Function mysql_sql_parse_order

sqladvisor/main.cc:812–857

同理,同时判断order by 表是否相同,还要判断升降序是否一致

//同理,同时判断order by 表是否相同,还要判断升降序是否一致
TABLE_LIST* mysql_sql_parse_order() {
    TABLE_LIST * table = NULL;
    ORDER::enum_order dire;
    bool is_only_one_table = true;
    SQL_I_List<ORDER> order_list = current_lex->order_list;
    int order_elemnts = order_list.elements;
    int order_elment_i = 0;
    if (order_elemnts > 0) {
        if (options.verbose)
            sql_print_information("第%d步：开始解析order by 条件 \n", STEP_CNT++);
        ORDER *order_field = order_list.first;
        while (order_field != NULL) {
            order_elment_i++;
            if (order_field->item_ptr->type() == Item::FIELD_ITEM) {
                TABLE_LIST * tbname2 = find_table((Item_field *) (order_field->item_ptr));
		if (tbname2 == NULL) {
		    is_only_one_table = false;
		    break;
		}
                if (isPrimary(((Item_field *) (order_field->item_ptr))->field_name,tbname2->table_name)) {
                    if (order_elment_i == order_elemnts) //当order by c1,c2...中包含主键时,只有当主键在最后位置则忽略,否则无法使用order by索引
                        break;
                    else if (options.verbose)
                        sql_print_information("第%d步：字段%s是主键同时不在order by列表末尾,放弃处理order by条件 \n",STEP_CNT++,((Item_field *) (order_field->item_ptr))->field_name);
                    return NULL;
                }
                ORDER::enum_order dire2 = order_field->direction;
                if (table == NULL) {
                    table = tbname2;
                    dire = dire2;
                } else if (table->table_name != tbname2->table_name || dire != dire2) {
                    is_only_one_table = false;
                    break;
                }
	    }
            order_field = order_field->next;
        }

        if (is_only_one_table && table) {
            if (TABLE_ELEMENT == 1 || table->is_table_driverd) {
                return table;
            }
        }
    }
    return NULL;
}

void mysql_sql_parse_group_order_add(TABLE_LIST *table,
        SQL_I_List<ORDER> order_list) {