At the first MySQL user conference since it spent a billion dollars acquiring the open source database, Sun said this week that a near-final release candidate of MySQL 5.1 could be downloaded at http://dev.mysql.com/downloads.

It’s supposed to be generally available in June, two months later than anticipated. It’s trying to avoid a bug-ridden premature release like MySQL 5.0.

The new cut is supposed to be 15% faster than previous versions and adds limited table and index partitioning, row-based and hybrid replication, an event scheduler and a new Upgrade Advisor warning enterprise subscribers of bugs.

Thinking of users like Amazon and Google, MySQL is going now for performance and scale, trying perhaps for the performance and scale of Postgres, the other open source database that Sun sells. Under Sun it could take years.

MySQL is also supposed to be developing an SaaS version of itself.

There is also a new visual design tool called MySQL Workbench that integrates data modeling, physical database design, database creation, change management and documentation capabilities into a single seamless environment for MySQL developers and DBAs.

It comes in a free Community Edition or a $99 commercial Standard Edition for Windows now with Linux and Mac to follow.

Meanwhile, Innobase, the MySQL storage engine house that Oracle bought to give MySQL agita, says it’s got a new version of its transactional widgetry, InnoDB Plug-in 1.0 for MySQL 5.1 and ticked off a list of enhancements like fast index creation, data compression, a new row storage format and file format management.

It claims the new Barracuda file format should improve performance, flexibility, reliability and ease of use for InnoDB users.

It also says that MySQL 5.1 users can move to the new plug-in without waiting for the next release of MySQL.

There’s an early adopter release of the GPL-protected code at www.innodb.com/support/downloads/.