Hibernate Envers revision number order - oracle

Question

I used Envers to audit my entities. The DB used is Oracle 11g. For the revision number of the revision entity, I used a oracle sequence. But since the oracle sequence does not guarantee monotonic increasing of each call to nextval, In my revision table, I got something like this,
We can see that the rev number is not monotonically increasing. In the audit table of my entity, I have this:
By chaining the records together with the rev number to form a timeline, I got :
24 --> 1302 --> 1303 --> 1355 --> 1304 --> 1356 --> 1357 --> 1305 -->1358 --> null
In fact, I have a cluster of 2 servers. They both can persist data into the DB. I suspect that this has relation to the problem of order in revnumber. Because of this problem. Query like MyEntity anEntity = auditReader.find(MyEntity.class, id, revNum) doesn't work because of
org.hibernate.envers.query.impl.AbstractAuditQuery.getSingleResult(AbstractAuditQuery.java:117) . I checked the SQL generated by Hibernate, in the where clause
where
myentity.rev<=?
and myentity.revtype<>?
and myentity.id=?
and (
myentity.revend>?
or myentity.revend is null
)
so for the rev number 1356, several audit records are retrieved, for example
1356 --> 1357 and 1305 -->1358 because rev num 1356 is just between the two ends.
How can I solve this problem? I mean to make the rev number monotonically increasing one transaction after another.
UPDATE
My revision entity
#Entity
#RevisionEntity(CustomRevisionListener.class)
#Table(name = "REV_TABLE")
#SequenceGenerator(name = "GENERIC_GENERATOR", sequenceName = "SQ_REVISION_ID")
public class Revision {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator ="GENERIC_GENERATOR")
#Column(nullable = false, name = REV)
#RevisionNumber
private long rev;
}

Answer 1

You probably want to take a look at how the revision number sequence is defined inside the SequenceIdRevisionEntity class. We essentially define it as follows:
#Id
#GeneratedValue(generator = "RevisionNumberSequenceGenerator")
#GenericGenerator(
name = "RevisionNumberSequenceGenerator",
strategy = "org.hibernate.envers.enhanced.OrderedSequenceGenerator",
parameters = {
#Parameter(name = "table_name", value = "REVISION_GENERATOR"),
#Parameter(name = "sequence_name", value = "REVISION_GENERATOR"),
#Parameter(name = "initial_value", value = "1"),
#Parameter(name = "increment_size", value = "1")
}
)
#RevisionNumber
private int id;
The key is specifying that the initial_value and increment_size are defined as 1 to avoid the hi-lo gaps you're noticing with your existing sequence definition.