Delete then create entity using Spring JPA with Hibernate and @Transactional violates unique key constraints

Question

Setup: SpringBoot application using SpringJPA with Hibernate

I have two entities: A and B. Set is a child of A.

I want to remove a B and create another one in a characteristic which would hit a unique constraint. To avoid that I first need to delete the old B before creating a new one. Since I am in a transaction, I have to flush after deletion.

Executing the following code will still fail:

    @Transactional
    void removeOldBsAndCreateNewOnes(A a) {
        final Set<B> bSet = a.getBs();
        final Set<B> removedBs = new HashSet<>();
        bSet.stream()
                .filter(
                    //magic stuff here
                )
                .forEach(b -> {
                    bRepository.delete(b);
                    // Flush is needed as we are in a transaction and not flushing will make hibernate to insert the new B first on commit which will violate the configured unique constraints.
                    bRepository.flush();
                    removedBs.add(b);
                });
        bSet.removeAll(removedBs);
    
        final Set<B> newBs = new HashSet<>();
        // Doing some stuff to detemine new Bs
        bRepository.saveAll(newBs);
        bSet.addAll(newBs);
    }

Nevertheless I get a unique constraint violation error. flush() is not executed. I already searched for reasons and looked here without success:

itsfoobar · Accepted Answer · 2025-07-13 19:53:28Z

Because of some strange solutions which only cause much more problems (e.g. creating a manual delete query using @Modifying causes the EntityManager to explode or doing delete and create in separate transactions) I would like to document what I've found out:

Before a refactoring everything worked like expected: flush() was executed and the entity immediately got deleted. After weeks of the refactoring step the bug came up and nobody knew why.

Solution: You need to remove the entity from the parent first. Otherwise Hibernate will not execute flush().
Example:

        bSet.stream()
                .filter(
                    //magic stuff here
                )
                .forEach(b -> {
                    bRepository.delete(b);
                    // Flush is needed as we are in a transaction and not flushing will make hibernate to insert the new B first on commit which will violate the configured unique constraints.
                    removedBs.add(b);
                });
        bSet.removeAll(removedBs);
        bRepository.flush();

        // Create new Bs

Or in a correct order:

        bSet.stream()
                .filter(
                    //magic stuff here
                )
                .forEach(b -> {
                    bSet.remove(b);
                    bRepository.delete(b);
                });
        // Flush is needed as we are in a transaction and not flushing will make hibernate to insert the new B first on commit which will violate the configured unique constraints.
        bRepository.flush();

        // Create new Bs

Hope this helps!

Collectives™ on Stack Overflow

Delete then create entity using Spring JPA with Hibernate and @Transactional violates unique key constraints

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related