code: func (q *TagQuery) getInitialByEqual(expr kv, idCh chan schema.MKey, stopCh chan struct{}) {
  	defer q.wg.Done()
  
  KEYS:
  	for k := range q.index[expr.key][expr.value] {
  		select {
  		case <-stopCh:
  			break KEYS
  		case idCh <- k:
  		}
  	}
  
  	close(idCh)
  }
docs: // getInitialByEqual generates the initial resultset by executing the given equal expression