mysqlcheck: A table maintenance program

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. 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.

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 the MariaDB Knowledge Base 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.

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 following names can be used to change mysqlcheck default behavior.

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] option file groups.

--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.

--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-auth=name

Default authentication client-side plugin to use.

--default-character-set=charset_name

Use charset_name as the default character set.

--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 will force using the old, slow, repair with keycache method, instead of the much faster repair by sorting.

--fast, -F

Check only tables that have not been closed properly.

--fix-db-names

Convert database names to the format used since MySQL 5.1. Only database names that contain special characters are affected.

--fix-table-names

Convert table names (including views) to the format used since MySQL 5.1. Only table names that contain special characters are affected.

--flush,

Flush each table after check. This is useful if you don't want to have the checked tables take up space in the caches after the check.

--force, -f

Continue even if an SQL error occurs.

--host=host_name, -h host_name

Connect to the MariaDB 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

Do not read default options from any option file. This must be given as the first argument.

--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. 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.

--plugin-dir=name

Directory for client-side plugins.

--port=port_num, -P port_num

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

--print-defaults

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

--process-tables

Perform the requested operation on tables. Defaults to on; use --skip-process-tables to disable.

--process-views=val

Perform the requested operation (only CHECK VIEW or REPAIR VIEW). Possible values are NO, YES (correct the checksum, if necessary, add the mariadb-version field), UPGRADE_FROM_MYSQL (same as YES and toggle the algorithm MERGE<->TEMPTABLE.

--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.

--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 -s

Don't process the database (case-sensitive) specified as argument.

--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

Enable SSL for connection (automatically enabled with other flags). Disable with --skip-ssl.

--ssl-ca=name

CA file in PEM format (check OpenSSL docs, implies --ssl).

--ssl-capath=name

CA directory (check OpenSSL docs, implies --ssl).

--ssl-cert=name

X509 cert in PEM format (check OpenSSL docs, implies --ssl).

--ssl-cipher=name

SSL cipher to use (check OpenSSL docs, implies --ssl).

--ssl-key=name

X509 key in PEM format (check OpenSSL docs, implies --ssl).

--ssl-crl=name

Certificate revocation list (check OpenSSL docs, implies --ssl).

--ssl-crlpath=name

Certificate revocation list path (check OpenSSL docs, implies --ssl).

--ssl-verify-server-cert

Verify server's "Common Name" in its cert against hostname used when connecting. This option is disabled by default.

--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 MariaDB user name to use when connecting to the server.

--verbose, -v

Verbose mode. Print information about the various stages of program operation. Using one --verbose option will give you more information about what mysqlcheck is doing.

Using two --verbose options will also give you connection information.

Using it 3 times will print out all CHECK, RENAME and ALTER TABLE during the check phase.

--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.

mysqlcheck (1)

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