MySQL 冗余索引排查及优化

这里使用到 pt 工具 pt-duplicate-key-checker 。

pt 工具下载：https://www.percona.com/downloads/percona-toolkit/LATEST/

压缩包下载完成后，上传到服务器，解压即可，这里安装过程跳过，直接进入工具使用及冗余索引排查环节。

1.查看工具帮助说明：

[mysql@dbtestsitdb01 bin]$ ./pt-duplicate-key-checker --help
pt-duplicate-key-checker examines MySQL tables for duplicate or redundant
indexes and foreign keys.  Connection options are read from MySQL option files.
For more details, please use the --help option, or try 'perldoc
./pt-duplicate-key-checker' for complete documentation.

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

Options:

--all-structs         Compare indexes with different structs (BTREE, HASH,
                    etc)
--ask-pass            Prompt for a password when connecting to MySQL
--charset=s       -A  Default character set
--[no]clustered       PK columns appended to secondary key is duplicate (
                    default yes)
--config=A            Read this comma-separated list of config files; if
                    specified, this must be the first option on the command
                    line
--databases=h     -d  Check only this comma-separated list of databases
--defaults-file=s -F  Only read mysql options from the given file
--engines=h       -e  Check only tables whose storage engine is in this comma-
                    separated list
--help                Show help and exit
--host=s          -h  Connect to host
--ignore-databases=H  Ignore this comma-separated list of databases
--ignore-engines=H    Ignore this comma-separated list of storage engines
--ignore-order        Ignore index order so KEY(a,b) duplicates KEY(b,a)
--ignore-tables=H     Ignore this comma-separated list of tables
--key-types=s         Check for duplicate f=foreign keys, k=keys or fk=both (
                    default fk)
--password=s      -p  Password to use when connecting
--pid=s               Create the given PID file
--port=i          -P  Port number to use for connection
--set-vars=A          Set the MySQL variables in this comma-separated list of
                    variable=value pairs
--socket=s        -S  Socket file to use for connection
--[no]sql             Print DROP KEY statement for each duplicate key (
                    default yes)
--[no]summary         Print summary of indexes at end of output (default yes)
--tables=h        -t  Check only this comma-separated list of tables
--user=s          -u  User for login if not current user
--verbose         -v  Output all keys and/or foreign keys found, not just
                    redundant ones
--version             Show version and exit
--[no]version-check   Check for the latest version of Percona Toolkit, MySQL,
                    and other programs (default yes)

Option types: s=string, i=integer, f=float, h/H/a/A=comma-separated list, d=DSN, z=size, m=time

Rules:

This tool accepts additional command-line arguments. Refer to the SYNOPSIS and usage information for details.

DSN syntax is key=value[,key=value...]  Allowable DSN keys:

KEY  COPY  MEANING
===  ====  =============================================
A    yes   Default character set
D    yes   Default database
F    yes   Only read default options from the given file
P    yes   Port number to use for connection
S    yes   Socket file to use for connection
h    yes   Connect to host
p    yes   Password to use when connecting
u    yes   User for login if not current user

If the DSN is a bareword, the word is treated as the 'h' key.

Options and values after processing arguments:

--all-structs         FALSE
--ask-pass            FALSE
--charset             (No value)
--clustered           TRUE
--config              /etc/percona-toolkit/percona-toolkit.conf,/etc/percona-toolkit/pt-duplicate-key-checker.conf,/home/mysql/.percona-toolkit.conf,/home/mysql/.pt-duplicate-key-checker.conf
--databases           (No value)
--defaults-file       (No value)
--engines             (No value)
--help                TRUE
--host                (No value)
--ignore-databases    
--ignore-engines      
--ignore-order        FALSE
--ignore-tables       
--key-types           fk
--password            (No value)
--pid                 (No value)
--port                (No value)
--set-vars            
--socket              (No value)
--sql                 TRUE
--summary             TRUE
--tables              (No value)
--user                (No value)
--verbose             FALSE
--version             FALSE
--version-check       TRUE

2.查看冗余索引

[mysql@dbtestsitdb01 bin]$ ./pt-duplicate-key-checker -uroot -p‘123456’ -h127.1 --socket=/mysql/data/mysql.sock -d dbtest01
# ########################################################################
# dbtest01.t3                                                             
# ########################################################################

# idx_xx is a left-prefix of idx_uniq
# Key definitions:
#   KEY `idx_xx` (`xxx`) USING BTREE,
#   UNIQUE KEY `idx_uniq` (`xxx`,`yyy`,`zzz`),
# Column types:
#	  `xxx` varchar(20) not null
#	  `yyy` varchar(20) not null
#	  `zzz` varchar(20) not null
# To remove this duplicate index, execute:
ALTER TABLE `dbtest01`.`t3` DROP INDEX `idx_xx`;

# ########################################################################
# dbtest01.ttt                                                            
# ########################################################################

# name is a left-prefix of xxx
# Key definitions:
#   KEY `name` (`name`),
#   KEY `xxx` (`name`,`age`)
# Column types:
#	  `name` varchar(20) default null
#	  `age` varchar(10) default null
# To remove this duplicate index, execute:
ALTER TABLE `dbtest01`.`ttt` DROP INDEX `name`;

# ########################################################################
# Summary of indexes                                                      
# ########################################################################

# Size Duplicate Indexes   741
# Total Duplicate Indexes  2
# Total Indexes            79

由上述检查信息中，我们可以看到，表 t3 、ttt 中存在冗余索引，并且给出对应可以删除重复索引的SQL命令。

结尾的统计信息：