presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/RaptorBucketFunction.java/RaptorBucketFunction/varcharHashFunction
class RaptorBucketFunction:    private static HashFunction varcharHashFunction()
    {
        return (block, position) -> XxHash64.hash(block.getSlice(position, 0, block.getSliceLength(position)));
    }