Function mysql_sql_parse_group_order_add

sqladvisor/main.cc:859–925

}

void mysql_sql_parse_group_order_add(TABLE_LIST *table,
        SQL_I_List<ORDER> order_list) {
    INDEX_FIELD * index_head = NULL;
    INDEX_FIELD * index_prev = NULL;
    ORDER * order_field = order_list.first;
    while (order_field != NULL) {
        if (order_field->item_ptr->type() == Item::FIELD_ITEM) {
            if (isPrimary(((Item_field *) (order_field->item_ptr))->field_name,
                    table->table_name)) {
                if (options.verbose)
                    sql_print_information("第%d步：字段%s是主键并且在列表末尾,忽略不添加 \n",
                            STEP_CNT++,
                            ((Item_field *) (order_field->item_ptr))->field_name);
                break; //当字段是主键时,则一定是在order by| group by  列表末尾,直接忽略。
            }
            Field_Description * field_index = new Field_Description(
                    (Item_field *) order_field->item_ptr);
            INDEX_FIELD * index_field = new INDEX_FIELD(field_index);
            if (index_head == NULL) {
                index_head = index_field;
                index_prev = index_head;
            } else {
                index_prev->next_field = index_field;
                index_prev = index_prev->next_field;
            }
        }
        order_field = order_field->next;
    }
    if (index_head != NULL) {
        INDEX_FIELD *index = table->index_field_head;
        if (index == NULL
                || index->index_field->operator_type != Item_func::EQ_FUNC) {
            table->index_field_head = index_head;
        } else {
            INDEX_FIELD *PREV = NULL;
            while (index != NULL) {
                if (strcasecmp(index->index_field->field_name->field_name,
                        index_head->index_field->field_name->field_name) == 0) { //如果存在跟order by条件中相同字段,则直接将order by挂在后面。
                    if (PREV == NULL) {
                        table->index_field_head = index_head;
                    } else {
                        PREV->next_field = index_head;
                    }
                    break;
                }
                if (index->index_field->operator_type == Item_func::EQ_FUNC) {
                    if (index->next_field == NULL) {
                        index->next_field = index_head;
                        break;
                    } else {
                        PREV = index;
                        index = index->next_field;
                    }
                } else {
                    if (PREV == NULL) {
                        table->index_field_head = index_head;
                    } else {
                        PREV->next_field = index_head;