[wp-trac] [WordPress Trac] #8071: Refrain from querying all the comments on a post when paged

[WordPress Trac]

#8071: Refrain from querying all the comments on a post when paged
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 Reporter:  markjaquith             |       Owner:  wonderboymusic
     Type:  enhancement             |      Status:  assigned
 Priority:  normal                  |   Milestone:  4.4
Component:  Comments                |     Version:  2.7
 Severity:  normal                  |  Resolution:
 Keywords:  has-patch dev-feedback  |     Focuses:
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Changes (by wonderboymusic):

 * keywords:  needs-patch => has-patch dev-feedback


Comment:

 [attachment:8071.diff 8071.diff] makes this work

 Create 2 helper functions (these can be renamed, whatever):
 * `wp_comments_per_page()` - figures out what the default per page value
 is
 * `wp_comment_pages_count( $total, $top_level )` - total can be read from
 `$post->comment_count`, `$top_level` is the count of a queried array of
 top level comment ids for a post that runs when comments are threaded

 Add 2 query vars to `WP_Comment_Query`:
 * `parent__in` - for querying for comment_IDs that belong to a set of
 parents
 * `parent__not_in` for completeness

 Add a new `orderby` value in `WP_Comment_Query`: `comment__in` - when
 querying by `comment__in`, need to return them in the same order.

 In `comment_template()`:
 - We're going to split the query - add `'fields' => 'ids'` to
 `$comment_args`
 - If comments are threaded, query for all of the top level comment ids -
 else, get all of the comment IDs
 - Figure out how many pages of comments there are using
 `wp_comment_pages_count()`
 - Save the number of pages on `$wp_query` as `->comment_pages_count`
 - If we determine that there is more than 1 page of comments:
   - save the current page on `$wp_query` as `->comment_pages_page`
   - slice the list of comment IDs based on `page` and `per_page`
   - if comments are threaded, use `parent__in` in
 `wp_threaded_comment_ids()` to query for comment children (1 query for
 comment IDs per depth level)
 - set `comment__in` to the comment IDs, orderby `comment__in`, get all of
 the comments in 1 query

 In `wp_list_comments()`:

 * If no comments are passed to the function (means we're in the loop) and
 `$wp_query->comment_pages_page` is set, reset `$r['page']` to 1, so that
 the Walker doesn't try to create the offset that we created by slicing the
 comment_IDs in `comments_template()`

 Any Comments? (Huzzah!)

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Ticket URL: <https://core.trac.wordpress.org/ticket/8071#comment:14>
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