GeneratedValue in Postgres

Question

I have my entity class mapped like below:

@Entity
@Audited
@Table(name=\"messages_locale\")
public class Locale {

    @Id
    @GeneratedValue
    @Getter @S         


        

Answer 1

In PostgreSQL auto-increment is handled using the SERIAL pseudo type. You use this type when you execute CREATE TABLE.

Now to the point - this SERIAL pseudo type creates a sequence. Autoincrement in PostgreSQL is handled using the created sequence. The default value of the id column becomes - nextval('your_sequence_name').

In Hibernate for an User entity:

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "users_seq_gen")
@SequenceGenerator(name = "users_seq_gen", sequenceName = "users_id_seq")
public Long getId() {
     return id;
}

Read here:

http://www.postgresql.org/docs/8.4/static/datatype-numeric.html#DATATYPE-SERIAL

http://www.neilconway.org/docs/sequences/