Last night we had a number of keen souls at the Brisbane MySQL User Group. I was very impressed to see the majority of people with laptops at hand.

You can download my slides and code examples at my Articles page.

In our hands on Hackfest tutorial we created the new command SHOW USERGROUPS. Before anybody makes a comment, it was stated in the presentation that this command was made a dummy one, and is a poor candidate for two reasons.

1. The results should be more dynamic, rather then hardcoded into the source tree
2. USERGROUPS is not an ideal name due to comparisions to Users, Groups, Roles etc

Still it was productive, here was the outcome of our work for the evening.

mysql> SHOW USERGROUPS; …

Continuing on from Tutorial 2.

When reviewing the 2.1. C/C++ Coding Guidelines for MySQL, you will see that the MySQL Source uses within the C/C++ code DBUG (Fred Fish’s debug library). This is one of the 3rd party open source products that are documented in the Internals 1.4. The Open-source Directories.

You will also find some usage in the MySQL Manual E.3 The DBUG Package. So enough talk, how do you use this.

DBUG

You get the DBUG output by running a mysqld debug version with the argument –debug. The output …

I got home today and sat down to read my home email list. Nothing new. But on a MySQL mailing list, there was an enquiry why performance was slowing in a given application. I didn’t even have to read the situation, nor the problem, it took less then the 200ms mentioned to identify the problem looking at the supplied schema.

In summary, the first table in the schema had a primary key of VARBINARY(255) and a engine type of Innodb. Hold on, wait, it’s a concatenated key of two VARBINARY(255) columns. And I should mention, that primary key was a foreign key in the next table. If this was a home website app with one user, ok well it’s still bad, but this application was having performance problems with reasonable volumes of transactions, it’s not a beginner application. (A recent reference If you don?t know your data, you don?t know your application). Where do people learn …

“The key, the whole key, and nothing but the key, so help me Codd!”

The database guys should like that one. Can’t remember where I saw it today to acknowledge reference.

Well, it’s Sunday night so I will put this down to being the weekend. The background to being caught out is a request I made to my local Users Group mailing list for some information on people’s environments because I wanted to some empirical data analysis without having any more knowledge of the systems.

In summary (without the surrounding fan-fare, I was seeking):

SELECT VERSION();
SHOW STATUS;
SHOW VARIABLES;  // Optional

I was however perplexed why my first data point analysis (Read/Write ratio) using the Status values Com_insert, Com_update, Com_delete and Com_select was not always giving me expected results. In particular, a number of server results showed 0 for values while I knew the results came from working MySQL environments.

So, sanity check with good friend Morgan and I get the response to answer the dilemma SHOW STATUS defaults to session …

No, it’s not a bedtime story, is a serious system’s design concept and I’m amazing that people don’t know about this.
As I mentioned in If you don?t know your data, you don?t know your application I was doing a Java Code Review, and I found a clear case of a much simplier solution. How simple you ask?

Well, without completing the task 100%, I achieved in less then 1 day (and lets say for the argument 1 more day of work), what is being worked on by somebody else for a week, with an estimate of 2 more weeks to complete. So let’s add 50% to my estimate, that’s a total of 3 days verses 15 days. You do the math. and yes that was last week and that task is still being worked on the same way, even with reference to my working code. Not to mention the code is a similiar magnitude of simplicity, and simplicity means cost savings in support, people so quickly forget …

The art of data modelling is definitely lost on some [most] people, or they never found it, even though they think they did. Over dinner with good friend Morgan last night we were swapping present stories on the topic.

Morgan wrote recently about I want my 4 bytes back damn it., and interesting example storing an ISBN. Further reference can be found at Getting started with MySQL of a more impractical ISBN example.

Disk is cheap now, so the attitude and poor excuse can be, well a few extra bytes doesn’t matter. Well no! If your a social hacker and have a website with a maximium concurrent connections of 2 maybe, but much like some recent Java Code Reviewing I just performed, just because the system isn’t 24×7, …

Just came across a good article by Jay Pipes talking about lazy loading and caching of content. A nice read with some good code examples that I thought I should share with my fellow readers.

Read Jays blog entry

I’ve recently completed a contract and I’ve been in discussions with agents and other employers for further work. Having had one of the worse experiences in my previous work, I’ve been extra careful to ensure what I’m told at the interview/meeting stage is indeed true and accurate (in my last case it was not). I’ve also not made the assumption that an organisation that is dependent on software has placed a certain level of value on what’s in place. (in my last case I did, simply due to the size of the organisation and volume of business).

So, when being asked by people what I’m seeking, outside of the technical skills and compendencies, I’m seeking an organisation that places value on it’s existing software, it’s software quality, it’s software improvement and most importantly it’s software developers. It was unfortunate that for an organisation that lived in software, and would not survive long (especially at …

Today Peter Zaitsev announced launch of new forums related to MySQL Performance questions. He says:

This forum is created as free alternative to MySQL Consulting Services which we provide. If you would like to get some free help to your performance issues please use forums so everyone else could benefit from our replies. You also should get more opinions on your performance problems from other forum members. There were a lot of unrelated performance questions placed as comments and sent by email and we had to find better way to organize it.

I think that it is a great idea to start such forums ontop of great blog site because many people can find it from Google when looking for some performance related questions or discussions. So, I want to say good luck to peter and will try to participate any discussions in these forums.