Repeated updates on EVENT table, in Hibernate one to many mapping

[Kumar Raja]

Hi All,

I have an Event.hbm.xml

<hibernate-mapping>
    <class name="org.learning.hibernate.Event" table="EVENT">
        <id name="id">
            <column name="EVENT_ID" />
            <generator class="native" />
        </id>
        <property name="title" type="java.lang.String">
            <column name="EVENT_TITLE" />
        </property>
        <property name="date" type="timestamp">
            <column name="EVENT_DATE" />
        </property>
    </class>
</hibernate-mapping>

Person.hbm.xml

<set name="events" table="PERSON_EVENT" cascade = "all">
            <key>
                <column name="PERSON_ID" />
            </key>
            <many-to-many class="org.learning.hibernate.Event" column = "EVENT_ID" unique = "true"/>
        </set>

The above examples are taken from associations.

I populated Events and Persons and now trying to add an event to Person in two different unit of works, as the example given in link, only that I changed the query.

      
//begin transaction
//        Person aPerson = (Person) session
//                .createQuery("select p from Person p left join fetch p.events where p.id = :pid")
//                .setParameter("pid", personId)
//                .uniqueResult(); // Eager fetch the collection so we can use it detached
        
        Person aPerson = (Person) session
                .createQuery("select p from Person p where p.id = :pid")
                .setParameter("pid", personId)
                .uniqueResult(); // Eager fetch the collection so we can use it detached
        Event anEvent = (Event) session.load(Event.class, eventId);

// commit transaction
// End of first unit of work

aPerson.getEvents().add(anEvent); // aPerson (and its collection) is detached

// Begin second unit of work
// obtain new session and begin transaction
session.update(aPerson); // Reattachment of aPerson
//Commit transaction and close session.

Now I'm trying to associate person and events as below (Assume that addEventsToPersons has the above logic)

em.addEventsToPersons(1,1);
em.addEventsToPersons(1,2);
em.addEventsToPersons(1,3);
em.addEventsToPersons(1,4);

The association is working fine, but what I noticed is the below sequence of SQL

Hibernate: select person0_.PERSON_ID as PERSON1_1_, person0_.PERSON_FNAME as PERSON2_1_, person0_.PERSON_LNAME as PERSON3_1_, person0_.PERSON_PHONE as PERSON4_1_ from LEARN.PERSON person0_ where person0_.PERSON_ID=?
Hibernate: select events0_.PERSON_ID as PERSON1_1_1_, events0_.EVENT_ID as EVENT2_1_, event1_.EVENT_ID as EVENT1_0_0_, event1_.EVENT_TITLE as EVENT2_0_0_, event1_.EVENT_DATE as EVENT3_0_0_ from LEARN.PERSON_EVENT events0_ inner join LEARN.EVENT event1_ on events0_.EVENT_ID=event1_.EVENT_ID where events0_.PERSON_ID=?
Hibernate: update LEARN.PERSON set PERSON_FNAME=?, PERSON_LNAME=?, PERSON_PHONE=? where PERSON_ID=?
Hibernate: delete from LEARN.PERSON_EVENT where PERSON_ID=?
Hibernate: insert into LEARN.PERSON_EVENT (PERSON_ID, EVENT_ID) values (?, ?)

Hibernate: select person0_.PERSON_ID as PERSON1_1_, person0_.PERSON_FNAME as PERSON2_1_, person0_.PERSON_LNAME as PERSON3_1_, person0_.PERSON_PHONE as PERSON4_1_ from LEARN.PERSON person0_ where person0_.PERSON_ID=?
Hibernate: select events0_.PERSON_ID as PERSON1_1_1_, events0_.EVENT_ID as EVENT2_1_, event1_.EVENT_ID as EVENT1_0_0_, event1_.EVENT_TITLE as EVENT2_0_0_, event1_.EVENT_DATE as EVENT3_0_0_ from LEARN.PERSON_EVENT events0_ inner join LEARN.EVENT event1_ on events0_.EVENT_ID=event1_.EVENT_ID where events0_.PERSON_ID=?
Hibernate: update LEARN.PERSON set PERSON_FNAME=?, PERSON_LNAME=?, PERSON_PHONE=? where PERSON_ID=?
Hibernate: update LEARN.EVENT set EVENT_TITLE=?, EVENT_DATE=? where EVENT_ID=?
Hibernate: insert into LEARN.PERSON_EVENT (PERSON_ID, EVENT_ID) values (?, ?)

Hibernate: select person0_.PERSON_ID as PERSON1_1_, person0_.PERSON_FNAME as PERSON2_1_, person0_.PERSON_LNAME as PERSON3_1_, person0_.PERSON_PHONE as PERSON4_1_ from LEARN.PERSON person0_ where person0_.PERSON_ID=?
Hibernate: select events0_.PERSON_ID as PERSON1_1_1_, events0_.EVENT_ID as EVENT2_1_, event1_.EVENT_ID as EVENT1_0_0_, event1_.EVENT_TITLE as EVENT2_0_0_, event1_.EVENT_DATE as EVENT3_0_0_ from LEARN.PERSON_EVENT events0_ inner join LEARN.EVENT event1_ on events0_.EVENT_ID=event1_.EVENT_ID where events0_.PERSON_ID=?
Hibernate: update LEARN.PERSON set PERSON_FNAME=?, PERSON_LNAME=?, PERSON_PHONE=? where PERSON_ID=?
Hibernate: update LEARN.EVENT set EVENT_TITLE=?, EVENT_DATE=? where EVENT_ID=?
Hibernate: update LEARN.EVENT set EVENT_TITLE=?, EVENT_DATE=? where EVENT_ID=?
Hibernate: insert into LEARN.PERSON_EVENT (PERSON_ID, EVENT_ID) values (?, ?)

Hibernate: select person0_.PERSON_ID as PERSON1_1_, person0_.PERSON_FNAME as PERSON2_1_, person0_.PERSON_LNAME as PERSON3_1_, person0_.PERSON_PHONE as PERSON4_1_ from LEARN.PERSON person0_ where person0_.PERSON_ID=?
Hibernate: select events0_.PERSON_ID as PERSON1_1_1_, events0_.EVENT_ID as EVENT2_1_, event1_.EVENT_ID as EVENT1_0_0_, event1_.EVENT_TITLE as EVENT2_0_0_, event1_.EVENT_DATE as EVENT3_0_0_ from LEARN.PERSON_EVENT events0_ inner join LEARN.EVENT event1_ on events0_.EVENT_ID=event1_.EVENT_ID where events0_.PERSON_ID=?
Hibernate: update LEARN.PERSON set PERSON_FNAME=?, PERSON_LNAME=?, PERSON_PHONE=? where PERSON_ID=?
Hibernate: update LEARN.EVENT set EVENT_TITLE=?, EVENT_DATE=? where EVENT_ID=?
Hibernate: update LEARN.EVENT set EVENT_TITLE=?, EVENT_DATE=? where EVENT_ID=?
Hibernate: update LEARN.EVENT set EVENT_TITLE=?, EVENT_DATE=? where EVENT_ID=?
Hibernate: insert into LEARN.PERSON_EVENT (PERSON_ID, EVENT_ID) values (?, ?)

As you notice, the number of times I'm trying to add events to persons, the execution of Hibernate: update LEARN.EVENT set EVENT_TITLE=?, EVENT_DATE=? where EVENT_ID=? is increasing.

and also, why Hibernate: delete from LEARN.PERSON_EVENT where PERSON_ID=? for the first association. Why should the record be deleted and then added back again.

Please advise.
is being executed m

[Kumar Raja]

Any thoughts on this question