java - Hibernate generates negative id values when using a sequence

Question

I have a class with the following definition:

@Id
@SequenceGenerator(name = "SEQ_ACE_WORKERS_QUEUE_STATS_ID", sequenceName = "SEQ_ACE_WORKERS_QUEUE_STATS_ID", allocationSize = 500)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_ACE_WORKERS_QUEUE_STATS_ID")
@Column(name = "ID")
private long Id;

When we ran it on Jboss 4.2.3 it worked fine and generated the proper ID's (starting from 1000+)

Now we moved to jboss 7.1.1 and it generates negative ID's! (starting from -498 and going up)

Any idea why this might happen?

Answer 1

The new behaviour is the followings:

AllocationSize is a range of primary key values reserved for Hibernate. And the select seq.nextval from dual will be done only after hibernate consumed this range of primary keys.

So you must declare the same value on both allocationSize (Hibernate) and sequence increment by (DB)

When explicitly set allocationSize=500, e.g. on Oracle

create sequence SEQ_ACE_WORKERS_QUEUE_STATS_ID
       MINVALUE 1 
       MAXVALUE 999999999999999999999999999 
       START WITH 1
       INCREMENT BY 500 
       NOCACHE 
       NOCYCLE;

Otherwise, you'll notice negative values or constraint errors raised from your DB because of primary key collisions.

When the app server is restarted, you'll notice the 'jump' between the latest primary key allocated, and the 'newly' sequence number selected at restart.

Final comment: default value is 50. So if you don't specify allocationSize on the Hibernate side, you must declare increment by 50 on the DB side.