Node(ID) already exists with label X and properties y = 'z', a = 'b' on repository save with unicity

[fabienOuedraogo]

Hi the Team,

I got the error Node(ID) already exists with label Entity and properties prop1 = v1, prop2 = v2 when try trying to save an entity defined as:

class Entity {
  @Id
  @GeneratedValue
  private Long id;
  
  @RelationShip(type = "LINKED_TO")
  private List<LinkedEntity> linkedTo;

  @DynamicLabels
  private List<String> additionalLabels;
}

class LinkedEntity {
  @Id
  private String prop1;
  private Strint prop2;

   @DynamicLabels
  private List<String> additionalLabels;
}

I created an unicity constraint for LinkedEntity where prop1 and prop2 must be unique (ASSERT (n.prop1, n.prop2))

Now when a LinkedEntity already exists I get a Constraint violation exception when I try to create a new Entity linkedTo the existing LinkedEntity.

It seems Spring data Neo4j try to create the existing LinkedEntity again.

Is it possible to only create not existing nodes and the create the relationship?

[meistermeier]

Spring Data Neo4j won't create entities already existing in the database.
All save operation are using some kind of "MATCH first (on id), if nothing was found, CREATE"-logic.
I am wondering why the message mentions the Entity class and not the LinkedEntity class in ... with label Entity ...
Is it possible that you do have a saved node of the type Entity with the properties and now persist a LinkedEntity with the additional dynamic label :Entity?
If not, could you please provide a simple reproducer for the problem? I took the example from above and cannot reproduce it with e.g. something like:

Entity entity = new Entity();
LinkedEntity linkedEntity = new LinkedEntity();
linkedEntity.prop1 = "a";
linkedEntity.prop2 = "b";
entity.linkedTo = new ArrayList<>();
entity.linkedTo.add(linkedEntity);
// if we would have the same properties in Entity and would add this label, it could fail
// linkedEntity.additionalLabels.add("Entity");

repository.save(entity);

[fabienOuedraogo]

@meistermeier thank you for your response.

Here is what I did:

  @Override
  public Mono<Entity> save(String tenant, Entity entity) {
    return entityRepository.save(entity.toBuilder().tenant(tenant).build().withAdditionalLabel());
  }

When a want to create a new Entity linked to an existing LinkedEntity, I set the tenant property and add an additionalLabel which is "BU" concatenated to the tenant. The objectif is to get a new relation as :

(n:`Entity`:`BU15`) - [ r: LINKED_TO ]-> (p:`LinkedEntity`:`BU15` { code: 'TEST', tenant: '15') 

Please note that I have an unicity constraint on LinkedEntity code and tenant as we can get another LinkedEntity like (p:LinkedEntity:BU16 { code: 'TEST', tenant: '16')

