Codezusammenfassung des langsamen MySQL-Abfragevorgangs

mysql> show variables like "%long%";    
<SPAN style="COLOR: #ff00ff"> //查看一下默认为慢查询的时间10秒 </SPAN> 
+-----------------+-----------+  
| Variable_name  | Value   |  
+-----------------+-----------+  
| long_query_time | 10.000000 |  
+-----------------+-----------+  
1 row in set (0.00 sec)  
  
mysql> set global long_query_time=1;     
<SPAN style="COLOR: #ff00ff">//设置成1秒，加上global,下次进mysql已然生效</SPAN>  
Query OK, 0 rows affected (0.00 sec)  
 
mysql> show variables like "%slow%";     
<SPAN style="COLOR: #ff00ff"> //查看一下慢查询是不是已经开启 </SPAN> 
+---------------------+---------------------------------+  
| Variable_name    | Value              |  
+---------------------+---------------------------------+  
| log_slow_queries  | OFF               |  
| slow_launch_time  | 2                |  
| slow_query_log   | OFF               |  
| slow_query_log_file | /usr/local/mysql/mysql-slow.log |  
+---------------------+---------------------------------+  
4 rows in set (0.00 sec)  
  
mysql> set slow_query_log=&#39;ON&#39;;          
<SPAN style="COLOR: #ff00ff"> //加上global，不然会报错的</SPAN> 
ERROR 1229 (HY000): Variable &#39;slow_query_log&#39; is a GLOBAL variable and should be set with SET GLOBAL 
mysql> set global slow_query_log=&#39;ON&#39;;      
<SPAN style="COLOR: #ff00ff">//这个参数设置为ON，表示启用慢查询，可以捕获执行时间超过一定数值的SQL语句。</SPAN> 
Query OK, 0 rows affected (0.28 sec)  
  
mysql> show variables like "%slow%";       
<SPAN style="COLOR: #ff00ff">//查看是否已经开启 </SPAN> 
+---------------------+---------------------------------+  
| Variable_name    | Value              |  
+---------------------+---------------------------------+  
| log_slow_queries  | ON               |  
| slow_launch_time  | 2                |  
| slow_query_log   | ON               |  
| slow_query_log_file | /usr/local/mysql/mysql-slow.log |  
+---------------------+---------------------------------+  
4 rows in set (0.00 sec)

slow_query_log = 1
      
//开启慢查询日志,将1改为ON也可以
long_query_time = 1
      
//mysql慢查询时间，指定达到多少秒才算慢查询；这里推荐设置超过1秒的执行语句就会被记录到慢查询日志中
slow_query_log_file= /var/lib/mysql/mysql-slow.log
     
//慢查询日志路径。这里slow_query_log_file修改为log-slow-queries 也可以
//主要是上面三行内容，还可以添加下面几行细节性配置
long-queries-not-using-indexes
     
//记录没有使用索引的查询语句
min_examined_row_limit = 1000
    
 //记录查找了多达1000次而引起的慢查询
log-slow-admin-statements
     
  //记录ALTER TABLE等语句引发的慢查询
log-slow-slave-statements       
 //记录从服务器产生的慢查询

/usr/local/mysql/libexec/mysqld, Version: 5.1.26-rc-log (Source distribution). started with:  
Tcp port: 3306 Unix socket: /tmp/mysql.sock  
Time         Id Command  Argument  
# Time: 100814 13:28:30  
# User@Host: root[root] @ localhost []  
# Query_time: 10.096500 Lock_time: 0.045791 Rows_sent: 1 Rows_examined: 2374192  
SET timestamp=1281763710;  
select count(distinct ad_code) as x from ad_visit_history where ad_code in (select ad_code from ad_list where media_id=15);  
# Time: 100814 13:37:02  
# User@Host: root[root] @ localhost []  
# Query_time: 10.394134 Lock_time: 0.000091 Rows_sent: 1 Rows_examined: 2374192  
SET timestamp=1281764222;  
select count(distinct ad_code) as x from ad_visit_history where ad_code in (select ad_code from ad_list where media_id=15);  
# Time: 100814 13:37:16  
# User@Host: root[root] @ localhost []  
# Query_time: 4.608920 Lock_time: 0.000078 Rows_sent: 1 Rows_examined: 1260544  
SET timestamp=1281764236;  
select count(*) as cou from ad_visit_history where ad_code in (select ad_code from ad_list where id=41) order by id desc;