code: func NewValuesFunc(ctx sessionctx.Context, offset int, retTp *types.FieldType) *ScalarFunction {
  	fc := &valuesFunctionClass{baseFunctionClass{ast.Values, 0, 0}, offset, retTp}
  	bt, err := fc.getFunction(ctx, nil)
  	terror.Log(err)
  	return &ScalarFunction{
  		FuncName: model.NewCIStr(ast.Values),
  		RetType:  retTp,
  		Function: bt,
  	}
  }
docs: // NewValuesFunc creates a new values function.