I'm looking at the limits of WordPress and have an optimization question. For the designers of WP, I'm trying to understand the following query in admin-functions.php:
SELECT meta_key from $wpdb->postmeta GROUP BY meta_key ORDER BY meta_id DESC LIMIT 10
I built a blog with the contents of a mailing list (http://blogs.semperen.com/nblog). The code I wrote to do the import (in *cough* perl) stuffs the info in to the db and saves the original RFC822 headers as meta data. You can see this from the front page of a post as the author of the post, which is a meta data retrieval. That's pretty quick.
I have 83,147 blog posts in the db with a total of 1,180,243 rows in the meta data table. When editing a post, the above query takes about 5 minutes and 11 seconds, which doesn't make it terribly interactive :(
So my question is, what is the point of the query? Is it to retrieve the metadata for that particular post? If so, why not do something like
SELECT meta_key FROM $wpdb->postmeta WHERE post_id = *thepostid* ORDER BY meta_id DESC
Takes about 0.01 seconds. In the original query, what relates it to the post. Looking for some guidance on this and I'm putting an articles together on it.