为什么要避免大事务以及大事务如何解决？

select * from information_schema.innodb_trx where TIME_TO_SEC(timediff(now(),trx_started))>10

# 查询所有正在运行的事务及运行时间

select t.*,to_seconds(now())-to_seconds(t.trx_started) idle_time from INFORMATION_SCHEMA.INNODB_TRX t



# 查询事务详细信息及执行的SQL

select now(),(UNIX_TIMESTAMP(now()) - UNIX_TIMESTAMP(a.trx_started)) diff_sec,b.id,b.user,b.host,b.db,d.SQL_TEXT from information_schema.innodb_trx a inner join information_schema.PROCESSLIST b

on a.TRX_MYSQL_THREAD_ID=b.id and b.command = 'Sleep'

inner join performance_schema.threads c ON b.id = c.PROCESSLIST_ID

inner join performance_schema.events_statements_current d ON d.THREAD_ID = c.THREAD_ID;



# 查询事务执行过的所有历史SQL记录

SELECT

  ps.id 'PROCESS ID',

  ps.USER,

  ps.HOST,

  esh.EVENT_ID,

  trx.trx_started,

  esh.event_name 'EVENT NAME',

  esh.sql_text 'SQL',

  ps.time 

FROM

  PERFORMANCE_SCHEMA.events_statements_history esh

  JOIN PERFORMANCE_SCHEMA.threads th ON esh.thread_id = th.thread_id

  JOIN information_schema.PROCESSLIST ps ON ps.id = th.processlist_id

  LEFT JOIN information_schema.innodb_trx trx ON trx.trx_mysql_thread_id = ps.id 

WHERE

  trx.trx_id IS NOT NULL 

  AND ps.USER != 'SYSTEM_USER' 

ORDER BY

  esh.EVENT_ID;

  

 # 简单查询事务锁

 select * from sys.innodb_lock_waits

 

 # 查询事务锁详细信息

 SELECT

  tmp.*,

  c.SQL_Text blocking_sql_text,

  p.HOST blocking_host 

FROM

  (

  SELECT

    r.trx_state wating_trx_state,

    r.trx_id waiting_trx_id,

    r.trx_mysql_thread_Id waiting_thread,

    r.trx_query waiting_query,

    b.trx_state blocking_trx_state,

    b.trx_id blocking_trx_id,

    b.trx_mysql_thread_id blocking_thread,

    b.trx_query blocking_query 

  FROM

    information_schema.innodb_lock_waits w

    INNER JOIN information_schema.innodb_trx b ON b.trx_id = w.blocking_trx_id

    INNER JOIN information_schema.innodb_trx r ON r.trx_id = w.requesting_trx_id 

  ) tmp,

  information_schema.PROCESSLIST p,

  PERFORMANCE_SCHEMA.events_statements_current c,

  PERFORMANCE_SCHEMA.threads t 

WHERE

  tmp.blocking_thread = p.id 

  AND t.thread_id = c.THREAD_ID 

  AND t.PROCESSLIST_ID = p.id