一、information_schema简介
在MySQL中，把 information_schema 看作是一个数据库，确切说是信息数据库。其中保存着关于MySQL服务器所维护的所有其他数据库的信息。如数据库名，数据库的表，表栏的数据类型与访问权 限等。在INFORMATION_SCHEMA中，有数个只读表。它们实际上是视图，而不是基本表，因此，你将无法看到与之相关的任何文件。
information_schema数据库表说明:
1 1、SCHEMATA表：提供了当前mysql实例中所有数据库的信息。是show databases的结果取之此表。
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3 2、TABLES表：提供了关于数据库中的表的信息（包括视图）。详细表述了某个表属于哪个schema，表类型，表引擎，创建时间等信息。是show tables from schemaname的结果取之此表。
4
5 3、COLUMNS表：提供了表中的列信息。详细表述了某张表的所有列以及每个列的信息。是show columns from schemaname.tablename的结果取之此表。
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7 4、STATISTICS表：提供了关于表索引的信息。是show index from schemaname.tablename的结果取之此表。
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9 5、USER_PRIVILEGES（用户权限）表：给出了关于全程权限的信息。该信息源自mysql.user授权表。是非标准表。
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11 6、SCHEMA_PRIVILEGES（方案权限）表：给出了关于方案（数据库）权限的信息。该信息来自mysql.db授权表。是非标准表。
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13 7、TABLE_PRIVILEGES（表权限）表：给出了关于表权限的信息。该信息源自mysql.tables_priv授权表。是非标准表。
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15 8、COLUMN_PRIVILEGES（列权限）表：给出了关于列权限的信息。该信息源自mysql.columns_priv授权表。是非标准表。
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17 9、CHARACTER_SETS（字符集）表：提供了mysql实例可用字符集的信息。是SHOW CHARACTER SET结果集取之此表。
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19 10、COLLATIONS表：提供了关于各字符集的对照信息。
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21 11、COLLATION_CHARACTER_SET_APPLICABILITY表：指明了可用于校对的字符集。这些列等效于SHOW COLLATION的前两个显示字段。
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23 12、TABLE_CONSTRAINTS表：描述了存在约束的表。以及表的约束类型。
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25 13、KEY_COLUMN_USAGE表：描述了具有约束的键列。
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27 14、ROUTINES表：提供了关于存储子程序（存储程序和函数）的信息。此时，ROUTINES表不包含自定义函数（UDF）。名为“mysql.proc name”的列指明了对应于INFORMATION_SCHEMA.ROUTINES表的mysql.proc表列。
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29 15、VIEWS表：给出了关于数据库中的视图的信息。需要有show views权限，否则无法查看视图信息。
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31 16、TRIGGERS表：提供了关于触发程序的信息。必须有super权限才能查看该表查看引擎
information_schema.ENGINS 对应于 show engines;
查看数据库
information_schema.SCHEMATA 对应于 show databases;
查看表
information_schema.TABLES 对应于 show tables;
查看列
information_schema.COLUMNS 对应于show columns from table_name
查看索引
information_schema.STATISTICS 对应于show index from table_name
查看线程
information_schema.PROCESSLIST 对应于 show processlist
二.MySQL 库表简介
在mysql数据库中，有mysql_install_db脚本初始化权限表，存储权限的表有：
1、user表: 用户列、权限列、安全列、资源控制列
2、db表 : 用户列、权限列
3、host表
4、table_priv表
5、columns_priv表
6、proc_priv表
三.sys库表简介
sys_config ： 这是在这个系统库上存在的唯一一个表了, 表结构如下：
CREATE TABLE `sys_config` (
`variable` varchar(128) NOT NULL,
`value` varchar(128) DEFAULT NULL,
`set_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`set_by` varchar(128) DEFAULT NULL,
PRIMARY KEY (`variable`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
• variable ： 配置选项名称
• value ： 配置选项值
• set_time： 该行配置修改的时间
• set_by ： 该行配置信息修改者，如果从被安装没有修改过，那么这个数据应该为NULL
这里写图片描述
以上值的会话变量为@sys.+表中variable字段，譬如：@sys.statement_truncate_len
可以set @sys.statement_truncate_len = 32 临时改变值，在会话中会一直使用这个值，如果想要恢复使用表的默认值，只需要将这个会话值设置为null；set @sys.statement_truncate_len = null;
• diagnostics.allow_i_s_tables : 默认为OFF ，如果开启表示允许diagnostics() 存储过程执行扫描information_schema.tables 表，如果表很多，那么可能会很耗性能，
• diagnostics.include_raw : 默认为OFF ， 开启将会从metrics 视图输出未加工处理的数据 。
• statement_performance_analyzer.limit : 视图在没有加limit限制时，返回的最大行数
• statement_performance_analyzer.view
• statement_truncate_len : 通过format_statement()函数返回值的最大长度
这个表非默认选项还有一个@sys.debug参数 , 可以手动加入:
INSERT INTO sys_config (variable, value) VALUES('debug', 'ON');
UPDATE sys_config SET value = 'OFF' WHERE variable = 'debug';
SET @sys.debug = NULL;四.performance_schema库表简介
1 performance_schema是运行在较低级别的用于监控MySQL Server运行过程中的资源消耗、资源等待等情况的一个功能特性，也是一个存储引擎。该特性具有以下特点。
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3 提供了一种在数据库运行时实时检查Server内部执行情况的方法
4 可监控任何事情以及对应的时间消耗，利用这些信息来判断Server中的相关资源消耗
5 只被记录在本地Server的performance_schema中，其表中数据发生变化时不会被写入binlog中，也不会通过复制机制被复制到其他Server中
6 对于这些表可使用SELECT语句查询，也可以使用SQL语句更新performance_schema数据库中的表记录，但不建议更新，会影响后续的数据收集
