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MySQL 日志之--慢查询日志（slow-query-log）

15-12-09 来源：[db:作者]

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慢查询日志：

MySQL慢查询日志记录下所有执行超过long_query_time时间的SQL语句，帮你找到执行慢的SQL，方便我们对这些SQL进行优化。

慢查询日志的配置：

默认情况下，mysql没有启用慢查询日志。

[root@rh64 ~]# mysql -u root -p

Enter password:

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection id is 1

Server version: 5.6.25-73.1 Percona Server (GPL), Release 73.1, Revision 07b797f

Oracle is a registered trademark of Oracle Corporation and/or its

affiliates. Other names may be trademarks of their respective

owners。

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show variables like '%slow%';

+------------------------------------+------------------------------+
| Variable_name                      | Value                        |
+------------------------------------+------------------------------+
| log_slow_admin_statements          | OFF                          |
| log_slow_filter                    |                              |
| log_slow_rate_limit                | 1                            |
| log_slow_rate_type                 | session                      |
| log_slow_slave_statements          | OFF                          |
| log_slow_sp_statements             | ON                           |
| log_slow_verbosity                 |                              |
| max_slowlog_files                  | 0                            |
| max_slowlog_size                   | 0                            |
| slow_launch_time                   | 2                            |
| slow_query_log                     | OFF                          |
| slow_query_log_always_write_time   | 10.000000                    |
| slow_query_log_file                | /var/lib/mysql/rh64-slow.log |
| slow_query_log_timestamp_always    | OFF                          |
| slow_query_log_timestamp_precision | second                       |
| slow_query_log_use_global_control  |                              |
+------------------------------------+------------------------------+
16 rows in set (0.01 sec)

1、可以配置my.cnf文件，服务启动时自动配置

[root@rh64 ~]# cat /etc/my.cnf

[mysqld]

datadir=/var/lib/mysql

socket=/var/lib/mysql/mysql.sock

user=mysql

# Disabling symbolic-links is recommended to prevent assorted security risks

symbolic-links=0

innodb_data_file_path=ibdata1:12M;ibdata2:10M:autoextend

sql_mode=STRICT_TRANS_TABLES ,NO_ENGINE_SUBSTITUTION

slow_query_log=true

slow_query_log_file = "/var/lib/mysql/rh64-slow.log"

long_query_time=1

log-queries-not-using-indexes=true

[mysqld_safe]

log-error=/var/log/mysqld.log

pid-file=/var/run/mysqld/mysqld.pid

explicit_defaults_for_timestamp=true

innodb_buffer_pool_size = 128M

join_buffer_size = 128M

sort_buffer_size = 2M

read_rnd_buffer_size = 2M

重启server后，查看：

mysql> show variables like '%slow%';

+------------------------------------+------------------------------+
| Variable_name                      | Value                        |
+------------------------------------+------------------------------+
| log_slow_admin_statements          | OFF                          |
| log_slow_filter                    |                              |
| log_slow_rate_limit                | 1                            |
| log_slow_rate_type                 | session                      |
| log_slow_slave_statements          | OFF                          |
| log_slow_sp_statements             | ON                           |
| log_slow_verbosity                 |                              |
| max_slowlog_files                  | 0                            |
| max_slowlog_size                   | 0                            |
|
 slow_launch_time                   | 2                            |
| slow_query_log                     | ON                           |
| slow_query_log_always_write_time   | 10.000000                    |
| slow_query_log_file                | /var/lib/mysql/rh64-slow.log |
| slow_query_log_timestamp_always    | OFF                          |
| slow_query_log_timestamp_precision | second                       |
| slow_query_log_use_global_control  |                              |
+------------------------------------+------------------------------+
16 rows in set (0.00 sec)

2、在系统中配置slow-query-log

mysql> set @@global.slow_query_log = on;

mysql> show variables like '%slow%';

+------------------------------------+------------------------------+
| Variable_name                      | Value                        |
+------------------------------------+------------------------------+
| log_slow_admin_statements          | OFF                          |
| log_slow_filter                    |                              |
| log_slow_rate_limit                | 1                            |
| log_slow_rate_type                 | session                      |
| log_slow_slave_statements          | OFF                          |
| log_slow_sp_statements             | ON                           |
| log_slow_verbosity                 |                              |
| max_slowlog_files                  | 0                            |
| max_slowlog_size                   | 0                            |
| slow_launch_time                   | 2                            |
| slow_query_log                     | ON                           |
| slow_query_log_always_write_time   | 10.000000                    |
| slow_query_log_file                | /var/lib/mysql/rh64-slow.log |
| slow_query_log_timestamp_always    | OFF                          |
| slow_query_log_timestamp_precision | second                       |
| slow_query_log_use_global_control  |                              |
+------------------------------------+------------------------------+
16 rows in set (0.00 sec)

