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MySQL Replication  /  ...  /  Replication and Temporary Tables

4.1.30 Replication and Temporary Tables

In MySQL 8.0, when binlog_format is set to ROW or MIXED, statements that exclusively use temporary tables are not logged on the source, and therefore the temporary tables are not replicated. Statements that involve a mix of temporary and nontemporary tables are logged on the source only for the operations on nontemporary tables, and the operations on temporary tables are not logged. This means that there are never any temporary tables on the replica to be lost in the event of an unplanned shutdown by the replica. For more information about row-based replication and temporary tables, see Row-based logging of temporary tables.

When binlog_format is set to STATEMENT, operations on temporary tables are logged on the source and replicated on the replica, provided that the statements involving temporary tables can be logged safely using statement-based format. In this situation, loss of replicated temporary tables on the replica can be an issue. In statement-based replication mode, CREATE TEMPORARY TABLE and DROP TEMPORARY TABLE statements cannot be used inside a transaction, procedure, function, or trigger when GTIDs are in use on the server (that is, when the enforce_gtid_consistency system variable is set to ON). They can be used outside these contexts when GTIDs are in use, provided that autocommit=1 is set.

Because of the differences in behavior between row-based or mixed replication mode and statement-based replication mode regarding temporary tables, you cannot switch the replication format at runtime, if the change applies to a context (global or session) that contains any open temporary tables. For more details, see the description of the binlog_format option.

Safe replica shutdown when using temporary tables.  In statement-based replication mode, temporary tables are replicated except in the case where you stop the replica server (not just the replication threads) and you have replicated temporary tables that are open for use in updates that have not yet been executed on the replica. If you stop the replica server, the temporary tables needed by those updates are no longer available when the replica is restarted. To avoid this problem, do not shut down the replica while it has temporary tables open. Instead, use the following procedure:

  1. Issue a STOP SLAVE SQL_THREAD statement.

  2. Use SHOW STATUS to check the value of the Slave_open_temp_tables variable.

  3. If the value is not 0, restart the replication SQL thread with START SLAVE SQL_THREAD and repeat the procedure later.

  4. When the value is 0, issue a mysqladmin shutdown command to stop the replica.

Temporary tables and replication options.  By default, with statement-based replication, all temporary tables are replicated; this happens whether or not there are any matching --replicate-do-db, --replicate-do-table, or --replicate-wild-do-table options in effect. However, the --replicate-ignore-table and --replicate-wild-ignore-table options are honored for temporary tables. The exception is that to enable correct removal of temporary tables at the end of a session, a replica always replicates a DROP TEMPORARY TABLE IF EXISTS statement, regardless of any exclusion rules that would normally apply for the specified table.

A recommended practice when using statement-based replication is to designate a prefix for exclusive use in naming temporary tables that you do not want replicated, then employ a --replicate-wild-ignore-table option to match that prefix. For example, you might give all such tables names beginning with norep (such as norepmytable, norepyourtable, and so on), then use --replicate-wild-ignore-table=norep% to prevent them from being replicated.