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  • MySQL中查询日志与慢查询日志的基本学习教程(转)

    一、查询日志

      查询日志记录MySQL中所有的query，通过"--log[=file_name]"来打开该功能。由于记录了所有的query，包括所有的select，体积比较大，开启后对性能也有比较大的影响，所以请大家慎用该功能。一般只用于跟踪某些特殊的sql性能问题才会短暂打开该功能。默认的查询日志文件名为：hostname.log.  
    ----默认情况下查看是否启用查询日志：

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    [root@node4 mysql5.5]# service mysql start
     
     
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    Starting MySQL....                     [ OK ]
     
     
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    [root@node4 mysql5.5]# mysql
     
     
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    Welcome to the MySQL monitor. Commands end with ; or g.
    Your MySQL connection id is 1
    Server version: 5.5.22-log Source distribution
     
    Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
     
    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.
     
     
     
     
     
     
     
     
     
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    mysql> show variables like '%log';
     
     
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    +--------------------------------+-------+
    | Variable_name         | Value |
    +--------------------------------+-------+
    | back_log            | 50  |
    | general_log          | OFF  |
    | innodb_locks_unsafe_for_binlog | OFF  |
    | log              | OFF  |
    | relay_log           |    |
    | slow_query_log         | OFF  |
    | sync_binlog          | 0   |
    | sync_relay_log         | 0   |
    +--------------------------------+-------+
    8 rows in set (0.00 sec)
     
     
     
     
     
     
     
     
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    ----备注：log和general_log这两个参数是兼容的。而默认的情况下查询日志是不开启的<br>----使用下面的命令是开启查询日志<br>mysql> set global log=1;
     
     
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    Query OK, 0 rows affected, 1 warning (0.03 sec)
     
     
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    mysql> show variables like '%log';
     
     
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    +--------------------------------+-------+
    | Variable_name         | Value |
    +--------------------------------+-------+
    | back_log            | 50  |
    | general_log          | ON  |
    | innodb_locks_unsafe_for_binlog | OFF  |
    | log              | ON  |
    | relay_log           |    |
    | slow_query_log         | OFF  |
    | sync_binlog          | 0   |
    | sync_relay_log         | 0   |
    +--------------------------------+-------+
    8 rows in set (0.00 sec)
    ----其中log参数是过时的，在启动选项中使用log参数的话，会在err日志中显示出来。
    ----修改my.cnf文件，添加log的参数设置
     
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    [root@node4 mysql5.5]# vi my.cnf
    [root@node4 mysql5.5]# cat ./my.cnf |grep '^log='
    log=/tmp/mysqlgen.log
    ----清空err日志
    [root@node4 mysql5.5]# cat /dev/null > /tmp/mysql3306.err
    [root@node4 mysql5.5]# ll /tmp/mysql3306.err
    -rw-rw---- 1 mysql root 0 Jul 31 07:50 /tmp/mysql3306.err
    [root@node4 mysql5.5]# service mysql start
     
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    Starting MySQL...                     [ OK ]
    ----启动数据库后查看err日志的内容
     
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    [root@node4 mysql5.5]# cat /tmp/mysql3306.err 
     
     
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    130731 07:51:32 mysqld_safe Starting mysqld daemon with databases from /opt/mysql5.5/data
    130731 7:51:32 [Warning] The syntax '--log' is deprecated and will be removed in a future release. Please use '--general-log'/'--general-log-file' instead.
    130731 7:51:33 InnoDB: The InnoDB memory heap is disabled
    130731 7:51:33 InnoDB: Mutexes and rw_locks use InnoDB's own implementation
    130731 7:51:33 InnoDB: Compressed tables use zlib 1.2.3
    130731 7:51:33 InnoDB: Initializing buffer pool, size = 128.0M
    130731 7:51:33 InnoDB: Completed initialization of buffer pool
    130731 7:51:33 InnoDB: highest supported file format is Barracuda.
    130731 7:51:33 InnoDB: Waiting for the background threads to start
    130731 7:51:34 InnoDB: 1.1.8 started; log sequence number 1625855
    130731 7:51:34 [Note] Event Scheduler: Loaded 0 events
    130731 7:51:34 [Note] /opt/mysql5.5/bin/mysqld: ready for connections.
    Version: '5.5.22-log' socket: '/tmp/mysql.sock' port: 3306 Source distribution
    ----使用最新的参数
    ----general_log和general_log_file。
     
     
     
     
     
     
     
     
     
     
     
     
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    [root@node4 mysql5.5]# service mysql stop
     
     
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    Shutting down MySQL.                    [ OK ]
     
     
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    [root@node4 mysql5.5]# vi my.cnf
    [root@node4 mysql5.5]# cat ./my.cnf |grep '^general'
     
     
     
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    general_log = 1
    general_log_file = /tmp/mysqlgen.log
     
     
     
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    [root@node4 mysql5.5]# service mysql start
     
     
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    Starting MySQL...                     [ OK ]
     
     
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    [root@node4 mysql5.5]# mysql
     
     
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    Welcome to the MySQL monitor. Commands end with ; or g.
    Your MySQL connection id is 1
    Server version: 5.5.22-log Source distribution
     
    Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
     
    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.
     
