Hibernate - Slow batch insert

Question

The following is my code for batch inserting to MySQL remote database.

    Session session = db.setSession();
    Transaction tx = session.beginTransaction();

    for ( int i=0; i<e.getContents().size(); i++ ) {
        Content content = e.getContents().get(i);
        session.save(content);
        if ( i % 40 == 0 ) { 
            session.flush();
            session.clear();
        }
    }
    tx.commit();

The mapping is defined in the following way:

class name="Database.Content" table="..." schema="" catalog="...">
    <id name="id">
        <column name="id" sql-type="int" not-null="true"/>
        <generator class="identity"/>
    </id>
    <property name="week">
        <column name="week" sql-type="int"/>
    </property>
    <property name="type">
        <column name="type" sql-type="int" not-null="true"/>
    </property>
    <many-to-one name="group" class="Database.Group">
        <column name="`group`"/>
    </many-to-one>
    <many-to-one name="table" class="Database.Table">
        <column name="`table`" not-null="true"/>
    </many-to-one>
</class>

I also set up some properties in hibernate.cfg.xml :

<property name="hibernate.jdbc.batch_size">40</property>
<property name="hibernate.cache.use_second_level_cache">false</property>

Unfortunately, the insertion of 150 rows takes about 30 seconds, which is very slow. I have read that setting generator=identity may disable batch inserting completely. However, if I remove the generator line, I end up with getting Duplicate key error. I wonder if I could send null as my id , so MySQL will do the job.

What is the best way to optimise the query? Thanks.

Answer 1

As answered in this SO question identity will indeed not work for batch. For MySQL you end up either generating ids in an application (fe with generator assigned or uuid - Hibernate-specific) or employing JPA-compliant table generator.

Example of using table generator:

<table-generator name="EMP_GEN"
        table="GENERATOR_TABLE"
        pk-column-name="key"
        value-column-name="hi"
        pk-column-value="EMP"
        allocation-size="20"/>

See details on http://docs.jboss.org/hibernate/orm/4.3/manual/en-US/html_single/#mapping-declaration-id . There is also a description of what parameter mean on Java EE page .