mysqlcheck - a table maintenance program at Linux.org

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MYSQLCHECK(1) MySQL Database System MYSQLCHECK(1)

NAME
mysqlcheck - a table maintenance program

SYNOPSIS
mysqlcheck [options] [db_name [tbl_name ...]]

DESCRIPTION
The mysqlcheck client performs table maintenance: It checks, repairs, optimizes, or analyzes tables.

Each table is locked and therefore unavailable to other sessions while it is being processed, although for
check operations, the table is locked with a READ lock only (see Section 12.3.5, “LOCK TABLES and UNLOCK
TABLES Syntax”, for more information about READ and WRITE locks). Table maintenance operations can be
time-consuming, particularly for large tables. If you use the --databases or --all-databases option to process
all tables in one or more databases, an invocation of mysqlcheck might take a long time. (This is also true
for mysql_upgrade because that program invokes mysqlcheck to check all tables and repair them if necessary.)

mysqlcheck is similar in function to myisamchk, but works differently. The main operational difference is that
mysqlcheck must be used when the mysqld server is running, whereas myisamchk should be used when it is not.
The benefit of using mysqlcheck is that you do not have to stop the server to perform table maintenance.

mysqlcheck uses the SQL statements CHECK TABLE, REPAIR TABLE, ANALYZE TABLE, and OPTIMIZE TABLE in a
convenient way for the user. It determines which statements to use for the operation you want to perform, and
then sends the statements to the server to be executed. For details about which storage engines each statement
works with, see the descriptions for those statements in Section 12.4.2, “Table Maintenance Statements”.

The MyISAM storage engine supports all four maintenance operations, so mysqlcheck can be used to perform any
of them on MyISAM tables. Other storage engines do not necessarily support all operations. In such cases, an
error message is displayed. For example, if test.t is a MEMORY table, an attempt to check it produces this
result:

shell> mysqlcheck test t
test.t
note : The storage engine for the table doesn´t support check

If mysqlcheck is unable to repair a table, see Section 2.4.4, “Rebuilding or Repairing Tables or Indexes” for
manual table repair strategies. This will be the case, for example, for InnoDB tables, which can be checked
with CHECK TABLE, but not repaired with REPAIR TABLE.

The use of mysqlcheck with partitioned tables is not supported before MySQL 5.1.27.

Caution
It is best to make a backup of a table before performing a table repair operation; under some
circumstances the operation might cause data loss. Possible causes include but are not limited to file
system errors.

There are three general ways to invoke mysqlcheck:

shell> mysqlcheck [options] db_name [tbl_name ...]
shell> mysqlcheck [options] --databases db_name ...
shell> mysqlcheck [options] --all-databases

If you do not name any tables following db_name or if you use the --databases or --all-databases option,
entire databases are checked.

mysqlcheck has a special feature compared to other client programs. The default behavior of checking tables
(--check) can be changed by renaming the binary. If you want to have a tool that repairs tables by default,

mysqlcheck supports the following options, which can be specified on the command line or in the [mysqlcheck]
and [client] option file groups. mysqlcheck also supports the options for processing option files described
at Section 4.2.3.3.1, “Command-Line Options that Affect Option-File Handling”.

· --help, -?

Display a help message and exit.

· --all-databases, -A

Check all tables in all databases. This is the same as using the --databases option and naming all the
databases on the command line.

· --all-in-1, -1

Instead of issuing a statement for each table, execute a single statement for each database that names all
the tables from that database to be processed.

· --analyze, -a

Analyze the tables.

· --auto-repair

If a checked table is corrupted, automatically fix it. Any necessary repairs are done after all tables
have been checked.

· --character-sets-dir=path

The directory where character sets are installed. See Section 9.5, “Character Set Configuration”.

· --check, -c

Check the tables for errors. This is the default operation.

· --check-only-changed, -C

Check only tables that have changed since the last check or that have not been closed properly.

· --check-upgrade, -g

Invoke CHECK TABLE with the FOR UPGRADE option to check tables for incompatibilities with the current
version of the server. This option automatically enables the --fix-db-names and --fix-table-names options.
--check-upgrade was added in MySQL 5.1.7.

