code: func (p *LogicalSelection) PruneColumns(parentUsedCols []*expression.Column) error {
  	child := p.children[0]
  	parentUsedCols = expression.ExtractColumnsFromExpressions(parentUsedCols, p.Conditions, nil)
  	return child.PruneColumns(parentUsedCols)
  }
docs: // PruneColumns implements LogicalPlan interface.