Suspend calling wp_cache_set_posts_last_changed() when touching post meta in WP_Sync_Post_Meta_Storage

[westonruter]

Trac ticket: https://core.trac.wordpress.org/ticket/64696

Use of AI Tools

Gemini CLI authored a commit to help add phpdoc for the with_suspended_posts_last_changed_update() method.

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[github-actions]

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[chriszarate]

I can't speak to whether this is the correct performance mitigation, but the code change looks good in the context of the sync provider. 👍 Thank you!

[mindctrl]

I'll try to confirm the level of accuracy of the screenshots included here to be sure there are no bugs in the way I'm tracking this, but here's a quick look at the difference before and after this PR:

Before

After

Edit: Note the before/after timestamps are opposite the way I've labeled them. This is due to running a 2nd check on the "before" run to double check my results.

I'm testing this with 3 Playwright clients making edits to the same post.

[westonruter]

@mindctrl it might be helpful to also have a client that is continuously doing reads to a function that uses wp_cache_get_last_changed( 'posts' ) as the salt for a return value that should be cached in object cache, to simulate the impact of having this on a live site getting a lot of traffic. This would be in a addition to having sync clients open. For example, get_archives() would continuously have its cache impacted by sync changes.

It seems like there are a lot of examples where unrelated post and post meta changes are causing object cache invalidations needlessly. (Cache invalidation is hard!)