I am using Neo4j 5.9.0 community
Problem description : My graph only has one type of relationship [:Relationship], and one type of node (:Node). I want to find the shortest path between two nodes, but I do not want the shortest path returned to contain this pattern : (:Node)<-[:Relationship]-(:Node)-[:Relationship]->(:Node)
I have read here that
If the MATCH clause of the shortestPath function includes a WHERE clause, a shortest path that satisfies the WHERE clause conditions is returned if one exists.
so this should be possible, and I have tested without using the shortestPath function that paths that verify this requirement indeed exist in my graph.
What I have tried: I have tested mutliple ways to filter the shortest path returned, but none of them were successful. I tried using the exists{} subquery:
match p = shortestPath((startNode:Node {id : 1})-[:Relationship*]-(endNode:Node {id : 2}))
where none(pathNode in nodes(p) where exists{
match (n1:Node)<-[:Relationship]-(pathNode)-[:Relationship]->(n2:Node)
where ((n1 in nodes(p)) and (n2 in nodes(p)))
})
return p
which returns 'Unknown expression type during transformation (class org.neo4j.cypher.internal.ir.ast.ExistsIRExpression)',
as well as using isEmpty() predicate function :
match p = shortestPath((startNode:Node {id : 1})-[:Relationship*]-(endNode:Node {id : 2}))
where isEmpty ([(n1)<-[:Relationship]-(n2)-[:Relationship]->(n3) where ((n1 in nodes(p)) and (n2 in nodes(p)) and (n3 in nodes(p))) | n2.id])
return p
which returns 'Unknown expression type during transformation (class org.neo4j.cypher.internal.ir.ast.ListIRExpression)'
I do not understand why the queries above do not work properly. Any help would be appreciated, thank you.
After explaining the problem on the Neo4j GitHub, the Neo4j team addressed this bug and declared that it has been fixed in the 5.15 release. I have not personally verified nor tested this.