Re: [OJB-developers] OQL bug

[Georg S. <ge...@me...>]

Hi,

I thought a little bit about my last posting and of course the thing I did
was quite stupid since interfaces can not have fields. The query would
have to be
select allX from X where sequence.getSomeField() = $1

I do not know if this is correct OQL and even then it would be a
performance problem because the query engine would have to load each
object to invoke the method.

Anyway let me explain why I even got to that problem.
I actually wanted to do something like this:
select allX from X where sequence= $1

sequence is a reference field that holds an interface of type Sequence.

Please correct me if this is not possible in OQL, but I thought that I
could pass in an object when binding. My problem was that I passed in an
object which is loaded with dynamic proxy turned on. The query engine than
threw an error that it did not know a class $Proxy2. Somehow the engine
should substitute the actual interface or object for the proxy.

regards

Georg

On Fri, 8 Mar 2002, Georg Schneider wrote:

> Hi,
>
> when something similar as the following OQL-Query
>
> select allX from X where sequence.somefield = $1 ....
>
> where the sequence field is actually an interface I get a
> NullPointerException:
>
> java.lang.NullPointerException
>         at
> ojb.broker.metadata.ClassDescriptor.getPkFields(ClassDescriptor.java:869)
>         at
> ojb.broker.accesslayer.SqlGenerator$JoinInfo.asSqlClause(SqlGenerator.java:66)
>         at
> ojb.broker.accesslayer.SqlGenerator.getJoinClause(SqlGenerator.java:914)
>         at
> ojb.broker.accesslayer.SqlGenerator.getPreparedSelectStatement(SqlGenerator.java:685)
>         at
> ojb.broker.accesslayer.JdbcAccess.executeQuery(JdbcAccess.java:186)
>         at ojb.broker.accesslayer.RsIterator.<init>(RsIterator.java:179)
>         at
> ojb.broker.singlevm.PersistenceBrokerImpl.getIteratorFromQuery(PersistenceBrokerImpl.java:1181)
>         at
> ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBrokerImpl.java:901)
>         at
> ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBrokerImpl.java:986)
>         at
> ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBrokerImpl.java:958)
>         at ojb.odmg.oql.OQLQueryImpl.execute(OQLQueryImpl.java:229)
>
>
> I looked a little bit around and the problem seems to be in the inner
> class JoinInfo in SqlGenerator which tries to do the following
>
>             refCld =
> aCld.getRepository().getDescriptorFor(anOrd.getItemClass());
>
>
> anOrd.getItemClass() of course is an interface which as a Descriptor
> doesn't have any fields. I suppose the interface would have to be
> substituted somehow by the actual classes implementing that interface and
> maybe this would mean having to do various actual SQL-Queries each with a
> concrete class and then somehow merging the result, or doing an
> (outer) join over all the concrete class tables involved and then somehow
> postprocessing the result again.
>
> regards
>
> Georg
>
>
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