presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/storage/organization/ShardCompactor.java/SortedRowSource/SortedRowSource
class SortedRowSource:        public SortedRowSource(ConnectorPageSource pageSource, List<Type> columnTypes, List<Integer> sortIndexes, List<SortOrder> sortOrders)
        {
            this.pageSource = requireNonNull(pageSource, "pageSource is null");
            this.columnTypes = ImmutableList.copyOf(requireNonNull(columnTypes, "columnTypes is null"));
            this.sortIndexes = ImmutableList.copyOf(requireNonNull(sortIndexes, "sortIndexes is null"));
            this.sortOrders = ImmutableList.copyOf(requireNonNull(sortOrders, "sortOrders is null"));

            currentPage = pageSource.getNextPage();
            currentPosition = 0;
        }