Prime caches for featured images in post rest api controller

[spacedmonkey]

In the post api controller, if the post type supports thumbnails, this results a query to be run for each post's thumbnail. For a REST API request with 100 posts in it, this can result in lots of queries. In core there is already a function called update_post_thumbnail_cache, used to prime post thumbnails. However, this does not seem to be fired here. A simple fix would be to fire update_post_thumbnail_cache in the post controller.

Trac ticket: https://core.trac.wordpress.org/ticket/55592

[TimothyBlynJacobs]

Great find.

[spacedmonkey]

@TimothyBlynJacobs Have added a unit tests. Are you happy for me to commit?

[TimothyBlynJacobs]

Go for it.

[spacedmonkey]

In 53499:

REST API: Prime caches for featured images in post controller.

Ensure that featured image caches are primed for post collections in the post REST API controller, by calling the update_post_thumbnail_cache function.

Props Spacedmonkey, TimothyBlynJacobs, mitogh.
Fixes #55592.

Committed in https://core.trac.wordpress.org/changeset/53499

[desrosj]

There are a lot of caching related changes in 6.1 and a dev note should be written collecting them all. Marking this for inclusion.

[spacedmonkey]

Early draft of a dev note can be found ​here.

[milana_cap]

Dev note: ​https://make.wordpress.org/core/2022/10/10/performance-improvements-to-the-rest-api/