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 Post subject: merge causes unecessary update with <version>
PostPosted: Fri Jul 23, 2010 9:10 am 
Newbie

Joined: Fri Jul 23, 2010 9:00 am
Posts: 1
Hello,
using Hibernate 3.5.2-Final.
The problem (i believe it's a bug) is that hibernate will cause an update to the version when using merge, even when the object has not changed. The issue occurs when replacing a Set reference with a new HashSet in the loaded object.

Here is the mapping to test:
Code:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="scanserver.util.hibernate.tests">
  <class name="GroupTest" table="groups" lazy="false" dynamic-update="true">
    <id column="id" name="id">
      <generator class="native"/>
    </id>
    <version column="version" name="version"/>
    <property name="name"/>
  </class>

  <class name="UserTest" table="users" lazy="false" dynamic-update="true">
    <id column="id" name="id"><generator class="native"/></id>
    <version column="version" name="version"/>
    <property name="userName"/>
    <property name="name"/>
    <set cascade="merge,save-update" fetch="join" name="Groups" table="usersgroups">
      <key column="UserID"/>
      <many-to-many class="GroupTest" column="GroupID"/>
    </set>
  </class>
</hibernate-mapping>


Here is the code to reproduce:
Code:
    Session s = getSession();
    s.beginTransaction();
    UserTest u = (UserTest)s.load(UserTest.class, 1);
    s.getTransaction().commit();
    s.close();
   
    //this is the line that causes the problem
    u.setGroups(new HashSet(u.getGroups()));

    s = getSession();
    s.beginTransaction();
    s.merge(u);
    s.getTransaction().commit();
    s.close();


Hibernate executes the following SQL:
Code:
Hibernate:
    update
        users
    set
        version=?
    where
        id=?
        and version=?

Obviously, there is nothing to update here apart from the version!
If the line that replaces the Set is omited, then this update does not occur.

Costas


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