Add_Custom_Fields_To_Search::cf_search_join( string $join )

		function cf_search_join( $join ) {
			global $wpdb;

			if ( ! is_search() || $this->is_media_library() ) {
				return $join;
			}

			// join to search post meta values like year, make, model, trim, etc
			$join .= ' LEFT JOIN ' . $wpdb->postmeta . ' ON ' . $wpdb->posts . '.ID = ' . $wpdb->postmeta . '.post_id ';

			// these joins are so taxonomy terms like Sport Utility Vehicle => suv are included
			$join .= 'LEFT JOIN ' . $wpdb->term_relationships . ' tr ON ' . $wpdb->posts . '.ID = tr.object_id '
			. 'INNER JOIN ' . $wpdb->term_taxonomy . ' tt ON tt.term_taxonomy_id = tr.term_taxonomy_id '
			. 'INNER JOIN ' . $wpdb->terms . ' t ON t.term_id = tt.term_id ';

			return $join;
		}