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.\" ========================================================================
.\"
.IX Title "PT-DUPLICATE-KEY-CHECKER 1p"
.TH PT-DUPLICATE-KEY-CHECKER 1p "2012-06-15" "perl v5.14.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
pt\-duplicate\-key\-checker \- Find duplicate indexes and foreign keys on MySQL tables.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
Usage: pt-duplicate-key-checker [\s-1OPTION\s0...] [\s-1DSN\s0]
.PP
pt-duplicate-key-checker examines MySQL tables for duplicate or redundant
indexes and foreign keys.  Connection options are read from MySQL option files.
.PP
.Vb 1
\&   pt\-duplicate\-key\-checker \-\-host host1
.Ve
.SH "RISKS"
.IX Header "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.
.PP
pt-duplicate-key-checker is a read-only tool that executes \s-1SHOW\s0 \s-1CREATE\s0 \s-1TABLE\s0 and
related queries to inspect table structures, and thus is very low-risk.
.PP
At the time of this release, there is an unconfirmed bug that causes the tool
to crash.
.PP
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 \s-1URL:\s0
http://www.percona.com/bugs/pt\-duplicate\-key\-checker <http://www.percona.com/bugs/pt-duplicate-key-checker>.
.PP
See also \*(L"\s-1BUGS\s0\*(R" for more information on filing bugs and getting help.
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This program examines the output of \s-1SHOW\s0 \s-1CREATE\s0 \s-1TABLE\s0 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
\&\s-1BTREE\s0 index is not a duplicate of a \s-1FULLTEXT\s0 index, even if they have the same
columns.  You can override this.
.PP
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.
.SH "OPTIONS"
.IX Header "OPTIONS"
This tool accepts additional command-line arguments.  Refer to the
\&\*(L"\s-1SYNOPSIS\s0\*(R" and usage information for details.
.IP "\-\-all\-structs" 4
.IX Item "--all-structs"
Compare indexes with different structs (\s-1BTREE\s0, \s-1HASH\s0, etc).
.Sp
By default this is disabled, because a \s-1BTREE\s0 index that covers the same columns
as a \s-1FULLTEXT\s0 index is not really a duplicate, for example.
.IP "\-\-ask\-pass" 4
.IX Item "--ask-pass"
Prompt for a password when connecting to MySQL.
.IP "\-\-charset" 4
.IX Item "--charset"
short form: \-A; type: string
.Sp
Default character set.  If the value is utf8, sets Perl's binmode on
\&\s-1STDOUT\s0 to utf8, passes the mysql_enable_utf8 option to DBD::mysql, and runs \s-1SET\s0
\&\s-1NAMES\s0 \s-1UTF8\s0 after connecting to MySQL.  Any other value sets binmode on \s-1STDOUT\s0
without the utf8 layer, and runs \s-1SET\s0 \s-1NAMES\s0 after connecting to MySQL.
.IP "\-\-[no]clustered" 4
.IX Item "--[no]clustered"
default: yes
.Sp
\&\s-1PK\s0 columns appended to secondary key is duplicate.
.Sp
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).
.Sp
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.
.Sp
Here's an example of a key that is considered redundant with this option:
.Sp
.Vb 2
\&  PRIMARY KEY  (\`a\`)
\&  KEY \`b\` (\`b\`,\`a\`)
.Ve
.Sp
The use of such indexes is rather subtle.  For example, suppose you have the
following query:
.Sp
.Vb 1
\&  SELECT ... WHERE b=1 ORDER BY a;
.Ve
.Sp
This query will do a filesort if we remove the index on \f(CW\*(C`b,a\*(C'\fR.  But if we
shorten the index on \f(CW\*(C`b,a\*(C'\fR to just \f(CW\*(C`b\*(C'\fR and also remove the \s-1ORDER\s0 \s-1BY\s0, the query
should return the same results.
.Sp
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.
.IP "\-\-config" 4
.IX Item "--config"
type: Array
.Sp
Read this comma-separated list of config files; if specified, this must be the
first option on the command line.
.IP "\-\-databases" 4
.IX Item "--databases"
short form: \-d; type: hash
.Sp
Check only this comma-separated list of databases.
.IP "\-\-defaults\-file" 4
.IX Item "--defaults-file"
short form: \-F; type: string
.Sp
Only read mysql options from the given file.  You must give an absolute pathname.
.IP "\-\-engines" 4
.IX Item "--engines"
short form: \-e; type: hash
.Sp
Check only tables whose storage engine is in this comma-separated list.
