一、现象
使用备份软件备份报错
ERROR 1356 (HY000): View 'sys.host_summary' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them

二、原因
检查sys表是否损坏
mysql> select if(isnull('performance_schema'.'accounts'.'HOST'),'background','performance_schema'.'accounts'.'HOST')
AS 'host',sum('stmt'.'total') AS 'statements','sys'.'format_time'(sum('stmt'.'total_latency')) AS 'statement_latency','sys'.'format_time'(ifnull((sum('stmt'.'total_latency') / nullif(sum('stmt'.'total'),0)),0))
AS 'statement_avg_latency',sum('stmt'.'full_scans') AS 'table_scans',sum('io'.'ios') AS 'file_ios','sys'.'format_time'(sum('io'.'io_latency')) AS 'file_io_latency',sum('performance_schema'.'accounts'.'CURRENT_CONNECTIONS')
AS 'current_connections',sum('performance_schema'.'accounts'.'TOTAL_CONNECTIONS') AS 'total_connections',count(distinct 'performance_schema'.'accounts'.'USER') AS 'unique_users','sys'.'format_bytes'(sum('mem'.'current_allocated'))
AS 'current_memory','sys'.'format_bytes'(sum('mem'.'total_allocated')) AS 'total_memory_allocated' from
((('performance_schema'.'accounts' join
'sys'.'x$host_summary_by_statement_latency' 'stmt' on(('performance_schema'.'accounts'.'HOST' = 'stmt'.'host')))
join 'sys'.'x$host_summary_by_file_io' 'io' on(('performance_schema'.'accounts'.'HOST' = 'io'.'host')))
join 'sys'.'x$memory_by_host_by_current_bytes'
'mem' on(('performance_schema'.'accounts'.'HOST' = 'mem'.'host')))
group by if(isnull('performance_schema'.'accounts'.'HOST'),'background','performance_schema'.'accounts'.'HOST');
returns
ERROR 1305 (42000): FUNCTION sys.format_time does not exist

三、解决方法
如果主从库都有此问题，先从从库执行，再执行主库，mysql_upgrade不会使gtid变化，但是drop database 命令会使gtid变化，所以我们要关闭掉基于会话的sql_log_bin。

  1. STOP SLAVE;
  2. SET SQL_LOG_BIN=0;
  3. DROP DATABASE sys;
  4. SET SQL_LOG_BIN=1;
  5. Run mysql_upgrade
  6. START SLAVE;