[wp-trac] [WordPress Trac] #42566: When I use wp_nav_menu I get a huge update_meta_cache query regardless of theme

[WordPress Trac]

#42566: When I use wp_nav_menu I get a huge update_meta_cache query regardless of
theme
--------------------------+-----------------------------
 Reporter:  andyseaton83  |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Menus         |    Version:  4.8.3
 Severity:  normal        |   Keywords:
  Focuses:                |
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 Hi there,

 I've got a wordpress site that's been up and running for a couple of years
 now. I always keep core+plugins up to date, and although I use a custom
 theme, I'm pretty happy with how it's working.

 Recently however it started to crash regularly - and the server guys
 notified me that it was mysql that was causing it. So I installed Query
 Monitor and took a look - there was a massive query which looked like
 this:


 {{{
 SELECT post_id, meta_key, meta_value
 FROM ajs_postmeta
 WHERE post_id IN (11178,9677,9060,7417,7354, <lots more ids>)
 ORDER BY meta_id ASC
 }}}


 This was returning 20,000 rows each time the page was loading. This
 obviously overloaded the server during peak times and it needed rebooting.

 This is the code that was causing the problem (I know this because I
 replaced it and the offending query disappeared)

 {{{#!php
 <?php
 $header_menu_query = wp_nav_menu(array(
                      'theme_location' => 'header-menu',
                      'container' => 'nav',
                      'container_class' => 'nav-menu-holder nav-menu-
 landing nav-new',
                      'menu_class' => 'nav-menu',
                      'walker' => new themeslug_walker_nav_menu));
 }}}


 So I replaced wp_nav_menu with static HTML and the query size reduced as
 it was no longer calling wp_nav_menu. I thought it might have been
 something I'd done in my theme - so I removed the custom walker, which
 didn't have any effect, and played about with some settings. I tried using
 the recommendation here: [https://hitchhackerguide.com/2011/11/01
 /reducing-postmeta-queries-with-update_meta_cache]/ but that had no
 effect.

 So the next step was to try a different menu. So I deleted my menu (which
 had 70/80 items in it) and added 5 new items to a new menu. That then gave
 the following query:



 {{{
 SELECT post_id, meta_key, meta_value
 FROM ajs_postmeta
 WHERE post_id IN (11178,9677,9060,7417,7354)
 ORDER BY meta_id ASC
 }}}


 which is the same query as above but without the lots of additional ids -
 as this menu only had 5 items. This returned around 450 rows - so it's not
 hard to see that a menu with 70/80 items would get up to 20,000.

 The last thing I tried was to change to the default theme and disable all
 plugins (bar Query Monitor) and tried again. I associated my test menu
 (with the 5 items) with the 2017 theme top menu and checked query monitor
 - it still showed this query:

 {{{
 SELECT post_id, meta_key, meta_value
 FROM ajs_postmeta
 WHERE post_id IN (11178,9677,9060,7417,7354)
 ORDER BY meta_id ASC
 }}}

 with the same number of rows.

 So my question is this - is this something that is a problem in core
 wordpress, seeing as this update_meta_cache() method seems to be creating
 massive queries if you have a larger than average menu - even 15/20 items
 would create a fairly large result set each time.

 I've been googling like crazy as I really want to get this sorted - but I
 can't seem to find a solution, and I'm wondering if it's something in the
 latest release. There's no difference between browser or OS that I can see
 - its just something wrong (I think) with the update_meta_cache method as
 it relates to the wp_nav_menu function.

 Anyway, happy for you to take a look at my config etc - let me know what
 you need. Best email to get me on is andy at weboptimize.co.uk or you can
 call my UK mobile on 07791-107755

 Thanks

 Andy

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Ticket URL: <https://core.trac.wordpress.org/ticket/42566>
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