Object identity

[Florian Minjat]

Hi Chris,
I read the ReadStrategy FAQ and it's quite interresting. I have some 
question though.
First of all, how long will the read strategy last for a given session 
by doing mySession 'session readStrategy: myReadStrategy.' ? Do I have 
to revert it back to a default strategy after my specific queries ?
Then is it possible to be more specific. For example : my Players have 
a reference to a Dungeon which references a Desk which has two 
OrderedCollection referencing Letters. If I want to send a Letter to 
10 Players, I need to had a Letter in each of their Desk, resulting of 
a huge query I think. Is there a way to be so much specific with a 
ReadStrategy ?
By doing such a query, my understanding is that the other referenced 
objects of the Dungeons won't be materialized. Am I right ?

Florian

Florian Minjat wrote:
> Great ! I knew there were already something like that in Magma.
> I will test it soon. It should speed up the listing of the players 
> considerably.
> Thanks !
> 
> Florian
> 
> Chris Muller wrote:
>> Yes, I think you are asking about ReadStrategy's.  They are crucial to
>> getting proper performance out of Magma.  Here is the information
>> about ReadStrategy's you must understand:
>>
>>  http://wiki.squeak.org/squeak/2638
>>
>>
>> On 6/12/07, Florian Minjat <florian.minjat at emn.fr> wrote:
>>> I have another question : if I ask magma for an object Player which
>>> references others Players in its Letters, will magma deserialize all
>>> the referenced players ?
>>> If it is the case, is there a way to ask for an 'half-deserialization'
>>> ? By that I mean for example getting the referenced Players with all
>>> their primitive objects but no referenced object ? Otherwise I will
>>> need to seriously rethink the Mailbox/Letter model of my application.
>>>
>>> Florian
>>>
>>>
>>> Chris Muller wrote:
>>> > Hi Florian, this is an interesting problem.
>>> >
>>> > First to answer your question, Magma identifies an object as already
>>> > in the repository if it has a "permanent" oid.  This is an oid range
>>> > between MaOidCalculator #firstUserObjectOid and #lastUserObjectOid.
>>> > The #hash of an object never comes into play to determine this, or
>>> > anything in Magma for that matter.
>>> >
>>> > One way to get your large object-model into Magma would be to change
>>> > the method MaObjectBuffer>>#ensureSpaceFor: to allow more than 10
>>> > megabyte serializations.  I only suggest this only because it is an
>>> > arbitrary limit and it looks like your model is right there just over
>>> > the limit.  Change it to 50-meg on the fastest computer you have, It
>>> > should work.  Submit the commit and let it run all night.
>>> >
>>> > Another option would be to temporarily change your Players to
>>> > reference the other players only logically; by some temporary id or
>>> > something.  Once you get them loaded into Magma, then reset the
>>> > references back to the actual objects.
>>> >
>>> > Note #maTransientVariables is available to implement on Player so it
>>> > will not serialize those variables, so you could actually ADD a new
>>> > logical reference, if necessary, and make the hard player reference
>>> > transient (temporarily).
>>> >
>>> > Please let me know if these ideas are feasible.
>>> >
>>> > - Chris
>>> >
>>> >
>>> > On 6/10/07, Florian Minjat <florian.minjat at emn.fr> wrote:
>>> >> Hi,
>>> >>    I am trying to transfer a big object hierarchy to Magma : 110100
>>> >> objects in 9004144 bytes.
>>> >>    The basic structure is composed of ~70 Players with a lot of stuff
>>> >> inside. Each players can have some Letters which references other
>>> >> Players as sender or recipients.
>>> >>    The problem is that I can't submit one player to an empty Magma
>>> >> repository without letting Magma insert all the references Players.
>>> >> And the resulting transaction is too big, causing an error. So I
>>> >> separated all the Letters from the Players, inserted the players
>>> >> (~50min) and then tried to insert the Letters. But I close the
>>> >> connection to the magma repository between the two, so Magma tried
>>> >> again to load all the references Players.
>>> >>    So here is my question : how does Magma identify a given object as
>>> >> already inside a repository ? Does it compare the hash of the objects
>>> >> and I just need to redefine the hash method of Players ?
>>> >>    Each try is quite long so I would like to understand a little more
>>> >> of the inner mechanisms of Magma instead of trying numerous times.
>>> >>
>>> >> Florian
>>> >> _______________________________________________
>>> >> Magma mailing list
>>> >> Magma at lists.squeakfoundation.org
>>> >> http://lists.squeakfoundation.org/mailman/listinfo/magma
>>> >>
>>> >
>>> _______________________________________________
>>> Magma mailing list
>>> Magma at lists.squeakfoundation.org
>>> http://lists.squeakfoundation.org/mailman/listinfo/magma
>>>
>>
> _______________________________________________
> Magma mailing list
> Magma at lists.squeakfoundation.org
> http://lists.squeakfoundation.org/mailman/listinfo/magma
>