.IP "\-\-help" 4
.IX Item "--help"
Show help and exit.
.IP "\-\-host" 4
.IX Item "--host"
short form: \-h; type: string
.Sp
Connect to host.
.IP "\-\-ignore\-databases" 4
.IX Item "--ignore-databases"
type: Hash
.Sp
Ignore this comma-separated list of databases.
.IP "\-\-ignore\-engines" 4
.IX Item "--ignore-engines"
type: Hash
.Sp
Ignore this comma-separated list of storage engines.
.IP "\-\-ignore\-order" 4
.IX Item "--ignore-order"
Ignore index order so \s-1KEY\s0(a,b) duplicates \s-1KEY\s0(b,a).
.IP "\-\-ignore\-tables" 4
.IX Item "--ignore-tables"
type: Hash
.Sp
Ignore this comma-separated list of tables.  Table names may be qualified with
the database name.
.IP "\-\-key\-types" 4
.IX Item "--key-types"
type: string; default: fk
.Sp
Check for duplicate f=foreign keys, k=keys or fk=both.
.IP "\-\-password" 4
.IX Item "--password"
short form: \-p; type: string
.Sp
Password to use when connecting.
.IP "\-\-pid" 4
.IX Item "--pid"
type: string
.Sp
Create the given \s-1PID\s0 file.  The file contains the process \s-1ID\s0 of the script.
The \s-1PID\s0 file is removed when the script exits.  Before starting, the script
checks if the \s-1PID\s0 file already exists.  If it does not, then the script creates
and writes its own \s-1PID\s0 to it.  If it does, then the script checks the following:
if the file contains a \s-1PID\s0 and a process is running with that \s-1PID\s0, then
the script dies; or, if there is no process running with that \s-1PID\s0, then the
script overwrites the file with its own \s-1PID\s0 and starts; else, if the file
contains no \s-1PID\s0, then the script dies.
.IP "\-\-port" 4
.IX Item "--port"
short form: \-P; type: int
.Sp
Port number to use for connection.
.IP "\-\-set\-vars" 4
.IX Item "--set-vars"
type: string; default: wait_timeout=10000
.Sp
Set these MySQL variables.  Immediately after connecting to MySQL, this string
will be appended to \s-1SET\s0 and executed.
.IP "\-\-socket" 4
.IX Item "--socket"
short form: \-S; type: string
.Sp
Socket file to use for connection.
.IP "\-\-[no]sql" 4
.IX Item "--[no]sql"
default: yes
.Sp
Print \s-1DROP\s0 \s-1KEY\s0 statement for each duplicate key.  By default an \s-1ALTER\s0 \s-1TABLE\s0
\&\s-1DROP\s0 \s-1KEY\s0 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.
.Sp
To disable printing these statements, specify \f(CW\*(C`\-\-no\-sql\*(C'\fR.
.IP "\-\-[no]summary" 4
.IX Item "--[no]summary"
default: yes
.Sp
Print summary of indexes at end of output.
.IP "\-\-tables" 4
.IX Item "--tables"
short form: \-t; type: hash
.Sp
Check only this comma-separated list of tables.
.Sp
Table names may be qualified with the database name.
.IP "\-\-user" 4
.IX Item "--user"
short form: \-u; type: string
.Sp
User for login if not current user.
.IP "\-\-verbose" 4
.IX Item "--verbose"
short form: \-v
.Sp
Output all keys and/or foreign keys found, not just redundant ones.
.IP "\-\-version" 4
.IX Item "--version"
Show version and exit.
.SH "DSN OPTIONS"
.IX Header "DSN OPTIONS"
These \s-1DSN\s0 options are used to create a \s-1DSN\s0.  Each option is given like
\&\f(CW\*(C`option=value\*(C'\fR.  The options are case-sensitive, so P and p are not the
same option.  There cannot be whitespace before or after the \f(CW\*(C`=\*(C'\fR and
if the value contains whitespace it must be quoted.  \s-1DSN\s0 options are
comma-separated.  See the percona-toolkit manpage for full details.
.IP "\(bu" 4
A
.Sp
dsn: charset; copy: yes
.Sp
Default character set.
.IP "\(bu" 4
D
.Sp
dsn: database; copy: yes
.Sp
Default database.
.IP "\(bu" 4
F
.Sp
dsn: mysql_read_default_file; copy: yes
.Sp
Only read default options from the given file
.IP "\(bu" 4
h
.Sp
dsn: host; copy: yes
.Sp
Connect to host.
