4.5.3. mysqlcheck — A Table Maintenance Program

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 ttest.tnote     : 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".

Table 4.6. mysqlcheck Options

Format	Option File	Description	Introduced
--all-databases	all-databases	Check all tables in all databases
--all-in-1	all-in-1	Execute a single statement for each database that names all the tables from that database
--analyze	analyze	Analyze the tables
--auto-repair	auto-repair	If a checked table is corrupted, automatically fix it
--bind-address=ip_address	bind-address	Use the specified network interface to connect to the MySQL Server
--character-sets-dir=path	character-sets-dir	The directory where character sets are installed
--check	check	Check the tables for errors
--check-only-changed	check-only-changed	Check only tables that have changed since the last check
--check-upgrade	check-upgrade	Invoke CHECK TABLE with the FOR UPGRADE option
--compress	compress	Compress all information sent between the client and the server
--databases	databases	Process all tables in the named databases
--debug[=debug_options]	debug	Write a debugging log
--debug-check	debug-check	Print debugging information when the program exits
--debug-info	debug-info	Print debugging information, memory and CPU statistics when the program exits
--default-auth=plugin	default-auth=plugin	The authentication plugin to use	5.6.2
--default-character-set=charset_name	default-character-set	Use charset_name as the default character set
--extended	extended	Check and repair tables
--fast	fast	Check only tables that have not been closed properly
--fix-db-names	fix-db-names	Convert database names to 5.1 format
--fix-table-names	fix-table-names	Convert table names to 5.1 format
--force	force	Continue even if an SQL error occurs
--help		Display help message and exit
--host=host_name	host	Connect to the MySQL server on the given host
--login-path=name		Read login path options from .mylogin.cnf	5.6.6
--medium-check	medium-check	Do a check that is faster than an --extended operation
--optimize	optimize	Optimize the tables
--password[=password]	password	The password to use when connecting to the server
--pipe		On Windows, connect to server using a named pipe
--plugin-dir=path	plugin-dir=path	The directory where plugins are located	5.6.2
--port=port_num	port	The TCP/IP port number to use for the connection
--protocol=type	protocol	The connection protocol to use
--quick	quick	The fastest method of checking
--repair	repair	Perform a repair that can fix almost anything except unique keys that are not unique
--silent	silent	Silent mode
--skip-database=db_name	skip-database	Omit this database from performed operations	5.6.11
--socket=path	socket	For connections to localhost
--ssl-ca=file_name	ssl-ca	The path to a file that contains a list of trusted SSL CAs
--ssl-capath=dir_name	ssl-capath	The path to a directory that contains trusted SSL CA certificates in PEM format
--ssl-cert=file_name	ssl-cert	The name of the SSL certificate file to use for establishing a secure connection
--ssl-cipher=cipher_list	ssl-cipher	A list of allowable ciphers to use for SSL encryption
--ssl-crl=file_name	ssl-crl	The path to a file that contains certificate revocation lists	5.6.3
--ssl-crlpath=dir_name	ssl-crlpath	The path to a directory that contains certificate revocation list files	5.6.3
--ssl-key=file_name	ssl-key	The name of the SSL key file to use for establishing a secure connection
--ssl-verify-server-cert	ssl-verify-server-cert	The server's Common Name value in its certificate is verified against the host name used when connecting to the server
--tables	tables	Overrides the --databases or -B option
--use-frm	use-frm	For repair operations on MyISAM tables
--user=user_name,	user	MySQL user name to use when connecting to server
--verbose		Verbose mode
--version		Display version information and exit
--write-binlog	write-binlog	Log ANALYZE, OPTIMIZE, REPAIR statements to binary log. --skip-write-binlog adds NO_WRITE_TO_BINLOG to these statements.

--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 beginning with MySQL 5.6.1.
--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 6.3.7, "Pluggable Authentication".

This option was added in MySQL 5.6.2.
--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 6.3.7, "Pluggable Authentication".

This option was added in MySQL 5.6.2.
--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.
--skip-database=db_name

Do not include the named database (case sensitive) in the operations performed by mysqlcheck. This option was added in MySQL 5.6.11.
--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.