@Override
    public RecordPointerAndKeyPrefix newKey() {
        return new RecordPointerAndKeyPrefix();
    }
Supports sorting an array of (record pointer, key prefix) pairs.
Used in {@link UnsafeInMemorySorter}.

Within each long[] buffer, position {@code 2 * i} holds a pointer pointer to the record at
index {@code i}, while position {@code 2 * i + 1} in the array holds an 8-byte key prefix.
indexr-query-opt/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeSortDataFormat.java