Re: Hierarchical relationship problems

From: Filip Balas (fbala..mail.com)
Date: Mon Apr 25 2005 - 16:47:43 EDT

  • Next message: Andrus Adamchik: "Re: Hierarchical relationship problems"

    I'm on the bleeding edge (could be why I'm having the
    problem) cayenne 1.2M3.

    Filip

    On 4/25/05, Andrus Adamchik <andru..bjectstyle.org> wrote:
    > You shouldn't have to do anything special. Cayenne (including the Modeler)
    > works fine with simple parent-child hierarchies. For "children" I expect
    > the generated query to look even simpler:
    >
    > SELECT t0.description, t0.id, t0.parent_id
    > FROM dbo.IMV_locations t0, dbo.IMV_locations t1
    > WHERE t0.parent_id = ? [bind: 1]
    >
    > So ... What version of Cayenne do you have? There was a bug long time ago
    > that messed it up, but I am fairly sure it is fixed in 1.1 final and 1.1.1
    > releases.
    >
    > Andrus
    >
    >
    > > Hi Andrus,
    > >
    > > Yes that makes perfect sense. I didn't catch that error, I just
    > > assumed the modeler would generate the right xml when
    > > I selected the proper source and target.
    > >
    > > However, even when I corrected the xml manually to your
    > > suggestion, I still have the following statement generated
    > > by cayenne:
    > >
    > > SELECT t0.description, t0.id, t0.parent_id
    > > FROM dbo.IMV_locations t0, dbo.IMV_locations t1
    > > WHERE t0.parent_id = t1.id AND (t1.parent_id = ?) [bind: 1]
    > >
    > > I need it to read:
    > >
    > > SELECT t0.description, t0.id, t0.parent_id
    > > FROM dbo.IMV_locations t0, dbo.IMV_locations t1
    > > WHERE t0.parent_id = t1.id AND (t1.id = ?) [bind: 1]
    > >
    > > In another spot in my code I have a hierarchy set up but
    > > it is a many to many (map, not tree) and cayenne seems
    > > to deal with that beautifully. To achieve this I have an intermediate
    > > table that maps locations to one another. Will I have to add
    > > this extra table with a one-To-one constraint to ensure a tree
    > > structure and not a map?
    > >
    > > Thanks to all who have answered.
    > > Your help is greatly appreciated.
    > > Filip
    > >
    > >
    > >
    > > On 4/24/05, Andrus Adamchik <andru..bjectstyle.org> wrote:
    > >> Hi Filip,
    > >>
    > >> > <obj-relationship name="children" source="Location"
    > >> target="Location" deleteRule="Cascade"
    > >> > db-relationship-path="rel_children.rel_children"/>
    > >> >
    > >> > <obj-relationship name="parent" source="Location" target="Location"
    > >> db-relationship-path="rel_parent.rel_parent"/>
    > >>
    > >> The way relationships above are mapped you'll be getting GRANDchildren
    > >> and GRANDparents. Is this really what you want? The query you quote
    > >> seems correct (for grandchildren). What I mean is that
    > >>
    > >>
    > >> > SELECT t0.description, t0.id, t0.parent_id
    > >> > FROM dbo.IMV_locations t0, dbo.IMV_locations t1
    > >> > WHERE t0.parent_id = t1.id AND (t1.parent_id = ?) [bind: 1]
    > >>
    > >> is a short form for
    > >>
    > >> SELECT t0.description, t0.id, t0.parent_id
    > >> FROM dbo.IMV_locations t0, dbo.IMV_locations t1, dbo.IMV_locations t2
    > >> WHERE t0.parent_id = t1.id AND t1.parent_id = t2.id AND t2.id = ?
    > >> [bind: 1]
    > >>
    > >> (see an extra join)... If you need direct children, then you need to
    > >> remove the last component in the obj-relationship path. The resulting
    > >> mapping should look like this:
    > >>
    > >>
    > >> <obj-relationship name="children" source="Location" target="Location"
    > >> deleteRule="Cascade"
    > >> db-relationship-path="rel_children"/>
    > >>
    > >> <obj-relationship name="parent" source="Location" target="Location"
    > >> db-relationship-path="rel_parent"/>
    > >>
    > >> I hope I understood your requirements correctly...
    > >>
    > >> Andrus
    > >>
    > >>
    > >
    > >
    > > --
    > > Cell : 403.461.7895
    > > Work: 403.770.1534
    > > MSN: fbala..otmail.com
    >
    >

    -- 
    Cell  : 403.461.7895
    Work: 403.770.1534
    MSN:  fbala..otmail.com
    



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