PostgreSQL, Hibernate : Default increase sequence length by 1

Question

I am working on a Spring-MVC project in which we are using Hibernate as our ORM and PostgreSQL as the database. We have a Students class, whose ID we are using in one of the PDF form generated, and for business reasons we require that the number be incremented by 1 always. I checked that the allocation-size parameter can be changed for Hibernate, but does it also effect the underlying sequence in PostgreSQL or do I have to create a new one?

If the underlying sequence is not altered by Hibernate, how can I change the sequence so that it's auto-incremented by 1 in PostgreSQL. Thank you.

Code :

  @Id
    @Column(name="studentid")
    @GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "student_gen")
    @SequenceGenerator(name = "student_gen",sequenceName = "student_seq",allocationSize = 1)
    private int studentid;

Kayaman · Accepted Answer · 2017-03-31 08:36:18Z

2

No, the sequence in Postgres won't be changed just by modifying the Hibernate annotation.

You can use ALTER SEQUENCE student_seq INCREMENT BY 1 to modify the sequence.

answered Mar 31, 2017 at 8:36

Kayaman

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2 Comments

We are Borg Over a year ago

Thank you. If I don't change the allocation size on Model and just give the above command, is that okay? As it will take us a new deployment. Thank you.

Kayaman Over a year ago

No, it won't be okay actually. See stackoverflow.com/questions/2595124/… and stackoverflow.com/questions/5346147/… for more info. Basically the generator works with the database sequence, and unless the allocationSize is the same as INCREMENT BY, the values generated can become really odd.

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