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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 22:49:50 -0400

Hey John,

Oh, yes, I checked every aspect of every database column and constraint, and of every model attribute and relationship *very* painstakingly. I was even comparing the entities' .plist files in text mode.

I would think single-table mapping would be the better choice if performance is the driving concern... no? I would think the benefit of vertical mapping would be clarity of expression of the design (that is, implementation look a lot like conceptual design); and for horizontal mapping.

I chose single-table mapping for B because for the most part, it's merely a correlation table with a couple of extra attributes, mostly shared by all subclasses. There are a couple of exceptions, but they are just that: exceptions - not the general rule.

I tend to agree with you, though, that this is getting to be a complicated mess, and probably not worth the effort. But it would be kinda cool if I could get it to work. :)

- Patrick



On Aug 3, 2006, at 7:55 PM, John Larson wrote:

Patrick,

Not to seem too obvious, but did you check the relationship in your C subclass. I spent two days troubleshooting a bunch of subclassing just to find out I forgot to uncheck the Abstract box in the subclasses. I'm just about over the hangover now, but I now *always* check EOModeler.

IMHO, however, I would evaluate your decision to use such a scheme. In the time you spend troubleshooting this you may be able to implement true horizontal or vertical inheritance and get better performance.

John

On Aug 3, 2006, at 4:05 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? :-)

--
Patrick Robinson
AHNR Info Technology, Virginia Tech
email@hidden



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References: 
 >strange EO inheritance issue (From: Patrick Robinson <email@hidden>)
 >Re: strange EO inheritance issue (From: John Larson <email@hidden>)

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