Database slowdown after update to 3.4.1

Question

I own a wordpress installation, and Updated to 3.4.1.

After the upgrade, I got a very strange slowdown to my wordpress.

After all, I used the

define('SAVEQUERIES', true);

in my wp-config.php with combined with the following code in my theme footer.php

global $wpdb;
echo "<pre>";
print_r($wpdb->queries);
echo "</pre>";

and I found that while I don't have many queries (49 queries I got), there are

• 4 Quiries took more than 9''
• 3 Quiries took more than 8''
• 4 Quiries took more than 7''
• 4 Quiries took more than 6''
• 8 Quiries took more than 5''
• 1 Quiry took more than 4''

Here I will show you some of the queries:

/* Execution time 7.0095062E-5 */
SELECT t.*, tt.* FROM wp_terms AS t INNER JOIN wp_term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy IN ('category') AND tt.count > 0 ORDER BY t.name ASC

/* Execution time 5.3167343E-5 */
SELECT post_id, meta_key, meta_value FROM wp_postmeta WHERE post_id IN (77375,77379,77381)

/* Execution time 9.2029572E-5 */
SELECT wp_posts.* FROM wp_posts WHERE ID IN (77381,77379,77375)

In most of the queries there query is simple, with no complexity, and I cannot imagine why that queries are so slow.

The WordPress database contains in about 60.000 records and running on percona.

Any idea for that issue and how maybe can I fix it ?

Answer 1

If you've got 60,000 records, try cleaning post/page revisions; these really accumulate and cause excessively long queries. I've seen database sizes drop 90% with huge increases in performance.

Run the query below in phpmyadmin or from the command line and then optimize:

DELETE a,b,c
FROM wp_posts a
LEFT JOIN wp_term_relationships b ON (a.ID = b.object_id)
LEFT JOIN wp_postmeta c ON (a.ID = c.post_id)
WHERE a.post_type = 'revision'

Talk to your web host, too. Maybe MySQL or your CPU is being throttled down.

Answer 2

you are right ... there shouldn't be a problem with performance and your database my just need some improvements for caching.

Are you running W3 Total Cache - this should have an immediate benefit for your site performance and you'll want it to cache database if that is possible with your Server.

Then -- take a backup of your SQL database and you should also optimise & repair the tables.