Re: PKs With Multitable Inheritance
Re: PKs With Multitable Inheritance
- Subject: Re: PKs With Multitable Inheritance
- From: Ramsey Gurley <email@hidden>
- Date: Wed, 27 Jul 2011 18:02:26 -0700
On Jul 27, 2011, at 5:23 PM, Chuck Hill wrote:
>
> On 2011-07-27, at 5:21 PM, Ted Archibald wrote:
>
>> With a project I'm working on I decided to have a number of my entities inherit from an abstract entity. Each of these entities have their own separate table (I forget what kind of inheritance that's called...).
>
> Horizontal.
More info here:
http://wiki.objectstyle.org/confluence/display/WO/Modeling+Inheritance+with+Entity+Modeler
>> I noticed that EOF is only generating a single series of PKs for the abstract parent entity and not PKs for each child entity. I read somewhere that that's what EOF likes to do with inheritance. But considering I'd never be dealing with the abstract entity, is there a way to make EOF give PKs to each individual entity?
>
> There is probably a way, but it will lead to corrupt data or other problems. EOF needs all the EOs in a hierarchy to have a unique key regardless of entity.
>
>
> Chuck
You could do it in a custom EOAdaptor, but it won't function. OpenBase plugin does this (last time I used it), and as a result, the only inheritance that works on OpenBase is single table.
EOF depends on keys that are unique across all the subclasses, because EOF needs the keys to be unique to create a relationships to the parent entities. Otherwise, what is the FK for a relationship to your parent if both tables have overlapping PKs?
It will sorta work with horizontal until you start making relationships. It would be fundamentally incompatible with vertical because of the way the pk is shared across multiple tables.
Ramsey
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