Order by multiple meta fields not working when using relation “OR”

Hi,

I recently ran into a problem that I even went as far as installing a fresh install of WordPress with no plugins activated and could recreate the exakt same problem. So here’s my situation:

I have a post type called “html5-blank”. It has two meta boxes attached to it, “field1” and “field2”. I want to do a WP_Query that acts like a search in that it does a “LIKE” comparisation against those fields. I then want to sort the results on the meta fields, which I read was perfectably possible here: https://make.ww.wp.xz.cn/core/2015/03/30/query-improvements-in-wp-4-2-orderby-and-meta_query/

But I soon discovered there was a limitation to this – the relation field in the meta query had to be set to “AND” and not to “OR”. So consider this args array, sent into a WP_Query:

$args = array(
	'post_type' => array('html5-blank'),
	'posts_per_page' => '-1',
	'meta_query' => array(
		'relation' => 'AND',
		'field1' => array(
			'key'     => 'field1',
			'value'   => 'test',
			'compare' => 'LIKE'
		),
		'field2' => array(
			'key'     => 'field2',
			'value'   => 'test',
			'compare' => 'LIKE'
		),
	),

	'orderby' => array(
		'field1' => 'ASC',
		'field2' => 'ASC',
		'title' => 'ASC',
	)
);

This results in this query:

SELECT wp_posts.* FROM wp_posts INNER JOIN wp_postmeta ON ( wp_posts.ID = wp_postmeta.post_id ) INNER JOIN wp_postmeta AS mt1 ON ( wp_posts.ID = mt1.post_id ) WHERE 1=1 AND ( ( wp_postmeta.meta_key = 'field1' AND wp_postmeta.meta_value LIKE '%test%' ) AND ( mt1.meta_key = 'field2' AND mt1.meta_value LIKE '%test%' ) ) AND wp_posts.post_type = 'html5-blank' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') GROUP BY wp_posts.ID ORDER BY wp_postmeta.meta_value ASC, CAST(mt1.meta_value AS CHAR) ASC, wp_posts.post_title ASC test

This seems fine to me. But then consider this, it’s the exact same WP_Query arguments but with the relation set to “OR”:

$args = array(
	'post_type' => array('html5-blank'),
	'posts_per_page' => '-1',
	'meta_query' => array(
		'relation' => 'OR',
		'field1' => array(
			'key'     => 'field1',
			'value'   => 'test',
			'compare' => 'LIKE'
		),
		'field2' => array(
			'key'     => 'field2',
			'value'   => 'test',
			'compare' => 'LIKE'
		),
	),

	'orderby' => array(
		'field1' => 'ASC',
		'field2' => 'ASC',
		'title' => 'ASC',
	)
);

Which results in this SQL query:

SELECT wp_posts.* FROM wp_posts INNER JOIN wp_postmeta ON ( wp_posts.ID = wp_postmeta.post_id ) WHERE 1=1 AND ( ( wp_postmeta.meta_key = 'field1' AND wp_postmeta.meta_value LIKE '%test%' ) OR ( wp_postmeta.meta_key = 'field2' AND wp_postmeta.meta_value LIKE '%test%' ) ) AND wp_posts.post_type = 'html5-blank' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') GROUP BY wp_posts.ID ORDER BY wp_postmeta.meta_value ASC, CAST(wp_postmeta.meta_value AS CHAR) ASC, wp_posts.post_title ASC test

Here, the orderby fall completely apart. So I’m wondering if this is by design or some kind of bug?

I created this account here just caused I didn’t know where to put this. If this is the wrong forum, then feel free to point me in the right direction. 🙂