presto-main/src/main/java/io/prestosql/type/TypeUtils.java/TypeUtils/getHashPosition
class TypeUtils:    public static long getHashPosition(List<? extends Type> hashTypes, Block[] hashBlocks, int position)
    {
        int[] hashChannels = new int[hashBlocks.length];
        for (int i = 0; i < hashBlocks.length; i++) {
            hashChannels[i] = i;
        }
        HashGenerator hashGenerator = new InterpretedHashGenerator(ImmutableList.copyOf(hashTypes), hashChannels);
        Page page = new Page(hashBlocks);
        return hashGenerator.hashPosition(position, page);
    }