How to find source of these strange SQL queries?

Question

I'm looking at my slow queries and i don't understand how some bot or person is doing them. They look like this: (i copy/paste them no placeholders!)

SELECT post_id FROM wp_postmeta, wp_posts WHERE ID = post_id AND post_type = 'rentals' AND meta_key = '_wp_old_slug' AND meta_value = '%5dsibbo-cmp-layoutthor-cookiesdiv';

SELECT post_id FROM wp_postmeta, wp_posts WHERE ID = post_id AND post_type = 'rentals' AND meta_key = '_wp_old_slug' AND meta_value = 'sauved2ahukewjjx9uu2zb8ahvwbxaihz3waceqfnoecaiqagusgaovvaw2fcppukbhgtva5flmmmnzl';

These are increasing server load in the server. I don't understand how can you even query by meta_value in the front end?! Makes no sense to me.

Answer 1

They're from WordPress. They come from the wp_old_slug_redirect() function which is run whenever there is a 404. The purpose is to check if the requested URL was the old URL for a post so that it can redirect to the new URL.

If you're seeing a lot of these then it means you're getting a lot of 404 hits. The slugs in your example suggest that it's probably bots, but it's hard to say. I highly doubt this query alone is causing significant server load. It's probably the volume of the requests themselves that is the problem.