Re: How to pass dynamic attribute values to QueryCustomizerImplementations

[Guido Beutler]

Hello,

for a more detailed description pleas look at my other mail.
Daniel Perry wrote:
I am still confused by this too.
 

sorry!

Say i have a 1:n mapping between Manager and Employee.
I want to query using ODMG to say
"select all Managers (and their Employees) where Manager.department=blah AND
Employee.status=fulltime"
 

OK then you get a filled collection with all fulltime Employee in there.

I did this using a query customizer for static queries (eg
Employee.deleted=false).
I never worked out how to do dynamicly though.  My (bodge) solution was to
load the Managers with all their Employees, and then remove any Employees
from the collection that didnt match my criteria.
 

You're right but lets say youre loading >17000 Employees, this may tke a 
while ;-)
I already know that I would need only 1 to 5 so removing them would work 
but not really is a solution (in my case).

I can see an obvious problem with this querying - if you materialise a
Manager, all Employees relating to it should be materialised, as say for
example you do a markDirty on the Manager object matching the above
criteria, all the Employees not matching status=fulltime would not be in the
collection when it's written, so would be lost.
Still, for read only (eg web interfaces like JSP using taglibs) it would be
very useful to be able to do these queries.
 

Yes, I'm only doing selects and for performance of my application this 
would be _very_ usefull.
For me OJB needs >30s to build the collection

best regards,

Gudio

Daniel.

----- Original Message ----- 
From: "Brian McCallister" <[EMAIL PROTECTED]>
To: "OJB Users List" <[EMAIL PROTECTED]>
Sent: Friday, December 19, 2003 3:27 PM
Subject: Re: How to pass dynamic attribute values to
QueryCustomizerImplementations

 

Saw your original message and am thinking about this one.

Any chance you can post specifics?

Does value need to change while running, or is it just dependent upon
something at load time?
-Brian

On Fri, 2003-12-19 at 10:09, Guido Beutler wrote:
   

Hello,

This is a repost with a better subject, hoping to get a hint.

I build a custom QueryCustomizer implementation to restrict the
retrieved values of a collection to a known primary key.
I saw that I could add attributes at the deployment descriptor but the
value of the
primary key changes dynamically during my application.
My sample:

  public Query customizeQuery(Object anObject, PersistenceBroker
aBroker, CollectionDescriptor aCod, QueryByCriteria aQuery)
  {
     aQuery.getCriteria().addEqualTo("field","value");
      return aQuery;
  }
The "value" should change dynamically. Is there really no way to pass
additional dynamic arguments to the implementation?
IA Simple workaround is to use System properties but of course this just
a hack for a test case. It's not thread save, it's slow
etc.
I found no way to find out where the current query came from to build
sonething like a callback. Extending the Query implementation by
a user object would be a solution buit this modification shouldn't be
done without consulting the OJB crew.
Implementing a user object might be difficult because the querry which
is passed to the QueryCustomizer  is generated by OJB and is
not directly coming from my code. So a modified Query would mean that
the user object must be passed around by OJB Broker.
I still think that I miss something.
best regards,

Guido

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