Looks like a programming question, you can try HashMap and use the domain value as key, then make your comparison and update the count   Here is one example: https://stackoverflow.com/questions/46169229/how-to-count-the-number-of-unique-values-in-hashmap/46169712 ... View more

Hello Dennis,    thank you for the reply. It really helped a lot!   Q1: That worked very well with the updateAttrbute processor.  Q2: This also worked. I had the the settings of the csvWriter service (UpdateRecord) messed up. But it works fine.  Q3: That is a bummer, I hoped it will would be a piece of cake to implement that. But i will look into one of the mentioned tools and figure it out. Q4: True that. The file is going to explode with data.    ... View more