javax.persistence.EntityExistsException with SequenceGenerator

Question

I am inserting some records in Oracle DB. For the uniqueness, I am using SequenceGenerator. Below is the code:

public class XxspPoInLineLocqty implements Serializable {
    @Id 
    @SequenceGenerator(name = "SequenceLocIdGenerator", sequenceName = "LINE_LOCQTY_JPA_ID_SQ")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SequenceLocIdGenerator")
    @Column(name="LINE_LOCQTY_JPA_ID")
    private Long lineLocqtyJPAId;

//other fields..
}

XxspPoInLineLocqty is having @ManyToOne relation with XxspPoInLine. When I am persisting XxspPoInLine entity, I am receiving below error:

javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [com.bcone.oracle.ebs.model.XxspPoInLineLocqty#76]
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:116)
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:155)
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:162)
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:804)
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:764)
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener$1.cascade(JpaPersistEventListener.java:80)
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:391)

I looked on the stackoverflow and found some solutions for this: 1. Use allocationSize=1 Since I am having 5000+ XxspPoInLineLocqty , this would be the worst option I could apply. I tried this as well but after 40min my network got fluctuate and persisting got failed. I cannot use this option as it degrade the performance.

2. Increse the value of allocation size I increased the allocationSize=500, but still faced the same issue at different identifier(#372).

javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [com.bcone.oracle.ebs.model.XxspPoInLineLocqty#-372]
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:116)
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:155)
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:162)
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:804)
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:764)
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener$1.cascade(JpaPersistEventListener.java:80)
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:391)
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:316)

Even tried GenerationType.AUTO, but no luck. Below is the sequence on Oracle DB:

CREATE SEQUENCE  "APPS"."LINE_LOCQTY_JPA_ID_SQ"  MINVALUE 1 MAXVALUE 999999999999999999999999999 INCREMENT BY 1 START WITH 7641 CACHE 20 NOORDER  NOCYCLE ;

I am still confused why this issue is coming up. I didn't understand the root cause of this. Can someone explain me the root cause of this exception, and what should be the work around?

Note : Before inserting the records, I deleted all the rows from table. So the table is blank when I execute the above sequnce code.

krokodilko krokodilko · Accepted Answer · 2018-01-01T13:09:44

allocationSize parameter must match the INCREMENT BY value of the sequence.

It works in such a way that Hibernate gets a value from the sequence (from the database), and then keeps that value in the memory and generates next X subsequent identifiers (where X=allocationSize) incrementing this value by 1 in the memory, without reaching for the database.

Once Hibernate generates X identifiers, it gets the next value from the sequence, and generates new X identifiers, incrementing that value by 1

A simple example - let say that:

@SequenceGenerator( ....allocationSize=5 ...)
CREATE SEQUENCE .... INCREMENT BY 1 ...

In the above case Hibernate:

Fetches the first number from the sequence - let say NextVal = 1 and stores it in the memory
Generates next allocationSize=5 identifiers incrementing the above value by 1, that is: Id = 1, 2, 3, 4, 5
Fetches the next number from the sequence - because of INCREMENT BY 1, the nextVal will be: 2
Generates next allocationSize=5 identifiers incrementing the above value by 1, that is: Id = 2, 3, 4, 5, 6

As you can see, it will cause a dulicate error.

Now please consider this case:

@SequenceGenerator( ....allocationSize=5 ...)
CREATE SEQUENCE .... INCREMENT BY 5 ...

In this case Hibernate:

Fetches the first number from the sequence - let say NextVal = 1 and stores it in the memory
Generates next allocationSize=5 identifiers incrementing the above value by 1, that is: Id = 1, 2, 3, 4, 5
Fetches the next number from the sequence - because of INCREMENT BY 5, the nextVal will be: 6
Generates next allocationSize=5 identifiers incrementing the above value by 1, that is: Id = 6, 7, 8, 9, 10

In this case there is no duplicate error.

The last case has the disadvantage that if the sequence is used outside of Hibernate, then the sequence will produce gaps.

javax.persistence.EntityExistsException with SequenceGenerator

1 Answers