table with an auto increment column:

mysql_parse() -> mysql_execute_command() -> mysql_insert() ->
write_record() -> handler::ha_write_row() -> ha_innobase::write_row() ->
handler::update_auto_increment() -> ha_innobase::get_auto_increment()

For the last couple of days I’ve been working on removing drizzleadmin (formerly mysqladmin) from Drizzle‘s source tree and I’m happy to announce that the code is now merged to the trunk.

So why did we decide to throw out a program that’s been around for a long time? Well, the tool wasn’t really useful to drizzle since mysqladmin is designed for MySQL and we wanted to factor out these old command line tools in the tree (explained later). With that in mind, I’ve been gradually removing code from drizzleadmin and by the end of it’s lifetime, only two commands remained: “shutdown” and “ping”. These commands are now moved to the drizzle command line tool.

Here’s the new standard way to shutdown drizzled:

$ drizzle --shutdown --verbose
shutting down drizzled... …

Spreading the word about Jay’s awesome findings on the libdrizzle benchmark against the original library inherited from MySQL. For those that aren’t familiar with libdrizzle, it is a fresh new (modern implementation) MySQL compatible client library for Drizzle that leverages asynchronous I/O and smarter memory usage founded by Eric Day.

You can read how this library came to life in this thread:

• https://lists.launchpad.net/drizzle-discuss/msg00472.html

As you can see in Jay’s findings with sysbench, libdrizzle outperforms the original library in all concurrency …

On early Tuesday morning, I made a quick trip to Paris, France, to attend and speak at the Solutions Linux / Open Source 2009 Conference. I've never been to this conference before and was quite surprised about its size - it's actually the largest Open Source event in France and it reminded me a lot of LinuxTag in Germany. Many well-known vendors (e.g. Sun, Novell, Canonical, Bull, etc.) were exhibiting. The also was a large "DotOrg" section for various Open Source projects and I was very happy to see that LeMUG.fr, the official MySQL User Group of France, had a table there, too! A big Thank You goes to Pascal Borghino, who manned that table on his own most of the time and answered questions about MySQL. I …

My travel schedule is getting quite crowded for the next months - I just received confirmation that I will be speaking at the phpDay in Verona, Italy on May 15-16th. I'll be talking about bzr - The Bazaar source revision control system as well as MySQL Backup and Security - Best practices in the developer track of the conference. I've never been to Verona, but it seems like it's a beautiful city. I look forward to being there!