Langue: en

Version: 2008-12-29 (fedora - 04/07/09)

Section: 1 (Commandes utilisateur)


mk-find - Find MySQL tables and execute actions, like GNU find.


mk-find looks for MySQL tables that pass the tests you specify, and executes the actions you specify. The default action is to print the database and table name to STDOUT.

mk-find is simpler than GNU find. It doesn't allow you to specify complicated expressions on the command line.

mk-find only looks for and processes tables. If you need it to do other things, like triggers or columns, file a bug report and I'll add the features.

mk-find uses SHOW TABLES when possible, and SHOW TABLE STATUS when needed.


You can download Maatkit from Google Code at <>, or you can get any of the tools easily with a command like the following:

Where "toolname" can be replaced with the name (or fragment of a name) of any of the Maatkit tools. Once downloaded, they're ready to run; no installation is needed. The first URL gets the latest released version of the tool, and the second gets the latest trunk code from Subversion.


There are three kinds of options: normal options, which determine some behavior or setting; tests, which determine whether a table should be included in the list of tables found; and actions, which do something to the tables mk-find finds.

mk-find uses standard Getopt::Long option parsing, so you should use double dashes in front of long option names, unlike GNU find.


Prompt for a password when connecting to MySQL.
Specifies that all regular expression searches are case-insensitive.
Enables character set settings in Perl and MySQL. If the value is "utf8", sets Perl's binmode on STDOUT to utf8, passes the "mysql_enable_utf8" option to DBD::mysql, and runs "SET NAMES UTF8" after connecting to MySQL. Any other value sets binmode on STDOUT without the utf8 layer, and runs "SET NAMES" after connecting to MySQL.
Measure times (for ``--mmin'', etc) from the beginning of today rather than from the current time.
If you specify this option, only this file is read for MySQL default options; otherwise all the default files will be read.
Displays a help message.
Connect to host.
By default, tests are evaluated as though there were an AND between them. This option switches it to OR.

Option parsing is not implemented by mk-find itself, so you cannot specify complicated expressions with parentheses and mixtures of OR and AND.

The password to use when connecting.
The port number to use for the connection.
This option is enabled by default. It quotes MySQL identifier names with MySQL's standard backtick character. Quoting happens after tests are run, and before actions are run.
Specify any variables you want to be set immediately after connecting to MySQL. These will be included in a "SET" command.
The socket file to use for the connection.
The user for login if not the current user.
Output version information and exit.


Most tests check some criterion against a column of SHOW TABLE STATUS output. Numeric arguments can be specified as +n for greater than n, -n for less than n, and n for exactly n. All numeric options can take an optional suffix multiplier of k, M or G (1_024, 1_048_576, and 1_073_741_824 respectively). All patterns are Perl regular expressions (see 'man perlre') unless specified as SQL LIKE patterns.

Dates and times are all measured relative to the same instant, when mk-find first asks the database server what time it is. All date and time manipulation is done in SQL, so if you say to find tables modified 5 days ago, that translates to SELECT DATE_SUB(CURRENT_TIMESTAMP, INTERVAL 5 DAY). If you specify ``--daystart'', if course it's relative to CURRENT_DATE instead.

However, table sizes and other metrics are not consistent at an instant in time. It can take some time for MySQL to process all the SHOW queries, and mk-find can't do anything about that. These measurements are as of the time they're taken.

If you need some test that's not in this list, file a bug report and I'll enhance mk-find for you. It's really easy.

Table's next AUTO_INCREMENT is n. This tests the Auto_increment column.
Table avg row len is n bytes. This tests the Avg_row_length column.
Table checksum is n. This tests the Checksum column.
Table was created n minutes ago. This tests the Create_time column.
Table collation matches pattern. This tests the Collation column.
Table comment matches pattern. This tests the Comment column.
Table create option matches pattern. This tests the Create_options column.
Table was created n days ago. This tests the Create_time column.
Table data uses n bytes of space. This tests the Data_length column.
Table has n bytes of free space. This tests the Data_free column.
Database name matches SQL LIKE pattern.
Database name matches this pattern.
Table has no rows. This tests the Rows column.
Table storage engine matches this pattern. This tests the Engine column, or in earlier versions of MySQL, the Type column.
Table indexes use n bytes of space. This tests the Index_length column.
Table was checked n minutes ago. This tests the Check_time column.
Table was checked n days ago. This tests the Check_time column.
Table was last modified n minutes ago. This tests the Update_time column.
Table was last modified n days ago. This tests the Update_time column.
Table name has nonexistent MySQL connection ID. This tests the table name for a pattern. The argument to this test must be a Perl regular expression that captures digits like this: (\d+). If the table name matches the pattern, these captured digits are taken to be the MySQL connection ID of some process. If the connection doesn't exist according to SHOW FULL PROCESSLIST, the test returns true. If the connection ID is greater than mk-find's own connection ID, the test returns false for safety.

Why would you want to do this? If you use MySQL statement-based replication, you probably know the trouble temporary tables can cause. You might choose to work around this by creating real tables with unique names, instead of temporary tables. One way to do this is to append your connection ID to the end of the table, thusly: scratch_table_12345. This assures the table name is unique and lets you have a way to find which connection it was associated with. And perhaps most importantly, if the connection no longer exists, you can assume the connection died without cleaning up its tables, and this table is a candidate for removal.

This how I manage scratch tables, and that's why I included this test in mk-find.

