Unique index on a superclass and value reusable between different subclasses

Question

Unique index on a superclass and value reusable between different subclasses

In a project using Spring Data Neo4j 3.2, I have a model that looks like this:

@NodeEntity
public abstract class A {
    @GraphId
    public Long id;
    @Indexed(unique = true)
    public Long technicalId;
}

@NodeEntity
public class B extends A {}

@NodeEntity
public class C extends A {}

I missed the paragraph in the documentation about the default merge function and we ran into the following situation without getting an exception:

B b = new B();
b.technicalId = 42;
neo4jTemplate.save(b);
// I now have Node[1] in Neo4j with the following labels: B, _B, A

C c = new C();
c.technicalId = 42;
neo4jTemplate.save(c);
// No exception and Node[1] now has the following labels: B, _B, A, C, _C

So, the situation can be avoided:

either using instance-based indexes :

@NodeEntity
public abstract class A {
    @GraphId
    public Long id;
    @Indexed(unique = true, level = Level.INSTANCE)
    public Long technicalId;
}

or using failOnDuplicate

(although it is not mentioned in the documentation, even for 3.3, but I found it here and here ), which avoids creating 3 indexes instead of 1, so less I / O on write and less disk space:

@NodeEntity
public abstract class A {
    @GraphId
    public Long id;
    @Indexed(unique = true, failOnDuplicate = true)
    public Long technicalId;
}

However, is it not a mistake that the default behavior will change the nature of the node (given a class hierarchy) and create a combination of labels that might prevent the object from being created? I mean the node now has two labels prefixed with:, n:B:_B:A:C:_C

because two Cypher requests were requested:

MERGE (n:`A` {`technicalId`: {value}})
  ON CREATE SET n={props} SET n:SupplierCompany
  return n
// params {value=42, props={technicalId=42}}
match (n)
  where id(n)={nodeId}
  set n:`A`:`C`:`_C`
// params {nodeId=1}