code: func (view *UtxoViewpoint) fetchUtxos(db database.DB, outpoints map[wire.OutPoint]struct{}) error {
  	// Nothing to do if there are no requested outputs.
  	if len(outpoints) == 0 {
  		return nil
  	}
  
  	// Filter entries that are already in the view.
  	neededSet := make(map[wire.OutPoint]struct{})
  	for outpoint := range outpoints {
  		// Already loaded into the current view.
  		if _, ok := view.entries[outpoint]; ok {
  			continue
  		}
  
  		neededSet[outpoint] = struct{}{}
  	}
  
  	// Request the input utxos from the database.
  	return view.fetchUtxosMain(db, neededSet)
  }
docs: // fetchUtxos loads the unspent transaction outputs for the provided set of
  // outputs into the view from the database as needed unless they already exist
  // in the view in which case they are ignored.