FLUSH [LOCAL | NO_WRITE_TO_BINLOG] flush_option [, flush_option] ...
The FLUSH statement clears or reloads
various internal caches used by MySQL. To execute
FLUSH, you must have the
RELOAD privilege.
The RESET statement is similar to
FLUSH. See Section 13.5.5.5, “RESET Syntax”.
flush_option can be any of the
following:
-
HOSTS
Empties the host cache tables. You should flush the host
tables if some of your hosts change IP number or if you
get the error message Host
'host_name' is
blocked. When more than
max_connect_errors errors occur
successively for a given host while connecting to the
MySQL server, MySQL assumes that something is wrong and
blocks the host from further connection requests. Flushing
the host tables allows the host to attempt to connect
again. See Section A.2.5, “Host 'host_name' is blocked”. You can start
mysqld with
--max_connect_errors=999999999 to avoid
this error message.
-
DES_KEY_FILE
Reloads the DES keys from the file that was specified with
the --des-key-file option at server
startup time.
-
LOGS
Closes and reopens all log files. If binary logging is
enabled, the sequence number of the binary log file is
incremented by one relative to the previous file. On Unix,
this is the same thing as sending a
SIGHUP signal to the
mysqld server (except on some Mac OS X
10.3 versions where mysqld ignores
SIGHUP and SIGQUIT).
If the server was started with the
--log-error option, FLUSH
LOGS causes the error log is renamed with a
suffix of -old and
mysqld creates a new empty log file. No
renaming occurs if the --log-error option
was not given.
-
PRIVILEGES
Reloads the privileges from the grant tables in the
mysql database.
-
QUERY CACHE
Defragment the query cache to better utilize its memory.
FLUSH QUERY CACHE does not remove any
queries from the cache, unlike RESET QUERY
CACHE.
-
STATUS
Resets most status variables to zero. This is something
you should use only when debugging a query. See
Section 1.8, “How to Report Bugs or Problems”.
-
{TABLE | TABLES}
[tbl_name [,
tbl_name] ...]
When no tables are named, closes all open tables and
forces all tables in use to be closed. This also flushes
the query cache. With one or more table names, flushes
only the given tables. FLUSH TABLES
also removes all query results from the query cache, like
the RESET QUERY CACHE statement.
-
TABLES WITH READ LOCK
Closes all open tables and locks all tables for all
databases with a read lock until you execute
UNLOCK TABLES. This is very convenient
way to get backups if you have a filesystem such as
Veritas that can take snapshots in time.
-
USER_RESOURCES
Resets all per-hour user resources to zero. This enables
clients that have reached their hourly connection, query,
or update limits to resume activity immediately.
FLUSH USER_RESOURCES does not apply to
the limit on maximum simultaneous connections. See
Section 13.5.1.3, “GRANT Syntax”.
FLUSH statements are written to the binary
log unless the optional NO_WRITE_TO_BINLOG
keyword (or its alias LOCAL) is used. This
is done so that FLUSH statements used on a
MySQL server acting as a replication master will be replicated
by default to the replication slave.
Note: FLUSH
LOGS, FLUSH MASTER,
FLUSH SLAVE, and FLUSH TABLES WITH
READ LOCK are not logged in any case because they
would cause problems if replicated to a slave.
You can also access some of these statements with the
mysqladmin utility, using the
flush-hosts, flush-logs,
flush-privileges,
flush-status, or
flush-tables commands.
Note: It is not possible in
MySQL 5.1 to issue FLUSH
statements within stored functions or triggers. However, you
may use FLUSH in stored procedures, so long
as these are not called from stored functions or triggers. See
Section I.1, “Restrictions on Stored Routines and Triggers”.
See also Section 13.5.5.5, “RESET Syntax”, for information about how
the RESET statement is used with
replication.
