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From Dia Kharrat <dkhar...@gmail.com>
Subject Re: How are version conflicts handled in HBase?
Date Fri, 05 Jun 2015 15:50:28 GMT
Ted: Yes, I've already read the HBase documentation, but didn't find
anything that directly answered my question. My question was simply whether
it's possible to get cells with the same timestamp with concurrent Puts to
the same cell.

Vlad: Thanks for the information. Yep, I've also noticed the behavior of
the last-write-wins when testing directly in hbase shell and writing out
two values to the same cell with an identical timestamp.

So, I gather that an application writing to the same cell concurrently will
result in potential data loss when the write is at the exact same
millisecond, correct? For my use-case, I'm not necessarily looking for
uniqueness for the timestamp, but want to ensure I can still access all
versions of the cell, even ones with the same timestamp.

Dia

On Thu, Jun 4, 2015 at 7:05 PM, Vladimir Rodionov <vladrodionov@gmail.com>
wrote:

> >> Please read http://hbase.apache.org/book.html#_store
>
> How does this answer original question?
>
> -Vlad
>
> On Thu, Jun 4, 2015 at 6:30 PM, Ted Yu <yuzhihong@gmail.com> wrote:
>
> > Dia:
> > Please read http://hbase.apache.org/book.html#_store
> >
> > Cheers
> >
> > On Thu, Jun 4, 2015 at 6:02 PM, Vladimir Rodionov <
> vladrodionov@gmail.com>
> > wrote:
> >
> > > Yes, last write wins (with higher sequenceId). MemStore will resolve
> this
> > > conflict and only the last
> > > put will be added eventually, unless ... between these two puts
> > MemStore's
> > > snapshot is created.
> > > I this case put #1 will be saved in  a snapshot and eventually will
> make
> > it
> > > into a store file, but this is just my speculations.
> > >
> > > -Vlad
> > >
> > > On Thu, Jun 4, 2015 at 5:08 PM, Dia Kharrat <dkharrat@gmail.com>
> wrote:
> > >
> > > > I'm trying to confirm the behavior of HBase when there are concurrent
> > > > writes to the same cell that happen at the exact same millisecond and
> > not
> > > > providing a timestamp value to the Put operations (i.e. relying on
> > > current
> > > > time of region server). Is it possible that such concurrent writes
> > result
> > > > in a cell with an identical version value or does HBase have a
> > mechanism
> > > to
> > > > protect against that?
> > > >
> > > > If that's the case, my understanding is that last write wins,
> correct?
> > > >
> > > > Thanks,
> > > > Dia
> > > >
> > >
> >
>

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