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From Adam Fuchs <afu...@apache.org>
Subject Re: Keys with identical timestamps
Date Mon, 09 Feb 2015 21:04:29 GMT
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.

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.

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