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怎么理解MySQL5.6中的PERFORMANCE_SCHEM
本篇内容介绍了“怎么理解MySQL5.6中的PERFORMANCE_SCHEM”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！
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通过sql语句找到在经历什么等待事件!
Statement -> stage -> wait的三级结构，通过nesting_event_id进行关联，它表示某个事件的父event_id。
比如分析包含count(*)的某条SQL语句，具体如下：(类似于oracle的v$sql, v$sqlstat, v$sqlarea)
SELECT
EVENT_ID,
sql_text
FROM events_statements_history
WHERE sql_text LIKE '%count(*)%';
+----------+--------------------------------------+
| EVENT_ID | sql_text |
+----------+--------------------------------------+
| 1690 | select count(*) from chuck.test_slow |
+----------+--------------------------------------+
a.查看每个阶段的时间消耗：(类似于oracle的时间模型V$SYS_TIME_MODEL V$SESS_TIME_MODEL)
SELECT
event_id,
EVENT_NAME,
SOURCE,
TIMER_END - TIMER_START
FROM events_stages_history_long
WHERE NESTING_EVENT_ID = 1690;
+----------+--------------------------------+----------------------+-----------------------+
| event_id | EVENT_NAME | SOURCE | TIMER_END-TIMER_START |
+----------+--------------------------------+----------------------+-----------------------+
……
| 2647 | stage/sql/Sending data | sql_executor.cc:192 | 7369072089000 |
b.查看某个阶段的锁等待情况 (类似于oracle的v$session_wait)
针对每个stage可能出现的锁等待，一个stage会对应一个或多个wait，events_waits_history_long这个表容易爆满[默认阀值10000]。由于select count(*)需要IO(逻辑IO或者物理IO)，所以在stage/sql/Sending data阶段会有io等待的统计。通过stage_xxx表的event_id字段与waits_xxx表的nesting_event_id进行关联。
SELECT
event_id,
event_name,
source,
timer_wait,
object_name,
index_name,
operation,
nesting_event_id
FROM events_waits_history_long
WHERE nesting_event_id = 2647;
+----------+---------------------------+-----------------+------------+-------------+------------+-----------+------------------+
| event_id | event_name | source | timer_wait | object_name | index_name | operation | nesting_event_id |
+----------+---------------------------+-----------------+------------+-------------+------------+-----------+------------------+
| 190607 | wait/io/table/sql/handler | handler.cc:2842 | 1845888 | test_slow | idx_c1 | fetch | 2647 |
https://www.cnblogs.com/zhoujinyi/p/5236705.html
MySQL5.6 PERFORMANCE_SCHEMA 说明
背景：
MySQL 5.5开始新增一个数据库：PERFORMANCE_SCHEMA，主要用于收集数据库服务器性能参数。并且库里表的存储引擎均为PERFORMANCE_SCHEMA，而用户是不能创建存储引擎为PERFORMANCE_SCHEMA的表。MySQL5.5默认是关闭的，需要手动开启，在配置文件里添加：
[mysqld]
performance_schema=ON
查看是否开启：
mysql>show variables like 'performance_schema';
+--------------------+-------+
| Variable_name | Value |
+--------------------+-------+
| performance_schema | ON |
+--------------------+-------+
从MySQL5.6开始，默认打开，本文就从MySQL5.6来说明，在数据库使用当中PERFORMANCE_SCHEMA的一些比较常用的功能。具体的信息可以查看官方文档。
相关表信息：
一：配置（setup）表：
zjy@performance_schema 10:16:56>show tables like '%setup%';
+----------------------------------------+
| Tables_in_performance_schema (%setup%) |
+----------------------------------------+
| setup_actors |
| setup_consumers |
| setup_instruments |
| setup_objects |
| setup_timers |
+----------------------------------------+
1，setup_actors：配置用户纬度的监控，默认监控所有用户。
zjy@performance_schema 10:19:11>select * from setup_actors;
+------+------+------+
| HOST | USER | ROLE |
