Lenz Grimmer's blog

Shortly after I created the initial packages of embedded InnoDB on the OpenSUSE Build Service, Oracle/Innobase released an updated version (1.0.3.5325). In addition to many improvements and bug fixes, they slightly changed the versioning scheme to better indicate what version of the InnodDB plugin their code is based on (see Vasil's posting on the InnoDB Forums for more information).

I've now updated my InnoDB packages on the Build Service to this version as well - please note that the naming scheme of the shared library package has been changed from "embedded_innodb1" to "libinnodb2" — RPM will take care of replacing the old package during update, even though the name has changed.

Oracle/InnoBase announced the availability of the embedded version of InnoDB at this year's MySQL Conference & Expo, but I have not seen a lot of comments or reviews about it so far. Which surprises me, because I think this is a very interesting piece of technology!

In my opinion it might actually hit the sweet spot for application developers seeking an alternative embedded database solution. SQLite is nice and popular, but it seems to have concurrency issues when used in multi-threaded applications. An embedded MySQL server would be an alternative - this is what the Amarok developers decided to go with, for example. But this approach has its issues, too, especially the lack of a shared library version of libmysqld poses some challenges when distributing binaries.

This is where I think the embedded version of InnoDB might have an edge. It's pretty lightweight in comparison to a full-blown MySQL server, provides excellent crash-recovery (which is essential for desktop applications), transactions (useful in environments with high concurrency) and foreign key constraints. I'm not sure how important these are for embedded use cases, it probably depends on the complexity of the data to be stored. On the downside, Embedded InnoDB does not "speak" SQL. In order to store and retrieve values, you need to use the InnoDB API. See the chapter Concepts and Architecture for more details and an overview.

Another possible reason for the low popularity might be that it's currently not part of any Linux distribution (yet) and that Oracle only provides binary tarball packages for Linux and a Windows binary for download from the web site.

Therefore I've now created a spec file to build RPMs of Embedded InnoDB and added it to my repository on the openSUSE Build Service, which now provides Embedded InnoDB packages for a wide range of RPM-based Linux distributions. I hope that the spec file will be included in the next source distribution. I've posted it (and a patch to fix a few problems with the examples) to the newly created InnoDB mailing list, but to be sure I added a note to the Embedded InnoDB Forum as well.

Last week at CeBit I once again had a conversation with an application developer that was not aware that it's possible to embed the MySQL Server inside an application instead of running it as a separate process. I experienced something similar at FOSDEM recently, while talking with the Amarok developers - how come that this feature is so little known? In fact, there are two possibilities for embedding MySQL (and both of them are licensed under the GPL): the first one is using the libmysqld embedded library, which is suitable if you are developing C/C++ applications:

The embedded MySQL server library makes it possible to run a full-featured MySQL server inside a client application. The main benefits are increased speed and more simple management for embedded applications.

The embedded server library is based on the client/server version of MySQL, which is written in C/C++. Consequently, the embedded server also is written in C/C++.

The API is identical for the embedded MySQL version and the client/server version.

Especially consider the last sentence - it's actually fairly easy to create an application that supports connecting to both an embedded or a standalone server instance! Here are some related links to get you going:

• libmysqld, the Embedded MySQL Server Library
• MySQL C API functions
• Embedding the MySQL Server Library in a C Program by Russell Dyer
• Embedded MySQL Discussion Forum

If you're a Java developer, you should consider taking a look at our Connector/MXJ product - this allows you to embed a MySQL server in your Java application:

MySQL Connector/MXJ is a Java Utility package for deploying and managing a MySQL database. Deploying and using MySQL can be as easy as adding an additional parameter to the JDBC connection url, which will result in the database being started when the first connection is made. This makes it easy for Java developers to deploy applications which require a database by reducing installation barriers for their end-users.

MySQL Connector/MXJ makes the MySQL database appear to be a java-based component. It does this by determining what platform the system is running on, selecting the appropriate binary, and launching the executable. It will also optionally deploy an initial database, with any specified parameters.

Included are instructions for use with a JDBC driver and deploying as a JMX MBean to JBoss.

Some related links to further information/help:

• MySQL Connector/MXJ documentation
• MySQL Connector/MXJ Downloads
• JDBC and Java discussion forum
• MySQL and Java Mailing list

Does your application make use of an embedded MySQL Server already? Please let me know! I'd love to learn more about the use cases and experiences you have made.