If is sometimes difficult to keep in mind the range of open source projects that are under Oracle's control these days but MySQL is one of them. The latest version 5.5 has just been made generally available - at least indicating that things are still happening. However the biggest change is that now the MySQL edition with support MySQL Enterprise edition has gone up in price and many suspect that in the future there will be a growing gap between it and the open source Community Edition.
The MySQL 5.5 Community Edition, which is licensed under the GNU General Public License (GPL), is available for free download now includes InnoDB as the default storage engine.
The most important new feature is efficiency and scalability. MySQL Database and InnoDB storage engine have been enhanced to provide optimum performance and scalability when running on the mulit-CPU and multi-core systems. In addition, with release 5.5, InnoDB is now the default storage engine for the MySQL Database, delivering ACID transactions, referential integrity and crash recovery.
New semi-synchronous replication and Replication Heart Beat improve failover speed and reliability.
In recent benchmarks, the new release delivered performance improvements compared to MySQL 5.1. Results included:
On Windows: Up to 1,500 percent performance gains for Read/Write operations and up to 500 percent gain for Read Only.
On Linux: Up to 360 percent performance gain in Read/Write operations and up to 200 percent improvement in Read Only.
These look like speed improvements that make it worth upgrading - especially if you use MySQL under Windows.