MariaDB 5.3/5.5 has introduced a new join type “Hash Joins” which is an implementation of a Classic Block-based Hash Join Algorithm. In this post we will see what the Hash Join is, how it works and for what types of queries would it be the right choice. I will show the results of executing benchmarks for different queries and explain the results so that you have a better understanding of when using the Hash Join will be best and when not. Although Hash Joins are available since MariaDB 5.3, but I will be running my benchmarks on the newer MariaDB 5.5.

Overview

Hash Join is a new algorithm introduced in MariaDB 5.3/5.5 that can be used for joining tables that have a equijoin conditions of the form tbl1.col1 = tbl2.col1, etc. As I mentioned above that what is actually implemented is the Classic Hash Join. But its known as Block Nested Loop Hash (BNLH) Join in MariaDB.
The Classic Hash Join Algorithm …

Read the original article at Best of Guide – Highlights of Our Popular Content

We cherry pick the top 5 most popular posts of various topics we’ve covered in recent months.

• 5 Things Toxic to Scalability

We use a broad brush to highlight the biggest no-nos in web application scalability.

We dig into scalability, steering to the richest areas to focus on.

MySQL on Amazon EC2, the what, how …

Today let’s talk about a resource very useful on MySQL, the FullText Index and Search
This resource is very powerful, today on versions 5.5 is just available to MyISAM engine, but, like we can see on MySQL FullText documentation, it will be available also to InnoDB on MySQL 5.6

Usually when we want to search for a word or expression, we use LIKE ‘%word%’, in case we are looking for more than one word we use LIKE ‘%word1%word2%’, what many people don’t know is for this kind of search is expensive and not optimized to our MySQL, in this cases we solve our problems with FullText Index
the syntax is easy, MATHC() … AGAINST (), where MATCH we specified the name(s) of column(s) which we are looking for, yes, we can look for more then one column, we just need all this columns specified on our index …

A special extended edition of Tech Messages for 2011-09-21 through 2012-05-11:

• Understanding Linux CPU Load - when should you be worried?
• Performance Testing - Load Balancer SSL Stress Testing
  This is a great simple test. Thanks, Corey!
• Mosh: the mobile shell
• Twitter open sources its MySQL secret sauce
• Lab Overview
  This guy is serious about his lab!

WordPress on S3: run a beautiful website on Amazon S3 cloud storage

OblakSoft is proud to introduce the 1st ever dynamic WordPress site running on top of Amazon S3: Yapixx.  Now you too can launch your own beautiful website on Amazon S3.

While Yapixx stands for Yet Another Picture Sharing Site, it is actually one of a kind.  Yapixx is WordPress that was moved to run on top of Amazon S3 storage without changing a line of code in the WordPress core engine.

• What is Yapixx?
• …

A short while after I fixed the legacy bug that prevented temporary MyISAM tables from using the dynamic record format, I got an email from Davi Arnaut @ Twitter. It turned out that Twitter needed to fix the very same problem, but for the case when INFORMATION_SCHEMA temporary tables use MyISAM.

In short, INFORMATION_SCHEMA tables provide access to database metadata. Despite their name, they are more like views than tables: when you query them, relevant data is gathered from the dictionary and other server internals, not from tables. The gathered data is stored in a temporary table (memory or MyISAM depending on size) and then returned to the user.

The reason Davi emailed me was to let me know that he had further improved the fix for temporary MyISAM tables to also enable the use of dynamic record format for …

I had to benchmark an EC2 instance to see whether a database could be safely moved to it. It is a good practice, which helps avoiding surprises when an instance or its storage are allocated in a noisy neighborhood, where the neighbors use so much resources that it affects the performance of our MySQL database. It is understandable that one can never get very reliable results on EC2, this is a shared environment after all, and that some fluctuations should be expected, however it is still good to know the numbers. I started my benchmarks and everything seemed fine at first, but then sometimes statistics I was getting started looking quite odd.

I was running the benchmarks on a High-CPU Extra Large Instance and couldn’t see any reliability in the results at all. I mean, in one moment I was getting poor throughput and horrible response times only to see it improve a lot a few minutes later. I ruled out a possibility that it could be …

Security-Enhanced Linux or SELinux is a Linux kernel feature that provides a mechanism for supporting access control security policies. It enables a system administrator to create an extra set of rules that define allowed operations for programs even after the standard controls are checked. In other words, SELinux can help improving system security by restricting access of an application to only a few resources it actually needs, which makes it more difficult for an attacker to gain access to the entire system through exploiting any possible vulnerabilities in the application.

However as rarely anything in life is free, is there any price we have to pay to use SELinux on a MySQL server?

I ran a simple MySQL benchmark first with database working in a system with SELinux enabled (SELINUX=enforcing), and then also with the extra security layer entirely disabled (SELINUX=disabled).

The …

In the latest episode of our “Meet The MySQL Experts” podcast, Mikael Ronstrom, senior MySQL Architect, explains us how the MySQL Thread Pool improves MySQL Scalability.

You can try out the MySQL Thread Pool via our MySQL Enterprise Edition Trial.

And…MySQL being of Nordic origin, Hyvää Vappua/Glada Vappen to all the Finns and Swedes among us!

Enjoy the podcast!

For the week of April 18th, 2012: Oracle Announces It’s First Sponsored MySQL Conference A New Development Milestone Release of MySQL 5.6 is now available IOUG’s Real World Performance Tour Returns to California this Month IOUG’s Plug-In to Vegas! adds … Continue reading →