code: func (q *TagQuery) getInitialByPrefix(expr kv, idCh chan schema.MKey, stopCh chan struct{}) {
  	defer q.wg.Done()
  
  VALUES:
  	for v, ids := range q.index[expr.key] {
  		if !strings.HasPrefix(v, expr.value) {
  			continue
  		}
  
  		for id := range ids {
  			select {
  			case <-stopCh:
  				break VALUES
  			case idCh <- id:
  			}
  		}
  	}
  
  	close(idCh)
  }
docs: // getInitialByPrefix generates the initial resultset by executing the given prefix match expression