GraphAcademy

Intermediate Cypher Queries

Filtering Queries

Controlling Results Returned

Working with Cypher Data

Graph Traversal

Pipelining Queries

Reducing Memory

Using Parameters

Relationships Traversed

Finding more co-actors

Actors in movies that Robert Blake acted in

Given this query and what you have learned about graph traversal:

cypher
MATCH (p:Person {name: 'Robert Blake'})-[:ACTED_IN]->(m:Movie)
MATCH (allActors:Person)-[:ACTED_IN]->(m)
RETURN m.title, collect(allActors.name)

How many relationships are traversed to return the result?

  • ✓ 20

Hint

The query finds each movie that Robert Blake acted in. How many ACTED_IN traversals is that?

For each movie, it uses a second MATCH to find all actors to acted in that movie. Because there are two MATCH clauses, it traverses the ACTED_IN relationship from Robert Blake twice.

How many ACTED_IN relationships are traversed?

Solution

This query traverses a total of 20 ACTED_IN relationships.

  1. It first traverses all ACTED_IN relationships from Robert Blake (4 traversals)

  2. For each movie found, it traverses all ACTED_IN relationships to tbe movie. (16 traversals, including the traversal from Robert Blake)

You can see the nodes and relationships involved, with this query:

cypher
MATCH (p:Person {name: 'Robert Blake'})-[:ACTED_IN]->(m:Movie)
MATCH (allActors:Person)-[:ACTED_IN]->(m)
RETURN p,m,allActors

Summary

In this challenge, you determined the number of relationships that are traversed during query.

In the next lesson, you will learn about traversal with variable-length paths in the graph.