PostgreSQL get nested rows with limit - postgresql

Question

I got a self referencing table that's only 1 deep: comments and replies. A reply is just a comment with a parent id:
Comments (simplified):
- comment_id
- parentCommentId
Users have to scroll through the comments and replies and typically 10 new rows are being fetched each time, I'm trying out an recursive query for this:
WITH RECURSIVE included_childs(comment_id, parent_comment_id) AS
(SELECT comment_id, parent_comment_id
FROM comments
UNION
SELECT c.comment_id, c.parent_comment_id
FROM included_childs ch, comments c
WHERE c.comment_id = ch.parent_comment_id
)
SELECT *
FROM included_childs
limit 10
obviously because of limit 10 not all the childs are being included this way and conversations will be cut off. What I actually want is a limit on the parents and have all childs included, regardless of how many total rows.
update
This is the actual query, now with limit in the first branch:
WITH RECURSIVE included_childs(comment_id, from_user_id, fk_topic_id, comment_text, parent_comment_id, created) AS
((SELECT comment_id, from_user_id, fk_topic_id, comment_text, parent_comment_id, created
FROM vw_comments WHERE fk_topic_id = 2
and parent_comment_id is null
limit 1)
union all
SELECT c.comment_id, c.from_user_id, c.fk_topic_id, c.comment_text, c.parent_comment_id, c.created
FROM included_childs ch, vw_comments c
WHERE c.comment_id = ch.parent_comment_id
)
SELECT *
FROM included_childs
still, this doesn't give me the expected results, I get 1 comment as a result with no replies.
update 2
silly mistake on the where clause:
WHERE c.comment_id = ch.parent_comment_id
should've been
WHERE ch.comment_id = c.parent_comment_id
it's working now.

Answer 1

I think the first branch in the UNION in the recursive CTE should be something like:
SELECT comment_id, parent_comment_id
FROM comments
WHERE parent_comment_id IS NULL
LIMIT 10
Then you'd get all replies for these 10 "root" comments.
I'd expect some sort of ORDER BY in there, unless you don't care for the order.
UNION ALL would be fester than UNION, and there cannot be cycles, right?