[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)
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 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 has-unit-tests  |     Focuses:  performance
--------------------------------------+--------------------------

Comment (by FolioVision):

 Replying to [comment:31 peterwilsoncc]:
 > Good catch, I've added it in to the dropdown in my PR.

 Thank you for the follow up.

 I tested the new version of your branch: https://github.com/peterwilsoncc
 /wordpress-develop/tree/try/58368-comment-count-no-orderby


 With standard WordPress the query responsible for the comment type drop
 down:


 {{{
 SELECT wp_5_comments.comment_ID
 FROM wp_5_comments
 WHERE ( ( comment_approved = '0'
 OR comment_approved = '1' ) )
 AND comment_type IN ('pingback', 'trackback')
 ORDER BY wp_5_comments.comment_date_gmt DESC
 LIMIT 0,1
 }}}

 Would take 7.28 seconds on average.

 With the new improved code the query would look like this:

 {{{
 SELECT wp_5_comments.comment_ID
 FROM wp_5_comments
 WHERE ( ( comment_approved = '0'
 OR comment_approved = '1' ) )
 AND comment_type IN ('pingback', 'trackback')
 LIMIT 0,1
 }}}

 But strangely it would take 8.68 seconds.

 As I explained in our ticket the `comment_type` **index** is what really
 helps: #58488

 With that index the query would take 0.3 miliseconds on average.

 Each test was repeated 4 times and I would go from the original code to
 the new branch and then back and run more tests to ensure the numbers are
 not affected by something else.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/58368#comment:32>
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