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From Pavel Pereslegin <xxt...@gmail.com>
Subject Re: IgniteSet implementation: changes required
Date Mon, 19 Feb 2018 07:44:42 GMT
Hello Vladimir,

> What we can do is to optionally disable on-heap caching for specific set at the cost
of lower performance if user wants so.

I want to make sure that we are speaking about the same thing. By
"on-heap caching" I mean custom datastructure and not standard on-heap
cache, we can't disable it now, because it is the part of current
IgniteSet implementation. Is it acceptable to use GridOffHeapMap
optionally instead of ConcurrentHashMap for "off-heap mode"?


2018-02-15 23:20 GMT+03:00 Dmitriy Setrakyan <dsetrakyan@apache.org>:
> On Thu, Feb 15, 2018 at 6:08 AM, Vladimir Ozerov <vozerov@gridgain.com>
> wrote:
>
>> I do not think indexes is the right approach - set do not have indexes, and
>> you will have to maintain additional counter for it in order to know when
>> to stop.
>>
>> From what I see there are two distinct problems:
>> 1) Broken recovery - this is just a bug which needs to be fixed. As soon as
>> data is stored in real persistent cache, recovery of data structure state
>> should be trivial task.
>> 2) Heap items - this should not be a problem in common case when set
>> contains moderate number of elements. If set is excessively large, then
>> this is not the right structure for your use case and you should use
>> standard IgniteCache API instead. What we can do is to optionally disable
>> on-heap caching for specific set at the cost of lower performance if user
>> wants so.
>>
>
> Vladimir, I am not sure I agree. In my view, set should be similar to
> cache, just a different API. I am not sure why we should make an
> assumptions that set data should be smaller than cache, especially given
> that it is a trivial task to implement a set based on Ignite cache API (we
> could just store key-key mappings in cache instead of key-value mappings
> internally).
>
> Can you clarify why you believe that IgniteSet should need to have on-heap
> entries?
>
> D.

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