ojb query question

[Jair da Silva Ferreira Júnior <j2...@amazon.com.br>]

Hi,
    I am using ojb1.0_rc5, ODMG api with OJB queries, mysql4 (innodb tables)
in Linux Red Hat 7.3 (kernel 2.4.20-20.7).
    How can I run a query that returns objects from a different class than
the class to search from? For example:

        class Person{
            int id;
            String name;

            //rest of the class ommited
        }

        class House{
            int id;
            String name;

            int ownerId;
            Person owner; //reference to Person

            //rest of the class ommited
        }

        The House class has a reference to the Person class.

        I want to build a query like this:
          Criteria c=new Criteria();
          c.addEqualTo("name","home");
          QueryByCriteria query=QueryFactory.newQuery(House.class,c);

          I want the query to return objects of the Person class using the
reference from House (owner atribute).
          Something like:
              query.setSelectAttribute("owner",true); //the true parameter
is to return distinct objects
                or
              broker.getCollectionByQuery(query,"owner",true);

          I looked for a similar method in OJB api and docs and couldn't
find one. Is there such a similar method or is there anyway I can achieve
the same result?

    I know that I can get House objects from the query and then get the
Person objects I need in a loop, but that would make performance suffer in
my scenario.
    Please, notice that I don't have a collection of Houses in Person
because that would also make performace suffer in my scenario.

    Any help would be appreciated.

Thanks,
    Jair Jr



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Re: ojb query question

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

hi jair,

if there's no reference from person to house you can't build a simple 
query. but you may use a query with a subquery. please have a look at 
QueryTest#testSubQuery4

hth
jakob

Jair da Silva Ferreira Júnior wrote:
> Hi,
>     I am using ojb1.0_rc5, ODMG api with OJB queries, mysql4 (innodb tables)
> in Linux Red Hat 7.3 (kernel 2.4.20-20.7).
>     How can I run a query that returns objects from a different class than
> the class to search from? For example:
> 
>         class Person{
>             int id;
>             String name;
> 
>             //rest of the class ommited
>         }
> 
>         class House{
>             int id;
>             String name;
> 
>             int ownerId;
>             Person owner; //reference to Person
> 
>             //rest of the class ommited
>         }
> 
>         The House class has a reference to the Person class.
> 
>         I want to build a query like this:
>           Criteria c=new Criteria();
>           c.addEqualTo("name","home");
>           QueryByCriteria query=QueryFactory.newQuery(House.class,c);
> 
>           I want the query to return objects of the Person class using the
> reference from House (owner atribute).
>           Something like:
>               query.setSelectAttribute("owner",true); //the true parameter
> is to return distinct objects
>                 or
>               broker.getCollectionByQuery(query,"owner",true);
> 
>           I looked for a similar method in OJB api and docs and couldn't
> find one. Is there such a similar method or is there anyway I can achieve
> the same result?
> 
>     I know that I can get House objects from the query and then get the
> Person objects I need in a loop, but that would make performance suffer in
> my scenario.
>     Please, notice that I don't have a collection of Houses in Person
> because that would also make performace suffer in my scenario.
> 
>     Any help would be appreciated.
> 
> Thanks,
>     Jair Jr
> 
> 
> 
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> 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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