Provided by: percona-toolkit_3.1+dfsg-1.1_all bug

NAME

       pt-duplicate-key-checker - Find duplicate indexes and foreign keys on MySQL tables.

SYNOPSIS

       Usage: pt-duplicate-key-checker [OPTIONS] [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

       Percona Toolkit is mature, proven in the real world, and well tested, but all database
       tools can pose a risk to the system and the database server.  Before using this tool,
       please:

       •   Read the tool's documentation

       •   Review the tool's known "BUGS"

       •   Test the tool on a non-production server

       •   Backup your production server and verify the backups

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.

       The output ends with a short summary that includes an estimate of the total size, in
       bytes, that the duplicate indexes are using. This is calculated by multiplying the index
       length by the number of rows in their respective tables.

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.  If password contains commas they must be escaped
           with a backslash: "exam\,ple"

       --pid
           type: string

           Create the given PID file.  The tool won't start if the PID file already exists and
           the PID it contains is different than the current PID.  However, if the PID file
           exists and the PID it contains is no longer running, the tool will overwrite the PID
           file with the current PID.  The PID file is removed automatically when the tool exits.

       --port
           short form: -P; type: int

           Port number to use for connection.

       --set-vars
           type: Array

           Set the MySQL variables in this comma-separated list of "variable=value" pairs.

           By default, the tool sets:

              wait_timeout=10000

           Variables specified on the command line override these defaults.  For example,
           specifying "--set-vars wait_timeout=500" overrides the defaultvalue of 10000.

           The tool prints a warning and continues if a variable cannot be set.

       --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.

       --[no]version-check
           default: yes

           Check for the latest version of Percona Toolkit, MySQL, and other programs.

           This is a standard "check for updates automatically" feature, with two additional
           features.  First, the tool checks its own version and also the versions of the
           following software: operating system, Percona Monitoring and Management (PMM), MySQL,
           Perl, MySQL driver for Perl (DBD::mysql), and Percona Toolkit. Second, it checks for
           and warns about versions with known problems. For example, MySQL 5.5.25 had a critical
           bug and was re-released as 5.5.25a.

           A secure connection to Percona’s Version Check database server is done to perform
           these checks. Each request is logged by the server, including software version numbers
           and unique ID of the checked system. The ID is generated by the Percona Toolkit
           installation script or when the Version Check database call is done for the first
           time.

           Any updates or known problems are printed to STDOUT before the tool's normal output.
           This feature should never interfere with the normal operation of the tool.

           For more information, visit
           <https://www.percona.com/doc/percona-toolkit/LATEST/version-check.html>.

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.

       •   A

           dsn: charset; copy: yes

           Default character set.

       •   D

           dsn: database; copy: yes

           Default database.

       •   F

           dsn: mysql_read_default_file; copy: yes

           Only read default options from the given file

       •   h

           dsn: host; copy: yes

           Connect to host.

       •   p

           dsn: password; copy: yes

           Password to use when connecting.  If password contains commas they must be escaped
           with a backslash: "exam\,ple"

       •   P

           dsn: port; copy: yes

           Port number to use for connection.

       •   S

           dsn: mysql_socket; copy: yes

           Socket file to use for connection.

       •   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>.

       Please report bugs at <https://jira.percona.com/projects/PT>.  Include the following
       information in your bug report:

       •   Complete command-line used to run the tool

       •   Tool "--version"

       •   MySQL version of all servers involved

       •   Output from the tool including STDERR

       •   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/> 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 for
       MySQL developed by Percona.  Percona Toolkit was forked from two projects in June, 2011:
       Maatkit and Aspersa.  Those projects were created by Baron Schwartz and primarily
       developed by him and Daniel Nichter.  Visit <http://www.percona.com/software/> to learn
       about other free, open-source software from Percona.

COPYRIGHT, LICENSE, AND WARRANTY

       This program is copyright 2011-2018 Percona LLC and/or its affiliates, 2007-2011 Baron
       Schwartz.

       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 3.1.0

POD ERRORS

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