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
LOCK TABLES and
UNLOCK TABLES Syntax",
for more information about
Table maintenance operations can be time-consuming, particularly for large tables. If you use the
--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
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
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".
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:
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
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 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.
|mysqlrepair||The default option is
|mysqlanalyze||The default option is
|mysqloptimize||The default option is
mysqlcheck supports the following options, which can be
specified on the command line or in the
groups of an option file. mysqlcheck also supports the options for processing option
files described at Section 184.108.40.206,
"Command-Line Options that Affect Option-File Handling".
|--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|
|--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|
|--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.|
Display a help message and exit.
Check all tables in all databases. This is the same as using the
--databases option and naming all the databases on the command line.
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 the tables.
If a checked table is corrupted, automatically fix it. Any necessary repairs are done after all tables have been checked.
On a computer having multiple network interfaces, this option can be used to select which interface is employed when connecting to the MySQL server.
The directory where character sets are installed. See Section 10.5, "Character Set Configuration".
Check the tables for errors. This is the default operation.
Check only tables that have changed since the last check or that have not been closed properly.
CHECK TABLE with the
FOR UPGRADE option
to check tables for incompatibilities with the current version of the server. This option
automatically enables the
Compress all information sent between the client and the server if both support compression.
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.
Write a debugging log. A typical
debug_options string is
Print some debugging information when the program exits.
Print debugging information and memory and CPU usage statistics when the program exits.
charset_name as the default character set. See Section 10.5, "Character Set Configuration".
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!
The client-side authentication plugin to use. See Section 6.3.7, "Pluggable Authentication".
Check only tables that have not been closed properly.
Convert database names to 5.1 format. Only database names that contain special characters are affected.
Convert table names to 5.1 format. Only table names that contain special characters are affected. This option also applies to views.
Continue even if an SQL error occurs.
Connect to the MySQL server on the given host.
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 the tables.
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
-p option on the command
prompts for one.
Specifying a password on the command line should be considered insecure. See Section 220.127.116.11, "End-User Guidelines for Password Security". You can use an option file to avoid giving the password on the command line.
On Windows, connect to the server using a named pipe. This option applies only if the server supports named-pipe connections.
The directory in which to look for plugins. It may be necessary to specify this option if the
option is used to specify an authentication plugin but mysqlcheck does not find it. See Section
6.3.7, "Pluggable Authentication".
The TCP/IP port number to use for the connection.
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".
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.
Perform a repair that can fix almost anything except unique keys that are not unique.
Silent mode. Print only error messages.
Do not include the named database (case sensitive) in the operations performed by mysqlcheck.
For connections to
localhost, the Unix socket file to use, or, on
Windows, the name of the named pipe to use.
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
18.104.22.168, "SSL Command Options".
-B option. All name arguments following the option are regarded as
For repair operations on
MyISAM tables, get the table structure from
.frm file so that the table can be repaired even if the
.MYI header is corrupted.
The MySQL user name to use when connecting to the server.
Verbose mode. Print information about the various stages of program operation.
Display version information and exit.
This option is enabled by default, so that
OPTIMIZE TABLE, and
REPAIR TABLE statements generated by mysqlcheck are written to the binary log. Use
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.