presto-main/src/main/java/io/prestosql/operator/PagesIndex.java/PagesIndex/createPagesIndexComparator
class PagesIndex:    private PagesIndexOrdering createPagesIndexComparator(List<Integer> sortChannels, List<SortOrder> sortOrders)
    {
        List<Type> sortTypes = sortChannels.stream()
                .map(types::get)
                .collect(toImmutableList());
        return orderingCompiler.compilePagesIndexOrdering(sortTypes, sortChannels, sortOrders);
    }