How to optimise recursive query - Neo4j?

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I am developing a contact tracing framework using Neo4j. There are 2 types of nodes, namely Person and Location. There exists a relationship VISITED between a Person and a Location, which has properties startTS and endTS. Example:

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Now suppose person 1 is infected. I need to find all the persons who have been in contact with this person. For each person identified, I need to find all other persons who have been in contact with that person. This process is repeated until an identified person has not met anyone. Here is a working code:

MATCH path = (infected:Person {id:'1'})-[*]-(otherPerson:Person)
WITH relationships(path) as rels, otherPerson
WHERE all(i in range(1, size(rels)-1)
  WHERE i % 2 = 0
  OR (rels[i].endTS >= rels[i-1].startTS AND rels[i].startTS <= rels[i-1].endTS)
)
RETURN otherPerson

The problem is that the process is taking way too much time to complete with large datasets. Can the above query be optimised? Thank you for your help.

cypher graph-databases neo4j
1 Answers

For this one, unfortunately, there are some limitations on our syntax for filtering these more complex conditions during expansion. We can cover post-expansion filtering, but you'd want an upper bound otherwise this won't perform well on a more complex graph.

To get what you need today (filtering during-expansion instead of after), you would need to implement a custom procedure in Java leveraging our traversal API, and then call the procedure in your Cypher query.

Advanced syntax that can cover these cases has already been proposed for GQL, and we definitely want that in Cypher. It's on our backlog.

user_923590
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