In the first three parts of the series we have seen how a PTF basically works, but we have focused on row-semantic PTF only. In this part we’ll look at the table semantic PTF. As a reminder, the main difference to row-semantic PTF is that it is not enough to look at the currently processed row to produce the result. With table semantic PTF we often also need some summarized state from the previously processed rows. They are useful to implement user defined aggregate or window functions. Let’s first try to implement a very basic example of table semantic PTF and learn more theory as we go. Weiterlesen →