FLUSH ERROR LOGS FLUSH GENERAL LOGS FLUSH RELAY LOGS FLUSH SLOW LOGS 

• FLUSH OPTIMIZER_COSTS 

Re-reads the cost model tables so that the optimizer starts using the current cost estimates stored in them. 

This operation requires the FLUSH_OPTIMIZER_COSTS  or RELOAD  privilege. 

The server writes a warning to the error log for any unrecognized cost model table entries. For information about these tables, see Section 8.9.5, “The Optimizer Cost Model” . This operation affects only sessions that begin subsequent to the flush. Existing sessions continue to use the cost estimates that were current when they began. 

• FLUSH PRIVILEGES 

Re-reads the privileges from the grant tables in the mysql  system schema. As part of this operation, the server reads the global_grants  table containing dynamic privilege assignments and registers any unregistered privileges found there. 

This operation requires the RELOAD  privilege. 

If the --skip-grant-tables  option was specified at server startup to disable the MySQL privilege system, FLUSH PRIVILEGES  provides a way to enable the privilege system at runtime. 

Resets failed-login tracking (or enables it if the server was started with --skip-grant-tables ) and unlocks any temporarily locked accounts. See Section 6.2.15, “Password Management” . 

Frees memory cached by the server as a result of GRANT , CREATE USER , CREATE SERVER , and INSTALL PLUGIN  statements. This memory is not released by the corresponding REVOKE , DROP USER , DROP SERVER , and UNINSTALL PLUGIN  statements, so for a server that executes many instances of the statements that cause caching, there is an increase in cached memory use unless it is freed with FLUSH PRIVILEGES . 

Clears the in-memory cache used by the caching_sha2_password  authentication plugin. See Cache Operation for SHA-2 Pluggable Authentication. 

• FLUSH RELAY LOGS [FOR CHANNEL channel ] 

Closes and reopens any relay log file to which the server is writing. If relay logging is enabled, the sequence number of the relay log file is incremented by one relative to the previous file. 

This operation requires the RELOAD  privilege. 

The FOR CHANNEL channel  clause enables you to name which replication channel the operation applies to. Execute FLUSH RELAY LOGS FOR CHANNEL channel  to flush the relay log for a specific replication channel. If no channel is named and no extra replication channels exist, the operation applies to the default channel. If no channel is named and multiple replication channels exist, the operation applies to all replication channels. For more information, see Section 17.2.2, “Replication Channels” . 

• FLUSH SLOW LOGS 

Closes and reopens any slow query log file to which the server is writing. 

This operation requires the RELOAD  privilege. 

