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From Dave Lamy <davel...@gmail.com>
Subject Re: First time inheritance attempt
Date Thu, 24 Sep 2009 17:59:59 GMT
Yes, I'm attempting vertical multiple-table inheritance.  I was assuming
functionality based upon this document:

http://cayenne.apache.org/doc/inheritance-overview.html

which had this section:
Vertical (joined) inheritance

This final approach requires one table per subclass plus one table for the
superclass. All attributes found in the superclass are stored in this
additional table. This is particularly useful when you have lots of common
attributes or relations to other entities. Perhaps Person is subclassed by
Student, Teacher, Parent, AdminStaff, Visitor and Applicant. But all these
entities are allowed to borrow books from the library. Now, rather than
creating 6 relationships between each of these tables to the Loan table, you
can create a single relationship between Person and Loan.

Superclass: abstract or concrete
Class designator column: required
Primary key: in superclass. Copied into subclass to form the one-to-one
join.

Perhaps this is not yet implemented?  :-(

Dave


On Thu, Sep 24, 2009 at 12:46 PM, Michael Gentry <mgentry@masslight.net>wrote:

> You are trying to do multiple-table inheritance?
>
> Unless I'm mistaken, I don't believe that has been implemented yet.
> Cayenne can do in-table inheritance using a discriminator column.
>
>
> On Thu, Sep 24, 2009 at 1:10 PM, Dave Lamy <davelamy@gmail.com> wrote:
> > Hey guys--
> >
> > I'm attempting to model some inheritance for the first time and it's not
> > working yet.  Here's my situation:
> >
> > My model is to have a non-abstract parent class->table and then
> > subclass->tables like so:
> >
> > First I should doublecheck to make sure my mapping XML looks OK:
> >
> >    <db-entity name="ASSET_CONTENT">
> >        ...
> >        <db-attribute name="CONTENT_TYPE" type="VARCHAR" length="50"/>
> >        <db-attribute name="ID" type="INTEGER" isPrimaryKey="true"
> > isGenerated="true" isMandatory="true"/>
> >        ...
> >    </db-entity>
> >    <db-entity name="IMAGE_ASSET_CONTENT">
> >        <db-attribute name="HEIGHT" type="INTEGER"/>
> >        <db-attribute name="ID" type="INTEGER" isPrimaryKey="true"
> > isMandatory="true"/>
> >        <db-attribute name="WIDTH" type="INTEGER"/>
> >    </db-entity>
> >    <obj-entity name="AssetContent"
> > className="com.routeto1.asset.filesystem.AssetContent"
> > lock-type="optimistic" dbEntityName="ASSET_CONTENT"
> > superClassName="com.routeto1.data.impl.DynamicDataObject">
> >        <obj-attribute name="contentType" type="java.lang.String"
> > db-attribute-path="CONTENT_TYPE"/>
> >         ...
> >        <pre-persist method-name="prePersist"/>
> >    </obj-entity>
> >    <obj-entity name="ImageAssetContent" superEntityName="AssetContent"
> > className="com.routeto1.asset.filesystem.ImageAssetContent"
> > lock-type="optimistic" dbEntityName="IMAGE_ASSET_CONTENT">
> >        <qualifier><![CDATA[contentType = "IMAGE"]]></qualifier>
> >        <obj-attribute name="height" type="java.lang.Integer"
> > db-attribute-path="HEIGHT"/>
> >        <obj-attribute name="width" type="java.lang.Integer"
> > db-attribute-path="WIDTH"/>
> >    </obj-entity>
> >
> > Not sure if I need to provide you any more than that.  Cayenne accepts
> the
> > config fine, but when I create a new ImageAssetContent and save it,
> Cayenne
> > only saves to the IMAGE_ASSET_CONTENT  table:
> >
> > 2009-09-24 10:30:53,602 INFO [org.apache.cayenne.access.QueryLogger] -
> > <INSERT INTO IMAGE_ASSET_CONTENT (HEIGHT, ID, WIDTH) VALUES (?, ?, ?)>
> > 2009-09-24 10:30:53,656 INFO [org.apache.cayenne.access.QueryLogger] -
> > <[batch bind: 1->HEIGHT:440, 2->ID:220, 3->WIDTH:495]>
> >
> > I've confirmed that there is data in the object that should be getting
> saved
> > to the ASSET_CONTENT table but is not.
> >
> > What's also interesting is that it is pulling an auto PK value (this is
> > running on a Derby DB for testing):
> >
> > 2009-09-24 10:30:53,258 INFO [org.apache.cayenne.access.QueryLogger] -
> > <SELECT NEXT_ID FROM AUTO_PK_SUPPORT WHERE TABLE_NAME = ? FOR UPDATE
> [bind:
> > 1:'IMAGE_ASSET_CONTENT']>
> >
> > Not so interesting that it's pulling one, but for IMAGE_ASSET_CONTENT?
> I'd
> > assume it would be pulling for ASSET_CONTENT and reusing that ID in both
> the
> > parent and child tables.
> >
> > Am I missing something really basic?
> >
> > I've tested this on 3.0 M5 and M6 with same results.
> >
> > Dave
> >
>

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