MySQL 慢查询日志(Slow Query Log)(3)

root@localhost[tempdb]> system tail  /var/lib/mysql/suse11b-slow.log
# User@Host: root[root] @ localhost []
# Query_time: 37.514172  Lock_time: 0.000123 Rows_sent: 0  Rows_examined: 424448
SET timestamp=1412431806;
insert into tb_slow select * from tb_slow;
# Time: 141004 22:10:47
# User@Host: root[root] @ localhost []
# Query_time: 1.573293  Lock_time: 0.000183 Rows_sent: 83  Rows_examined: 424614
SET timestamp=1412431847;
select table_schema,table_name,count(*) from tb_slow  --这条SQL被记录下来了，其查询时间为1.573293s
group by table_schema,table_name order by 3,2;

root@localhost[tempdb]> show variables like '%log_queries_not_using_indexes';
+-------------------------------+-------+
| Variable_name                | Value |
+-------------------------------+-------+
| log_queries_not_using_indexes | OFF  |
+-------------------------------+-------+

root@localhost[tempdb]> set global log_queries_not_using_indexes=1;
Query OK, 0 rows affected (0.00 sec)

--查看表tb_slow索引信息，表tb_slow无任何索引
root@localhost[tempdb]> show index from tb_slow;
Empty set (0.00 sec)

root@localhost[tempdb]> select count(*) from tb_slow;
+----------+
| count(*) |
+----------+
|  424448 |
+----------+
1 row in set (0.20 sec)

root@localhost[tempdb]> system tail -n3 /var/lib/mysql/suse11b-slow.log
# Query_time: 0.199840  Lock_time: 0.000152 Rows_sent: 1  Rows_examined: 424448
SET timestamp=1412432188;
select count(*) from tb_slow;  --此次查询时间为0.199840，被记录的原因是因为没有走索引，因为表本身没有索引

--------------------------------------分割线 --------------------------------------

Ubuntu 14.04下安装MySQL

《MySQL权威指南(原书第2版)》清晰中文扫描版 PDF

Ubuntu 14.04 LTS 安装 LNMP Nginx\PHP5 (PHP-FPM)\MySQL

Ubuntu 14.04下搭建MySQL主从服务器

Ubuntu 12.04 LTS 构建高可用分布式 MySQL 集群

Ubuntu 12.04下源代码安装MySQL5.6以及Python-MySQLdb

MySQL-5.5.38通用二进制安装

--------------------------------------分割线 --------------------------------------