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From David Boxenhorn <da...@citypath.com>
Subject Re: deleted counters keeps their value?
Date Wed, 21 Sep 2011 12:44:25 GMT
The reason why counters work is that addition is commutative, i.e.

x + y = y + x

but deletes are not commutative, i.e.

x + delete ≠ delete + x

so the result depends on the order in which the messages arrive.


2011/9/21 Radim Kolar <hsn@sendmail.cz>

> Dne 21.9.2011 12:07, aaron morton napsal(a):
>
>  see technical limitations for deleting counters http://wiki.apache.org/**
>> cassandra/Counters <http://wiki.apache.org/cassandra/Counters>
>>
> For instance, if you issue very quickly the sequence "increment, remove,
> increment" it is possible for the removal to be lost (if for some reason the
> remove happens to be the last received messages).
>
> But i do not remove then very quickly. it does that even with 60 seconds
> between delete and increment. I do not understand what means: "remove
> happens to be the last received messages".
>

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