code: func (p *Projection) matchProperty(_ *requiredProperty, childPlanInfo ...*physicalPlanInfo) *physicalPlanInfo {
  	np := *p
  	np.SetChildren(childPlanInfo[0].p)
  	return &physicalPlanInfo{p: &np, cost: childPlanInfo[0].cost}
  }
docs: // matchProperty implements PhysicalPlan matchProperty interface.