wp query - Reduce or prevent calling of update_meta_cache

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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?

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?

• wp-query
• post-meta
• pre-get-posts

Share Improve this question asked May 6, 2015 at 9:50 JoshJosh 12711 gold badge33 silver badges1111 bronze badges 1

• Just a sidenote: Explanation of update_post_(meta/term)_cache. – Howdy_McGee ♦ Commented Feb 1, 2016 at 16:32

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2 Answers 2

Sorted by: Reset to default 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;
}

For a WP_Query, caching can be disabled by setting certain caching parameters to false.

Similarly for WP_Term_Query, it can be disabled by including update_term_meta_cache => false in the query args.

Additionally, the filter update_{$meta_type}_metadata_cache can be used to disable metadata caching for all queries on the object type. (ex. update_post_metadata_cache, update_term_metadata_cache, etc)

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