Add a filter to get_available_post_mime_types() function to allow overriding extremely slow query.

[maciejmackowiak]

On sites sites with lot of posts the query used in get_available_post_mime_types is extremely slow.
It would be nice to have a filter that will allow us to override this query and for example cache the results.

It could be something simillar to this filter:
https://core.trac.wordpress.org/browser/tags/5.6/src/wp-includes/media.php#L4172

<?php
function get_available_post_mime_types($type = 'attachment') {
        global $wpdb;
        $types = apply_filters('get_available_post_mime_types', null, $type);
        if ( ! is_array( $types ) ) {
                $types = $wpdb->get_col($wpdb->prepare( "SELECT DISTINCT post_mime_type FROM $wpdb->posts WHERE post_type = %s", $type ) );
        }
        return $types;
}

[archon810]

+1 for this.

For us, it adds an additional 0.35s or so (right now, more if db is loaded).

SELECT SQL_NO_CACHE DISTINCT post_mime_type
FROM wp_posts
WHERE post_type = 'attachment'
> OK
> Time: 0.35s

On the grid view it is called from here:
​https://github.com/WordPress/WordPress/blob/785cb6cc7d4d17ef0aa16b187dcfb6a8dc513e1b/wp-admin/includes/class-wp-media-list-table.php#L97

It calls this function:
​https://github.com/WordPress/WordPress/blob/00680f2e89766e4ac9a71c68a8cccd3a141afb34/wp-admin/includes/post.php#L1287

And here is the query:
​https://github.com/WordPress/WordPress/blob/bf83c368fdfcee2b879d00b193f505038e1681f0/wp-includes/post.php#L7517

We were able to cache and greatly speed up this query already:

SELECT DISTINCT YEAR( post_date ) AS year, MONTH( post_date ) AS month
FROM wp_posts
WHERE post_type = 'attachment'
AND post_status != 'auto-draft'
AND post_status != 'trash'
ORDER BY post_date DESC

and I hope with the new proposed filter, we will be able to speed up the site even more.

https://core.trac.wordpress.org/ticket/52759

[maciejmackowiak]

Here is a pull request:
​https://github.com/WordPress/wordpress-develop/pull/1088/files

[Mista-Flo]

Hi there,

I'm definitely for a filter to short circuit this slow query, but I think first we need to fix this slow query by implementing a cache, wether it use the internal cache API system from Core or the Transient API, (check the slack thread we started for further comments).

Related tickets talking about the performance issues of this query: https://core.trac.wordpress.org/ticket/43658

[archon810]

Great idea 💡.

[maciejmackowiak]

check the slack thread we started for further comments

Can you point me to that thread, please?

[archon810]

@maciejmackowiak The link is right above. ​https://wordpress.slack.com/archives/core-media/p1615475295157700