Question Backlog for Valentina mailing list.

[Ruslan Zasukhin]

On 11/16/05 8:45 AM, "Ed Kleban" <Ed at Kleban.com> wrote:

Hi Ed,

>>>> * Valentina 2 also have new link -- BbinaryLink. This is not a field at
>>>> all.
>>>> 
>>>> Methods of Vlink class work for ALL link kinds. So it needs write text in
>>>> general form.
>>>> 
>>> 
>>> Yes. I understand and agree.  First I had to understand what it did.  I
>>> could
>>> write something that would serve all cases now.   I very much like
>>> the concept of the Vlink; making the links be an instantiated abstraction
>>> is very cool.  
>>> --Ed
> 
> Well, I take that back.  I clearly don't understand.  Last night in bed I
> started wondering:

:-)
 
> "I wonder if there's a way to simply use a byte-wide field as you would use
> an ObjectPtr field if it is known in advance that the linked-to table will
> never have more that 255 records? "

YES. Then you get old good FOREIGN KEY. And this still is VLink.
 
> Then I thought, "Hmm. maybe that's what Binary Links can do if you create a
> link between a byte-size field in one table with the virtual RecID field in
> another table."

NO. BinaryLink always use RecID values.

> But I just now read all the doc in both the Kernel and RB Reference about
> Binary Links and decided I don't have a clue about what they do or how to
> use 'em.

They do effectively the same as you do in Relational model with help of
third Table to establish M:M link.

What do this table? It just remember pairs  (id1, id2)

BinaryLink do the same, but use RecIDs and it is NOT a table.
It is more effective structure.

 
> Specifically:  The constructor VBinaryLink takes as arguments a pair of
> tables, and some referece ("power") , deletion, and storage arguments -- but
> has no field arguments.

Right. Because always RecID are used.

ObjectPtr also do not use "field" of pointed table. Remember?
Only Foreign KEY need field.

> So my conjecture that it could relate specific
> fields was clearly wrong, that's not what it does, nor is that what the
> documentation says it does.  In fact as the doc clearly states it doesn't
> require field allocations.

right
 
> So I guess I'm stuck.  I don't understand these critters.  I understand how
> to create a binary link with VBinaryLink(...), but I don't know how to use
> the link once I have it.  How do I tell the link, or how does the link know,
> which records in Table A correspond to which records in Table B, or vice
> versa?

simple:

    link.Add( tblA.RecID, tblBRecID )



-- 
Best regards,

Ruslan Zasukhin
VP Engineering and New Technology
Paradigma Software, Inc

Valentina - Joining Worlds of Information
http://www.paradigmasoft.com

[I feel the need: the need for speed]