remove_ancestor_topics.sql

select
	child_link_id,
	child_topic_id,
	parent_link_id,
	parent_topic_id,
	child_path,
	parent_path
	from (
		select
			lt_child.link_id as child_link_id,
			lt_child.topic_id as child_topic_id,
			l_child.path as child_path,
			lt_parent.link_id as child_link_id,
			lt_parent.topic_id as parent_topic_id,
			l_parent.path as parent_path
		from
			links_topics as lt_child
			inner join topics as t_child on t_child.id = lt_child.topic_id
			inner join topics as t_parent on t_parent.id = lt_parent.topic_id
			inner join links_topics as lt_parent on lt_child.link_id = lt_parent.link_id and t_parent.path @> t_child.path
			
	) as sub;

single.sql

select
	lt.link_id,
	lt.topic_id
	from links_topics as lt
	where lt.link_id in (select link_id from links_topics where links_topics.topic_id = 52)
	and lt.topic_id in (
		select t.id
			from topics as t
			inner join topics as t_b on t.path @> subpath(t_b.path, 0, nlevel(t_b.path) - 1) where t_b.id = 52
	);