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Re: strange EO inheritance issue
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Re: strange EO inheritance issue


  • Subject: Re: strange EO inheritance issue
  • From: Patrick Robinson <email@hidden>
  • Date: Thu, 03 Aug 2006 22:39:10 -0400

On Aug 3, 2006, at 5:24 PM, Sacha Michel Mallais wrote:
On Aug 3, 2006, at 2:05 PM, Patrick Robinson wrote:

I've got a rather strange EO inheritance question. I've got a situation where I've set up single-table inheritance (with a
subclass "type" column) for 7 out of 8 of my subclasses; and a separate table (with the same "type" column) that has a bunch more columns for the 8th, just because I didn't want all those columns sitting there empty for most of the rows (i.e. for the other 7 subclasses). Probably false economy, but be that as it may....


My structure looks like this:

A <-->> B <<--> C

C is modeled as an inheritance hierarchy using horizontal mapping, and B is modeled as the inheritance hierarchy described above, using mostly single-table mapping. There is a different subclass of B for each corresponding subclass of C.

It all built just fine, but when it came time to save an object of my new C subclass (the one that corresponds to the B subclass with its own table), the primary key of the C subclass object did not propagate to the B subclass object -- it was left as null. This is done with Oracle, so there's an Oracle sequence C_SEQ that's used to obtain C's primary key, and C_ID is the primary key of all C subclasses. Normally, this propagates to the B subclass objects just fine (with all the other B subclasses, that is), but it isn't working with the B subclass that is set in EOModeler to use its own table.

Has anyone else tried to do this kind of thing, or am I just trying to do something idiotic? :-)

Hi Patrick,

I've recently tried a similar thing to no success. It appears that there is a WO bug WRT propagating PKs to tables that are not correlation tables (a correlation table is a table mapping two entities in a many-to-many relationship with no other attributes -- if B had attributes B.aPK and B.cPK, and no others, it would be a correlation table). What I did was to throw out propagation and instead use a standard integer PK.

Hey Sacha,

Before I started trying to mix single-table and horizonal mapping in a single inheritance hierarchy, I actually had this all working. B was a correlation table with some additional attributes. That is, its PK was composed of B.aPK and B.cPK, but it also had cType (which let me subclass B into various subclass correlation tables via single- table mapping), and some things like sortOrder (to let the user specify a particular order for the C objects), myComments, etc.

The propagation of PK from A and C (i.e. its subclasses) to B (i.e. its subclasses) actually worked just fine. The fly got into the ointment when I started mixing inheritance models in a single hierarchy.

--
Patrick Robinson
AHNR-IT, Virginia Tech
email@hidden



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References: 
 >strange EO inheritance issue (From: Patrick Robinson <email@hidden>)
 >Re: strange EO inheritance issue (From: Sacha Michel Mallais <email@hidden>)

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