+------+------+------+
| % | % | % |
+------+------+------+
2，setup_consumers：配置events的消费者类型，即收集的events写入到哪些统计表中。
zjy@: performance_schema 10:23:35>select * from setup_consumers;
+--------------------------------+---------+
| NAME | ENABLED |
+--------------------------------+---------+
| events_stages_current | NO |
| events_stages_history | NO |
| events_stages_history_long | NO |
| events_statements_current | YES |
| events_statements_history | NO |
| events_statements_history_long | NO |
| events_waits_current | NO |
| events_waits_history | NO |
| events_waits_history_long | NO |
| global_instrumentation | YES |
| thread_instrumentation | YES |
| statements_digest | YES |
+--------------------------------+---------+
这里需要说明的是需要查看哪个就更新其ENABLED列为YES。如：
zjy@performance_schema 10:25:02>update setup_consumers set ENABLED='YES' where NAME in ('events_stages_current','events_waits_current');
Query OK, 2 rows affected (0.00 sec)
更新完后立即生效，但是服务器重启之后又会变回默认值，要永久生效需要在配置文件里添加：
[mysqld]
#performance_schema
performance_schema_consumer_events_waits_current=on
performance_schema_consumer_events_stages_current=on
performance_schema_consumer_events_statements_current=on
performance_schema_consumer_events_waits_history=on
performance_schema_consumer_events_stages_history=on
performance_schema_consumer_events_statements_history=on
即在这些表的前面加上：performance_schema_consumer_xxx。表setup_consumers里面的值有个层级关系：
global_instrumentation > thread_instrumentation = statements_digest > events_stages_current = events_statements_current = events_waits_current > events_stages_history = events_statements_history = events_waits_history > events_stages_history_long = events_statements_history_long = events_waits_history_long
只有上一层次的为YES，才会继续检查该本层为YES or NO。global_instrumentation是最高级别consumer，如果它设置为NO，则所有的consumer都会忽略。其中history和history_long存的是current表的历史记录条数，history表记录了每个线程最近等待的10个事件，而history_long表则记录了最近所有线程产生的10000个事件，这里的10和10000都是可以配置的。这三个表表结构相同，history和history_long表数据都来源于current表。长度通过控制参数：
zjy@performance_schema 11:10:03>show variables like 'performance_schema%history%size';
+--------------------------------------------------------+-------+
| Variable_name | Value |
+--------------------------------------------------------+-------+
| performance_schema_events_stages_history_long_size | 10000 |
| performance_schema_events_stages_history_size | 10 |
| performance_schema_events_statements_history_long_size | 10000 |
| performance_schema_events_statements_history_size | 10 |
| performance_schema_events_waits_history_long_size | 10000 |
| performance_schema_events_waits_history_size | 10 |
+--------------------------------------------------------+-------+
3，setup_instruments：配置具体的instrument，主要包含4大类：idle、stage/xxx、statement/xxx、wait/xxx：
zjy@performance_schema 10:56:35>select name,count(*) from setup_instruments group by LEFT(name,5);
+---------------------------------+----------+
| name | count(*) |
+---------------------------------+----------+
| idle | 1 |
| stage/sql/After create | 111 |
| statement/sql/select | 179 |
| wait/synch/mutex/sql/PAGE::lock | 296 |
+---------------------------------+----------+
