get_nested_categories() and friends use a lot of DB queries

[mdawaffe]

get_nested_categories(), cat_rows(), and wp_dropdown_cats() spend at least one query per category. The attached patch uses the built in caching to eliminate all but one or two queries. I do not know if this proposed method is actually any faster.

Note: these are admin-side only functions, so DB hits aren't as important.

Reduce DB hits by orders of magnitude for admin side category template functions.

Can get_categories() be used in here?

The advantage of get_all_category_ids is that, with the current cache implementation, it does the following query the first time it's run and caches the result in a PHP variable (and on the file system if it can).

SELECT * FROM wp_categories

get_categories(), though much more robust, does no caching. Without adding caching to gote_categories(), even if we're careful within one function, we'll still run a SELECT for each function dealing with the categories table. For example, categories.php run both cat_rows() and wp_dropdown_cats().

Stale patch. Needs update.

mdawaffe,

Can you freshen this up for 2.1, or should we push it off to 2.2 (remember, 4 months from 2.1 to 2.2)?

Push it. The category get functions got an overhaul which fixed most of this up.

I can revisit it later, but it's not worth looking at now to save one or two queries in the admin.

Bumping milestone for feature freeze. Bordlerline as to whether this is a feature or simply an enhancement that could be included as a fix. Patch is stale though so I'll bump.

wp_category_checklist()

(In [7737]) wp_category_checklist() and wp_link_category_checklist() to replace the nested cats code. see #2621

(In [7739]) Don't query post cats if no post. see #2621

fixed?