Michael J. Ross writes "If you were to ask some database developers to cite their favorite strategies for expanding the functionality of the relational database management systems with which they work, you would probably hear a variety of answers. One individual might recommend the use of an alternate database engine optimized for the given application. Another might explain the many advantages of using stored procedures to replace SQL queries embedded in the source code of any programs that connect to databases. But one answer you likely would not receive involves changing the internals of the database engine itself. With the latest major release of MySQL, developers using that particular RDBMS are now able to extend the capabilities of the built-in database engines, by creating plug-ins. This is the topic of a book by Sergei Golubchik and Andrew Hutchings: MySQL 5.1 Plugin Development." Read on for the rest of Michael's review.