code: func (p *baseLogicalPlan) PruneColumns(parentUsedCols []*expression.Column) {
  	if len(p.children) == 0 {
  		return
  	}
  	child := p.GetChildByIndex(0).(LogicalPlan)
  	child.PruneColumns(parentUsedCols)
  	p.SetSchema(child.GetSchema())
  }
docs: // PruneColumns implements LogicalPlan interface.