PT-DUPLICATE-KEY-CHECKER(1p) User Contributed Perl Documentation PT-DUPLICATE-KEY-CHECKER(1p)
NAME
pt-duplicate-key-checker - Find duplicate indexes and foreign keys on MySQL tables.
SYNOPSIS
Usage: pt-duplicate-key-checker [OPTION...] [DSN]
pt-duplicate-key-checker examines MySQL tables for duplicate or redundant indexes and foreign keys. Connection options are read from MySQL
option files.
pt-duplicate-key-checker --host host1
RISKS
The following section is included to inform users about the potential risks, whether known or unknown, of using this tool. The two main
categories of risks are those created by the nature of the tool (e.g. read-only tools vs. read-write tools) and those created by bugs.
pt-duplicate-key-checker is a read-only tool that executes SHOW CREATE TABLE and related queries to inspect table structures, and thus is
very low-risk.
At the time of this release, there is an unconfirmed bug that causes the tool to crash.
The authoritative source for updated information is always the online issue tracking system. Issues that affect this tool will be marked
as such. You can see a list of such issues at the following URL: http://www.percona.com/bugs/pt-duplicate-key-checker
<http://www.percona.com/bugs/pt-duplicate-key-checker>.
See also "BUGS" for more information on filing bugs and getting help.
DESCRIPTION
This program examines the output of SHOW CREATE TABLE on MySQL tables, and if it finds indexes that cover the same columns as another index
in the same order, or cover an exact leftmost prefix of another index, it prints out the suspicious indexes. By default, indexes must be
of the same type, so a BTREE index is not a duplicate of a FULLTEXT index, even if they have the same columns. You can override this.
It also looks for duplicate foreign keys. A duplicate foreign key covers the same columns as another in the same table, and references the
same parent table.
OPTIONS
This tool accepts additional command-line arguments. Refer to the "SYNOPSIS" and usage information for details.
--all-structs
Compare indexes with different structs (BTREE, HASH, etc).
By default this is disabled, because a BTREE index that covers the same columns as a FULLTEXT index is not really a duplicate, for
example.
--ask-pass
Prompt for a password when connecting to MySQL.
--charset
short form: -A; type: string
Default character set. 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.
--[no]clustered
default: yes
PK columns appended to secondary key is duplicate.
Detects when a suffix of a secondary key is a leftmost prefix of the primary key, and treats it as a duplicate key. Only detects this
condition on storage engines whose primary keys are clustered (currently InnoDB and solidDB).
Clustered storage engines append the primary key columns to the leaf nodes of all secondary keys anyway, so you might consider it
redundant to have them appear in the internal nodes as well. Of course, you may also want them in the internal nodes, because just
having them at the leaf nodes won't help for some queries. It does help for covering index queries, however.
Here's an example of a key that is considered redundant with this option:
PRIMARY KEY (`a`)
KEY `b` (`b`,`a`)
The use of such indexes is rather subtle. For example, suppose you have the following query:
SELECT ... WHERE b=1 ORDER BY a;
This query will do a filesort if we remove the index on "b,a". But if we shorten the index on "b,a" to just "b" and also remove the
ORDER BY, the query should return the same results.
The tool suggests shortening duplicate clustered keys by dropping the key and re-adding it without the primary key prefix. The
shortened clustered key may still duplicate another key, but the tool cannot currently detect when this happens without being ran a
second time to re-check the newly shortened clustered keys. Therefore, if you shorten any duplicate clustered keys, you should run the
tool again.
--config
type: Array
Read this comma-separated list of config files; if specified, this must be the first option on the command line.
--databases
short form: -d; type: hash
Check only this comma-separated list of databases.
--defaults-file
short form: -F; type: string
Only read mysql options from the given file. You must give an absolute pathname.
--engines
short form: -e; type: hash
Check only tables whose storage engine is in this comma-separated list.
--help
Show help and exit.
--host
short form: -h; type: string
Connect to host.
--ignore-databases
type: Hash
Ignore this comma-separated list of databases.
--ignore-engines
type: Hash
Ignore this comma-separated list of storage engines.
--ignore-order
Ignore index order so KEY(a,b) duplicates KEY(b,a).
--ignore-tables
type: Hash
Ignore this comma-separated list of tables. Table names may be qualified with the database name.
--key-types
type: string; default: fk
Check for duplicate f=foreign keys, k=keys or fk=both.
--password
short form: -p; type: string
Password to use when connecting.
