@Override
    public UTF8String getString(int ordinal) {
        int index = (int) getLong(ordinal);
        return stringValues.get(index);
    }
Update this UnsafeRow to point to the underlying byte array.

@param buf         byte array to point to
@param sizeInBytes the number of bytes valid in the byte array
indexr-query-opt/src/main/java/io/indexr/query/row/UnsafeRow.java