code: func (q *TagQuery) getInitialByTagPrefix(idCh chan schema.MKey, stopCh chan struct{}) {
  	defer q.wg.Done()
  
  TAGS:
  	for tag, values := range q.index {
  		if !strings.HasPrefix(tag, q.tagPrefix) {
  			continue
  		}
  
  		for _, ids := range values {
  			for id := range ids {
  				select {
  				case <-stopCh:
  					break TAGS
  				case idCh <- id:
  				}
  			}
  		}
  	}
  
  	close(idCh)
  }
docs: // getInitialByTagPrefix generates the initial resultset by creating a list of
  // metric IDs of which at least one tag starts with the defined prefix