code: func DropTxIndex(db database.DB, interrupt <-chan struct{}) error {
  	err := dropIndex(db, addrIndexKey, addrIndexName, interrupt)
  	if err != nil {
  		return err
  	}
  
  	return dropIndex(db, txIndexKey, txIndexName, interrupt)
  }
docs: // DropTxIndex drops the transaction index from the provided database if it
  // exists.  Since the address index relies on it, the address index will also be
  // dropped when it exists.