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Home » Modeling » EMF » Persisting chained objects in CDO(MongoDB store)(Chained Objects, CDO and MongoDB)
Persisting chained objects in CDO(MongoDB store) [message #1704174] Fri, 07 August 2015 21:50 Go to next message
Fábio Silva is currently offline Fábio SilvaFriend
Messages: 18
Registered: December 2014
Junior Member
I am trying to persist a large emf model using CDO and mongoDB. As usual, it throws an exception saying the collection is too large. Then I tried to persist in chunks, but the references were lost.
Ex: My model has a commit -> change -> changeRegion relashionship

It didn't work when I tried to persist the "commit" object, so I tried to persist changeRegion upfront. But the references of "change" get lost. Actually the transaction model is a bit strange. If I do the same operation, but in a smaller transction section, it persists in separate collections, whereas larger transaction sections leads to bigger, concentrated objects.

What's the proper way to work?
Re: Persisting chained objects in CDO(MongoDB store) [message #1705226 is a reply to message #1704174] Thu, 13 August 2015 06:03 Go to previous message
Eike Stepper is currently offline Eike StepperFriend
Messages: 6446
Registered: July 2009
Senior Member
Hi Fábio,

Please note that we don't actively maintain the MongoDBStore due to the lack of resources. More comments below...

Cheers
/Eike

----
http://www.esc-net.de
http://thegordian.blogspot.com
http://twitter.com/eikestepper


Am 07.08.2015 um 23:50 schrieb Fábio Silva:
> I am trying to persist a large emf model using CDO and mongoDB. As usual, it throws an exception saying the collection
> is too large.
Not that the document in the collection is too large?

> Then I tried to persist in chunks, but the references were lost. Ex: My model has a commit -> change -> changeRegion
> relashionship
That might be a bug in the MongoDBStore. IIRC the logic in there is not too complicated, so you may want to use the
debugger to investigate your problem further.

> It didn't work when I tried to persist the "commit" object, so I tried to persist changeRegion upfront. But the
> references of "change" get lost. Actually the transaction model is a bit strange. If I do the same operation, but in a
> smaller transction section, it persists in separate collections, whereas larger transaction sections leads to bigger,
> concentrated objects.
I don't understand what you mean. Perhaps it helps to be more concrete and describe the problem with an example.

Because MongoDB itself does not support proper ACID transactions across multiple documents/collections like common SQL
databases the MongoDBStore persists each CDO commit atomically in a single document. The drawback is that read access is
implemented as queries over multiple commit documents.


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