docs: public final byte[] getStringAsBytes(int columnIndex) {
          validateColumnType(columnIndex, VoltType.STRING);
          int pos = m_buffer.position();
          m_buffer.position(getOffset(columnIndex));
          int len = m_buffer.getInt();
          if (len == VoltTable.NULL_STRING_INDICATOR) {
              m_wasNull = true;
              m_buffer.position(pos);
              return null;
          }
          m_wasNull = false;
          byte[] data = new byte[len];
          m_buffer.get(data);
          m_buffer.position(pos);
          return data;
      }