BOPF Determination based on requested fields

I've a performance intensive calculation implemented in a BOPF Determination. This determination calculates a transient field value.

In my OData DPC_EXT class I'm doing the retrieve_by_association. And passing the $select parameters to the it_requested_attributes. But BOPF is still selecting all fields irrespectively to the requested fields. And especially it's still calculating the transient field even if it's not requested.

I've redefined the /BOBF/IF_FRW_DETERMINATION~check but the requested fields are not available there,

Does anyone have any idea?