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:
 
Option | Description | 
 
CHANGED_PAGE_BITMAPS | Internal command used for backup
purposes. See the Information Schema CHANGED_PAGE_BITMAPS
Table. | 
 
CLIENT_STATISTICS | Reset client statistics (see SHOW
CLIENT_STATISTICS). | 
 
DES_KEY_FILE | Reloads the DES key file (Specified with the
--des-key-file startup option). | 
 
HOSTS | Flush the hostname cache (used for converting ip to
host names and for unblocking blocked hosts. See
max_connect_errors) | 
 
INDEX_STATISTICS | Reset index statistics (see SHOW
INDEX_STATISTICS). | 
 
[ERROR | ENGINE | GENERAL | SLOW | BINARY | RELAY] LOGS |
Close and reopen the specified log type, or all log types if
none are specified. FLUSH RELAY LOGS [connection-name] can
be used to flush the relay logs for a specific connection.
Only one connection can be specified per FLUSH command. See
Multi-source replication. FLUSH ENGINE LOGS will delete all
unneeded Aria redo logs. Since MariaDB 10.1.30 and MariaDB
10.2.11, FLUSH BINARY LOGS
DELETE_DOMAIN_ID=(list-of-domains) can be used to discard
obsolete GTID domains from the server's binary log state.
In order for this to be successful, no event group from the
listed GTID domains can be present in existing binary log
files. If some still exist, then they must be purged prior
to executing this command. If the command completes
successfully, then it also rotates the binary log. | 
 
MASTER | Deprecated option, use RESET MASTER instead. | 
 
PRIVILEGES | Reload all privileges from the privilege tables
in the mysql database. If the server is started with
--skip-grant-table option, this will activate the privilege
tables again. | 
 
QUERY CACHE | Defragment the query cache to better utilize
its memory. If you want to reset the query cache, you can do
it with RESET QUERY CACHE. | 
 
QUERY_RESPONSE_TIME | See the QUERY_RESPONSE_TIME plugin. | 
 
SLAVE | Deprecated option, use RESET SLAVE instead. | 
 
SSL | Used to dynamically reinitialize the server's TLS
context by reloading the files defined by several TLS system
variables. See FLUSH SSL for more information. This command
was first added in MariaDB 10.4.1. | 
 
STATUS | Resets all server status variables that can be
reset to 0. Not all global status variables support this, so
not all global values are reset. See FLUSH STATUS for more
information. | 
 
TABLE | Close tables given as options or all open tables if
no table list was used. From MariaDB 10.4.1, using without
any table list will only close tables not in use, and tables
not locked by the FLUSH TABLES connection. If there are no
locked tables, FLUSH TABLES will be instant and will not
cause any waits, as it no longer waits for tables in use.
When a table list is provided, from MariaDB 10.4.1, the
server will wait for the end of any transactions that are
using the tables. Previously, FLUSH TABLES only waited for
the statements to complete. | 
 
TABLES | Same as FLUSH TABLE. | 
 
TABLES ... FOR EXPORT | For InnoDB tables, flushes table
changes to disk to permit binary table copies while the
server is running. Introduced in MariaDB 10.0.8. See FLUSH
TABLES ... FOR EXPORT for more. | 
 
TABLES WITH READ LOCK | Closes all open tables. New tables
are only allowed to be opened with read locks until an
 
TABLES WITH READ LOCK AND DISABLE CHECKPOINT | As TABLES
WITH READ LOCK but also disable all checkpoint writes by
transactional table engines. This is useful when doing a
disk snapshot of all tables. | 
 
TABLE_STATISTICS | Reset table statistics (see SHOW
TABLE_STATISTICS). | 
 
USER_RESOURCES | Resets all per hour user resources. This
enables clients that have exhausted their resources to
connect again. | 
 
USER_STATISTICS | Reset user statistics (see SHOW
USER_STATISTICS). | 
 
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
 
The FLUSH SSL command was first added in MariaDB 10.4.
 
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;
 

 
 
 
 
 
 
 
 

URL: https://mariadb.com/kb/en/flush/