One technique that I use to understand MySQL Internals (and ZFS internals in the past) is to look at bug reports. They have lots of useful information in them.

One example is Bug#32149 Long semaphore wait for adaptive hash latch. The bug synopsis could very well have been Why are global locks in a storage engine such a BAD idea. There is lots of useful information about this and the workaround MySQL server uses to work with storage engines that do.. Interesting!

Do you know of any other interesting bugs that document MySQL internals?

One technique that I use to understand MySQL Internals (and ZFS internals in the past) is to look at bug reports. They have lots of useful information in them.

One example is Bug#32149 Long semaphore wait for adaptive hash latch. The bug synopsis could very well have been Why are global locks in a storage engine such a BAD idea. There is lots of useful information about this and the workaround MySQL server uses to work with storage engines that do.. Interesting!

Do you know of any other interesting bugs that document MySQL internals?

as celia wrote earlier, we are in riga, latvia for a meeting of the mysql developers. she is holed up in the hotel room working on a screenplay (or maybe in the atrium where the wifi is better), and i am in a presentation about blogging.

celia already posted pictures from our excursion day on sunday (the day we didn’t sit around in the meeting rooms at the hotel). i took some video which i will figure out how to deal with once we are back home.

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Recently we were migrating an InnoDB/MyISAM schema to NDB. I was too lazy to calculate all the needed MySQL Cluster parameters (for example with ndb_size.pl) and just took my default config.ini template.
Because I am really lazy I have a little script doing this for me (alter_engine.sh).

But suddenly my euphoria was stopped abruptly by the following error:

 MySQL error code 136: No more room in index file

The usual command that helps me in such a situation is a follows:

 # perror 136

MySQL error code 136: No more room in index file

But in this case it is not really helpful. Also …

This is a picture with a lot of impact. This was from Seedcamp. The question asked was “What tools will you use?”.

Mårten pointed this out to us at the opening speeches at the Sun Database Group Developer’s Meeting. Its interesting to see what technologies are used. MySQL is by far, the most popular database server that all startups seem to use (though to be fair, I see CouchDB and PostgreSQL there too). PHP is about the most popular language (followed closely by Java, then Ruby). Its amazing to see what kind of technologies people are using to build the companies of tomorrow.

Find out more about it, at the Zeitgeist redux on the seedcamp blog.

I had first seen the interesting Rails logo in a talk by Terry Chay, while I was at OSCON, a few months ago.

Now, my esteemed colleague Jay Pipes has it on his laptop. It seems they’re making stickers, even.

Otherwise, my next task is to revamp our Ruby content. Currently, it looks a little sad. It has to at least be as good as Using MySQL With Ruby, no?

Recently we were migrating an InnoDB/MyISAM schema to NDB. I was too lazy to calculate all the needed MySQL Cluster parameters (for example with ndb_size.pl) and just took my default config.ini template.
Because I am really lazy I have a little script doing this for me (alter_engine.sh).

But suddenly my euphoria was stopped abruptly by the following error:

MySQL error code 136: No more room in index file

The usual command that helps me in such a situation is a follows:

# perror 136
MySQL error code 136: No more room in index file

But in this case …

Recently, I had to futz with an Ubuntu server that was to run mail, web, and database services.

You slowly learn that Ubuntu as a desktop is easy to use, but as a server, its “different”, if you come from a Red Hat based background (especially if you’ve been using Red Hat-based distributions for the last thirteen years or so).

From example, while service httpd start works (well, the equivalent is service apache start), enabling things on boot using chkconfig (I wrote about it a while back) is replaced with update-rc.d.

In fact, if you’re an rpm aficionado, dpkg is a little different. I applaud the Ubuntu folk for creating an article such as …

A customer has recently experienced a possible memory leak in its NDB-API application. What he did was something like:

# ps aux | grep <pid>

over time and then he saw the RSS increasing. When he would have had a look a little longer he would have seen that the RSS consumption would increase up to a certain level and then becomes stable. Which is the expected behavior.

But how to explain to the customer that his application, which was in fact not doing anything, consumes more RSS?
With a diff over time on /proc/<pid>/smaps we found that this area was the reason:

b67b7000-b6fca000 rw-p b67b7000 00:00 0 (8 Mbyte)
Size:               8268 kB
Rss:                 148 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:       148 kB
Referenced:          148 kB

But what is this meaning? To find the answer we did a strace on the program and got the …