wp_get_object_terms - no caching mechanism in place - results in duplicate queries

[webgeekconsulting]

wp_get_object_terms() isn't caching queries which results in duplicate queries against the database. See the following debug info:

SELECT t.term_id FROM hf9v_terms AS t INNER JOIN hf9v_term_taxonomy AS tt ON tt.term_id = t.term_id INNER JOIN hf9v_term_relationships AS tr ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy IN ('product_category') AND tr.object_id IN (229) ORDER BY t.name ASC
include('wp-admin/edit-form-advanced.php'), do_meta_boxes, call_user_func, post_categories_meta_box, wp_popular_terms_checklist, wp_get_object_terms 

SELECT t.term_id FROM hf9v_terms AS t INNER JOIN hf9v_term_taxonomy AS tt ON tt.term_id = t.term_id INNER JOIN hf9v_term_relationships AS tr ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy IN ('product_category') AND tr.object_id IN (229) ORDER BY t.name ASC
include('wp-admin/edit-form-advanced.php'), do_meta_boxes, call_user_func, post_categories_meta_box, wp_terms_checklist, wp_get_object_terms

I've attached a patch that creates a cache of the database query - similar to what is being suggested in ticket #29894.

[webgeekconsulting]

taxonomy.php patch

[boonebgorges]

Thanks for the patch! As in #29894, I like the consolidation of cache keys. And as in #29894, I have a couple questions and concerns:

• It looks at a glance like the second query (2332 right hand side in https://core.trac.wordpress.org/attachment/ticket/29942/taxonomy.php.patch) is pulling up information that is available in the main query being fired earlier. No need for a second query, and no need for a separate cache. This needs testing.
• Unit test coverage for wp_get_object_terms() is pretty lackluster. I'm very wary of making these sorts of changes until we at least get basic coverage.

[dd32]

Just run into this again, if there's anyone out there who wants to put a little time into digging into Taxonomies, this could be an interesting patch to continue with @boonebgorges concerns :)

[dd32]

Should also mention for others; You can use get_the_terms() which is the cached variant of wp_get_object_terms().

[boonebgorges]

This ended up being resolved as part of the WP_Term_Query migration in #37198.