mysqlcheck - Unix, Linux Command

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 12.3.5, \(lqLOCK TABLES and UNLOCK TABLES Syntax\(rq, 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 12.4.2, \(lqTable Maintenance Statements\(rq.


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
Section 2.13.4, \(lqRebuilding or Repairing Tables or Indexes\(rq
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 before MySQL 5.1.27.





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.




mysqlcheck
supports the following options, which can be specified on the command line or in the
[mysqlcheck]
and
[client]
option file groups.
mysqlcheck
also supports the options for processing option files described at
Section 4.2.3.3.1, \(lqCommand-Line Options that Affect Option-File Handling\(rq.



o





Display a help message and exit.



o





Check all tables in all databases. This is the same as using the
--databases
option and naming all the databases on the command line.



o





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.



o





Analyze the tables.



o





If a checked table is corrupted, automatically fix it. Any necessary repairs are done after all tables have been checked.



o





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 only in the version of
mysqlcheck
that is supplied with MySQL Cluster, beginning with MySQL Cluster NDB 6.3.4. It is not available in standard MySQL 5.1 releases.



o





The directory where character sets are installed. See
Section 9.5, \(lqCharacter Set Configuration\(rq.



o





Check the tables for errors. This is the default operation.



o





Check only tables that have changed since the last check or that have not been closed properly.



o





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.
--check-upgrade
was added in MySQL 5.1.7.



o





Compress all information sent between the client and the server if both support compression.



o





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.



o





Write a debugging log. A typical
debug_options
string is
'd:t:o,file_name'. The default is
'd:t:o'.



o





Print some debugging information when the program exits. This option was added in MySQL 5.1.21.



o





Print debugging information and memory and CPU usage statistics when the program exits. This option was added in MySQL 5.1.14.



o





Use
charset_name
as the default character set. See
Section 9.5, \(lqCharacter Set Configuration\(rq.



o





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!



o





Check only tables that have not been closed properly.



o





Convert database names to 5.1 format. Only database names that contain special characters are affected. This option was added in MySQL 5.1.7.



o





Convert table names to 5.1 format. Only table names that contain special characters are affected. This option was added in MySQL 5.1.7. As of MySQL 5.1.23, this option also applies to views.



o





Continue even if an SQL error occurs.



o





Connect to the MySQL server on the given host.



o





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.



o





Optimize the tables.



o





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 5.3.2.2, \(lqEnd-User Guidelines for Password Security\(rq. You can use an option file to avoid giving the password on the command line.



o





On Windows, connect to the server using a named pipe. This option applies only if the server supports named-pipe connections.



o





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



o





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, \(lqConnecting to the MySQL Server\(rq.



o





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.



o





Perform a repair that can fix almost anything except unique keys that are not unique.



o





Silent mode. Print only error messages.



o





For connections to
localhost, the Unix socket file to use, or, on Windows, the name of the named pipe to use.



o





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 5.5.6.3, \(lqSSL Command Options\(rq.



o





Override the
--databases
or
-B
option. All name arguments following the option are regarded as table names.



o





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.



o





The MySQL user name to use when connecting to the server.



o





Verbose mode. Print information about the various stages of program operation.



o





Display version information and exit.



o





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. This option was added in MySQL 5.1.18.


Copyright © 1997, 2011, Oracle and/or its affiliates. All rights reserved.


This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License.


This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.


You should have received a copy of the GNU General Public License along with the program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see http://www.gnu.org/licenses/.




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