code: func simpleResolveName(node ast.ExprNode, tblInfo *model.TableInfo) (ast.ExprNode, error) {
  	nr := nameResolver{tblInfo, nil}
  	if _, ok := node.Accept(&nr); !ok {
  		return nil, errors.Trace(nr.err)
  	}
  	return node, nil
  }
docs: // SimpleResolveName resolves all column names in the expression node.