How do I set relationship data as properties on a node?

I've taken the leap from SQL to Neo4j. I have a few complicated relationships that I need to set as properties on nodes as the first step towards building a recommendation engine.

This Cypher query returns a list of categories and weights.

MATCH (m:Movie {name: "The Matrix"})<-[:TAKEN_FROM]-(i:Image)-[r:CLASSIFIED_AS]->(c:Category) RETURN c.name, avg(r.weight)

This returns

{ "fighting": 0.334, "looking moody": 0.250, "lying down": 0.237 }

How do I set these results as key value pairs on the parent node?

The desired outcome is this:

(m:Movie { "name": "The Matrix", "fighting": 0.334, "looking moody": 0.250, "lying down": 0.237 })

Also, I assume I should process my (m:Movie) nodes in batches so what is the best way of accomplishing this?

Solution

Not quite sure how you're getting that output, that return shouldn't be returning both of them as key value pairs. Instead I would expect something like: {"c.name":"fighting", "avg(r.weight)":0.334}, with separate records for each pair.

You may need APOC procedures for this, as you need a means to set the property key to the value of the category name. That's a bit tricky, but you can do this by creating a map from the collected pairs, then use SET with += to update the relevant properties:

MATCH (m:Movie {name: "The Matrix"})<-[:TAKEN_FROM]-(:Image)-[r:CLASSIFIED_AS]->(c:Category) 
WITH m, c.name as name, avg(r.weight) as weight
WITH m, collect([name, weight]) as category
WITH m, apoc.map.fromPairs(category) as categories
SET m += categories

As far as batching goes, take a look at apoc.periodic.iterate(), it will allow you to iterate on the streamed results of the outer query and execute the inner query on batches of the stream:

CALL apoc.periodic.iterate(
 "MATCH (m:Movie)
 RETURN m",
 "MATCH (m)<-[:TAKEN_FROM]-(:Image)-[r:CLASSIFIED_AS]->(c:Category) 
  WITH m, c.name as name, avg(r.weight) as weight
  WITH m, collect([name, weight]) as category
  WITH m, apoc.map.fromPairs(category) as categories
  SET m += categories",
{iterateList:true, parallel:false}) YIELD total, batches, errorMessages
RETURN total, batches, errorMessages