This table provides details of the transactions handled by applier threads on a replica or Group Replication group member. For a single-threaded replica, data is shown for the replica’s single applier thread. For a multithreaded replica, data is shown individually for each applier thread. The applier threads on a multithreaded replica are sometimes called workers. The number of applier threads on a replica or Group Replication group member is set by the slave_parallel_workers system variable, which is set to zero for a single-threaded replica. A multithreaded replica also has a coordinator thread to manage the applier threads, and the status of this thread is shown in the replication_applier_status_by_coordinator  table. 

All error codes and messages displayed in the columns relating to errors correspond to error values listed in Server Error Message Reference. 

When the Performance Schema is disabled, local timing information is not collected, so the fields showing the start and end timestamps for applied transactions are zero. The start timestamps in this table refer to when the worker started applying the first event, and the end timestamps refer to when the last event of the transaction was applied. 

When a replica is restarted by a START REPLICA | SLAVE  statement, the columns beginning APPLYING_TRANSACTION  are reset. Before MySQL 8.0.13, these columns were not reset on a replica that was operating in single-threaded mode, only on a multithreaded replica. 

The replication_applier_status_by_worker  table has these columns: 

• CHANNEL_NAME 

The replication channel which this row is displaying. There is always a default replication channel, and more replication channels can be added. See Section 17.2.2, “Replication Channels”  for more information. 

• WORKER_ID 

The worker identifier (same value as the id  column in the mysql.slave_worker_info  table). After STOP REPLICA | SLAVE , the THREAD_ID  column becomes NULL , but the WORKER_ID  value is preserved. 

• THREAD_ID 

The worker thread ID. 

• SERVICE_STATE 

ON  (thread exists and is active or idle) or OFF  (thread no longer exists). 

• LAST_ERROR_NUMBER , LAST_ERROR_MESSAGE 

The error number and error message of the most recent error that caused the worker thread to stop. An error number of 0 and message of the empty string mean “no error” . If the LAST_ERROR_MESSAGE  value is not empty, the error values also appear in the replica’s error log. 

Issuing RESET MASTER  or RESET REPLICA | SLAVE  resets the values shown in these columns. 

• LAST_ERROR_TIMESTAMP 

A timestamp in ’ YYYY-MM-DD hh:mm:ss [. fraction ]’  format that shows when the most recent worker error occurred. 

• LAST_APPLIED_TRANSACTION 

