MariaDB 5.5 has deprecated PBXT
One of the things we (Team MariaDB) talked quite a bit about since we released was PBXT. It was a feature differentiation to MySQL as we shipped another storage engine. It was included in MariaDB 5.1, 5.2, and 5.3; however with our release of MariaDB 5.5, PBXT (docs in the Knowledgebase) has been deprecated and not built by default any longer.
The reason behind it is clear: PBXT is currently not under active development. We still include it in the source releases and if you would like to use it, you just have to build it. If and when development around it comes back to an active state with bugs being fixed and the engine being pushed forward, I’m sure we’ll start building it again. In the meantime, much thanks to Paul McCullagh for developing a great transactional engine.