code: func (p *PhysicalProperty) IsPrefix(prop *PhysicalProperty) bool {
  	if len(p.Items) > len(prop.Items) {
  		return false
  	}
  	for i := range p.Items {
  		if !p.Items[i].Col.Equal(nil, prop.Items[i].Col) || p.Items[i].Desc != prop.Items[i].Desc {
  			return false
  		}
  	}
  	return true
  }
docs: // IsPrefix checks whether the order property is the prefix of another.