Database system concepts by abraham silberschatz #14th chapter

Question

is it allowed in a B+ tree, while deletion to leave behind a key in internal nodes while deleting it from the leaf ?

Answer 1

While deleting a key, we have to take care of the keys present in the internal nodes (i.e. indexes) as well because the values are redundant in a B+ tree.

Comments

Yes, The problem here is gold is not actually one of the leaves. this was a direct screenshot from the book. Even though the tree still works for any valid input at the given state. Nowhere it was mentioned in the book the image here is an intermediate state during deletion of the key element ‘gold’.