[wp-hackers] How to avoid multiple calls to wp_get_object_terms

[Simon Blackbourn]

Hi

I've got a custom taxonomy (resource_types) associated with a custom post
type (resource), and in my loop I'm using wp_get_object_terms to list the
taxonomies each post is in:

    $types = wp_get_object_terms( $post->ID, 'resource_types' );

However, this causes a complex database query for every post in the loop:

    SELECT t.*, tt.*
    FROM aaa_terms AS t
    INNER JOIN aaa_term_taxonomy AS tt
    ON tt.term_id = t.term_id
    INNER JOIN aaa_term_relationships AS tr
    ON tr.term_taxonomy_id = tt.term_taxonomy_id
    WHERE tt.taxonomy IN ('resource_types')
    AND tr.object_id IN (*POSTIDHERE*)
    ORDER BY t.name ASC

I can see that WordPress executes a query earlier before the loop that is
getting all this information anyway:

    SELECT t.*, tt.*, tr.object_id
    FROM aaa_terms AS t
    INNER JOIN aaa_term_taxonomy AS tt
    ON tt.term_id = t.term_id
    INNER JOIN aaa_term_relationships AS tr
    ON tr.term_taxonomy_id = tt.term_taxonomy_id
    WHERE tt.taxonomy IN ('resource_tags', 'resource_types')
    AND tr.object_id IN (387, 249, 288, 279, 232, 253, 341, 228, 301, 395)
    ORDER BY t.name ASC

What I can't figure out is if there is any way to avoid calling
wp_get_object_terms on every post (maybe accessing the data from this
earlier query somehow)?

Thanks
Simon