.IP "\(bu" 4
p
.Sp
dsn: password; copy: yes
.Sp
Password to use when connecting.
.IP "\(bu" 4
P
.Sp
dsn: port; copy: yes
.Sp
Port number to use for connection.
.IP "\(bu" 4
S
.Sp
dsn: mysql_socket; copy: yes
.Sp
Socket file to use for connection.
.IP "\(bu" 4
u
.Sp
dsn: user; copy: yes
.Sp
User for login if not current user.
.SH "ENVIRONMENT"
.IX Header "ENVIRONMENT"
The environment variable \f(CW\*(C`PTDEBUG\*(C'\fR enables verbose debugging output to \s-1STDERR\s0.
To enable debugging and capture all output to a file, run the tool like:
.PP
.Vb 1
\&   PTDEBUG=1 pt\-duplicate\-key\-checker ... > FILE 2>&1
.Ve
.PP
Be careful: debugging output is voluminous and can generate several megabytes
of output.
.SH "SYSTEM REQUIREMENTS"
.IX Header "SYSTEM REQUIREMENTS"
You need Perl, \s-1DBI\s0, DBD::mysql, and some core packages that ought to be
installed in any reasonably new version of Perl.
.SH "BUGS"
.IX Header "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>.
.PP
Please report bugs at https://bugs.launchpad.net/percona\-toolkit <https://bugs.launchpad.net/percona-toolkit>.
Include the following information in your bug report:
.IP "\(bu" 4
Complete command-line used to run the tool
.IP "\(bu" 4
Tool \*(L"\-\-version\*(R"
.IP "\(bu" 4
MySQL version of all servers involved
.IP "\(bu" 4
Output from the tool including \s-1STDERR\s0
.IP "\(bu" 4
Input files (log/dump/config files, etc.)
.PP
If possible, include debugging output by running the tool with \f(CW\*(C`PTDEBUG\*(C'\fR;
see \*(L"\s-1ENVIRONMENT\s0\*(R".
.SH "DOWNLOADING"
.IX Header "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:
.PP
.Vb 1
\&   wget percona.com/get/percona\-toolkit.tar.gz
\&
\&   wget percona.com/get/percona\-toolkit.rpm
\&
\&   wget percona.com/get/percona\-toolkit.deb
.Ve
.PP
You can also get individual tools from the latest release:
.PP
.Vb 1
\&   wget percona.com/get/TOOL
.Ve
.PP
Replace \f(CW\*(C`TOOL\*(C'\fR with the name of any tool.
.SH "AUTHORS"
.IX Header "AUTHORS"
Baron Schwartz and Daniel Nichter
.SH "ABOUT PERCONA TOOLKIT"
.IX Header "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.
.SH "COPYRIGHT, LICENSE, AND WARRANTY"
.IX Header "COPYRIGHT, LICENSE, AND WARRANTY"
This program is copyright 2007\-2011 Baron Schwartz, 2011\-2012 Percona Inc.
Feedback and improvements are welcome.
.PP
\&\s-1THIS\s0 \s-1PROGRAM\s0 \s-1IS\s0 \s-1PROVIDED\s0 \*(L"\s-1AS\s0 \s-1IS\s0\*(R" \s-1AND\s0 \s-1WITHOUT\s0 \s-1ANY\s0 \s-1EXPRESS\s0 \s-1OR\s0 \s-1IMPLIED\s0
\&\s-1WARRANTIES\s0, \s-1INCLUDING\s0, \s-1WITHOUT\s0 \s-1LIMITATION\s0, \s-1THE\s0 \s-1IMPLIED\s0 \s-1WARRANTIES\s0 \s-1OF\s0
\&\s-1MERCHANTABILITY\s0 \s-1AND\s0 \s-1FITNESS\s0 \s-1FOR\s0 A \s-1PARTICULAR\s0 \s-1PURPOSE\s0.
.PP
This program is free software; you can redistribute it and/or modify it under
the terms of the \s-1GNU\s0 General Public License as published by the Free Software
Foundation, version 2; \s-1OR\s0 the Perl Artistic License.  On \s-1UNIX\s0 and similar
systems, you can issue `man perlgpl' or `man perlartistic' to read these
licenses.
.PP
You should have received a copy of the \s-1GNU\s0 General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place, Suite 330, Boston, \s-1MA\s0  02111\-1307  \s-1USA\s0.
.SH "VERSION"
.IX Header "VERSION"
pt-duplicate-key-checker 2.1.2