First release candidate of MySQL 5.5 with InnoDB as a default
At its Open World Conference, Oracle has published 5.5.6, the first release candidate of version 5.5 of its free MySQL database. As chief developer Tomas Ulin puts it, the software is fully functional and not a "GA" version (general availability). 5.5 is the first MySQL version that Oracle has released since taking over Sun.
Clearly, the new owner has left its mark in the new default for the database engine. The transaction-capable InnoDB is used, instead of the old MyISAM engine. Oracle says it is much faster than the previous version, thanks partly to multiple roll-back segments and the use of asynchronous I/O under Linux. In particular, MySQL does not come to a standstill as often when there are simultaneous connections on multi-core machines. The developers have changed the threading that the server uses, for example, by using dedicated locks for individual tasks instead of the former global lock.
Another innovation is
SIGNAL/RESIGNAL, which implements a standard method for handling errors that can occur during the execution of stored procedures. A performance schema provides information about MySQL Server's internal performance data. Partitions can be defined based on values for multiple columns. Oracle says that semi-synchronous replication also improves reliability.
The engines are what make MySQL unlike other database systems. They handle actual data management so that, depending on the task, a special engine may be used. While the old default MyISAM does have a reputation of being fast, it does not do transactions or foreign keys. InnoDB has those capabilities but lacks the full-text indexing available in MyISAM. However, Oracle says it will be adding this function.