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
--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
--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
--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 5.7.1
--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
--ssl-crlpath=dir_name ssl-crlpath The path to a directory that contains certificate revocation list files
--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.




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