A batch sequence generator for Hibernate that uses recursive queries to preallocate multiple values in a single database access.

<dependency> <groupId>com.github.marschall</groupId> <artifactId>hibernate-batch-sequence-generator</artifactId> <version>1.1.0</version> </dependency>

This sequence generator combines the advantages of several existing sequence generators and avoids their disadvantages

• hi/lo
  • all database access has to be aware of it
  • there is no clear relationship from the current sequence value to the column value
• pooled and pooledlo
  • INCREMENT BY value has to be set on the database sequence
  • direct use of the sequence can cause a lot of identifier waste
  • the pool size and the INCREMENT BY value need to match
• IDENTITY
  • does not support JDBC batch inserts
• TABLE
  • has bad write performance

The limitations of this sequence generator are

• limited database dialect support (see below)
• if you're using hbm2ddl then the CACHE value on the sequence is not set

You can use this sequence generator like this

@Id @GenericGenerator( name = "some_column_name_id_generator", strategy = "com.github.marschall.hibernate.batchsequencegenerator.BatchSequenceGenerator", parameters = { @Parameter(name = "sequence", value = "SOME_SEQUENCE_NAME"), @Parameter(name = "fetch_size", value = "SOME_FETCH_SIZE_VALUE") }) @GeneratedValue(generator = "some_column_name_id_generator") @Column(name = "SOME_COLUMN_NAME") private Long someColumnName;

You need to configure the following things

SOME_SEQUENCE_NAME

the SQL name of the sequence from which the values should be fetched

SOME_FETCH_SIZE_VALUE

integer, how many values should be fetched at once, this should be equal to the CACHE value of the sequence

SOME_COLUMN_NAME

the SQL name of the column for which the value should be generated

some_column_name_id_generator

unique if of the generator

The following RDBMS have been verified to work

• DB2
• Firebird
• H2
• HSQLDB
• MariaDB 10.3 with Hibernate 5.2.17 or later
• Oracle
• Postgres
• SQL Sever
• In theory any RDBMS that supports WITH RECURSIVE and sequences is supported.

Unfortunately these RDBMS are currently not supported

• MySQL due to the lack of sequence support

For the best possible performance the CACHE value of the database sequence should be set to the same value as the "fetch_size" parameter.

The project has been developed and tested against Hibernate 5.4.

The project has no dependencies other than Hibernate.

• https://vladmihalcea.com/2015/03/18/how-to-batch-insert-and-update-statements-with-hibernate/
• https://docs.jboss.org/hibernate/orm/5.0/manual/en-US/html/ch03.html#configuration-optional-properties
• https://vladmihalcea.com/2014/07/08/hibernate-identity-sequence-and-table-sequence-generator/
• https://dzone.com/articles/how-batch-insert-and-update