On 11/01/10 1:05 AM, George Stan wrote:
Hi,
Is it possible to map fake foreign keys with CM?
In many DBs for webapps there seem to be quite a few tables (for entities like
Tags, Comments, Attachments, Events) to have relationships to many other
tables, and instead of a FK, a combination of two fields is used
(target_table_name and target_row_id).
I know that other ORMs (like ActiveRecord from RoR) have this feature, but I'm
not sure about Cayenne.
Hi George,
There is another option which I should have pointed out. Say you have an Attachments
table. And an AttachmentsRelation table which is the many many join. Then make
AttachmentsRelation a "single table inheritance" entity with children:
AttachmentsRelation_Contact
AttachmentsRelation_Room
AttachmentsRelation_Building
AttachmentsRelation_Painting
Then each of these children is mapped with a join in Cayenne modeler to the appropriate Contact,
Room, etc entities. There will be a qualifier in the single table inheritance setup which will be
something like "contact", "room", etc as needed.
That really should do everything you wanted.
Cheers
Ari
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Aristedes Maniatis
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