One random post from multiple custom post types

Question

I'm building a post grid on my front page and I'd like to show one random post per CPT. At the moment, CPT are queried out in a query array:

<?php
$c = 1; //init counter
$bpr = 3; //boxes per row   
$wp_query = new WP_Query(array('showposts' => 9, 'orderby'=> 'rand', 'post_type' => array('productions',  'plays', 'movies', 'theatres', 'directors', 'artists', 'countries', 'events', 'grades')));
while( have_posts() ) : the_post(); ?>


<div class="post" id="post-<?php the_ID(); ?>">
   <p><?php $post_type = get_post_type_object( get_post_type($post) ); echo $post_type->label ; ?></p>
   <a href="<?php the_permalink() ?>" rel="bookmark">
      <?php if ( has_post_thumbnail() ) {
         the_post_thumbnail('thumbnail');
        } else { ?>
        <img src="<?php bloginfo('template_directory'); ?>/img/fallback_image.jpg" alt="<?php the_title(); ?>" />
      <?php } ?>
   </a>
</div>
<?php
if($c == $bpr) :
?>
<div class="clr"></div>
<?php
$c = 0;
endif;
?>
<?php
        $c++;
        endwhile;

?>

So the problem with this array is that it starts to dublicate the CPT's when I query them, sometimes even it queries 4 random posts from CPT.

One solution would be to create 9 different queries - one for each CPT, but this seems to be overkill for the front page.

Is there a way to really only query 1 random post per CPT in a way that wouldn't affect the page loading time so much?

Answer 1

This method might work for you. You will have to grab more posts than you need but it is better than doing 9 queries.

$args = array(
    'post_type' => array( 'type1', 'type2', 'type3', 'etc...' ),
    'posts_per_page' => -1
    );

$myquery = new WP_Query( $args );
    $type1 = 0; $type2 = 0; $type3 = 0;  $count = 0;
    while ( $myquery->have_posts() ) : $myquery->the_post();

    if ( $post->post_type == 'type1' ) $type1++; 
    if ( $post->post_type == 'type1' && $type1 > 1 ) continue;

    if ( $post->post_type == 'type2' ) $type2++; 
    if ( $post->post_type == 'type2' && $type2 > 1 ) continue;

    if ( $post->post_type == 'type3' ) $type3++; 
    if ( $post->post_type == 'type3' && $type3 > 1 ) continue;

    // I stopped at 3 but keep going as far as you need.

    $count++; if ( $count > 9 ) continue;

    // Do Stuff

    endwhile;