     
     
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    mysql> show variables like '%log';
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    +--------------------------------+-------+
    | Variable_name         | Value |
    +--------------------------------+-------+
    | back_log            | 50  |
    | general_log          | ON  |
    | innodb_locks_unsafe_for_binlog | OFF  |
    | log              | ON  |
    | relay_log           |    |
    | slow_query_log         | OFF  |
    | sync_binlog          | 0   |
    | sync_relay_log         | 0   |
    +--------------------------------+-------+
    8 rows in set (0.04 sec)
     
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    mysql> show variables like '%file';
     
     
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    +---------------------+-----------------------------------+
    | Variable_name    | Value               |
    +---------------------+-----------------------------------+
    | ft_stopword_file  | (built-in)            |
    | general_log_file  | /tmp/mysqlgen.log         |
    | init_file      |                  |
    | local_infile    | ON                |
    | pid_file      | /tmp/mysql3306.pid        |
    | relay_log_info_file | relay-log.info          |
    | slow_query_log_file | /opt/mysql5.5/data/node4-slow.log |
    +---------------------+-----------------------------------+
    7 rows in set (0.00 sec)
    ----在上面的操作中可以看到已经启用查询日志，并且文件目录是/tmp/mysqlgen.log。
    ----查询日志记录了哪些东西？

    进行下面的查询

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    mysql> show databases;
     
     
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    +--------------------+
    | Database      |
    +--------------------+
    | information_schema |
    | mysql       |
    | performance_schema |
    | test        |
    | test2       |
    +--------------------+
    5 rows in set (0.08 sec)
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    mysql> use test;
     
     
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    Database changed
     
     
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    mysql> show tables;
     
     
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    Empty set (0.00 sec)
     
     
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    mysql> use test2;
     
     
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    Database changed
     
     
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    mysql> show tables;
     
     
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    +-----------------+
    | Tables_in_test2 |
    +-----------------+
    | course     |
    | jack      |
    | sc       |
    | student     |
    | t        |
    | teacher     |
    +-----------------+
    6 rows in set (0.07 sec)
     
     
     
     
     
     
     
     
     
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    mysql> drop table t;
     
     
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    Query OK, 0 rows affected (0.13 sec)
     
     
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    mysql> select * from sc;
     
     
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    Empty set (0.04 sec)
     
    ----可以看到上面的操作都记录在了mysqlgen.log里面。
     
     
     
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    [root@node4 ~]# tail -f /tmp/mysqlgen.log
     
     
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    /opt/mysql5.5/bin/mysqld, Version: 5.5.22-log (Source distribution). started with:
    Tcp port: 3306 Unix socket: /tmp/mysql.sock
    Time         Id Command  Argument
    130731 7:55:41    1 Query  show databases
    130731 7:55:56    1 Query  SELECT DATABASE()
          1 Init DB  test
    130731 7:55:59    1 Query  show tables
    130731 7:56:19    1 Query  SELECT DATABASE()
          1 Init DB  test2
    130731 7:56:23    1 Query  show tables
    130731 7:56:27    1 Query  drop table t
    130731 7:56:39    1 Query  select * from sc

    二、慢查询日志
       顾名思义，慢查询日志中记录的是执行时间较长的query，也就是我们常说的slow query，通过设--log-slow-queries[=file_name]来打开该功能并设置记录位置和文件名，默认文件名为hostname-slow.log，默认目录也是数据目录。
        慢查询日志采用的是简单的文本格式，可以通过各种文本编辑器查看其中的内容。其中记录了语句执行的时刻，执行所消耗的时间，执行用户，连接主机等相关信息。MySQL还提供了专门用来分析满查询日志的工具程序mysqlslowdump，用来帮助数据库管理人员解决可能存在的性能问题。

    ----使用log_slow_queries参数打开慢查询，由于该参数已经过时，因此在err日志中将出现提示信息

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    ----修改my.cnf文件，添加log_slow_queries参数
    [root@node4 ~]# vi /opt/mysql5.5/my.cnf
    [root@node4 ~]# cat /opt/mysql5.5/my.cnf |grep '^log_slow'
    log_slow_queries = /tmp/mysqlslow.log
    ----清空err日志内容：
    [root@node4 ~]# cat /dev/null > /tmp/mysql3306.err
    [root@node4 ~]# service mysql start
     