7 表中数据不会持久化存储在磁盘中，而是保存在内存中，一旦服务器重启，这些数据就会丢失
8 不会导致server的行为发生变化（查询，优化等）
9 总体上开销有限也不会影响性能
10 对某事件监测失败，不影响server正常运行
11 当针对一个数据，同时被performance_schema收集和查询，则收集优先与查询
12 事件监测点可进行配置- 查看是否当前数据库是否支持
mysql> sho engines;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'sho engines' at line 1
mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)
Support 为YES 表示支持- 查看该特性是否使能
1 mysql> show variables like 'performance_schema';
2 +--------------------+-------+
3 | Variable_name | Value |
4 +--------------------+-------+
5 | performance_schema | ON |
6 +--------------------+-------+
7 1 row in set (0.00 sec)
如果为off则表示未使能。该参数为只读参数，则可在mysql.cnf中进行配置后重启服务使用该引擎的这些表的分类
1）语句事件记录表
mysql> show tables like 'events_statement%';
+----------------------------------------------------+
| Tables_in_performance_schema (events_statement%) |
+----------------------------------------------------+
| events_statements_current | //当前语句事件表
| events_statements_histogram_by_digest | //历史语句事件表
| events_statements_histogram_global |
| events_statements_history |
| events_statements_history_long | //长语句历史事件表
| events_statements_summary_by_account_by_event_name | //聚合后的摘要表
| events_statements_summary_by_digest |
| events_statements_summary_by_host_by_event_name |
| events_statements_summary_by_program |
| events_statements_summary_by_thread_by_event_name |
| events_statements_summary_by_user_by_event_name |
| events_statements_summary_global_by_event_name |
+----------------------------------------------------+
12 rows in set (0.00 sec)
2）等待时间记录表
mysql> show tables like 'events_wait%';
+-----------------------------------------------+
| Tables_in_performance_schema (events_wait%) |
+-----------------------------------------------+
| events_waits_current |
| events_waits_history |
| events_waits_history_long |
| events_waits_summary_by_account_by_event_name |
| events_waits_summary_by_host_by_event_name |
| events_waits_summary_by_instance |
| events_waits_summary_by_thread_by_event_name |
| events_waits_summary_by_user_by_event_name |
| events_waits_summary_global_by_event_name |
+-----------------------------------------------+
9 rows in set (0.00 sec)
3）阶段事件记录表
mysql> show tables like 'events_stage%';
+------------------------------------------------+
| Tables_in_performance_schema (events_stage%) |
+------------------------------------------------+
| events_stages_current |
| events_stages_history |
| events_stages_history_long |
| events_stages_summary_by_account_by_event_name |
| events_stages_summary_by_host_by_event_name |
| events_stages_summary_by_thread_by_event_name |
| events_stages_summary_by_user_by_event_name |
| events_stages_summary_global_by_event_name |
+------------------------------------------------+
8 rows in set (0.00 sec)
4）事务事件记录表
mysql> show tables like 'events_transaction%';
+------------------------------------------------------+
| Tables_in_performance_schema (events_transaction%) |
+------------------------------------------------------+
| events_transactions_current |
| events_transactions_history |
| events_transactions_history_long |
| events_transactions_summary_by_account_by_event_name |
| events_transactions_summary_by_host_by_event_name |
| events_transactions_summary_by_thread_by_event_name |
| events_transactions_summary_by_user_by_event_name |
| events_transactions_summary_global_by_event_name |
+------------------------------------------------------+
8 rows in set (0.00 sec)
5）监控文件系统层调用的表
mysql> show tables like '%file%';
+---------------------------------------+
| Tables_in_performance_schema (%file%) |
+---------------------------------------+
| file_instances |
| file_summary_by_event_name |
| file_summary_by_instance |
+---------------------------------------+
3 rows in set (0.00 sec)
6）监视内存使用的表
mysql> show tables like '%memory%';
+-----------------------------------------+
| Tables_in_performance_schema (%memory%) |
+-----------------------------------------+
| memory_summary_by_account_by_event_name |
| memory_summary_by_host_by_event_name |
| memory_summary_by_thread_by_event_name |
| memory_summary_by_user_by_event_name |
