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From Billie Rinaldi <billie.rina...@gmail.com>
Subject Re: Keys with identical timestamps
Date Mon, 09 Feb 2015 21:37:27 GMT
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.
>

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