suse查看mysql内存使用情况_MySQL 慢查询日志

最新推荐文章于 2021-04-28 22:24:43 发布

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最新推荐文章于 2021-04-28 22:24:43 发布

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文章标签： suse查看mysql内存使用情况

本文链接：https://blog.youkuaiyun.com/weixin_35775778/article/details/113556300

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long_query_time ：设定慢查询的阀值，超出次设定值的SQL即被记录到慢查询日志，缺省值为10s

slow_query_log ：指定是否开启慢查询日志

log_slow_queries ：指定是否开启慢查询日志(该参数要被slow_query_log取代，做兼容性保留)

slow_query_log_file ：指定慢日志文件存放位置，可以为空，系统会给一个缺省的文件host_name-slow.log

min_examined_row_limit：查询检查返回少于该参数指定行的SQL不被记录到慢查询日志

log_queries_not_using_indexes: 不使用索引的慢查询日志是否记录到索引

--当前版本

root@localhost[(none)]> show variables like 'version';

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

| Variable_name | Value |

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

| version | 5.5.39-log |

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

root@localhost[(none)]> show variables like '%slow%';

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

| Variable_name | Value |

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

| log_slow_queries | OFF |

| slow_launch_time | 2 |

| slow_query_log | OFF |

| slow_query_log_file | /var/lib/mysql/suse11b-slow.log |

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

root@localhost[tempdb]> set global log_slow_queries=1;

Query OK, 0 rows affected, 1 warning (0.00 sec)

root@localhost[(none)]> show warnings;

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

| Level | Code | Message |

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

| Warning | 1287 | '@@log_slow_queries' is deprecated and will be removed in a future release. Please use '@@slow_query_log' instead |

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

--从下面的查询中可知，2个系统变量log_slow_queries，slow_query_log同时被置为on

root@localhost[(none)]> show variables like '%slow%';

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

| Variable_name | Value |

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

| log_slow_queries | ON |

| slow_launch_time | 2 |

| slow_query_log | ON |

| slow_query_log_file | /var/lib/mysql/suse11b-slow.log |

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

root@localhost[tempdb]> show variables like '%long_query_time%';

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

| Variable_name | Value |

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

| long_query_time | 10.000000 |

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

--为便于演示，我们将全局和session级别long_query_time设置为1

root@localhost[tempdb]> set global long_query_time=1;

Query OK, 0 rows affected (0.00 sec)

root@localhost[tempdb]> set session long_query_time=1;

Query OK, 0 rows affected (0.00 sec)

--Author : Leshami

--Blog : http://blog.youkuaiyun.com/leshami

root@localhost[tempdb]> create table tb_slow as select * from information_schema.columns;

Query OK, 829 rows affected (0.10 sec)

Records: 829 Duplicates: 0 Warnings: 0

root@localhost[tempdb]> insert into tb_slow select * from tb_slow;

Query OK, 829 rows affected (0.05 sec)

Records: 829 Duplicates: 0 Warnings: 0

.....为便于演示，我们插入一些数据，中间重复过程省略

root@localhost[tempdb]> insert into tb_slow select * from tb_slow;

Query OK, 26528 rows affected (4.40 sec)

Records: 26528 Duplicates: 0 Warnings: 0

root@localhost[tempdb]> system tail /var/lib/mysql/suse11b-slow.log

/usr/sbin/mysqld, Version: 5.5.39-log (MySQL Community Server (GPL)). started with:

Tcp port: 3306 Unix socket: /var/lib/mysql/mysql.sock

Time Id Command Argument

# Time: 141004 22:05:48

# User@Host: root[root] @ localhost []

# Query_time: 4.396858 Lock_time: 0.000140 Rows_sent: 0 Rows_examined: 53056

use tempdb;

SET timestamp=1412431548;

insert into tb_slow select * from tb_slow;

....再次插入一些记录....

root@localhost[tempdb]> insert into tb_slow select * from tb_slow;

Query OK, 212224 rows affected (37.51 sec)

Records: 212224 Duplicates: 0 Warnings: 0

root@localhost[tempdb]> select table_schema,table_name,count(*) from tb_slow

-> group by table_schema,table_name order by 3,2;

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

| table_schema | table_name | count(*) |

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

| information_schema | COLLATION_CHARACTER_SET_APPLICABILITY | 1024 |

| performance_schema | cond_instances | 1024 |

...........

| mysql | user | 21504 |

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

83 rows in set (1.58 sec)

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