· --compress

Compress all information sent between the client and the server if both support compression.

· --databases, -B

Process all tables in the named databases. Normally, mysqlcheck treats the first name argument on the
command line as a database name and following names as table names. With this option, it treats all name
Print debugging information and memory and CPU usage statistics when the program exits. This option was
added in MySQL 5.1.14.

· --default-character-set=charset_name

Use charset_name as the default character set. See Section 9.5, “Character Set Configuration”.

· --defaults-extra-file=filename

Set filename as the file to read default options from after the global defaults files has been read. Must
be given as first option.

· --defaults-file=filename

Set filename as the file to read default options from, override global defaults files. Must be given as
first option.

· --extended, -e

If you are using this option to check tables, it ensures that they are 100% consistent but takes a long
time.

If you are using this option to repair tables, it runs an extended repair that may not only take a long
time to execute, but may produce a lot of garbage rows also!

· --fast, -F

Check only tables that have not been closed properly.

· --fix-db-names

Convert database names to 5.1 format. Only database names that contain special characters are affected.
This option was added in MySQL 5.1.7.

· --fix-table-names

Convert table names to 5.1 format. Only table names that contain special characters are affected. This
option was added in MySQL 5.1.7. As of MySQL 5.1.23, this option also applies to views.

· --force, -f

Continue even if an SQL error occurs.

· --host=host_name, -h host_name

Connect to the MySQL server on the given host.

· --medium-check, -m

Do a check that is faster than an --extended operation. This finds only 99.99% of all errors, which should
be good enough in most cases.

· --no-defaults

Specifying a password on the command line should be considered insecure. See Section 5.3.2.2, “End-User
Guidelines for Password Security”. You can use an option file to avoid giving the password on the command
line.

· --pipe, -W

On Windows, connect to the server via a named pipe. This option applies only if the server supports
named-pipe connections.

· --port=port_num, -P port_num

The TCP/IP port number to use for the connection.

· --protocol={TCP|SOCKET|PIPE|MEMORY}

The connection protocol to use for connecting to the server. It is useful when the other connection
parameters normally would cause a protocol to be used other than the one you want. For details on the
allowable values, see Section 4.2.2, “Connecting to the MySQL Server”.

· --print-defaults

Print the program argument list and exit. This must be given as the first argument.

· --quick, -q

If you are using this option to check tables, it prevents the check from scanning the rows to check for
incorrect links. This is the fastest check method.

If you are using this option to repair tables, it tries to repair only the index tree. This is the fastest
repair method.

· --repair, -r

Perform a repair that can fix almost anything except unique keys that are not unique.

· --silent, -s

Silent mode. Print only error messages.

· --socket=path, -S path

For connections to localhost, the Unix socket file to use, or, on Windows, the name of the named pipe to
use.

· --ssl*

Options that begin with --ssl specify whether to connect to the server via SSL and indicate where to find
SSL keys and certificates. See Section 5.5.6.3, “SSL Command Options”.

· --tables

Override the --databases or -B option. All name arguments following the option are regarded as table
names.

· --version, -V

Display version information and exit.

· --write-binlog

This option is enabled by default, so that ANALYZE TABLE, OPTIMIZE TABLE, and REPAIR TABLE statements
generated by mysqlcheck are written to the binary log. Use --skip-write-binlog to cause NO_WRITE_TO_BINLOG
to be added to the statements so that they are not logged. Use the --skip-write-binlog when these
statements should not be sent to replication slaves or run when using the binary logs for recovery from
backup. This option was added in MySQL 5.1.18.

This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU
General Public License as published by the Free Software Foundation; version 2 of the License.

This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
License for more details.

You should have received a copy of the GNU General Public License along with the program; if not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see
http://www.gnu.org/licenses/.

SEE ALSO
For more information, please refer to the MySQL Reference Manual, which may already be installed locally and
which is also available online at http://dev.mysql.com/doc/.

AUTHOR
Sun Microsystems, Inc. (http://www.mysql.com/).

MySQL 5.1 04/06/2010 MYSQLCHECK(1)