idle表示socket空闲的时间，stage类表示语句的每个执行阶段的统计，statement类统计语句维度的信息，wait类统计各种等待事件，比如IO，mutux，spin_lock,condition等。
4，setup_objects：配置监控对象，默认对mysql，performance_schema和information_schema中的表都不监控，而其它DB的所有表都监控。
zjy@performance_schema 11:00:18>select * from setup_objects;
+-------------+--------------------+-------------+---------+-------+
| OBJECT_TYPE | OBJECT_SCHEMA | OBJECT_NAME | ENABLED | TIMED |
+-------------+--------------------+-------------+---------+-------+
| TABLE | mysql | % | NO | NO |
| TABLE | performance_schema | % | NO | NO |
| TABLE | information_schema | % | NO | NO |
| TABLE | % | % | YES | YES |
+-------------+--------------------+-------------+---------+-------+
5，setup_timers：配置每种类型指令的统计时间单位。MICROSECOND表示统计单位是微妙，CYCLE表示统计单位是时钟周期，时间度量与CPU的主频有关，NANOSECOND表示统计单位是纳秒。但无论采用哪种度量单位，最终统计表中统计的时间都会装换到皮秒。（1秒＝1000000000000皮秒）
zjy@performance_schema 11:05:12>select * from setup_timers;
+-----------+-------------+
| NAME | TIMER_NAME |
+-----------+-------------+
| idle | MICROSECOND |
| wait | CYCLE |
| stage | NANOSECOND |
| statement | NANOSECOND |
+-----------+-------------+
二：instance表
1，cond_instances：条件等待对象实例
表中记录了系统中使用的条件变量的对象，OBJECT_INSTANCE_BEGIN为对象的内存地址。
2，file_instances：文件实例
表中记录了系统中打开了文件的对象，包括ibdata文件，redo文件，binlog文件，用户的表文件等，open_count显示当前文件打开的数目，如果重来没有打开过，不会出现在表中。
zjy@performance_schema 11:20:04>select * from file_instances limit 2,5;
+---------------------------------+--------------------------------------+------------+
| FILE_NAME | EVENT_NAME | OPEN_COUNT |
+---------------------------------+--------------------------------------+------------+
| /var/lib/mysql/mysql/plugin.frm | wait/io/file/sql/FRM | |
| /var/lib/mysql/mysql/plugin.MYI | wait/io/file/myisam/kfile | 1 |
| /var/lib/mysql/mysql/plugin.MYD | wait/io/file/myisam/dfile | 1 |
| /var/lib/mysql/ibdata1 | wait/io/file/innodb/innodb_data_file | 2 |
| /var/lib/mysql/ib_logfile0 | wait/io/file/innodb/innodb_log_file | 2 |
+---------------------------------+--------------------------------------+------------+
3，mutex_instances：互斥同步对象实例
表中记录了系统中使用互斥量对象的所有记录，其中name为：wait/synch/mutex/*。LOCKED_BY_THREAD_ID显示哪个线程正持有mutex，若没有线程持有，则为NULL。
4，rwlock_instances： 读写锁同步对象实例
表中记录了系统中使用读写锁对象的所有记录，其中name为 wait/synch/rwlock/*。WRITE_LOCKED_BY_THREAD_ID为正在持有该对象的thread_id，若没有线程持有，则为NULL。READ_LOCKED_BY_COUNT为记录了同时有多少个读者持有读锁。（通过 events_waits_current 表可以知道，哪个线程在等待锁；通过rwlock_instances知道哪个线程持有锁。rwlock_instances的缺陷是，只能记录持有写锁的线程，对于读锁则无能为力）。
5，socket_instances：活跃会话对象实例
表中记录了thread_id,socket_id,ip和port，其它表可以通过thread_id与socket_instance进行关联，获取IP-PORT信息，能够与应用对接起来。
event_name主要包含3类：
wait/io/socket/sql/server_unix_socket，服务端unix监听socket
wait/io/socket/sql/server_tcpip_socket，服务端tcp监听socket
wait/io/socket/sql/client_connection，客户端socket
三：Wait表
1，events_waits_current：记录了当前线程等待的事件
2，events_waits_history：记录了每个线程最近等待的10个事件
3，events_waits_history_long：记录了最近所有线程产生的10000个事件
表结构定义如下：
CREATE TABLE `events_waits_current` (
`THREAD_ID` bigint(20) unsigned NOT NULL COMMENT '线程ID',
`EVENT_ID` bigint(20) unsigned NOT NULL COMMENT '当前线程的事件ID，和THREAD_ID确定唯一',
`END_EVENT_ID` bigint(20) unsigned DEFAULT NULL COMMENT '当事件开始时，这一列被设置为NULL。当事件结束时，再更新为当前的事件ID',
`EVENT_NAME` varchar(128) NOT NULL COMMENT '事件名称',
