@Override
    public void setString(int ordinal, UTF8String value) {
        if (stringValues == null) {
            stringValues = new ArrayList<>();
        }
        int index = stringValues.size();
        stringValues.add(value);
        setLong(ordinal, 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