- GreatSQL社区原创内容未经受权不得随便应用，转载请分割小编并注明起源。
- GreatSQL是MySQL的国产分支版本，应用上与MySQL统一。
- 作者： bruce
- 文章起源：GreatSQL社区原创
什么是events_statements_current表
在MySQL中，PFS下有一张内存表: events_statements_current，看到这个名称"xxx_current"，小白如我可能会认为这张表中的数据就是以后零碎的沉闷(active)语句。该表的形容如下(有局部省略):
mysql> desc events_statements_current;+-------------------------+------------------------------------------------+------+-----+---------+-------+| Field | Type | Null | Key | Default | Extra |+-------------------------+------------------------------------------------+------+-----+---------+-------+| THREAD_ID | bigint unsigned | NO | PRI | NULL | || EVENT_ID | bigint unsigned | NO | PRI | NULL | || END_EVENT_ID | bigint unsigned | YES | | NULL | || EVENT_NAME | varchar(128) | NO | | NULL | || SOURCE | varchar(64) | YES | | NULL | || TIMER_START | bigint unsigned | YES | | NULL | || TIMER_END | bigint unsigned | YES | | NULL | || TIMER_WAIT | bigint unsigned | YES | | NULL | || LOCK_TIME | bigint unsigned | NO | | NULL | || SQL_TEXT | longtext | YES | | NULL | || DIGEST | varchar(64) | YES | | NULL | || DIGEST_TEXT | longtext | YES | | NULL | || CURRENT_SCHEMA | varchar(64) | YES | | NULL | |...| MYSQL_ERRNO | int | YES | | NULL | || RETURNED_SQLSTATE | varchar(5) | YES | | NULL | || MESSAGE_TEXT | varchar(128) | YES | | NULL | |...+-------------------------+------------------------------------------------+------+-----+---------+-------+44 rows in set (0.01 sec)间接应用以后语句表的问题
间接做个小试验，终端1：
SELECT sleep(1);终端2：
USE performance_schema;-- 查看最近用户语句SELECT s.thread_id, s.sql_text FROM events_statements_current s, threads t WHERE s.thread_id = t.thread_id AND t.type = 'FOREGROUND';输入:
mysql> SELECT s.thread_id, s.sql_text FROM events_statements_current s, threads t WHERE s.thread_id = t.thread_id AND t.type = 'FOREGROUND';+-----------+--------------------------------------------------------------------------------------------------------------------------------------+| thread_id | sql_text |+-----------+--------------------------------------------------------------------------------------------------------------------------------------+| 58 | select sleep(1) || 1849 | SELECT s.thread_id, s.sql_text FROM events_statements_current s, threads t WHERE s.thread_id = t.thread_id AND t.type = 'FOREGROUND' |+-----------+--------------------------------------------------------------------------------------------------------------------------------------+2 rows in set (0.00 sec)重复执行上述语句，发现终端1以后执行的语句都是：SELECT sleep(1)，看起来有点像BUG呀 。
真的是这样吗? 来细看一下文档的定义：
The events_statements_current table contains current statement events. The table stores one row per thread showing the current status of the thread's most recent monitored statement event, so there is no system variable for configuring the table size.
发现了一些要害信息: "showing the current status of the thread's most recent monitored statement event"，也就是说：保留的是线程最近被检测到的语句事件，并非以后正在处于执行状态的语句
获取以后沉闷的语句办法
为了理解这个问题的解决方案，来看看具体实现的代码：
void pfs_end_statement_vc(PSI_statement_locker *locker, void *stmt_da) { PSI_statement_locker_state *state = reinterpret_cast<PSI_statement_locker_state *>(locker); ... if (state->m_discarded) { return; } ... // storage/perfschema/pfs.cc:6462 if (flags & STATE_FLAG_TIMED) { timer_end = get_statement_timer(); wait_time = timer_end - state->m_timer_start; } ... if (flags & STATE_FLAG_THREAD) { ... if(flags & STATE_FLAG_EVENT) { ... // storage/perfschema/pfs.cc:6528 pfs->m_timer_end = timer_end; pfs->m_cpu_time = cpu_time; pfs->m_end_event_id = thread->m_event_id; ... } }阐明，在语句运行完结的时候，PFS会更新记录：
- m_timer_end 运行完结工夫
- m_end_event_id 语句完结事件ID
持续浏览代码，发现除了在：pfs_start_statement_vc中对该值进行初始化外，批改该值的代码仅有这一处，根本能够得出结论：m_timer_end > 0 或 m_end_event_id >0 代表语句运行曾经完结。
整个繁难工具测一下:
. ./setenvFOR i IN $(seq 1 1000000)DOmysql -h127.0.0.1 -P3306 -uroot <<EOFUSE performance_schema;-- 打印所有的进行中用户SQL(除了本身)SELECT s.* FROM events_statements_current s, threads t WHERE s.thread_id = t.thread_id AND t.type = 'FOREGROUND' AND sql_text like '%FOREGROUND%' = FALSE AND s.end_event_id IS NULL \GEOF sleep 0.1 # 每0.1秒跑一下DONE运行后果:
*************************** 1. row *************************** THREAD_ID: 15082 EVENT_ID: 127 END_EVENT_ID: NULL EVENT_NAME: statement/sql/select SOURCE: init_net_server_extension.cc:95 TIMER_START: 19879433851621000 TIMER_END: 19880288626029000 TIMER_WAIT: 854774408000 LOCK_TIME: 0 SQL_TEXT: select sleep(1), 3...将工具SQL替换成
-- 移除原来的 s.end_event_id is NULLSELECT s.* FROM events_statements_current s, threads t WHERE s.thread_id = t.thread_id AND t.type = 'FOREGROUND' AND sql_text like '%FOREGROUND%' = FALSE AND s.timer_end = 0 \G再次运行：
## 真的是啥也没有啊，真的是啥也没有啊，再认真看看文档 (https://dev.mysql.com/doc/ref...):
TIMER_START, TIMER_END, TIMER_WAITTiming information for the event. The unit for these values is picoseconds (trillionths of a second). The TIMER_START and TIMER_END values indicate when event timing started and ended. TIMER_WAIT is the event elapsed time (duration).If an event has not finished, TIMER_END is the current timer value and TIMER_WAIT is the time elapsed so far (TIMER_END − TIMER_START).重要信息: 当事件没有实现，TIMER_END会继续参考以后工夫更新
与设想的很不一样，无奈关上源码，看看有什么线索
//storage/perfschema/table_events_statements.cc:315(table_events_statements_common) if (m_row.m_end_event_id == 0) { timer_end = get_statement_timer(); } else { timer_end = statement->m_timer_end; }换句话说：运行未完结时，statement->m_timer_end的值的确是0，然而timer_end赋值用的是语句计时器的以后工夫。
测试论断：events_statements_current能够用于形容以后沉闷语句，沉闷这个条件能够应用：END_EVENT_ID IS NULL来过滤。
Enjoy GreatSQL :)
## 对于 GreatSQL
GreatSQL是由万里数据库保护的MySQL分支，专一于晋升MGR可靠性及性能，反对InnoDB并行查问个性，是实用于金融级利用的MySQL分支版本。
相干链接： GreatSQL社区 Gitee GitHub Bilibili
GreatSQL社区：
社区博客有奖征稿详情：https://greatsql.cn/thread-10...
技术交换群：
微信：扫码增加GreatSQL社区助手微信好友，发送验证信息加群。