Hibernate PESSIMISTIC_WRITE not locking db and returning oldValue

Question

I am using "Postgres" database and pessimistic_locking for locking database row.

I have the following code

@Transactional
doProcess(int id, int quantity){
   Article article = lockArticle(id);
   modifyArticle(article, quantity);
}

This is lockArticle() function which locks and fetches article from DB(Postgres)

Article lockArticle(int id){
        return sessionFactory.getCurrentSession().createCriteria(Article.class)
                .add(Restrictions.eq("id", id))
                .setLockMode(LockMode.PESSIMISTIC_WRITE)
                .setTimeout(10000)
                .getUniqueResult();
    }

Here is the modifyArticle(), which basically deletes/updates article entry in database.

modifyArticle(Article article, int quantity){

 if(article.getQuantity()<quantity){
     dao.delete(article);
 }

 else{
   article.setQuantity(article.getQuantity()-quantity)
   dao.updateArticle(article);
  }
}

//DAO for updateArticle

@Transactional
updateArticle(Article article){
   sessionFactory.getCurrentSession().saveOrUpdate(article);
}

Let's say initially in db, article has quantity 10.

I have spawned 2 threads to update article quantity, first thread is spawned with quantity = 2, second thread with 3. So ideally the DB after both the finished processing should be 5(10-2-3).

But database net quantity in db is either 8(10-2)/7(10-3).

Can someone please help me understand why PESSIMISTIC_LOCKING is not working and what would be a workaround to fix this?

Answer 1

After getting the lock, if i did session.refresh(entity), i got the updated value.