code: final void clear() {
          reset();
          
          _freeQueue.clear();
          _targetQueue.clear();
          _compactedQueue.clear();
          while(!_updateManager.isServiceQueueEmpty()) {
              CompactionUpdateBatch batch = _updateManager.pollBatch();
              _updateManager.recycleBatch(batch);
          }
      }
docs: Note that this method is called only by SimpleDataArray.