Mysql源码学习——打造专属语法(5)

            {

              $2->set_name($1, (uint) ($3 - $1), thd->charset());

            }

          }

        ;

variable:

          '@'

          {

            if (! Lex->parsing_options.allows_variable)

            {

              my_error(ER_VIEW_SELECT_VARIABLE, MYF(0));

              MYSQL_YYABORT;

            }

          }

          variable_aux

          {

            $$= $3;

          }

        ;

variable_aux:

          ident_or_text SET_VAR expr

          {

            Item_func_set_user_var *item;

            $$= item= new (YYTHD->mem_root) Item_func_set_user_var($1, $3);

            if ($$ == NULL)

              MYSQL_YYABORT;

            LEX *lex= Lex;

            lex->uncacheable(UNCACHEABLE_RAND);

            lex->set_var_list.push_back(item);

          }

        | ident_or_text

          {

            $$= new (YYTHD->mem_root) Item_func_get_user_var($1);

            if ($$ == NULL)

              MYSQL_YYABORT;

            LEX *lex= Lex;