`SOURCE` varchar(64) DEFAULT NULL COMMENT '该事件产生时的源码文件',
`TIMER_START` bigint(20) unsigned DEFAULT NULL COMMENT '事件开始时间（皮秒）',
`TIMER_END` bigint(20) unsigned DEFAULT NULL COMMENT '事件结束结束时间（皮秒）',
`TIMER_WAIT` bigint(20) unsigned DEFAULT NULL COMMENT '事件等待时间（皮秒）',
`SPINS` int(10) unsigned DEFAULT NULL COMMENT '',
`OBJECT_SCHEMA` varchar(64) DEFAULT NULL COMMENT '库名',
`OBJECT_NAME` varchar(512) DEFAULT NULL COMMENT '文件名、表名、IP:SOCK值',
`OBJECT_TYPE` varchar(64) DEFAULT NULL COMMENT 'FILE、TABLE、TEMPORARY TABLE',
`INDEX_NAME` varchar(64) DEFAULT NULL COMMENT '索引名',
`OBJECT_INSTANCE_BEGIN` bigint(20) unsigned NOT NULL COMMENT '内存地址',
`NESTING_EVENT_ID` bigint(20) unsigned DEFAULT NULL COMMENT '该事件对应的父事件ID',
`NESTING_EVENT_TYPE` enum('STATEMENT','STAGE','WAIT') DEFAULT NULL COMMENT '父事件类型(STATEMENT, STAGE, WAIT)',
`OPERATION` varchar(32) NOT NULL COMMENT '操作类型（lock, read, write）',
`NUMBER_OF_BYTES` bigint(20) DEFAULT NULL COMMENT '',
`FLAGS` int(10) unsigned DEFAULT NULL COMMENT '标记'
) ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8
四：Stage 表
1，events_stages_current：记录了当前线程所处的执行阶段
2，events_stages_history：记录了当前线程所处的执行阶段10条历史记录
3，events_stages_history_long：记录了当前线程所处的执行阶段10000条历史记录
表结构定义如下：
CREATE TABLE `events_stages_current` (
`THREAD_ID` bigint(20) unsigned NOT NULL COMMENT '线程ID',
`EVENT_ID` bigint(20) unsigned NOT NULL COMMENT '事件ID',
`END_EVENT_ID` bigint(20) unsigned DEFAULT NULL COMMENT '结束事件ID',
`EVENT_NAME` varchar(128) NOT NULL COMMENT '事件名称',
`SOURCE` varchar(64) DEFAULT NULL COMMENT '源码位置',
`TIMER_START` bigint(20) unsigned DEFAULT NULL COMMENT '事件开始时间（皮秒）',
`TIMER_END` bigint(20) unsigned DEFAULT NULL COMMENT '事件结束结束时间（皮秒）',
`TIMER_WAIT` bigint(20) unsigned DEFAULT NULL COMMENT '事件等待时间（皮秒）',
`NESTING_EVENT_ID` bigint(20) unsigned DEFAULT NULL COMMENT '该事件对应的父事件ID',
`NESTING_EVENT_TYPE` enum('STATEMENT','STAGE','WAIT') DEFAULT NULL COMMENT '父事件类型(STATEMENT, STAGE, WAIT)'
) ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8
五：Statement 表
1，events_statements_current：通过 thread_id+event_id可以唯一确定一条记录。Statments表只记录最顶层的请求，SQL语句或是COMMAND，每条语句一行。event_name形式为statement/sql/*，或statement/com/*
2，events_statements_history
3，events_statements_history_long
表结构定义如下：
CREATE TABLE `events_statements_current` (
`THREAD_ID` bigint(20) unsigned NOT NULL COMMENT '线程ID',
`EVENT_ID` bigint(20) unsigned NOT NULL COMMENT '事件ID',
`END_EVENT_ID` bigint(20) unsigned DEFAULT NULL COMMENT '结束事件ID',
`EVENT_NAME` varchar(128) NOT NULL COMMENT '事件名称',
`SOURCE` varchar(64) DEFAULT NULL COMMENT '源码位置',
`TIMER_START` bigint(20) unsigned DEFAULT NULL COMMENT '事件开始时间（皮秒）',
`TIMER_END` bigint(20) unsigned DEFAULT NULL COMMENT '事件结束结束时间（皮秒）',
`TIMER_WAIT` bigint(20) unsigned DEFAULT NULL COMMENT '事件等待时间（皮秒）',
`LOCK_TIME` bigint(20) unsigned NOT NULL COMMENT '锁时间',
`SQL_TEXT` longtext COMMENT '记录SQL语句',
`DIGEST` varchar(32) DEFAULT NULL COMMENT '对SQL_TEXT做MD5产生的32位字符串',
`DIGEST_TEXT` longtext COMMENT '将语句中值部分用问号代替，用于SQL语句归类',
`CURRENT_SCHEMA` varchar(64) DEFAULT NULL COMMENT '默认的数据库名',
`OBJECT_TYPE` varchar(64) DEFAULT NULL COMMENT '保留字段',
`OBJECT_SCHEMA` varchar(64) DEFAULT NULL COMMENT '保留字段',
`OBJECT_NAME` varchar(64) DEFAULT NULL COMMENT '保留字段',
