how to create a key for write optimzied dso ?

We need the summation of material per plant. But we have a different key in the LQUA table which is WH number and Quant(not the org quantity field, this is a quant of the WH ) Is it mandatory to have the same key as in the table or we can get the summation even with the material & Plant as the semantic key in the write optimized dso ? Please advise how to get the summation from this table using generic datasource through table with the below key.

NOTE :we will have a standard dso on the write optimzied dso and cube /MP as the reporting layer.

Thanks