With Clearcase, the Lucene index corresponding to the diff text (added and removed lines per changeset and per file) is not populated.

For a given repository myrepo, this index can be found inside the var folder, at /var/cache/myrepo/idx2.

The issue is that, with the new search, the lack of results for the diff texts is very visible, since it is one of the category of results with its own counter. For a ClearCase repository, this counter is always zero and its result page is always empty.