Getting top n records for each group in neo4j

Question

I need to group the data from a neo4j database and then to filter out everything except the top n records of every group.

Example:

I have two node

Answer 1

Try

MATCH (o:Order)-[r:ADDED]->(a:Article)
WITH o, r, a
ORDER BY o.oid, r.t
WITH o, COLLECT(a)[..2] AS topArticlesByOrder UNWIND topArticlesByOrder AS a
RETURN a.aid AS articleId, COUNT(*) AS count

Results look like

articleId    count
   8           6
   2           2
   4           5
   7           2
   3           3
   6           5
   0           7

on this sample graph created with

FOREACH(opar IN RANGE(1,15) |
    MERGE (o:Order {oid:opar})
    FOREACH(apar IN RANGE(1,5) |
        MERGE (a:Article {aid:TOINT(RAND()*10)})
        CREATE o-[:ADDED {t:timestamp() - TOINT(RAND()*1000)}]->a
    )
)