查看Query Performance
SET PROFILING=1;
SHOW PROFILES;
SHOW PROFILE CPU FOR QUERY 2;
觀看即時process
SHOW FULL PROCESSLIST;
Buffer Size
如果MySQL使用的CPU過高，加大buffer可能有幫助，以下是innodb引擎的調教方式
查看當前buffer size
SHOW VARIABLES LIKE 'innodb_buffer_pool_size';
查看建議buffer size，參考神回答
SELECT CEILING(Total_InnoDB_Bytes*1.6/POWER(1024,3)) RIBPS FROM
(SELECT SUM(data_length+index_length) Total_InnoDB_Bytes
FROM information_schema.tables WHERE engine='InnoDB') A;
如果出現數字1，表示建議buffer size 1GB，可在/etc/mysql/conf.d/my.cnf設定
[mysqld]
innodb_buffer_pool_size = 1G
[mysql]跟[mysqld]的差別：前者是mysql command line client套用的設定，後者是mysql server。詳情見此。
重啟mysql server後，再次查看buffer size確認無誤。
Query Cache
另外可以再加兩項，query_cache_size是所有query的cache大小，query_cache_limit是單個query所佔的極限。
query_cache_size=518M
query_cache_limit=10M
Example
select SQL_NO_CACHE P.* from product P left join
(
select distinct product_id, sort from product_type_relation where type_id in (16)
) AS A
ON P.id=A.product_id
ORDER BY A.sort, P.id desc
LIMIT 0,28;
=> 耗時0.1
SELECT SQL_NO_CACHE distinct P.id, P.*
FROM product_type_relation A
LEFT JOIN product P ON A.product_id=P.id
WHERE A.type_id in (16)
ORDER BY A.sort asc, P.id desc
LIMIT 0, 28;
=> 耗時0.04
SELECT SQL_NO_CACHE P.*
FROM product P
LEFT JOIN product_type_relation A ON A.product_id=P.id
WHERE P.id in
(
select distinct product_id from product_type_relation where type_id in (16)
)
ORDER BY A.sort
LIMIT 0,28;
=> 耗時0.022
