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13.7.6.3 FLUSH Statement

FLUSH [NO_WRITE_TO_BINLOG | LOCAL] {
    flush_option [, flush_option] ...
  | tables_option
}

flush_option: {
    BINARY LOGS
  | DES_KEY_FILE
  | ENGINE LOGS
  | ERROR LOGS
  | GENERAL LOGS
  | HOSTS
  | LOGS
  | MASTER
  | PRIVILEGES
  | QUERY CACHE
  | RELAY LOGS
  | SLAVE
  | SLOW LOGS
  | STATUS
  | USER_RESOURCES
}

tables_option: {
    TABLES
  | TABLES tbl_name [, tbl_name] ...
  | TABLES WITH READ LOCK
  | TABLES tbl_name [, tbl_name] ... WITH READ LOCK
}

The FLUSH statement has several variant forms that clear or reload various internal caches, flush tables, or acquire locks. To execute FLUSH, you must have the RELOAD privilege. Specific flush options might require additional privileges, as described later.

Note

It is not possible 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 20.8, “Restrictions on Stored Programs”.

By default, the server writes FLUSH statements to the binary log so that they replicate to replication slaves. To suppress logging, specify the optional NO_WRITE_TO_BINLOG keyword or its alias LOCAL.

Note

FLUSH LOGS, FLUSH MASTER, FLUSH SLAVE, and FLUSH TABLES WITH READ LOCK (with or without a table list) are not written to the binary log in any case because they would cause problems if replicated to a slave.

The FLUSH statement causes an implicit commit. See Section 13.3.3, “Statements That Cause an Implicit Commit”.

The mysqladmin utility provides a command-line interface to some flush operations, using commands such as flush-hosts, flush-logs, flush-privileges, flush-status, and flush-tables. See Section 4.5.2, “mysqladmin — Client for Administering a MySQL Server”.

Sending a SIGHUP signal to the server causes several flush operations to occur that are similar to various forms of the FLUSH statement. Signals can be sent by root or the account that owns the server process. They enable the applicable flush operations to be performed without having to connect to the server (which for these operations requires an account that has the RELOAD privilege). See Section 4.10, “Unix Signal Handling in MySQL”.

The RESET statement is similar to FLUSH. See Section 13.7.6.6, “RESET Statement”, for information about using the RESET statement with replication.

The following list describes the permitted FLUSH statement flush_option values. For descriptions of FLUSH TABLES variants, see FLUSH TABLES Syntax.

FLUSH TABLES Syntax

FLUSH TABLES flushes tables, and, depending on the variant used, acquires locks. Any TABLES variant used in a FLUSH statement must be the only option used. FLUSH TABLE is a synonym for FLUSH TABLES.

Note

The descriptions here that indicate tables are flushed by closing them apply differently for InnoDB, which flushes table contents to disk but leaves them open. This still permits table files to be copied while the tables are open, as long as other activity does not modify them.