CODEWITHSUNDEEP
loopsneo4jcyphergraph-databases
James
James

Reputation: 23

find loops in Neo4j

I am following this Course Graph Analytics With Neo4j to explore Neo4j database. The database is very simple, which contains 11 nodes ('A', 'B','C'...), 14 relationships. I want to find all loops within this Neo4j database. I have used this following query to find the loops containing 'A'.

match p=(n)-[*]-(m)
where n.Name = ['A'] and m.Name = ['A']
return EXTRACT(n IN NODES(p)| n.Name) AS Paths, length(p)
order by length(p)

The problem is that, within several loops generated from the above query, some nodes has been visited twice, like 'C' in the following loop: ["A", "C", "D", "B", "C", "J", "F", "A"].

Which Filter function I can use to eliminate this. Thank you,

Upvotes: 2

Views: 3856

Answers (1)

Bruno Peres
Bruno Peres

Reputation: 16375

I believe this query should work:

MATCH p=(n)-[*]-(m)
WHERE n.Name = ['A'] and m.Name = ['A']
AND NONE (node IN NODES(p) WHERE SIZE(
                FILTER(x IN NODES(p) WHERE node = x AND x.name <> 'A')
        ) > 1
    )
RETURN EXTRACT(n IN NODES(p)| n.Name) AS Paths, length(p)
order by length(p)

That is: the query uses the NONE(), SIZE() and FILTER() functions to guarantee that only paths without repeated nodes will be matched.

Based in this SO answer.

Upvotes: 1

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