Description of problem:
On the aplaws-ws3 branch, we added an AuditingObserver to ContentItem
by adding these two lines in the "initialize" method.         

m_audit_trail = BasicAuditTrail.retrieveForACSObject(this);
addObserver(new AuditingObserver(m_audit_trail));

Since every ContentItem will have a BasicAuditTrail, I wanted to find
a way to force the load in a single query like the old aggressive load
(e.g. when I load a ContentItem, it automatically loads the
BasicAuditTrail as well).  So, I thought that I could do this by
adding an association between ContentItem and BasicAuditTrail so in
ContentItem.pdl, in the "object type" definitely, I added this:
   BasicAuditTrail[0..1] auditTrail = join cms_items.item_id to
acs_auditing.object_id;

Once I compile with this once change in the pdl then various actions
cease to work (such as publishing and deleting).  For instance, when I
delete, I get this:

-*-*-*- Section: Stack trace -*-*-*-
com.redhat.persistence.engine.rdbms.RDBMSEngine$4: ORA-01407: cannot
update ("APLAWSWP3"."CMS_ITEMS"."ITEM_ID") to NULL

	at
com.redhat.persistence.engine.rdbms.RDBMSEngine.execute(RDBMSEngine.java:514)
	at
com.redhat.persistence.engine.rdbms.RDBMSEngine.execute(RDBMSEngine.java:430)
	at
com.redhat.persistence.engine.rdbms.RDBMSEngine.flush(RDBMSEngine.java:395)
	at com.redhat.persistence.Session.flushInternal(Session.java(Compiled
Code))
	at com.redhat.persistence.Session.flush(Session.java:562)
	at
com.arsdigita.persistence.DataObjectImpl.delete(DataObjectImpl.java:380)
	at com.arsdigita.domain.DomainObject.delete(DomainObject.java:324)
	at
com.arsdigita.cms.ui.folder.FolderBrowser$ItemDeleter.cellSelected(FolderBrowser.java:463)
	at com.arsdigita.bebop.Table.fireCellSelected(Table.java:238)
	at com.arsdigita.bebop.Table.respond(Table.java:538)
	at
com.arsdigita.cms.ui.folder.FolderBrowser.respond(FolderBrowser.java:204)
	at com.arsdigita.bebop.PageState.respond(PageState.java:367)


The queries leading up to the delete are:
-- ID: #280
-- Duration: 1ms
update cms_items
set type_id = null
where cms_items.item_id = '1477';


-- ID: #281
-- Duration: 2ms
update cms_items
set section_id = null
where cms_items.item_id = '1477';


-- ID: #282
-- Duration: 3ms
update cms_items
set item_id = null
where cms_items.item_id = '1477';


My guess is that because it is a 0..1 association it is trying to null
out the column.  However, since the column is actually the primary key
we are getting the error.  I would think that persistence should be
able to catch this situation and no try to execute the above query.

If I change the association to 1..1 and then in the initialize()
method I do:

       m_audit_trail = BasicAuditTrail.retrieveForACSObject(this);
        addObserver(new AuditingObserver(m_audit_trail));
        setAssociation("auditTrail", m_audit_trail);

Then when I create an item I get this:
com.redhat.persistence.engine.rdbms.RDBMSEngine$4: ORA-01400: cannot
insert NULL into ("APLAWSWP3"."CMS_ITEMS"."ITEM_ID")

	at
com.redhat.persistence.engine.rdbms.RDBMSEngine.execute(RDBMSEngine.java:514)
	at
com.redhat.persistence.engine.rdbms.RDBMSEngine.execute(RDBMSEngine.java:430)
	at
com.redhat.persistence.engine.rdbms.RDBMSEngine.flush(RDBMSEngine.java:395)
	at com.redhat.persistence.Session.flushInternal(Session.java(Compiled
Code))
	at com.redhat.persistence.Session.flush(Session.java:562)
	at com.redhat.persistence.Cursor.next(Cursor.java:107)
	at com.arsdigita.persistence.DataQueryImpl.next(DataQueryImpl.java:465)
	at com.arsdigita.cms.ContentBundle.getInstance(ContentBundle.java:295)
	at
com.arsdigita.cms.ContentBundle.getPrimaryInstance(ContentBundle.java:255)
	at com.arsdigita.cms.ContentBundle.beforeSave(ContentBundle.java:507)

with the last several queries being:

-- ID: #96
-- Duration: 3ms
insert into acs_objects
(object_type, object_id, display_name, default_domain_class)
values
('com.arsdigita.cms.contenttypes.Address', '1507', 'ffff',
'com.arsdigita.cms.contenttypes.Address');


-- ID: #97
-- Duration: 2ms
insert into vc_objects
(object_id, is_deleted)
values
('1507', 'false');


-- ID: #98
-- Duration: 2ms
insert into cms_items
(ancestors, version, name, language, item_id)
values
('1507/', 'draft', 'ffff', 'en', null);

Again, my guess is that it has something to do with the column being
used for the join being the same as the reference key.

Is this in fact a persistence bug?  Or is there a better way that we
can get the system to load the BasicAuditTrail and the ContentItem all
in the same query?  If we could eliminate the extra query or two for
each BasicAuditTrail there are pages that would have their number of
queries cut in half so this is relatively important to figure out from
a performance point of view.



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