I recently encountered some strange problems with BeOS: all of a sudden, all of my standard query windows were empty – no new mail, no messages to be answered or to look at any longer. I was frightened.
I made some checks, but the indices seemed to be okay – I tried queries from a Terminal (using the query command), and they worked as expected.
Tracker adds a query for BEOS:TYPE to almost every query, but there is no index for this attribute on a standard system, which is perfectly okay since there are some other (indexed) attributes in the query as well.
Some stupid application I tried recently must have created an index for BEOS:TYPE but of course, no files were listed in there yet, so Tracker could no longer find anything.
Once the problem is revealed, the solution is often very simple:
rmindex BEOS:TYPE
You can use lsindex to get a list of all indices on the current volume – try the -l option to get more information about the indices.