MySQL errors - Even the world's most popular open source database can fail

1. use mysql;
   --
   -- Table structure for table `gtid_slave_pos`
   --
   
   DROP TABLE IF EXISTS `gtid_slave_pos`;
   /*!40101 SET @saved_cs_client     = @@character_set_client */;
   /*!40101 SET character_set_client = utf8 */;
   CREATE TABLE `gtid_slave_pos` (
     `domain_id` int(10) unsigned NOT NULL,
     `sub_id` bigint(20) unsigned NOT NULL,
     `server_id` int(10) unsigned NOT NULL,
     `seq_no` bigint(20) unsigned NOT NULL,
     PRIMARY KEY (`domain_id`,`sub_id`)
   ) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='Replication slave GTID position';
   /*!40101 SET character_set_client = @saved_cs_client */;

   ERROR 1813 (HY000): Tablespace for table '`mysql`.`gtid_slave_pos`' exists. Please DISCARD the tablespace before IMPORT.

2. Ok, let's do this (source) :

   ALTER TABLE `mysql`.`gtid_slave_pos` DISCARD TABLESPACE;

   ERROR 1146 (42S02): Table 'mysql.gtid_slave_pos' doesn't exist

3. So I have some tablespace for a missing table () ???
   Seems like my "MySQL data" directory has orphan idb files (i.e. idb files having no frm mate, source). Let's find them :
   find /var/lib/mysql/data -type f -name "*ibd" | sed -r 's/\.ibd$/.frm/' | xargs -I foo bash -c 'ls foo &>/dev/null && : || echo foo'

   /var/lib/mysql/data/mysql/gtid_slave_pos.frm
   /var/lib/mysql/data/mysql/innodb_index_stats.frm
   /var/lib/mysql/data/mysql/innodb_table_stats.frm

   Now let's clean up (simulating file deletion) :
   for stuff in /var/lib/mysql/data/mysql/gtid_slave_pos.ibd /var/lib/mysql/data/mysql/innodb_index_stats.ibd /var/lib/mysql/data/mysql/innodb_table_stats.ibd; do mv "$stuff" "${stuff}_DISABLED"; done
4. After that, I've been able to drop + create table gtid_slave_pos

--
-- Dumping data for table `gtid_slave_pos`
--

LOCK TABLES `gtid_slave_pos` WRITE;
/*!40000 ALTER TABLE `gtid_slave_pos` DISABLE KEYS */;
/*!40000 ALTER TABLE `gtid_slave_pos` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `innodb_index_stats`
--

DROP TABLE IF EXISTS `innodb_index_stats`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
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;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `innodb_index_stats`
--

LOCK TABLES `innodb_index_stats` WRITE;
/*!40000 ALTER TABLE `innodb_index_stats` DISABLE KEYS */;
/*!40000 ALTER TABLE `innodb_index_stats` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `innodb_table_stats`
--

DROP TABLE IF EXISTS `innodb_table_stats`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
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;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `innodb_table_stats`
--

LOCK TABLES `innodb_table_stats` WRITE;
/*!40000 ALTER TABLE `innodb_table_stats` DISABLE KEYS */;
/*!40000 ALTER TABLE `innodb_table_stats` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `slave_master_info`
--

DROP TABLE IF EXISTS `slave_master_info`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
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';
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `slave_master_info`
--

LOCK TABLES `slave_master_info` WRITE;
/*!40000 ALTER TABLE `slave_master_info` DISABLE KEYS */;
/*!40000 ALTER TABLE `slave_master_info` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `slave_relay_log_info`
--

DROP TABLE IF EXISTS `slave_relay_log_info`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
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';
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `slave_relay_log_info`
--

LOCK TABLES `slave_relay_log_info` WRITE;
/*!40000 ALTER TABLE `slave_relay_log_info` DISABLE KEYS */;
/*!40000 ALTER TABLE `slave_relay_log_info` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `slave_worker_info`
--

DROP TABLE IF EXISTS `slave_worker_info`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
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';
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `slave_worker_info`
--

LOCK TABLES `slave_worker_info` WRITE;
/*!40000 ALTER TABLE `slave_worker_info` DISABLE KEYS */;
/*!40000 ALTER TABLE `slave_worker_info` ENABLE KEYS */;
UNLOCK TABLES;