--- name: "mysqlindexcheck" section: "1" platform: "linux" package: "mysql-utilities" version: "1.6.4-1" release: "Debian 9 (Stretch)" platforms: ["linux"] url: "https://new.carta.tech/mysqlindexcheck" --- # mysqlindexcheck(1) Identify Potentially Redundant Table Indexes ## NAME mysqlindexcheck - Identify Potentially Redundant Table Indexes ## SYNOPSIS **mysqlindexcheck \[***options***\]** *db***\[***:table***\] ...** ## DESCRIPTION This utility reads the indexes for one or more tables and identifies duplicate and potentially redundant indexes. To check all tables in a database, only specify the database name. To check a specific table, name the table in *db.table* format. It is possible to mix database and table names. You can scan tables in any database except the internal databases **mysql**, **INFORMATION\_SCHEMA**, and **performance\_schema**. Depending on the index type, the utility applies the following rules to compare indexes (designated as idx\_a and idx\_b): • **BTREE** idx\_b is redundant to idx\_a if and only if all the columns from idx\_b are a prefix of idx\_a. Order and uniqueness count. • **HASH** idx\_a and idx\_b are redundant if they are duplicates, i.e. if and only if they contain the same columns in the same order. • **SPATIAL** idx\_a and idx\_b are duplicates if and only if they contain the same column (only one column is permitted). • **FULLTEXT** idx\_b is redundant to idx\_a if and only if all columns in idx\_b are included in idx\_a. Order does not count. To see DROP statements drop redundant indexes, specify the **--show-drops** option. To examine the existing indexes, use the **--verbose** option, which prints the equivalent **CREATE INDEX** (or **ALTER TABLE**) for primary keys. To display the best or worst non-primary key indexes for each table, use the **--best** or **--worst** option. This causes the output to show the best or worst indexes from tables with 10 or more rows. By default, each option shows five indexes. To override that, provide an integer value for the option. To change the format of the index lists displayed for the **--show-indexes**, **--best**, and **--worst** options, use one of the following values with the **--format** option: • **grid** (default) Display output in grid or table format like that of the **mysql** client command-line tool. • **csv** Display output in comma-separated values format. • **tab** Display output in tab-separated format. • **sql** Print SQL statements rather than a list. • **vertical** Display output in single-column format like that of the \\G command for the **mysql** client command-line tool. **Note**\ The **--best** and **--worst** lists cannot be printed as SQL statements. OPTIONS.PP **mysqlindexcheck** accepts the following command-line options: • --help Display a help message and exit. • --license Display license information and exit. • --best\[=\\] If **--stats** is given, limit index statistics to the best *N* indexes. The default value of *N* is 5 if omitted. • --format=\, -f\ Specify the index list display format for output produced by **--stats**. Permitted format values are **grid**, **csv**, **tab**, **sql**, and **vertical**. The default is **grid**. • --report-indexes, -r Reports if a table has neither UNIQUE indexes nor a PRIMARY key. • --server=\ Connection information for the server. To connect to a server, it is necessary to specify connection parameters such as the user name, host name, password, and either a port or socket. MySQL Utilities provides a number of ways to supply this information. All of the methods require specifying your choice via a command-line option such as --server, --master, --slave, etc. The methods include the following in order of most secure to least secure. • Use login-paths from your .mylogin.cnf file (encrypted, not visible). Example : \<*login-path*\>\[:\<*port*\>\]\[:\<*socket*\>\] • Use a configuration file (unencrypted, not visible) Note: available in release-1.5.0. Example : \<*configuration-file-path*\>\[:\<*section*\>\] • Specify the data on the command-line (unencrypted, visible). Example : \<*user*\>\[:\<*passwd*\>\]@\<*host*\>\[:\<*port*\>\]\[:\<*socket*\>\] • --show-drops, -d Display **DROP** statements for dropping indexes. • --show-indexes, -i Display indexes for each table. • --skip, -s Skip tables that do not exist. • --ssl-ca The path to a file that contains a list of trusted SSL CAs. • --ssl-cert The name of the SSL certificate file to use for establishing a secure connection. • --ssl-cert The name of the SSL key file to use for establishing a secure connection. • --ssl Specifies if the server connection requires use of SSL. If an encrypted connection cannot be established, the connection attempt fails. Default setting is 0 (SSL not required). • --stats Show index performance statistics. • --verbose, -v Specify how much information to display. Use this option multiple times to increase the amount of information. For example, **-v** = verbose, **-vv** = more verbose, **-vvv** = debug. • --version Display version information and exit. • --worst\[=\\] If **--stats** is also passed in, limit index statistics to the worst *N* indexes. The default value of *N* is 5, if omitted. NOTES.PP You must provide connection parameters (user, host, password, and so forth) for an account that has the appropriate privileges to read all objects accessed during the operation. For the **--format** option, the permitted values are not case sensitive. In addition, values may be specified as any unambiguous prefix of a valid value. For example, **--format=g** specifies the grid format. An error occurs if a prefix matches more than one valid value. The path to the MySQL client tools should be included in the PATH environment variable in order to use the authentication mechanism with login-paths. This will allow the utility to use the **my\_print\_defaults** tools which is required to read the login-path values from the login configuration file (.mylogin.cnf). EXAMPLES.PP To check all tables in the employees database on the local server to see the possible redundant and duplicate indexes, use this command: ``` shell> mysqlindexcheck --server=root@localhost employees # Source on localhost: ... connected. # The following indexes are duplicates or redundant \ for table employees.dept_emp: # CREATE INDEX emp_no ON employees.dept_emp (emp_no) USING BTREE # may be redundant or duplicate of: ALTER TABLE employees.dept_emp ADD PRIMARY KEY (emp_no, dept_no) # The following indexes are duplicates or redundant \ for table employees.dept_manager: # CREATE INDEX emp_no ON employees.dept_manager (emp_no) USING BTREE # may be redundant or duplicate of: ALTER TABLE employees.dept_manager ADD PRIMARY KEY (emp_no, dept_no) # The following indexes are duplicates or redundant \ for table employees.salaries: # CREATE INDEX emp_no ON employees.salaries (emp_no) USING BTREE # may be redundant or duplicate of: ALTER TABLE employees.salaries ADD PRIMARY KEY (emp_no, from_date) # The following indexes are duplicates or redundant \ for table employees.titles: # CREATE INDEX emp_no ON employees.titles (emp_no) USING BTREE # may be redundant or duplicate of: ALTER TABLE employees.titles ADD PRIMARY KEY (emp_no, title, from_date) ``` PERMISSIONS REQUIRED.PP Regarding the privileges needed to run this utility, the user needs SELECT privilege on the mysql database as well as for the databases which tables are being checked. ## COPYRIGHT Copyright © 2006, 2016, Oracle and/or its affiliates. All rights reserved. This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License. This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with the program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see http://www.gnu.org/licenses/. ## SEE ALSO For more information, please refer to the MySQL Utilities and Fabric documentation, which is available online at http://dev.mysql.com/doc/index-utils-fabric.html ## AUTHOR Oracle Corporation (http://dev.mysql.com/).