[Glass] Concurrency Pattern - Delete an object if a collction it contains is empty, how ?

[Ralph Mauersberger]

Hello Marten,

a simple but effective strategy could be to include something like 
theEmptySet add: #deleted in transaction A. This would conflict with a 
potential addition made by transaction B. As far as I understand your 
use case, the Set-Entry #deleted (or whatever) won't be a problem if no 
conflict occures, since the object with the Set will be GCed in that case.

Br,

Ralph


Am 27.02.2019 um 16:54 schrieb Marten Feldtmann via Glass:
>
> I do not want to remove an empty set from an object, perhaps this 
> makes it much clearer:
>
>
> Transaction A:
>
> +-------------------> check if set in object attribute slot is empty  
> -> remove object -> ------------------------------------+
>
> Transaction B:
>
>                + -----------------> add element to set in object 
> attribute slot -> ------------ +
>
>
> I would not assume, that this results into a commit conflict ....
>
>
>> James Foster <Smalltalk at JGFoster.net> hat am 27. Februar 2019 um 
>> 15:59 geschrieben:
>>
>> In order to better understand the situation, I have two questions:
>> (1) Why do you want to remove an empty Set from an object?
>> (2) Why not use locks?
>>
>> James
>>
>>> On Feb 27, 2019, at 4:16 AM, Marten Feldtmann via Glass < 
>>> glass at lists.gemtalksystems.com 
>>> <mailto:glass at lists.gemtalksystems.com>> wrote:
>>>
>>> This seems to be a general concurrency handling pattern in Gemstone:
>>>
>>>
>>> Situation: I have an object, which holds a Set in one of its 
>>> attributes (slots).
>>>
>>> Question: I want to remove this object, IF the set is empty. But 
>>> what happens, if another task is just adding an item to this set ? 
>>> How can Gemstone find a commit conflict ? I do not want to use locks 
>>> on objects.
>>>
>>>
>>> Any other idea ?
>>>
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>>
>
>
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