Re: [OJB-developers] n:m-Mapping with Extent

[<Joa...@tp...>]

Hy,

I've already done what you suggested (rebuild a new query), but it was a
very ugly hack, as I didn't know where to put it and how to do it properly
( I don't even want to mention were I did it ;-). It broke some other tests
'though and I decided to do a clean approach, rather then debug this ugly
piece of code that I produced. At least I saw that extents in combination
with MtoN-mappings are possible. Is it possible to provide
QueryByMtoNCriteria with the necessary information to rebuild itself for a
specific extent-class/table? I think that would be somewhat nicer.

regards
Joachim Sauer



                                                                                                                                              
                    "Jakob                                                                                                                    
                    Braeuchi"            An:     <obj...@li...>, <Joa...@tp...>                 
                    <jbraeuchi@ho        Kopie:                                                                                               
                    tmail.com>           Thema:  Re: [OJB-developers] n:m-Mapping with Extent                                                 
                                                                                                                                              
                    30.04.2002                                                                                                                
                    09:08                                                                                                                     
                                                                                                                                              
                                                                                                                                              



hi joachim,

as you mentioned the problem is the wrong table in from- and where-clause
coming from prebuilt MtoNQuery.
the second problem is getPreparedSelectStatement() in SqlGenerator: for
MtoNQQueries tables are taken from the query and NOT from
the ClassDescriptor, the query still pointing to the tables of the base
class instead of the extent. the same is true for the EqualToColumnCriteria
in the query.

i think when using extents there is always a mismatch between the query and
the class descriptor but it only hurts with MtoNQuery.
it may be the best thing to build a new query based on the original one for
the extents and then to execute this query.
what do you think ?

jakob


----- Original Message -----
From: <Joa...@tp...>
To: <obj...@li...>
Sent: Monday, April 29, 2002 3:04 PM
Subject: [OJB-developers] n:m-Mapping with Extent


> Hy,
>
> it's me again. I've finally hunted down the bug. Let me explain the
> scenario:
>
> I've got a class OneSide. Each object can have one or more ManySide
> objects. This is implemented via a List with coresponding
> CollectionDescriptor using a association-table (non-decomposed
N:M-Mapping
> in OJB-speak). Additionally there is a class named ManySideExtent, that
> extends ManySide and is mapped to another table.
>
> When I enable debugging in SqlGenerator I'll find the following messages
> (after many others)  when loading a OneSide object:
>
> [ojb.broker.accesslayer.SqlGenerator] DEBUG: SQL: SELECT
> manyside.id,manyside.value FROM manyside, oneside_manyside WHERE
> (oneside_id= ? )  AND oneside_manyside.manyside_id=manyside.id
>
> this one looks quite correct and gets me the correct results (all
ManySide
> objects that belong to the one OneSide object), but the next one (which
> tries to load the ManySideExtent objects) fails:
>
> [ojb.broker.accesslayer.SqlGenerator] DEBUG: SQL: SELECT
> manyside_extent.id,manyside_extent.value,manyside_extent.another_value
FROM
> manyside, oneside_manyside WHERE (oneside_id= ? )  AND
> oneside_manyside.manyside_id=manyside.id
>
> the problem here obviously is, that the wrong table is used in the
> FROM-clause and the WHERE-clause. These come from the Query object, that
is
> created by the PersistenceBrokerImpl in getMtoNQuery. I think calling
> getMtoNQuery with the ClassDescriptor of ManySideExtent for the second
> query would solve the problem, the problem is, that the query is not
built
> in the function that decides wether we need to query for extents ...
>
> Maybe a correct solution would be somewhere else altogether, but I don't
> know enough about the system to see where.
>
> regards
> Joachim Sauer
>
>
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