Since all the Entities have integer primary keys, there is no way to discriminate between what entity owns what a row in table D because it could be any one of the first three. The join table is a requirement otherwise there needs to be an attribute added to the table which contains D to tell AR (or any SQL query) which of the three entities owns that row, similar to what the Any attribute does.
On Jun 5, 1:03 pm, Thi <[email protected]> wrote: > From a design standpoint, I wonder which would be the best solution, > having a join table or simply letting FKs add up as columns on the D > table. Join tables sounds more elegant, a single table sounds way > easier to implement/maintain, hm. > > On Jun 4, 11:12 am, Jason Sznol <[email protected]> wrote: > > > I don't want to start a new topic regarding this but I was able to fix > > my problem. By putting a HasAndBelongsToMany Attribute on my three > > entities owning the last entity, I was able to force ActiveRecord and > > hbm2ddl to use a join table so the schema looks like this > > (ParentEntityTable x ParentChildEntityJoinTable x ChildEntityTable). > > This solved my issue completely; however, I was reading some use cases > > where if you put a Unique attribute on the many-to-many relationship > > you force it to become a one-to-many relationship with a join table. I > > do not see the unique attribute on the HasAndBelongsToMany attribute > > and I cannot think of any other way to get ActiveRecord to create this > > schema. Any ideas if this will be implemented or how to do it? > > > On May 27, 4:22 pm, Markus Zywitza <[email protected]> wrote: > > > > It might work with an explicit Any-Property in D. You must never > > > forget that even unidirectional relations are relations. And on the > > > database, one-to-many relations are implemented with FKs on the > > > one-side, regardless of whether AR hides that from the model or not. > > > > -Markus > > > > 2009/5/27 Hexedit <[email protected]>: > > > > > I apologize I worded my first message improperly. D should have no > > > > knowledge > > > > of the Entities A, B or C. In my object there is no Property for > > > > linking back to > > > > any one of the other entities. So it is a one sidedHasManywith no > > > > related BelongsTo. > > > > I suppose an Any tag would work well in this situation but I'm not > > > > sure how to configure > > > > it or if it even works with aHasManyon the other side of the > > > > relation. Assuming that > > > > my domains A, B, and C never have conflicting integer primary keys, > > > > this shouldn't be > > > > an issue correct? > > > > > On May 27, 10:56 am, Markus Zywitza <[email protected]> wrote: > > > >> You have A, B and C pointing to D: Ergo, D has an implicit many-to-one > > > >> to A, B and C, which is hidden in AR due to the unidirectional > > > >> relation. Now you want that D only has one many-to-one connection, > > > >> which will direct to A, B or C. This seems impossible: How should AR > > > >> know from an integer to which of the classes A, B or C it belongs? If > > > >> you use Identity, the same key might be used in A, B and C, leaving AR > > > >> clueless of what to load. > > > > >> You need three FK columns in D if A, B and C are not related. If they > > > >> belong to the same base class, you can define theHasManythere, but > > > >> with unrelated classes your scenario is impossible. > > > > >> -Markus > > > > >> 2009/5/27 Hexedit <[email protected]>: > > > > >> > I have three unique entity classes that each have a collection of a > > > >> > fourth entity via theHasManyattribute. The mappings should be one-to- > > > >> > many unidirectional relationships from entities A, B, and C to entity > > > >> > D. EachHasManyattribute references the same table and the same > > > >> > column for the foreign key. Since the referenced column is an integer > > > >> > it should not matter that it could be pointing to objects from 3 > > > >> > tables. The problem is that the generation tool non-deterministically > > > >> > picks one of the first three entities and creates a foreign key > > > >> > relationship from the reference column in the 4th entity table to the > > > >> > entity that owns that relation. Is there any way for me to override > > > >> > this behavior and make it so that the Many side of theHasMany > > > >> > relationship doesn't foreign key back to the first table? --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Castle Project Users" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/castle-project-users?hl=en -~----------~----~----~----~------~----~------~--~---
