toString

Used for debugging. Format may suddenly change.

Current format looks like _a(3.1):c45/4:[sorter=<long: "timestamp">!], which means the segment's name is _a; it was created with Lucene 3.1 (or '' if it's unknown); it's using compound file format (would be C if not compound); it has 45 documents; it has 4 deletions (this part is left off when there are no deletions); it is sorted by the timestamp field in descending order (this part is omitted for unsorted segments).