Hi ya,

we have a simple parent child situation - where we want to have children ordered in specific order. For this we have children defined in a list and have defined an integer index column.

Everything works ok - except if we add constraint to the database to the index column to be NOT NULL. While debugging what Hibernate does I noticed following:

1) insert into nodes (title, state, parent_id, owner_group_id, id) values (?, ?, ?, ?, ?)

2) Hibernate: update nodes set parent_id=null, position=null where parent_id=? and position=?

3) Hibernate: update nodes set parent_id=?, position=? where id=?

I don't get it why Hibernate does the step 2 and is there anything that can be done.

Any pointers would be appreciated.

Hibernate version:

2.1.3

Mapping documents:

<class name="fi.hy.sitetree.Node" table="nodes" >

<cache usage="transactional"/>

<id name="id" column="id" type="long" unsaved-value="0">
<generator class="sequence">
<param name="sequence">node_seq</param>
</generator>
</id>

<many-to-one name="parent" class="fi.hy.sitetree.Node" column="parent_id" not-null="true" />

<list name="children" lazy="true" cascade="delete" inverse="true">
<cache usage="transactional"/>
<key column="parent_id" />
<index column="position" type="int" not-null="true" />
<one-to-many class="fi.hy.sitetree.Node" />
</list>

CREATE TABLE nodes (
ID NUMBER PRIMARY KEY,
title VARCHAR(255),
parent_id NUMBER REFERENCES nodes (ID) ON DELETE CASCADE,
state INTEGER DEFAULT 0,
position INTEGER DEFAULT 0 NOT NULL,
owner_group_id NUMBER REFERENCES principal_groups (ID)
-- CONSTRAINT parent_position UNIQUE (parent_id, position)
);

public class Node {

public static final String NODE_NAME = "Node";

private long id;
private String title;
private NodeState state;
private Node parent;
private List children;
private PrincipalGroup group;

public void addChild(Node child) {
if (children == null) {
children = new Vector();
}
child.setParent(this);
children.add(child);
}

...

}

Name and version of the database you are using:

Oracle 8

The generated SQL (show_sql=true):

insert into nodes (title, state, parent_id, owner_group_id, id) values (?, ?, ?, ?, ?)

Hibernate: update nodes set parent_id=null, position=null where parent_id=? and position=?

Hibernate: update nodes set parent_id=?, position=? where id=?

When trying to do a testcase that would produce the same behaviour in minimal enviroment, I noticed that this behaviour seems to be caused by Spring framework's HibernateTemplate. Not just Hibernate.

http://forum.springframework.org/viewto ... =5351#5351

Chapter 9. Parent Child Relationships in manual

hth

Did not really help, since that was already used as a base.

However for now we will circumvent the problem by setting constraint initially deferred, which prevents it to be checked untill transaction ends.