Neo4j / Cypher仅在谓词适用于所有关系时才匹配

Question

I need to match nodes only when every relationship the node has fullfills a whereclause:

MATCH (o:Otherthing)
WHERE id(o) = 1
MATCH (unknown:Thing)
WHERE (unknown)-[:DEPENDS_ON]->(:Thing)<-[:DEPENDS_ON*]-(:Thing)<-[:STARTED_WITH]-(o) 
RETURN unknown

Every matched "Thing" should only have relationships labeled with "DEPENDS_ON" and all of them should fullfill the condition.

How can I achieve that?

Answer 1

This may work for you:

MATCH (u:Thing)-[:DEPENDS_ON]->(:Thing)<-[:DEPENDS_ON*]-(:Thing)<-[:STARTED_WITH]-(o)
WHERE ID(o) = 1
WITH u, COUNT(*) AS num
WHERE SIZE((u)--()) = num
RETURN u

The query uses an efficient degreeness check to get the total number of relationships for u , and compares that with the number of times u satisfied the MATCH . Also, since you are identifying o by its native ID (which I am assuming is always going to be the ID for an Otherthing ), it is more efficient to not specify its label (to avoid a label verification operation).