Find max depth with bidiretional graph

Question

using neo4j I'm trying to find max depth in this graph:

Using this query I find deph value 20 (because I have this bidirectional relationship):

MATCH p=(u:User)-[:Amico*]->(f:User)
RETURN p, length(p) order by length(p) desc limit 1

How can I have the true value of this depth?

Does this answer your question? [How do find the longest path in a cyclic Graph between two nodes?](https://stackoverflow.com/questions/2679081/how-do-find-the-longest-path-in-a-cyclic-graph-between-two-nodes) — dbl, Oct 18 '20 at 10:53
It's a good Idea, But I don't know how to write it in Cypher. — Francesco Bocci, Oct 18 '20 at 11:08
Either way my initial comment was to use `dfs`, yet `bfs` was used in the accepted answer from the thread above. [docs DFS tutorial](https://neo4j.com/docs/graph-data-science/current/algorithms/dfs/) && [docs BFS tutorial docs](https://neo4j.com/docs/graph-data-science/current/algorithms/bfs/) — dbl, Oct 18 '20 at 11:36
Yet [another link](https://neo4j.com/developer/kb/achieving-longestpath-using-cypher/) from their docs that seems related. — dbl, Oct 18 '20 at 11:42
By the way, Neo4j can traverse a relationship in either direction equally efficiently. If 2 relationships in opposite directions are always paired together, that implies a bad data model (which requires unnecessary storage overhead and overly-complex code-- as you are seeing). For more info, see the Note at the bottom of [this answer](https://stackoverflow.com/a/60645114/974731). If you only had a single relationship between every pair of nodes, your original query (except with an undirected relationship) should have worked. — cybersam, Oct 19 '20 at 18:44

score 1 · Accepted Answer · answered Oct 18 '20 at 20:45

I guess you could solve it by only considering paths in which each node only appears once. Neo4j's apoc library offers a function for that:

MATCH p=(u:User)-[:Amico*]->(f:User)
WHERE NOT apoc.coll.containsDuplicates(nodes(p))
RETURN p, length(p) order by length(p) desc limit 1

1 Answers1