Not all code removed responsible for comments caching in Recent Comments widget

[alexvorn2]

As we all know - in 4.4.0, Fragment caching for comments was removed in favor of split queries.

But in the \wp-includes\widgets\class-wp-widget-recent-comments.php line 104 we have

// Prime cache for associated posts. (Prime post term cache if we need it for permalinks.)
$post_ids = array_unique( wp_list_pluck( $comments, 'comment_post_ID' ) );
_prime_post_caches( $post_ids, strpos( get_option( 'permalink_structure' ), '%category%' ), false );

I'm not sure what this code does but it is related to caching.

DO we need to remove this code?

[boonebgorges]

Thanks for the ticket.

The "fragment caching" referred to in [34581] is the caching of fully-formed HTML markup. The commit message on [34581] suggests that, after some performance improvements to WP_Comment_Query, this HTML caching is no longer worth the trouble of invalidation.

The widget still leverages the object cache, when appropriate. The snippet of code you've highlighted is responsible for loading the comment post items into the cache, so that subsequent calls to get_permalink() (via get_comment_link()) don't require additional database queries. It's still relevant.

[alexvorn2]

Thanks for clarification.