As documented in the MySQL Reference Manual:

a UNIQUE index permits multiple NULL values for columns that can contain NULL.

There are many scenarios in which this behavior is desirable. For example imagine you create a user table and require an email address, but you want username to be optional. You make the username column nullable, but you also want to make sure all non-null values in the column are unique, so it makes sense to add a UNIQUE INDEX. If the UNIQUE INDEX didn't allow multiple NULL values then you would need to move the username column to a separate table in order to both maintain uniqueness and allow users without usernames.

But there are also plenty of scenarios where this behavior can cause problems. For example, consider aggregated …

We maintain a lot of servers under Kinja, so we have to use some orchestrator software to perform some tasks on a lot of servers. The Ansbile software is used by us, because it is cool.

We have also a lot of MySQL servers (and counting!) under Kinja, so we have some tasks to perform on them, such as managing replication. Of course there are some ways to do this, for example using multiplexed terminals, or run ansibile shell commands what performs mysql queries (e.g. ansible mysql-master1 -m shell -a “mysql -e “SOME SQL QUERY HERE”) but it is not too comfy, and needs a lot of manual work.

So, there is a way to make it easier for us, and that’s why I made a mysql_replication module for ansible. (And I made a pull request for that on GitHub, so I hope it will be merged soon to ‘official’ branch)

The mysql_replication module helps you to

…

Brandon Johnson at Mozilla has posted a nice tip on how to use MySQL Workbench SSH tunneling with MySQL servers configured to accept only Unix Socket File connections (no TCP/IP). Head over there for more info about how to use the “socat” utility to bridge a SSH tunnel from WB to a socket only MySQL.

A fairy tale

Once upon a time I did an operating system upgrade, a minor one that should do no harm, but just get me up to date by fixing any bugs in the version I had been using. It seemed like a good idea.

All seemed to be fine. I use a package provided by an external vendor and not the one produced by the operating system provider as this vendor provides a newer version of the package and I need that. The vendor has to make his package fit in the os environment his package is built for and normally does a pretty good job.

I use automation to build my systems and when I built a new one some issues appeared. Related to the new version of the OS the provider had enhanced one of his packages and the installation pulled in new dependencies. The install of the external package I use then broke as it conflicted with the new dependency provided by the OS.  While a workaround is possible: uninstall …

Continuent Tungsten Replicator 2.1 is now available for download at www.continuent.com/software and http://code.google.com/p/tungsten-replicator/downloads/list. 

Tungsten Replicator is a high performance, open source, data replication engine for MySQL and Oracle, released under a GPL V2 license. Tungsten Replicator has all the features you expect from enterprise-class data replication products

It has recently been brought to our attention that the MySQL man pages have been relicensed. The change was made rather silently going from MySQL 5.5.30 to MySQL 5.5.31. This affects all pages in the man/ directory of the source code.

You can tell the changes have come during this short timeframe (5.5.30->5.5.31). The old manual pages were released under the following license:

This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License.

The new man pages (following 5.5.31 and greater – still valid for 5.5.32) are released under the following license:

This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license …

This is a follow-up, troubleshooting article that goes hand-in-hand with my “Building MariaDB 5.1 on Windows Revisited” post, and covers some problems and their solutions that one might encounter when attempting to build MariaDB from source code on Microsoft Windows.

The first error I ran into was this, on my main compile step (i.e., the 2nd cmake command):

C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\Microsoft.Cpp
Common.targets(151,5): error MSB6006: "cmd.exe" exited with code 1.
[C:\mysql\mariadb-5.1.67\bld\scripts\GenFixPrivs.vcxproj]

That in itself doesn’t tell us too much. Searching the full compile output, we find:

Generating ../../scripts/mysql_fix_privilege_tables.sql
The system cannot find the file specified.
C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\Microsoft.Cpp
Common.targets(151,5): error MSB6006: "cmd.exe" exited with …

I previously wrote an article on Building MariaDB 5.1 on Windows, but it was about 1.5 years ago (for 5.1.60; this is for 5.1.67), so I wanted to update this a little since I’ve built it entirely from the command-line this time (as well as highlight a couple problems/solutions – which I’ll cover in a subsequent troubleshooting post). This process it quite similar to my steps for building MariaDB 5.5 and MariaDB 10.0, however it’s slightly different since 5.1 requires you run the configure.js script before running cmake. Aside from that though, things are mostly the same.

Here is the full procedure:

Download 5.1.67 MariaDB source and extract to C:\mysql\mariadb-5.1.67
cd C:\mysql\mariadb-5.1.67
win\configure.js
cmake .
cmake …

The MariaDB Foundation Board has now been meeting for a few months and we have been gradually taking steps to establish the Foundation as an independent organisation with member-led governance. The Board has asked me, as CEO, to provide regular updates on our progress here on the MariaDB Blog, so watch for posts in the Foundation category.

I’ve a larger news update in preparation for next week, but first a news item about our relationship with the wider community. Given the threat software patents pose to all free and open source developers, it’s important to use every defence available as well as to unite to frustrate patent aggressors. To that end, the MariaDB Foundation has become a licensee of the Open Invention Network, a …

MySQL Cluster 7.3 has now been declared GA! This means that you can deploy it in your live systems and get support from Oracle.

This post briefly describes the main new features in the release; for a deeper dive, refer to the What’s new in MySQL Cluster 7.3 white paper and the more specialised blog posts that you’ll find links to from this post.

I’ll also be giving more details in the MySQL Cluster 7.3 Webinar which is scheduled for 09:00 Pacific / Noon Eastern / 17:00 UK / 18:00 CET this Thursday (20th June). This is a great opportunity to get your questions answered in real-time by the experts. As …