How to choose the id generation strategy when using JPA and Hibernate

Question

I was going through Id generation section of the Hibernate reference guide and  java persistence with Hibernate   There are quite a few options available with Hibernate and JPA combined   I was looking for a further documentation on how to choose the specific id generation strategy   I am also looking for tipping points   For example  hilo strategy is expected to reduce contention  I am assuming there must be a trade off associated with this choice    I want to be educated about the trade offs   Is there any literature available

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A while ago i wrote a detailed article about Hibernate key generators: http://blog.eyallupu.com/2011/01/hibernatejpa-identity-generators.html

Choosing the correct generator is a complicated task but it is important to try and get it right as soon as possible - a late migration might be a nightmare.

A little off topic but a good chance to raise a point usually overlooked which is sharing keys between applications (via API). Personally I always prefer surrogate keys and if I need to communicate my objects with other systems I don't expose my key (even though it is a surrogate one) – I use an additional ‘external key’. As a consultant I have seen more than once 'great' system integrations using object keys (the 'it is there let's just use it' approach) just to find a year or two later that one side has issues with the key range or something of the kind requiring a deep migration on the system exposing its internal keys. Exposing your key means exposing a fundamental aspect of your code to external constrains shouldn’t really be exposed to.

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I find this lecture very valuable https   vimeo com 190275665  in point 3 it summarizes these generators and also gives some performance analysis and guideline one when you use each one

User · Answer

Basically  you have two major choices   You can generate the identifier yourself  in which case you can use an assigned identifier  You can use the  GeneratedValue annotation and Hibernate will assign the identifier for you   For the generated identifiers you have two options   UUID identifiers  Numerical identifiers   For numerical identifiers you have three options   IDENTITY SEQUENCE TABLE  IDENTITY is only a good choice when you cannot use SEQUENCE  e g  MySQL  because it disables JDBC batch updates  SEQUENCE is the preferred option  especially when used with an identifier optimizer like pooled or pooled-lo  TABLE is to be avoided since it uses a separate transaction to fetch the identifier and row-level locks which scales poorly

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The API Doc are very clear on this   All generators implement the interface org hibernate id IdentifierGenerator  This is a very simple interface  Some applications can choose to provide their own specialized implementations  however  Hibernate provides a range of built-in implementations  The shortcut names for the built-in generators are as follows  increment generates identifiers of type long  short or int that are unique only when no other process is inserting data into the same table  Do not use in a cluster  identity supports identity columns in DB2  MySQL  MS SQL Server  Sybase and HypersonicSQL  The returned identifier is of type long  short or int  sequence uses a sequence in DB2  PostgreSQL  Oracle  SAP DB  McKoi or a generator in Interbase  The returned identifier is of type long  short or int hilo uses a hi lo algorithm to efficiently generate identifiers of type long  short or int  given a table and column  by default hibernate unique key and next hi respectively  as a source of hi values  The hi lo algorithm generates identifiers that are unique only for a particular database  seqhilo uses a hi lo algorithm to efficiently generate identifiers of type long  short or int  given a named database sequence  uuid uses a 128-bit UUID algorithm to generate identifiers of type string that are unique within a network  the IP address is used   The UUID is encoded as a string of 32 hexadecimal digits in length  guid uses a database-generated GUID string on MS SQL Server and MySQL  native selects identity  sequence or hilo depending upon the capabilities of the underlying database  assigned lets the application assign an identifier to the object before save   is called  This is the default strategy if no  element is specified  select retrieves a primary key  assigned by a database trigger  by selecting the row by some unique key and retrieving the primary key value  foreign uses the identifier of another associated object  It is usually used in conjunction with a  primary key association  sequence-identity a specialized sequence generation strategy that utilizes a database sequence for the actual value generation  but combines this with JDBC3 getGeneratedKeys to return the generated identifier value as part of the insert statement execution  This strategy is only supported on Oracle 10g drivers targeted for JDK 1 4  Comments on these insert statements are disabled due to a bug in the Oracle drivers   If you are building a simple application with not much concurrent users  you can go for increment  identity  hilo etc   These are simple to configure and did not need much coding inside the db  You should choose sequence or guid depending on your database  These are safe and better because the id generation will happen inside the database  Update  Recently we had an an issue with idendity where primitive type  int  this was fixed by using warapper type  Integer  instead

[java] How to choose the id generation strategy when using JPA and Hibernate

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