Syntax

FLUSH [NO_WRITE_TO_BINLOG | LOCAL]
    flush_option [, flush_option] ...

or when flushing tables:

FLUSH [NO_WRITE_TO_BINLOG | LOCAL] TABLES [table_list]  [table_flush_option]

where table_list is a list of tables separated by , (comma).

Description

The FLUSH statement clears or reloads various internal caches used by MariaDB. To execute FLUSH, you must have the RELOAD privilege. See GRANT.

The RESET statement is similar to FLUSH. See RESET.

You cannot issue a FLUSH statement from within a stored function or a trigger. Doing so within a stored procedure is permitted, as long as it is not called by a stored function or trigger. See Stored Routine Limitations, Stored Function Limitations and Trigger Limitations.

If a listed table is a view, an error like the following will be produced:

ERROR 1347 (HY000): 'test.v' is not BASE TABLE

By default, FLUSH statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

The different flush options are:

You can also use the mysqladmin client to flush things. Use mysqladmin --help to examine what flush commands it supports.

FLUSH STATUS

Server status variables can be reset by executing the following:

FLUSH STATUS;

Global Status Variables that Support FLUSH STATUS

Not all global status variables support being reset by FLUSH STATUS. Currently, the following status variables are reset by FLUSH STATUS:

• Aborted_clients
• Aborted_connects
• Aria_pagecache_blocks_not_flushed
• Aria_pagecache_blocks_unused
• Aria_pagecache_blocks_used
• Binlog_cache_disk_use
• Binlog_cache_use
• Binlog_stmt_cache_disk_use
• Binlog_stmt_cache_use
• Connection_errors_accept
• Connection_errors_internal
• Connection_errors_max_connections
• Connection_errors_peer_address
• Connection_errors_select
• Connection_errors_tcpwrap
• Created_tmp_files
• Delayed_errors
• Delayed_writes
• Feature_check_constraint
• Feature_delay_key_write
• Max_used_connections
• Opened_plugin_libraries
• Performance_schema_accounts_lost
• Performance_schema_cond_instances_lost
• Performance_schema_digest_lost
• Performance_schema_file_handles_lost
• Performance_schema_file_instances_lost
• Performance_schema_hosts_lost
• Performance_schema_locker_lost
• Performance_schema_mutex_instances_lost
• Performance_schema_rwlock_instances_lost
• Performance_schema_session_connect_attrs_lost
• Performance_schema_socket_instances_lost
• Performance_schema_stage_classes_lost
• Performance_schema_statement_classes_lost
• Performance_schema_table_handles_lost
• Performance_schema_table_instances_lost
• Performance_schema_thread_instances_lost
• Performance_schema_users_lost
• Qcache_hits
• Qcache_inserts
• Qcache_lowmem_prunes
• Qcache_not_cached
• Rpl_semi_sync_master_no_times
• Rpl_semi_sync_master_no_tx
• Rpl_semi_sync_master_timefunc_failures
• Rpl_semi_sync_master_wait_pos_backtraverse
• Rpl_semi_sync_master_yes_tx
• Rpl_transactions_multi_engine
• Server_audit_writes_failed
• Slave_retried_transactions
• Slow_launch_threads
• Ssl_accept_renegotiates
• Ssl_accepts
• Ssl_callback_cache_hits
• Ssl_client_connects
• Ssl_connect_renegotiates
• Ssl_ctx_verify_depth
• Ssl_ctx_verify_mode
• Ssl_finished_accepts
• Ssl_finished_connects
• Ssl_session_cache_hits
• Ssl_session_cache_misses
• Ssl_session_cache_overflows
• Ssl_session_cache_size
• Ssl_session_cache_timeouts
• Ssl_sessions_reused
• Ssl_used_session_cache_entries
• Subquery_cache_hit
• Subquery_cache_miss
• Table_locks_immediate
• Table_locks_waited
• Tc_log_max_pages_used
• Tc_log_page_waits
• Transactions_gtid_foreign_engine
• Transactions_multi_engine

FLUSH SSL

In MariaDB 10.4 and later, the FLUSH SSL command can be used to dynamically reinitialize the server's TLS context. This is most useful if you need to replace a certificate that is about to expire without restarting the server.

This operation is performed by reloading the files defined by the following TLS system variables:

• ssl_cert
• ssl_key
• ssl_ca
• ssl_capath
• ssl_crl
• ssl_crlpath

These TLS system variables are not dynamic, so their values can not be changed without restarting the server.

If you want to dynamically reinitialize the server's TLS context, then you need to change the certificate and key files at the relevant paths defined by these TLS system variables, without actually changing the values of the variables. See MDEV-19341 for more information.

Reducing Memory Usage

To flush some of the global caches that take up memory, you could execute the following command:

FLUSH LOCAL HOSTS,
   QUERY CACHE, 
   TABLE_STATISTICS, 
   INDEX_STATISTICS, 
   USER_STATISTICS;