I thought of this, but seems more complicated than what I want:

1. Find the max of imported pk MAX_PK.
2. Change all PKs entries in ReadAt, add MAX_PK to them.
3. Import new data (there is no overlap between the old and new data).
4. Change the PK of ReadAt from old_PK to new_PK.
5. Delete all Person whose PK >= MAX_PK, there are no ForeginKeys to them after the previous step.

I will try implementing it now.