6.5.3 mysqlcheck — A Table Maintenance Program

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MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4

6.5.3 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 15.3.6, “LOCK TABLES and UNLOCK TABLES Statements”, 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 the MySQL upgrade procedure if it determines that table checking is needed because it processes tables the same way.)

mysqlcheck must be used when the mysqld server is running, which means 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 15.7.3, “Table Maintenance Statements”.

All storage engines do not necessarily support all four maintenance operations. In such cases, an error message is displayed. For example, if test.t is an MEMORY table, an attempt to check it produces this result:

$> 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 3.14, “Rebuilding or Repairing Tables or Indexes” for manual table repair strategies. This is 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:

mysqlcheck [options] db_name [tbl_name ...]
mysqlcheck [options] --databases db_name ...
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.

mysqlcheck supports the following options, which can be specified on the command line or in the [mysqlcheck] and [client] groups of an option file. For information about option files used by MySQL programs, see Section 6.2.2.2, “Using Option Files”.

Table 6.12 mysqlcheck Options

• --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, except that the INFORMATION_SCHEMA and performance_schema databases are not checked. They can be checked by explicitly naming them with the --databases option. - --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, use this option to select which interface to use for connecting to the MySQL server. - --character-sets-dir=dir_name

The directory where character sets are installed. See Section 12.15, “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. - --compress

Compress all information sent between the client and the server if possible. See Section 6.2.8, “Connection Compression Control”.

This option is deprecated. Expect it to be removed in a future version of MySQL. See Configuring Legacy Connection Compression. - --compression-algorithms=value

The permitted compression algorithms for connections to the server. The available algorithms are the same as for the protocol_compression_algorithms system variable. The default value is uncompressed.

For more information, see Section 6.2.8, “Connection Compression Control”. - --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 any 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.

This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option. - --debug-check

Print some debugging information when the program exits.

This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option. - --debug-info

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

This option is available only if MySQL was built using WITH_DEBUG. MySQL release binaries provided by Oracle are not built using this option. - --default-character-set=charset_name

Use charset_name as the default character set. See Section 12.15, “Character Set Configuration”. - --defaults-extra-file=file_name

Read this option file after the global option file but (on Unix) before the user option file. If the file does not exist or is otherwise inaccessible, an error occurs. If file_name is not an absolute path name, it is interpreted relative to the current directory.

For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”. - --defaults-file=file_name

Use only the given option file. If the file does not exist or is otherwise inaccessible, an error occurs. If file_name is not an absolute path name, it is interpreted relative to the current directory.

Exception: Even with --defaults-file, client programs read .mylogin.cnf.

For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”. - --defaults-group-suffix=str

Read not only the usual option groups, but also groups with the usual names and a suffix of str. For example, mysqlcheck normally reads the [client] and [mysqlcheck] groups. If this option is given as --defaults-group-suffix=_other, mysqlcheck also reads the [client_other] and [mysqlcheck_other] groups.

For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”. - --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

A hint about which client-side authentication plugin to use. See Section 8.2.17, “Pluggable Authentication”. - --enable-cleartext-plugin

Enable the mysql_clear_password cleartext authentication plugin. (See Section 8.4.1.4, “Client-Side Cleartext Pluggable Authentication”.) - --fast, -F

Check only tables that have not been closed properly. - --force, -f

Continue even if an SQL error occurs. - --get-server-public-key

Request from the server the public key required for RSA key pair-based password exchange. This option applies to clients that authenticate with the caching_sha2_password authentication plugin. For that plugin, the server does not send the public key unless requested. This option is ignored for accounts that do not authenticate with that plugin. It is also ignored if RSA-based password exchange is not used, as is the case when the client connects to the server using a secure connection.

If --server-public-key-path=file_name is given and specifies a valid public key file, it takes precedence over --get-server-public-key.

For information about the caching_sha2_password plugin, see Section 8.4.1.2, “Caching SHA-2 Pluggable Authentication”. - --host=host_name, -h host_name

Connect to the MySQL server on the given host. - --login-path=name

Read options from the named login path in the .mylogin.cnf login path file. A “login path” is an option group containing options that specify which MySQL server to connect to and which account to authenticate as. To create or modify a login path file, use the mysql_config_editor utility. See Section 6.6.7, “mysql_config_editor — MySQL Configuration Utility”.

