There is one function we can use to identify row number in oracle analytics cloud application: ROWID()
It can be used inside of workbook, dataset, and dataflow.
Inside of workbook, if you create a calculation with expression rowid(), and then refer this measure in the result set, it will be unique identify each row of returned result
If you want to identify each column in the source dataset, then you need add this column in dataset itself
Beside above, you can also use this function inside dataflow to add unique id for each incoming row, based on it, maybe you can split data or implement some other function based on your requirement.