Sun pushed out a "near final" version of MySQL 5.1 on Tuesday, but is holding back the production release of the open-source database until it irons out some remaining bugs, officials said Tuesday.

Sun wants to avoid issuing another buggy release of the database, which is what happened when MySQL, which Sun acquired in January, released MySQL 5.0 two years ago, said Marten Mickos, the former CEO of MySQL who is now a senior vice president at Sun.

"When we released MySQL 5.0, it didn't really meet our quality standards," he said Tuesday at the start of the MySQL Conference & Expo in Santa Clara, California. "With 5.1 we are being much more conservative, much harder on ourselves."

Sun made a "release candidate" of the software available for download on Tuesday. Mickos said it will release the production version by the end of June, or about three months later than planned.

This marks the first MySQL conference since Sun acquired the company in January. MySQL had been planning an initial public offering before Mickos decided to accept Sun's $1 billion acquisition offer at a dinner with Sun CEO Jonathan Schwartz last November.

Mickos showed a photo on Tuesday of himself and two other MySQL executives, taken on the beach at sunset in Santa Cruz, California, standing around a fire and ceremoniously burning the IPO documents that they never used.

"We took all those bankers' documents and our stock ticker symbol and everything else and we burned it," he said. "It was a sad moment, but also a moment of leaving things behind" and accepting the company's future as part of Sun.

Sun says the deal makes sense because it will be able to bring its vast sales, engineering, and support resources to MySQL. Sun has about 32,000 employees worldwide, and MySQL had only 400. Sun also hopes the deal will open new doors for it to sell its server hardware and other products.

Mickos and Schwartz, who also spoke here, sought to emphasize the synergies between the companies. Schwartz said he has been a champion of open-source software since he took over as CEO two years ago last week.

"The number one thing we are working on with Sun now is performance and scale," Mickos said. "We are known as one of the fastest databases, but all our big customers tell us they want more scale."

MySQL already has some very large customers, including Amazon and Google. But such customers typically modify the open-source software to support their large-scale Web applications.

Sun's goal is to add better scale and performance to the official, supported releases of MySQL and to better support traditional back-end applications where IBM, Oracle, and Microsoft are the dominant vendors.

My SQL 5.1 adds some of those capabilities, including table and index partitioning, which will improve query response times; and row-based replication, for faster and more reliable replication. The update also includes an event scheduler that lets administrators automate common SQL tasks.

The release candidate issued Tuesday is not recommended for production use unless a customer needs the new features right away, Mickos said. He said the delay in the release was not related to Sun's acquisition. The release candidate already has fewer bugs than there were in the production release of MySQL 5.0, he said.