stange exception while indexing

[Cam Bazz]

Does anyone have any idea about the error I got while indexing?

Best Regards,
-C.B.

Exception in thread "main" java.io.IOException: background merge hit
exception: _kq:C962870 _kr:C2591 into _ks [optimize]
    at org.apache.lucene.index.IndexWriter.optimize(IndexWriter.java:1749)
    at org.apache.lucene.index.IndexWriter.optimize(IndexWriter.java:1689)
    at org.apache.lucene.index.IndexWriter.optimize(IndexWriter.java:1669)