     
     
     
     
     
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    Starting MySQL....                     [ OK ]
     
     
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    ----查看err日志的信息
     
     
    [root@node4 data]# tail -f /tmp/mysql3306.err
     
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    02:26:28 mysqld_safe Starting mysqld daemon with databases from /opt/mysql5.5/data
     2:26:28 [Warning] The syntax '--log-slow-queries' is deprecated and will be removed in a future release. Please use '--slow-query-log'/'--slow-query-log-file' instead.
     2:26:28 [Warning] You need to use --log-bin to make --binlog-format work.
     2:26:28 InnoDB: The InnoDB memory heap is disabled
     2:26:28 InnoDB: Mutexes and rw_locks use InnoDB's own implementation
     2:26:28 InnoDB: Compressed tables use zlib 1.2.3
     2:26:28 InnoDB: Initializing buffer pool, size = 128.0M
     2:26:28 InnoDB: Completed initialization of buffer pool
     2:26:28 InnoDB: highest supported file format is Barracuda.
     2:26:28 InnoDB: Waiting for the background threads to start
     2:26:30 InnoDB: 1.1.8 started; log sequence number 3069452
     2:26:30 [Note] Event Scheduler: Loaded 0 events
     2:26:30 [Note] /opt/mysql5.5/bin/mysqld: ready for connections.
    Version: '5.5.22-log' socket: '/tmp/mysql.sock' port: 3306 Source distribution
     
     
     
     
     
     
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    ----使用slow_query_log和slow_query_log_file
    [root@node4 ~]# vi /opt/mysql5.5/my.cnf
    [root@node4 ~]# cat /opt/mysql5.5/my.cnf |grep '^slow_query'
    ?
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    slow_query_log = 1
    slow_query_log_file = /tmp/mysqlslow.log1
     
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    [root@node4 ~]# service mysql start
     
     
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    Starting MySQL...                     [ OK ]
     
     
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    [root@node4 ~]# mysql
     
     
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    Welcome to the MySQL monitor. Commands end with ; or g.
    Your MySQL connection id is 1
    Server version: 5.5.22-log Source distribution
     
    Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
     
    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.
     
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    mysql> show variables like '%slow%';
     
     
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    +---------------------+---------------------+
    | Variable_name    | Value        |
    +---------------------+---------------------+
    | log_slow_queries  | ON         |
    | slow_launch_time  | 10          |
    | slow_query_log   | ON         |
    | slow_query_log_file | /tmp/mysqlslow.log1 |
    +---------------------+---------------------+
    rows in set (0.00 sec)
     
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    ----关于slow_launch_time参数，首先修改一下参数值
    mysql> set global long_query_time=1;
     
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    Query OK, 0 rows affected (0.00 sec)
     
     
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    mysql> show variables like '%long_query%';
     
     
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    +-----------------+----------+
    | Variable_name  | Value  |
    +-----------------+----------+
    | long_query_time | 1.000000 |
    +-----------------+----------+
    row in set (0.00 sec)

    ----进行一下相关操作，查看/tmp/mysqlslow.log1的内容

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    mysql> select database();
     
     
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    +------------+
    | database() |
    +------------+
    | NULL    |
    +------------+
    row in set (0.00 sec)
     
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    mysql> use test;
     
     
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    Database changed
     
     
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    mysql> show tables;
     
     
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    Empty set (0.00 sec)
     
     
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    mysql> create table t as select * from information_schema.tables;
     
     
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    Query OK, 85 rows affected (0.38 sec)
    Records: 85 Duplicates: 0 Warnings: 0
     
     
     
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    mysql> insert into t select * from t;
     
     
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    Query OK, 85 rows affected (0.05 sec)
    Records: 85 Duplicates: 0 Warnings: 0
     
     
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    mysql> insert into t select * from t;
     
     
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    Query OK, 170 rows affected (0.03 sec)
    Records: 170 Duplicates: 0 Warnings: 0
     
     
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    mysql> insert into t select * from t;
     
     
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    Query OK, 340 rows affected (0.05 sec)
    Records: 340 Duplicates: 0 Warnings: 0
     
     
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    mysql> insert into t select * from t;
     
     
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    Query OK, 680 rows affected (0.08 sec)
    Records: 680 Duplicates: 0 Warnings: 0
     
     
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    mysql> insert into t select * from t;
     
     
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    Query OK, 1360 rows affected (0.29 sec)
    Records: 1360 Duplicates: 0 Warnings: 0
     
     
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    mysql> insert into t select * from t;
     
     
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    Query OK, 2720 rows affected (1.49 sec)
    Records: 2720 Duplicates: 0 Warnings: 0
     
