EclipseLink very slow on inserting data - eclipselink

Question

I'm using the latest EclipseLink version with MySQL 5.5 (table type InnoDB). I'm inserting about 30900 records (which could be also more) at a time.
The problem is, that the insert performance is pretty poor: it takes about 22 seconds to insert all records (compared with JDBC: 7 seconds). I've read that using batch writing should help - but doesn't!?
#Entity
public class TestRecord {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
public Long id;
public int test;
}
The code to insert the records:
factory = Persistence.createEntityManagerFactory("xx_test");
EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
for(int i = 0; i < 30900; i++) {
TestRecord record = new TestRecord();
record.test = 21;
em.persist(record);
}
em.getTransaction().commit();
em.close();
And finally my EclipseLink configuration:
<persistence-unit name="xx_test" transaction-type="RESOURCE_LOCAL">
<class>com.test.TestRecord</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/xx_test" />
<property name="javax.persistence.jdbc.user" value="root" />
<property name="javax.persistence.jdbc.password" value="test" />
<property name="eclipselink.jdbc.batch-writing" value="JDBC" />
<property name="eclipselink.jdbc.cache-statements" value="true"/>
<property name="eclipselink.ddl-generation.output-mode" value="both" />
<property name="eclipselink.ddl-generation" value="drop-and-create-tables" />
<property name="eclipselink.logging.level" value="INFO" />
</properties>
</persistence-unit>
What I'm doing wrong? I've tried several setting, but nothing seems the help.
Thanks in advance for helping me! :)
-Stefan
Another thing is to add ?rewriteBatchedStatements=true to the data URL used by the connector.
This caused executing about 120300 inserts down to about 30s which was about 60s before.

Answer 1

JDBC Batch writing improves performance drastically; please try it
Eg: property name="eclipselink.jdbc.batch-writing" value="JDBC"

Answer 2

#GeneratedValue(strategy = GenerationType.IDENTITY)
Switch to TABLE sequencing, IDENTITY is never recommended and a major performance issue.
See,
http://java-persistence-performance.blogspot.com/2011/06/how-to-improve-jpa-performance-by-1825.html
I seem to remember that MySQL may not support batch writing without some database config as well, there was another post on this, I forget the url but you could probably search for it.

Answer 3

Probably the biggest difference besides the mapping conversion is the caching. By default EclipseLink is placing each of the entities into the persistence context (EntityManager) and then during the finalization of the commit it needs to add them all to the cache.
One thing to try for now is:
measure how long an em.flush() call takes after the loop but before the commit. Then if you want you could call em.clear() after the flush so that the newly inserted entities are not merged into the cache.
Doug