| memory_summary_global_by_event_name |
+-----------------------------------------+
5 rows in set (0.00 sec)
7）动态对performance_schema进行配置的配置表
mysql> show tables like '%setup%';
+----------------------------------------+
| Tables_in_performance_schema (%setup%) |
+----------------------------------------+
| setup_actors |
| setup_consumers |
| setup_instruments |
| setup_objects |
| setup_threads |
+----------------------------------------+
5 rows in set (0.01 sec)查询性能表进行进行分析
两个基本概念
● instruments：生产者，用于采集MySQL中各种操作产生的事件信息，对应配置表中的配置项，我们可以称之为事件采集配置项。以下提及的生产者均统称为instruments。
● consumers：消费者，对应的消费者表用于存储来自instruments采集的数据，对应配置表中的配置项，我们可以称之为消费存储配置项。以下提及的消费者均统称为consumers。
1、哪类的SQL执行最多？
mysql> SELECT DIGEST_TEXT,COUNT_STAR,FIRST_SEEN,LAST_SEEN FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC
-> ;
+----------------------------------------------------------------------------------------------------------------------------------------+------------+----------------------------+----------------------------+
| DIGEST_TEXT | COUNT_STAR | FIRST_SEEN | LAST_SEEN |
+----------------------------------------------------------------------------------------------------------------------------------------+------------+----------------------------+----------------------------+
| SHOW VARIABLES LIKE ? | 4 | 2022-01-04 18:14:24.153156 | 2022-01-04 21:25:12.396097 |
| SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 3 | 2022-01-04 18:06:55.067124 | 2022-01-04 18:21:09.809550 |
2、哪类SQL的平均响应时间最多？
mysql> SELECT DIGEST_TEXT,AVG_TIMER_WAIT FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC ;
+----------------------------------------------------------------------------------------------------------------------------------------+----------------+
| DIGEST_TEXT | AVG_TIMER_WAIT |
+----------------------------------------------------------------------------------------------------------------------------------------+----------------+
| SHOW VARIABLES LIKE ? | 5867400000 |
| SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 42246300000 |
3、哪类SQL排序记录数最多？
mysql> SELECT DIGEST_TEXT,SUM_SORT_ROWS FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC;
+----------------------------------------------------------------------------------------------------------------------------------------+---------------+
| DIGEST_TEXT | SUM_SORT_ROWS |
+----------------------------------------------------------------------------------------------------------------------------------------+---------------+
| SHOW VARIABLES LIKE ? | 0 |
4、哪类SQL扫描记录数最多？
mysql> SELECT DIGEST_TEXT,SUM_ROWS_EXAMINED FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC;
+----------------------------------------------------------------------------------------------------------------------------------------+-------------------+
| DIGEST_TEXT | SUM_ROWS_EXAMINED |
+----------------------------------------------------------------------------------------------------------------------------------------+-------------------+
| SHOW VARIABLES LIKE ? | 51 |
5、哪类SQL使用临时表最多？
mysql> SELECT DIGEST_TEXT,SUM_CREATED_TMP_TABLES,SUM_CREATED_TMP_DISK_TABLES FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC;
+----------------------------------------------------------------------------------------------------------------------------------------+------------------------+-----------------------------+
| DIGEST_TEXT | SUM_CREATED_TMP_TABLES | SUM_CREATED_TMP_DISK_TABLES |
+----------------------------------------------------------------------------------------------------------------------------------------+------------------------+-----------------------------+
| SHOW VARIABLES LIKE ? | 4 | 0 |
| SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 0 | 0 |
6、哪类SQL返回结果集最多？
mysql> SELECT DIGEST_TEXT,SUM_ROWS_SENT FROM events_statements_summary_by_digest ORDER BY COUNT_STAR DESC;
+-------------------------------------------------------------------------------------------------------------------------------------------------------+---------------+
| DIGEST_TEXT | SUM_ROWS_SENT |
