MySQL中的profile的意义以及使用场景有哪些？

mysql> show variables like '%profil%';

+------------------------+-------+

| Variable_name          | Value |

+------------------------+-------+

| profiling              | OFF   |         --开启SQL语句剖析功能

| profiling_history_size | 15    |         --设置保留profiling的数目，缺省为15，范围为0至100，为0时将禁用profiling

+------------------------+-------+

SELECT STATE,

       SUM(DURATION) AS TOTAL_R,

       ROUND(100 * SUM(DURATION) /

             (SELECT SUM(DURATION)

                FROM INFORMATION_SCHEMA.PROFILING

               WHERE QUERY_ID = 1),

             2) AS PCT_R,

       COUNT(*) AS CALLS,

       SUM(DURATION) / COUNT(*) AS "R/Call"

  FROM INFORMATION_SCHEMA.PROFILING

 WHERE QUERY_ID = 1

 GROUP BY STATE

 ORDER BY TOTAL_R DESC;