Returing the most current league in cypher

StackOverflow https://stackoverflow.com/questions/17097341

Question

I've the League node entity as below

@NodeEntity
class League
{
  private Date startDate;
}

I want to return the most recent league for which the below cypher is working fine when executed from the shell

START n=node(*) WHERE has(n.__type__) and n.__type__='com.aravind.avl.domain.League' RETURN n ORDER BY n.startDate ASC LIMIT 1

I moved this to repository as below

public interface LeagueRepository extends GraphRepository<League>
{
    @Query ("START n=node(*) RETURN n ORDER BY n.startDate DESC LIMIT 1")
    League findCurrentLeague();
}

It is giving me the below error. I believe we no need to provide the spring-data-neo4j implementation details like __type__ when using the repositories. Wondering how to correctly write the query in repository without exposing the spring-data-neo4j implementation details?

JUNIT

@Test
    public void findCurrentLeague() throws ParseException
    {
        SimpleDateFormat df = new SimpleDateFormat("dd/MM/yyyy");

        League l1 = new League();
        l1.setStartDate(df.parse("01/03/2013"));
        l1.setEndDate(new Date());
        l1.setName("in year 2013");

        League l2 = new League();
        l2.setStartDate(df.parse("01/03/2001"));
        l2.setEndDate(df.parse("01/10/2001"));
        l2.setName("in year 2001");

        repo.save(l1);
        repo.save(l2);

        League currentLeague = repo.findCurrentLeague();
        assertNotNull(currentLeague);
        assertEquals("in year 2013", currentLeague.getName());
    }

Error

Caused by: org.springframework.dao.InvalidDataAccessResourceUsageException: Error executing statement START n=node(*) RETURN n ORDER BY n.startDate DESC LIMIT 1; nested exception is org.neo4j.cypher.EntityNotFoundException: The property 'startDate' does not exist on Node[0]
    at org.springframework.data.neo4j.support.query.CypherQueryEngine.parseAndExecuteQuery(CypherQueryEngine.java:63)
    at org.springframework.data.neo4j.support.query.CypherQueryEngine.query(CypherQueryEngine.java:49)
    ... 39 more
Caused by: org.neo4j.cypher.EntityNotFoundException: The property 'startDate' does not exist on Node[0]
    at org.neo4j.cypher.internal.commands.expressions.Property.apply(Property.scala:35)
    at org.neo4j.cypher.internal.commands.expressions.Property.apply(Property.scala:29)
    at org.neo4j.cypher.internal.pipes.ExtractPipe$$anonfun$createResults$1$$anonfun$apply$1.apply(ExtractPipe.scala:37)
    at org.neo4j.cypher.internal.pipes.ExtractPipe$$anonfun$createResults$1$$anonfun$apply$1.apply(ExtractPipe.scala:35)
    at scala.collection.immutable.Map$Map1.foreach(Map.scala:118)
    at org.neo4j.cypher.internal.pipes.ExtractPipe$$anonfun$createResults$1.apply(ExtractPipe.scala:35)
    at org.neo4j.cypher.internal.pipes.ExtractPipe$$anonfun$createResults$1.apply(ExtractPipe.scala:34)
    at scala.collection.Iterator$$anon$19.next(Iterator.scala:335)
    at org.neo4j.cypher.internal.pipes.TopPipe.createResults(TopPipe.scala:45)
    at org.neo4j.cypher.internal.pipes.ColumnFilterPipe.createResults(ColumnFilterPipe.scala:37)
    at org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl$$anonfun$6.apply(ExecutionPlanImpl.scala:127)
    at org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl$$anonfun$6.apply(ExecutionPlanImpl.scala:125)
    at org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl.execute(ExecutionPlanImpl.scala:33)
    at org.neo4j.cypher.ExecutionEngine.execute(ExecutionEngine.scala:59)
    at org.neo4j.cypher.ExecutionEngine.execute(ExecutionEngine.scala:63)
    at org.neo4j.cypher.javacompat.ExecutionEngine.execute(ExecutionEngine.java:79)
    at org.springframework.data.neo4j.support.query.CypherQueryEngine.parseAndExecuteQuery(CypherQueryEngine.java:61)
    ... 40 more
Caused by: org.neo4j.graphdb.NotFoundException: 'startDate' property not found for NodeImpl#0.
Was it helpful?

Solution

Also, the SDN entities, if they contain indexed properties, there should be indexes for these, which let's you target these nodes:

START n=node:League("name:*") RETURN n ORDER BY n.startDate? DESC LIMIT 1

HTH

OTHER TIPS

Do you have the property startDate on every node? The exception indicates:

Caused by: org.neo4j.cypher.EntityNotFoundException: The property 'startDate' does not exist on Node[0]
    at org.neo4j.cypher.internal.commands.expressions.Property.apply(Property.scala:35)

and it looks like it's complaining about the reference node.

Since you're starting at all nodes using node(*) it's probably picking up the reference node. If you don't need it then you might be able to get rid of it, or, if you don't have startDate anyway on all nodes, maybe modify your query to:

START n=node(*) RETURN n ORDER BY n.startDate? DESC LIMIT 1
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