code: func (e *SelectionExec) Open(ctx context.Context) error {
  	if err := e.baseExecutor.Open(ctx); err != nil {
  		return err
  	}
  	e.childResult = e.children[0].newFirstChunk()
  	e.batched = expression.Vectorizable(e.filters)
  	if e.batched {
  		e.selected = make([]bool, 0, chunk.InitialCapacity)
  	}
  	e.inputIter = chunk.NewIterator4Chunk(e.childResult)
  	e.inputRow = e.inputIter.End()
  	return nil
  }
docs: // Open implements the Executor Open interface.