Re: First time inheritance attempt

From: Dave Lamy (davelam..mail.com)
Date: Thu Sep 24 2009 - 14:20:39 EDT

  • Next message: Michael Gentry: "Re: First time inheritance attempt"

    Crap. OK. Nothing like an occasional reminder of what happens when you
    assume things.

    Thanks for the tip Michael-- I'll just use another method for now.

    Dave

    On Thu, Sep 24, 2009 at 1:18 PM, Michael Gentry <mgentr..asslight.net>wrote:

    > I believe single-table and horizontal have been implemented, but I
    > don't think vertical has been implemented yet. There is still an open
    > ticket for vertical inheritance:
    >
    > https://issues.apache.org/jira/browse/CAY-1090
    >
    >
    > On Thu, Sep 24, 2009 at 1:59 PM, Dave Lamy <davelam..mail.com> wrote:
    > > 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 <mgentr..asslight.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 <davelam..mail.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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