Thank you very much for your input!
The stored procedure is also what I got in my trace, and I recon that the more logic SAP pushes down from the BW OLAP into the Analytical Engine of HANA, the more complex statements you will get.
My aim is here is to make sure that the calculation view performs good, that it handles the pruning correctly (I use the constant values in Unions) and not the least, to make sure that we transfer as few records as possible between the views/engines.
All my source tables have between 500 million and 5 billion records hence the reason why it is important to validate and document how the data is processed internally before sending it to BW/frontend.
Is there any way to run something similar to PlanViz with a Bex Query as input? The RSRT does not really give me the required HANA information.