29.12.21.5 The log_status Table

The log_status table provides information that enables an online backup tool to copy the required log files without locking those resources for the duration of the copy process.

When the log_status table is queried, the server blocks logging and related administrative changes for just long enough to populate the table, then releases the resources. The log_status table informs the online backup which point it should copy up to in the source's binary log and gtid_executed record, and the relay log for each replication channel. It also provides relevant information for individual storage engines, such as the last log sequence number (LSN) and the LSN of the last checkpoint taken for the InnoDB storage engine.

The log_status table has these columns:

• SERVER_UUID

  The server UUID for this server instance. This is the generated unique value of the read-only system variable server_uuid.

• LOCAL

  The log position state information from the source, provided as a single JSON object with the following keys:

  binary_log_file

  The name of the current binary log file.

  binary_log_position

  The current binary log position at the time the log_status table was accessed.

  gtid_executed

  The current value of the global server variable gtid_executed at the time the log_status table was accessed. This information is consistent with the binary_log_file and binary_log_position keys.

• REPLICATION

  A JSON array of channels, each with the following information:

  channel_name

  The name of the replication channel. The default replication channel's name is the empty string (“”).

  relay_log_file

  The name of the current relay log file for the replication channel.

  relay_log_pos

  The current relay log position at the time the log_status table was accessed.

• STORAGE_ENGINES

  Relevant information from individual storage engines, provided as a JSON object with one key for each applicable storage engine.

The log_status table has no indexes.

The BACKUP_ADMIN privilege, as well as the SELECT privilege, is required for access to the log_status table.

TRUNCATE TABLE is not permitted for the log_status table.