2021-12-09 17:39:12.467 DEBUG 32340 --- [4jDriverIO-2-21] org.springframework.data.neo4j.cypher    : Executing:
MATCH (n) WHERE id(n) = $__id__ UNWIND labels(n) AS label WITH label WHERE NOT (label IN $__staticLabels__) RETURN collect(label) AS __nodeLabels__
2021-12-09 17:39:13.184 DEBUG 32340 --- [4jDriverIO-2-21] org.springframework.data.neo4j.cypher    : Executing:
OPTIONAL MATCH (hlp:`Entity`) WHERE id(hlp) = $__id__ WITH hlp WHERE hlp IS NULL CREATE (n:`Entity`) SET n = $__properties__ SET n:`BU15` RETURN id(n) UNION MATCH (n:`Entity`) WHERE id(n) = $__id__ SET n += $__properties__ SET n:`BU15` RETURN id(n)
2021-12-09 17:39:19.746 DEBUG 32340 --- [4jDriverIO-2-21] org.springframework.data.neo4j.cypher    : Executing:
MATCH (n) WHERE n.code = $__id__ UNWIND labels(n) AS label WITH label WHERE NOT (label IN $__staticLabels__) RETURN collect(label) AS __nodeLabels__
2021-12-09 17:40:30.504 DEBUG 32340 --- [4jDriverIO-2-21] org.springframework.data.neo4j.cypher    : Executing:
MERGE (n:`LinkedEntity` {code: $__id__}) SET n += $__properties__ REMOVE n:`BU15`:`BU16` SET n:`BU15` RETURN id(n)
2021-12-09 17:41:03.099 DEBUG 32340 --- [4jDriverIO-2-21] .d.n.c.t.ReactiveNeo4jTransactionManager : Participating transaction failed - marking existing transaction as rollback-only
2021-12-09 17:41:03.100 DEBUG 32340 --- [4jDriverIO-2-21] .d.n.c.t.ReactiveNeo4jTransactionManager : Participating transaction failed - marking existing transaction as rollback-only
2021-12-09 17:41:03.101 DEBUG 32340 --- [4jDriverIO-2-21] .d.n.c.t.ReactiveNeo4jTransactionManager : Participating transaction failed - marking existing transaction as rollback-only
2021-12-09 17:41:03.102 DEBUG 32340 --- [4jDriverIO-2-21] .d.n.c.t.ReactiveNeo4jTransactionManager : Initiating transaction rollback
2021-12-09 17:41:03.126 ERROR 32340 --- [4jDriverIO-2-21] c.a.c.s.e.api.CostingApiException        : UNEXPECTED_ERROR - Node(2348) already exists with label `LinkedEntity` and properties `tenant` = '15', `code` = 'JANDJ'; Error code 'Neo.ClientError.Schema.ConstraintValidationFailed'; nested exception is org.neo4j.driver.exceptions.ClientException: Node(2348) already exists with label `LinkedEntity` and properties `tenant` = '15', `code` = 'JANDJ' - Node(2348) already exists with label `LinkedEntity` and properties `tenant` = '15', `code` = 'JANDJ'; Error code 'Neo.ClientError.Schema.ConstraintValidationFailed'; nested exception is org.neo4j.driver.exceptions.ClientException: Node(2348) already exists with label `LinkedEntity` and properties `tenant` = '15', `code` = 'TEST'

At this line I can't understand why removing all additional labels: MERGE (n:`LinkedEntity` {code: $__id__}) SET n += $__properties__ REMOVE n:`BU15`:`BU16` SET n:`BU15` RETURN id(n)

[meistermeier]

We remove and set the labels because we need to be sure that after the persist operation you are left only with the labels defined on you entity at the moment of calling save.
I am currently testing if there is any possible constellation that would somehow trigger the creation.

[fabienOuedraogo]

@meistermeier Thank for your response and your investigation.
I'm currently trying to setup a compound key (code, tenant) for my nodes to check if I can avoid constraint violation. I assume it is possible to have compound key like @Id MyCompoundKey id;

[meistermeier]

FYI: A composite key won't work, yet.
There is already an open issue for this enhancement #2448

[meistermeier]

I am currently wondering what version of Spring Data Neo4j 6 you are using.
The generated query for the related node:
MATCH (n) WHERE n.code....
should be
MATCH (linkedEntity:LinkedEntity) WHERE linkedEntity.code = $__id__
in the more current versions.
Also the REMOVE part for the labels is not explicit anymore in the queries.
A more current version could help (6.1.latest / 6.2.latest)

[fabienOuedraogo]

@meistermeier I used version 6.0.6 and then migrated to 6.1.1. The log I posted was for both versions, I think. Do you mean an higher version than 6.1.1 could help?

[meistermeier]

Yes definitely, we did some enhancement in this area. If possible use 6.1.7 (latest 6.1 as of this writing) or 6.2.0.

[fabienOuedraogo]

Ok thank you @meistermeier

[meistermeier]

Closing this for now. If the problem persists if using more current versions, feel free to open this issue again.