os.clear();
        private void flushWord(short collectionId, String token, ByteArray data) {            //return early            //TODO : is this ever called ? -pb            if (data.size() == 0)                return;            final Lock lock = dbTokens.getLock();            try {                lock.acquire(Lock.WRITE_LOCK);                 WordRef key = new WordRef(collectionId, token);                dbTokens.append(key, data);            } catch (LockException e) {                LOG.warn("Failed to acquire lock for '" + dbTokens.getFile().getName() + "' (inverted index)", e);            } catch (ReadOnlyException e) {                LOG.warn("Read-only error on '" + dbTokens.getFile().getName() + "' (inverted index)", e);            } catch (IOException e) {                LOG.error(e.getMessage() + "' in '" + dbTokens.getFile().getName() + "' (inverted index)", e);               } finally {                lock.release();            }        }        