code: func (p *LogicalLock) PruneColumns(parentUsedCols []*expression.Column) error {
  	if p.Lock != ast.SelectLockForUpdate {
  		return p.baseLogicalPlan.PruneColumns(parentUsedCols)
  	}
  
  	for _, cols := range p.children[0].Schema().TblID2Handle {
  		parentUsedCols = append(parentUsedCols, cols...)
  	}
  	return p.children[0].PruneColumns(parentUsedCols)
  }
docs: // PruneColumns implements LogicalPlan interface.