How to get comments for each post in the list?

Question

MySQL

Hello! I display a list of posts and I want to get the last 3 comments for each. How can this be done with less resources? Here's the principle:

After all, if you get a list of posts, and then request from the database for each comment, then when you display 50 posts, you get an additional 50 queries to the database.

Answer 1

1. Get posts (1 request if you don't pull and prime caches of metadata and taxonomies).
2. Pull out their IDs from the array of posts (wp_list_pluck or a similar method).
3. Get comments using WP_Comment_Query by passing the IDs from step 2 to the post__in property (1 request, if you do not pull and prime caches of metadata and posts)
4. Display posts in a cycle, in each iteration, take the necessary comments from the result of step 3
Total : 2 requests.
However, in real life, you still need metadata for both posts and comments. Therefore, there will be more requests, but not N + 1.
In general, it would not hurt to cache such things in their entirety, or at least the results of queries, in transients. For how long - depends on the frequency of updating information on the site. From 5 minutes to an hour.