CODEWITHSUNDEEP
neo4jcypher
jrizzo
jrizzo

Reputation: 68

Cypher query to find circular reference

Given the example found here: http://console.neo4j.org/?id=qzjrxu, how would I identify nodes with relationships that end back to the starting node?

IE: joe -> bill -> tom -> joe AND matt -> matt

Thanks for the help.

Upvotes: 4

Views: 2379

Answers (2)

NiklasUllmann
NiklasUllmann

Reputation: 77

Depending on your problem and size of your graph you could try apoc.nodes.cycles from the apoc extension.

Documentation of that function

With that you could run something like:

MATCH (e)
WITH collect(e) AS e_list
CALL apoc.nodes.cycles(e_list, {relTypes: ['XYZ'], maxDepth: 100}) 
YIELD path RETURN path

It is better to reduce the number of nodes beforehand by filtering etc., especially with a large database.

Upvotes: 0

InverseFalcon
InverseFalcon

Reputation: 30417

For small to medium graphs, this should return nodes suffering from a circular reference and the path itself:

MATCH (e)
WHERE SIZE((e)<-[:ManagedBy]-()) <> 0 
AND SIZE(()<-[:ManagedBy]-(e)) <> 0
MATCH path = (e)<-[:ManagedBy*]-(e) 
RETURN e, path

EDIT

I made a small change to first filter out nodes which do not have incoming and outgoing :ManagedBy relationships, those will never have a cycle.

Also it's highly recommended to use labels to reduce the nodes processed to the smallest set.

Upvotes: 4

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