clear_embed_cache not working for Multisite/Network

Hi,

while trying to solve another problem (I’ll make a separate post), I stumbled upon this bug in the clear_embed_cache function (inc/class-embed-privacy.php):

It seems that the code does not clear the postmeta tables from old embed-privacy entries on multisite installations. The code is here:

/**
	 * Embeds are cached in the postmeta database table and need to be removed
	 * whenever the plugin will be enabled or disabled.
	 */
	public function clear_embed_cache() {
		global $wpdb;
		
		// the query to delete cache
		$query = "DELETE FROM	$wpdb->postmeta
				WHERE			meta_key LIKE '%_oembed_%'";
		
		if ( is_plugin_active_for_network( 'embed-privacy/embed-privacy.php' ) ) {
			// on networks we need to iterate through every site
			$sites = get_sites( 99999 );
			
			foreach ( $sites as $site ) {
				switch_to_blog( $site );
				$wpdb->query( $query );
			}
		}
		else {
			$wpdb->query( $query );
		}
	}

The thing is, that the query is not updated to match the blogs’ individual postmeta table names. I tried my best coming up with a dynamic solution, but unfortunately I could not figure out a way to dynamically the table name, so instead I came up with this adapted query to be executed while in the foreach loop:

$query2 = "DELETE FROM	".$wpdb->get_blog_prefix($site->blog_id)."postmeta
				WHERE			meta_key LIKE '%_oembed_%'";

This query did successfully delete all the post meta data from all the blogs on dis-/reenabling the plugin on my multisite.

I think you also can skip the switch_to_blog part. Another way would be to use the delete_post_meta function but then you either have to loop over all post metas to find the keys you want to delete or store this information elsewhere.