MYSQLINDEXCHECK(1) MySQL Utilities MYSQLINDEXCHECK(1)
NAME
mysqlindexcheck - Check for redundant or duplicate indexes on a list tables or databases
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, specify only the database name. To check a specific table, name the table in db.table format. It is pos-
sible 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 the first n columns in idx_b also appear in idx_a. Order and uniqueness count.
HASH idx_a and idx_b are duplicates if and only if they contain the same columns in the same order. Uniqueness counts.
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 counts.
To see DROP statements to 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 nonprimary 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 monitor.
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 monitor.
Note: The --best and --worst lists cannot be printed as SQL statements.
OPTIONS
mysqlindexcheck accepts the following command-line options:
--help Display a help message and exit.
--best[=<N>]
If --stats is given, limit index statistics to the best N indexes. The default value of N is 5 if omitted.
--format=<index_format>, -f<index_format>
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.
--server=<source>
Connection information for the server in <user>[:<passwd>]@<host>[:<port>][:<socket>] format.
--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.
--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[=<N>]
If --stats is given, limit index statistics to the worst N indexes. The default value of N is 5 if omitted.
NOTES
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.
EXAMPLES
To check all tables in the employees database on the local server to see the possible redundant and duplicate indexes, use this command:
$ 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)
COPYRIGHT
Copyright (c) 2010, 2012, Oracle and/or its affiliates. All rights reserved.
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 of the License.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MER-
CHANTABILITY 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 this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
AUTHOR
MySQL Utilities Team
COPYRIGHT
2010, Oracle and/or its affiliates. All rights reserved.
1.0.3 May 09, 2012 MYSQLINDEXCHECK(1)