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From David Boxenhorn <da...@citypath.com>
Subject Re: Why do Digest Queries return hash instead of timestamp?
Date Wed, 13 Jul 2011 14:31:01 GMT
Is that the actual reason?

This seems like a big inefficiency to me. For those of us who don't worry
about this extreme edge case (that probably will NEVER happen in real life,
for most applications), is there a way to turn this off?

Or am I wrong about this making the operation MUCH more expensive?


On Wed, Jul 13, 2011 at 3:20 PM, Boris Yen <yulinyen@gmail.com> wrote:

> For a specific column, If there are two versions with the same timestamp,
> the value of the column is used to break the tie.
>
> if v1.value().compareTo(v2.value()) < 0, it means that v2 wins.
>
> On Wed, Jul 13, 2011 at 7:13 PM, David Boxenhorn <david@citypath.com>wrote:
>
>> How would you know which data is correct, if they both have the same
>> timestamp?
>>
>> On Wed, Jul 13, 2011 at 12:40 PM, Boris Yen <yulinyen@gmail.com> wrote:
>>
>>> I can only say, "data" does matter, that is why the developers use hash
>>> instead of timestamp. If hash value comes from other node is not a match, a
>>> read repair would perform. so that correct data can be returned.
>>>
>>>
>>> On Wed, Jul 13, 2011 at 5:08 PM, David Boxenhorn <david@citypath.com>wrote:
>>>
>>>> If you have to pieces of data that are different but have the same
>>>> timestamp, how can you resolve consistency?
>>>>
>>>> This is a pathological situation to begin with, why should you waste
>>>> effort to (not) solve it?
>>>>
>>>> On Wed, Jul 13, 2011 at 12:05 PM, Boris Yen <yulinyen@gmail.com> wrote:
>>>>
>>>>> I guess it is because the timestamp does not guarantee data
>>>>> consistency, but hash does.
>>>>>
>>>>> Boris
>>>>>
>>>>>
>>>>> On Wed, Jul 13, 2011 at 4:27 PM, David Boxenhorn <david@citypath.com>wrote:
>>>>>
>>>>>> I just saw this
>>>>>>
>>>>>> http://wiki.apache.org/cassandra/DigestQueries
>>>>>>
>>>>>> and I was wondering why it returns a hash of the data. Wouldn't it
be
>>>>>> better and easier to return the timestamp? You don't really care
what the
>>>>>> data is, you only care whether it is more or less recent than another
piece
>>>>>> of data.
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>

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