    ----在这里已经超过1s了，查看/tmp/mysqlslow.log1
     
     
     
     
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    [root@node4 data]# tail -f /tmp/mysqlslow.log1
     
     
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    # Time: 130801 2:36:25
    # User@Host: root[root] @ localhost []
    # Query_time: 2.274219 Lock_time: 0.000322 Rows_sent: 0 Rows_examined: 5440
    use test;
    SET timestamp=1375295785;
    insert into t select * from t;
     
    ----log_queries_not_using_indexes参数实验
     
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    mysql> show variables like '%indexes%';
     
     
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    +-------------------------------+-------+
    | Variable_name         | Value |
    +-------------------------------+-------+
    | log_queries_not_using_indexes | OFF  |
    +-------------------------------+-------+
    row in set (0.00 sec)
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    mysql> set log_queries_not_using_indexes = 1;
     
     
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    ERROR 1229 (HY000): Variable 'log_queries_not_using_indexes' is a GLOBAL variable and should be set with SET GLOBAL
     
     
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    mysql> set global log_queries_not_using_indexes = 1;
     
     
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    Query OK, 0 rows affected (0.01 sec)
     
     
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    mysql> show variables like '%indexes%';
     
     
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    +-------------------------------+-------+
    | Variable_name         | Value |
    +-------------------------------+-------+
    | log_queries_not_using_indexes | ON  |
    +-------------------------------+-------+
    row in set (0.00 sec)
     
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    mysql> desc t;
     
     
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    +-----------------+---------------------+------+-----+---------+-------+
    | Field      | Type        | Null | Key | Default | Extra |
    +-----------------+---------------------+------+-----+---------+-------+
    | TABLE_CATALOG  | varchar(512)    | NO  |   |     |    |
    | TABLE_SCHEMA  | varchar(64)     | NO  |   |     |    |
    | TABLE_NAME   | varchar(64)     | NO  |   |     |    |
    | TABLE_TYPE   | varchar(64)     | NO  |   |     |    |
    | ENGINE     | varchar(64)     | YES |   | NULL  |    |
    | VERSION     | bigint(21) unsigned | YES |   | NULL  |    |
    | ROW_FORMAT   | varchar(10)     | YES |   | NULL  |    |
    | TABLE_ROWS   | bigint(21) unsigned | YES |   | NULL  |    |
    | AVG_ROW_LENGTH | bigint(21) unsigned | YES |   | NULL  |    |
    | DATA_LENGTH   | bigint(21) unsigned | YES |   | NULL  |    |
    | MAX_DATA_LENGTH | bigint(21) unsigned | YES |   | NULL  |    |
    | INDEX_LENGTH  | bigint(21) unsigned | YES |   | NULL  |    |
    | DATA_FREE    | bigint(21) unsigned | YES |   | NULL  |    |
    | AUTO_INCREMENT | bigint(21) unsigned | YES |   | NULL  |    |
    | CREATE_TIME   | datetime      | YES |   | NULL  |    |
    | UPDATE_TIME   | datetime      | YES |   | NULL  |    |
    | CHECK_TIME   | datetime      | YES |   | NULL  |    |
    | TABLE_COLLATION | varchar(32)     | YES |   | NULL  |    |
    | CHECKSUM    | bigint(21) unsigned | YES |   | NULL  |    |
    | CREATE_OPTIONS | varchar(255)    | YES |   | NULL  |    |
    | TABLE_COMMENT  | varchar(2048)    | NO  |   |     |    |
    +-----------------+---------------------+------+-----+---------+-------+
    rows in set (0.05 sec)
     
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    ----下面的命令是查看索引的
    mysql> show index from t;
     
     
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    Empty set (0.01 sec)
     
     
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    mysql> select * from t where engine='xxx';
     
     
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    Empty set (0.18 sec)
     
    # Time: 130801 2:43:43
    # User@Host: root[root] @ localhost []
    # Query_time: 0.185773 Lock_time: 0.148868 Rows_sent: 0 Rows_examined: 5440
    SET timestamp=1375296223;
    select * from t where engine='xxx';

    PS：slow query log相关变量

    命令行参数：

        --log-slow-queries

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

    系统变量

        log_slow_queries

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

        slow_query_log

        slow quere log的开关，当值为1的时候说明开启慢查询。

        slow_query_log_file

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

        long_query_time

        记录超过的时间，默认为10s

        log_queries_not_using_indexes

        log下来没有使用索引的query，可以根据情况决定是否开启

    三、Mysqldumpslow

        如果日志内容很多，用眼睛一条一条看会累死，mysql自带了分析的工具，使用方法如下：

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    [root@node4 data]# mysqldumpslow --help
     
     
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    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
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  • 原文地址：https://www.cnblogs.com/wuwuw/p/8855889.html
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