private SortedKeyValueIterator<Key,Value> createSystemIter(Range r, List<SortedKeyValueIterator<Key,Value>> readers, HashSet<Column> columns)
throws IOException {
MultiIterator multiIterator = new MultiIterator(readers, false);
DeletingIterator delIter = new DeletingIterator(multiIterator, false);
ColumnFamilySkippingIterator cfsi = new ColumnFamilySkippingIterator(delIter);
ColumnQualifierFilter colFilter = new ColumnQualifierFilter(cfsi, columns);
VisibilityFilter visFilter = new VisibilityFilter(colFilter, Constants.NO_AUTHS, new byte[0]);
visFilter.seek(r, LocalityGroupUtil.EMPTY_CF_SET, false);