`OBJECT_INSTANCE_BEGIN` bigint(20) unsigned DEFAULT NULL COMMENT '内存地址',
`MYSQL_ERRNO` int(11) DEFAULT NULL COMMENT '',
`RETURNED_SQLSTATE` varchar(5) DEFAULT NULL COMMENT '',
`MESSAGE_TEXT` varchar(128) DEFAULT NULL COMMENT '信息',
`ERRORS` bigint(20) unsigned NOT NULL COMMENT '错误数目',
`WARNINGS` bigint(20) unsigned NOT NULL COMMENT '警告数目',
`ROWS_AFFECTED` bigint(20) unsigned NOT NULL COMMENT '影响的数目',
`ROWS_SENT` bigint(20) unsigned NOT NULL COMMENT '返回的记录数',
`ROWS_EXAMINED` bigint(20) unsigned NOT NULL COMMENT '读取扫描的记录数目',
`CREATED_TMP_DISK_TABLES` bigint(20) unsigned NOT NULL COMMENT '创建磁盘临时表数目',
`CREATED_TMP_TABLES` bigint(20) unsigned NOT NULL COMMENT '创建临时表数目',
`SELECT_FULL_JOIN` bigint(20) unsigned NOT NULL COMMENT 'join时，第一个表为全表扫描的数目',
`SELECT_FULL_RANGE_JOIN` bigint(20) unsigned NOT NULL COMMENT '引用表采用range方式扫描的数目',
`SELECT_RANGE` bigint(20) unsigned NOT NULL COMMENT 'join时，第一个表采用range方式扫描的数目',
`SELECT_RANGE_CHECK` bigint(20) unsigned NOT NULL COMMENT '',
`SELECT_SCAN` bigint(20) unsigned NOT NULL COMMENT 'join时，第一个表位全表扫描的数目',
`SORT_MERGE_PASSES` bigint(20) unsigned NOT NULL COMMENT '',
`SORT_RANGE` bigint(20) unsigned NOT NULL COMMENT '范围排序数目',
`SORT_ROWS` bigint(20) unsigned NOT NULL COMMENT '排序的记录数目',
`SORT_SCAN` bigint(20) unsigned NOT NULL COMMENT '全表排序数目',
`NO_INDEX_USED` bigint(20) unsigned NOT NULL COMMENT '没有使用索引数目',
`NO_GOOD_INDEX_USED` bigint(20) unsigned NOT NULL COMMENT '',
`NESTING_EVENT_ID` bigint(20) unsigned DEFAULT NULL COMMENT '该事件对应的父事件ID',
`NESTING_EVENT_TYPE` enum('STATEMENT','STAGE','WAIT') DEFAULT NULL COMMENT '父事件类型(STATEMENT, STAGE, WAIT)'
) ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8
六：Connection 表
1，users：记录用户连接数信息
2，hosts：记录了主机连接数信息
3，accounts：记录了用户主机连接数信息
zjy@performance_schema 12:03:27>select * from users;
+------------------+---------------------+-------------------+
| USER | CURRENT_CONNECTIONS | TOTAL_CONNECTIONS |
+------------------+---------------------+-------------------+
| debian-sys-maint | | 36 |
| zjy | 1 | 22285 |
| dchat_php | | 37864 |
| dxyslave | 2 | 9 |
| nagios | | 10770 |
| dchat_data | 140 | 2233023 |
| NULL | | 15866 |
| dchat_api | 160 | 2754212 |
| mha_data | 1 | 36 |
| backup | | 15 |
| cacti | | 4312 |
| kol | 10 | 172414 |
+------------------+---------------------+-------------------+
12 rows in set (0.00 sec)
zjy@performance_schema 12:03:34>select * from hosts;
+-----------------+---------------------+-------------------+
| HOST | CURRENT_CONNECTIONS | TOTAL_CONNECTIONS |
+-----------------+---------------------+-------------------+
| 192.168.100.218 | 150 | 2499422 |
| 192.168.100.240 | 10 | 172429 |
| 192.168.100.139 | | 698 |
| 192.168.100.21 | | 2 |
| 192.168.100.220 | 150 | 2526136 |
| 192.168.100.25 | 1 | 7 |
| NULL | | 15867 |
| 192.168.100.241 | | 21558 |
| 192.168.100.191 | 1 | 34 |
| localhost | | 10807 |
| 192.168.100.118 | 1 | 2 |
| 192.168.100.251 | | 4312 |
| 192.168.100.23 | 1 | 31 |
| 192.168.100.193 | | 15 |
+-----------------+---------------------+-------------------+
14 rows in set (0.01 sec)
zjy@performance_schema 12:05:21>select * from accounts;
+------------------+-----------------+---------------------+-------------------+
