Newbie just getting started with V4RB: Is-a relationships

[Ruslan Zasukhin]

on 2/28/03 9:22 PM, Stefano Franchi at s.franchi at auckland.ac.nz wrote:

Hi Stefano,

> I am just getting started with Valentina for RealBasic, and I need to
> clarify a couple of issues about hierarchical relationships in
> Valentina before I get started with database design.
> 
> Say I have an object "Book"  with all the usual fields. It is a
> subclass of VBaseObject. If I need to specialize Book into
> "ManuscriptBook" (for example) can I subclass it and inherit all the
> properties of Book? This is what some Object-relational RDMS  like
> PostgreSQL allow.   But I'm not clear if Valentina allows it as well.

Right now no, but we definitely will,
And in the way little different from Postgre.

> If it isn't possible, how do people normally implement Is-a
> relationships like this one in Valentina? Two standard approaches come
> to mind:

> a.  With manually maintained 1-1 relationships between child and parent
> tables? Or

Yes!

And use ObjectPtr field in the child table for this,
Make it unique, to get 1 : 1

> b. with so-called "horizontal" design (i.e. by having only children and
> replicating all the parent's fields in each table)?

NO!  bad idea.

> I very much prefer the first approach, but it usually takes quite a
> significant performance hit in traditional RDBMS, because of all the
> joins needed to reconstruct the complete entity. Design is cleaner,
> though, and easier to maintain. Is Valentina's famed speed a good
> reason to dismiss the performance hit? Does it even suffer from it (I
> have no idea, yet I hope, of how different Valentina is from a RDBMS
> internally)?

Yes, ObjectPtr field is SPECIALLY designed to support this -- INHERITANCE.
I self will use it for inheritance in future versions.

In fact ObjectPtr field is 4 times faster of RDB links,
And JOINS in Valentina will be much faster of RDBMS.

And wait the moment. I think Postgre also simply relate 2 tables...
Although do not remember. IF they go by second way then this is really bad
way.

-- 
Best regards,
Ruslan Zasukhin      [ I feel the need...the need for speed ]
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e-mail: ruslan at paradigmasoft.com
web: http://www.paradigmasoft.com

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