[wp-trac] [WordPress Trac] #58368: WordPress dashboard is very slow when there are many comments (and the database isn't great)

[WordPress Trac]

#58368: WordPress dashboard is very slow when there are many comments (and the
database isn't great)
--------------------------+--------------------------
 Reporter:  Guss77        |       Owner:  (none)
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  6.3
Component:  Comments      |     Version:  6.2.2
 Severity:  minor         |  Resolution:
 Keywords:  has-patch     |     Focuses:  performance
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Comment (by westonruter):

 Skipping sorting when only querying for a count makes sense to me.

 Per @joemcgill, the problematic code is the call to `wp_count_comments()`
 in [https://github.com/WordPress/wordpress-
 develop/blob/d51ee6ce097fb288aca9da1f95899fc3d77c0fa4/src/wp-
 admin/menu.php#L89-L107 wp-admin/menu.php].

 This function uses the object cache to [https://github.com/WordPress
 /wordpress-develop/blob/d51ee6ce097fb288aca9da1f95899fc3d77c0fa4/src/wp-
 includes/comment.php#L1438-L1448C2 store the comment count for a post]. If
 this were made into a transient instead, this would address the lack of
 persistent object cache.

 Aside: @Guss77 another option for you would be to add a
 `wp_count_comments` filter in [https://github.com/WordPress/wordpress-
 develop/blob/d51ee6ce097fb288aca9da1f95899fc3d77c0fa4/src/wp-
 includes/comment.php#L1433-L1436 that same function]. This would allow you
 to short-circuit the expensive query, and you could use the query that
 lacks the `ORDER BY`.

 Lastly, I just wanted to note that in the AMP plugin we had this same
 problem of a count in the menu slowing down admin page loads, here
 specifically the count for AMP validation errors. We solved the problem by
 fetching the count over the REST API and then storing it in
 `sessionStorage`, and we only do the fetch once the menu item is actually
 shown (via `IntersectionObserver`): this would help in the case where the
 admin menu is collapsed. See the code here: https://github.com/ampproject
 /amp-wp/blob/develop/assets/src/amp-validation/counts/index.js

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Ticket URL: <https://core.trac.wordpress.org/ticket/58368#comment:14>
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