The argument I use to ``--pid'' is ``\D_(\d+)$''. That finds tables with a series of numbers at the end, preceded by an underscore and some non-number character (the latter criterion prevents me from examining tables with a date at the end, which people tend to do: baron_scratch_2007_05_07 for example). It's better to keep the scratch tables separate of course.

If you do this, make sure the user mk-find runs as has the PROCESS privilege! Otherwise it will only see connections from the same user, and might think some tables are ready to remove when they're still in use. For safety, mk-find checks this for you.

See also ``--sid''.

Table has n rows. This tests the Rows column.
Table row format matches pattern. This tests the Row_format column.
Table name contains the server ID. If you create temporary tables with the naming convention explained in ``--pid'', but also add the server ID of the server on which the tables are created, then you can use this pattern match to ensure tables are dropped only on the server they're created on. This prevents a table from being accidentally dropped on a slave while it's in use (provided that your server IDs are all unique, which they should be for replication to work).

For example, on the master (server ID 22) you create a table called scratch_table_22_12345. If you see this table on the slave (server ID 23), you might think it can be dropped safely if there's no such connection 12345. But if you also force the name to match the server ID with "--sid '\D_(\d+)_\d+$'", the table won't be dropped on the slave.

Table uses n bytes of space. This tests the sum of the Data_length and Index_length columns.
Table name matches SQL LIKE pattern.
Table name matches this pattern.
Table version is n. This tests the Version column.


The exec_plus action happens after everything else, but otherwise actions happen in an indeterminate order. If you need determinism, file a bug report and I'll add this feature.

Execute this SQL with each item found. The SQL can contain escapes and formatting directives (see ``--printf'').
Specify a DSN in key-value format to use when executing SQL with ``--exec'' and ``--exec_plus''. Any values not specified are inherited from command-line arguments.
Execute this SQL with all items at once. This option is unlike ``--exec''. There are no escaping or formatting directives; there is only one special placeholder for the list of database and table names, %s. The list of tables found will be joined together with commas and substituted wherever you place %s.

You might use this, for example, to drop all the tables you found:


This is sort of like GNU find's ``-exec command {} +'' syntax. Only it's not totally cryptic. And it doesn't require me to write a command-line parser.

Print the database and table name, followed by a newline. This is the default action if no other action is specified.
Print format on the standard output, interpreting '\' escapes and '%' directives. Escapes are backslashed characters, like \n and \t. Perl interprets these, so you can use any escapes Perl knows about. Directives are replaced by %s, and as of this writing, you can't add any special formatting instructions, like field widths or alignment (though I'm musing over ways to do that).

Here is a list of the directives. Note that most of them simply come from columns of SHOW TABLE STATUS. If the column is NULL or doesn't exist, you get an empty string in the output. A % character followed by any character not in the following list is discarded (but the other character is printed).

    ---- ------------------ ------------------------------------------
    a    Auto_increment
    A    Avg_row_length
    c    Checksum
    C    Create_time
    D    Database           The database name in which the table lives
    d    Data_length
    E    Engine             In older versions of MySQL, this is Type
    F    Data_free
    f    Innodb_free        Parsed from the Comment field
    I    Index_length
    K    Check_time
    L    Collation
    M    Max_data_length
    N    Name
    O    Comment
    P    Create_options
    R    Row_format
    S    Rows
    T    Table_length       Data_length+Index_length
    U    Update_time
    V    Version


Find all tables created more than a day ago, which use the MyISAM engine, and print their names:
   mk-find --ctime +1 --engine MyISAM

Find InnoDB tables that haven't been updated in a month, and convert them to MyISAM storage engine (data warehousing, anyone?):

   mk-find --mtime +30 --engine InnoDB --exec "ALTER TABLE %D.%N ENGINE=MyISAM"

Find tables created by a process that no longer exists, following the name_sid_pid naming convention, and remove them.

   mk-find --pid '\D_\d+_(\d+)$' --sid '\D_(\d+)_\d+$' --exec_plus "DROP TABLE %s"

Find empty tables in the test and junk databases, and delete them:

   mk-find --empty junk test --exec_plus "DROP TABLE %s"

Find tables more than five gigabytes in total size:

   mk-find --tablesize +5G

Find all tables and print their total data and index size, and sort largest tables first (sort is a different program, by the way).

   mk-find --printf "%T\t%D.%N\n" | sort -rn

As above, but this time, insert the data back into the database for posterity:

   mk-find --noquote --exec "INSERT INTO sysdata.tblsize(db, tbl, size) VALUES('%D', '%N', %T)"


The environment variable "MKDEBUG" enables verbose debugging output in all of the Maatkit tools:
    MKDEBUG=1 mk-....


Please use Google Code Issues and Groups to report bugs or request support: <>.

Please include the complete command-line used to reproduce the problem you are seeing, the version of all MySQL servers involved, the complete output of the tool when run with ``--version'', and if possible, debugging output produced by running with the "MKDEBUG=1" environment variable.


You need the following Perl modules: DBI and DBD::mysql.


This program is copyright 2007-2008 Baron Schwartz. Feedback and improvements are welcome (see ``BUGS'').


This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2; OR the Perl Artistic License. On UNIX and similar systems, you can issue `man perlgpl' or `man perlartistic' to read these licenses.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.


Baron Schwartz.


This manual page documents Ver 0.9.14 Distrib 2725 $Revision: 2311 $.