1

I have a jpa configuration like this: 

    @Id
    //@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="seq_gen")
    @GeneratedValue(generator = "timedep_seq_gen")
    @GenericGenerator(
             name = "seq_gen",
             strategy = "org.hibernate.id.enhanced.SequenceStyleGenerator",
                     parameters = {
                                @Parameter(name = "sequence_name", value = "sequence_myseq"),
                                @Parameter(name = "initial_value", value = "1"),
                                @Parameter(name = "increment_size", value = "10"),
                                @Parameter(name = "optimizer", value ="hilo")
                                }
            )
    private Long id;

The insertions are creating id values like 1,2,3.. and this is fine till I manually do 

SELECT nextval('sequence_myseq');

I expect that on running the above from pgadmin(or any other client), the next set of values generated by the jpa/hibernate generator should skip the values for the id column, but that is not the case. It still generates the values without skipping any id values. What is the problem here ?

EDIT 1 Till I get some concrete answer, looks like hilo optimization will not work for multiple instances. The following is working but it needs you to set 

 increment by 10

in your sequence definition as well.

@GeneratedValue(generator = "dep_seq_gen")
    @SequenceGenerator(
            name = "dep_seq_gen",
            sequenceName = "sequence_dep",
            allocationSize = 10
        )
Vlad Mihalcea
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user2599052
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1 Answers1

2

Hilo limitations

Hilo algorithm is not interoperable with systems that don't know the hilo allocations scheme, and this is why Hibernate supports the pooled optimizer.

Pooled optimizer

Unlike hilo, the pooled optimizer includes the database sequence values in the identifier values allocated by the application. For this reason, any new sequence value is not going to conflict with previous or future values.

Since pooled is used by default, you can also simplify your @Id mapping using the SequenceGenerator instead of the more verbose @GenericGenerator you used for hilo:

@Id
@GeneratedValue(
    strategy = GenerationType.SEQUENCE,
    generator = "sequence_myseq"
)
@SequenceGenerator(
    name = "sequence_myseq",
    sequenceName = "sequence_myseq",
    allocationSize = 3
)
private Long id;

Migrating from hilo to pooled

If you used hilo and want to migrate to the pooled optimizer, you will need to change the sequence value as, otherwise, conflicts will be generated.

Vlad Mihalcea
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  • ' is not interoperable with systems that don't know the hilo allocations scheme', but I am talking about the two instances of the same server which have the same code. Hence they both know the hilo allocation, still it doesn't work. I see the LegacyHiLoAlgorithmOptimizer used to support this but now they have removed in the new implementation – user2599052 Feb 05 '20 at 11:40
  • If you can replicate the issue using [this test case template](https://in.relation.to/2016/01/14/hibernate-jpa-test-case-template/) against the latest Hibernate ORM version, then you should open a Jira issue. Use two distinct `SesisonFactory` instances to emulate multiple servers and use two Threads to see if you get the conflict. – Vlad Mihalcea Feb 05 '20 at 11:47
  • If Hibernate says that this hilo optimization can be used in multi server environment, then there is no doubt that its a defect. The code to generate value doesn't even depend on the value of sequence from callback. Only the high values change. – user2599052 Feb 05 '20 at 12:20
  • 1
    Luckily, Hibernate is an open-source project, so you can fix the issue and send a Pull Request. That's the true spirit of open-source software development. – Vlad Mihalcea Feb 05 '20 at 12:29
  • sure. but i need a defect to be created first. – user2599052 Feb 05 '20 at 12:34