Reducing postmeta queries with update_meta_cache()

functions.php

add_filter( 'posts_results', 'cache_meta_data', 9999, 2 );
function cache_meta_data( $posts, $object ) {
    $posts_to_cache = array();
    // this usually makes only sense when we have a bunch of posts
    if ( empty( $posts ) || is_wp_error( $posts ) || is_single() || is_page() || count( $posts ) < 3 )
        return $posts;
         
    foreach( $posts as $post ) {
        if ( isset( $post->ID ) && isset( $post->post_type ) ) {
            $posts_to_cache[$post->ID] = 1;
        }
    }
     
    if ( empty( $posts_to_cache ) )
        return $posts;
 
    update_meta_cache( 'post', array_keys( $posts_to_cache ) );
    unset( $posts_to_cache );
 
    return $posts;
}