Using unwind in a call with cypherdsl

Drivers & Stacks Spring Data Neo4j & Neo4j-OGM
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1

I have a cypher query and want to catch related nodes for each node in the result.
So my working raw cypher query looks like :

MATCH p = (:lookingType)<-[:specifiedRelation]-()
WITH nodes(p) AS nodes, relationships(p) AS relations
CALL {
 WITH nodes
 UNWIND nodes AS n
 MATCH second_p=(n)-[second_relations:otherRelation]->(second_nodes)
 RETURN second_nodes, second_relations
}
RETURN nodes, relations, collect(second_nodes), collect(second_relations)

In my java project, I want to use cypherdsl for this.
But, I have a problem using a Unwind inside a call. That's what I try :

OngoingReading imports = Cypher.unwind(Functions.nodes(first_path)).as("n");
Statement completeStatement = Cypher.match(first_path)
   .call(second_path,
       imports)
   .returning(nodes, relations, second_nodes, second_relations)
   .build();

But call doesn't manage OngoingReading objects. Is there any turn around?
As it is a common use case in my project, using only one query to the database is important.
I fail with multiple other ways. Thank you for reading and for your help.

2

Hi @paulB that whould be something like that:

SymbolicName nodes = Cypher.name("nodes");
		SymbolicName relations = Cypher.name("relations");
		SymbolicName second_nodes = Cypher.name("second_nodes");
		SymbolicName second_relations = Cypher.name("second_relations");

		NamedPath first_path = Cypher.path("p")
			.definedBy(
				Cypher.node("lookingType").relationshipFrom(Cypher.anyNode(), "specifiedRelation")
			);
		NamedPath second_path = Cypher.path("second_p")
			.definedBy(
				Cypher.anyNode("n")
					.relationshipTo(Cypher.anyNode().named(second_nodes), "otherRelation")
					.named(second_relations)
			);

		Statement inner = Cypher.unwind(nodes).as("n").with("n")
				.match(second_path)
				.returning(second_nodes, second_relations)
				.build();

		Statement completeStatement =
			Cypher
				.match(first_path)
				.with(Functions.nodes(first_path).as(nodes), Functions.relationships(first_path).as(relations))
				.call(inner, nodes.as("nodes"))
				.returning(nodes, relations, Functions.collect(second_nodes), Functions.collect(second_relations))
			.build();

which gives you

MATCH p = (:lookingType)<-[:specifiedRelation]-()
WITH nodes(p) AS nodes, relationships(p) AS relations
CALL {
  WITH nodes
  WITH nodes AS nodes
  UNWIND nodes AS n
  WITH n
  MATCH second_p = (n)-[second_relations:otherRelation]->(second_nodes)
  RETURN second_nodes, second_relations
}
RETURN nodes, relations, collect(second_nodes), collect(second_relations)

the 2nd with is ugly and is caused by that Call {} inner creates empty with when using an unnamed import. · Issue #319 · neo4j-contrib/cypher-dsl · GitHub, which I will fix soon.

3

Hi @michael_simons1,

Thank you so much for your help.
I was doing something quite ugly with some CypherParser, thank god, you came in!
With this use case, I have a new point of view on the convenient SymbolicName.

Thank for your time and your work.

1 Like
4

My pleasure! Your contribution helped me to discover the rendering bug (which was fixed, release will be done probably next week).