For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”. - --no-login-paths

Skips reading options from the login path file.

See --login-path for related information.

For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”. - --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

Do not read any option files. If program startup fails due to reading unknown options from an option file, --no-defaults can be used to prevent them from being read.

The exception is that the .mylogin.cnf file is read in all cases, if it exists. This permits passwords to be specified in a safer way than on the command line even when --no-defaults is used. To create .mylogin.cnf, use the mysql_config_editor utility. See Section 6.6.7, “mysql_config_editor — MySQL Configuration Utility”.

For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”. - --optimize, -o

Optimize the tables. - --password[=password], -p[password]

The password of the MySQL account used for connecting to the server. The password value is optional. If not given, mysqlcheck prompts for one. If given, there must be no space between --password= or -p and the password following it. If no password option is specified, the default is to send no password.

Specifying a password on the command line should be considered insecure. To avoid giving the password on the command line, use an option file. See Section 8.1.2.1, “End-User Guidelines for Password Security”.

To explicitly specify that there is no password and that mysqlcheck should not prompt for one, use the --skip-password option. - --password1[=pass_val]

The password for multifactor authentication factor 1 of the MySQL account used for connecting to the server. The password value is optional. If not given, mysqlcheck prompts for one. If given, there must be no space between --password1= and the password following it. If no password option is specified, the default is to send no password.

Specifying a password on the command line should be considered insecure. To avoid giving the password on the command line, use an option file. See Section 8.1.2.1, “End-User Guidelines for Password Security”.

To explicitly specify that there is no password and that mysqlcheck should not prompt for one, use the --skip-password1 option.

--password1 and --password are synonymous, as are --skip-password1 and --skip-password. - --password2[=pass_val]

The password for multifactor authentication factor 2 of the MySQL account used for connecting to the server. The semantics of this option are similar to the semantics for --password1; see the description of that option for details. - --password3[=pass_val]

The password for multifactor authentication factor 3 of the MySQL account used for connecting to the server. The semantics of this option are similar to the semantics for --password1; see the description of that option for details. - --pipe, -W

On Windows, connect to the server using a named pipe. This option applies only if the server was started with the named_pipe system variable enabled to support named-pipe connections. In addition, the user making the connection must be a member of the Windows group specified by the named_pipe_full_access_group system variable. - --plugin-dir=dir_name

The directory in which to look for plugins. Specify this option if the --default-auth option is used to specify an authentication plugin but mysqlcheck does not find it. See Section 8.2.17, “Pluggable Authentication”. - --port=port_num, -P port_num

For TCP/IP connections, the port number to use. - --print-defaults

Print the program name and all options that it gets from option files.

For additional information about this and other option-file options, see Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”. - --protocol={TCP|SOCKET|PIPE|MEMORY}

The transport protocol to use for connecting to the server. It is useful when the other connection parameters normally result in use of a protocol other than the one you want. For details on the permissible values, see Section 6.2.7, “Connection Transport Protocols”. - --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. - --server-public-key-path=file_name

The path name to a file in PEM format containing a client-side copy of the public key required by the server for RSA key pair-based password exchange. This option applies to clients that authenticate with the sha256_password (deprecated) or caching_sha2_password authentication plugin. This option is ignored for accounts that do not authenticate with one of those plugins. It is also ignored if RSA-based password exchange is not used, as is the case when the client connects to the server using a secure connection.

If --server-public-key-path=file_name is given and specifies a valid public key file, it takes precedence over --get-server-public-key.

For sha256_password (deprecated), this option applies only if MySQL was built using OpenSSL.

For information about the sha256_password and caching_sha2_password plugins, see Section 8.4.1.3, “SHA-256 Pluggable Authentication”, and Section 8.4.1.2, “Caching SHA-2 Pluggable Authentication”. - --shared-memory-base-name=name

On Windows, the shared-memory name to use for connections made using shared memory to a local server. The default value i

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