@Override
 public void discard() throws IOException {
   btree.delete();
 }
 @Override
 protected RecordIterator getRecordsInternal() {
   return btree.iterateAll();
 }
 @Override
 protected void clearInternal() throws IOException {
   btree.clear();
 }
 @Override
 protected void storeRecordInternal(byte[] record) throws IOException {
   btree.insert(record);
 }