code: func (e *StreamAggExec) Next(ctx context.Context, req *chunk.RecordBatch) error {
  	if span := opentracing.SpanFromContext(ctx); span != nil && span.Tracer() != nil {
  		span1 := span.Tracer().StartSpan("streamAgg.Next", opentracing.ChildOf(span.Context()))
  		defer span1.Finish()
  	}
  	if e.runtimeStats != nil {
  		start := time.Now()
  		defer func() { e.runtimeStats.Record(time.Since(start), req.NumRows()) }()
  	}
  	req.Reset()
  	for !e.executed && !req.IsFull() {
  		err := e.consumeOneGroup(ctx, req.Chunk)
  		if err != nil {
  			e.executed = true
  			return err
  		}
  	}
  	return nil
  }
docs: // Next implements the Executor Next interface.