[wp-trac] [WordPress Trac] #36904: Add caching to comment feed in WP_Query

[WordPress Trac]

#36904: Add caching to comment feed in WP_Query
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 Reporter:  spacedmonkey  |       Owner:
     Type:  enhancement   |      Status:  new
 Priority:  normal        |   Milestone:  Future Release
Component:  Query         |     Version:  2.2
 Severity:  normal        |  Resolution:
 Keywords:  needs-patch   |     Focuses:  performance
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Changes (by boonebgorges):

 * keywords:  needs-unit-tests has-patch => needs-patch


Comment:

 I've spent some time with the latest patch, and it seems to do pretty well
 with single-post comment feeds - example.com/2017/05/foo/comments/feed/.
 [attachment:36904.4.patch] is a slightly cleaned-up version, with an
 initial pass at a technique for having at least a tiny bit of test
 coverage.

 But the patch, as written, breaks the main comment feed:
 example.com/comments/feed/. This feed should fetch the latest 10 comments
 from all published posts (10 being the default posts_per_rss):

 {{{
 SELECT  wp_comments.* FROM wp_comments JOIN wp_posts ON (
 wp_comments.comment_post_ID = wp_posts.ID ) WHERE ( post_status =
 'publish' OR ( post_status = 'inherit' AND post_type = 'attachment' ) )
 AND comment_approved = '1'  ORDER BY comment_date_gmt DESC LIMIT 10
 }}}

 With [attachment:36904.4.patch], it fetches the last 10 comments *that
 belong to the last 10 posts*. Any comments from posts 11+ will not be
 included.

 @spacedmonkey Could you take this back to the drawing board a bit? It
 seems that removing the `// Comment feeds` block and doing all processing
 after the main posts query is responsible for this problem. It might turn
 out that we'll need to continue to do something in that part of the query
 generation, whether it's setting some sort of flag (it's not clear to me
 what that'd look like, but maybe you can figure it out) or just calling
 `WP_Comment_Query` in both places.

 If we get a version with everything working, it seems like a good call for
 4.9.

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Ticket URL: <https://core.trac.wordpress.org/ticket/36904#comment:9>
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