Re: [Modeling-users] one model, multiple database instances

[Sebastien B. <sbi...@us...>]

        Hi,

Delio Brignoli <in...@dr...> wrote:
> Hello,
>=20
> I'm evaluating the use of modeling for our new project(s) and was
> wondering if some of you could give me pointers on how to access
> multiple database instances of the same model in the same
> application. (I understand that each database instance will be
> isolated and don't expect to insert object from an objectStore into
> another) After creating my first model definition and 30 minutes dive
> in the docs, it seems I'll have to create an EC passing a 'properly
> crafted' :-) ObjectStore instance. Am I on the right track?

Without more details, I guess you intend to do some load-balancing between =
db-instances in aread-only app., right?

  First, if you want to do that in different processes, simply change
  the model's connection dictionary before using it; each process will
  then use its own db instance.

Regarding EC(parentObjectStore): it's usually used to make child ECs;
passing it a dedicated ObjectStore is completely untested. But you're on
the right track: you can either give it a dedicated DBContext, or use
the default behaviour (which assigns a ObjectStoreCoordinator) and
design your own ObjStoreCoord. so that e.g. it returns different
DBContexts for different ECs.
  In both cases, you'll have to take care of the DBContext's Database
(see e.g. DBContext.handleNotification): either each one gets its own,
or they all share the same.  If every DBContext gets its own Database
object, then each EC should *always* get the same DBContext, or you'll
defeat the snapshotting ref. counting.

-- S=E9bastien.