Hibernate SequenceGenerator and allocationSize

Question

We all know the default behaviour of Hibernate when using  SequenceGenerator - it increases real database sequence by one  multiple this value by 50  default allocationSize value  - and then uses this value as entity ID   This is incorrect behaviour and conflicts with specification which says      allocationSize -  Optional  The amount to increment by when allocating sequence numbers from the sequence    To be clear  I do not bother about gaps between generated IDs   I care about IDs that are not consistent with underlying database sequence  For example  any other application  that e g  uses plain JDBC  may want to insert new rows under IDs obtained from sequence - but all those values may be already used by Hibernate  Madness   Do somebody know any solution to this problem  without setting allocationSize 1 and thus degrading performance    EDIT  To make things clear  If last inserted record had ID   1  then HB use values 51  52  53    for its new entities BUT at the same time  sequence s value in database will be set to 2  Which can easily leads to errors when other applications are using that sequence     On the othe hand  specification says  in my understanding  that database sequence should have been set to 51 and in the meantime HB should use values from range  2  3     50  UPDATE    As Steve Ebersole mentioned below  the behaviour described by me  and also the most intuitive for many  can be enabled by setting hibernate id new generator mappings true   Thanks all of You   UPDATE 2  For future readers  below you can find a working example    Entity  Table name    users   public class User         Id      GeneratedValue strategy   GenerationType SEQUENCE  generator    USERS SEQ        SequenceGenerator name    USERS SEQ   sequenceName    SEQUENCE USERS       private Long id      persistence xml   lt persistence-unit name  testPU  gt     lt properties gt       lt property name  hibernate id new generator mappings  value  true    gt     lt  properties gt   lt  persistence-unit gt

User · Answer

I would check the DDL for the sequence in the schema. JPA Implementation is responsible only creation of the sequence with the correct allocation size. Therefore, if the allocation size is 50 then your sequence must have the increment of 50 in its DDL.

This case may typically occur with the creation of a sequence with allocation size 1 then later configured to allocation size 50 (or default) but the sequence DDL is not updated.

User · Answer

After digging into hibernate source code and  Below configuration goes to Oracle db for the next value after 50 inserts  So make your INST PK SEQ increment 50 each time it is called   Hibernate 5 is used for below strategy  Check also below http   docs jboss org hibernate orm 5 1 userguide html single Hibernate User Guide html identifiers-generators-sequence   Id  Column name    ID    GenericGenerator name    INST PK SEQ    strategy    org hibernate id enhanced SequenceStyleGenerator   parameters              org hibernate annotations Parameter                  name    optimizer   value    pooled-lo             org hibernate annotations Parameter                  name    initial value   value    1             org hibernate annotations Parameter                  name    increment size   value    50             org hibernate annotations Parameter                  name   SequenceStyleGenerator SEQUENCE PARAM  value    INST PK SEQ             GeneratedValue strategy   GenerationType SEQUENCE  generator    INST PK SEQ   private Long id

User · Answer

allocationSize 1 It is a micro optimization before getting query Hibernate tries to assign value in the range of allocationSize and so try to avoid querying database for sequence  But this query will be executed every time if you set it to 1  This hardly makes any difference since if your data base is accessed by some other application then it will create issues if same id is used by another application meantime     Next generation of Sequence Id is based on allocationSize   By defualt it is kept as 50 which is too much  It will also only help if your going to have near about 50 records in one session which are not persisted and which will be persisted using this particular session and transation   So you should always use allocationSize 1 while using SequenceGenerator  As for most of underlying databases sequence is always incremented by 1

User · Answer

To be absolutely clear    what you describe does not conflict with the spec in any way   The spec talks about the values Hibernate assigns to your entities  not the values actually stored in the database sequence   However  there is the option to get the behavior you are looking for   First see my reply on Is there a way to dynamically choose a  GeneratedValue strategy using JPA annotations and Hibernate   That will give you the basics   As long as you are set up to use that SequenceStyleGenerator  Hibernate will interpret allocationSize using the  pooled optimizer  in the SequenceStyleGenerator   The  pooled optimizer  is for use with databases that allow an  increment  option on the creation of sequences  not all databases that support sequences support an increment    Anyway  read up about the various optimizer strategies there

User · Answer

Steve Ebersole  amp  other members  Would you kindly explain the reason for an id with a larger gap by default 50   I am using Hibernate 4 2 15 and found the following code in org hibernate id enhanced OptimizerFactory cass   if   lo  gt  maxLo        lastSourceValue   callback getNextValue       lo   lastSourceValue eq  0     1   0     hi   lastSourceValue copy   multiplyBy  maxLo 1         value   hi copy   add  lo        Whenever it hits the inside of the if statement  hi value is getting much larger   So  my id during the testing with the frequent server restart generates the following sequence ids  1  2  3  4  19  250  251  252  400  550  750  751  752  850  1100  1150   I know you already said it didn t conflict with the spec  but I believe this will be very unexpected situation for most developers      Anyone s input will be much helpful    Jihwan  UPDATE  ne1410s  Thanks for the edit  cfrick  OK  I will do that   It was my first post here and wasn t sure how to use it   Now  I understood better why maxLo was used for two purposes  Since the hibernate calls the DB sequence once  keep increase the id in Java level  and saves it to the DB  the Java level id value should consider how much was changed without calling the DB sequence when it calls the sequence next time     For example  sequence id was 1 at a point and hibernate entered 5  6  7  8  9  with allocationSize   5   Next time  when we get the next sequence number  DB returns 2  but hibernate needs to use 10  11  12    So  that is why  hi   lastSourceValue copy   multiplyBy  maxLo 1    is used to get a next id 10 from the 2 returned from the DB sequence   It seems only bothering thing was during the frequent server restart and this was my issue with the larger gap   So  when we use the SEQUENCE ID  the inserted id in the table will not match with the SEQUENCE number in DB

User · Answer

I too faced this issue in Hibernate 5    Id  GeneratedValue strategy   GenerationType SEQUENCE  generator   SEQUENCE   SequenceGenerator name   SEQUENCE  sequenceName   SEQUENCE  private Long titId    Got a warning like this below      Found use of deprecated  org hibernate id SequenceHiLoGenerator  sequence-based id generator  use org hibernate id enhanced SequenceStyleGenerator instead  See Hibernate Domain Model Mapping Guide for details    Then changed my code to SequenceStyleGenerator    Id  GenericGenerator name  cmrSeq   strategy    org hibernate id enhanced SequenceStyleGenerator           parameters                      Parameter name    sequence name   value    SEQUENCE       GeneratedValue generator    sequence name   private Long titId    This solved my two issues    The deprecated warning is fixed Now the id is generated as per the oracle sequence

[java] Hibernate, @SequenceGenerator and allocationSize

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