[Re-post] PB query question

[Phil Warrick <ph...@mcgill.ca>]

Hi again,

I posted this a few weeks ago, perhaps when the best person to answer
wasn't around (Jakob?).  Your suggestions would be welcome.


Here is my model:

[A] <1--n> [B] <1--n> [C] <1--1> [D]
                         | |
                        C1 C2

I want to query for A objects using a C1 timestamp field as criteria (C1
is a subclass of C and C does not have the timestamp field) and a D
string field as criteria.

If the timestamp field belonged to the C class, then there would be no
problem directly querying for A's.

Since the criteria is a C1 attribute I don't think that I can directly
query for A's, so I can do it in two steps by first querying for C1
objects and then iterating through the returned collection to gather the
A objects, as follows

// snippit begin
Criteria criteria1 = new Criteria();
Criteria criteria2 = new Criteria();
criteria1.addEqualTo("d.stringField", new String("foo"));
criteria2.addEqualTo("d.stringField", new String("foofoo"));
criteria1.addOrCriteria(criteria2);
			
Criteria criteria3 = new Criteria();
criteria3.addBetween("timeStamp", timeStamp1, timeStamp2);
			
criteria1.addAndCriteria(criteria3);

Query query = new QueryByCriteria(C1.class, criteria1);
Collection c1Set = broker.getCollectionByQuery(query);

java.util.Iterator itr = c1Set.iterator();
List aList = new ArrayList();
while (itr.hasNext())
{
      // gather the A's (more db hits here)
      A a = c1.getB().getA();
      aList.add(a);
}
// snippit end

It would be nice to reduce the DB hits and query for the A's directly as
is possible in with standard OQL:

select c1.b.a from c1 in C1.class
	where (c1.d.stringField = \"foo\" or
                  c1.d.stringField = \"foofoo\") and
	e.theTimestamp >= timestamp '" + timeStamp1 + "' " and
           e.theTimestamp <= timestamp '" + timeStamp2 + "' "

Is there any possibility that this is possible with PB queries?

Thanks for read this far,

Phil




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Re: [Re-post] PB query question

[Jakob Braeuchi <jb...@gmx.ch>]

hi phil,

there have been discussions about defining the fields of the subclasses 
in the abstract base class as well. but i do not know the current state :(
you could try to use a path hint (setPathForClass) but this could 
conflict with the other extent .

jakob

Phil Warrick wrote:

> Hi again,
>
> I posted this a few weeks ago, perhaps when the best person to answer
> wasn't around (Jakob?).  Your suggestions would be welcome.
>
>
> Here is my model:
>
> [A] <1--n> [B] <1--n> [C] <1--1> [D]
>                         | |
>                        C1 C2
>
> I want to query for A objects using a C1 timestamp field as criteria (C1
> is a subclass of C and C does not have the timestamp field) and a D
> string field as criteria.
>
> If the timestamp field belonged to the C class, then there would be no
> problem directly querying for A's.
>
> Since the criteria is a C1 attribute I don't think that I can directly
> query for A's, so I can do it in two steps by first querying for C1
> objects and then iterating through the returned collection to gather the
> A objects, as follows
>
> // snippit begin
> Criteria criteria1 = new Criteria();
> Criteria criteria2 = new Criteria();
> criteria1.addEqualTo("d.stringField", new String("foo"));
> criteria2.addEqualTo("d.stringField", new String("foofoo"));
> criteria1.addOrCriteria(criteria2);
>            
> Criteria criteria3 = new Criteria();
> criteria3.addBetween("timeStamp", timeStamp1, timeStamp2);
>            
> criteria1.addAndCriteria(criteria3);
>
> Query query = new QueryByCriteria(C1.class, criteria1);
> Collection c1Set = broker.getCollectionByQuery(query);
>
> java.util.Iterator itr = c1Set.iterator();
> List aList = new ArrayList();
> while (itr.hasNext())
> {
>      // gather the A's (more db hits here)
>      A a = c1.getB().getA();
>      aList.add(a);
> }
> // snippit end
>
> It would be nice to reduce the DB hits and query for the A's directly as
> is possible in with standard OQL:
>
> select c1.b.a from c1 in C1.class
>     where (c1.d.stringField = \"foo\" or
>                  c1.d.stringField = \"foofoo\") and
>     e.theTimestamp >= timestamp '" + timeStamp1 + "' " and
>           e.theTimestamp <= timestamp '" + timeStamp2 + "' "
>
> Is there any possibility that this is possible with PB queries?
>
> Thanks for read this far,
>
> Phil
>
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: ojb-user-unsubscribe@db.apache.org
> For additional commands, e-mail: ojb-user-help@db.apache.org
>
>


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