Removing Spotlight index for a no-more-existent Time Machine drive Suppose that an old full Time Machine drive is attached to a new macOS installation, and configured as the main backup storage (but no backup of the new position already begun). Spotlight started indexing the old drive, as usual. 

How would I clear indexing data and related for this disk, if it has been successively erased (ExFAT) with Disk Utility?
Spotlight index for an external drive is stored on that drive, so you wiped it along with the data.