Why this article?

First of all, because I had fun digging in the code.

Then, I was reading a lot about the improvements we will have in MySQL 5.6 and about some already present in 5.5. Most of them are well covered by people that certainly know more than me, so I read and read, but after a while became curious. I began reading the code and performing tests. I started to compare versions, like 5.1 – 5.5. – 5.6. One of the things I was looking for was how the new Purge thread mechanism works and what were its implications. I have to say that it seems to work better than the previous versions, and the Dimitry blog (see reference) seems to confirm that.

So again, why the article? Because I think there are some traps here and there, and I feel the need to write about them. The worse behavior is with MySQL 5.5. This is because in 5.5 we have an intermediate situation, where the purge is not fully …

I've been dealing with MySQL Cluster in one way or another since around 2005 or so (back in the MySQL 4.1 days) but it is still full of "funny" surprises. This post is a collection of different locking related issue i ran into during the previous weeks that i had not been aware of up to now (or simply may have forgotten over time)

== Unique hash indexes lock exclusively ==

This is the one that regular users are most likely to run into: in general row logs in MySQL Cluster distinguish between reads and writes so that writers can block other writers, but not readers and readers from other transactions always see the last committed row value (Cluster currently only supports the READ COMMITTED isolation level). As soon as you have a secondary unique index in addition to a primary key things are different though. Internally a unique index that is not the primary key is implemented as a unique hash index in Cluster (and optionally also …

Why this article?

First of all because I was having fun in digging in the code.

Then I was reading a lot about the improvements we will have in MySQL 5.6, and of some already present in 5.5.

Most of them are well cover by people for sure more expert then me, so I read and read, but after a while I start to be also curious, and I start to read the code, and do tests.

I start to do comparison between versions, like 5.1 - 5.5. - 5.6

One of the things I was looking to was how the new Purge thread mechanism works and his implications.

I have to say that it seems working better then the previous versions, and the Dimitry blog (see reference) seems confirm that.

So again why the article? Because I think there are some traps here and there and I feel the need to write about them.

The worse behaviour is when using MySQL 5.5, and this is because in 5.5 we have an intermediate …

Tweaking is the motto - what an easy release PECL/mysqlnd_ms 1.4 will be! The first tweak for the next stable version of the mysqlnd replication and load balancing plugin solves pitfalls around charsets. String escaping now works on lazy connection handles (default) prior to establishing a connection to MySQL. A new server_charset setting has been introduced for this. The way it works also prevents you from the risk of using a different charset for escaping than used later on for your connection.

Lazy connections and server_charset

PECL/mysqlnd_ms is a load balancer. A users connection handle can point to different nodes of a replication cluster over time. For example, if using MySQL Replication, the connection handle may point to the master for running writes and, later on, to one of the slaves for reads. At the very moment a user opens a …

This week we listen to MySQL founders David Axmark and Michael "Monty" Widenius talk about all sorts of topics, from the MySQL ecosystem to "Crazy Monty", an open source restaurant. David and Monty don't always agree, so this panel is enlightening and also funny.

News/Events/Feedback
MariaDB 5.5 features - 5.5 is now GA!

IOUG podcast about MySQL Connect and the new Development Milestone Release (DMR) of MySQL 5.6.

read more

If you are using the Disk Data feature of MySQL Cluster you may find this useful. As you may know the default way of storing data in MySQL Cluster is in-memory. However, if you have tables that don't require realtime access and/or are growing larger than your available memory then you can use disk data tables. I have written a bunch of posts about disk data tables before:

• http://johanandersson.blogspot.se/2008/06/disk-data-tables.html
• http://johanandersson.blogspot.se/2008/11/disk-data-extent-deallocation-caveats.html
• …

MySQL uses different type of threads for running specific utilities like mysql_install_db, flushes MyISAM tables, Replication, TCP/IP sockets etc. All threads can run with four different priorities like Interrupt, connect, wait and query priorities. Different types of threads are: The main thread : This one is created by MySQL client normally, this will be one … Continue Reading …

There is no replacement for the documentation of the database products. There is no alternative of forums for these technologies, and also there is no alter ego for the database blogs. They add up yet another avenue to explore when the professionals need help. This Log Buffer Edition helps professional in identifying few blog posts [...]

Percona is glad to announce the release of Percona Server 5.1.62-13.3 on April 25, 2012 (Downloads are available here and from the Percona Software Repositories).

Based on MySQL 5.1.62, including all the bug fixes in it, Percona Server 5.1.62-13.3 is now the current stable release in the 5.1 series. All of Percona‘s software is open-source and free, all the details of the release can be found in the 5.1.62-13.3 milestone at Launchpad.

New …

Percona is glad to announce the release of Percona Server 5.5.22-25.2 on April 25, 2012 (Downloads are available here and from the Percona Software Repositories).

Based on MySQL 5.5.22, including all the bug fixes in it, Percona Server 5.5.22-25.2 is now the current stable release in the 5.5 series. All of Percona‘s software is open-source and free, all the details of the release can be found in the 5.5.22-25.1 milestone at Launchpad.

Bugs Fixed:

• While running the test …