Ubuntu Manpage: mysqlcheck - a table maintenance program

Provided by: percona-xtradb-cluster-client-5.5_5.5.37-25.10+dfsg-0ubuntu0.14.04.5_amd64

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 13.3.5, “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 13.7.2, “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 2.11.4, “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.

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, you should just make a copy of mysqlcheck named mysqlrepair, or make a symbolic link to
mysqlcheck named mysqlrepair. If you invoke mysqlrepair, it repairs tables.

The names shown in the following table can be used to change mysqlcheck default behavior.
┌───────────────┬──────────────────────────────────┐
│ Command │ Meaning │
├───────────────┼──────────────────────────────────┤
│ mysqlrepair │ The default option is --repair │
├───────────────┼──────────────────────────────────┤
│ mysqlanalyze │ The default option is --analyze │
├───────────────┼──────────────────────────────────┤
│ mysqloptimize │ The default option is --optimize │
└───────────────┴──────────────────────────────────┘

mysqlcheck supports the following options, which can be specified on the command line or in the
[mysqlcheck] and [client] groups of an option file. mysqlcheck also supports the options for processing
option files described at Section 4.2.3.4, “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.

• --bind-address=ip_address

On a computer having multiple network interfaces, this option can be used to select which interface
is employed when connecting to the MySQL server.

This option is supported only in the version of mysqlcheck that is supplied with MySQL Cluster. It is
not available in standard MySQL Server 5.5 releases.

• --character-sets-dir=path

The directory where character sets are installed. See Section 10.5, “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.

• --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 arguments as database names.

• --debug[=debug_options], -# [debug_options]

Write a debugging log. A typical debug_options string is d:t:o,file_name. The default is d:t:o.

• --debug-check

Print some debugging information when the program exits.

• --debug-info

Print debugging information and memory and CPU usage statistics when the program exits.

• --default-character-set=charset_name

Use charset_name as the default character set. See Section 10.5, “Character Set Configuration”.

• --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!

• --default-auth=plugin

The client-side authentication plugin to use. See Section 6.3.6, “Pluggable Authentication”.

This option was added in MySQL 5.5.10.

• --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.

• --fix-table-names

Convert table names to 5.1 format. Only table names that contain special characters are affected.
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.

• --optimize, -o

Optimize the tables.

• --password[=password], -p[password]

The password to use when connecting to the server. If you use the short option form (-p), you cannot
have a space between the option and the password. If you omit the password value following the
--password or -p option on the command line, mysqlcheck prompts for one.

Specifying a password on the command line should be considered insecure. See Section 6.1.2.1, “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 using a named pipe. This option applies only if the server supports
named-pipe connections.

• --plugin-dir=path

The directory in which to look for plugins. It may be necessary to specify this option if the
--default-auth option is used to specify an authentication plugin but mysqlcheck does not find it.
See Section 6.3.6, “Pluggable Authentication”.

This option was added in MySQL 5.5.10.

• --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
permissible values, see Section 4.2.2, “Connecting to the MySQL Server”.

• --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 using SSL and indicate where
to find SSL keys and certificates. See Section 6.3.9.4, “SSL Command Options”.

• --tables

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

• --use-frm

For repair operations on MyISAM tables, get the table structure from the .frm file so that the table
can be repaired even if the .MYI header is corrupted.

• --user=user_name, -u user_name

The MySQL user name to use when connecting to the server.

• --verbose, -v

Verbose mode. Print information about the various stages of program operation.

• --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.

COPYRIGHT

       Copyright © 1997, 2014, Oracle and/or its affiliates. All rights reserved.

       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/.

AUTHOR

       Oracle Corporation (http://dev.mysql.com/).

MySQL 5.5                                          03/14/2014                                      MYSQLCHECK(1)

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