By Giuseppe Maxia

The Data Charmer, a.k.a. The Wizard, is a free lance database consultant, with a long career in several IT fields. He is well known for his Perl and SQL expertise,although he is proficient in several other languages, such as C++, shell scripts, and Italian.

He has a split personality, one of which lives in virtual space and time, floating around UTC+1. The other (or the others, as there is a dispute about how many they are) is less documented and some people believe it to be fictional. He teaches Creative Biography at the University of Euphoria, CA (also known as Euphoric State).

G.M. Hello, D.C. Thanks for agreeing to be interviewed. I'll start with a question that most people ask. Who are you?

D.C. This is not really a question I'm willing to answer. Besides, the answer would be misleading. In the Internet age, I can be several people at …

I spent the last month taking a break from Open Source, partly due to FreeBSD 7.1 failing to hit the FTP servers as scheduled (any excuse), but mostly due to Santa’s early delivery of Ableton Live. Not really Open Source I may add but extremely cool nonetheless and a much needed break from coding!.

I find that staring too much at code can hamper the creative process (hehe), and as you know Creativity and Innovation go hand in hand with Open Source Software!.

Speaking of which, while I have been busy playing with waveforms and elastic audio, the Open Source world has been all guns blazing with cool releases like MySQL 5.1 GA, …

How would one concatenate strings from a column (multiple rows) into a single row using MySQL? I see its possible with MS SQL Server 2005 and above. Any incite into how to achieve this in MySQL would be much appreciated.

MS SQL Server 2005 - Example

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SELECT Web_Account_ID,
GroupNameConcat = REPLACE(
        (
        SELECT
                Web_Account_Group_Name_ID AS [DATA()]
        FROM
                tblWebAccountGroup WAG
        WHERE
                WAG.Web_Account_ID = WA.Web_Account_ID
        ORDER BY
                Web_Account_Group_Name_ID
            FOR XML PATH ('')
        ), ' ', ',')
FROM tblWebAccounts WA
ORDER BY Web_Account_ID

Query Results Example

Source: …

Arjen & gang are looking for skilled and enthusiastic colleagues!
Essentials

• guru level practical skills in MySQL schema/query design, server administration and tuning;
  
• expertise with common dev and deployment infrastructure (mainly Linux but also other *nix and Windows);
  
• freedom to travel without restriction;
  
• self-motivated, ability to work independently (from anywhere - good Internet access required);
  
• excellent written/verbal English, comfortable public speaker.

Being a small, company, the range of possible work tasks can be quite diverse, although you are not required to be able to do everything. That said, your application will be more highly regarded if you exhibit a broad range of skills and interests, both directly technical and otherwise.
Desirable abilities

• shell and Perl scripting;
  
…

Few months ago I’ve switched one of our internal projects from doing synchronous database saves of analytics data to an asynchronous processing using starling + a pool of workers. This was the day when I really understood the power of specialized queue servers. I was using database (mostly, MySQL) for this kind of tasks for years and sometimes (especially under a highly concurrent load) it worked not so fast… Few times I worked with some queue servers, but those were either some small tasks or I didn’t have a time to really get the idea, that specialized queue servers were created just to do these tasks quickly and efficiently.

All this time (few months now) I was using starling noticed really bad thing in how it works: if workers die (really die, or lock on something for a long time, or just start lagging) …

Since the day one when I joined Scribd, I was thinking about the fact that 90+% of our traffic is going to the document view pages, which is a single action in our documents controller. I was wondering how could we improve this action responsiveness and make our users happier.

Few times I was creating a git branches and hacking this action trying to implement some sort of page-level caching to make things faster. But all the time results weren’t as good as I’d like them to be. So, branches were sitting there and waiting for a better idea.

Few months ago my good friend has joined Scribd and we’ve started thinking on this problem together. As the result of our brainstorming we’ve managed to figure out what were the problems preventing us from doing efficient caching: …

Background Knowledge

For some reason or another the priority menu in the edit task panel is not wide enough and therefore it cuts off the priority names. This can be easily fixed by modifying some inline CSS. Yes I agree this should be done within the skin’s CSS file, however there is nothing present in the CSS file to alter that I could find.

Solution

Edit /taskfreak/include/html/xajax_panel_edit.php at line #18 by changing the width value of “40px” to “125px” or to what you desired width.

Code Before

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<td>< ?php
$objTemp = new ItemPriority();
$objTemp->qSelect('priority',($objTask->priority)?$objTask->priority:3,'','','style="width:40px"');
?></td>

Code After

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<td>< …

Background Knowledge

TaskFreak! presently does not have a means via the web interface to present a complete list of tasks for which the current user is the project leader. I will show you how to add “My Projects” list based on bpiper’s solution with a slight difference. My solution is almost identical to bpiper’s but with a different approach to continue support of the supported interface languages. To do this each supported language file will require to be edited.

Thanks to bpiper for posting your solution.

Solution

1. Edit /taskfreak/include/language/en/freak.php starting at line #15. Add in a new array key/value at any point you desire like so “‘my_projects’ => ‘My Projects’,” (without double quotes), see below for example.

   Note: Each interface language file will be …

On a large data migration project that I am currently spearheading, we have a large installed userbase of over 2 million users running on a social networking engine. The schema has been redesigned from scratch, and code is being written to match the new schema, using the all-powerful MySQL database as the system to manage all that data.

Since this social network is global, we need good and reliable location information. The current location model is flawed and full of holes, so we have chosen AssemblySys‘ data to replace it.

We are not using AssemblySys’ schema, as we’ve rolled our own. I’ve designed our new schema to be hierarchial in nature, treating all locations on the planet as ‘nodes’ with a tree relationship, with “Earth” being the parent of all nodes. This model allows us to account for all countries and their idiosyncratic …

In many programing languages it is possible to shorten if statements using what’s called the ternary operator. It is sometimes referred as the “one line if statement” or the “short if statement”. This can help at times to produce cleaner code, however use this operator wisely as it is not always best to be used for more complicated statements.

PHP Example of an if statement

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if($nFoo > 0)
{
   echo "I'm at the work.";
}
else
{
   echo "I'm at home.";
}

PHP Example using the ternary operator

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      echo $nFoo > 0 ? "I'm at the work." : "I'm at home.";

The expression (expr1) ? (expr2) : (expr3) evaluates to expr2 if expr1 evaluates to …