Creating custom mappings between objects

Question

I currently have a db schmea that supports "soft" deletes. Example:
Client table has fields:
id - primary key (number)
name - varchar
active ("Y" or "N" where "Y" means active and "N" means "INACTIVE")
We also have a table Users:
id - primary key (number)
name - varchar
active ("Y" or "N" where "Y" means active and "N" means "INACTIVE")
When I delete a user I want to set its active field to "N" and then when
someone reads users from the client (after I have saved my changes) I want
only users whoses active field is "Y" to be returns, i.e.
Client clientA = <read client A>
Collection users = clientA.getUsers();
Is there a way to configure/customize the mapping/relationship between
objects?
Thanks!
Bruce

Answer 1

All of the emails are really my way of getting a soft delete to work. Does
KODO support this feature or is their a standard work around to support
this feature?
Thanks!
Bruce
Alex Roytman wrote:
You could break you collection into multiple mutually exclusive
subcollections (like active/inactive) and have your object model to map them
separately (via views with mutually exclusive criterion) When changing a
collection member's status you will need to move it from active collection
to inactive. Complete collection can be dode as dybamic (delegating)
composition of the subcollections (but it will cost twice as much to fetch
it)
Try to resolve your issues on object model level. I believe altering sql
mappings to make them very fancy will cause you lots of grief in the long
run
"Bruce" <[email protected]> wrote in message
news:[email protected]...
I also want to do something similiar to support object history. I could
have a Client object which gets modified and instead of editing this
object I would copy it, inactivate the copy and then edit the original.
This allows for full history. I can always select by active (or a more
complicated status) to get the rest of the history instead of the "top".
Views here seems like a hack. I have activew fields in all of my tables so
I would nee views for each table which is a lot to manage if fields are
changing (need to change them in both places). Also this creates issues
since views are really read-only.
Isn't there a way to change the SQL used to read a relationship?
Bruce
Alex Roytman wrote:
map your classes against views with (where active = 'Y') to make sure
"soft
deleted" records do not get read and have your object model to handlesoft
deletes (like removing from collections etc) use helper methods to do"soft
deletes" masking real deletes is not good idea - you will need them atsome
point
"Stephen Kim" <[email protected]> wrote in message
news:[email protected]...
While there is nothing default that does particularly what you desire,
but from my perspective, you should not have Kodo do anything by
default
as you will probably want to delete the inactive instances at somelater
point.
Instead you should look into Query.setCandidates:
http://www.solarmetric.com/Software/Documentation/2.4.3/docs/jdo-javadoc/jav
ax/jdo/Query.html
i.e. public Collection getActiveUsers ()
PersistenceManager pm = JDOHelper.getPersistenceManager
(this);
Query q = pm.newQuery (User.class, true);
q.setFilter ("active == "N"");
q.setCandidates (users);
return q.execute ();
I haven't tested the above code and there are a lot of optimizations
you
could do such as caching the query in a transient collection but Ithink
you get the idea.
You may want to post your thoughts on our newsgroups
(news://news.solarmetric.com) and see how other people are tackling
similar probles..
Bruce wrote:
I currently have a db schmea that supports "soft" deletes. Example:
Client table has fields:
id - primary key (number)
name - varchar
active ("Y" or "N" where "Y" means active and "N" means "INACTIVE")
We also have a table Users:
id - primary key (number)
name - varchar
active ("Y" or "N" where "Y" means active and "N" means "INACTIVE")
When I delete a user I want to set its active field to "N" and then
when
someone reads users from the client (after I have saved my changes)I
want
only users whoses active field is "Y" to be returns, i.e.
Client clientA = <read client A>
Collection users = clientA.getUsers();
Is there a way to configure/customize the mapping/relationship
between
objects?
Thanks!
Bruce
Stephen Kim
[email protected]
SolarMetric, Inc.
http://www.solarmetric.com