get_blog_post() and get_blog_permalink() create duplicate caches that aren't invalidated

[ryan]

Both of these copy per blog information to global caches and never invalidate that information when the sources change.

[nacin]

get_blog_post() should also use switch_to_blog() like get_blog_permalink().

Persistent caching that we get via switch_to_blog() should be enough, no? The double-caching seems weird.

[ryan]

Actually, global-posts is invalidated at the end of clean_post_cache() so get_blog_post() isn't as bad as it first seemed.

[nacin]

Replying to ryan:

Actually, global-posts is invalidated at the end of clean_post_cache() so get_blog_post() isn't as bad as it first seemed.

We can kill that line now, though. 21595.diff​ looks good.

[ryan]

That removes the invalidation. Those rare third parties who might be relying on that invalidation would have to perform the invalidation themselves on a clean_post_cache hook. I left the registration of global-posts as a global group in for now.

[ryan]

​[UT990]

[ryan]

In [21628]:

Use switch_to_blog()/restore_current_blog() in get_blog_post() and get_blog_permalink(). Eliminate the duplicate caching in these functions. Return WP_Post from get_blog_post(). Update phpdoc. Remove global-posts cache invalidation. Props jondavidjohn fixes #21595

[ryan]

​[UT992]

[nacin]

#19420 was marked as a duplicate.