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 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
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 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
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.