Re: Mapping multiple EOs to one table
Re: Mapping multiple EOs to one table
- Subject: Re: Mapping multiple EOs to one table
- From: Ricardo Strausz <email@hidden>
- Date: Mon, 18 Aug 2003 16:33:02 -0500
On lunes, agos 18, 2003, at 16:10 America/Mexico_City, Jonathan
Rochkind wrote:
I'm doubtful that single table inheritance will work for you. The EOF
inheritance scheme assumes that each row represents a certain class,
and doesn't change back and forth. You have rows that really are all
classes at once, it's not that certain rows are certain classes. It's
that they're all at once, but you just don't want to fetch all the
data in at once. I don't think you are going to be able to use EOF
inheritance in a way that achieves your goals (doesn't fetch in all
columns at once), but doesn't cause any problems. That's too far from
what it's intended for, I think.
I do not undestud your concern...
Say I have a table with four columns: PK, date, anInt & aFloat
and I want to see it in two different scenarios: in the first only PK,
date & anInt, and in the second PK, date & aFloat.
I can make a parent entity with PK & date and two childs (each with the
extra column added as an atribute), all mapped to the same table...
I think that the only thing to be cocerned here is to alow those extra
atributes to be NULL in the database...
Dino
But I haven't been able to think of a better solution either. You
might be best off just moving your data to a number of different
tables, instead of having them all in one table.
With your previous design, having multiple EOEntities that are really
the same table, you could try something like: Designate of your
entities as the 'primary' one. Only this one will ever be inserted.
It has relationships to the other entities, that are really
relationships to other 'parts' of the same row the source EO
represents. Follow these relationships to get these other parts;
don't ever insert EOs of these other entities. Still not sure that
will work. Monkeying around with the 'propagate primary key' and
'mandatory' and 'owns destination' attributes on the relationships
from this 'main' entity to the other ones might get you somewhere too.
But I'm not too optimistic about it myself.
--Jonathan
At 08:23 AM 8/19/2003 +1200, Ray Ackland wrote:
Well, even though many of the tables will only be sharing one common
field (primary key) I guess what we are looking at is really single
table inheritance. This could be the way to go. Seems to meet all the
criteria - the parent class is just the primary key field.
I will definitely try it and tell you what happens. That gives me
much more optimism.
Ray.
On Tuesday, Aug 19, 2003, at 06:08 Pacific/Auckland, Ricardo Strausz
wrote:
Just guessing...
but first, does you multiple views of the same table inherits from
one the other?
It may be that, if you want to have different views from the same
table, define different childs for it (and not simply unrelated
entities which may confuse EOM).
Hope it helps! let us know
Dino
_______________________________________________
webobjects-dev mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/webobjects-dev
Do not post admin requests to the list. They will be ignored.
_______________________________________________
webobjects-dev mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/webobjects-dev
Do not post admin requests to the list. They will be ignored.
_______________________________________________
webobjects-dev mailing list | email@hidden
Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/webobjects-dev
Do not post admin requests to the list. They will be ignored.