[FIXED] Could not find mappable nodes or relationships inside Record

Issue

I want to return aggregate count along with the main attributes using SDN OGM.

This is my data in Neo4j

{
  "identity": 777777,
  "labels": [
    "RootMarker"
  ],
  "properties": {
"lastModifiedDate": 1666934940115,
"p5Latest": true,
"messageIds": [
      "fake-900b-49ac-92c7-fake",
      "fake-fd73-4058-b07b-fake"
    ],
"messageId": "fake-fd73-4058-b07b-fake",
"deviceId": "XXXXX",
"domainId": "fake-35d5-11ed-9299-fake",
"resources": 1,
"createdDate": 1666896513598,
"drniId": 111111111111,
"isFull": true,
"resyncId": "fake-46d3-4ab1-bf34-fake",
"status": "resync",
"latest": [
      22
    ]
  }
}

My Repo

public interface StackOverFlowRepository extends Neo4jRepository<RootMarkerDTO, Long> {

    @Query("MATCH (n:RootMarker {current: true}) RETURN n.domainId as domainId, count(n.domainId) as count ORDER BY n.domainId")
    List<TestProjections> getRootMarker();
    
}

My main objective is return attributes as well this count(n.domainId) as count

Both here below works

@Query("MATCH (n:RootMarker {current: true}) RETURN count(n.domainId) as count ORDER BY n.domainId")
Long itWorks1();

@Query("MATCH (n:RootMarker {current: true}) RETURN n.domainId as domainId ORDER BY n.domainId")
List<RootMarkerDTO> itWorks2();

RootMarkerDTO:

@Node(labels = "RootMarker")
@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
public class RootMarkerDTO{

    @Id @GeneratedValue
    private Long id;

    private String domainId;
    private String resyncId;
    private String status;
    private String deviceId;
}

This here do NOT work

@Node(labels = "RootMarker")
@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
public class RootMarkerDTO{

    @Id @GeneratedValue
    private Long id;

    private String domainId;
    private String resyncId;
    private String status;
    private String deviceId;
    
    //Here
    private Long count;
}

TestProjections

import lombok.Value;

@Value
public class TestProjections {
    String domainId;
    Long count;
}

Error:

org.springframework.data.neo4j.core.mapping.NoRootNodeMappingException: Could not find mappable nodes or relationships inside Record<{domainId: "78d89740-35d5-11ed-9299-d5f548819a2b", count: 280}> for org.springframework.data.neo4j.core.mapping.DefaultNeo4jPersistentEntity@6d2db15b

I missing something really important about SDN understanding. Any help is appreciated.

EDIT:

I have created this completed replicable setup.

https://github.com/goldman7911/spring-data-understanding

MyRepository there is a method customCount() with a more realistic scenario.

//THAT'S NOT WORKING
@Query("match (r:RootMarker) UNWIND r.messageIds as rx return r.resyncId as resyncId, count(rx) as counter")
List<MyDTO> customCount();

That's is the same return from Neo4j

And the error:

org.springframework.data.neo4j.core.mapping.NoRootNodeMappingException: Could not find mappable nodes or relationships inside Record<{resyncId: "fake-7777-4ab1-7777-fake", counter: 4}> for org.springframework.data.neo4j.core.mapping.DefaultNeo4jPersistentEntity@7fc420b8

EDIT2:

Following @meistermeier propose it works. I just do not understand why upper SDN layers can't handle it. What exactly is not capable of understand that.

public Collection<MyDTO> getRootMarkerByNeo4jClient() throws NoSuchElementException {
        Collection<MyDTO> result = neo4jClient.query("match (r:RootMarker) UNWIND r.messageIds as rx return r.resyncId as resyncId, count(rx) as counter")
                .fetchAs(MyDTO.class)
                .mappedBy((typeSystem, record) -> {
                    String resyncId = record.get("resyncId").asString();
                    Long counter = record.get("counter").asLong();
                    return new MyDTO(resyncId, counter);
                }).all();
        return result;
    }

Solution

A projection in Spring Data Neo4j always refers to an entity. So adding e.g. the count to it, will create a bunch of arbitrary properties.

This is something that SDN does not consider matching for the type of the repository or its projections. For this cases I recommend to use the Neo4jClient with the custom query and create the instance of the (non-)projection yourself.

neo4jClient.query("<your query>")
    .fetchAs(TestProjections.class)
    .mappedBy((typeSystem, record) -> {
        Long domainId = record.get("domainId").asLong();
        Long count = record.get("count").asLong();
        return new TestProjections(domainId, count);
    });

Answered By - meistermeier
Answer Checked By - Dawn Plyler (JavaFixing Volunteer)