[hibernate-dev] [OGM] Mapping associations in MongoDB

[Guillaume SCHEIBEL]

At the very beginning, I thought to manage association like this:

   - Case of @OneTo* associations could be managed like embeddeds (for me
   it makes sens and close to the mongo way)
   - Case of @ManyTo* associations could be managed in a usual way
   (association collections, etc.)

Of course, at the end, we should provide a configuration system like an
@InsideAssociation to explicitly  say "I want to store this association
inside the "master" one" no ?
And regarding the documentation
http://www.mongodb.org/display/DOCS/Database+References#DatabaseReferences-DBRef
it could be an idea :)

what do you think ?

Guillaume

2012/4/25 Emmanuel Bernard <emmanuel at hibernate.org>

> ## Mapping strategy
>
> I think we have explored three main options while implementing the
> association mapping in MongoDB
>
> 1. Put the assoc info within the entity document we navigate from
> 2. Put the assoc info in a dedicated document and dedicated collection
> 3. Put the assoc info in n documents (one doc per row) and a dedicated
> collection
>
> And slightly orthogonal to this, we have considered to use a prefix for
> the association collection to make sure it does not clash when mapping
> @ManyToOne @JoinColumn.
>
> I am reading MongoDB in Action and it seems option 1 is the most natural
> for MongoDB. At least let's offer the option via a property collected by
> the datastore / dialect. We can decide to reduce options down the road we
> we have a better grasp. And that will prevent rewriting the dialect every
> tie someone changes his mind (like me ;P)
>
> ## Optimizing what is store
>
> We definitely store the same data over and over (like the table in
> association rows. At some point we probably will want to clean that up to
> do a more "natural" mapping.
>
> (More) thoughts on associations?
>
> Emmanuel
>
> PS: this is nothing new but I'd rather capture this info by mail rather
> than via IRC discussions to consolidate it.
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