presto-main/src/main/java/io/prestosql/operator/index/UnloadedIndexKeyRecordSet.java/UnloadedIndexKeyRecordSet/containsNullValue
class UnloadedIndexKeyRecordSet:    private static boolean containsNullValue(int position, Page page)
    {
        for (int channel = 0; channel < page.getChannelCount(); channel++) {
            Block block = page.getBlock(channel);
            if (block.isNull(position)) {
                return true;
            }
        }
        return false;
    }