5

My theme calls the update_meta_cache() function 58 times per page! This function appears to run the following query based on the post in question:

SELECT post_id, meta_key, meta_value
-> FROM wp_postmeta
-> WHERE post_id IN (81649)
-> ORDER BY meta_id ASC
-> ;

The vast majority of the meta_keys (and corresponding values) returned are not necessary for the page in question (e.g. yoast_wpseo_title, _edit_last, _edit_lock are not needed for the homepage loop).

Is there a way to reduce or prevent calling of the update_meta_cache? Perhaps a way to include in a function on the pre_get_posts hook?

2

Whenever you use the function get_post_meta(), the above query will be performed to get all post meta and store in the cache. The more posts you query, the more queries are made.

To reduce the number of queries, we should pre-cache all meta values of all posts in the query before calling get_post_meta.

This is the sample code taken from a tutorial:

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;
}
  • 2
    I just came across this issue, as I'm seeing a ton of update_meta_cache() requests being made. With this tweak in my themes function.php file, I'm still seeing lots of these kind of queries? SELECT post_id, meta_key, meta_value FROM wp_postmeta WHERE post_id IN (8987) ORDER BY meta_id ASC ... am I doing something wrong? – Andrew Newby Mar 3 '16 at 8:51
  • No effect whatsoever, it's bad idea to use random 2011 code on latest wp so much changed. – Michael Rogers Mar 5 '18 at 16:48

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