3、查看慢查询日志信息

[root@rh64 mysql]# tail rh64-slow.log

use prod;
SET timestamp=1449476453;
insert into emp1 select * from emp1;
# Time: 151207 16:21:11
# User@Host: root[root] @ localhost []  Id:     2
# Schema: prod  Last_errno: 0  Killed: 0
# Query_time: 16.748949  Lock_time: 0.000137  Rows_sent: 0  Rows_examined: 1236992  Rows_affected: 618496
# Bytes_sent: 58
SET timestamp=1449476471;
insert into emp1 select * from emp1;
[root@rh64 mysql]# tail -f rh64-slow.log 
use prod;
SET timestamp=1449476453;
insert into emp1 select * from emp1;
# Time: 151207 16:21:11
# User@Host: root[root] @ localhost []  Id:     2
# Schema: prod  Last_errno: 0  Killed: 0
# Query_time: 16.748949  Lock_time: 0.000137  Rows_sent: 0  Rows_examined: 1236992  Rows_affected: 618496
# Bytes_sent: 58
SET timestamp=1449476471;
insert into emp1 select * from emp1;
# Time: 151207 16:22:54
# User@Host: root[root] @ localhost []  Id:     2
# Schema: prod  Last_errno: 0  Killed: 0
# Query_time: 44.036039  Lock_time: 0.000083  Rows_sent: 0  Rows_examined: 2473984  Rows_affected: 1236992
# Bytes_sent: 59
SET timestamp=1449476574;
insert into emp1 select * from emp1;
# Time: 151207 16:26:46
# User@Host: root[root] @ localhost []  Id:     2
# Schema: prod  Last_errno: 0  Killed: 0
# Query_time: 106.674422  Lock_time: 0.000148  Rows_sent: 0  Rows_examined: 4947968  Rows_affected: 2473984
# Bytes_sent: 59
SET timestamp=1449476806;
insert into emp1 select * from emp1;

记录没有使用索引的语句：

mysql> set @@global.log_queries_not_using_indexes=on;

Query OK, 0 rows affected (0.00 sec)

mysql> show variables like '%index%';
+----------------------------------------+-------+
| Variable_name                          | Value |
+----------------------------------------+-------+
| eq_range_index_dive_limit              | 10    |
| expand_fast_index_creation             | OFF   |
| innodb_adaptive_hash_index             | ON    |
| innodb_adaptive_hash_index_partitions  | 1     |
| innodb_cmp_per_index_enabled           | OFF   |
| log_bin_index                          |       |
| log_queries_not_using_indexes          | ON    |
| log_throttle_queries_not_using_indexes | 0     |
| relay_log_index                        |       |
+----------------------------------------+-------+
9 rows in set (0.00 sec)

测试：

mysql> select count(*) from emp1 where empno=7788;

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

| count(*) |

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

| 688128 |

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

1 row in set (4.03 sec)

[root@rh64 mysql]# tail rh64-slow.log

SET timestamp=1449476453;
insert into emp1 select * from emp1;
# Time: 151207 16:21:11
# User@Host: root[root] @ localhost []  Id:     2
# Schema: prod  Last_errno: 0  Killed: 0
# Query_time: 16.748949  Lock_time: 0.000137  Rows_sent: 0  Rows_examined: 1236992  Rows_affected: 618496
# Bytes_sent: 58

SET timestamp=1449476471;
insert into emp1 select * from emp1;
# Time: 151207 16:22:54
# User@Host: root[root] @ localhost []  Id:     2
# Schema: prod  Last_errno: 0  Killed: 0
# Query_time: 44.036039  Lock_time: 0.000083  Rows_sent: 0  Rows_examined: 2473984  Rows_affected: 1236992
# Bytes_sent: 59

SET timestamp=1449476574;
insert into emp1 select * from emp1;
# Time: 151207 16:26:46
# User@Host: root[root] @ localhost []  Id:     2
# Schema: prod  Last_errno: 0  Killed: 0
# Query_time: 106.674422  Lock_time: 0.000148  Rows_sent: 0  Rows_examined: 4947968  Rows_affected: 2473984
# Bytes_sent: 59

