This document provides 13 tips for WordPress developers to optimize their database performance. It recommends making regular database dumps, using wp-cli commands to manage the database, cleaning up bloated tables like wp_options and wp_postmeta, configuring the database server properly, using object caching like Redis to improve performance, and monitoring performance with tools like slow logs and profiling. The tips aim to help developers identify and address common database issues that can impact a WordPress site's security and speed.

1. 13 Things
Every Developer
Should Know About
Their Database to
Run WordPress
Optimally
WordCamp Europe 2020
Otto Kekäläinen
@ottokekalainen
seravo.com

2. ● Linux and open source advocate
● Written WP themes and plugins,
contributed to WordPress Core,
MySQL, MariaDB…
● CEO, sysadmin and developer at
Seravo.com – WordPress
hosting and upkeep
Otto Kekäläinen

3. Premium
Hosting and
Upkeep for
WordPress

4. The database is involved in both!
○ contains all your valuable data
○ often the bottleneck of performance
Common Issues in WordPress:
Security & Speed

5. DATABASE
THE SINGLE MOST
IMPORTANT PART OF
YOUR WORDPRESS
INFRASTRUCTURE

6. TIP #1: MAKE (USE OF) DB DUMPS
Benefits
● Copying your WordPress files is not enough for a
backup
● The database dump file format is
○ plain-text: view and modify it as much as you like
○ interoperable: import it into a MySQL or MariaDB
database server anywhere
Command line: mysqldump or wp db export

7. TIP #1: MAKE (USE OF) DB DUMPS
$ wp db export --skip-extended-insert --allow-root --single-transaction
example-after.sql
$ diff -u example-before.sql example-after.sql
--- example-before.sql 2018-08-30 10:58:23.243836204 +0300
+++ example-after.sql 2018-08-30 10:57:57.771762687 +0300
@@ -2,3 +2,4 @@
INSERT INTO `wp_terms` VALUES (70,'transients','transients',0,0);
INSERT INTO `wp_terms` VALUES (71,'code','code',0,0);
INSERT INTO `wp_terms` VALUES (72,'performance','performance',0,0);
+INSERT INTO `wp_terms` VALUES (73,'WordPress','wordpress',0,0);
What are these tables and columns? See
codex.wordpress.org/Database_Description

8. TIP #2: LEARN WP-CLI DB COMMANDS
List them all with wp db --help
My most used ones:
● wp db export/import
● wp db size --tables --all-tables --size_format=mb
● wp db cli
● wp db search --one_line
● wp search-replace --all-tables http://example.com
https://example.com
^ My favourite!

9. TIP #3: USE ADMINER TO BROWSE
● Adminer is one file, easy to install and update
● Less security vulnerabilities than in PHPMyAdmin

10. TIP #4: WP_OPTIONS AND AUTOLOAD
● Every single WordPress page load runs this query
SELECT * FROM wp_options WHERE autoload = 'yes'

11. TIP #4: WP_OPTIONS AND AUTOLOAD
● If wp_options table is larger than 1 MB, try to clean it up
● Find rows with the largest amount of data in the option_value
field:
○ SELECT option_name, length(option_value) FROM
wp_options WHERE autoload='yes' ORDER BY
length(option_value) DESC LIMIT 30
● File bugs against stupid plugins polluting your options table
● If cannot be cleaned, add an index on autoload
○ CREATE INDEX autoloadindex ON wp_options(autoload,
option_name)

12. TIP #5: WP_POSTMETA BLOAT
● Any site using custom post types or WooCommerce is likely to have a
big wp_postmeta table. While every post adds just one new row (and
many fields) to the database and keeping the number of column names
constant, the use of add_post_meta() calls will bloat the database with
tens or hundreds of rows per post where each row only contains two
fields: name and value.
● Find the meta_key naming patterns with most amount of rows:
○ SELECT substring(meta_key, 1, 20) AS
key_start, count(*) AS count FROM
wp_postmeta GROUP BY key_start
ORDER BY count DESC LIMIT 30

13. Unfortunately database bloat
and stupid use of database is
common in plugins.
We need to do more to raise
awareness about database
best practices!

14. TIP #6: LEARN SQL
● It is not enough that you know PHP, learn SQL as well.
● The database has 20 years of engineering on how to fetch a
small set of data from a huge set of data as quickly as
possible. Don’t try to reinvent that in PHP.
● Don’t put everything in wp_postmeta. Don’t be afraid of
creating your own custom tables that have the correct
columns, relations and indexes already defined.
● Learn what ‘index’ means and why you don’t want to be
causing ‘full table scans’ in the database.