| USER | HOST | CURRENT_CONNECTIONS | TOTAL_CONNECTIONS |
+------------------+-----------------+---------------------+-------------------+
| cacti | 192.168.100.251 | | 4313 |
| debian-sys-maint | localhost | | 36 |
| backup | 192.168.100.193 | | 15 |
| dchat_api | 192.168.100.220 | 80 | 1382585 |
| dchat_php | 192.168.100.220 | | 20292 |
| zjy | 192.168.100.139 | | 698 |
| zjy | 192.168.100.241 | | 21558 |
| mha_data | 192.168.100.191 | 1 | 34 |
| dxyslave | 192.168.100.118 | 1 | 2 |
| kol | 192.168.100.240 | 10 | 172431 |
| dxyslave | 192.168.100.25 | 1 | 7 |
| dchat_data | 192.168.100.218 | 70 | 1109974 |
| zjy | 192.168.100.23 | 1 | 31 |
| dchat_php | 192.168.100.218 | | 17572 |
| dchat_data | 192.168.100.220 | 70 | 1123306 |
| NULL | NULL | | 15868 |
| mha_data | 192.168.100.21 | | 2 |
| dchat_api | 192.168.100.218 | 80 | 1371918 |
| nagios | localhost | | 10771 |
+------------------+-----------------+---------------------+-------------------+
View Code
七：Summary 表： Summary表聚集了各个维度的统计信息包括表维度，索引维度，会话维度，语句维度和锁维度的统计信息
1，events_waits_summary_global_by_event_name：按等待事件类型聚合，每个事件一条记录
CREATE TABLE `events_waits_summary_global_by_event_name` (
`EVENT_NAME` varchar(128) NOT NULL COMMENT '事件名称',
`COUNT_STAR` bigint(20) unsigned NOT NULL COMMENT '事件计数',
`SUM_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '总的等待时间',
`MIN_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '最小等待时间',
`AVG_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '平均等待时间',
`MAX_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '最大等待时间'
) ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8
2，events_waits_summary_by_instance：按等待事件对象聚合，同一种等待事件，可能有多个实例，每个实例有不同的内存地址，因此
event_name+object_instance_begin唯一确定一条记录。
CREATE TABLE `events_waits_summary_by_instance` (
`EVENT_NAME` varchar(128) NOT NULL COMMENT '事件名称',
`OBJECT_INSTANCE_BEGIN` bigint(20) unsigned NOT NULL COMMENT '内存地址',
`COUNT_STAR` bigint(20) unsigned NOT NULL COMMENT '事件计数',
`SUM_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '总的等待时间',
`MIN_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '最小等待时间',
`AVG_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '平均等待时间',
`MAX_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '最大等待时间'
) ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8
3，events_waits_summary_by_thread_by_event_name：按每个线程和事件来统计，thread_id+event_name唯一确定一条记录。
CREATE TABLE `events_waits_summary_by_thread_by_event_name` (
`THREAD_ID` bigint(20) unsigned NOT NULL COMMENT '线程ID',
`EVENT_NAME` varchar(128) NOT NULL COMMENT '事件名称',
`COUNT_STAR` bigint(20) unsigned NOT NULL COMMENT '事件计数',
`SUM_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '总的等待时间',
`MIN_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '最小等待时间',
`AVG_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '平均等待时间',
`MAX_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '最大等待时间'
) ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8
4，events_stages_summary_global_by_event_name：按事件阶段类型聚合，每个事件一条记录，表结构同上。
5，events_stages_summary_by_thread_by_event_name：按每个线程和事件来阶段统计，表结构同上。
6，events_statements_summary_by_digest：按照事件的语句进行聚合。
CREATE TABLE `events_statements_summary_by_digest` (