+-------------------------------------------------------------------------------------------------------------------------------------------------------+---------------+
| SHOW VARIABLES LIKE ? | 51 |
| SELECT NAME , TYPE , `thread_id` , `processlist_id` FROM `performance_schema` . `threads` WHERE TYPE = ? | 38 |
7、哪个表物理IO最多？
mysql> SELECT file_name,event_name,SUM_NUMBER_OF_BYTES_READ,SUM_NUMBER_OF_BYTES_WRITE FROM file_summary_by_instance ORDER BY SUM_NUMBER_OF_BYTES_READ + SUM_NUMBER_OF_BYTES_WRITE DESC;
+------------------------------------------+---------------------------------------+--------------------------+---------------------------+
| file_name | event_name | SUM_NUMBER_OF_BYTES_READ | SUM_NUMBER_OF_BYTES_WRITE |
+------------------------------------------+---------------------------------------+--------------------------+---------------------------+
| /var/lib/mysql/ibtmp1 | wait/io/file/innodb/innodb_data_file | 0 | 14729216 |
| /var/lib/mysql/#ib_16384_1.dblwr | wait/io/file/innodb/innodb_dblwr_file | 8585216 | 0 |
8、哪个表逻辑IO最多？
mysql> SELECT object_name,COUNT_READ,COUNT_WRITE,COUNT_FETCH,SUM_TIMER_WAIT FROM table_io_waits_summary_by_table ORDER BY sum_timer_wait DESC;
+------------------------------------------------------+------------+-------------+-------------+----------------+
| object_name | COUNT_READ | COUNT_WRITE | COUNT_FETCH | SUM_TIMER_WAIT |
+------------------------------------------------------+------------+-------------+-------------+----------------+
| books | 1 | 1 | 1 | 14683357736 |
| dd_properties | 0 | 0 | 0 | 0 |
9、哪个索引访问最多？mysql> SELECT OBJECT_NAME,INDEX_NAME,COUNT_FETCH,COUNT_INSERT,COUNT_UPDATE,COUNT_DELETE FROM table_io_waits_summary_by_index_usage ORDER BY SUM_TIMER_WAIT DESC;
+------------------------------------------------------+----------------------------------+-------------+--------------+--------------+--------------+
| OBJECT_NAME | INDEX_NAME | COUNT_FETCH | COUNT_INSERT | COUNT_UPDATE | COUNT_DELETE |
+------------------------------------------------------+----------------------------------+-------------+--------------+--------------+--------------+
| books | NULL | 1 | 1 | 0 | 0 | 10、哪个索引从来没有用过？
mysql> SELECT OBJECT_SCHEMA,OBJECT_NAME,INDEX_NAME FROM table_io_waits_summary_by_index_usage WHERE INDEX_NAME IS NOT NULL AND COUNT_STAR = 0 AND OBJECT_SCHEMA <> 'mysql' ORDER BY OBJECT_SCHEMA,OBJECT_NAME;
+--------------------+------------------------------------------------------+----------------------------------+
| OBJECT_SCHEMA | OBJECT_NAME | INDEX_NAME |
+--------------------+------------------------------------------------------+----------------------------------+
| cara_testing_db | books | PRIMARY |
| performance_schema | accounts | ACCOUNT | 11、哪个等待事件消耗时间最多？
mysql> SELECT EVENT_NAME,COUNT_STAR,SUM_TIMER_WAIT,AVG_TIMER_WAIT FROM events_waits_summary_global_by_event_name WHERE event_name != 'idle' ORDER BY SUM_TIMER_WAIT DESC ;
+---------------------------------------------------------------------+------------+----------------+----------------+
| EVENT_NAME | COUNT_STAR | SUM_TIMER_WAIT | AVG_TIMER_WAIT |
+---------------------------------------------------------------------+------------+----------------+----------------+
| wait/io/file/innodb/innodb_data_file | 1103 | 686179063712 | 622102240 |
| wait/io/file/innodb/innodb_dblwr_file | 30 | 118918612832 | 3963953732 |
| wait/io/file/innodb/innodb_log_file | 109 | 66884431760 | 613618552 | 12、剖析某条SQL的执行情况，包括statement信息，stege信息，wait信息
mysql> SELECT EVENT_ID,sql_text FROM events_statements_history WHERE sql_text LIKE '%count(*)%';
+----------+----------------------------+
| EVENT_ID | sql_text |
+----------+----------------------------+
| 155 | select count(*) from books |
+----------+----------------------------+
1 row in set (0.00 sec) 13、查看每个阶段的时间消耗
mysql> SELECT event_id,EVENT_NAME,SOURCE,TIMER_END - TIMER_START FROM events_stages_history_long WHERE NESTING_EVENT_ID = 1553
-> ;
Empty set (0.01 sec) 14、查看每个阶段的锁等待情况
mysql> SELECT event_id,event_name,source,timer_wait,object_name,index_name,operation,nesting_event_id FROM events_waits_history_long;
Do everything well
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