SET timestamp=1449476806;
insert into emp1 select * from emp1;
# Time: 151207 16:30:44
# User@Host: root[root] @ localhost []  Id:     2
# Schema: prod  Last_errno: 0  Killed: 0
# Query_time: 4.025612  Lock_time: 0.000098  Rows_sent: 1  Rows_examined: 4947968  Rows_affected: 0
# Bytes_sent: 68

SET timestamp=1449477044;
select count(*) from emp1 where empno=7788;

4、通过mysqldumpslow工具查看慢查询日志

[root@rh64 mysql]# mysqldumpslow

Can't determine basedir from 'my_print_defaults mysqld' output: --datadir=/var/lib/mysql
--socket=/var/lib/mysql/mysql.sock
--user=mysql
--symbolic-links=0
--innodb_data_file_path=ibdata1:12M;ibdata2:10M:autoextend
--sql_mode=STRICT_TRANS_TABLES ,NO_ENGINE_SUBSTITUTION

[root@rh64 mysql]# mysqldumpslow --help

Usage: mysqldumpslow [ OPTS... ] [ LOGS... ]
Parse and summarize the MySQL slow query log. Options are
  --verbose    verbose
  --debug      debug
  --help       write this text to standard output
  -v           verbose
  -d           debug
  -s ORDER     what to sort by (al, at, ar, c, l, r, t), 'at' is default
                al: average lock time
                ar: average rows sent
                at: average query time
                 c: count
                 l: lock time
                 r: rows sent
                 t: query time  
  -r           reverse the sort order (largest last instead of first)
  -t NUM       just show the top n queries
  -a           don't abstract all numbers to N and strings to 'S'
  -n NUM       abstract numbers with at least n digits within names
  -g PATTERN   grep: only consider stmts that include this string
  -h HOSTNAME  hostname of db server for *-slow.log filename (can be wildcard),
               default is '*', i.e. match all
  -i NAME      name of server instance (if using mysql.server startup script)
  -l           don't subtract lock time from total time

[root@rh64 mysql]# mysqldumpslow rh64-slow.log

Reading mysql slow query log from rh64-slow.log
Count: 3  Time=0.00s (0s)  Lock=0.00s (0s)  Rows=0.0 (0), root[root]@localhost
  # Schema: prod  Last_errno: N  Killed: N
  # Query_time: N.N  Lock_time: N.N  Rows_sent: N  Rows_examined: N  Rows_affected: N
  # Bytes_sent: N
  SET timestamp=N;
  insert into emp1 select * from emp1
Count: 1  Time=0.00s (0s)  Lock=0.00s (0s)  Rows=0.0 (0), root[root]@localhost
  # Schema: prod  Last_errno: N  Killed: N
  # Query_time: N.N  Lock_time: N.N  Rows_sent: N  Rows_examined: N  Rows_affected: N
  # Bytes_sent: N
  use prod;
  SET timestamp=N;
  insert into emp1 select * from emp1
Count: 1  Time=0.00s (0s)  Lock=0.00s (0s)  Rows=0.0 (0), root[root]@localhost
  # Schema: prod  Last_errno: N  Killed: N
  # Query_time: N.N  Lock_time: N.N  Rows_sent: N  Rows_examined: N  Rows_affected: N
  # Bytes_sent: N
  SET timestamp=N;
  select count(*) from emp1 where empno=N

按照平均锁定时间进行排序，查找前10名：

[root@rh64 mysql]# mysqldumpslow -s al -n 10 rh64-slow.log

Reading mysql slow query log from rh64-slow.log

Count: 3 Time=0.00s (0s) Lock=0.00s (0s) Rows=0.0 (0), root[root]@localhost

# Schema: prod Last_errno: N Killed: N

# Query_time: N.N Lock_time: N.N Rows_sent: N Rows_examined: N Rows_affected: N

# Bytes_sent: N

SET timestamp=N;

insert into emp1 select * from emp1

Count: 1 Time=0.00s (0s) Lock=0.00s (0s) Rows=0.0 (0), root[root]@localhost

# Schema: prod Last_errno: N Killed: N

# Query_time: N.N Lock_time: N.N Rows_sent: N Rows_examined: N Rows_affected: N

# Bytes_sent: N

use prod;

SET timestamp=N;

insert into emp1 select * from emp1

Count: 1 Time=0.00s (0s) Lock=0.00s (0s) Rows=0.0 (0), root[root]@localhost

# Schema: prod Last_errno: N Killed: N

# Query_time: N.N Lock_time: N.N Rows_sent: N Rows_examined: N Rows_affected: N

# Bytes_sent: N

SET timestamp=N;

select count(*) from emp1 where empno=N

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