Unable to detect changes in contacts android

After scanning through the ContactsContract.Contacts table i get data related to each contact which i then store in the my database with the lookup_key being the primary key.The problem is if the user makes changes to a contact like a name change or phone number change then the lookup key of that contact changes,even though google specifies that a lookup key should be used for identifying a contact.So this way a new contact gets inserted into my database even though the same contact was just edited.