accumulo-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Dave Hardcastle <hardcastle.d...@gmail.com>
Subject Re: Keys with identical timestamps
Date Mon, 09 Feb 2015 22:12:05 GMT
Adam, Billie,

That's what I thought - thanks for confirming, and for the quick response.

Dave.

On 9 February 2015 at 21:37, Billie Rinaldi <billie.rinaldi@gmail.com>
wrote:

> On Mon, Feb 9, 2015 at 1:04 PM, Adam Fuchs <afuchs@apache.org> wrote:
>
>> Hi Dave,
>>
>> As long as your combiner is associative and commutative both of the
>> values should be represented in the combined result. The
>> non-determinism is really around ordering, which generally doesn't
>> matter for a combiner.
>>
>
> Yes.  However, do not attempt to insert identical keys in a single
> mutation.  Only one will be kept, whether versioning is enabled or not.
>
> Billie
>
>
>>
>> Adam
>>
>> On Mon, Feb 9, 2015 at 3:49 PM, Dave Hardcastle
>> <hardcastle.dave@gmail.com> wrote:
>> > Hi,
>> >
>> > Could someone clarify whether the following statement from the manual -
>> "If
>> > two inserts are made into Accumulo with the same rowID, column, and
>> > timestamp, then the behavior is non-deterministic" - applies even if the
>> > versioning iterator is off? Is the non-determinism the fact that the
>> order
>> > is undetermined if two identical inserts are made and all versions are
>> kept?
>> >
>> > I have an application where the key corresponds to an object and a time
>> > range, and the value is properties of the object over that time range.
>> The
>> > time range is stored in the column qualifier, but I also put the end of
>> the
>> > time range as the timestamp of the key. I frequently get data late, and
>> so
>> > create a key and insert that, but that key may already exist in the
>> table.
>> > When multiple identical versions get put in, the values are aggregated
>> using
>> > a combiner. This seems to be working fine. But maybe I shouldn't be
>> assuming
>> > that Accumulo won't silently drop one of the two keys?
>> >
>> > Thanks,
>> >
>> > Dave.
>>
>
>

Mime
View raw message