I am excited to announce the availability of the GA release of our new product Percona XtraDB Cluster.

Percona XtraDB Cluster is a High Availability and Scalability solution for MySQL Users and is based on Percona Server 5.5.20.

With this release we make clustering very easy and affordable for everyone. You can convert your existing MySQL replication setup into a cluster in just a couple minutes.

Tomorrow, 4-April-2012, I will be giving a webinar where I will explain what Percona XtraDB Cluster is and how does it …

On April 2nd 2012 FromDual released the new version v0.9 of its Performance Monitor for MySQL (mpm). The new version can be downloaded from here.

The Performance Monitor for MySQL (mpm) is an agent which is hooked into Zabbix. Zabbix is an integrated Enterprise Monitoring solution which can produce performance graphs and alerting.

The changes in the new release are:

New functionality

• A new server module gathers MySQL database specific server informations. This is especially interesting for the Monitoring as a Service customers.
• You can monitor …

Very interesting blog post by Todd Hoff at highscalability.com presenting “7 Years of YouTube Scalability Lessons in 30 min” based on a presentation from Mike Solomon, one of the original engineers at YouTube:

…. The key takeaway away of the talk for me was doing a lot with really simple tools. While many teams are moving on to more complex ecosystems, YouTube really does keep it simple. They program primarily in Python, use MySQL as their database, they’ve stuck with Apache, and even new features for such a massive site start as a very simple Python program.

That doesn’t mean YouTube doesn’t do cool stuff, they do, but what makes everything work together is more a philosophy or a way of doing things than technological hocus pocus. What made YouTube into one of the …

I’m excited by all of the recent developments surrounding the Percona Live MySQL Conference and Expo! Our own Baron Schwartz will moderate the Diamond Keynote Panel entitled “Future Perfect: The Road Ahead for MySQL” which will feature a panel of MySQL industry leaders, including: Sundar Raghavan, director product management at Amazon; Paul Mikesell, CEO of Clustrix; a representative from HP; and, a representative from McAfee. The Diamond Sponsor Keynote Panel will take place at 9:30 a.m. on Thursday, April 12th and provide insight into the future of MySQL technology, adoption, and the ecosystem landscape. I am also very pleased to introduce two new sponsors including McAfee which recently joined as a Diamond Sponsor and AOL which …

Looks like we’ll be having some more fun at the Percona Live MySQL Conference! In addition to our booth and my colleague Tim’s talk, my lightning talk was accepted. The title is “OLTP and OLAP – Have Your Cake and Eat it Too!” The lightning talks, given in a TBD order, will start Wednesday evening (April 11th) at around 6:30 pm.

Below is the abstract I submitted.

OLTP and OLAP – Have Your Cake and Eat it Too!

…

Swapping occurs when system moves some data between memory and a special area on disk called swap space. The process is called swapping in or swapping out depending on the direction in which it happens. System swaps out when it makes a decision to free up some physical memory (RAM) and pushes data out to disk. It swaps in when an application needs to access data that was swapped out. MySQL is like any other application and any memory it holds can also be sent to disk. It may have severe negative impact on performance.

The foremost step to prevent swapping is ensuring that not database, not any other application can either independently or collectively use up all available memory. The peak usage may not exceed a threshold that still leaves comfortable buffer for any remaining system activity. If this condition is not met, nothing can help and swapping may occur.

Further tuning can be done …

I will be spaking at the conference "Reality Check: Big Data" coming up on April 26 here in Stockholm. This is all about big data in in's different shapes, and the conference is run by Swedish Computer Society and is sponsored by IDG. Read more about it here: http://www.dfkompetens.se/konferenser/kurser/1112022/index.xml

If you are there and want to talk, just catch me there, I'll be there most of the day, and my talk is in the afternoon, at 15:15.

Cheers
/Karlsson

Update: MariaDB 5.1.62 and 5.2.12 have been released. They contain an important security fix.

We are pleased to announce the immediate availability of MariaDB 5.1.61 and MariaDB 5.2.11. Both of these stable (GA) releases incorporate MySQL 5.1.61 and several bug fixes.

Please see the What is MariaDB 5.1 page for an overview of MariaDB 5.1, and the What is MariaDB 5.2 page for an overview of MariaDB 5.2.

Sources, binaries, …

To select the carrier / delivery method in PrestaShop by the postal code of the delivery address, create a file Address.php in /override/classes with this content:

<?php
class Address extends AddressCore
{
    protected static function getPostcodeByAddress($id_address) {
        $row = Db::getInstance()->getRow('
            SELECT `postcode`
            FROM '._DB_PREFIX_.'address a
            WHERE a.`id_address` = '.(int)($id_address));
        return $row['postcode'];
    }

    public static function getZoneById($id_address)
    {
        $postcode = self::getPostcodeByAddress($id_address);
        if (in_array($postcode, Array(1050)))
            return 1;
        elseif (in_array($postcode, Array(2000)))
            return 10;
        return 0;
    }
}

In this example, postal code 1050 is assigned to the carrier with ID 1 and postal code 2000 is assigned to carrier ID 10 (see the carrier list in …

COUNT() function returns a number of rows returned by a query. In a popular opinion COUNT(*) should not be used on InnoDB tables, but this is only half true.

If a query performs filtering on any column, there is no relevant difference in how COUNT(*) will be executed regardless of the storage engine. In any such case MySQL has to look for matching rows and then count them.

In the following queries COUNT(*) can be used without any negative impact on performance:

SELECT COUNT(*) FROM mytable WHERE id = 12345
SELECT COUNT(*) FROM mytable WHERE is_enabled = 1
SELECT COUNT(*) FROM mytable WHERE username LIKE 'a%' AND is_enabled = 1

The real difference is when no filter is specified in WHERE clause, i.e. when query counts all rows in a table. MyISAM maintains cached row count for each table, so it can always return the value …