Cui Pengfei ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) *updated* an issue Hibernate ORM ( https://hibernate.atlassian.net/browse/HHH?atlOrigin=eyJpIjoiNDQxY2UyNGQw... ) / Bug ( https://hibernate.atlassian.net/browse/HHH-16054?atlOrigin=eyJpIjoiNDQxY2... ) HHH-16054 ( https://hibernate.atlassian.net/browse/HHH-16054?atlOrigin=eyJpIjoiNDQxY2... ) JPA / Hibernate, duplicate pkey error when updating entity that is a subclass of a base class that uses IdClass for composite primary key ( https://hibernate.atlassian.net/browse/HHH-16054?atlOrigin=eyJpIjoiNDQxY2... ) Change By: Cui Pengfei ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) h1. # How to reproduce this issue [ <strike> https://github.com/cuipengfei/Spikes/tree/master/jpa/ClassIdUpdateIssue |https://github.com/cuipengfei/Spikes/tree/master/jpa/ClassIdUpdateIssue|smart-link] ~~ this code can reproduce the issue, just run the main method then the error will happen. </strike> https://github.com/gregturn/spring-data-jpa-id-class-issues/tree/main/src... Just make sure you have docker installed and run these 👆 unit tests. The unit test with **EmbeddedId** will be ok. But the one with **IdClass** will **fail**, while we **expect** it to be **successful**. h1. Issue Description There is a base class like this: {code:java} @Entity @Inheritance(strategy = InheritanceType.SINGLE_TABLE) @DiscriminatorFormula("case when vip_number is not null then 'vip' else 'normal' end") @DiscriminatorValue("normal") @IdClass(CustomerPK.class) public class CustomerWithIdClass implements Serializable { private String firstName; private String lastName; @Id private Long versionId; @Id private Long unitId; protected CustomerWithIdClass() { } // getter and setters ...... }{code} Its IdClass is like this: {code:java}@NoArgsConstructor @EqualsAndHashCode @Embeddable public class CustomerPK implements Serializable { private Long unitId; private Long versionId; public void setUnitId(Long unitId) { this.unitId = unitId; } public void setVersionId(Long versionId) { this.versionId = versionId; } }{code} Then it has a subclass: {code:java}@Entity @DiscriminatorValue("vip") public class VipCustomerWithIdClass extends CustomerWithIdClass { private String vipNumber; public VipCustomerWithIdClass() { } public VipCustomerWithIdClass(String firstName, String lastName, String vipNumber) { super(firstName, lastName); this.vipNumber = vipNumber; } public String getVipNumber() { return vipNumber; } public void setVipNumber(String vipNumber) { this.vipNumber = vipNumber; } } {code} The subclass only adds one additional field, nothing else fancy. Then when I try to persist an instance of the subclass like this: {code:java}        CustomerWithIdClass customer = new CustomerWithIdClass("a", "b"); customer.setVersionId(123L); customer.setUnitId(456L); repository.save(customer);//save object of base class, ok customer.setFirstName("a2"); repository.save(customer);//modify object of base class and save again, ok VipCustomerWithIdClass vipCustomer = new VipCustomerWithIdClass("a", "b", "888"); vipCustomer.setVersionId(987L); vipCustomer.setUnitId(654L); repository.save(vipCustomer);//save object of subclass, ok vipCustomer.setVipNumber("999"); repository.save(vipCustomer);//modify object of subclass and save again, NOT OK // ↑ THIS FAILS BECAUSE OF PRIMARY KEY CONFLICT. INSERT STATEMENT WAS USED INSTEAD OF UPDATE, WHY? // this failure only happens when: // 1. base class uses IdClass for composite primary key // 2. saving an instance of the subclass for the second time after modification {code} h1. The Error Then there will be an *error of duplicate pkey* when I try to save the instance of the *subclass* for the *second time* *after some modification*. The error seems to be related with the @*IdClass* annotation, because I have tried using @*EmbeddedId* and @*Embeddable* for composite pkey, then the error does not happen. h1. The question What is the root reason of this issue? Is @IdClass not supposed to be used for this scenario? h1. links [https://stackoverflow.com/questions/75147518/jpa-hibernate-duplicate-pkey...] [https://github.com/spring-projects/spring-data-jpa/issues/2767|https://gi...] ( https://hibernate.atlassian.net/browse/HHH-16054#add-comment?atlOrigin=ey... ) Add Comment ( https://hibernate.atlassian.net/browse/HHH-16054#add-comment?atlOrigin=ey... ) Get Jira notifications on your phone! Download the Jira Cloud app for Android ( https://play.google.com/store/apps/details?id=com.atlassian.android.jira.... ) or iOS ( https://itunes.apple.com/app/apple-store/id1006972087?pt=696495&ct=Em... ) This message was sent by Atlassian Jira (v1001.0.0-SNAPSHOT#100214- sha1:771690a )