--pid
type: string
Create the given PID file. The file contains the process ID of the script. The PID file is removed when the script exits. Before
starting, the script checks if the PID file already exists. If it does not, then the script creates and writes its own PID to it. If
it does, then the script checks the following: if the file contains a PID and a process is running with that PID, then the script dies;
or, if there is no process running with that PID, then the script overwrites the file with its own PID and starts; else, if the file
contains no PID, then the script dies.
--port
short form: -P; type: int
Port number to use for connection.
--set-vars
type: string; default: wait_timeout=10000
Set these MySQL variables. Immediately after connecting to MySQL, this string will be appended to SET and executed.
--socket
short form: -S; type: string
Socket file to use for connection.
--[no]sql
default: yes
Print DROP KEY statement for each duplicate key. By default an ALTER TABLE DROP KEY statement is printed below each duplicate key so
that, if you want to remove the duplicate key, you can copy-paste the statement into MySQL.
To disable printing these statements, specify "--no-sql".
--[no]summary
default: yes
Print summary of indexes at end of output.
--tables
short form: -t; type: hash
Check only this comma-separated list of tables.
Table names may be qualified with the database name.
--user
short form: -u; type: string
User for login if not current user.
--verbose
short form: -v
Output all keys and/or foreign keys found, not just redundant ones.
--version
Show version and exit.
DSN OPTIONS
These DSN options are used to create a DSN. Each option is given like "option=value". The options are case-sensitive, so P and p are not
the same option. There cannot be whitespace before or after the "=" and if the value contains whitespace it must be quoted. DSN options
are comma-separated. See the percona-toolkit manpage for full details.
o A
dsn: charset; copy: yes
Default character set.
o D
dsn: database; copy: yes
Default database.
o F
dsn: mysql_read_default_file; copy: yes
Only read default options from the given file
o h
dsn: host; copy: yes
Connect to host.
o p
dsn: password; copy: yes
Password to use when connecting.
o P
dsn: port; copy: yes
Port number to use for connection.
o S
dsn: mysql_socket; copy: yes
Socket file to use for connection.
o u
dsn: user; copy: yes
User for login if not current user.
ENVIRONMENT
The environment variable "PTDEBUG" enables verbose debugging output to STDERR. To enable debugging and capture all output to a file, run
the tool like:
PTDEBUG=1 pt-duplicate-key-checker ... > FILE 2>&1
Be careful: debugging output is voluminous and can generate several megabytes of output.
SYSTEM REQUIREMENTS
You need Perl, DBI, DBD::mysql, and some core packages that ought to be installed in any reasonably new version of Perl.
BUGS
For a list of known bugs, see http://www.percona.com/bugs/pt-duplicate-key-checker <http://www.percona.com/bugs/pt-duplicate-key-checker>.
Please report bugs at https://bugs.launchpad.net/percona-toolkit <https://bugs.launchpad.net/percona-toolkit>. Include the following
information in your bug report:
o Complete command-line used to run the tool
o Tool "--version"
o MySQL version of all servers involved
o Output from the tool including STDERR
o Input files (log/dump/config files, etc.)
If possible, include debugging output by running the tool with "PTDEBUG"; see "ENVIRONMENT".
DOWNLOADING
Visit http://www.percona.com/software/percona-toolkit/ <http://www.percona.com/software/percona-toolkit/> to download the latest release of
Percona Toolkit. Or, get the latest release from the command line:
wget percona.com/get/percona-toolkit.tar.gz
wget percona.com/get/percona-toolkit.rpm
wget percona.com/get/percona-toolkit.deb
You can also get individual tools from the latest release:
wget percona.com/get/TOOL
Replace "TOOL" with the name of any tool.
AUTHORS
Baron Schwartz and Daniel Nichter
ABOUT PERCONA TOOLKIT
This tool is part of Percona Toolkit, a collection of advanced command-line tools developed by Percona for MySQL support and consulting.
Percona Toolkit was forked from two projects in June, 2011: Maatkit and Aspersa. Those projects were created by Baron Schwartz and
developed primarily by him and Daniel Nichter, both of whom are employed by Percona. Visit <http://www.percona.com/software/> for more
software developed by Percona.
COPYRIGHT, LICENSE, AND WARRANTY
This program is copyright 2007-2011 Baron Schwartz, 2011-2012 Percona Inc. Feedback and improvements are welcome.
THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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.
VERSION
pt-duplicate-key-checker 2.1.2
perl v5.14.2 2012-06-15 PT-DUPLICATE-KEY-CHECKER(1p)