【MySQL】5.6.x InnoDB Error Table mysql.innodb_table_stats not found

【问题描述】：
检查error log的时候发现大量warnings：
[Warning] InnoDB Error Table mysql.innodb_index_stats not found
[Warning] InnoDB Error Table mysql.innodb_table_stats not found
[Warning] InnoDB Error Table mysql.slave_master_info not found
[Warning] InnoDB Error Table mysql.slave_relay_log_info not found
[Warning] InnoDB Error Table mysql.slave_worker_info not found

或在打开innodb表时，在err-log里会打印出：
 InnoDB: Error: Table "mysql"."innodb_table_stats" not found.
 Error: Fetch of persistent statistics requested for table "{databse_name}"."{table_name}"
but the required system tables mysql.innodb_table_stats and
mysql.innodb_index_stats are not present or have unexpected structure.
Using transient stats instead.

【解决方案】：
先看看能否drop table，如果说表不存在，则继续下一步。

1. DROP TABLE mysql.innodb_index_stats;
2. DROP TABLE mysql.innodb_table_stats;
3. DROP TABLE mysql.slave_master_info;
4. DROP TABLE mysql.slave_relay_log_info;
5. DROP TABLE mysql.slave_worker_info;

删除datadir下mysql数据库中的这五张表的frm文件（如有ibd也一并删除）

1. rm -rf $datadir/mysql/innodb_index_stats.*
2. rm -rf $datadir/mysql/innodb_table_stats.*
3. rm -rf $datadir/mysql/slave_master_info.*
4. rm -rf $datadir/mysql/slave_relay_log_info.*
5. rm -rf $datadir/mysql/slave_worker_info.*

再执行如下语句，重新创建这五张表：

     USE mysql;

    CREATE TABLE `innodb_index_stats` (
      `database_name` varchar(64) COLLATE utf8_bin NOT NULL,
      `table_name` varchar(64) COLLATE utf8_bin NOT NULL,
      `index_name` varchar(64) COLLATE utf8_bin NOT NULL,
      `last_update` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
      `stat_name` varchar(64) COLLATE utf8_bin NOT NULL,
      `stat_value` bigint(20) unsigned NOT NULL,
      `sample_size` bigint(20) unsigned DEFAULT NULL,
      `stat_description` varchar(1024) COLLATE utf8_bin NOT NULL,
      PRIMARY KEY (`database_name`,`table_name`,`index_name`,`stat_name`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin STATS_PERSISTENT=0;

    CREATE TABLE `innodb_table_stats` (
      `database_name` varchar(64) COLLATE utf8_bin NOT NULL,
      `table_name` varchar(64) COLLATE utf8_bin NOT NULL,
      `last_update` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
      `n_rows` bigint(20) unsigned NOT NULL,
      `clustered_index_size` bigint(20) unsigned NOT NULL,
      `sum_of_other_index_sizes` bigint(20) unsigned NOT NULL,
      PRIMARY KEY (`database_name`,`table_name`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin STATS_PERSISTENT=0;

    CREATE TABLE `slave_master_info` (
      `Number_of_lines` int(10) unsigned NOT NULL COMMENT 'Number of lines in the file.',
      `Master_log_name` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL COMMENT 'The name of the master binary log currently being read from the master.',
      `Master_log_pos` bigint(20) unsigned NOT NULL COMMENT 'The master log position of the last read event.',
      `Host` char(64) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL DEFAULT '' COMMENT 'The host name of the master.',
      `User_name` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The user name used to connect to the master.',
      `User_password` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The password used to connect to the master.',
      `Port` int(10) unsigned NOT NULL COMMENT 'The network port used to connect to the master.',
      `Connect_retry` int(10) unsigned NOT NULL COMMENT 'The period (in seconds) that the slave will wait before trying to reconnect to the master.',
      `Enabled_ssl` tinyint(1) NOT NULL COMMENT 'Indicates whether the server supports SSL connections.',
      `Ssl_ca` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The file used for the Certificate Authority (CA) certificate.',
      `Ssl_capath` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The path to the Certificate Authority (CA) certificates.',
      `Ssl_cert` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The name of the SSL certificate file.',
      `Ssl_cipher` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The name of the cipher in use for the SSL connection.',
      `Ssl_key` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The name of the SSL key file.',
      `Ssl_verify_server_cert` tinyint(1) NOT NULL COMMENT 'Whether to verify the server certificate.',
      `Heartbeat` float NOT NULL,
      `Bind` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'Displays which interface is employed when connecting to the MySQL server',
      `Ignored_server_ids` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The number of server IDs to be ignored, followed by the actual server IDs',
      `Uuid` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The master server uuid.',
      `Retry_count` bigint(20) unsigned NOT NULL COMMENT 'Number of reconnect attempts, to the master, before giving up.',
      `Ssl_crl` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The file used for the Certificate Revocation List (CRL)',
      `Ssl_crlpath` text CHARACTER SET utf8 COLLATE utf8_bin COMMENT 'The path used for Certificate Revocation List (CRL) files',
      `Enabled_auto_position` tinyint(1) NOT NULL COMMENT 'Indicates whether GTIDs will be used to retrieve events from the master.',
      PRIMARY KEY (`Host`,`Port`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8 STATS_PERSISTENT=0 COMMENT='Master Information';

    CREATE TABLE `slave_relay_log_info` (
      `Number_of_lines` int(10) unsigned NOT NULL COMMENT 'Number of lines in the file or rows in the table. Used to version table definitions.',
      `Relay_log_name` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL COMMENT 'The name of the current relay log file.',
      `Relay_log_pos` bigint(20) unsigned NOT NULL COMMENT 'The relay log position of the last executed event.',
      `Master_log_name` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL COMMENT 'The name of the master binary log file from which the events in the relay log file were read.',
      `Master_log_pos` bigint(20) unsigned NOT NULL COMMENT 'The master log position of the last executed event.',
      `Sql_delay` int(11) NOT NULL COMMENT 'The number of seconds that the slave must lag behind the master.',
      `Number_of_workers` int(10) unsigned NOT NULL,
      `Id` int(10) unsigned NOT NULL COMMENT 'Internal Id that uniquely identifies this record.',
      PRIMARY KEY (`Id`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8 STATS_PERSISTENT=0 COMMENT='Relay Log Information';

    CREATE TABLE `slave_worker_info` (
      `Id` int(10) unsigned NOT NULL,
      `Relay_log_name` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
      `Relay_log_pos` bigint(20) unsigned NOT NULL,
      `Master_log_name` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
      `Master_log_pos` bigint(20) unsigned NOT NULL,
      `Checkpoint_relay_log_name` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
      `Checkpoint_relay_log_pos` bigint(20) unsigned NOT NULL,
      `Checkpoint_master_log_name` text CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
      `Checkpoint_master_log_pos` bigint(20) unsigned NOT NULL,
      `Checkpoint_seqno` int(10) unsigned NOT NULL,
      `Checkpoint_group_size` int(10) unsigned NOT NULL,
      `Checkpoint_group_bitmap` blob NOT NULL,
      PRIMARY KEY (`Id`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8 STATS_PERSISTENT=0 COMMENT='Worker Information';

最后重启mysqld即可。