Mysql之performance Schema

Performance schema是用于监控Mysql执行，具有如下特征：

　　1.用于在运行时探查Mysql Server的执行过程，是由Performance_schema引擎和 Performance_schema库实现的，侧重于性能数据，而非元数据【INFORMATION_SCHEMA】.

　　2.Performance Schema监控Server Event.an event could be a function call, a wait for the operating system, a stage of an SQL statement execution such as parsing or sorting, or an entire statement or group of statements.

　　3.Performance Schema表的更改不会被写入binLog中。

　　Performance_schema,默认是开的。

如　　：

要想查看Server当前正在干什么，可查看events_waits_current.查询历史最近的events,可查询：events_waits_history,events_waits_history_long.

可配置其保存条数：

[mysqld]
performance_schema
performance_schema_events_waits_history_size=20
performance_schema_events_waits_history_long_size=15000

Performance Schema 运行时配置：

　　Performance Schema setup表包含监控配置的相关信息。

　　查看和更新事件定时器【event timer】，可参考： Performance Schema Runtime Configuration

The setup_objects table controls whether the Performance Schema monitors particular table and stored program objects.

对setup_objects表的修改会立即生效。如：

会对所有自定义的库，表监控。

threads表记录每一个server线程，包括线程信息及指示monitor是否已经启动。若要使Performance schema监控一个线程，以下必须为TRUE:

setup_consumers表里的thread_instrumentation必须为YES,select * from setup_consumers where name ='thread_instrumentation';

The threads.INSTRUMENTED column must be YES.

Wait Instrument Components：

wait/io： wait/io/file 　wait/io/socket   wait/io/table

wait/lock：wait/lock/table      wait/lock/metadata/sql/mdl

23.9.7.1 The events_transactions_current Table