Custom wp_query differs on index page and category page

Question

I've been banging my hand against the wall for a little while now trying to figure this out.

Can anyone explain to me why this custom wp_query prduces two different sql statements, one for the index page (which is correct) and one for the category page (which is wrong)

function myFunction( $category )
{
    if(!$category) return;

    $query = array(
        'post_type' => 'download',
    );

    $query['tax_query'][] = array(
        'taxonomy' => 'download_category',
        'terms' => explode( ',', $category ),
        'field' => 'slug'
    );

    $downloads = new WP_Query( $query );

    return intval($downloads->found_posts);
}

Index sql (correct):

SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts INNER JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id) WHERE 1=1 AND ( wp_term_relationships.term_taxonomy_id IN (20) ) AND wp_posts.post_type = 'download' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'refunded' OR wp_posts.post_status = 'failed' OR wp_posts.post_status = 'revoked' OR wp_posts.post_status = 'abandoned' OR wp_posts.post_status = 'active' OR wp_posts.post_status = 'inactive' OR wp_posts.post_status = 'private') GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC LIMIT 0, 10

Category sql (wrong):

SELECT SQL_CALC_FOUND_ROWS wp_posts.ID FROM wp_posts INNER JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id) WHERE 1=1 AND ( wp_term_relationships.term_taxonomy_id IN (15) ) AND wp_posts.post_type IN ('nav_menu_item', 'post', 'eddset') AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'refunded' OR wp_posts.post_status = 'failed' OR wp_posts.post_status = 'revoked' OR wp_posts.post_status = 'abandoned' OR wp_posts.post_status = 'active' OR wp_posts.post_status = 'inactive' OR wp_posts.post_author = 1 AND wp_posts.post_status = 'private') GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC LIMIT 0, 10

It is ignoring the post_type but can't figure out why?

Any help much appreciated.

Answer 1

I can only assume that there is filter running on the category page that is overwriting your post type.

1. Try adding 'suppress_filters'=>true to your query arguments, but that only works for some filters not all. I suspect it will not work in this case.
2. Or find the filter that is altering the query and modify it so that it does not overwrite existing post_type arguments, which is what I assume the filter does.

I expect that option #2 is going to be the solution.