I found a possibly unstable solution but it seems to work so far without any kind of notices or errors ( as of yet ). It takes advantage of both the relationship query hook to set a specific flag and the posts_clauses hook to join the postmeta table and search on that. The SQL solution was found via Iconic WP blog post of a similar nature.
/**
* Product relationship field - include searching SKU
*
* @param Array $args
* @param Array $field
* @param Integer $post_id
*
* @return $args
*/
function prefix_product_relationship_query_mods( $args, $field, $post_id ) {
$args['post_status'] = 'publish';
if( ! empty( $args['s'] ) ) {
$args['acf_sku_search'] = true;
}
return $args;
}
add_filter( 'acf/fields/relationship/query/name=field_name', 'prefix_product_relationship_query_mods', 10, 3 );
/**
* Modify the query clauses to search on the postmeta table when asked to :)
*
* @param Array $clauses
* @param WP_Query $query
*
* @return Array $clauses
*/
function prefix_acf_relationship_search_sku( $clauses, $query ) {
global $wpdb;
if( $query->get( 'acf_sku_search', false ) ) {
$clauses['join'] = " LEFT JOIN {$wpdb->postmeta} ON {$wpdb->posts}.ID = {$wpdb->postmeta}.post_id ";
$clauses['where'] = preg_replace(
"/\(\s*{$wpdb->posts}.post_title\s+LIKE\s*(\'[^\']+\')\s*\)/",
"({$wpdb->posts}.post_title LIKE $1) OR ({$wpdb->postmeta}.meta_key = '_sku' AND {$wpdb->postmeta}.meta_value LIKE $1)",
$clauses['where']
);
$query->set( 'acf_sku_search', false ); // Set to false just in case.
}
return $clauses;
}
add_filter( 'posts_clauses', 'prefix_acf_relationship_search_sku', 10, 2 );