15. TIP #7: BUT DON’T USE SQL DIRECTLY
● In WordPress PHP code use get_posts() for basics
● Use the WP_Query class for more advanced cases
● When WP_Query does not fit, use the $wpdb->get_row(),
$wpdb->insert() etc methods
● If you really need raw
SQL, don’t access the
database directly,
instead use
$wpdb->prepare() and
$wpdb->query() to
avoid SQL injection
vulnerabilities

16. TIP #8: CONFIGURE DATABASE SERVER
1. MariaDB preferred over Oracle MySQL
2. Use a recent version (MariaDB 10.3+)
3. Storage engine: InnoDB (not MyISAM)
4. Character set: UTFMB4 (for emojis )
5. Collation: your local sorting order A-Ö
6. ..and optimize all the other settings
Or hire a database administrator, or use a
WordPress hosting company that does this for you.

17. Reasons to
switch to
MariaDB
● MariaDB development is more open
and vibrant
● Quicker and more transparent
security releases
● More cutting edge features
● More storage engines
● Better performance for WP
● Galera active-active master
clustering
● Oracle stewardship is uncertain
● MariaDB has leapt in popularity
● Compatible and easy to migrate
https://seravo.fi/2015/10-reasons-to-migrate-t
o-mariadb-if-still-using-mysql

18. TIP #9: TRANSIENTS AND OBJECT CACHE
● Use Redis cache or similar
to store transients and
sessions so they can be
removed from wp_options
// Simple WP Transient API example
if ( ! $result = get_transient( ‘q_result’ ) ) {
$result = run_complex_and_slow_query();
set_transient( ‘q_result’, $result, 3600 );
}
echo $result;
● Redis and WP Transients
API will ease the load on
the database and help you
make super fast sites

19. TIP #10: MONITOR PERFORMANCE
● Take a peek with
SHOW PROCESSLIST;
● Analyse unusual slowness by
enabling mariadb-slow.log
logging
● Enable Tideways or similar
service for sampling your
WordPress site PHP execution in
production to find bottlenecks

20. AND ONE EXTRA TIP:
NEVER PUSH YOUR DEV
DATABASE INTO PRODUCTION

21. TIP #11: DB CLEANUP
● DELETE FROM `wp_posts` WHERE post_type =
'revision' AND post_date NOT LIKE '2018-%';
● DELETE FROM wp_options WHERE option_name
LIKE ('_transient_%') OR option_name LIKE
('_site_transient_%');
● Checkout what
wp-content/plugins/*/uninstall.php contains and
what plugins are supposed to clean away if they
are uninstalled

22. TIP #12: EXPLAIN, PLEASE
● You can append ‘EXPLAIN’ to any query and the
optimizer will tell how it is running the query
● EXPLAIN SELECT * FROM wp_options WHERE
autoload = 'yes';
MariaDB [wp_palvelu_06a4ad]> explain SELECT * FROM wp_options WHERE autoload = 'yes';
+------+-------------+------------+------+---------------+------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+------+-------------+------------+------+---------------+------+---------+------+------+-------------+
| 1 | SIMPLE | wp_options | ALL | NULL | NULL | NULL | NULL | 415 | Using where |
+------+-------------+------------+------+---------------+------+---------+------+------+-------------+

23. TIP #13: TEST WITH DUMMY DATA
● While developing a site, load lots of dummy data into it so you
can test how your site looks and performs with 100, 1000 or 100
000 posts.
● Basic: Import themeunittestdata.wordpress.xml
○ codex.wordpress.org/Theme_Unit_Test
● More data: wp post generate
○ curl http://loripsum.net/api/5 |
wp post generate --post_content --count=10
● More realism: wp-cli-fixtures
○ github.com/nlemoine/wp-cli-fixtures

24. Thank you!
Seravo.com @Seravo @ottokekalainen

25. See also
Make Your Site Faster with Caching
https://seravo.com/blog/wordpress-cache/
300% faster WordPress load times with transients
https://seravo.com/blog/faster-wordpress-with-transients/
5 common reasons why your WordPress site is slow
https://youtu.be/8sJExUO-U4A
Improving WordPress Performance with XDebug and PHP Profiling
https://youtu.be/oKcIS5A-6_c