How to paginate intermediate nodes

Neo4j Graph Platform Cypher
1

Hi, thanks in advance for all the help offered at this community, it's really helpful.

I couldn't quite understand what's happening with the situation below.
Say there's a test data like this. Users can 'like' a certain project.

CREATE
(a:User),(b:User),(c:User),(p1:Project{id:1}),(p2:Project{id:2}),(p3:Project{id:3}),
(a)-[:LIKED]->(p3),(b)-[:LIKED]->(p3),(c)-[:LIKED]->(p3),
(a)-[:LIKED]->(p2),(b)-[:LIKED]->(p2)

I would like to get projects in order of liked counts. This is the query I wrote:

MATCH (p:Project)
OPTIONAL MATCH (p)-[l:LIKED]-(:User)
WITH count(l) as likedCount, p ORDER BY likedCount DESC
// perform some expensive task on p
RETURN p.id, likedCount

Now, since I am performing some expensive task with p,
I want to limit the number of projects to work on, with something like this.

MATCH (p:Project)
OPTIONAL MATCH (p)-[l:LIKED]-(:User)
WITH count(l) as likedCount, p ORDER BY likedCount DESC
WITH collect(p)[0..3] as projects, likedCount
UNWIND projects as p
// perform expensive task, but only to limited projects
RETURN p.id, likedCount

The result:

p.id	likedCount
3	3
2	2
1	0

To paginate, for example excluding the most liked project, I would change [0..3] to [1..3] as such:

MATCH (p:Project)
OPTIONAL MATCH (p)-[l:LIKED]-(:User)
WITH count(l) as likedCount, p ORDER BY likedCount DESC
WITH collect(p)[1..3] as projects, likedCount
UNWIND projects as p
RETURN p.id, likedCount

Now I get this:

(no changes, no records)

Instead of getting 2 project rows, why did I get 0?

2

Hi Dowanna,

count() aggregation function will be automatically grouped.
So Please change "(p)[1..3]" to "SKIP 1 LIMIT 3"

MATCH (p:Project)
OPTIONAL MATCH (p)-[l:LIKED]-(:User)
WITH count(l) as likedCount, p
  ORDER BY likedCount DESC SKIP 1 LIMIT 3
RETURN p.id, likedCount