`SCHEMA_NAME` varchar(64) DEFAULT NULL COMMENT '库名',
`DIGEST` varchar(32) DEFAULT NULL COMMENT '对SQL_TEXT做MD5产生的32位字符串。如果为consumer表中没有打开statement_digest选项，则为NULL',
`DIGEST_TEXT` longtext COMMENT '将语句中值部分用问号代替，用于SQL语句归类。如果为consumer表中没有打开statement_digest选项，则为NULL。',
`COUNT_STAR` bigint(20) unsigned NOT NULL COMMENT '事件计数',
`SUM_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '总的等待时间',
`MIN_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '最小等待时间',
`AVG_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '平均等待时间',
`MAX_TIMER_WAIT` bigint(20) unsigned NOT NULL COMMENT '最大等待时间',
`SUM_LOCK_TIME` bigint(20) unsigned NOT NULL COMMENT '锁时间总时长',
`SUM_ERRORS` bigint(20) unsigned NOT NULL COMMENT '错误数的总',
`SUM_WARNINGS` bigint(20) unsigned NOT NULL COMMENT '警告的总数',
`SUM_ROWS_AFFECTED` bigint(20) unsigned NOT NULL COMMENT '影响的总数目',
`SUM_ROWS_SENT` bigint(20) unsigned NOT NULL COMMENT '返回总数目',
`SUM_ROWS_EXAMINED` bigint(20) unsigned NOT NULL COMMENT '总的扫描的数目',
`SUM_CREATED_TMP_DISK_TABLES` bigint(20) unsigned NOT NULL COMMENT '创建磁盘临时表的总数目',
`SUM_CREATED_TMP_TABLES` bigint(20) unsigned NOT NULL COMMENT '创建临时表的总数目',
`SUM_SELECT_FULL_JOIN` bigint(20) unsigned NOT NULL COMMENT '第一个表全表扫描的总数目',
`SUM_SELECT_FULL_RANGE_JOIN` bigint(20) unsigned NOT NULL COMMENT '总的采用range方式扫描的数目',
`SUM_SELECT_RANGE` bigint(20) unsigned NOT NULL COMMENT '第一个表采用range方式扫描的总数目',
`SUM_SELECT_RANGE_CHECK` bigint(20) unsigned NOT NULL COMMENT '',
`SUM_SELECT_SCAN` bigint(20) unsigned NOT NULL COMMENT '第一个表位全表扫描的总数目',
`SUM_SORT_MERGE_PASSES` bigint(20) unsigned NOT NULL COMMENT '',
`SUM_SORT_RANGE` bigint(20) unsigned NOT NULL COMMENT '范围排序总数',
`SUM_SORT_ROWS` bigint(20) unsigned NOT NULL COMMENT '排序的记录总数目',
`SUM_SORT_SCAN` bigint(20) unsigned NOT NULL COMMENT '第一个表排序扫描总数目',
`SUM_NO_INDEX_USED` bigint(20) unsigned NOT NULL COMMENT '没有使用索引总数',
`SUM_NO_GOOD_INDEX_USED` bigint(20) unsigned NOT NULL COMMENT '',
`FIRST_SEEN` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00' COMMENT '第一次执行时间',
`LAST_SEEN` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00' COMMENT '最后一次执行时间'
) ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8
7，events_statements_summary_global_by_event_name：按照事件的语句进行聚合。表结构同上。
8，events_statements_summary_by_thread_by_event_name：按照线程和事件的语句进行聚合，表结构同上。
9，file_summary_by_instance：按事件类型统计（物理IO维度）
10，file_summary_by_event_name：具体文件统计（物理IO维度）
9和10一起说明：
统计IO操作：COUNT_STAR，SUM_TIMER_WAIT,MIN_TIMER_WAIT,AVG_TIMER_WAIT,MAX_TIMER_WAIT
统计读 ：COUNT_READ,SUM_TIMER_READ,MIN_TIMER_READ,AVG_TIMER_READ,MAX_TIMER_READ, SUM_NUMBER_OF_BYTES_READ
统计写 ：COUNT_WRITE,SUM_TIMER_WRITE,MIN_TIMER_WRITE,AVG_TIMER_WRITE,MAX_TIMER_WRITE, SUM_NUMBER_OF_BYTES_WRITE
统计其他IO事件，比如create，delete，open，close等：COUNT_MISC,SUM_TIMER_MISC,MIN_TIMER_MISC,AVG_TIMER_MISC,MAX_TIMER_MISC
11，table_io_waits_summary_by_table：根据wait/io/table/sql/handler，聚合每个表的I/O操作（逻辑IO纬度）
统计IO操作：COUNT_STAR,SUM_TIMER_WAIT,MIN_TIMER_WAIT,AVG_TIMER_WAIT,MAX_TIMER_WAIT
统计读 ：COUNT_READ,SUM_TIMER_READ,MIN_TIMER_READ,AVG_TIMER_READ,MAX_TIMER_READ
：COUNT_FETCH,SUM_TIMER_FETCH,MIN_TIMER_FETCH,AVG_TIMER_FETCH, MAX_TIMER_FETCH
统计写 ：COUNT_WRITE,SUM_TIMER_WRITE,MIN_TIMER_WRITE,AVG_TIMER_WRITE,MAX_TIMER_WRITE
