Re: [eclipselink-users] Ids not being used

[sonavor <jw@xxxxxxxxxxxxxx>]

I have also run into this problem.  I don't know if it is a problem or my
lack of understanding about the preallocated ids.  For now I have changed
the allocation size to 1.  I was thinking that using a higher value like the
default value of 50 would be more efficient (less times to read the ID
table).

In my situation I am using EclipseLink with Spring and a Struts application. 
My insert and update operations are only in a Spring business object and the
entity manager is provided by Spring through this configuration in the
Spring applicationContext.xml -

<!-- defines the JPA vendor adapter ... EclipseLink in this case -->
<bean id="vendorAdapter"
class="org.springframework.orm.jpa.vendor.EclipseLinkJpaVendorAdapter">
        <property name="databasePlatform"
value="org.eclipse.persistence.platform.database.MySQLPlatformPlatform" />
        <property name="showSql" value="true" />
</bean>

<!-- defines the datasource from an expected JNDI name provided by the
server -->
<jee:jndi-lookup id="dataSource" jndi-name="jdbc/cimdb" />

<!-- defines the JPA EntityManagerFactory and injects the defined datasource
-->
<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="jpaVendorAdapter" ref="vendorAdapter"/>
        <property name="dataSource" ref="dataSource" />
        <property name="jpaPropertyMap">
            <map>
                <entry key="eclipselink.jdbc.native-sql" value="true"/>
                <entry key="eclipselink.logging.level" value="FINEST"/>
                <entry key="eclipselink.logging.exceptions" value="true"/>
                <entry key="eclipselink.target-database" value="MYSQL"/>
                <entry key="eclipselink.weaving" value="static"/>
            </map>
        </property>
</bean>

Then in my Spring business objects the EntityManager is injected with a
method -
//EntityManager will be auto-injected due to @PersistenceContext
@PersistenceContext(unitName = "CiMJpaLibPU")
private EntityManager em;
public void setEntityManager(EntityManager em) {
        this.em = em;
}

Usage of the EntityManager in the Spring business class is then just like
this -

Query q = em.createNamedQuery("MediaResolution.findAll");
List<MediaResolution> rList = q.getResultList();

or in the case of an insert like this -

MediaListing ml = new MediaListing; // a JPA entity
(pseudo code) ml.<set various attributes>
em.persist(ml);

All of this works fine except that the generated primary keys jump by the
default count of 50 unless I set the allocation size smaller.  As I do here
-

@Id
@GeneratedValue(generator="MLTable")
@TableGenerator(name="MLTable", table="KEY_SEQUENCE",
            pkColumnName="KEY_SEQ_NAME", valueColumnName="KEY_INDEX",
            pkColumnValue="com.cim.jpa.MediaListing", allocationSize=1)
@Basic(optional = false)
@Column(name = "MEDIA_ID", nullable = false)
private Integer mediaId;

I have noticed that in the case of a OneToMany relationship that while
looping through and inserting the child records (i.e. media items for the
MediaListing JPA class) that the MediaItems JPA children do get primary key
values in increments of "1" even with the allocationSize set to the default
50.

The difference there is that the child records are being inserted at the
same time as the parent and are all in one transaction.  While the parent
inserts are always created in a new transaction.  Does that mean the Spring
framework is creating a new EntityManager for each transaction then?







James Sutherland wrote:
> 
> 50 is the default preallocation size, but all the preallocated ids should
> be used.  Are you creating a new EntityManagerFactory each time? Please
> include your config.
> 
> 
> 
> cl333r wrote:
>> 
>> Folks, a simple example, after I insert one or more entities into the
>> table the next id value starts with a 50 offset, and it happens every
>> time. Hence it looks like a lot of id values will never be used. Is it
>> true?
>> Is there a "wiser" way to "spend" id numbers (except the "identity"
>> solution)?
>> 
>> Using MySQL 5.0 on Ubuntu, JPA with EclipseLink. Happens for all
>> generation types except IDENTITY but can't use it because it lets me know
>> the ID of a newly created entity only after I commit it to the db.
>> 
> 
> 

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