How to make pagination if there are child elements, can they be loaded separately?

Question

CodeIgniter

I ran into pagination, posts have child elements in the feed. You need to bring out 20 parents. The question is how to pull them out, because each has child elements. That is, you need a request to the database - to display 20 parents and all children. Can you tell me how to do it? Or maybe there are more beautiful options, for example, as in contact. But there, too, it is not clear to me personally, because child elements must also be taken into account.

Answer 1

Assemble the tree completely, then cut N elements from the beginning, taking into account sub elements.
How to split a tree into pages (PHP+MySQL)?