INSERT统计，相应的还有DELETE和UPDATE统计：COUNT_INSERT,SUM_TIMER_INSERT,MIN_TIMER_INSERT,AVG_TIMER_INSERT,MAX_TIMER_INSERT
12，table_io_waits_summary_by_index_usage：与table_io_waits_summary_by_table类似，按索引维度统计
13，table_lock_waits_summary_by_table：聚合了表锁等待事件，包括internal lock 和 external lock
internal lock通过SQL层函数thr_lock调用，OPERATION值为：
read normal、read with shared locks、read high priority、read no insert、write allow write、write concurrent insert、write delayed、write low priority、write normal
external lock则通过接口函数handler::external_lock调用存储引擎层，OPERATION列的值为：read external、write external
14，Connection Summaries表：account、user、host
events_waits_summary_by_account_by_event_name
events_waits_summary_by_user_by_event_name
events_waits_summary_by_host_by_event_name
events_stages_summary_by_account_by_event_name
events_stages_summary_by_user_by_event_name
events_stages_summary_by_host_by_event_name
events_statements_summary_by_account_by_event_name
events_statements_summary_by_user_by_event_name
events_statements_summary_by_host_by_event_name
15，socket_summary_by_instance、socket_summary_by_event_name：socket聚合统计表。
八：其他相关表
1，performance_timers：系统支持的统计时间单位
2，threads：监视服务端的当前运行的线程
统计应用：
关于SQL维度的统计信息主要集中在events_statements_summary_by_digest表中，通过将SQL语句抽象出digest，可以统计某类SQL语句在各个维度的统计信息
1，哪个SQL执行最多：
zjy@performance_schema 11:36:22>SELECT SCHEMA_NAME,DIGEST_TEXT,COUNT_STAR,SUM_ROWS_SENT,SUM_ROWS_EXAMINED,FIRST_SEEN,LAST_SEEN FROM events_statements_summary_by_digest ORDER BY COUNT_STAR desc LIMIT 1\G
*************************** 1. row ***************************
SCHEMA_NAME: dchat
DIGEST_TEXT: SELECT ...
COUNT_STAR: 1161210102
SUM_ROWS_SENT: 1161207842
SUM_ROWS_EXAMINED:
FIRST_SEEN: 2016-02-17 00:36:46
LAST_SEEN: 2016-03-07 11:36:29
各个字段的注释可以看上面的表结构说明：从2月17号到3月7号该SQL执行了1161210102次。
2，哪个SQL平均响应时间最多：
zjy@performance_schema 11:36:28>SELECT SCHEMA_NAME,DIGEST_TEXT,COUNT_STAR,AVG_TIMER_WAIT,SUM_ROWS_SENT,SUM_ROWS_EXAMINED,FIRST_SEEN,LAST_SEEN FROM events_statements_summary_by_digest ORDER BY AVG_TIMER_WAIT desc LIMIT 1\G
*************************** 1. row ***************************
SCHEMA_NAME: dchat
DIGEST_TEXT: SELECT ...
COUNT_STAR: 1
AVG_TIMER_WAIT: 273238183964000
SUM_ROWS_SENT: 50208
SUM_ROWS_EXAMINED: 5565651
FIRST_SEEN: 2016-02-22 13:27:33
LAST_SEEN: 2016-02-22 13:27:33
各个字段的注释可以看上面的表结构说明：从2月17号到3月7号该SQL平均响应时间273238183964000皮秒（1000000000000皮秒=1秒）
3，哪个SQL扫描的行数最多：
SUM_ROWS_EXAMINED
4，哪个SQL使用的临时表最多：
SUM_CREATED_TMP_DISK_TABLES、SUM_CREATED_TMP_TABLES
5，哪个SQL返回的结果集最多：
SUM_ROWS_SENT
6，哪个SQL排序数最多：
SUM_SORT_ROWS
通过上述指标我们可以间接获得某类SQL的逻辑IO(SUM_ROWS_EXAMINED)，CPU消耗(SUM_SORT_ROWS)，网络带宽(SUM_ROWS_SENT)的对比。
通过file_summary_by_instance表，可以获得系统运行到现在，哪个文件(表)物理IO最多，这可能意味着这个表经常需要访问磁盘IO。
7，哪个表、文件逻辑IO最多（热数据）：
zjy@performance_schema 12:16:18>SELECT FILE_NAME,EVENT_NAME,COUNT_READ,SUM_NUMBER_OF_BYTES_READ,COUNT_WRITE,SUM_NUMBER_OF_BYTES_WRITE FROM file_summary_by_instance ORDER BY SUM_NUMBER_OF_BYTES_READ+SUM_NUMBER_OF_BYTES_WRITE DESC LIMIT 2\G
*************************** 1. row ***************************
FILE_NAME: /var/lib/mysql/ibdata1 #文件
新闻名称：怎么理解MySQL5.6中的PERFORMANCE_SCHEM
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