[wp-trac] [WordPress Trac] #50567: Set $post filter in update_post_cache()

[WordPress Trac]

#50567: Set $post filter in update_post_cache()
-------------------------------+--------------------------
 Reporter:  Cybr               |       Owner:  (none)
     Type:  defect (bug)       |      Status:  new
 Priority:  normal             |   Milestone:  5.6
Component:  Posts, Post Types  |     Version:  trunk
 Severity:  normal             |  Resolution:
 Keywords:                     |     Focuses:  performance
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Comment (by Cybr):

 @peterwilsoncc asked me in Slack if I could post fuller screenshots
 (`50567.png`) pertaining to this ticket.

 Attached (`cg.zip`) are before and after CacheGrind outputs generated by
 xDebug on PHP 7.4.7 via XAMPP on a VM with generous overhead
 (16GB/4x3.8GHz).

 I've used Twenty Twenty with no plugins active on WP 5.4.2 en_US,
 displaying 20 posts (duplicated default post "Hello World!") at `/wp-
 admin/edit.php`, and 10 posts at `/` (homepage).

 To learn how to inspect the files, see https://xdebug.org/docs/profiler. I
 used [https://sourceforge.net/projects/qcachegrindwin/ QCacheGrind] to
 generate the attached screenshot.

 1 unit of Incl./Self/Time is equal to 1 microsecond (0.001ms).

 The attached screenshot shows the grind's output in this order:
 Home Before / Home After
 Admin Before / Admin After

 [[Image(https://core.trac.wordpress.org/raw-
 attachment/ticket/50567/50567.png)]]

 At the bottom-left of each window in the screenshots, you can see the
 Total Time Cost to generate the page. Since we can't use opcode caching
 during debugging, file inclusion takes up a generous amount of time. So,
 you can't calculate the relative performance impact of the improvements to
 the total page generation time. Nevertheless, you can measure a
 significant boost there, too.

 ||= =|| sanitize_post_field |||| Called |||| Microtime |||| Seconds ||
 Improvement ||
 ||= =|| Location || Before || After || Before || After || Before || After
 || =-1*((Af-Be)/Be) ||
 || (logged out) || / || 4 554 || 276 || 100 911 || 6 110 || 0.101 || 0.006
 || 94% ||
 || (logged in) || /wp-admin/edit.php || 12 443 || 483 || 272 566 || 10 372
 || 0.273 || 0.011 || 96% ||

 So, we can assume almost up to 0.3s improved response times using PHP 7.4,
 implying a total of 62% of the total page load time.

 You'll notice from the same CacheGrind files, `sanitize_term_field()` is
 also affected by this issue, where category ID 1 is resanitized over and
 over again. To accommodate for that, see #50568.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/50567#comment:3>
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