At the end of The Force Awakens, it is shown that R2-D2 only has part of the galaxy map to the Jedi temple where Luke is hiding, and there is a very clean section missing as if it has been purposefully removed.
In later interviews, it is clarified that R2-D2 downloaded the map from the Empire when he plugged into the first Death Star.
It is also shown that the First Order is missing the exact same section of the map, hence their hunt for BB-8.
Why are both the First Order and R2-D2 missing this part of the map? Did Luke hack into the Order's mainframe and delete it so he could run and hide? Or was the Empire already missing the data before they became the First Order?
If the Empire just never got around to finishing the map, who did? The two maps fit together perfectly (with a red line and all), so it appears they were once merged.