I have installed the current version of Confluence and imported the XML backup which was created by the old installation of Confluence. After the import I invoked the feature for rebuilding the index because I was not able to search anymore. Unfortuantely the rebuild did not succeed. Instead the progress of the rebuild slowed down nearly exponentially and did not finish. After downgrading to 2.2.7 the import and index rebuild worked again without any problems.