slow query is not to be trusted !

Such like below:
SQL code

# Query_time: 2.495439  Lock_time: 0.000104 Rows_sent: 18  Rows_examined: 18
SET timestamp=1306285687;
SELECT /* SMW::getSemanticData 210.226.94.19 */  p_id, value_string as value  FROM `smw_spec2`  WHERE s_id='7635';

SQL code

335 rows in set (0.00 sec)
 
mysql> explain SELECT /* SMW::getSemanticData 210.226.94.19 */  p_id, value_string as value  FROM `smw_spec2`  WHERE s_id='7635';
+----+-------------+-----------+------+---------------+--------+---------+-------+------+-------+
| id | select_type | table     | type | possible_keys | key    | key_len | ref   | rows | Extra |
+----+-------------+-----------+------+---------------+--------+---------+-------+------+-------+
|  1 | SIMPLE      | smw_spec2 | ref  | s_id,s_id_2   | s_id_2 | 4       | const |  334 |       |
+----+-------------+-----------+------+---------------+--------+---------+-------+------+-------+
1 row in set (0.00 sec)

This query is very faster when system is not busy,but it also contain in the slow_queries file.

当系统繁忙的时候，当然可能会慢


况且你explain的是执行计划 ，并没有显示执行时间

检查你的long_query_time 设置是多少。