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