Insert into DB - dynamically depending on the number of flowfiles

[#1]

I am currently trying to insert a Json file that I transformed in several SQL sequences into my DB.

The DB uses an ID that is not automatically increased but the current highest ID in the DB +1. So if I have 30 insert-statements, I would have to get the maximum ID +1 for the first insert and +2 for the second etc...

Another Problem is, that there could be simultaneous inserts from another instance aswell. Is there a way of creating number of flowfiles (/#sql inserts) dummy files that I can create and update in another processor?

How could I perform this?

[#2]

Is there a way of calling a function that Returns the max(id)+1 with an existing processor? I tried calling my function from nifi, but I could not get it working. I would be glad if there are any Workarounds or tips that you could deliver.

@Matt Burgess