Just a random post about a WordPress plugin (hotel booking).
For the site in question, I have a script running which alerts me to any long running (>600s) MySQL queries (or causes of deadlock) and attempts to kill them. When it does this it emails me….
So, the site/MySQL was trying to run queries like this :
DELETE FROM wp_mphb_sync_logs WHERE queue_id IN (SELECT queue_id FROM wp_mphb_sync_queue WHERE queue_name < '1639573980');
which I did an explain, it showed there were > 5 million rows to examine (none of which are actually deleted by the query, so I assume the 5 million rows are all for now invalid queue_id entries).
Adding an index on the wp_mphb_sync_logs.queue_id field didn’t really help speed up the delete … and googling around and checking the plugin’s source code, led me to think it was safe (enough) to do a ‘TRUNCATE wp_mphb_sync_logs‘.
Now that’s done the table has remained empty 12 hours later; so I think everything’s fine.
This post is mostly because the plugin’s forum requires a paid membership to contribute; and I’m not paying $400 just to post “doing this worked for me”.